Influence of different environmental challenges on the expression of reproductive traits in Holstein cattle in Southern Brazil.

The aim of this study was to assess the impact of genotype-environment interaction (GEI) on the manifestation of traits such as age at first calving (AFC), age at first service (AFS), and calving interval (CI) through the application of the reaction norm model in Holstein cattle raised in Paraná state, Brazil. Utilizing data from the milk testing service of the Paraná Association of Holstein Cattle Breeders (APCBRH), this study analyzed records from 179,492 animals undergoing their first, second, and third lactations from the years 2012 to 2022. These animals were part of 513 herds spread across 72 municipalities in Paraná. The environmental gradient was established by normalizing contemporary group solutions, derived from the animal model, with the 305-day-corrected milk yield serving as the dependent variable. Subsequently, reaction norms were determined utilizing a Random Regression Model. Spearman's correlation was then applied to compare the estimates of breeding values across different environmental gradients for the studied traits. The highest EG (+ 4) indicates the least challenging environments, where animals experience better environmental conditions. Conversely, lower EG (-4) values represent the most challenging environments, where animals endure worse conditions. The only trait that exhibited a moderate heritability magnitude was AFC (0.23) in the least challenging environmental condition. The other traits were classified as having low heritability magnitudes regardless of the evaluated environmental gradient. While minimal evidence was found for the influence of GEI on CI, a clear GEI effect was observed for AFC and AFS across all environmental gradients examined. A reversal in genotype ranking occurred under extreme environmental conditions. The findings suggest that the best-performing genotype under one environmental gradient may not necessarily excel under another.

Estimating genetic parameters of reproductive, carcass, and meat quality traits in Polled Nellore cattle.

Considering the economic and commercial efficiency of the beef production chain, the yield and quality of the meat produced must also be included in breeding programs. For the Nellore breed, including the polled herd, these aspects have not been much studied. The aim of this study was to estimate genetic parameters for scrotal circumference adjusted to 365 (SC365) and 450 (SC450) days of age, age at first calving (AFC), accumulated productivity (AP), stayability (STAY), longissimus muscle area (LMA), thickness of subcutaneous fat over the 12th-13th ribs (BF), thickness of subcutaneous fat over the rump (RF), and shear force measured by Warner-Bratzler shear force (WBSF) of polled Nellore cattle. Bayesian analyses were performed by adopting a linear animal model, whereas STAY analyses used the linear threshold model. Heritability estimates were 0.31 (SC365), 0.37 (SC450), 0.16 (AFC), 0.25 (AP), 0.16 (STAY), 0.30 (LMA), 0.13 (BF), 0.24 (RF), and 0.15 (WBSF), indicating moderate response to selection. Genetic and residual correlations between SC365 and SC450 were high (0.91 and 0.74, respectively), as well as the genetic correlations of AP with SC365, SC450, AFC, and STAY (0.61, 0.62, - 0.69, and 0.83, respectively). Genetic and residual correlations of WBSF with reproductive and carcass characteristics exhibited high standard deviations, however favorable. Based on the results, it is expected that in the medium term, animals with greater sexual precocity will also have greater accumulated productivity and longer permanence of females in the herd, along with superior carcass traits. However, due to the low heritabilities and small genetic associations with reproductive traits, fat thickness characteristics (BF and RF) will still require direct selection.

Effect of the percentage of Bos taurus inheritance on the fertility of Holstein×Zebu and Brown Swiss×Zebu cows in the Mexican tropics

Background: No dairy breed or crossbreed has superior overall performance in all environments; therefore, it is necessary to determine which crossbreed is the most suitable for the Mexican tropic and what proportion of European breed is optimum for reproduction. Objective: To assess the effect of the proportion of Bos taurus (Bt) genes on reproductive performance of Holstein×Zebu (HZ) and Brown Swiss×Zebu (BZ) cows, and compare reproductive performance of these genotypes in a dual- purpose production system. Methods: Cows were maintained in a rotational grazing system on African star grass (Cynodon plectostachyus) in Veracruz, Mexico. Cows were milked twice daily. Calves were kept tied to the side of their dams while the cows were milked. Results: The percentage of Bt genes did not affect (p>0.05) fertility traits (age at first calving, days to first service after calving, services per conception, conception rate at first service, days open until conception, gestation length, and calving interval) of BZ cows. In contrast, HZ cows with less than 75% Holstein (H) genes were 0.3 years younger (p<0.05) at first calving and had 39.8 fewer days open (p<0.05) than HZ cows with 75% H genes or more. In addition, the calving interval of HZ cows with less than 75% H genes was 44.8 days shorter (p<0.05) than that of HZ cows with 75% H genes or more. The HZ cows had five fewer days pregnant and were 22.8 kg heavier at calving (p<0.05) than BZ cows. Conclusions: The effect of the percentage of Bt genes on cow fertility depends on the dairy breed used. In general, BZ and HZ cows present similar reproductive performance.

Antecedentes: Ninguna raza lechera o cruce tiene un desempeño general superior en todos los ambientes; por lo tanto, es necesario determinar cuál cruce lechero es más apropiado en el trópico mexicano y qué proporción de raza europea es óptima para la reproducción. Objetivo: Evaluar el efecto de la proporción de genes Bos taurus (Bt) en el desempeño reproductivo de vacas cruzadas Holstein×Cebú (HC) y Pardo Suizo×Cebú (PC), y comparar el desempeño reproductivo de estos dos genotipos en un sistema de producción doble propósito. Métodos: Las vacas se mantuvieron en un sistema de pastoreo rotacional en zacate Estrella de África (Cynodon plectostachyus) en Veracruz, México. Las vacas se ordeñaron dos veces al día. Los becerros se mantuvieron atados, a un costado de sus madres mientras éstas se ordeñaron. Resultados: El porcentaje de genes Bt no afectó (p>0,05) ninguna característica de fertilidad (edad a primer parto, días a primer servicio después del parto, servicios por concepción, tasa de preñez a primer servicio, días abiertos a la concepción, duración de la gestación, e intervalo entre partos) de las vacas PC. En contraste, las vacas HC con menos de 75% de genes Holstein (H) fueron 0,3 años más jóvenes (p<0,05) al primer parto y tuvieron 39,8 días abiertos menos (p<0,05) que las vacas HC con 75% de genes H o más. Además, el intervalo entre partos de las vacas HC con menos de 75% de genes H fue 44,8 días más corto (p<0,05) que el de las vacas HC con 75% de genes H o más. Las vacas HC tuvieron cinco días de gestación menos y fueron 22,8 kg más pesadas al parto (p<0,05) que las PC. Conclusiones: El efecto del porcentaje de genes Bt sobre la fertilidad de la vaca depende de la raza lechera usada. En general, las vacas PC y HC tienen similar desempeño reproductivo.

