Strategies for the identification of precocity in zebu beef cattle based on mixed nonlinear models and multivariate approach.

The use of mixed nonlinear models reduces the residual variance by including random effects, thereby improving the estimates in growth curves. Therefore, we tested distinct mixed nonlinear models (Richards, Brody, Gompertz, Logistic, and Von Bertalanffy) to model the growth curves of Zebu cattle herds raised on pasture in Brazil. In addition, we evaluated the diversity among breeds using hierarchical cluster multivariate analysis (full linkage) based on asymptotic weight (A), maturity rate (K), absolute growth rate (AGR), and absolute maturity rate (AMR) adjusted to 205, 365, 550, and 730 days of age. Body weight data from 311,834 males and females of Guzerat, Nellore, Tabapuã, and Polled Nellore breeds provided by the Brazilian Association of Zebu Breeders were used. The Brody model considering breed-sex fixed and animal random effects was the most suitable to describe the growth in the four breeds. The Guzerat and Tabapuã males showed increased precocity (higher K values) when compared to polled Nellore and Nellore males, which were characterized by higher A and AMR values. Females were more precocious than males (high K and low A values), particularly within Tabapuã and Guzerat breeds, respectively. Regardless of sex, the highest AGR values were observed from weaning up to 2 years of age in Tabapuã and Guzerat breeds. The cluster analyses revealed two groups: (1) Polled Nellore and Nellore males with high A, AGR_205, AGR_365, AGR_550, and AGR_730 values, represented by large adult animals, and (2) males and females of Guzerat and Tabapuã, characterized as animals of increased precocity. A subgroup encompassing males of Guzerat and Tabapuã was also observed, with intermediate values ​​for all parameters. This information is useful to help breeders and producers in strategies for feeding management and defining the most precocious beef cattle breed to increase the economic gains in pasture-based raising systems.

Phenotypic differences for growth, feed efficiency, and age of first calving of Brazilian zebu females.

This study investigated phenotypic differences of zebu females from four breeds using variables of growth, feed efficiency, and age at first calving. Weights throughout the life were recorded, and a growth curve was fitted using the Gompertz model. The growth was also evaluated at standardized ages (205, 365, and 550 days) using the body weight and the total and daily weight gains. The Kleiber index and age at first calving were used as measures of feed efficiency and sexual precocity, respectively, totaling 25 variables. New variables were created using the factor analysis and used in new multivariate analyzes. Only six factors explained 95.41% of the total variance and were used for the subsequent analyses. The factors were defined as maturity, precocity, feed efficiency postweaning, feed efficiency post 1 year of age, puberty, and birth weight. There were differences between breeds according to the multivariate analysis of variance. Each breed appeared in a quadrant on the Biplot graph, showing relationship with different factors, demonstrating the diversity of zebu females. There is a difference in growth, feed efficiency, and sexual precocity in Brazilian zebu females, allowing the identification of potentials of the animals and help breeders and decision-makers.

Genotype by environment interaction for fat and protein yields via reaction norms in Holstein cattle of southern Brazil.

Our objective was to evaluate the genetic merit of Holstein cattle population in southern Brazil in response to variations in the regional temperature by analyzing the genotype by environment interaction using reaction norms. Fat yield (FY) and protein yield (PY) data of 67 360 primiparous cows were obtained from the database of the Paraná Holstein Breeders Association, Brazil (APCBRH). The regional average annual temperature was used as the environmental variable. A random regression model was adopted applying mixed models with Restricted Maximum Likelihood (REML) algorithm using WOMBAT software. The genetic merit of the 15 most representative bulls, depending on the temperature gradient, was evaluated. Heritability ranged from 0.21 to 0.27 for FY and from 0.14 to 0.20 for PY. The genetic correlation observed among the environmental gradients proved to be higher than 0.80 for both traits. Slight reranking of bulls for both traits was detected, demonstrating that non-relevant genotype by environment interaction for FY and PY were observed. Consequently, no inclusion of the temperature effect in the model of genetic evaluation in southern Brazilian Holstein breed is required.

Genotype-environment interaction for age at first calving in Holstein cows in Brazil.

