Tomás Weber

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.

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.

Efeito de fatores ambientais sobre escores de avaliação visual à desmama e estimativa de parâmetros genéticos, para bezerros da raça charolês

To evaluate the influence of environmental factors on visual scores at weaning on Charolais breed animals, and to estimate genetic parameters, it were used records collected by PROMEBO from 1994 to 2002. The traits evaluated were the visual scores for conformation (C), precocity (P), muscling (M) and size (T) at weaning. First of all, it was performed an analyse of variance to verify wich environmental effects were significant on the studied characteristics. The model used considered, as fixed, the effect of contemporaneous group (GC), as covariables, the effects of age of the dam at parturition (IV), age at weaning (ID) and Julian date of birth (DJ) and the residual effect. All the variables included in the model affected significantly visual scores (P<0,05), except DJ, for M, P and C. From the adjusted averages for C, P, M and T it were adjusted regression equations for IV, ID and DJ. It was observed that cows freshening between 7 and 8 years produced calves with larger scores. In relation to the weaning age, it was observed that the animals weaned later presented more elevated visual scores. In relation to the Julian date of born, it was verified that calves born in June were favored in their scores, when compared with animal that born in December and January. The genetic parameters were estimated by Restricted Maximum Likelihood Method, using an animal model considering as fixed the effect of GC and, as covariables, IV, ID and DJ and, as random, the additive genetic direct and maternal and the residual effects. The heritability estimated for genetic direct effect and standard errors were .37 (.09), .35 (.09), .33 (.09) and .27 (.09), respectively, for C, M, P and T. These results suggest that the evaluation for visual scores, must to considerate the studied fixed effects, and that it is possible to include these characteristics in breeding programs.

Genetic parameters and phenotypic and genetic trends for weight at weaning and visual scores during this phase estimated for Angus-Nellore crossbred young bulls

Genetic parameters and genetic and phenotypic trends were estimated for weight at weaning (WW) and visual scores (VS) of conformation (C), precocity (P), musculature (M) and navel (N) for Angus × Nellore crossbred calves. It was used 39,676 records from pre-weaning phase of animals born from 1992 to 2002 in mid-western, southeastern and southern Brazil. The components of covariance were estimated using REML, in animal model, considering as random the maternal and direct additive genetic effects, and as fixed, the effects of contemporaneous group, the genetic group of the animal and of the cow, and as covariates the age of the calf at weaning and the age of the cow at calving, both on days and with linear and quadratic effects, besides direct (DH) and maternal heterosis (MH), both with only the linear effect. Estimates of direct and maternal heritability were 0.30 and 0.19, respectively, for WW, whereas VSs ranged from 0.16 to 0.20 and from 0.09 to 0.16, which indicates the possibility to obtain genetic gain through selection. It is expected answer correlated to C, P and for M when selection is practiced for weight at weaning is expected, as well as for P and M when selection is practiced for C. The direct and maternal genetic trends for WW (g/year) and for C, P, M and N (points/year) were: 221.0 and -312.0; 0.0022 and 0.00003; 0.0010 and 0.0001; 0.0013 and -0.0008; 0.0010 and 0.00009, respectively, while the phenotypic were: -685.2; -0.0102; -0.0219; -0.0256 and -0.0453, which highlights the need to adopt criteria for identifying young bulls of higher genetic value for WW and VSs.

Genetic parameters and genetic and phenotypic trends for pre-weaning productive and conformation traits for an Aberdeen Angus breed population