Antecedentes: Nenhuma raça ou cruza leiteira tem desempenho geral superior em todos os ambientes; portanto, é necessário determinar qual cruza leiteira é mais apropriada no trópico mexicano e qual proporção da raça europeia é ideal para a reprodução das vacas. Objetivo: Avaliar o efeito da proporção de genes Bos taurus (Bt) no desempenho reprodutivo de vacas Holandês×Zebu (HZ) e Pardo Suíço×Zebu (PZ), e comparar o desempenho reprodutivo desses dois genótipos em sistema de produção de dupla aptidão. Métodos: As vacas foram mantidas em sistema de pastoreio rotacional em capim Estrela de África (Cynodon plectostachyus) em Veracruz, México. As vacas foram ordenhadas duas vezes por dia. Os bezerros foram mantidos ao lado de suas mães enquanto eram ordenhadas. Resultados: A porcentagem dos genes Bt não afetou (p>0,05) nenhuma característica de fertilidade (idade ao primeiro parto, número de dias para o primeiro serviço pós-parto, serviços por concepção, taxa de prenhes no primeiro serviço, dias abertos, período de gestação e intervalo entre partos) das vacas PZ. Em contraste, vacas HC com menos de 75% dos genes Holandês (H) eram 0,3 anos mais jovens (p<0,05) no primeiro parto e tiveram 39,8 dias abertos a menos (p<0,05) do que as vacas HZ com 75% ou mais dos genes H. Além disso, o intervalo de parto das vacas HZ com menos de 75% dos genes H foram 44,8 dias mais curtos (p<0,05) do que as vacas HZ com 75% ou mais de genes H. As vacas HZ tiveram cinco dias de gestação a menos e foram 22,8 kg mais pesadas no parto (p<0,05) do que as PZ. Conclusões: O efeito da porcentagem de genes Bt na fertilidade da vaca dependeu da raça leiteira utilizada. Em geral, as vacas PZ e HZ tiveram desempenho reprodutivo semelhante.

Breed and heterosis effects on reproduction and production traits of Girolando cows

The objective of this study was to evaluate the breed and heterosis effects on reproductive traits, test-day milk yield, and 305-day milk yield in different lactations of crossbred Girolando cows. Data consisted of test-day milk yield records of first (118,831 records), second (63,227), and third lactation (44,512) and their relative productive (test-day milk yield, 305-day milk yield, and lactation length) and reproductive (age at first calving, calving interval, days open, and dry period) records of 35,582 Girolando cows from Brazil, collected from 1998 to 2014. The heterosis effect of the evaluated traits in Girolando cattle was estimated by MIXED procedure in SAS. Girolando cows showed a negative (favorable) and significant heterosis effect for reproductive traits. The dry periods between the first and second calving and between the second and third calving showed the greatest gains in heterosis (21.93 and 10.41%, respectively). All the evaluated productive traits showed a significant and similar heterosis effect between the three lactations. The use of crossbreeding strategies between the Holstein and Gyr breeds, instead of using the pure breed, is indeed a good alternative to increase the economic efficiency of the dairy activity in the different production systems in tropical environments.(AU)

Accuracy of genomic breeding values and predictive ability for postweaning liveweight and age at first calving in a Nellore cattle population with missing sire information.

The multiple sire system (MSS) is a common mating scheme in extensive beef production systems. However, MSS does not allow paternity identification and lead to inaccurate genetic predictions. The objective of this study was to investigate the implementation of single-step genomic BLUP (ssGBLUP) in different scenarios of uncertain paternity in the evaluation for 450-day adjusted liveweight (W450) and age at first calving (AFC) in a Nellore cattle population. To estimate the variance components using BLUP and ssGBLUP, the relationship matrix (A) with different proportions of animals with missing sires (MS) (scenarios 0, 25, 50, 75, and 100% of MS) was created. The genotyped animals with MS were randomly chosen, and ten replicates were performed for each scenario and trait. Five groups of animals were evaluated in each scenario: PHE, all animals with phenotypic records in the population; SIR, proven sires; GEN, genotyped animals; YNG, young animals without phenotypes and progeny; and YNGEN, young genotyped animals. The additive genetic variance decreased for both traits as the proportion of MS increased in the population when using the regular REML. When using the ssGBLUP, accuracies ranged from 0.13 to 0.47 for W450 and from 0.10 to 0.25 for AFC. For both traits, the prediction ability of the direct genomic value (DGV) decreased as the percentage of MS increased. These results emphasize that indirect prediction via DGV of young animals is more accurate when the SNP effects are derived from ssGBLUP with a reference population with known sires. The ssGBLUP could be applied in situations of uncertain paternity, especially when selecting young animals. This methodology is shown to be accurate, mainly in scenarios with a high percentage of MS.

Effect of the X chromosome in genomic evaluations of reproductive traits in beef cattle.

The aim of this study was to evaluate whether there are predictive advantages for breeding values with inclusion of X chromosome genomic markers for reproductive (occurrence of early pregnancy - P16 and age at first calving - AFC) and andrological (scrotal circumference -SC) variables in beef cattle. There were 3263 genotypes of females and males evaluated. There were breeding value estimates for SC, AFC and P16 considering two scenarios: 1) only autosomal markers or 2) autosomal and X chromosome markers. To evaluate effects of inclusion of X chromosome markers on selection, responses to selection were compared including or not including genomic marker information from the X chromosome. There were greater heritability estimates for SC (0.40 and 0.31), AFC (0.11 and 0.09) and P16 (0.43 and 0.38) when analyses included, compared with not including, genomic marker information from the X chromosome. When selection is based on results from analyses that did not include information for the X chromosome, there was about a 7 % lesser mean genomic breeding value for the SC traits for selected animals. For P16, there was an approximate 4% lesser breeding value without inclusion of genomic marker information from the X chromosome, while this inclusion did not have as great an effect on the breeding value for AFC. There was an average predictive correlation of 0.79, 0.98 and 0.84 for SC, AFC and P16, respectively. These estimates indicate inclusion of the X chromosome genomic marker information in the analysis can improve prediction of genomic breeding values, especially for SC.

