Arione Augusti Boligon

Associações genéticas entre pesos e características reprodutivas em rebanhos da raça Nelore

Records from 14,918 Nellore animals born from 1991 to 2000 in 28 herds in the South and Southeast regions of Brazil were used to estimate (co)variance components and genetic parameters for weaning weight (WW), yearling weight (YW), weights at 18 month of age (WAY) and at first calving (WFC), age at first calving (AFC) and days to first calving (DC). Multivariate animal models were fitted by REML. Estimates of heritability for WW, YW, WAY, WFC, AFC and DC were 0.26; 0.30; 0.34; 0.35; 0.14 and 0.07, respectively. Genetic correlations estimates among growth traits and AFC were moderate and negative, ranging from -0.31 to -0.16. Genetic correlation estimates were also negative for DC and WW (-0.09); YW (-0.13); WAY (-0.17) and WFC (-0.16). Genetic correlation estimates between growth traits and AFC were favorable and indicate it may be possible to reduce AFC through indirect selection on pos-weaning growth traits. The genetic correlation estimate between AFC and DC was high and positive (0.73) suggesting that selection for DC may result in correlated response for age at first calving.

Correlações genéticas entre medidas de perímetro escrotal e características produtivas e reprodutivas de fêmeas da raça Nelore

Genetic parameters for scrotal circumference at 12 (SC12) and at 18 months of age (SC18) of males, and yearling weight (W365), weight at first calving (WFC), age at first calving (AFC), days to first calving (DC) and length of first gestation (GL) of females were estimated using records from 9,932 females and 14,521 males from 28 Nellore herds, located in the South and Southeast regions of Brazil. Covariance components were estimated by REML, fitting bivariate animal models. Heritability estimates were high for SC12 (0.25 to 0.26), SC18 (0.35 to 0.37), W365 (0.35 and 0.38), WFC (0.40 and 0.41) and GL (0.19 and 0.20), but low for AFC (0.14 and 0.15) and DC (0.05 and 0.06). Genetic correlation estimates between SC12 and W365, WFC, AFC, DC and GL were 0.28, 0.30, -0.15, -0.04 and 0.10, respectively. In the same order, the respective genetic correlation estimates between SC18 and female traits were 0.29, 0.32, -0.21, -0.08 and 0.14. These results suggest that selection to improve female fertility efficiency based on SC18 would be more effective than by using SC12.

Herdabilidades e correlações entre pesos do nascimento à idade adulta em rebanhos da raça Nelore

Records of 19,458 Nellore breed animals, born from 1975 to 2002, from 8 herds participating in the Nellore Cattle Breeding Program (NCBP) were used to estimate (co)variance components, heritability and genetic correlations for birth weight, weaning weight, weight after yearling and at 2, 3 and 5 years of age. The restricted maximum likelihood method, with univariate, bivariate and multivariate analyses, was used. The models included the random additive genetic direct effect (animal) and fixed effects of age group and the linear and quadratic effects of calf age (except for the birth weight model) and age dam at calving. The random effect of permanent maternal environment was included in the analyses models for birth weight, weaning weight and yearling weight, and the random effect of maternal genetics only in the model for weaning weight. The heritability estimates, in multivariate analysis for weights at birth, weaning, yearling and at 2, 3 and 5 years of age were 0.25; 0.33; 0.34; 0.32; 0.33 and 0.35, respectively. The genetic correlations estimated between traits were positive and moderate to high in magnitude and tended to decrease with the increase in the distance between records, that indicated that selection for weight at any age will promote genetic change in weights at other ages including the female mature weight of the Nellore breed. The heritability estimates obtained in the multivariate analysis were high, especially at 3 and 5 years of age, suggesting better partition of genetic and environmental variances compared to uni and bivariate analyses but, high computer demands can still hinder its use in large databases.

Estimativas de herdabilidade e tendências genéticas para características de crescimento e reprodutivas em bovinos da raça Nelore: Estimates of heritability and genetic trends for growth and reproduction traits in Nelore cattle

The heritability coefficients and genetic trends for weaning weight (WW), post-yearling weight (PW), average gains from birth to weaning (GBW), average gains from weaning to post-yearling (GWP), scrotal circumference (SC), and age at first calving (AFC) were estimated in Nelore cattle. Variance components and heritability coefficients were estimated by restricted maximum likelihood and breeding values were predicted fitting bivariate animal models, always including weaning weight. Data from 128,148 animals born from 1984 to 2006 were used. Genetic trends for each trait were estimated by regression of breeding values on the animal birth year. Heritability estimates for direct effect were 0.23 (0.07) for WW; 0.24 (0.02) for PW; 0.21 (0.01) for GBW; 0.23 (0.01) for GWP; 0.46 (0.02) for SC; and 0.15 (0.01) for AFC. The direct genetic trends were 0.171 (0.01); 0.219 (0.02); 0.186 (0.03); and 0.224 (0.02) kg per year, for WW, PW, GBW, and GWP, respectively, corresponding to increases of 0.10, 0.08, 0.13, and 0.22% in the means of the same traits per year, respectively. In the first period (1984 to 1995), the SC and AFC genetic trends were null, with values of 0.011 (0.03) cm/year and -0.003 (0.06) days/year, respectively. Moreover, in the other period (1996 to 2006), the genetic trends of SC and AFC were 0.069 (0.01) cm/year and -3.024 (0.04) days/year, respectively. These values suggest that productive and reproductive traits, when used as selection criteria, result in genetic progress of the herd. Thus, they are indicated for selection of Nelore cattle.

