ABSTRACT The objective of this work is to estimate genetic parameters and breeding values to improve embryo and oocyte production, using repeatability and random regression models (RRM) for Gir dairy cattle. We used 11,398 records of ovum pick-up from 1,747 dairy Gir donors and evaluated sixteen different models: the traditional repeatability model and fifteen RRM, each of which considered a different combination of Legendre polynomial regressors to describe the additive genetic and permanent environment effects. The 4G1P model (four regressors for the genetic effect and one regressor for the permanent environment effect) is the most suitable model to analyze the number of viable and total oocytes, while the 3G1P is the best model to analyze the number of cleaved and viable embryos, according to the values of the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). The heritability estimated with the RRM was higher than that estimated with the repeatability model. The high repeatability reported for oocyte and embryo count traits indicates that donors, which had high oocyte and embryo counts in the first ovum pick-up, should maintain this result in the next ovum pick-up. Genetic correlations between adjacent ages were high and positive, while genetic correlations between extreme ages were weak. We observed a reranking of the top sires and females (heifers and cows) over the period evaluated. The reliability of the estimated breeding values by RRM showed changes across age, and the expected genetic gains by RRM are larger. This shows that RRM is most suitable alternative for the evaluation and selection of oocyte and embryo count traits.

ABSTRACT. The purpose of the present study was to evaluate the principal component analysis (PCA) to guide technical assistance regarding several dairy farms’ issues, which includes improving microbiological quality and physical-chemical composition of raw refrigerated milk. Data of monthly analysis of fat, protein, lactose, dry defatted stratum, somatic cell count, total bacterial count, milk temperature of 8,101 samples of milk from expansion tanks and production of 78 farms located in the northern region of Minas Gerais, Brazil were processed. Descriptive statistical measures and Pearson correlation coefficient were estimated involving all evaluated traits during the dry and rainy seasons. In addition, multivariate analyses were performed using PCA. The results showed that two farm sites were negatively related to milk quality in both seasons. One farm stood out positively, being able to be used as a herd management model to drive technical assistance actions. Thus, PCA is efficient in simplifying large amounts of data, allowing simpler and faster technical herd management interpretation.

ABSTRACT This study aimed to evaluate associations among final weight (FW), average daily gain (ADG), scrotal circumference (SC), and visual score (VS) of beef cattle in performance tests on pasture or in feedlots. Genetic parameters for FW, ADG, SC, and VS of young Nellore bulls performance-tested on pasture or in feedlots were evaluated by mixed model. The performance test and final age were considered as fixed effects and additive genetic and residual effects were considered as random effects. Additive genetic and residual variances for final weight and average daily gain were smaller on pasture than in feedlots. There was no difference between genetic and residual variances and heritability for scrotal circumference on pasture or in feedlots. Genetic variance and heritability for visual score on pasture were smaller than those in feedlots. The posterior means (and highest posterior density intervals with 90% of samples (HPD90) in parentheses) for heritability were 0.46 (0.42; 0.50) and 0.49 (0.41; 0.55) for FW, 0.25 (0.22; 0.29) and 0.25 (0.19; 0.30) for ADG, 0.56 (0.51; 0.61) and 0.60 (0.51; 0.68) for SC, and 0.31 (0.27; 0.34) and 0.42 (0.36; 0.48) for VS on pasture or in feedlots, respectively. The genetic correlations (posterior means with HPD90 in parentheses) were 0.74 (0.69; 0.79) and 0.67 (0.58; 0.77) between FW and ADG; 0.49 (0.43; 0.55) and 0.60 (0.53; 0.68) for FW and SC; 0.79 (0.75; 0.83) and 0.85 (0.80; 0.90) for FW and VS; 0.37 (0.29; 0.46) and 0.34 (0.19; 0.50) for ADG and SC; 0.65 (0.59; 0.71) and 0.74 (0.64; 0.84) for ADG and VS; and 0.46 (0.39; 0.52) and 0.53 (0.44; 0.62) for SC and VS, obtained on pasture or in feedlots, respectively. The genetic and residual (co)variances of growth, scrotal circumference, and visual score of beef cattle vary across environments; however, genetic and residual correlation and efficiency of correlated response among these traits remain constant on pasture or in feedlots.

RESUMO Objetivou-se avaliar, por meio de regressão logística, a relação entre composição físico-química do leite in natura e probabilidade de ocorrência de mastite em fêmeas mestiças Holandês, Gir e Jersey. O resultado do teste de CMT (positivo=1 e negativo=0) foi utilizado para estudo da probabilidade de ocorrência de mastite que foi modelada por meio de regressão logística. O modelo final composto por teor de gordura, lactose e contagem de células somáticas (CCS) foi escolhido por meio do procedimento Stepwise, disponível em SAS®, a partir das variáveis regressoras fazenda, teores de proteína, extrato seco desengordurado (ESD), gordura, lactose, e CCS. Observou-se que 53,86% dos animais apresentaram mastite subclínica. As variáveis CCS e teores de gordura e lactose influenciaram a probabilidade de ocorrência de mastite e incrementos de uma unidade de CCS, gordura e lactose possibilitam aumento de 0,4% e 52,8% e redução de 96,5%, respectivamente na probabilidade de ocorrência de mastite. A contagem de célula somática é a variável de maior impacto sendo que 600.000 células/mL resulta em 28% de probabilidade de ocorrência de mastite. O modelo de regressão logística permitiu quantificar o impacto da presença de mastite no rebanho e a composição físico-química do leite in natura.