Mapping genomic regions for reproductive traits in beef cattle: Inclusion of the X chromosome.

Although the second largest chromosome of the genome, the X chromosome is usually excluded from genome-wide association studies (GWAS). Considering the presence and importance of genes on this chromosome that are involved in reproduction, the aim of this study was to evaluate the effect of its inclusion in GWAS on reproductive traits (scrotal circumference [SC], early pregnancy [P16] and age at first calving [AFC]) in a Nelore herd. Genotype data from 3,263 animals with the above-mentioned phenotypes were used. The results showed an increase in the variances explained by the autosomal markers for all traits when the X chromosome was not included. For SC, there was an increase of more than 10% for the windows on chromosomes 2 and 6. For P16, the effect was increased by almost 20% for windows on chromosome 5. The same pattern was found for AFC, with an increase of more than 10% for the most important windows. The results indicate that the noninclusion of the X chromosome can overestimate the effects of autosomes on SC, P16 and AFC not only because of the additive effect of the X chromosome itself but also because of its epistatic effect on autosomal genes.

Análisis reproductivo de vacas Suizo Pardo x Cebú y Simmental x Cebú en condiciones tropicales / Reproductive analysis of Brown Swiss x Zebu and Simmental x Zebu cows in tropical conditions

RESUMEN Objetivo. Comparar la fertilidad de vacas cruzadas Suizo Pardo x Cebú y Simmental x Cebú criadas en un ambiente tropical. Materiales y métodos. Se evaluaron características reproductivas de 185 vacas cruzadas Suizo Pardo x Cebú y Simmental x Cebú con diversos porcentajes de raza europea. El pastoreo de las vacas fue rotacional. El ordeño fue dos veces al día con la ayuda (amamantamiento) del becerro, el cual se mantuvo atado cerca de la vaca mientras ella se ordeñaba. Las características se evaluaron ajustando un modelo de mediciones repetidas (excepto para edad a primer parto). Periodo interparto, edad a primer parto, días abiertos, periodo parto-primer servicio y peso al parto fueron analizados con PROC MIXED de SAS. Tasa de gestación a primer servicio y servicios por concepción, se analizaron con PROC GENMOD del mismo programa. Resultados. Las vacas Simmental x Cebú se sirvieron después del parto 39 días antes (p<0.05) y tuvieron 47 días abiertos menos (p<0.05) que las Suizo Pardo x Cebú. El periodo interparto de las vacas Simmental x Cebú fue 45 días más corto (p<0.05) que el de las Suizo Pardo x Cebú. Las vacas Simmental x Cebú pesaron 34 kg más al parto (p<0.05) que las Suizo Pardo x Cebú. Conclusiones. Las vacas Simmental x Cebú tuvieron mejor fertilidad que las Suizo Pardo x Cebú.

ABSTRACT Objective. Compare the fertility of Brown Swiss x Zebu and Simmental x Zebu crossbred cows reared in a tropical environment. Materials and methods. Reproductive traits of 185 Brown Swiss x Zebu and Simmental x Zebu crossbred cows with diverse percentages of European breed were evaluated. Grazing of cows was rotational. The milking was twice daily with the help (suckling) of the calf, which was kept tied next to the dam while she was milked. Traits were evaluated fitting a repeated measures model (except for age at first calving). Calving interval, age at first calving, days open, interval from calving to first service, and weight at calving were analyzed with PROC MIXED of SAS. Pregnancy rate at first service and services per conception were analyzed with PROC GENMOD of the same software. Results. Simmental x Zebu cows started to re-bred 39 days earlier after calving (p<0.05) and had 47 fewer days open (p<0.05) than Brown Swiss x Zebu cows. The calving interval of the Simmental x Zebu cows was 45 days shorter (p<0.05) than that of the Brown Swiss x Zebu cows. Simmental x Zebu cows were 34 kg heavier at calving (p<0.05) than Brown Swiss x Zebu cows. Conclusions. Simmental x Zebu cows had better fertility than Brown Swiss x Zebu cows.

Genetic parameters for milk, growth, and reproductive traits in Guzerá cattle under tropical conditions.

This study aimed to estimate the genetic parameters of milk (305-day milk yield (MY305)), growth (weaning weight (WW), yearling weight (YW), and weight at 550 days (W550)), and reproductive (age at first calving (AFC)) traits in Guzerá cattle by using Bayesian multiple-trait models. Systematic effects included sex and age at calving for the growth and milk traits, respectively. The additive genetic and contemporary groups (herd and year and season of birth) were included as random effects. Additionally, maternal genetic and permanent effects were also included as random effects for the WW. The heritability estimates were 0.29 (MY305), 0.42 (WW), 0.49 (YW), 0.56 (W550), and 0.25 (AFC). The genetic correlations among the growth traits were higher than 0.83; between the MY305 and WW, MY305 and YW, and MY305 and W550, the genetic correlations were 0.25, 0.32, and 0.36, respectively. The AFC was negatively correlated with the milk and growth traits. These results suggest the viability and potential of the joint selection for milk, beef, and reproductive traits in Guzerá cattle.

AMH Polymorphisms and their association with traits indicative of sexual precocity in nelore heifers / Polimorfismos do AMH e suas associações com características indicadoras de precocidade sexual em novilhas nelore

Anti-Müllerian Hormone (AMH) is a protein expressed in the gonads and related to ovarian follicular development. The aim of this study was to investigate the presence of polymorphisms in the AMH gene in a Nelore herd to analyze the genetic constitution of this population and to perform association studies with early pregnancy occurrence (EPO) and age at first calving (AFC). Phenotypic data consisted of verification of early pregnancy and age at first calving of 197 unrelated heifers exposed to the mating season and aged between 15 and 17 months (precocious group) and 24 months (non-precocious group). The “precocious” group consisted of 67 heifers with age at first calving of 26.5 ± 0.59 months, and the “non-precocious” group was composed of 130 heifers with age at first calving of 36.4 ± 0.99 months. All five exons of the AMH gene were amplified by Polymerase Chain Reaction (PCR) and sequenced. A total of three SNPs were identified in this study, all of them located in exon 5 (rs527023314, rs722016629, and rs134387246), the latter one positioned in the stop codon. All three SNPs identified in exon 5 characterized synonymous mutations. Only SNP rs134387246 exhibited a significant value (P ≤ 0.10) for EPO and AFC. The association study of SNP rs134387246 revealed an over-dominance effect (P = 0.056), and no additive effect was observed (P = 0.67). A reduction of 2.5 months (75 days) in the age at first calving of heterozygous heifers for the SNP rs134387246 was observed. For the first time, polymorphisms of the AMH gene were described in Nelore heifers and associated with sexual precocity traits.(AU)

