Genetic evaluation of the probability of pregnancy at 14 months for Nellore heifers

To estimate the heritability for the probability that yearling heifers would become pregnant, we analyzed the records of 11,487 Nellore animals that participated in breeding seasons at three farms in the Brazilian states of São Paulo and Mato Grosso do Sul. All heifers were exposed to a bull at the age of about 14 mo. The probability of pregnancy was analyzed as a categorical trait, with a value of 1 (success) assigned to heifers that were diagnosed pregnant by rectal palpation about 60 d after the end of the breeding season of 90 d and a value of 0 (failure) assigned to those that were not pregnant at that time. The estimate of heritability, obtained by Method 9, was 0.57 with standard error of 0.01. The EPD was predicted using a maximum a posteriori threshold method and was expressed as deviations from 50% probability. The range in EPD was -24.50 to 24.55%, with a mean of 0.78% and a SD of 7.46%. We conclude that EPD for probability of pregnancy can be used to select heifers with a higher probability of being fertile. However, it is mainly recommended for the selection of bulls for the production of precocious daughters because the accuracy of prediction is higher for bulls, depending on their number of daughters.

Study of stayability in Nellore cows using a threshold model

The objectives of the current study were to assess the feasibility of using stayability traits to improve fertility of Nellore cows and to examine the genetic relationship among the stayabilities at different ages. Stayability was defined as whether a cow calved every year up to the age of 5 (Stay5), 6 (Stay6), or 7 (Stay7) yr of age or more, given that she was provided the opportunity to breed. Data were analyzed based on a maximum a posteriori probit threshold model to predict breeding values on the liability scale, whereas the Gibbs sampler was used to estimate variance components. The EBV were obtained using all animals included in the pedigree or bulls with at least 10 daughters with stayability observations, and average genetic trends were obtained in the liability and transformed to the probability scale. Additional analyses were performed to study the genetic relationship among stayability traits, which were compared by contrasting results in terms of EBV and the average genetic superiority as a function of the selected proportion of sires. Heritability estimates and SD were 0.25 +/- 0.02, 0.22 +/- 0.03, and 0.28 +/- 0.03 for Stay5, Stay6, and Stay7, respectively. Average genetic trends, by year, were 0.51 +/- 0.34, and 0.38% for Stay5, Stay6, and Stay7, respectively. Estimates of EBV SD, in the probability scale, for all animals included in the pedigree and for bulls with at least 10 daughters with stayability observations were 7.98 and 12.95, 6.93 and 11.38, and 8.24 and 14.30% for Stay5, Stay6, and Stay7, respectively. A reduction in the average genetic superiorities in Stay7 would be expected if the selection were based on Stay5 or Stay6. Nonetheless, the reduction in EPD, depending on selection intensity, is on average 0.74 and 1.55%, respectively. Regressions of the sires' EBV for Stay5 and Stay6 on the sires' EBV for Stay7 confirmed these results. The heritability and genetic trend estimates for all stayability traits indicate that it is possible to improve fertility with selection based on a threshold analysis of stayability. The SD of EBV for stayability traits show that there is adequate genetic variability among animals to justify inclusion of stayability as a selection criterion. The potential linear relationship among stayability traits indicates that selection for improved female traits would be more effective by having predictions on the Stay5 trait.

Structural organization in leaf blade and sheath of elephant-grass cultivars (Pennisetum purpureum Schum. - POACEAE).

Elephant-grass is known as a great feed to dairy and beef cattle at tropical regions. Its agricultural aspects have been very observed. However, its botanical, mainly anatomical characteristics, are few studied. The objective of this work was to investigate the anatomical changes occurred in leaves (leaf blades and sheaths) of three elephant-grass cultivars (Pennisetum purpureum Schum. cultivar Roxo, EMPASC 307 Testo and EMPASC 309 Areia) at three stages of physiological maturity (4, 8 and 16 weeks after sprouting). In general, the three cultivars presented similar anatomy. A unique feature, the presence of aerenchyma was found in the leaf sheath of all three cultivars, at the second harvest (a weeks).