Dairy cattle production is distributed throughout the Brazilian regions. However, Brazilian producing regions are different in air temperature and humidity, diet, birth season, and other factors that may alter the reproductive performances of cows. The age of the cow at first calving (AFC) is a good indicator of sexual precocity since it shows the beginning of the female reproductive life and has a great influence on cow replacement costs. Researches on genotype-environment interaction (GEI) show the importance of using specific bulls for the different production systems in Brazil since most semen used in the country is imported. The objective of this work was to evaluate GEI for AFC in Holstein cows in Brazil, using reaction norms. The statistical models used were the standard animal model, which disregards the GEI, and hierarchical reaction norm models with homoscedastic (HRNMHO) and heteroscedastic (HRNMHE) residual variance, and one (HRNMHO1S and HRNMHE1S) and two (HRNMHO2S and HRNMHE2S) steps. HRNMHO1S presented better fit to the data, with lower heritability for environments with lower AFC, and higher heritability for environments with higher AFC. The GEI found was complex, with a reclassification of bulls, denoting the importance of considering GEI for evaluation and selection of bulls for different production levels. The reduction of AFC is possible when using breeding bulls adapted to the tropical and subtropical conditions of Brazil.

Genotype-environment interaction for productive traits of Holstein cows in Brazil described by reaction norms.

Brazil is the world's fourth largest milk producer; this activity extends throughout the national territory, with productions of approximate 34 billion liters of milk per year. The objective of this work was to evaluate the genotype-environment interaction (GEI) in purebred Holstein cows for milk (M), protein (P), and fat (F) yields. The statistical models used were the standard animal model (AM), which disregards the GEI, and hierarchical reaction norm models with homoscedastic (HRNMHO) and heteroscedastic (HRNMHE) residual variance, and one (HRNMHO1S and HRNMHE1S) and two (HRNMHO2S and HRNMHE2S) steps. HRNMHO1S presented a better fit of the data for all traits, with higher heritability for the best environments. Most bulls presented robust phenotypes; however, GEI was found with a reclassification of the bulls in the environmental gradient. Although few, and less used, bulls with plastic phenotypes were found for all traits, and the use of them can optimize genetic gains in specific environments.

Morphofunctional diversity of equine of varied genetic compositions raised in the Pantanal biome of Brazil.

Evaluating phenotypic diversity makes it possible to identify discrepancies in aptitudes among animals of different genetic bases, which is an indicator of adaptive or selective differences between populations. The objective of this work was to evaluate the morphofunctional diversity of 452 male and female adult equines (Arabian, Quarter Mile, Pantaneiro, and Criollo breeds, and undefined crossbreeds of horses and mules) raised in the Pantanal biome (Brazil). Linear measurements were performed to estimate conformation indexes. Initially, a discriminant analysis was performed, regardless of the animal's size, followed by factor analysis. The factors were characterized and used as new variables. The diversity among equines and their relationship with the factors were evaluated using multivariate analysis. The factors were classified according to their decreasing importance: balance, rusticity, and robustness for the measurement factors; and load, ability, conformation, and equilibrium for the index factors. The genetic groups of equines have well-defined morphofunctional characteristics. The main differences are based on the rusticity and ability typologies in relation to those based on performance. Equines introduced to the Pantanal biome presented a more robust and compact body with good conformation. As a result, these horses may have superior athletic performance during equestrian activities when compared to the Pantaneiro local breed. However, this biotype may represent less rusticity (less adaptive capacity). Therefore, the regional breed can be equal or better in equestrian activities than breeds introduced to the Pantanal biome. Thus, breeders may cross horses from local breeds as an alternative to those introduced. Undefined crossbred male equines presented a different profile from the Pantaneiro breed, which may indicate little use of crossbreeds in breeding.

Genetic diversity, population structure, and correlations between locally adapted zebu and taurine breeds in Brazil using SNP markers.

Genetic diversity is one of the most important issues in studies on conservation of cattle breeds and endangered species. The objective of this study was to estimate the levels of genetic differentiation between locally adapted taurine (Bos taurus taurus) and zebu (Bos taurus indicus) breeds in Brazil, which were genotyped for more than 777,000 SNPs. The fixation index (F ST), principal component analysis (PCA), and Bayesian clustering were estimated. The F ST highlighted genetic differentiation between taurine and zebu breeds. The taurine lines, Caracu and Caracu Caldeano, had significant genetic differentiation (F ST close to 5%) despite their recent selection for different uses (meat and milk). This genetic variability can be used for conservation of locally adapted animals, as well as for breeding programs on zebu breeds. Introgression of zebu in locally adapted breeds was identified, especially in Curraleiro Pé-Duro breed. The Gyr breed, however, had low breed purity at genomic level due to its very heterogeneous mixing pattern.

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.

Population genetic structure in the Holstein breed in Brazil.

