Detecção de QTL em dados de famílias estruturadas como as de um núcleo MOET por meio do método da regressão / QTL detection in MOET nucleus family structure-like data using the regression method

O objetivo deste trabalho foi avaliar a eficiência do método de regressão em detectar QTL com base na utilização de dados da estrutura de família (irmãos completos e meios-irmãos), como aqueles gerados em um núcleo MOET. Foram simulados dados fenotípicos e genotípicos em uma estrutura de núcleo MOET fechado de seleção. Três arquivos foram analisados, contendo: a) informações conjuntas de irmãos completos e meios-irmãos; b) apenas informações de irmãos completos e c) apenas informações de meios-irmãos. Verificou-se que o método da regressão, para dados discretos ou contínuos, foi capaz de detectar associações entre marcador e QTL em níveis bastante expressivos de significância (P<0.001 e P<0,0001), quando se utilizou o arquivo que continha informações conjuntas de irmãos completos e meios-irmãos. Os resultados indicaram a possibilidade de utilização dessa metodologia para estudos de detecção/validação de QTL em rebanhos ou núcleos de seleção que utilizam MOET.

The objective of this study was to evaluate the efficiency of the regression method to detect QTL using data from full and half-sib families, like those generated in a MOET nucleus. For this study, genotypic and phenotypic data were simulated in a structure of a closed selection MOET nucleus. Three files were analyzed containing: a) the joint information of full and half sibs; b) only full sibs data; and c) only half sibs data. The method of regression, for continuous or discrete data, was able to detect associations of marker and QTL in very expressive levels of significance (P<0.001 P<0.0001), when the file containing the joint information of full and half sisters was used. The results indicated the possibility of using this methodology for studies of QTL detection / validation in MOET nucleus or herds under selection.

Parâmetros genéticos entre características de leite, de peso e a idade ao primeiro parto em gado mestiço leiteiro (Bos taurus x Bos indicus) / Genetic parameters between milk traits, weight traits and age at first calving in crossbreed dairy cattle (Bos taurus x Bos indicus)

Foram estimadas as correlações genéticas entre características de produção de leite (produção de leite, gordura, proteína e duração da lactação em até 305 dias, na primeira lactação), características de peso (taxa de crescimento de novilhas entre 12-24 meses e peso médio de vacas) e idade ao primeiro parto, em uma população de fêmeas Mestiço Leiteiro Brasileiro (MLB), por meio de metodologia REML, sob modelo animal. As estimativas de herdabilidade das características estudadas na ordem acima foram, respectivamente, 0,28± 0,08, 0,30±0,11, 0,28±0,09, 0,19±0,07, 0,18±0,06, 0,42±0,10 e 0,48±0,12. As correlações genéticas entre peso médio da vaca e a produção de leite, gordura e proteína foram, respectivamente, -0,22±0,22, -0,49±0,31 e -0,22±0,23 e da taxa de crescimento das novilhas com a produção de leite, gordura e proteína foram respectivamente, -0,59±0,35, -0,73±0,44 e -0,62±0,37. As correlações genéticas entre produção de leite, peso médio das vacas e taxa de crescimento das novilhas com idade ao primeiro parto foram respectivamente, 0,05±0,18, -0,05±0,18 e 0,02±0,20. A alta correlação genética (0,93±0,02) entre produção de leite e duração da lactação indicou que não se deve remover a variação na duração da lactação na seleção de gado leiteiro tropical

Genetic correlations between milk production (milk, fat, protein yield lactation length in 305-d lactation), live weight (average cow live weight, growth rate between 12-24 mo) and age at first calving traits were estimated in a population of Mestiço Leiteiro Brasileiro (MLB) females using REML methodology and animal model. The estimates of heritability were respectively, 0.28± 0.08, 0.30±0.11, 0.28±0.09, 0.19±0.07, 0.18±0.06, 0.42±0.10 and 0.48±0.12 for those traits. Genetic correlations between milk, fat and protein yield with cow average weight were, respectively, -0.22±0.22, -0.49±0.31, -0.22±0.23, and between milk, fat and protein yield with heifer live weight gain, -0.59±0.35, -0.73±0.44, -0.62±0.37 as well. Genetic correlations between milk yield, cow average weight and heifer live weight gain with age at first calving were, respectively, 0.05±0.18, -0.05±0.18, 0.02±0.20. The high genetic correlation between milk production and lactation length (0.93±0.02) indicated that variation of the lactation length should not be removed when selecting tropical dairy cattle

