Leopoldo Andrade de Figueiredo

Análise de fatores genéticos e ambientais que afetam a infestação de fêmeas bovinas da raça Caracu por carrapatos (Boophilus microplus)

The objective of this study was to evaluate environmental aspects that affect the infestation of the Caracu cattle breed by the cattle tick Boophilus microplus (Canestrini, 1887) and to estimate genetic parameters for the level of this infestation. Countings of the parasite were done on female cattle from two herds, during all four seasons of the year, in two consecutive years (from September 1998 through July 2000). The number of ticks (NC) on one side of the animal was counted, and the infestations were also evaluated by scores (EC), according to the estimated number of parasites on the animal. Each animal had from one to eight observations. A total of 4,079 and 3,994 observations were obtained for NC and EC, respectively. The data were analyzed by the least squares method with a model that included the effects of herd (H), color of the animal (C), H x C, animal within H x C as error a, year, season, thickness of the hair, and age of animal as a covariable (linear and quadratic effects). The variance and covariance components were estimated by the restricted maximum likelihood derivative free method, using a model that included the effects of contemporary group (herd - year - season), hair thickness and age of the animal as a covariable (linear and quadratic effects), and the random additive direct and permanent environmental effects. Before the analyses, NC was transformed to log10 (n + 1) and EC was transformed to (x + 0.5) 1/2, where n is the number of ticks counted on the animal and x is the score for EC (0 to 4). The incidence of ticks was higher during the summer, and the ticker the hair the higher the infestation. The heritability and repeatability estimates were equal to 0.22 and 0.29, and 0.15 and 0.21 for NC and EC, respectively, and the genetic correlation between NC and EC was 1.00. The results indicate that there is enough additive genetic variation on tick numbers to support a selection program to increase resistance.

k -Casein, b -lactoglobulin and growth hormone allele frequencies and genetic distances in Nelore, Gyr, Guzerá, Caracu, Charolais, Canchim and Santa Gertrudis cattle

The genotypes for k-casein (k-CN), b-lactoglobulin (b-LG) and growth hormone (GH) were determined by polymerase chain reaction (PCR) and restriction enzyme digestion in seven breeds of cattle (Nelore, Gyr, Guzera, Caracu, Charolais, Canchim and Santa Gertrudis). k-Casein had two alleles with the A allele occurring at a higher frequency in Bos indicus breeds (0.93, 0.92 and 0.91% for Gyr, Guzera and Nelore, respectively). The b-lactoglobulin locus had two alleles in all of the breeds. European breeds had a higher frequency of the b-LG A allele than Zebu breeds. The GH locus had two alleles (L and V) in Bos taurus and was monomorphic (L allele only) in all of the Bos indicus breeds evaluated. The highest frequency for the V allele was observed in Charolais cattle. The markers used revealed a considerable similarity among breeds, with two main groups being discernible. One group consisted of Zebu and Santa Gertrudis breeds and the other consisted of European and Canchim breeds.

Estimativas de tendências e parâmetros genéticos do peso padronizado aos 378 dias de idade, medidas corporais e perímetro escrotal de machos Nelore de Sertãozinho, SP

The objectives of this study were to estimate the genetic trends and also the genetic and phenotypic parameters for body weight at 378 days (W378), body measurements and scrotal circumferences of Nellore males from selected and control populations of the Estacao Experimental de Zootecnia de Sertaozinho (SP), Brazil. The heritability estimates, considering sire and animal model were, respectively, 0.53± 0.12 and 0.36 for W378 days; 0.38±0.11 and 0.58 for hip height; 0.31±0.10 and 0.10 for chest girth; 0.40± 0.11 and 0.13 for body length; 0.39± 0.11 and 0.30 for dorsal line length; 0.33± 0.10 and 0.12 for rump length; 0.08 ± 0.07 and 0.14 for distance between pin bones; 0.23± 0.09 and 0.08 for distance between hip bones and 0.57± 0.13 and 0.44 for scrotal circumference. The highest genetic correlation between W378 and body measurements was found for chest girth (0.86 ± 0.08), and the others ranged from 0.46 to 0.72. Based on the median to high heritability values found for the majority of traits, it is expected to exist a good amount of additive genetic variability controlling their variation. In addition, due to the highest correlation between W378 and most of the traits, it is probable that most part of the genes that control post-weaning weight might control the growth of different regions of animal body. The good values for the genetic correlation and heritability explain the positive genetic trends for direct and secondary traits in the selection for W378.