We evaluated the population genetic structure of the Holstein breed in Brazil through pedigree analysis with the aim of supporting genetic management of extant herds. We used data from genealogical records of 204,511 animals in farms from south and southeast Brazil. Pedigree records between 1943 and 2005 were divided into seven periods of 8 years to estimate the effective population size (N e ). N e varied during the study periods, ranging from 0.19 to 3016.25. There was an increase in the percentage of inbred animals over time, from 0.18 to 5.0 %. However, this figure may be an underestimate due to the low completeness of pedigree, primarily related to paternal pedigree. The effective number of founders (fe) was 473 animals and ancestors (fa) was 471. The genetic contribution of 260 ancestors (founders or not) accounted for 50 % of the genetic variability in the population. The average relatedness coefficient (AR) and inbreeding coefficient indicate that the Holstein breed in Brazil is being effectively managed, despite a moderate founder effect and the low number of animals that are responsible for the population variance.

Inbreeding depression on production and reproduction traits of buffaloes from Brazil.

The objective of this study was to evaluate the influence of inbreeding depression on traits of buffaloes from Brazil. Specifically, the traits studied were body weight at 205 and 365 days of age, average daily gain from birth to 205 days (ADG_205), average daily gain between 205 and 365 days (ADG205_365) in Mediterranean buffaloes, and milk yield, lactation length, age of first calving and calving intervals in Murrah buffaloes. Inbreeding effects on the traits were determined by fitting four regression models (linear, quadratic, exponential and Michaelis-Menten) about the errors generated by the animal model. The linear model was only significant (P < 0.05) for growth traits (exception of ADG205_365). The exponential and Michaelis-Menten models were significant (P < 0.01) for all the studied traits while the quadratic model was not significant (P > 0.05) for any of the traits. Weight at 205 and 365 days of age decreased 0.25 kg and 0.39 kg per 1% of increase in inbreeding, respectively. The inbred animals (F = 0.25) produced less milk than non-inbred individuals: 50.4 kg of milk. Moreover, calving interval increased 0.164 days per 1% of increase in inbreeding. Interestingly, inbreeding had a positive effect on age at first calving and lactation length, decreasing age of first calving and increasing lactation length.

Interação genótipo x local x regime alimentar em bovinos nelore por meio de componentes principais de três modos

O principal objetivo deste estudo foi aplicar componentes principais com múltiplas matrizes de dados para verificar a interação tripla genótipo x local x regime alimentar no valor genético do efeito direto do peso, aos 205 dias de idade. Foram utilizados touros com filhos em três regiões de produção do Nordeste Brasileiro (Maranhão, Mata e Agreste, e Recôncavo Baiano) e criados nos regimes alimentares a pasto ou com suplementação. Não se evidenciou interação genótipo x local para a característica estudada, entretanto, constatou-se interação do genótipo x regime alimentar. A utilização dos touros deve ser direcionada de acordo com o regime alimentar de seus filhos.

The main objective of this study was to apply three-mode principal component analysis to assess the triple interaction (genotype x location x feeding) on direct genetic value for weight at 205 days of age. We used 60 sires with offspring in three regions of northeastern Brazil (Maranhão, Mata and Agreste, and Recôncavo Baiano) and raised on a pasture regime or with supplementation. There was no interaction between genotype and location, but there was a correlation between genotype and direct effect of feeding. The use of sires should be dictated according to the system of rearing of their offspring.

Genetic variability in Mediterranean buffalos evaluated by pedigree analysis / Variabilidade genética na raça bubalina Mediterrânea avaliada por meio de análise de pedigree

The objective of this research was to study the population genetic structure of four herds of Mediterranean buffaloes in Brazil. It was used pedigree data from 6,588 buffaloes of Mediterranean breed born from 1980 to 2002. Of the total number of animals studied, 60.5, 15.3 and 2.1% had a pedigree in the first, second and third ascendancy, respectively. The effective number of herds that provided breeding males was 1.60 for parents, 1.16 for grandparents and 1.00 for great-grandparents. There were 923 founder animals and only 71 effective founders. The effective number of ancestors explaining the genetic variability of the population was 71 and only 30 ancestors accounted for 50% of the genetic variability of the population. The average relatedness coefficient (AR) between individuals and inbreeding (F) of the population were estimated at 0.37 and 0.34% respectively. The average estimate of generation interval was 8.71±2.85 years. The variability of the current population is the result of a few ancestors, who are mostly also founders showing that the population was developed from a narrow genetic base which characterizes the occurrence of founder effect.