O hormônio Anti-Mülleriano (AMH) é uma proteína expressa nas gônadas e está relacionada ao desenvolvimento folicular ovariano. O objetivo desse trabalho foi investigar a presença de polimorfismos do gene AMH em um rebanho Nelore, analisar a constituição genética da população para o gene e estudar a associação entre os polimorfismos e as características ocorrência de prenhez precoce (OPP) e idade ao primeiro parto (IPP). Os dados fenotípicos consistiram da verificação da prenhez precoce e idade ao primeiro parto de 197 novilhas, não aparentadas, expostas à estação de monta com idade entre 15 e 17 meses (grupo precoce) ou 24 meses (grupo não precoce). O grupo denominado “precoce” foi composto por 67 novilhas com idade ao primeiro parto de 26.5±0.59 meses, e o segundo denominado “não precoce” composto por 130 novilhas com idade ao primeiro parto de 36.4±0.99 meses. Os cinco éxons do gene AMH foram amplificados por meio da técnica de Reação em Cadeia da Polimerase (PCR) e sequenciados. Um total de três SNPs foram identificados nesse estudo, todos localizados no éxon 5 (rs527023314, rs722016629 and rs134387246), sendo o último posicionado stop codon. Os três SNPs identificados caracterizaram mutações sinônimas. Somente o SNP rs134387246 exibiu associação significante (P ≤ 0.10) para ambas características (OPP e IPP). O estudo de associação do SNP rs134387246 revelou um efeito de sobre dominância (P=0,056), e ausência de ação gênica aditiva (P=0,67). Foi observada redução de 2,5 meses (75 dias) na idade ao primeiro parto de novilhas heterozigotas para o SNP rs134387246. Pela primeira vez na literatura, polimorfismos do gene AMH foram descritos em novilhas da raça Nelore e associados a características indicadoras de precocidade sexual.(AU)

AMH Polymorphisms and their association with traits indicative of sexual precocity in nelore heifers / Polimorfismos do AMH e suas associações com características indicadoras de precocidade sexual em novilhas nelore

Anti-Müllerian Hormone (AMH) is a protein expressed in the gonads and related to ovarian follicular development. The aim of this study was to investigate the presence of polymorphisms in the AMH gene in a Nelore herd to analyze the genetic constitution of this population and to perform association studies with early pregnancy occurrence (EPO) and age at first calving (AFC). Phenotypic data consisted of verification of early pregnancy and age at first calving of 197 unrelated heifers exposed to the mating season and aged between 15 and 17 months (precocious group) and 24 months (non-precocious group). The “precocious” group consisted of 67 heifers with age at first calving of 26.5 ± 0.59 months, and the “non-precocious” group was composed of 130 heifers with age at first calving of 36.4 ± 0.99 months. All five exons of the AMH gene were amplified by Polymerase Chain Reaction (PCR) and sequenced. A total of three SNPs were identified in this study, all of them located in exon 5 (rs527023314, rs722016629, and rs134387246), the latter one positioned in the stop codon. All three SNPs identified in exon 5 characterized synonymous mutations. Only SNP rs134387246 exhibited a significant value (P ≤ 0.10) for EPO and AFC. The association study of SNP rs134387246 revealed an over-dominance effect (P = 0.056), and no additive effect was observed (P = 0.67). A reduction of 2.5 months (75 days) in the age at first calving of heterozygous heifers for the SNP rs134387246 was observed. For the first time, polymorphisms of the AMH gene were described in Nelore heifers and associated with sexual precocity traits.

O hormônio Anti-Mülleriano (AMH) é uma proteína expressa nas gônadas e está relacionada ao desenvolvimento folicular ovariano. O objetivo desse trabalho foi investigar a presença de polimorfismos do gene AMH em um rebanho Nelore, analisar a constituição genética da população para o gene e estudar a associação entre os polimorfismos e as características ocorrência de prenhez precoce (OPP) e idade ao primeiro parto (IPP). Os dados fenotípicos consistiram da verificação da prenhez precoce e idade ao primeiro parto de 197 novilhas, não aparentadas, expostas à estação de monta com idade entre 15 e 17 meses (grupo precoce) ou 24 meses (grupo não precoce). O grupo denominado “precoce” foi composto por 67 novilhas com idade ao primeiro parto de 26.5±0.59 meses, e o segundo denominado “não precoce” composto por 130 novilhas com idade ao primeiro parto de 36.4±0.99 meses. Os cinco éxons do gene AMH foram amplificados por meio da técnica de Reação em Cadeia da Polimerase (PCR) e sequenciados. Um total de três SNPs foram identificados nesse estudo, todos localizados no éxon 5 (rs527023314, rs722016629 and rs134387246), sendo o último posicionado stop codon. Os três SNPs identificados caracterizaram mutações sinônimas. Somente o SNP rs134387246 exibiu associação significante (P ≤ 0.10) para ambas características (OPP e IPP). O estudo de associação do SNP rs134387246 revelou um efeito de sobre dominância (P=0,056), e ausência de ação gênica aditiva (P=0,67). Foi observada redução de 2,5 meses (75 dias) na idade ao primeiro parto de novilhas heterozigotas para o SNP rs134387246. Pela primeira vez na literatura, polimorfismos do gene AMH foram descritos em novilhas da raça Nelore e associados a características indicadoras de precocidade sexual.