Estimativas de (Co)Variâncias e Tendências Genéticas para Pesos em um Rebanho Canchim

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Intestinal starch disappearance increased in steers abomasally infused with starch and protein

Steers (379 +/- 10 kg) with ruminal, duodenal, and ileal cannulas were used in a 5 x 5 Latin square digestion trial to quantify and evaluate the relationship between intestinal protein supply and intestinal starch disappearance. Treatments were infusions of 0, 50, 100, 150, or 200 g/d of casein along with 1,042 g/d of raw cornstarch. Abomasal infusions were accomplished by passing tubing and a pliable retaining washer through the reticular-omasal orifice into the abomasum. Steers were fed a 93% corn silage, 7% supplement diet that contained 12% crude protein at 1.65% body weight in 12 equal portions/d. Periods lasted 17 d (12 d for adaptation, 2 d of collections, and 3 d of rest). The quantity and percentage of organic matter and protein disappearance from the small intestine increased linearly (P < 0.03) with infused casein. Greater quantities of starch disappeared with increased casein infusion (P < 0.01). The infusion of 200 g/d of casein increased small intestinal starch disappearance by 226 g/d over the control. Casein infusion did not affect the quantity or percent of organic matter, starch, or protein disappearance in the large intestine. Treatments did not change ruminal ammonia N, ruminal pH, or plasma glucose concentrations. Starch disappearance from the small intestine was increased with greater protein flow to the duodenum of steers.

Efeito da ovariectomia em novilhas Nelore x Angus, Bos taurus indicus x Bos taurus taurus sobre os ganhos de peso

This study aimed to evaluate the weight gain in cross breed heifers Nelore X Angus, spayed and nonspayed, kept on pasture and confinement. The animals were allotted in two groups as follows: group I consisted of 30 nonspayed heifers with 18 months old. Group 2 was composed of 30 spayed heifers with 18 months old. The animals were allotted in pasture of Brachiaria decumbens and weighted at 39 and 75 days. Significant difference was observed between the average daily gain of the two groups - G1 and G2 (75(th) day), respectively (0.51 kg and 0.65 kg; P<0.0 1). The following day (761 day), all animals were allotted and kept on confinement during 144 days. Significant difference was observed between the average daily gain of the two groups - G I and G2 (1441 day), respectively (0.73 kg and 0.58 kg; P<0.0 1). The results of this experiment show that spayed heifers presented a higher daily gain on pasture.

Estimativas de parâmetros genéticos para características de crescimento e produtividade em vacas da raça Canchim, utilizando-se inferência bayesiana

The objective of this study was to estimate genetic parameters for body weights at weaning (PD), 12 months old (P12) and adult age (PAD), culling age (TPR, days in herd), number (ND10) and kilograms (QD10) of calves weaned up to ten years of age, total number (NDT) and total kilograms (QDT) of calves weaned during herd life, and kilograms of calves weaned per year in herd (QTPR) of Canchim (5/8 Charolais + 3/8 Zebu) females from one herd. Data consisted of 3,249, 3.111, 1,138, 1,340, 1,362, 1,362, 1,340, 1,340 and 1,340 records of PD, P12, PAD, TPR, ND10, QD10, NDT, QDT and QTPR. respectively. Variance and covariance components were estimated by bivariate analyses between PD, P12 and PAD and other production traits using Bayesian inference. The models included the additive direct, permanent environmental and residual random effects and the fixed effects year and month of birth or calving, calving age and age of the animal, depending on the trait. QD10, QDT and QTPR of each female were obtained by adjusting the weaning weights of calves for year and month of birth, sex and age of cow. Average of heritability estimates were 0.38 (PD), 0.40 (P12), 0.54 (PAD), 0.22 (TPR), 0.22 (ND10), 0.24 (QD10), 0.23 (NDT), 0.23 (QDT) and 0.32 (QTPR), indicating genetic variability to obtain response by selection. Genetic correlations between TPR (-0.02, 0.26 and -0.12), ND10 (0.04, 0.10 and -0.29), QD10 (0.37, 0.39 and -0.13), NDT (-0.03, 0.14 and -0.25), QDT (0.20, 0.33 and -0.16), QTPR (0.21, 0.28 and -0.19) and body weights (PD, P12 and PAD) suggest that selection of females based on weaning and 12-month body weights will not affect productivity. However, it may be decreased by increasing female adult body weight.