SUMMARY This study aimed to evaluation, through logistic regression model, the relationship between physical-chemistry composition of bovine milk in natura and probability of occurrence of mastitis in crossbred female cattle from Hostein, Gyr and Jersey breed. The result of the CMT (positive =1 and negative = 0) was used to study the probability of occurrence of mastitis that was modeled using logistic regression. The final model consists of fat, lactose and somatic cell count (SCC) was selected by the Stepwise procedure available in SAS®, from the regressive variables farm, protein, degreased dry extract, fat, lactose, and SCC. It was observed that 53.86% of the animals had subclinical mastitis. The CCS, fat and lactose influenced the probability of incidence of mastitis and an increase in one unit of these variables is associated with an increase of 0.4% and 52.8% and reduction of 96.5%, respectively in the probability of incidence of mastitis. The CCS is the variable with the greatest impact on probability of mastitis, and the count of 600.000 cells/mL result in the 28% of probability of incidence of mastitis. The logistic regression model to quantify the impact from mastitis in the physical-chemistry composition of milk in natura in the dairy herd.

ResumoObjetivou-se avaliar as características produtivas e reprodutivas de fêmeas 1/2 Holandês x ¼ Nelore, ¼ Gir (Nelogir). Avaliou-se os efeitos de ordem e época de parto, do reprodutor da raça Gir e do reprodutor da raça Holandesa, avô materno e pais das matrizes 1/2 Holandês x Nelogir, respectivamente. A produção de leite total, com duração da lactação média de 288 dias, foi de 3.426,9kg de leite. A ordem de parto influenciou a produção média diária que foi maior no segundo parto e a duração da lactação, superior nos animais de primeiro parto. O período de início das águas apresentou menor duração da lactação e produção por dia de intervalo de parto. A produção de leite total não variou de acordo com o reprodutor Gir, pai da Nelogir, e foi superior nas matrizes filhas de reprodutores Holandeses com PTA positivo para leite. Ao primeiro parto o pico de produção foi de 13,03kg aos 45 dias de lactação, e a partir do segundo parto a produção foi decrescente desde o parto. Conclui-se que, em condições tropicais, as características produtivas e reprodutivas sustentam a iniciativa de produção de animais 1/2 Holandês x Nelogir a partir de matrizes compostas Nelogir e que a escolha do touro da raça Holandesa para produção de F1 HNG deve ser baseada no valor genético aditivo para produção de leite (PTA leite).

AbstractIt was aimed to evaluate the productive and reproductive traits of 1/2 Holstein x ¼ Nellore, ¼ Gir (Nelogir) females. They were evaluated the effects of order and season of calving, of Gir and Holstein sires grandfathers and fathers of the1/2 Holstein x Nelogir matrices, respectively. Total milk production, with average lactation length of 288 days, was 3,426.9kg of milk. The order of calving influenced the daily average production which was higher in the second calving and lactation length was superior in the first calving. The beginning of rain period (November to January) showed lower lactation length and production a day of calving interval. Total milk production did not vary according to Gir sire, Nelogir’s father, and was higher in the matrices daughters of Holstein sires with positive PTA for milk. In the first calving the production peak was of 13.03kg at 45 days of lactation, and from the second calving the production was descending one. In tropical conditions, productive and reproductive traits support the initiative of farm animals 1/2 Holstein x Nelogir from matrices composed Nelogir and that the choice of Holstein bull to produce F1 HNG should be based on the genetic value milk production (milk PTA).

The objective of this study was to estimate genetic parameters and to evaluate the effects of inbreeding on productive and reproductive traits of dairy Gyr cattle. Single-trait animal models were used to estimate genetic parameters and solutions for inbreeding coefficients for milk (milk 305-d), fat (fat 305-d), protein (protein 305-d), lactose (lactose 305-d), and total solids (TS 305-d) yield up to 305 days of lactation, days in milk (DIM), age at first calving (AFC) and calving intervals (CI). The mean inbreeding coefficient was 2.82%. The models with linear and quadratic effects of inbreeding coefficients fitted the data better than the models without or with only linear effect of inbreeding coefficient for all traits. The increase in inbreeding coefficient caused several losses in productive and reproductive traits of dairy Gyr cattle. Estimates of heritability for milk 305-d, fat 305-d, protein 305-d, lactose 305-d, TS 305-d, DIM, AFC, and CI were 0.28, 0.27, 0.22, 0.21, 0.22, 0.17, 0.20, and 0.10, respectively. It is possible to achieve genetic progress in productive traits (especially in milk 305-d and fat 305-d) and age at first calving in dairy Gyr cattle through selection.