O objetivo deste trabalho foi estudar a estrutura genética populacional de bubalinos da raça Mediterrâneo, em quatros rebanhos, no Brasil. Foram utilizados dados de pedigree de 6.588 bubalinos da raça Mediterrâneo nascidos no período de 1980 a 2002. Do total de animais estudados, 60,5; 15,3 e 2,1% possuíam pedigree na primeira, segunda e terceira ascendência, respectivamente. O número efetivo de rebanhos que forneceram machos reprodutores foi de 1,60 para pais; 1,16 para avôs e 1,00 para bisavôs. O número de animais fundadores foi 923 e o número efetivo de fundadores foi apenas 71. O número efetivo de ancestrais que explicaram a variabilidade genética da população foi de 71 e somente 30 ancestrais explicaram 50% da variabilidade genética da população. Os coeficientes médios de relação (CR) entre os indivíduos da população e de endogamia (F) foram estimados em 0,37 e 0,34%, respectivamente. A estimativa média do intervalo de gerações foi de 8,71±2,85 anos. A variabilidade da população atual é fruto da contribuição de poucos ancestrais, que são, na sua maioria, também fundadores, evidenciando que a população se desenvolveu a partir de uma base genética estreita, o que caracteriza a ocorrência do efeito fundador.

Population structure and genetic variability in the Murrah dairy breed of water buffalo in Brazil accessed via pedigree analysis.

The objective of this study was to use pedigree analysis to evaluate the population structure and genetic variability in the Murrah dairy breed of water buffalo (Bubalus bubalis) in Brazil. Pedigree analysis was performed on 5,061 animals born between 1972 and 2002. The effective number of founders (fe) was 60, representing 6.32 % of the potential number of founders. The effective number of ancestors (fa) was 36 and the genetic contribution of the 17 most influent ancestors explained 50 % of the genetic variability in the population. The ratio fe/fa (effective number of founders/effective number of ancestors), which expresses the effect of population bottlenecks, was 1.66. Completeness level for the whole pedigree was 76.8, 49.2, 27.7, and 12.8 % for, respectively, the first, second, third, and fourth known parental generations. The average inbreeding values for the whole analyzed pedigree and for inbreed animals were, respectively, 1.28 and 7.64 %. The average relatedness coefficient between individuals of the population was estimated to be 2.05 %-the highest individual coefficient was 10.31 %. The actual inbreeding and average relatedness coefficient are probably higher than estimated due to low levels of pedigree completeness. Moreover, the inbreeding coefficient increased with the addition of each generation to the pedigree, indicating that incomplete pedigrees tend to underestimate the level of inbreeding. Introduction of new sires with the lowest possible average relatedness coefficient and the use of appropriate mating strategies are recommended to keep inbreeding at acceptable levels and increase the genetic variability in this economically important species, which has relatively low numbers compared to other commercial cattle breeds. The inclusion of additional parameters, such as effective number of founders, effective number of ancestors, and fe/fa ratio, provides better resolution as compared to the inclusion of inbreeding coefficient and may help breeders and farmers adopt better precautionary measures against inbreeding depression and other deleterious genetic effects.

Análise de agrupamento na seleção de modelos de regressão não-lineares para curvas de crescimento de ovinos cruzados / Cluster analysis applied to nonlinear regression models selection to growth curves of crossed lambs

Este estudo teve como objetivo utilizar a análise de agrupamento para classificar modelos de regressão não-lineares usados para descrever a curva de crescimento de ovinos cruzados, tendo em vista os resultados de diferentes avaliadores de qualidade de ajuste. Para tanto, utilizaram-se dados de peso-idade dos seguintes cruzamentos entre raças de ovinos de corte: Dorper x Morada Nova, Dorper x Rabo Largo e Dorper x Santa Inês. Após a indicação do melhor modelo, objetivou-se ainda aplicar a técnica de identidade de modelos a fim de identificar o cruzamento mais produtivo. Foram ajustados doze modelos não-lineares, cuja qualidade de ajuste foi medida pelo coeficiente de determinação ajustado, critérios de informação de Akaike e Bayesiano, erro quadrático médio de predição e coeficiente de determinação de predição. A análise de agrupamento indicou o modelo Richards como o mais adequado para descrever as curvas de crescimento dos três grupos genéticos considerados, e os testes de identidade de modelos indicaram o cruzamento Dorper x Santa Inês como sendo o mais indicado para a pecuária local.