Efeitos da seleção para peso pós-desmame sobre medidas corporais e perímetro escrotal de machos Nelore de Sertãozinho (SP)

The objective of this study was to evaluate the indirect effects of selection for post-weaning weight on body measures and scrotal perimeter of 809 Nellore males from selected herds (NeS and NeT) and control herd (NeC), of the Estacao Experimental de Zootecnia de Sertaozinho. The statistical analyses were performed by using a sire mixed model where the random source of variation, sires, was nested within herds. The fixed effects were herds, year of performance test (PGP), age of cow and age of the animal as a covariate. The average genetic change for final weight, corrected for 378 days of age (W378), calculated as a deviation from the NeC herd, were 40.2 and 44.3 kg for the NeS and NeT herds, respectively. The correlated changes, for the other traits were, in the same order, 4.5 and 4.5 cm for hip height (HH); 6.2 and 7.0 cm for chest girth (CG); 5.8 and 6.3 cm for body length (BL); 2.9 and 2.0 cm for dorsal line length (DL); 1.7 and 2.4 cm for rump length (RL); 1.0 and 1.3 cm for distance between pin bones (DPB); 1.8 and 2.6 cm for distance between hip bones (DHP); and 1.3 and 2.2 cm for scrotal perimeter (SP). The results of this study showed that the direct selection for postweaning weight promoted correlated positive responses in the body dimensions and also in the scrotal perimeter of Nellore males.

Modelagem e estimação de parâmetros genéticos e fenotípicos para pesos do nascimento à seleção (378 dias) de machos Nelore

Genetic parameters for weights (17, 942 records), obtained in intervals of 60 days, from the birth to selection (378 days of age), of 2,582 males of the Nellore breed was estimated in univariate analyses by the Maximum Restricted Likelihood method. The models of analysis models included the fixed effects of contemporary groups, month of birth, mother age and age when the weights were collected as covariate. Three models differing in random effects were tested: the model 1 (M1) was adjusted for the direct and maternal addictive genetic effects and maternal permanent environment; in model 2 (M2) the maternal genetic effect was excluded; and the model 3 (M3) was only adjusted for the direct addictive genetic effect. The test of likelihood (LRT) detected significant differences, for all the ages, of M2 and M1 in relation to the simple model (M3), evidencing the importance of the maternal effects. Except for the birth weight (0.40), low values (0.05 to 0.12) of h2 were found for M1 and M2 until 8 months of age and, after this period, reasonable increase could be observed, reaching 0.28 until 13 months of age. The estimates of the total variance fraction, due to the effect of maternal permanent environment, were high and practically became unaffected between the models 1 and 2. Maternal effects, not necessarily decomposed (in genetic addictive and permanent environment), affected the Nellore males growth. Models that contemplate maternal effects, besides the genetic addictive direct effects, are more realistic to describe the trajectory of the variances in the initial phases of growth of Nelore male calves.