Reproductive performance of heifers of different weight classes in the first and second mating / Desempenho reprodutivo de novilhas de distintas classes de peso no primeiro e segundo acasalamento

The objective of this study was to evaluate the effect of live weight at first mating on reproductive performance in the first and second reproductive years. For that purpose, the reproductive history of 221 heifers mated for the first time between the years of 2003 and 2012 was evaluated. Heifers were grouped into three weight classes at the age of 24 months: 50-59.9% (55%), 60-69.9% (65%), and 70-80% (75%). The pregnancy rate in the first reproductive year in heifers from weight classes 55%, 65%, and 75% was 38.0%, 56.4%, and 69.0%, respectively. The pregnancy rate in the second reproductive year was not affected by weight at first mating (p > 0.05) and corresponded to 41.6%; 42.1%, and 50.4% in the three weight classes, respectively. The weight class of heifers before mating at the age of 24 months affected reproductive performance at first mating but did not increase the pregnancy rate in the second reproductive year.(AU)

Objetivou-se avaliar o efeito do peso vivo ao primeiro acasalamento de novilhas sobre o desempenho reprodutivo na primeira e segunda monta. Para isso, foi avaliado o histórico reprodutivo de 221 novilhas de corte acasaladas pela primeira vez entre os anos de 2003 até 2012. As novilhas foram agrupadas em três classes de peso vivo aos 24 meses de idade, sendo eles: entre 50 a 59,9% do peso adulto (55%); de 60 a 69,9% do peso adulto (65%) e entre 70 a 80% do peso adulto (75%). A taxa de prenhez no primeiro ano reprodutivo foi de 38,0%; 56,4% e 69,0% às acasaladas com faixa de peso de 55%, 65% e 75%; respectivamente. A taxa de prenhez no segundo ano reprodutivo não sofreu efeito da classe de peso ao primeiro acasalamento (p > 0,05) com valores de 41,6%; 42,1% e 50,4%. A classe de peso antes do acasalamento de novilhas aos dois anos de idade interfere no desempenho reprodutivo na primeira monta, mas não resulta em aumento na taxa de prenhez no segundo ano reprodutivo.(AU)

Reproductive performance of heifers of different weight classes in the first and second mating / Desempenho reprodutivo de novilhas de distintas classes de peso no primeiro e segundo acasalamento

The objective of this study was to evaluate the effect of live weight at first mating on reproductive performance in the first and second reproductive years. For that purpose, the reproductive history of 221 heifers mated for the first time between the years of 2003 and 2012 was evaluated. Heifers were grouped into three weight classes at the age of 24 months: 50-59.9% (55%), 60-69.9% (65%), and 70-80% (75%). The pregnancy rate in the first reproductive year in heifers from weight classes 55%, 65%, and 75% was 38.0%, 56.4%, and 69.0%, respectively. The pregnancy rate in the second reproductive year was not affected by weight at first mating (p > 0.05) and corresponded to 41.6%; 42.1%, and 50.4% in the three weight classes, respectively. The weight class of heifers before mating at the age of 24 months affected reproductive performance at first mating but did not increase the pregnancy rate in the second reproductive year.

Objetivou-se avaliar o efeito do peso vivo ao primeiro acasalamento de novilhas sobre o desempenho reprodutivo na primeira e segunda monta. Para isso, foi avaliado o histórico reprodutivo de 221 novilhas de corte acasaladas pela primeira vez entre os anos de 2003 até 2012. As novilhas foram agrupadas em três classes de peso vivo aos 24 meses de idade, sendo eles: entre 50 a 59,9% do peso adulto (55%); de 60 a 69,9% do peso adulto (65%) e entre 70 a 80% do peso adulto (75%). A taxa de prenhez no primeiro ano reprodutivo foi de 38,0%; 56,4% e 69,0% às acasaladas com faixa de peso de 55%, 65% e 75%; respectivamente. A taxa de prenhez no segundo ano reprodutivo não sofreu efeito da classe de peso ao primeiro acasalamento (p > 0,05) com valores de 41,6%; 42,1% e 50,4%. A classe de peso antes do acasalamento de novilhas aos dois anos de idade interfere no desempenho reprodutivo na primeira monta, mas não resulta em aumento na taxa de prenhez no segundo ano reprodutivo.

A combination of nutrition and genetics is able to reduce age at puberty in Nelore heifers to below 18 months.

Nelore heifers usually begin their reproductive life at ⩾24 months of age mainly due to suboptimal nutritional conditions and genetics. This study aimed to determine the effect of expected progeny difference (EPD) for age at first calving and average daily gain (ADG) on puberty in Nelore (Bos taurus indicus) heifers. A total of 58 weaned heifers (initial BW=174±6 kg; age=9±1 months) were allocated into 28 feedlot pens. Heifers were born from four sires, of which two had low EPD for age at first calving (L; n=33) and two had high EPD for age at first calving (H; n=25). Then, heifers of each EPD were randomly assigned to high ADG (HG; 0.7 kg) or low ADG (LG; 0.3 kg), resulting in four treatments: heifers from L sires were submitted to either HG (LHG; n=17) or LG (LLG; n=16), and heifers from H sires were submitted to either HG (HHG; n=12), or LG (HLG; n=13). The HG heifers were fed a 75% grain diet, whereas the LG heifers received 93% of forage in their diet. Blood samples were collected at 9, 14, 18, 24 and 28 months of age for IGF1 and leptin determination. There was a treatment effect (P<0.01) on the proportion of heifers that attained puberty by 18 (62%, 0%, 0% and 0%), 24 (100%, 6%, 54% and 0%) or 36 (100%, 100%, 100% and 38%) months of age for LHG, LLG, HHG and HLG treatments, respectively. In addition, mean age at puberty was different across treatments (P<0.01). Heifers from the LHG achieved puberty at the earliest age when compared with cohorts from other treatments (18.1, 28.9, 23.9 and 34.5 months for LHG, LLG, HHG and HLG, respectively). Serum IGF1 concentrations were higher for L heifers compared with H cohorts at 9, 14, 18, 24 and 28 months of age (P<0.01; treatment×age interaction), whereas circulating leptin concentrations were higher (P<0.01; age effect) as heifers became older, regardless of the treatments. In conclusion, only Nelore heifers with favorable genetic merit for age at first calving were able to attain puberty by 18 months of age. In heifers with unfavorable genetic merit for age at first calving, supplementary feeding to achieve high ADG was unable to shift the age at puberty below 24 months.

