Resumo -O objetivo deste trabalho foi estimar correlações genéticas e fenotípicas entre escores visuais e características de carcaça medidas por ultrassom, para verifi car a efi cácia desses escores na determinação da musculosidade e na avaliação da carcaça. As características de carcaça medidas por ultrassom foram área de olho de lombo (AOL) e espessura de gordura subcutânea (EG), mensuradas entre a região da 12 a e 13 a costelas, bem como a espessura de gordura subcutânea na garupa (EGP8). As características de estrutura (E), precocidade (P) e musculosidade (M) foram avaliadas por meio de escores visuais. Os componentes de covariância usados para estimar as correlações genéticas e fenotípicas foram obtidos pelo método da máxima verossimilhança restrita, em uma análise multicaracterística. As estimativas de correlações genéticas entre AOL e E, P e M foram 0,54, 0,58 e 0,61, respectivamente, e indicaram que, a longo prazo, a utilização da AOL como critério de seleção poderá produzir animais com maiores escores visuais para essas características. As correlações genéticas estimadas entre as espessuras de gordura (EG e EGP8) e os escores P e M apresentaram comportamento semelhante. Entretanto, as correlações genéticas entre as espessuras de gordura (EG e EGP8) e E foram próximas de zero. As correlações fenotípicas seguiram as mesmas tendências das respectivas correlações genéticas. Essas estimativas indicam que os escores visuais são determinados, em parte, pelos mesmos conjuntos de genes que infl uenciam a AOL.Termos para indexação: componente de variância, correlação fenotípica, herdabilidade, musculosidade, parâmetro genético. Genetic correlations between visual scores and carcass traits measured by real-time ultrasound in beef cattleAbstract -The aim of this work was to evaluate the genetic and phenotypic correlations between carcass traits measured by real-time ultrasound and by visual scores, in order to verify the effectiveness of these scores in determining muscularity and carcass fat. Carcass traits measured by real-time ultrasound were longissimus muscle area (LMA) and backfat thickness (BF), obtained between the 12 th and 13 th ribs, as well as the rump fat thickness (RF). The visual scores for the traits of body structure (E), precocity (P), and muscle (M) were evaluated individually. The genetic and phenotypic parameters were estimated by multivariate analysis, using restricted maximum likelihood methodology. The estimated genetic correlations between LMA and E, P and M were 0.54, 0.58 and 0.61, respectively, indicating that, in the long term, the use of LMA as a selection criterion might produce animals with higher visual scores. Similar genetic correlations were found between both subcutaneous fat measures (BF and RF) and P and M scores. However, genetic correlations between both subcutaneous fat measures and E were close to zero. The phenotypic correlations followed the same trends of their respective genetic correlations. These estimates indicate that the visual scores and LMA are, in part, determi...

Resumo -O objetivo deste trabalho foi determinar os fatores que afetam a altura da garupa em diferentes idades, em bovinos Nelore, e estimar a herdabilidade e as correlações genéticas entre esse caractere e as características reprodutivas e de crescimento. Os caracteres avaliados foram: altura da garupa à desmama, altura da garupa ao sobreano, peso à desmama, peso ao sobreano, perímetro escrotal e idade ao primeiro parto. Os fatores considerados foram: ano e mês de nascimento, rebanho, sexo, idade da vaca ao parto e idade do bezerro. Os componentes de variância e covariância foram estimados pela metodologia de máxima verossimilhança restrita, tendo-se utilizado um modelo animal. Todos os efeitos foram significativos para altura de garupa nas diferentes idades. As estimativas de herdabilidade quanto ao efeito genético direto indicaram que as características de crescimento e reprodutivas respondem à seleção, exceto a idade ao primeiro parto. As correlações genéticas entre as características de crescimento foram todas positivas e elevadas, de 0,42 a 0,90, o que indica que são determinadas em grande parte pelos mesmos conjuntos de genes de ação aditiva. Em razão das baixas magnitudes das estimativas de correlação genética (entre -0,14 e 0,16), a eficiência reprodutiva é pouco influenciada pela seleção quanto à altura de garupa.Termos para indexação: componentes de variância, correlações genéticas, herdabilidade, idade da vaca, idade do bezerro. Hip height and its relationships with reproductive and growth traits in Nelore cattleAbstract -The objective of this work was to determine factors that affect hip height at different ages, in Nelore cattle, and to estimate the heritability and the genetic correlation between this character and reproductive and growth traits. The analyzed traits were: hip height at weaning, hip height at post weaning, weight at weaning, weight at post weaning, scrotal circumference, and age at first calving. The analyzed factors were: year and month of birth, herd, sex, age of dam at calving, and calf age. The variance covariance components were estimate by the restrict maximum likelihood methodology using animal model. All effects were significant for hip height at different ages. The heritability estimates for direct genetic effects indicated that the growth and reproductive traits respond to selection, except for age at first calving. The genetic correlations between growth traits were positive and high, from 0.42 to 0.90, which indicates that they are mostly determined by the same group of genes with additive action. Due to the low magnitude of the estimated genetic correlations, from -0.14 to 0.16, the reproductive efficiency is little influenced by selection for hip height.