This study had the objectives to use the cluster analysis in order to classify nonlinear regression models used to describe the growth curve in relation to different quality fit evaluators. Were utilized weight-age data from the following crossbred beef lambs Dorper x Morada Nova, Dorper x Rabo Largo e Dorper x Santa Inês. After the choice of the best model, we aimed also to apply the model identity in order to identify the most efficient crossbred group. Eleven nonlinear models were used, whose fit quality was measured by determination coefficient, Akaike information criterion, Bayesian information criterion, mean quadratic error of prediction and predicted determination coefficient. The cluster analysis indicated the Richards as the best model for the three data sets, and the model identity tests revealed that the Dorper x Santa Inês crossbred group was recommend for meat production.

History of registered Gyr breed in Brazilian Northeast: population structure and genetic improvement of growth traits / Histórico da raça Gir registrada no Nordeste brasileiro: melhoramento genético em características de crescimento e estrutura populacional

This paper provides an evaluation of the population structure, phenotype and genetic trends of registered Gyr herd cattle in northeast Brazil. The study provides important baseline information for the management, conservation and potential population expansion of this economically and culturally important cattle breed. Pedigree data were analyzed for individuals born between 1964 and 2006. Body weight values were adjusted to 205 and 365 days of age for animals born between 1978 and 2006. Phenotypic change of zebu Gyr in northeast Brazil is solely due to environmental improvement. However, there is potential for artificial selection for weight gain in young cattle. Effective population size decreased during the 1990s and the average inbreeding coefficient increased during the studied period. An increase of the effective population size of Gyr in northeast Brazil is strongly recommended, along with an increase in the management of the mating process to prevent inbreeding and to maintain the genetic variability of the breed.

Com o intuito de fornecer subsídios para programas de conservação, seleção e expansão da raça Gir no Nordeste do Brasil, objetivou-se avaliar o histórico do rebanho Gir registrado no nordeste brasileiro, com base na sua estrutura populacional e no progresso genético e fenotípico de características de desenvolvimento ponderal. Foram utilizadas informações de pedigree de animais nascidos no período de 1964 a 2006 e dados dos pesos ajustados aos 205 e 365 dias de idade de bovinos nascidos de 1978 a 2006. O progresso genético para a raça no Nordeste foi ocasionado exclusivamente pelo melhoramento ambiental. O tamanho efetivo da população reduziu a partir da década de 90, e o coeficiente de endogamia médio aumentou durante o período estudado. É imprescindível que o tamanho efetivo da raça Gir do nordeste seja ampliado e que haja maior controle de acasalamentos entre indivíduos aparentados, para prevenção da endogamia e conservação da variabilidade genética e viabilidade da raça.

A eletroestimulação nervosa transcutânea acupuntural e convencional na cefaléia tensional / Conventional and acupunctural transcutaneous electrical nerve stimulation in tension-type headaches

O presente estudo propôs-se a comparar os efeitos da TENS tipo convencional e acupuntural no alívio da cefaléia tensional. Para tanto, realizou-se um ensaio clínico randomizado com oito mulheres randomizadas em 2 grupos: grupo I, em que foi aplicado a TENS do tipo convencional (F = 100 Hz, 60 ms por 30 minutos) e grupo II submetido à aplicação da TENS acupuntural (F = 4Hz, 230 ms por 30 min). Observou-se com esse estudo que houve uma redução significativa (p < 0,01) do quadro álgico no grupo I através da escala analógica visual, assim como no grupo I e II quando avaliadas por meio da escala comportamental (p < 0,01). Entretanto, no grupo II não foi observado alteração clinica (p = 0,13), através da escala analógica visual. Percebe-se que entre os indivíduos pesquisados, a TENS convencional foi eficaz no alívio da cefaléia tensional e dos comportamentos a ela associados e a TENS acupuntural no alívio da dor apenas. No entanto, sugere-se a elaboração de estudos mais amplos e multicêntricos, a seleção das variáveis: tipo de atividade laboral, freqüência das crises, assim como a comparação de outros parâmetros para a TENS.

This study aimed at comparing the effects of conventional and acupunctural TENS to relieve tension-type headache. Were involved in this clinical trial eight women randomized into 2 groups: group I, which received conventional TENS (F = 100 Hz, 60 ms, for 30 minutes) and group II with TENS acupunctural (F = 4Hz, 230 ms, for 30 min). It was observed a significant decrease (p < 0.01) of the painful picture in Group I through the visual analogue scale, as well as in group I and II when assessed by the behavioral scale (p < 0.01 ). Meanwhile, in Group II was not observed clinical change (p = 0.13) by visual analogue scale. It was observed that the conventional TENS was effective in relief of tension-type headaches and behavior associated and TENS acupunctural to relieve only pain. However, it is suggested the development of wider and multicenter studies, the selection of variables: type of activity, frequency of crises, as well as a comparison of other parameters for TENS.