Herdabilidades e Correlações Genéticas para Peso e Perímetro Escrotal de Machos e Características Reprodutivas e de Crescimento de Fêmeas, na Raça Canchim

The objective of this study was to estimate heritabilities of and genetic correlations among male body weight (BW12) and scrotal circumference (SC12) at 12 months of age, and female body weights at first (BWFC) and second (BWSC) calvings, age at first (AFC) and second (ASC) calvings, adult weight (AW), and mature weight (A) and maturation rate (k) obtained by the use of the Von Bertalanffy model. The restricted maximum likelihood method with an animal model that included the fixed effects of contemporary group and the random effects of animals, was used to estimate the variance and covariance components. The heritability estimates were equal to: 0.37 (BW12),0.30 (SC12),0.38 (A), 0.35 (k), 0.12 (AFC), 0.33 (BWFC), 0.04 (ASC), 0.39 (BWSC), and 0.38 (AW). The genetic correlations among BW12 and the female traits were: 0.19 (parameter A), 0.62 (parameter k), -0.58 (AFC), 0.69 (BWFC), -0.56 (ASC), 0.61 (BWSC), and 0.60 (AW). The genetic correlations among SC12 and the female traits were: -0.24 (A), 0.27 (k), -0.47 (AFC), 0.09 (BWFC), -0.67 (ASC), 0.07 (BWSC), and -0.17 (AW). These results indicate that male body weight and scrotal circumference and female weights (BWFC, BWSC and AW) and growth curve parameters A and k have enough additive genetic variation to respond to mass selection. Selection to increase male body weight at 12 months of age should result on favorable correlated changes in AFC, ASC and parameter k of females, but with increases in female body weights (BWFC, BWSC and AW). Selection to increase SC12 should result on desirable correlated responses in AFC, ASC and k, without any considerable change in female adult body weights.

Stem anatomy of Pennisetum purpureum schum. (Poaceae) cultivars

Elephant-grass is known like a great feed to dairy and beef cattle al tropical regions. Its agricultural aspects have been very observed. However, its botanical, mainly anatomical characteristics are few studied. The objective of this work was to investigate the anatomical changes occurred in stems of three elephant-grass cultivars (ROXO, EMPASC 307 TESTO and EMPASC 309 AREIA) at three stages of plant development (4, 8 and 16 weeks after sprouting). The anatomical features were similar among cultivars. When stems were young (4 weeks), a disorganization of vascular bundles were detected. However, at 8 weeks stage the were organized as a definitive form. Was observed a magnified of lignification as the stems age, mainly caused by the increased of bundles sheaths that surrounds all vascular bundles.

Tendência genética em pesos e ganhos em peso de bovinos da raça Guzerá

The main objective of this study was to estimate genetic and phenotypic trends in weights at birth (BW), 8 (W8) and 12 months (W12) of age; and also in the daily gains from birth to 8 months (G8) and from birth to 12 months (G12) for the ''Guzera'' cattle herd from the ''Fazenda de Ensino e Pesquisa do Campus de Ilha Solteira'', UNESP, at Selviria, MS, in the Central-West region of Brazil. The data were collected between 1979 and 1984 from 842 calves, sired by 22 sires. Genetic trends were estimated by three alternative procedures, two of them were based on the methodology of repeated use of sires and the other procedure on the differences in the average genetic values of sires in the different years. The phenotypic annual changes estimated were -0.232 kg, -8.278 kg, -0.033 kg, -8.498 kg e -0.023 kg, for BW, W8, G8, W12 and G12, respectively. The estimates of genetic trends, obtained by the three procedures were different, but showed that genetic changes for all analised traits were little.