The objectives of the present study were to investigate the influence of yearling weight on the occurrence of early pregnancy and to determine differences between precocious and non-precocious heifers in terms of pre-and postnatal calf mortality, calf weight and height, mature cow weight, and stayability of the cow in the herd. Data from 26 977 females of a Nelore herd that participated in the breeding season between 1986 and 2004 were analyzed. The influence of yearling weight on sexual precocity and differences between precocious and non-precocious heifers in pre-and postnatal calf mortality and stayability were analyzed using the GENMOD procedure of the SAS program. Differences in the growth traits between precocious and non-precocious animals were estimated by contrast analysis. Three groups were analyzed for postnatal mortality: first calving of the heifers, calves born from the third calving and all offspring of the cow. In order to have a standardized calving to conception period for all females (precocious and non-precocious), calves born from the second calving were not included in the analysis. This was necessary because the first calving to conception period (days open) of precocious heifers was longer than for non-precocious due to farm reproductive management. No differences in postnatal mortality rates, from the third calving, were observed between the two groups of heifers studied. Analysis of all offspring of the dams showed a 9% higher probability of death of calves born to precocious heifers compared with calves born to non-precocious heifers. With respect to stayability, precocious heifers presented 33% greater odds to remain in the herd until 5 and 6 years of age and 28% greater odds to remain in the herd until 7 years when compared with non-precocious heifers. Precocious heifers weaned calves (205 days) significantly heavier than non-precocious ones, 1.410 and 0.797 kg considering the weaning weights of all offspring and of the third calving, respectively. With respect to sexual precocity, the results suggest that the probability of heifers to become pregnant at 16 months of age increases with increasing weight. However, heifers weighing more than 240 kg present practically the same pregnancy probability. Nevertheless, exposure of heifers during the early breeding season is recommended for beef cattle herds raised in tropical regions in view of the numerous benefits demonstrated here.

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The objective of this study was to examine the relationship of DMI fluctuation, feedlot performance, feeding behavior, rumen morphometrics, and carcass characteristics in Nellore cattle classified by residual feed intake (RFI). One experiment was conducted in 2 consecutive years using individual pens (1.0 × 7.0 m) at the São Paulo State University feedlot, Dracena campus, Brazil. The experiment in year 1 started in June of 2012 with forty-eight 20-mo-old Nellore yearling bulls with an initial BW of 358.2 ± 19.4 kg. The experiment in year 2 started in January of 2013 with sixty 20-mo-old Nellore yearling bulls with an initial BW of 402.5 ± 33.0 kg. Experiments in years 1 and 2 lasted 94 and 84 d, respectively. All yearling bulls were categorized as high RFI (>0.5 SD above the mean, = 25), medium RFI (±0.5 SD from the mean, = 56), and low RFI (<0.5 SD below the mean, = 27). Visual appraisal to collect behavior data was made on d 40 (finishing period) of both years. Yearling bulls were harvested when average across treatment groups achieved a fat thickness of 4 mm at the 12th rib. Low-RFI yearling bulls had lower daily DMI, expressed either in kilograms ( < 0.01) or as percentage of BW ( < 0.01), and improved G:F ( < 0.01) when compared to high-RFI animals. No differences were observed ( > 0.10) for ADG, final BW, or HCW among RFI groups. Also, low-RFI yearling bulls had thinner final 12th rib ( < 0.01) and biceps femoris (P8) fat thickness ( < 0.01). Low-RFI yearling bulls were slower to consume ( = 0.03) and ruminate ( < 0.01) 1 kg of either DM or NDF. No significant ( > 0.10) RFI effect was observed for any ruminal morphometrics variables evaluated, with the exception of papillae area, in which low-RFI Nellore yearling bulls tended to have smaller ( = 0.07) papillae area than medium-RFI animals. In general, low-RFI Nellore yearling bulls consumed more particles larger than 19 and 8 mm and had a similar performance when compared to both medium- and high-RFI bulls; however, carcass fat composition was negatively impacted.

