Venício José de Andrade

Effects of extender and equilibration time on post-thaw motility and membrane integrity of cryopreserved Gyr bull semen evaluated by CASA and flow cytometry

The objectives of the present study were to investigate the effects of three equilibration times (0, 2, and 4h) and two extenders (TRIS or Bioxcell) for cryopreservation of bull semen. Semen from 12 Gyr bulls was cryopreserved using an automated freezing machine. There were significant interactions between equilibration times and extenders for sperm motility and membrane integrity. The control treatment (0h equilibration) had the lowest values (P<0.05) for total (MOT) and progressive motilities (PROG), and percentage of sperm with intact plasma and acrosomal membranes (IPIA), with no significant differences between extenders. Extender TRIS had greater cryoprotective action than Bioxcell, with greater MOT, PROG, IPIA at 2 and 4h, as well as the lowest proportion of damaged plasma membrane (DPM, 72.2% vs. 85.8%) for all times. Equilibration for 4h yielded the most desirable (P<0.05) for MOT, PROG, and IPIA, and the least DPM percentage (86.5, 78.0, and 72.6% for 0, 2, and 4h, respectively). Overall, the combination of TRIS and 4h of equilibration was the most desirable semen cryopreservation method, with greatest MOT, PROG, and IPIA (TRIS-T4=26.8%; BIO-T4=18.3%) and the least DPM. In conclusion, based on objective analyses, equilibration during cryopreservation was essential for maintaining motility and integrity of sperm membranes; equilibration for 4h yielded the greatest sperm survival, independent of the extender used.

Evaluation of four mathematical functions to describe scrotal circumference maturation in Nellore bulls.

Four functions to characterize scrotal circumference (SC) growth in Nellore bulls were compared to identify which was the most suitable for biological interpretation. Nellore bulls (n = 532), born between September and December of 1992 to 1994 were used in the study. Measurements were made on fixed dates in January, April, July and October of each year. At the time of SC measurements, the ages of the bulls ranged from 200 to 1300 d. The functions used to describe the data were: Brody, SC = A (1 - B exp -kt); Logistic, SC = A/(1 + B exp -kt); Gompertz, SC = A exp(-B exp -kt) and Richards SC = A (1 + B exp -kt)m, where SC is the scrotal circumference at t days of age, A is the estimated SC at maturity, B is the integration constant established by the initial values of SC and t, k is the maturity constant, which equals the ratio between the maximum rate of growth and SC at maturity; m is the inflection point parameter for Richards function, which did not converge. The Brody, Gompertz and Logistic functions fitted the data in a similar fashion, with similar values for the statistics EMS and R2, and they reached convergence with similar computational costs. The Logistic function presented the best pattern of average prediction error, and therefore, it was selected for biological interpretation. For the Logistic function, estimated SC at maturity (A) was 37.95 cm at 72 mo of age. The maturity index (k) was .11 cm, and the inflection point (time of maximum growth) was reached at 13.09 mo of age at an average SC of 18.97 cm.

Aspectos genéticos do peso à desmama e de algumas características reprodutivas de fêmeas Nelore

Estimates of genetic parameters for weaning weight adjusted to 240 days of age (WW240), age at first calving (AFC), age at second calving (ASC) and first calving interval (FCI) in Nellore cattle using REML methodology (MTDFREML), were obtained. Heritability estimates from univariate analyses were: 0.48±0.20; 0.27±0.15; 0.14±0.16; and 0.03±0.13, for WW240, AFC, ASC and FCI, respectively. Genetic correlation estimates between AFC and ASC and AFC and FCI were 0.97, -0.92, respectively. The genetic correlation between ASC and FCI was -0.82. The genetic correlations between WW240 and AFC, ASC and FCI were -0.20, 0.00 and 1.00, respectively.

Correlações genéticas e fenotípicas entre características reprodutivas e produtivas de touros da raça Nelore

O objetivo deste trabalho foi estimar correlacoes geneticas e fenotipicas de caracteristicas reprodutivas e ponderais em 579 touros Nelore, em criacao extensiva. As caracteristicas reprodutivas estudadas foram: circunferencia escrotal, consistencia, volume e forma testiculares, comprimento dos testiculos esquerdo e direito, largura dos testiculos esquerdo e direito, motilidade e vigor espermaticos, defeitos espermaticos maiores, menores e totais e classificacao andrologica por pontos. As caracteristicas foram analisadas pelo metodo de maxima verossimilhanca restrita, com algoritmos livres de derivadas, sob modelo animal, com inclusao da matriz de numeradores dos coeficientes de parentesco entre os animais e seus ascendentes. As correlacoes geneticas entre circunferencia escrotal e as caracteristicas peso corporal, volume testicular, motilidade espermatica, vigor espermatico, defeitos espermaticos menores, defeitos espermaticos totais e classificacao andrologica por pontos foram, respectivamente, 0,72, 0,99, 0,72, 0,60, -0,67, -0,12 e 0,64. As maiores correlacoes fenotipicas encontradas entre peso e circunferencia escrotal, caracteristicas fisicas e morfologicas do semen, quando comparadas as correlacoes entre idade e as mesmas caracteristicas, sao indicativas de que o peso tem maior influencia na condicao reprodutiva. As correlacoes geneticas entre classificacao andrologica por pontos e as caracteristicas: peso, circunferencia escrotal, volume testicular, defeitos espermaticos maiores e defeitos espermaticos totais foram, respectivamente, 0,19, 0,64, 0,71, -0,47 e -0,58.