DGAT1 K232A polymorphism in Brazilian cattle breeds

Recent reports identified DGAT1 (EC 2.3.1.20) harboring a lysine to alanine substitution (K232A) as a candidate gene with a strong effect on milk production traits. Our objective was to estimate the frequency of the DGAT1 K232A polymorphism in the main Zebu and Taurine breeds in Brazil as well as in Zebu x Taurine crossbreds as a potential QTL for marker-assisted selection. Samples of 331 animals from the main Brazilian breeds, Nellore, Guzerat, Red Sindhi, Gyr, Holstein, and Gyr x Holstein F1 were genotyped for DGAT1 K232A polymorphism (A and K alleles) using the PCR-RFLP technique. The highest frequency of the A allele was found in the Holstein sample (73%) followed by Gyr x Holstein F1 (39%). Gyr and Red Sindhi showed low frequencies of A alleles (4 and 2.5%, respectively). The A allele was not found in the Nellore and Guzerat samples. Our results could be used to guide association studies between this locus and milk traits in these breeds.

Association of BoLA-DRB3.2 alleles with tick (Boophilus microplus) resistance in cattle

Losses caused by bovine tick burdens in tropical countries have a tremendous economic impact on production systems. Besides reducing production, this parasite can cause death in the most susceptible animals. The use of commercial acaricides has been the major method of control, but their misuse has led to tick resistance to many chemicals. More recently, vaccines have been used in some countries without solving the problem completely. An alternative could be the development of resistant animals and the use of genetic markers and candidate genes that could help with the enormous task of selecting resistant animals. The bovine lymphocyte antigen genes (BoLA) have been shown to be associated with some parasitic infestations and disease incidence. Thus, the objective of the present study was to determine the association of BoLA-DRB3.2 alleles with tick resistance in cattle. The study was conducted on 231 F2 (Gyr x Holstein) animals that were artificially infested with 10,000 tick larvae. Log of tick count +1 was used as the dependent variable in a mixed animal model with allele substitution effects in addition to fixed effects of year and season at tick count, sex of calves, age of animal at tick count, hair type (short-straight, short-curl, long-straight, and long-curl), coat color (white, >75% white, 50- 75% white, and 25-50% white), and additive genetic, permanent environmental and residual effects as random. Females showed fewer ticks than males. Animals with short-straight hair were more resistant to tick infestation than animals with long-curl hair, and animals with whiter coat color also had fewer ticks. An association between BoLA alleles and lower tick number was found for alleles DRB3.2 *18, *20 and *27 at the 5% significance level. Also, one allele (DRB3.2*16) showed an association at the 10% level. Allele *27 was the most frequent in the population (30.7%), followed by alleles *16 (10.8%), *20 (8.7%) and *18 (2.4%)...

Genetic trend for milk yield in Guzerat herds participating in progeny testing and MOET nucleus schemes

Genetic trends for 305-day milk yield (P305) in Brazilian Guzerat herds under selection were compared. Data from 4898 lactations of 3179 purebred and crossbred cows from various regions of Brazil were used. Milk yield was adjusted for mature age and the contemporary groups were defined as herd and calving year. Genetic parameters were estimated using the MTDFREML program. The model included the random effects of animals and permanent environment, and herd-calving year, calving season and genetic composition as fixed effects. Genetic trends were estimated by linear regression of weighted average estimated breeding values as a function of calving year. The average P305 was 2065 ± 922 kg and the heritability was 0.23 ± 0.03. The annual genetic trend in estimated breeding values of cows for P305 was 7.09 ± 0.71 kg between 1987 and 2004, and 6.47 ± 2.35 kg between 1997 and 2004. For cows born and raised in the multiple ovulation and embryo transfer (MOET) nucleus, this trend was 36.46 ± 24.54 kg/year between 1997 and 2004, 183.14 ± 47.94 kg/year between 1997 and 2000, and 9.13 ± 19.19 kg/year between 2001 and 2004. An average inbreeding coefficient of 0.04 was found for inbred MOET cows in 2004. Increasing the size of the family and introducing new progenies changed reliabilities and predicted transmitting ability estimates of MOET sires. In conclusion, there was a positive genetic trend for milk yield in the MOET nucleus at low inbreeding coefficients due to the increased accuracy and estimated genetic merit, but no changes in the average milk yield were observed.