Estimation of genetic parameters for body weights, scrotal circumference, and testicular volume measured at different ages in Nellore cattle.

Data from 129,575 Nellore cattle born between 1993 and 2006, belonging to the Jacarezinho cattle-raising farm, were used to estimate genetic parameters for scrotal circumference measured at 9 (SC9), 12 (SC12), and 18 (SC18) mo of age and testicular volume measured at the same ages (TV9, TV12, and TV18) and to determine their correlation with weaning weight (WW) and yearling weight (YW), to provide information for the definition of selection criteria in beef cattle. Estimates of (co)variance components were calculated by the REML method applying an animal model in single- and multiple-trait analysis. The following heritability estimates and their respective SE were obtained for WW, YW, SC9, SC12, SC18, TV9, TV12, and TV18: 0.33 +/- 0.02, 0.37 +/- 0.03, 0.29 +/- 0.03, 0.39 +/- 0.04, 0.42 +/- 0.03, 0.19 +/- 0.04, 0.26 +/- 0.05, and 0.39 +/- 0.04, respectively. The genetic correlation between WW and YW was positive and high (0.80 +/- 0.04), indicating that these traits are mainly determined by the same genes. Genetic correlations between the growth traits and scrotal circumference measures were positive and of low to moderate magnitude, ranging from 0.23 +/- 0.04 to 0.38 +/- 0.04. On the other hand, increased genetic associations were estimated between scrotal circumference and testicular volume at different ages (0.61 +/- 0.04 to 0.86 +/- 0.04). Selection for greater scrotal circumference in males should result in greater WW, YW, and testicular volume. In conclusion, in view of the difficulty in measuring testicular volume, there is no need to change the selection criterion from scrotal circumference to testicular volume in genetic breeding programs of Zebu breeds.

Study of relations among age at first calving, average weight gains and weights from weaning to maturity in Nellore cattle

Data from 23,120 Nellore animals were used to estimate genetic parameters for age at first calving, average gains from weaning to yearling and from yearling to after yearling, weaning weight, yearling weight, after yearling weight and weight at 2 and 5 years of age. Animal models were fitted by Restricted Maximum likelihood Method. Estimate heritability for age at first calving, weaning to yearling weight gain, yearling to after yearling weight gain, weight at weaning, yearling weight, after yearling weight and weight from 2 to 5 years of age were 0.17 ± 0.01; 0.23 ± 0.03; 0.25 ± 0.03; 0.28 ± 0.02; 0.26 ± 0.03; 0.30 ± 0.03; 0.32 ± 0.02 and 0.36 ± 0.04, respectively. The genetic correlation estimates between age at first calving and weight traits ranged from -0.26 to -0.14. The genetic correlation estimates between age at first calving and average gains were also negative, but higher (-0.29 and -0.32). In general, these results indicate that selection for average gains will promote changes in age at first calving and female mature weight. Improvement in reproductive performance could be obtained with the inclusion of the age at first calving in the selection index.

Efeito da interação genótipo × ambiente sobre o peso ao nascimento, aos 205 e aos 550 dias de idade de bovinos da raça Nelore na Região Sul do Brasil

This study aimed to evaluate the genotype × environment interaction effect on birth (PN), weaning (P205) and yearling (P550) weights of Nellore cattle raised in 46 farms in three states (Rio Grande do Sul-RS, Santa Catarina-SC and Parana-PR) of the South Region of Brazil, from 1976 to 2001. Records on 10,874 animals, sired by 425 bulls and 7,629 dams were used to estimate (co)variance components by REML. Univariate and bivariate models included the contemporaneous group, feeding type (P205 and P550), management type (P205 and P550), age of cow at calving (PN and P205) covariate (linear and quadratic components) as fixed effects and direct additive genetic (PN, P205 and P550), maternal (PN and P205) and residual as random effects. Direct heritability estimates of PN, P205 and P550 within each State ranged from 0.38 ± 0.04 to 0.56 ± 0.08; from 0.22 ± 0.03 to 0.47 ± 0.05 and from 0.35 ± 0,03 to 0.51 ± 0,05, respectively. Maternal heritability estimates for the States ranged from 0.19 ± 0.03 to 0.31 ± 0.03 (PN) and from 0.16 ± 0.08 to 0.48 ± 0.07 (P205). Genetic correlations for PN, P205 and P550 between states were 0.75 ± 0.03, 0.25 ± 0.05 and 0.64 ± 0.07; 0.79 ± 0.08, -0.04 ± 0.07 and 0.41 ± 0.07 and 0.53 ± 0.02, 0.08 ± 0.15 and 0.76 ± 0.09 respectively for the RS-SC, RS-PR and SC-PR pairs. Overall, the Spearman correlations between breeding values (DEP) for PN, P205 and P550 predicted in different States were low. Changes in sire ranks between states indicate the presence of genotype× environment interaction in growth traits of Nellore cattle.