Precocidade sexual, eficiência reprodutiva e desempenho produtivo de matrizes jovens Nelore e cruzadas / Sexual precocity, reproductive efficiency and productive performance of Nelore and crossbred young cows

Com o objetivo de avaliar matrizes da raça Nelore (NE) e cruzadas 1/2 Angus + 1/2 Nelore (AN), 1/2 Caracu + 1/2 Nelore (CN) e 1/2 Senepol + 1/2 Caracu (SC) quanto à precocidade sexual em sistemas de recria a pasto, eficiência reprodutiva e desempenho produtivo das matrizes em cada grupo genético (GG), matrizes desses grupos foram produzidas por três safras. Foram avaliadas 40 matrizes AN, 37 CN, 51 NE e 43 SC. Para prenhez precoce, matrizes AN apresentaram taxa de prenhez de 92,2% contra 29,1% para CN, 22,6% para SC e 1,1% para NE. Na prenhez convencional, matrizes AN obtiveram 99,4%, 98,8% para CN, 84,4% para SC e 80,0% para NE. A reconcepção das matrizes AN foi 86,3%, 75,1% de CN, 49,6% de NE e 43,6% de SC. Matrizes AN tiveram menor média de idade ao primeiro parto em meses, 26,36±0,79, contra 31,33±0,86 para CN, 33,51±0,98 para SC e 38,08±0,74 para NE. Para peso ao desmame, crias three-cross das AN pesaram mais que as F1 das NE, por volta de 19%. Para relação de peso ao desmame, não houve diferenças estatísticas entre GG. Matrizes AN foram superiores às demais nos aspectos reprodutivos e produtivos, seguidas das matrizes CN.(AU)

With the aim of evaluating Nelore (NE), 1/2 Angus + 1/2 Nelore (AN), 1/2 Caracu + 1/2 Nelore (CN), and 1/2 Senepol + 1/2 Caracu (SC) females for sexual precocity on pasture backgrounding, reproductive efficiency and productive performance of cows and their calves of each genetic group (GG), animals of these groups were produced for three years. A total of 40 AN, 37 CN, 51 NE and 43 SC cows were evaluated. For early heifer pregnancy, AN cows had pregnancy rate of 92.2% compared to 29.1% for CN, 22.6% for SC and 1.1% for NE. For conventional heifer pregnancy AN obtained 99.4%, CN with 98.8%, SC with 84.4% and NE with 80.0%. The first reconception of AN cows were 86.3%, 75.1% for CN, 49.6% for NE and 43.6% for SC. AN cows also had lower age at first calving in months, 26.36±0.79, compared to 31.33±0.86 for CN, 33.51±0.98 for SC and 38.08±0.74 for NE. For weaning weigth the three-cross from AN were heavier than the F1s from NE, by a margin of 19%. For calf:cow weight ratio there was no statistical difference among GG. AN cows were superior to the others in both productive and reproductive aspects, followed by the CN cows.(AU)

Precocidade sexual, eficiência reprodutiva e desempenho produtivo de matrizes jovens Nelore e cruzadas / Sexual precocity, reproductive efficiency and productive performance of Nelore and crossbred young cows

Com o objetivo de avaliar matrizes da raça Nelore (NE) e cruzadas 1/2 Angus + 1/2 Nelore (AN), 1/2 Caracu + 1/2 Nelore (CN) e 1/2 Senepol + 1/2 Caracu (SC) quanto à precocidade sexual em sistemas de recria a pasto, eficiência reprodutiva e desempenho produtivo das matrizes em cada grupo genético (GG), matrizes desses grupos foram produzidas por três safras. Foram avaliadas 40 matrizes AN, 37 CN, 51 NE e 43 SC. Para prenhez precoce, matrizes AN apresentaram taxa de prenhez de 92,2% contra 29,1% para CN, 22,6% para SC e 1,1% para NE. Na prenhez convencional, matrizes AN obtiveram 99,4%, 98,8% para CN, 84,4% para SC e 80,0% para NE. A reconcepção das matrizes AN foi 86,3%, 75,1% de CN, 49,6% de NE e 43,6% de SC. Matrizes AN tiveram menor média de idade ao primeiro parto em meses, 26,36±0,79, contra 31,33±0,86 para CN, 33,51±0,98 para SC e 38,08±0,74 para NE. Para peso ao desmame, crias three-cross das AN pesaram mais que as F1 das NE, por volta de 19%. Para relação de peso ao desmame, não houve diferenças estatísticas entre GG. Matrizes AN foram superiores às demais nos aspectos reprodutivos e produtivos, seguidas das matrizes CN.(AU)

With the aim of evaluating Nelore (NE), 1/2 Angus + 1/2 Nelore (AN), 1/2 Caracu + 1/2 Nelore (CN), and 1/2 Senepol + 1/2 Caracu (SC) females for sexual precocity on pasture backgrounding, reproductive efficiency and productive performance of cows and their calves of each genetic group (GG), animals of these groups were produced for three years. A total of 40 AN, 37 CN, 51 NE and 43 SC cows were evaluated. For early heifer pregnancy, AN cows had pregnancy rate of 92.2% compared to 29.1% for CN, 22.6% for SC and 1.1% for NE. For conventional heifer pregnancy AN obtained 99.4%, CN with 98.8%, SC with 84.4% and NE with 80.0%. The first reconception of AN cows were 86.3%, 75.1% for CN, 49.6% for NE and 43.6% for SC. AN cows also had lower age at first calving in months, 26.36±0.79, compared to 31.33±0.86 for CN, 33.51±0.98 for SC and 38.08±0.74 for NE. For weaning weigth the three-cross from AN were heavier than the F1s from NE, by a margin of 19%. For calf:cow weight ratio there was no statistical difference among GG. AN cows were superior to the others in both productive and reproductive aspects, followed by the CN cows.(AU)

Genotype × environment interactions in reproductive traits of Nellore cattle in northeastern Brazil.

We evaluate genotype × environment (G × E) interactions for age at first calving (AFC) and calving interval (CI) of Nellore cattle in northeastern Brazil using four hierarchical reaction norm models (HRNMs). The best-fit model for the traits was the one step heteroscedastic hierarchical reaction norm model. Heritability was close to zero in the worst environments and increased as the environments improved (from 0.06 to 0.12 for AFC and from 0.01 to 0.03 for CI). The correlations between the intercept and the slope of the reaction norms for CI and AFC were from medium to high magnitude (0.75 ± 0.10 and 0.90 ± 0.04, respectively), indicating that animals with higher average breeding values had the greatest responses to the improvement of environmental conditions. The variation in heritability indicates different response to selection according to the environment in which the animals of the population are evaluated. The G × E was evident in bulls with more female offspring. In conclusion, our data demonstrate that selection for AFC in medium- and high-level environments leads to higher genetic gains.