Associação do loco BoLA-DRB3.2 com produção de leite em bovinos da raça Gir / Association of BoLA-DRB3.2 locus with bovine milk production in Gir breed

A associação entre os alelos do loco BoLA-DRB3.2, identificados pela técnica de PCR-RFLP, e a produção de leite na raça Gir foi estudada por meio da análise de dados moleculares e fenotípicos de 424 vacas Gir, utilizando um modelo misto, sob modelo animal. Os dados moleculares consistiam dos genótipos dos animais para os alelos do loco BoLA-DRB3.2 e os dados fenotípicos eram referentes à produção de leite em até 305 dias de lactação. O loco é altamente polimórfico nesta raça, sendo identificados sete alelos (BoLA-DRB3.2*4, *8, *11, *19, *28, *41 e *48) que não haviam sido encontrados em animais zebuínos. Dois alelos (*16 e *29) estavam significativamente associados com maiores produções de leite, sugerindo que o próprio loco BoLA-DRB3.2 ou um QTL a ele ligado influencia a produção de leite de vacas Gir.

Evaluation of crosses of Holstein, Jersey or Brown Swiss sires x Holstein-Friesian/Gir dams. 3. Lifetime performance and economic evaluation

Lifetime dairy production, reproduction and growth traits of 75 females sired by Holstein, Jersey or Brown Swiss bulls and Holstein-Friesian x Gir dams of 1/2 to 3/4 Holstein-Friesian fractions were compared. The animals were in a single herd under the same management. Milk, fat and protein yields, concentrates fed, reproduction, and weights were recorded throughout the lifetime of the cows. The data were analyzed by least squares techniques under models including the fixed effects of breed of sire, Bos taurus fraction and year of birth. Herd lifes for Holstein, Jersey and Brown Swiss crosses were 6.006 +/- 0.812, 8.129 +/- 0.863 and 7.247 +/- 0.777 years. Milk yields per day of herd life were 7.150 +/- 0.266, 6.757 +/- 0.282 and 6.249 +/- 0.254 kg. Weights of cull cows sold were 458 +/- 15, 415 +/- 15 and 457 +/- 13 kg. Based on these and on previously reported results of the same experiment, intakes of roughage and pasture were estimated from energy requirements. Lifetime expenditures on concentrates, roughages, pastures, milking, reproduction, and heifer rearing were calculated based on mean performance of each breed of sire, as well as on receipts from animals and milk sold (the latter with four sets of prices of protein, fat and carrier). The conclusion was that in systems of artificial female calf rearing and male calf wastage, the Jersey crosses appear to offer important economic benefits to farmers, which would be even greater if payment on milk protein and fat becomes effective

Relationships of weight and height with age in hybrid Holstein-Friesian/Guzera females

Serial data on live weights, height at withers and the weight/height ratio of 263 cows (3 to 9 years old) and 196 heifers (2 to 5 years old) were studied. The animals were of six red and white Holstein-Friesian (HF)/Guzera crosses (1/4, 1/2, 5/8, 3/4, 7/8 and > or = 31/32 HF-expected gene fraction). Separate analyses were performed for cows and heifers using the Proc Mixed of the SAS package. Models included the fixed effects of farm, season, reproductive and lactation status, two-factor interactions, quadratic regressions on age and age x crossbred group interaction, as continuous co-variables and regressions on the HF gene fraction and on breed heterozygosity, plus the animal random effect. Only heifer growth in height and weight/height was linear with age. In all three traits in both categories the individual additive-dominance model explained the variation between crossbred groups. The breed additive difference was not significant (P > 0.05) for cow and heifer live weight and for heifer weight/age ratio. Heterosis was significant for all traits except height of cows. Linear and quadratic regression coefficients for cows, were, respectively, for live weight, 35.20 +/- 5.23 kg/year and -1.54 +/- 0.43 kg/year2, for withers height, 2.49 +/- 0.29 cm/year and -0.15 +/- 0.02 cm/year2 and for weight/height, 0.22 +/- 0.04 kg/cm/year and -0.01 +/- 0.003 kg/cm/year2. Corresponding values for heifers were, for live weight, 153.46 +/- 37.06 kg/year and -15.69 +/- 4.91 kg/year2, while only linear coefficients applied to withers height (1.63 +/- 0.43 cm/year) and weight/height (0.16 +/- 0.03 kg/cm/year)