Efeito da incorporação da covariância entre os efeitos direto e materno sobre a análise para a característica dias para ganhar 160 Kg / Effect of the covariance between maternal and direct effects on the analyses for the traits days to gain 160 kg

O objetivo deste trabalho foi estudar o efeito da covariância entre os efeitos direto e materno sobre as estimativas dos parâmetros genéticos e nas predições dos valores genéticos, direto e materno, para a característica dias para ganhar 160 kg (D160) na fase pré-desmama. Os parâmetros e as predições dos valores genéticos foram estimados utilizando o aplicativo MTDFREML. O modelo 1 incluiu os efeitos genéticos direto e materno e de ambiente permanente, além do efeito fixo de grupo contemporâneo e da covariável idade da vaca ao parto, assumindo a covariância entre o efeito direto e materno (sigmaam 0); o modelo 2, considerou os mesmos efeitos do modelo 1, mas a covariância entre os efeitos direto e materno foi considerada nula (sigmaam=0). As estimativas de correlação de classificação dos animais pelos valores genético foram realizadas utilizando a correlação de Spearman. As estimativas de herdabilidade direta e materna para D160 foram respectivamente, 0,12 ± 0,01 e 0,09 ± 0,02, sob o modelo 1, e 0,12 ± 0,01 e 0,07 ± 0,02, sob o modelo 2. A correlação genética entre os efeitos direto e materno foi de -0,14 ± 0,12 (modelo 1). A inclusão da covariância entre os efeitos direto e materno nos modelos de análises não alterou a estimativa dos parâmetros genéticos e a classificação dos animais pela ordem dos valores genéticos estimados, quando se considerou toda a população. Entretanto, verificou-se que à medida que diminui a proporção de animais selecionados diminui a correspondência entre a classificação dos animais obtida pelos dois modelos.

Desempenho produtivo e reprodutivo de animais mestiços leiteiros (5/8 HVB x 3/8 Zebu) na região noroeste do Estado de São Paulo / Performance of dairy cattle (5/8 Holstein x 3/8 Zebu) in the northwest of the State of São Paulo

Com o objetivo de estudar a produção do gado mestiço (5/8 HVB e 3/8 ZEBU), na região Noroeste do Estado de São Paulo, avaliou-se os desempenhos produtivos e reprodutivos de vacas e bezerros na Estação Experimental de Zootecnia de Andradina (EEZA), em um período de sete anos, submetidas a controle leiteiro mensal, em sistema de uma ordenha diária com bezerro ao pé. Para o estudo do peso dos bezerros ao nascer e ao desmame, utilizou-se dados de 214 animais e para a produção de leite, 269 lactações de 74 vacas (2234 observações). Os dados foram analisados pelo método dos quadrados mínimos utilizando-se do programa SAS (1996). Para o peso ao nascer e ao desmame, utilizou-se um modelo contendo os efeitos fixos de sexo, mês e ano de nascimento do bezerro e a covariável idade da vaca (linear e quadrática) e o efeito aleatório de touro. Para a produção de leite, o modelo continha os efeitos fixos de mês e ano de nascimento do bezerro, idade da vaca, dias de lactação e mês do controle, e para o intervalo entre partos, o modelo continha os efeitos de vaca, mês e ano de nascimento do bezerro. Para o peso ao nascer apenas o efeito de sexo foi significativo (P<0,01), enquanto para o peso ao desmame e a produção de leite, todos os efeitos foram significativos (P<0,05), e apenas o ano de nascimento do bezerro influenciou significativamente (P<0,01) o intervalo entre partos. Os pesos médios e respectivos erros padrões para o peso ao nascer e ao desmame foram de 32,4 ± 0,6 kg e 125,7 ± 3,0 kg para os machos; 30,2 ± 0,6 kg e 117,7 ± 2,8 kg para as fêmeas, respectivamente. A média ajustada para o intervalo entre parto foi de 12,8 ± 0,7 meses e a idade a primeira cria teve média de 45,9 ± 7,1 meses e a produção média de leite ajustada para os 305 dias, foi de 1605,4 ± 128,3 kg. Apesar dos baixos índices de produtividade, o uso de animais mestiços pode ainda ser uma boa oportunidade para pequenos criadores que não dispõe de recursos para realizar grandes investimentos.