Características de carcaça de bovinos de diferentes grupos genéticos, castrados e não-castrados, em fase de terminação

The objective of this trial was to investigate the physical characteristics of carcasses and primary cuts of 86 steers and bulls averaging 329 kg of body weight and 20 months of age. Twelve Gir, 20 Nellore, 20 Guzera , and 20 Caracu all from herds that genetically selected for weight gain at 378 days of age and 14 non-genetically improved Nellore (control) were used in this study. Corn silage was used as the forage portion of the diet in a 60:40 (% DM) forage to concentrate ratio. A completely randomized design with a 5 x 2 factorial arrangement of treatments (genetic group and sexual condition) was used. Bulls had carcasses with greater weight, yield, and proportion of muscular tissue but similar subcutaneous fat thickness compared to steers. Caracu showed a slower development but greater muscular tissue deposition and less fat deposition resulting in higher proportion of beef round compared to the remaining breeds. The genetically improved Zebu had heavier carcasses than the non-genetically improved Nellore. The greatest hot carcass weight within Zebu was observed on the genetically improved Nellore (287 kg) and was similar to that found on Caracu (299 kg). Genetically and non-genetically improved Nellore and Gir had the highest yields of hot carcass (57.83, 56.82 and 57.26%, respectively). Caracu showed the greatest carcass length (134 cm) while non-geneticallyimproved Nellore the lowest (118.67 cm). The rib eye area was greater on Caracu than Zebu whereas the opposite was observed for subcutaneous fat thickness with the exception of Gir. Within the genetically improved animals, Nellore had the greatest carcass weight and within sexual condition, bulls showed finishing covering fat that fulfills the market requirements.

Efeitos de raça e da seleção para peso pós-desmame sobre características de confinamento e de carcaça da 15ª progênie dos rebanhos Zebu e Caracu de Sertãozinho (SP)

Quarenta e quatro machos inteiros provenientes de rebanhos selecionados para peso aos 378 dias (P378), nascidos em 1995, foram confinados na Estacao Experimental de Zootecnia de Sertaozinho, Estado de Sao Paulo. As amostras, representando a media geral de P378 em cada rebanho, foram formadas por oito animais Guzera (GuS) e nove para cada um dos grupos Gir (Gi), Nelore (NeS), Nelore Controle (NeC) e Caracu (Ca). O abate ocorreu aos 580 dias de idade e condicao corporal 8, em uma escala de 1 a 9. As medias minimas e maximas ajustadas, para as principais caracteristicas, envolvendo todos os grupos, foram: ganho medio diario de peso, 817 (NeC) e 1061 g (Ca); peso de abate (PAB), 408,3 (Gi) e 513,6 kg (Ca); peso de carcaca (PCAR), 230,2 (Gi) e 285,0 kg (Ca); rendimento de carcaca, 55,6 (GuS) e 58,1% (NeC). No corte entre a 9a-11a costelas, foram: musculo: 55,7 (NeC) e 64,7% (Ca); gordura: 18,6 (Ca) e 26,9% (NeC); osso: 16,7 (Ca) e 19,2% (Gi); espessura de gordura (ESPGOR): 6,4 (Ca) e 7,5 mm (GuS); area de olho de lombo: 62,8 (Gi) e 76,6 cm2 (Ca); forca de cizalhamento: 4,4 (Ca) e 5,4 kg (Gi) e perdas totais no cozimento: 23,4 (NeC) e 26,1% (Ca). Considerando o grupo Nelore, a selecao para peso provocou maiores PAB e PCAR, sem alterar o rendimento, a composicao fisica da costela ou a qualidade da carcaca e da carne. Animais Ca tiveram maior PAB, porem menor rendimento, maior musculosidade e menores niveis de gordura e espessura de gordura. Ja GuS, com rendimento semelhante ao Ca, apresentou maior ESPGOR. Nao se observaram diferencas entre os grupos geneticos quanto aos indices de maciez e perdas no cozimento da carne.