Avaliação de um Sistema de Produção de Gado de Corte. 1. Desempenho Reprodutivo

Data from 1983 through 1991 on reproductive performance, collected from the Beef Cattle production system at Embrapa Gado do Corte, were analyzed. This system, based on exclusive grazing, presented a pregnancy rate (2-3 years old heifers and cows) of 75.9%. The others observed index were first calving reconception rate, 62.1%, total herd loss rate, 2.2%, and calf loss rate until weaning, 6.0%. The calf loss rate represented 53.7% of the total herd loss rate. For calf loss rate (CLR) data analysis, the used model included the effects of sex (S), calf birth year (ANB), cow birth year (ANV) and the interactions between S x ANB and ANV x ANB. Sex had a significant effect on CLR, with 8.1 and 3.8% for male and female loss rate, respectively. For calving interval analysis, the used model included the following fixed effects: ANV, birth month of cow (MNV), birth cow order when it was a calf (OPV) and the ANV x MNV interaction. The 205-day cow weight and her age at first calving were used as covariables. The calving interval was 463.45 days (15.2 mo), ranging from 388 to 543 days, and it was significantly affected by ANV. It is suggested that more research attention should be directed to the highest loss rate observed for male calves, which represent higher commercial value than females.

A novel technique to produce polygenic resistance to anthracnose in Stylosanthes capitata

An improved cultivar, based on 17 genotypes of S. capitata and six of S.macrocephala, was developed at the wEmbrapa Beef Cattle Research Center, Campo Grande, Brazil. The aim was to create durable, race non-specific resistance to anthracnose controlled by polygenic factors. A mass hybridisation technique was employed to produce a high degree of genetic diversity and sizeable quantities of seed of hybrid-derived progenies of Brazilian and Venezuelan genotypes of S. capitata. Outcrossing resulted in a significant improvement in the forage production of progeny of Venezuelan accessions. The multicross was evaluated in multilocational trials, each representing a large tract of country in the Cerrados ecosystem along a north-south transect from lat.6degrees S to 20degrees S. The genetic shift that occurred in S. capitata was a key element in the formation of the new cultivar. It is a complex mixture of two species, and a recombination of much desired forage traits of Brazilian x Venezuelan genotypes, high forage and seed yields coupled with anthracnose resistance. The new cultivar with its diverse genetic make-up has a wide application in the acid-soil savannas of tropical America. It was released by Embrapa for the Cerrados in 2000.

Estudo da interação genótipo × ambiente sobre características de crescimento de bovinos de corte utilizando-se inferência bayesiana

The objective of this study was to evaluate the genotype x environment interaction for weaning and yearling weights, daily weight gain from weaning to 12 months of age and the growth performance in Canchim (5/8 Charolais + 3/8 Zebu) beef cattle estimated by a principal components analysis including those three traits. The environment was defined by season of birth (first and second semesters of the year). Genetic parameters were estimated by bayesian method with the Gibbs sampler using bivariate analyses (considering the trait in each of the two seasons as a different one) and models that included the fixed effects of year and month of birth, sex and age of cow (linear and quadratic) and the random effects of animal and residual. The results suggested that genetic evaluation and selection in Canchim beef cattle for the traits studied should consider the genotype and season of birth interaction.

New Stylosanthes guianensis for tropical grasslands

Hybrid stylos (Stylosanthes guianensis var. vulgaris x var. pauciflora) with durable, quantitative resistance to anthracnose, mid-season harvest maturity date (early-July), high DM and seed yields have been selected at the Embrapa Beef Cattle Research Center, Campo Grande, Brazil. The hybrids displayed improved forage traits in Brazil, the native habitat and major center of diversity of the species and its pathogen, as well as in vastly different ecosystems. Dry forage yields and anthracnose resistance of superior selections and their composites were equal, in some instances, significantly better, than those of cv. Mineir (a) over tildeo in multilocational trials situated in the Cerrados from lat. 6degrees S to lat. 20degrees S. Selected hybrids performed well in comparison with the highly successful CIAT 184 (cv.Reyan II) on Hainan Island, China. Composites have also shown good promise in seed multiplication plots in Queensland, Australia. A positive attribute of composite hybrids is their great genetic diversity in contrast to pure-line cultivars with a relatively narrow genetic base. These truly tropical forms of stylo are best adapted to regions with >1500mm average annual rainfall.