Tamanho de vacas Nelore adultas e seus efeitos no sistema de produção de gado de corte

Twenty Nellore mature cows and their calves were individually fed to determine the effects of frame size, weight and body condition on the production system efficiency. Means for different traits were: hip height (1.40±0.04m), withers height (1.40±0.03m), heart girth (1.84±0.04m), body length (1.38±0.13m), body surface area (4.60m²) and body weight (442.70±29.9kg). Phenotypic correlations between different size traits ranged from medium to high magnitude. Body surface was highly correlated to all traits measured. The body weight variation suggested that this trait should be evaluated along with other linear body measurement to determine the adequate animal body size.

Genetic parameters of libido in Brazilian Nellore bulls.

Genetic, environmental and phenotypic correlations between libido, testicular measurements, body weight and semen traits were estimated by multiple-trait-restricted maximum likelihood (MTDFREML) under animal models. Reproductive records, collected from 1992 to 1997, of 288 Nellore bulls were used. Estimates of heritability for libido unadjusted, adjusted for scrotal circumference and adjusted for body weight, were 0.34 +/- 0.10, 0.31 +/- 0.10, and 0.19 +/- 0.11, respectively. Genetic correlations between libido and body weight, scrotal circumference, testis length, testis width, testis volume and testis consistency were, respectively, 0.69, -0.43, -0.31, -0.16, 0.10, 0.87, and between libido and semen volume, sperm motility, vigor, gross motility, major, minor and total defects were, respectively, 0.71, 0.51, 0.12, 0.16, 0.31, 0.26 and 0.43. Results suggested that selection for libido would be effective and that it would lead to desirable correlated response for scrotal circumference, physical and morphological semen traits and undesirable correlated response in body weight.

Estimativas de parâmetros genéticos de características reprodutivas de touros Nelore, de dois e três anos de idade

Heritabilities and genetic correlations between performance and reproductive traits were estimated using Multiple Trait Derivative-Free Restricted Maximum Likelihood methodology in 579 pasture-raised Nelore bulls that were 19 to 39 months of age. Traits were breeding soundness evaluation (BSE), scrotal circumference (SC), testicular consistency (TC), testicular volume (TV), testicular shape (TS), length and width of right and left testicles, and semen traits including motility (Mot), vigor (Vig), major (MD) sperm defects, minor (mD) sperm defects and total (TD) sperm defects. Heritability estimates were 0.46; 0.10; 0.08; 0.16; 0.09; 0.11 and 0.10 for TC, Mot, Vig, MD, mD, TD and BSE, respectively. Genetic correlations between SC and: body weight (BW), TV, Mot, Vig, mD, TD and BSE were 0.72; 0.99; 0.72; 0.60; -0.67; -0.12 and 0.64, respectively, showing favorable associations between SC and the other traits. Genetic correlations between BSE and: BW, TV, MD and TD were 0.19; 0.71; -0.47 and -0.58, respectively. Results suggest that selection for body weight in Nelore bulls should not hamper fertility, nor should selection for reproductive traits hamper growth.

Descarte e congelabilidade do sêmen de touros de raças zebuínas e taurinas em central de inseminação artificial no Brasil

Semen characteristics from 250 Zebu and 144 European bulls were described and compared among season and species. All bulls were selected as donors and during five years were always stationed at an Artificial Insemination Center in Southeast of Brazil, where temperatures were above 19o C in both dry and rainy seasons. Contingency tables and Tukeys test were used to check associations and to compare group means, respectively. Semen from European breeds showed higher swirl, motility and concentration values than those of Zebu breeds (P<0.05). Semen volume was higher for Zebu breeds (P<0.05). There were more discarded ejaculates in the rainy season (P<0.05). A major cause for discarding ejaculates was undesirable physical characteristics for the Zebu and morphological characteristics for the European breeds (P<0.05). Semen freezing ability values for the European breeds were higher.

Produtividade e eficiência econômica de sistemas de produção de cria, recria e engorda de bovinos de corte na região sul do estado da Bahia

Economic efficiency and productivity of life-cycle cattle raising systems were studied by simulations that differed in calving rates (CR). The study was conducted on a life-cycle cattle production system (SCC) with 87% CR, and three simulated systems: -4CR with 83% CR, -2CR with 85% CR, and +2CR with 89% CR. The SCC was based on data from a life-cycle cattle system of 3,453 animals in the South of Bahia State, from January 2000 to December 2002. CR was adjusted according to energy requirement and herd composition in SCC during three years. Meat amount sold was 149, 146, 144, and 141kg/ha/year for -4CR, -2CR, SCC, and +2CR, respectively. Accumulated profit and return on invested capital were R

Efeito do creep feeding sobre o desempenho de bezerros e a eficiência reprodutiva de primíparas Nelore, em pastejo

780,695.42 and 7.8%; R