Evaluation of crosses of Holstein, Jersey or Brown Swiss sires x Holstein-Friesian/Gir dams. 2. Female liveweights

The liveweights of 100 females sired by Holstein (H), Jersey (J) or Brown Swiss (BS) bulls out of Holstein-Friesian x Gir dams of 1/2 to 3/4 Holstein-Friesian fraction were compared. The animals were kept in a single herd under the same management. The data were analyzed separately for four age categories by least squares techniques. The models for cows and heifers older than 18 months included the fixed effects of breed of sire, Bos taurus fraction, season of weighing, days in milk class (for cows only), pregnancy status class, year and the random effect of animal nested within breed of sire x B. taurus fraction subclasses. The models for younger heifers included the same effects except for lactation and pregnancy status. Based on 2937 observations, the mean weights for 0- to 6-month-old calves for the groups with H, J or BS sires were 88 +/- 1, 77 +/- 1 and 75 +/- 1 kg, respectively, the mean weights for 1-year-old heifers were 168 +/- 2, 159 +/- 2 and 155 +/- 1 kg, for 2-year-old heifers, 327 +/- 4, 303 +/- 4 and 319 +/- 4 kg, for 3-year-old heifers, 380 +/- 5, 369 +/- 8 and 390 +/- 4 kg and for cows, 464 +/- 3, 413 +/- 2 and 478 +/- 2 kg. Cubic growth curves, which were different in the three sire breed groups, satisfactorily explained the cow weight changes with age (R(2)>or=0.98). Maximum weight was attained at 7.8, 9.5 and 9.2 years in cows with H, J or BS sires. Although breed of sire effects were not significant in heifers (P>0.05), those with H sires were the heaviest up to two years of age. The females with BS or J sires had similar weights up to one year of age, but thereafter the former reached similar weights as the females with H sires and declined less after attaining the maximum weight. The cows with J sires were the lightest at all ages. Since previous results showed similar protein and fat yields per day of calving interval in the three breed of sire groups, it is suggested that the lighter J crosses may be more economic than the other groups on account of their likely lower feed maintenance costs

Taxa de gestaçäo em fêmeas da raça Holandesa confinadas em free stall, no veräo e inverno / Gestation rate of Holstein females confined in free stall, during the summer and winter

A taxa de gestaçäo de vacas em lactaçäo e de novilhas confinadas em free stall foi avaliada durante o inverno e o veräo, nos anos de 1993, 1994 e 1995. A temperatura ambiente (TA) e a umidade relativa do ar (UR) foram acompanhadas diariamente, durante quatro meses de veräo (dezembro a março) e três meses de inverno (junho a agosto). Em cada estaçäo mediram-se semanalmente às 9, 15 e 21h a temperatura retal (TR) e a freqüência respiratória (FR) de 50 por cento das vacas em lactaçäo, sorteadas ao acaso, separadas em quatro grupos de acordo com a produçäo de leite. A TA e o índice de temperatura e umidade (ITU) médios foram mais elevados (P < 0,05) no verao (25,6§C e 75,8) do que no inverno (19,0§C e 65,3), enquanto que a UR média foi a mesma nas duas estaçöes (80,0 por cento). As médias da TR e FR foram sempre mais elevadas no veräo e também às 15h, em comparaçäo com às das 9h (39,5§C e 64,8 mov/min versus 38,9§C e 44,2 mov/min). A taxa de gestaçäo das vacas em lactaçäo foi menor no veräo (45,7 por cento) do que no inverno (71,2 por cento). Entre as novilhas 85,4 por cento ficaram gestantes no veräo e 78,3 por cento no inverno (P<0,05)

Comparaçäo do desempenho de vacas mestiças Holandês com Guzerá de origem leiteira e näo leiteira / Comparative performance of \"dairy\" and \"non dairy\" Guzera x Holstein-Friesian progenies