Seroprevalence and risk factors of several bovine viral diseases in dairy farms of San Pedro de los Milagros, Antioquia, Colombia / Seroprevalencia y factores de riesgo para varias enfermedades virales en bovinos de hatos lecheros de San Pedro de los Milagros, Antioquia, Colombia / Soroprevalência e fatores de risco para várias doenças virais em bovinos de rebanhos leiteiros do Município de San Pedro de los Milagros, Antioquia, Colômbia

Bovine viral diarrhea virus (BVDV), Bovine herpesvirus-1 (BoHV-1) and enzootic bovine leucosis (EBL) are viral infections that cause three of the most important cow diseases in the world. Antibody detection is the quickest and most cost-effective method to detect exposition to the virus. The aim of this study was to determine the seroprevalence and risk factors associated with these diseases in cows from the town of San Pedro de los Milagros, Antioquia. A total of 791 bovines of 24 dairy farms were sampled for blood between may and june of 2014, and analized for antibodies against BVDV and BoHV-1. These 24 farms plus other five were analized for antibodies against EBL for a total of 1003 bovines from 29 farms sampled. All tests were done with ELISA kits commercially available. The risk factors for farm and cow selected were evaluated to analize their relation with the serological state of these three diseases using logistic regression. In general, seroprevalence at the animal level for BVDV BoHV-1 and EBL was 75.7% (95% CI: 68.7-82.6%), 31.1% (95% CI: 22.1-40.1%) and 47.8% (95% CI: 40-55.7%), respectively. The odds ratio of being seropositive for BoHV-1 was significantly higher (OR=3.0) in animals older than 3 years in comparison to bovines younger than a year. Not using disposable needles was associated with prevalence of EBL. In conclusion there was a high seroprevalence of EBL and BVDV, and a lower one for BoHV-1. Seropositivity to BoHV-1 was associated with cows older than 3 years and seropositivity to EBL was associated with not using disposable needles in the farm.

Las infecciones por virus de la diarrea viral bovina (BVDV), el herpes virus bovino-1 (BoHV-1) y la leucosis enzoótica bovina (EBL) causan tres de las enfermedades más importantes de la vaca a nivel mundial. La detección de anticuerpos es el método más rápido y costo-efectivo para detectar la exposición a estos virus. El objetivo de este estudio fue determinar la seroprevalencia y los factores de riesgo asociados a estas enfermedades en vacas del municipio de San Pedro de los Milagros, Antioquia. Un total de 791 bovinos de 24 hatos lecheros no vacunados fueron muestreados para sangre entre mayo y junio de 2014 y analizados para anticuerpos contra BVDV y BoHV-1. Estos 24 hatos más otros cinco fueron analizados para anticuerpos contra EBL para un total de 1003 bovinos de 29 hatos. Todas las pruebas fueron efectuadas con kits de ELISA disponibles comercialmente. Los factores de riesgo de hato y de vaca seleccionados fueron evaluados para analizar su relación con el estado serológico de estas tres enfermedades por medio de regresión logística. En general, la seroprevalencia a nivel de animal para BVDV, BoHV-1 y EBL fue 75,7% (95% CI: 68,7-82,6), 31,1% (95% CI: 22,1-40,1) y 47,8% (95% CI: 40-55,7), respectivamente. La relación de disparidad de ser seropositivo para BoHV-1 fue significativamente más alto (OR=3,0) en animales mayores de 3 años en comparación con bovinos menores de un año. No usar agujas desechables en la granja estuvo asociada con la prevalencia a EBL. En conclusión hubo una alta seroprevalencia de EBL y BVDV y una baja para BoHV-1. La seropositividad a BoHV-1 estuvo asociada con vacas mayores a tres años y la seropositividad a EBL estuvo asociada con el no uso de agujas desechables en la granja.

As infecções por vírus da diarreia viral bovina (BVDV), herpes vírus bovino-1 (BoHV-1) e leucose enzoótica bovina (EBL) causam três das doenças mais importantes da vaca no mundo todo. A detecção de anticorpos é o método mais rápido e custo-efetivo para detectar a exposição a estes vírus. O objetivo desta pesquisa foi determinar a soroprevalência e os fatores de risco associados a estas doenças em vacas de diferentes rebanhos leiteiros do município de San Pedro de los Milagros, Antioquia, Colômbia. Um total de 791 bovinos pertencentes a 24 rebanhos leiteiros não vacinados foram amostrados para sangue entre os meses de maio e junho de 2014 e analisados para anticorpos contra BVDV e BoHV-1. Estes 24 rebanhos mais outros cinco foram analisados para anticorpos contra EBL para um total de 1003 bovinos de 29 rebanhos. Todos os testes foram feitos com kits de ELISA disponíveis comercialmente. Os fatores de risco do rebanho e do animal selecionados foram avaliados para analisar sua relação com o estado sorológico de estas três doenças por médio de regressão logística. Em geral, a soroprevalência no animal para BVDV, BoHV-1 e EBL foi 75,7% (95% CI: 68,7-82,6), 31,1% (95% CI: 22,1-40,1) e 47,8% (95% CI: 40-55,7), respetivamente. A relação de disparidade de ser soropositivo para BoHV-1 foi significativamente maior (OR=3,0) em animais maiores de três anos em comparação com os menores de um ano. O fato de não utilizar agulhas descartáveis na fazenda, esteve associada com a prevalência a EBL. Em conclusão, houve uma alta soroprevalência de EBL e BVDV e a sua vez, uma baixa para BoHV-1. A soropositividade a BoHV-1 esteve associada com vacas maiores a três anos e a soropositividade a EBL esteve associada com a não utilização de agulhas descartáveis na fazenda.

Heritabilities, correlations, and genetic trends for reproductive traits of a multiracial cattle population in Colombia / Heredabilidades, correlaciones y tendencias genéticas para características reproductivas en una población bovina multirracial en Colombia / Herdabilidades, correlações e tendências genéticas para características reprodutivas em uma população multirracial na Colômbia

The aim of this study was to estimate heritabilities, genetic correlations, heterosis and genetic trends for reproductive traits in a multiracial Angus-Brahman cattle population in the Colombian tropics. Records of age at first calving (EPP), first calving interval (PIEP) and second calving interval (SIEP) were evaluated from years 1993 to 2009. Data were analyzed using a tree-characteristic model that included the fixed effects of contemporary group (year-season for EPP, year-season-sex for PIEP and SIEP), direct additive genetic fixed effects of breed, individual heterosis; and direct additive genetic random effect of the animal, as well as the residual random effect. The variance components were estimated by the restricted maximum likelihood method, using the AIREML program. The estimated means were 38.5 ± 6.0, 18.4 ± 3.7, and 17.6 ± 2.77 months for EPP, PIEP and SIEP, respectively. The estimated heritabilities were 0.32 ± 0.09 for EPP, 0.04 ± 0.01 for PIEP, and 0.14 ± 0.05 for SIEP. A low and negative genetic correlation between direct effects for EPP and SIEP (-0.07 ± 0.23) was found. Genetic trend for EPP and SIEP was not significant (p>0.05), while it was significant (p≤0.05) for PIEP, although close to zero. The EPP heritability estimate suggests that genetic progress can be achieved for this feature through selection in few generations. Genetic trends indicate that the selection intensity applied to this multiracial population was not enough to influence its breeding values during the studied period.