Genetic parameters and relationships between growth traits and scrotal circumference measured at different ages in Nellore cattle

Records from 106,212 Nellore animals, born between 1998 and 2006, were used to estimate (co)variance components and genetic parameters for birth weight (BW), average weight gains from birth to weaning (GBW), average weight gains from weaning to after yearling (GWAY), weaning hip height (WHH), postweaning hip height (PHH) and scrotal circumferences at 9 (SC9), 12 (SC12) and 15 (SC15) months of age. (Co)variance components were estimated by an animal model using multi-trait analysis. Heritability estimates for BW, GBW, GWAY, WHH, PHH, SC9, SC12 and SC15 were 0.31 ± 0.01; 0.25 ± 0.02; 0.30 ± 0.04; 0.51 ± 0.04; 0.54 ± 0.04; 0.39 ± 0.01; 0.41 ± 0.01 and 0.44 ± 0.02, respectively. Genetic correlations between growth traits ranged from 0.09 ± 0.01 to 0.88 ± 0.01, thereby implying that, at any age, selection to increase average weight gains will also increase stature. Genetic correlations between BW and average weight gains with scrotal circumferences were all positive and moderate (0.15 ± 0.03 to 0.38 ± 0.01). On the other hand, positive and low genetic associations were estimated between hip height and scrotal circumference at different ages (0.09 ± 0.01 to 0.17 ± 0.02). The results of this study pointed out that selection to larger scrotal circumferences in males will promote changes in average weight gains. In order to obtain Nellore cattle with the stature and size suitable for the production system, both weight gain and hip height should be included in a selection index.

Herdabilidade e tendência genética para as produções de leite e de gordura em rebanhos da raça Holandesa no estado do Rio Grande do Sul

Data comprising 5,007 records of first lactation of Holstein cows, daughters of 930 sires, from 33 herds in the state of Rio Grande do Sul, from 1984 to 1998, were used to estimate heritability coefficients and genetic trends for milk (MY) and fat (FY) yields and for fat percentage (%F). An animal model considered the genetic additive direct and residual as random effects and milking/day number, herd and year/season of parturition, and cow age at parturition as fixed effects, linear and quadratic effects, as covariate, inn order to estimate the coefficients of heritability and to predict the breeding values (BVs) for MY, FY and %F. The genetic trend was estimated by the regression of mean annual animal BVs in relation to animal year birth. The averages and respective standard deviations for MY, FY and %F were: 6,862.80 ± 1,881.21 kg/year, 228.63 ± 78.01 kg/year and 3.32 ± .18 %/year, respectively. The estimated coefficients of heritability and respective standard error for MY, FY and %F were: 0.30 ± 0.008; 0.28 ± 0.004 and 0.22 ± 0.015, respectively. The estimated genetic correlations were: 0.85 ± 0.19 and -0.15 ± 0.17 for MY and FY and MY and F%, respectively. The genetic trend for MY was of 9.25 kg/year, 0.11 kg/year for FP and -0.07%/year for %F. The values estimated for the coefficients of heritability suggest that it is possible to increase the rates for genetic gain for MP and FP, without change on %F rate. The genetic gains for MY and FY were positive, but low, however they can be improved if breeding programs that stimulate the dairy man to increase both traits milk quality are implemented.

Correlações genéticas entre escores visuais e características reprodutivas em bovinos Nelore usando inferência bayesiana

The aim of this work was to estimate the heritability and the genetic correlations between visual scores and reproductive traits of Nelore cattle. The traits evaluated were: finishing, muscling, and conformation scores at weaning (PD, MD, and CD, respectively) and yearling (PS, MS and CS, respectively); age at the first calving (IPP) and scrotal circumference (PE). The records of 66,244 animals born between 1990 and 2006 were used. The genetic parameters were estimated using bi-trait animal analyses with Bayesian inference. A linear model for IPP and PE and a nonlinear (threshold) model for visual scores were used. The heritability estimates were: CD, 0.19±0.02; PD, 0.23±0.02; MD, 0.20±0.02; CS, 0.26±0.01; PS, 0.33±0.02; MS, 0.32±0.02; IPP, 0.16±0.03; and PE, 0.36±0.02. Genetic correlation estimates between visual scores and IPP were negative, varying from -0.18±0.03 to -0.29±0.02. Positive genetic correlations were obtained between the visual scores and PE, from 0.19±0.01 to 0.31±0.01. Animal selection with the highest visual scores, mainly those taken after the yearling age, allows to improve herd reproductive traits.