In the present study, the effects of restricted intake of the final finishing diet as a means of dietary adaptation compared with diets increasing in concentrate content (step-up) over periods of 14 and 21 days on growth performance, carcass characteristics, feeding behaviour and rumen morphometrics of Nellore cattle were evaluated. One hundred and twenty 20 months old Nellore bulls (initial BW = 372.2 kg, s.d. = 21.5 kg) were randomly allocated in 24 pens (n = 5 per pen) and fed for 84 days. The study had a completely randomised design with a 2 × 2 factorial arrangement: adaptation using both 14-day and 21-day step-up and restriction protocols. Each treatment was replicated 6 times. One bull per pen was slaughtered (n = 24) at the end of adaptation period to evaluate rumen morphometrics. The remaining bulls (n = 96) were slaughtered at the end of experimental period. Interactions were observed (P &lt; 0.05) for growth performance, feeding behaviour and rumen morphometrics variables. Overall, no protocol or adaptation length main effect (P &gt; 0.05) was observed for any of the growth rate and carcass traits evaluated, except for hot carcass weight (P = 0.03) and dressing percentage (P = 0.04), where bulls adapted for 14 days had heavier carcasses and increased dressing percentage when compared with cattle adapted for 21 days. Cattle adapted for 21 days had a larger (P = 0.005) rumen wall absorptive surface area at the end of adaptation period than those adapted for 14 days; however, no differences were detected at the end of finishing period. Thus, Nellore yearling bulls could be adapted for 14 days regardless of the protocol.

This work aimed to survey management practices used by dairy farmers and to report nutritional recommendations adopted by 43 dairy cattle nutritionists in Brazil. The web-based survey consisted of 80 questions. Almost 50% of the participants had clients that produce <1000 kg of milk daily and 48.8% had clients who own fewer than 100 dairy cows. Corn was the primary source of grain (97.4%), and 43.9% of the nutritionists included from 41% to 50% concentrate in lactation diets. The mean roughage inclusion in lactation diets was 50.5% and 79% of the nutritionists reported corn silage as the primary roughage source. Average crude protein and rumen-degradable protein concentrations recommended by the nutritionists for lactation diets were 15.7% and 9%, respectively. Average Ca and P concentrations recommended for lactation diets were 0.70% and 0.41%, respectively. The major health problem reported by 83.9% of the nutritionists was mastitis. The present survey provides an overview of management practices adopted by dairy farmers and nutritional recommendations currently applied by dairy cattle nutritionists in Brazil. The most critical points identified were low milk yield, mastitis as the major health problem, lack of proper mixing and delivery of rations, and destination of male calves.

Foram analisados 13.406 registros de lactação de 7.153 vacas Gir Leiteiro com partos ocorridos de 1960 a 2008 com o objetivo de estimar ganhos ou perdas econômicas e em produção de leite atribuídos à variação no intervalo de partos (IP). Foi observada produção de leite média por vaca por lactação de 2.846,95 ± 1.339,72 kg e média de IP de 449,86 ± 51,54 dias. A redução do IP observado para 365 dias levaria a aumento na produção de leite de 558,16 kg. Os resultados econômicos decorrentes das perdas nas produções de leite e de bezerros foram de R$ 467,34/vaca/ lactação. Os gastos com ração e mão de obra foram de R$ 198,22. A perda econômica total foi de R$ 269,12/vaca/lactação. O aumento no IP tem resultado em perdas produtivas e econômicas nos rebanhos estudados.Palavras-chave: Gir leiteiro, intervalo de partos, perdas econômicas, produção de leite.