To estimate genetic parameters and to evaluate the genetic and phenotypic progress for the traits birth weight (PN), average daily gain from birth to weaning (GMDND), weaning weight adjusted to 205 days of age (P205) and the visual scores for conformation, precocity, musculature and size, at the pre weaning phase, there were used information from 23,176 Aberdeen Angus breed animals born between 1994 and 2004. The covariance components were obtained by REML, using an animal model. The direct and maternal heritabilities ranged from 0.10 (musculature) to 0.27 (PN) and the maternal from 0.07 (GMDND) to 0.21 (P205). The genetic correlations between GMDND and visual scores ranged from 0.55 to 0.66 and for the visual scores in between themselves from 0.50 to 0.92. The genetic trends for PN, GMDND, P205 were 17.5, 1.1, 220.9 (g/year) and for the visual scores were almost zero; the phenotypic were 29.8, -3.3, 467.9 (g/year). The estimated direct heritabilities suggest that it can be possible to get genetic gain by selection in this population, although for the visual scores the gain will be low. The genetic correlations between GMDND and visual scores show that selection for GMDND promotes improvement in visual scores and vice-versa. The genetic trends indicate genetic progress, however the phenotypic, negatives for some traits, suggest the necessity of to improve environmental conditions.To estimate genetic parameters and to evaluate the genetic and phenotypic progress for the traits birth weight (PN), average daily gain from birth to weaning (GMDND), weaning weight adjusted to 205 days of age (P205) and the visual scores for conformation, precocity, musculature and size, at the pre weaning phase, there were used information from 23,176 Aberdeen Angus breed animals born between 1994 and 2004. The covariance components were obtained by REML, using an animal model. The direct and maternal heritabilities ranged from 0.10 (musculature) to 0.27 (PN) and the maternal from 0.07 (GMDND) to 0.21 (P205). The genetic correlations between GMDND and visual scores ranged from 0.55 to 0.66 and for the visual scores in between themselves from 0.50 to 0.92. The genetic trends for PN, GMDND, P205 were 17.5, 1.1, 220.9 (g/year) and for the visual scores were almost zero; the phenotypic were 29.8, -3.3, 467.9 (g/year). The estimated direct heritabilities suggest that it can be possible to get genetic gain by selection in this population, although for the visual scores the gain will be low. The genetic correlations between GMDND and visual scores show that selection for GMDND promotes improvement in visual scores and vice-versa. The genetic trends indicate genetic progress, however the phenotypic, negatives for some traits, suggest the necessity of to improve environmental conditions.

Efeitos genéticos aditivos diretos e maternos e heterozigóticos sobre os desempenhos pré e pós-desmama em uma população multirracial Aberdeen Angus × Nelore

The objective of this study was to estimate direct and maternal additive genetic, non-additive and heterozygotic effects for pre and post-weaning traits and to develop equations to predict growth performance in a multi-breed Aberdeen Angus (Angus)-Nellore herd. The analyses were performed by SAS® using two different models. The model 1 (M1) was used for the pre-weaning traits, weaning weight adjusted to 205 days of age (P205) and average daily gain from birth to weaning (GMDND), and included the fixed effects of contemporary groups (GC), genetic groups (GG) and the covariates age of calf at weaning (IBD) and age of cow at calving (IVP). The same model except for replacing the covariate IBD by age of calf at yearling (IBS) was used for the post-weaning traits - yearling weight adjusted to 550 days of age (P550) and average daily gain from weaning to yearling (GMDDS). A multiple regression model (M2) was used after adjusting the data for GC, IVP and IBD (P205) and IBS (P550) effects and included the breed direct and maternal additive and the direct and maternal heterozygotic effects. Animals with higher maternal heterozygosis performed better for P205 and GMDND. A similar trend was observed for the direct heterozygosis. The direct genetic effect was larger than the maternal genetic effect for P550 and GMDDS. The additive direct effect determined better performances in the Angus breed. Differences between the estimated (M1) and predicted (M2) averages for P205, P550 and GMDDS were not significant.

Parâmetros genéticos e tendências genética e fenotípica para características de crescimento em uma população da raça Brangus

This study aimed to estimate the genetic parameters and genetic and phenotypic trends for weight at weaning (PD), yearling weight (PS), average daily gain from birth to weaning (GMDND), average daily gain from weaning to yearling (GMDDS), days to reach 160 kg at the pre weaning phase (D160) and days to reach 240 kg at post weaning phase (D240) of Brangus cattle raised in 37 farms in South, Southern and Mid Western Regions of Brazil, from 1987 to 2001. Records on 9,573 Brangus animals, sired by 415 bulls and 7,297 dams, were used to estimate (co)variance components by REML.The model included the genetic group of bull and dam and of contemporary group, age of cow at deliver, age at weaning weight and age at yearling weight covariate (linear and quadratic componentes) as fixed effects and the direct additive genetic, maternal and residual as random effects. The averages observed for PD, PS, GMDND, GMDDS, D160 and D240 were 171.62 kg, 306.2 kg, 0.701 kg, 0.395 kg, 234.97 days and 720.52 days, respectively. The direct heritabilities ranged from 0.15 (D240) to 0.45 (GMDND) and the maternal from 0.20 (PD) to 0.28 (GMDND). The genetic and phenotypic trends were 7.59 g/year and 0.864 kg/year; 5.16 g/year and 2.274 kg/year; 0.036 g/year and 0.007 kg/year; 0.011 g/year and 0.012 kg/year; -0.11 days/year and -1.59 days/year; -0.78 days/year and -9.79 days/year, respectively, for PD, PS, GMDND, GMDDS, D160 and D240.