Validação dos sistemas VIÇOSA, CNCPS e NRC para formulação de dietas para bovinos Nelore e Caracu, não-castrados, selecionados em condições brasileiras

Twenty-two animals, eight from genetic improved Nellore breed, six non-improved Nellore and eight from genetic improved Caracu breed, were used to evaluate and to validate the VICOSA, CNCPS (level 1 and 2) and NRC (level 1 and 2) systems, for diet formulations. The animals were confined with average live weight of 404 kg to genetic improved Nellore, 345 kg to non-improved Nellore and 434 kg to genetic improved Caracu breed, all with 18 months of age. The forage used was corn silage in forage to concentrate ratio of 50:50 in the diet. The slaughter criterion was determined by ultra-sound and it was executed when the animals reached an average of four millimeters of subcutaneous fat. The Student t test was used to compare the dry matter intake (DMI) and average daily gain (ADG) observed in the genetic groups and those predicted by the VICOSA, CNCPS and NRC systems. The VICOSA system showed a good estimate for ADG of the animals of genetic improved Nellore and non-improved Nellore breed, but the values were different of observed to improved Caracu. The VICOSA system does not have a good estimate for DMI for none of the three genetic groups. The CNCPS system, level 1 and 2 was efficient to estimate the DMI of the three genetic groups; however the estimative for ADG differed from the observed for both level 1 and level 2 of the system and the values were underestimated. In the NRC system, only the level 2 showed predicted values similar to those observed for both DMI and ADG.

Parâmetros genéticos do peso no início da estação de monta, considerado indicativo do peso adulto de matrizes Nelore

Genetic parameters were estimated for weight at the beginning of breeding season (PEM), considered as an indicative of mature weight of Nelore cows. Data file comprised 7,902 records from 1,556 cows from to a selection experiment conducted at the Estacao Experimental de Zootecnia de Sertaozinho, SP, Brazil. PEM were analyzed either as the last weight available for each cow in the data file (PEM_U) or as repeated records, including all weights (PEM_R). The analyses were also performed excluding the records of cows culled before reaching 4 years of age, and for both the last (PEM_U2) and the repeated (PEM_R2) records. Variance components were estimated by restricted maximum likelihood, fitting single and multiple trait animal models. The multiple trait models included the selection weights adjusted for 378 (males only) and 550 (females only) days of age. Heritability estimates obtained from the single trait analyses were 0.30±0.05, 0.37±0.06, 0.35±0.04 and 0.42±0.05, for PEM_U, PEM_U2, PEM_R and PEM_R2, respectively. Corresponding values for the multiple trait analyses were 0.34, 0.42, 0.56, and 0.57. Repeatability estimates for PEM_R and PEM_R2 were 0.58±0.01 and 0.69±0.01 for the single, and 0.61 and 0.72 for the multiple trait analyses, respectively. Estimates of genetic changes were significantly positive and equal to 0.40±0.08 and 0.35±0.07 percent of the mean per year, for the two selected lines in the experiment. The results obtained in the present study indicated the multiple trait repeated records models as the most appropriate for analyzing the PEM as an indicative of mature weight. The PEM could be included in a selection program aiming at monitoring a desirable mature weight.

Desempenho produtivo de bovinos de diferentes grupos raciais, castrados e não-castrados, em fase de terminação

Eighty-six castrated and non-castrated, approximately 20-month-old bovines averaging 329kg were used. They were 12 Gyr, 20 Nellore, 20 Guzera and 20 Caracu, which were submitted to selection to weight at 378 day-old (W378) and 14 control Nellore - chosen based on nule selection differential to W378. The diet contained 14.8% of crude protein in dry matter (DM) and corn silage was used in the ratio of 60:40% forage: concentrate in DM basis. A completely randomized design in a 5 x 2 factorial arrangement (breed and sexual condition) was used. The average daily gain of 1.51kg and 1.53kg for selected Nellore and Guzera did not differ, however surpassed those from the other breeds, which did not differ from each other. There was no difference between castrated and non-castrated animals. The dry matter intake in kg/day were higher for selected Nellore, Guzera and Caracu (10.30; 10.04 and 10.71kg/day, respectively) and the values observed for the two other groups did not differ from each other. The bionutritional efficiency was worse for Caracu (2.13) and better for control Nellore (1.58). Caracu needed to remain in feeding 133 days longer to reach 4mm of subcutaneous fat thickness. The time in feeding for the others groups were similar.