Comparou-se o desempenho de 30 vacas 1/4 HVB, filhas de sete touros Guzerá considerados leiteiros com o desempenho de 57 vacas também 1/4 HVB, filhas de oito touros näo leiteiros, usando-se dados de primeira lactaçäo, iniciadas entre 1980 e 1986, em 65 fazendas da Regiäo Sudeste. As médias ajustadas pelo método dos quadrados mínimos das produçöes de leite, de gordura e de proteína, duraçäo da lactaçäo, percentuais de gordura e proteína, intervalo entre partos e idade ao primeiro parto foram, para ambos grupos, respectivamente, 1.131 mais ou menos 169 e 1.092 mais ou menos 134kg, 49 mais ou menos 7 e 46 mais ou menos 6kg, 37 mais ou menos 5 e 35 mais ou menos 4kg, 240 mais ou menos 23 e 240 mais ou menos 18 dias, 4,2 mais ou menos 0,2 e 4,0 mais ou menos 0,1 por cento, 3,3 mais ou menos 0,1 e 3,1 mais ou menos 0,1 por cento, 17,6 mais ou menos 1,0 e 17,0 mais ou menos 0,8 meses e 46,5 mais ou menos 1,0 e 48,0 mais ou menos 0,8 meses. As diferenças entre grupos foram pequenas e näo significativas (P>0,16), näo justificando o qualificativo "leiteiro" dos pais. Comparou-se também o desempenho de 53 vacas F1, filhas de pais HVB e mäes Guzerá oriundas de dois rebanhos leiteiros, com o de 32 filhas dos mesmos pais e mäes Guzerá oriundas de três rebanhos de corte. As médias dos grupos, na mesma ordem das características citadas foram respectivamente, 2.687 mais ou menos 135 e 2,429 mais ou menos 165kg, 115 mais ou menos 6 e 104 mais ou menos 7kg, 85 mais ou menos 4 e 75 mais ou menos 5kg, 367 mais ou menos 18 e 329 mais ou menos 22 dias, 4,1 mais ou menos 0,1 e 4,2 mais ou menos 0,2 por cento, 3,1 mais ou menos 0,1 e 3,0 mais ou menos 0,1 por cento, 18,2 mais ou menos 0,9 e 16,0 mais ou menos 1,0 meses e 43,9 mais ou menos 0,8 e 45,2 mais ou menos 1,0 meses. Somente a diferença no intervalo entre partos foi significativa (P<0,05)

Variaçäo temporal do efeito do bicromato de potássio na conservaçäo de amostras de leite destinadas à análise em laboratório central / Time effect of potassium bichromate upon milk composition prior to laboratory testing

Foram analisadas, pelo método do quadrados mínimos, 13.189 registros de controles leiteiros mensais de 467 vacas de seis grupos genéticos (cruzamentos HVB x Guzerá), distribuídas em 65 fazendas agrupadas em cinco sub-regiöes da Regiäo Sudeste. As amostras, com adiçäo de 0,1 por cento p/v de K2Cr2O7 eram enviadas ao Centro Nacional de Pesquisa em Gado de Leite (CNPGL) para análise dos percentuais de gordura (PG) e proteína (PP). O período coleta-análise (t) variou de 0 a 28 dias. Após análises preliminares, adotou-se um modelo estatístico incluindo os efeitos da sub-regiäo, grupo genético, ano e mês da coleta, com duas regressöes lineares com inclinaçöes diferentes (c1 e c2), em cada um dos períodos t<8 e t>=8 dias. As regressöes dentro de sub-regiäo foram homogêneas para PG mas näo para PP (P=0,003). Em média, para a Regiäo Sudeste, os coeficientes das regressöes c1 e c2, foram, respectivamente, para PG, 0,0007 mais ou menos 0,0061 e -0,0147 mais ou menos 0,0049 unidades percentuais por dia após a coleta e para PP, 0,0023 mais ou menos 0,0023 e -0,0062 mais ou menos 0,0019 nas mesmas unidades. Entre as sub-regiöes, c1 para PP variou de -0,0038 mais ou menos 0,0082 a 0,0155 mais ou menos 0,0064 por dia, enquanto que c2 variou de -0,0178 mais ou menos 0,0041 a 0,0065 mais ou menos 0,0060. Pela baixa magnitude dos c1, evidencia-se a eficiência do conservador nos primeiros oito dias após a coleta. As análises devem ser feitas dentro deste prazo, mas se näo o forem, as equaçöes apresentadas poderäo eventualmente ser utilizadas para correçäo estatística

Comparative performance of six holstein-friesian X guzera crossbred groups in Brazil: health costs of calves

Costs of drugs for pneumoenteritis and plasmosis treatment were evaluated in 614 bucket reared female calves of six Holstein-Friesian (HF) x Guzera crossbred groups (1/4 to > 31/32 HF gene fraction). Important heterosis effects resulted in lowest health costs for F(l) (US$ 4.33 per calf) and highest costs for > 31132 HF calves (US$ 8.01).