Metanálise para características de carcaça de bovinos de diferentes grupos genéticos

The meta-analysis methodology was applied in this study to evaluate factors that affect the carcass quality components in beef cattle (rib eye area - AOL and fat thickness - EGC, measured between the 12th and the13th ribs) and to compare them in different genetic groups. Data from 215 measures of AOL and 209 measures of EGC, from 65,174 animals, extracted from 36 papers published between 1985 and 2006 were used. The Restricted Maximum Likelihood Method and an animal model that considered AOL and EGC as functions of the fixed effects of country from where the data come from; animal category; feed system; measure methodology; Bos indicus, british and continental Bos taurus gene contribution; age and weight at measure, were used. The observed averages for AOL and e EGC were 63.5cm2 and 4.2mm, respectively. The animals were in average 552.22 days old at the measure of the characteristics and had 468.47kg of live weight. The use of meta-analysis permitted to get generalized conclusions about AOL and EGC: animals rose in the EUA presented values significantly superior for AOL and EGC when compared with those rose in Australia and Brazil; castrated and the entire males presented bigger AOL measures (do not differing among them) compared to females, and females presented bigger EGC. The feed system, confined and do not confined, were superior to the greasing system. The Continental Bos taurus genotypes presented bigger AOL values, British Bos taurus presented bigger EGC values, and Bos indicus presented intermediate values. The measures taken in the carcass (pos mortis) and by ultra son (in vivo) were not different. The increase in the characteristics decreased with the age and live weight increase.

Efeito da inclusão da covariância genética aditiva direta-materna no modelo de análise sobre a magnitude das estimativas de parâmetros e valores genéticos preditos para ganho de peso na raça Brangus

The objective of this research was to study the effect of accouting for the covariance between the additive genetic direct and the maternal effects (covd-m) on the estimates of genetic parameters and on predictions of genetic values (VG), for average daily gain from birth to weaning (GMDND) and from weaning to 550 days of age (GMDDS). They were analyzed 28,949 records for GMDND and 11,884 for GMDDS of a Brangus breed population (5\8 Angus x 3/8 Nellore), collected from 1986 to 2002. The (co)variance components were obtained by REML. In the animal model for GMDND, the additive genetic direct and maternal and residual effects were considered as random, and the effects of contemporaneous group at weaning (Gc205), the interaction of the Nellore-Angus breed genetic percentage of the bull and cow (FGNA) and the covariables, age of the cow at birth (IV) and age at weaning (ID) as fixed effects. For GMDDS, the model was the same, except that Gc205 was substituted by contemporaneous group at 550 days of age (CG550) and ID by age at 550 days. In both models, permanent environmental effect of the cow was considered as a random effect. The heritabilities estimated for direct genetic effects ranged from 0.14 ± 0.03 to 0.21 ± 0.03 and for maternal effects from 0.00 ± 0.01 to 0.15 ± 0.02, the estimates had smaller values when covd-m was included in the model for GMDND. The correlations between genetic direct and maternal effects were negative -0.25 ± 0.12 (GMDND) and -0.77 ± 0.19 (GMDDS). The likelihood ratio test showed that there is no significant diference, at 5% significance level, between the adopted models for boths characteristics. The rank correlation between the VG predicted by the two models, were 0.89 for GMDND and 0.98 for GMDND, suggesting that a slight change in the rank of the animals can happen, for GMDND.

Coeficientes de herdabilidade e correlações genéticas para as produções de leite e de gordura, em diferentes níveis de produção, para raça Holandesa no estado do Rio Grande do Sul

Heritability and genetic correlations coefficients in different levels of milk production and fat were evaluated in this study. A data set of 8,887 milk and fat records from 5,875 Holstein cows, sired by 1,125 bulls from 1984 to 2001 were used. Dat a were stratified in three levels according to the herd milk production, low ( 6000 a 7500 kg). The (co)variance components were estimated by Restricted Maximum Likelihood Method including in an animal model as random, the genetic direct and the permanent environmental effects and as fixed, the effects of herd: milking control nucleus, year season, lactati on order, and the age of the cow at parturition and the period of lactation as co variables. The observed means and standard deviations f or milk (PL) and fat (PG) yields ranged from 4,922±743 kg to 8,760±126 kg and from 163±30 kg to 298±53 kg, respectively. The estimated heritability coefficients ranged from .13 to .19 and from .16 to .21, respectively for PL and PG. The highest values for the he ritability coefficients, for PL and PG were observed at the low and medium levels, suggesting that at these levels the improvement expecte d by selection could not be reached. The genetic correlation coefficients ranged from .91 to 1.00, suggesting that the selection for one of the characteristics will produce a similar response in the other.