El objetivo de este estudio fue estimar las heredabilidades, correlaciones genéticas, heterosis y tendencias genéticas para características reproductivas en una población bovina multirracial Angus-Brahman en el trópico bajo colombiano. Se evaluaron registros de edad al primer parto (EPP), primer intervalo entre partos (PIEP) y segundo intervalo entre partos (SIEP), desde el año 1993 hasta 2009. Los datos fueron analizados mediante un modelo tricarácter que incluyó los efectos fijos de grupo contemporáneo (año-época para EPP; año-época-sexo para PIEP y SIEP), efectos fijo genético aditivo directo de raza, heterosis individual; y los efectos aleatorios genéticos aditivos directos del animal y residual. Los componentes de varianza se estimaron por el método de máxima verosimilitud restringida, mediante el programa AIREML. Las medias estimadas fueron de 38,5 ± 6,0, 18,4 ± 3,7 y 17,6 ± 2,77 meses para EPP, PIEP y SIEP, respectivamente. Las heredabilidades estimadas fueron 0,32 ± 0,09 para EPP, 0,04 ± 0,01 para PIEP y 0,14 ± 0,05 para SIEP. Se encontró una baja correlación genética negativa entre efectos directos para EPPSIEP (-0,07 ± 0,23). Las tendencias genéticas para EPP y SIEP fueron no significativas (p>0,05), mientras que para PIEP fue significativa (p≤0,05), pero cercana a cero. El estimativo de heredabilidad para EPP, sugiere que a través de la selección en pocas generaciones se puede lograr progreso genético para esta característica en la población estudiada. Las tendencias genéticas indican que, la intensidad de selección aplicada a esta población multirracial no fue suficiente para influir sobre los valores de cría durante los años de estudio.

O objetivo desse estudo foi estimar as herdabilidades, correlações genéticas, heterose e tendências genéticas para características reprodutivas em uma população bovina multirracial Angus-Brahman no trópico baixo colombiano. Avaliaram-se registros de idade ao primeiro parto (EPP), primeiro intervalo entre partos (PIEP) e segundo intervalo entre partos (SIEP), desde 1993 até 2009. Os dados foram analisados mediante um modelo tricaráter que incluiu os efeitos fixos do grupo contemporâneo (anoépoca para EPP, ano-época-sexo para PIEP e SIEP), efeito fixo genético aditivo direto da raça, heterose individual e os efeitos aleatórios genéticos aditivos diretos do animal e residual. Os componentes de variância estimaram-se pelo método de máxima verossimilhança restrita, mediante o programa AIREML. As medias estimadas foram de 38,5 ± 6,0, 18,4 ± 3,7 e 17,6 ± 2,77 meses para EPP, PIEP e SIEP, respectivamente. As herdabilidades estimadas foram, EPP= 0,32 ± 0,09; PIEP= 0,04 ± 0,01; SIEP= 0,14 ± 0,05. Encontrou-se uma correlação genética negativa baixa entre os efeitos diretos para EPP-SIEP (-0,07 ± 0,23). As tendências genéticas para EPP e SIEP foram não significativas (p>0,05), enquanto que para PIEP foi significativa (p≤0,05), mas perto de cero. O estimativo de herdabilidade para EPP, sugere que a través da seleção em poucas gerações é possível lograr progresso genético para esta característica na população estudada. As tendências genéticas indicam que, a intensidade de seleção aplicada a esta população multirracial não foi suficiente para influir sob os valores de cria durante os anos de estudo.

Genetic improvement of Nellore cattle in the semi-arid region of northeastern Brazil / Melhoramento genético de bovinos Nelore na região semi-árida do nordeste do Brasil

The semi-arid region of Brazil represents approximately 57% of the northeastern territory. The main economic activity in this region is agriculture and livestock, in most cases, using traditional technologies. However, there is little published information currently available on cattle-raising in this part of Brazil. The objective of this study was to estimate genetic parameters and trends for productive and reproductive traits of Nellore cattle raised in semi-arid region of northeastern Brazil. Data were collected on weight-adjusted at 205 (W205), 365 (W365) and 550 (W550) days of life, age at first calving (AFC), calving interval (CI) and scrotal circumference (SC) at 550 days of life of cattle born between 1965 and 2011. Estimates of covariance and variance were obtained through univariate analysis using a Gibbs sampler. The estimated coefficients of heritability (mode) were 0.27 (W205), 0.36 (W365) and 0.39 (W550), 0.37 (SC), 0.22 (AFC) and 0.03 (CI). Little or no gain from selection is apparent in the genetic trend analysis over the 45 years of the study. However, environmental improvement has allowed phenotypic progress in growth traits and age at first age calving.

A região semiárida do Brasil representa aproximadamente 57% do território nordestino. A principal atividade econômica da região é a agricultura e pecuária e, na maioria dos casos, utilizando tecnologias tradicionais. No entanto, há poucas informações publicadas, sobre a criação de bovinos nesta parte do Brasil. O objetivo deste estudo foi estimar parâmetros e tendências genéticas para características produtivas e reprodutivas de bovinos Nelore criados na região semiárida do nordeste do Brasil. Foram coletados dados ajustados aos 205 (P205), 365 (P365) e 550 (P550) dias de vida, idade ao primeiro parto (IPP), intervalo entre partos (IP) e perímetro escrotal (PE) aos 550 dias de idade em bovinos nascidos entre 1965 e 2011. As estimativas de variância e covariância foram obtidas por meio de análise univariada usando um amostrador de Gibbs. Os coeficientes estimados de hereditariedade (moda) foram de 0,27 (P205), 0,36 (P365) e 0,39 (P550), 0,37 (PE), 0,22 (IPP) e 0,03 (IP). Pouco ou nenhum ganho de seleção foi encontrado na análise de tendência genética ao longo dos 45 anos do estudo. No entanto, a melhoria do ambiente permitiu progresso fenotípico das características de crescimento e idade ao primeiro parto.