Data de desmame e desempenho reprodutivo de vacas de corte

Abstract

RESUMO -O experimento foi conduzido na Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul, município de Eldorado do Sul, Brasil. O objetivo do estudo foi avaliar o efeito da data do desmame precoce (05/01/99) ou do convencional (26/03/99) sobre o desempenho reprodutivo de vacas de corte multíparas em duas estações de monta, 98/99, e a subseqüente, 99/00. Cinqüenta vacas tiveram seus bezerros desmamados em média aos 91 dias de vida, com peso mínimo de 70 kg (desmame precoce = DP), e 43 vacas desmamaram em média aos 170 dias, com peso médio de 131,2 kg (desmame convencional = DC). Os períodos de acasalamento ocorreram de 01/12/98 a 26/02/99, de 06/12/99 a 28/02/00. As vacas do DP apresentaram ganho médio diário (GMD) superior e melhor condição corporal (CC) que as do DC no primeiro acasalamento (0,828 kg x 0,549 kg; 2,4 x 2,0; P<0,05). O índice de prenhez em 1999 foi de 40,0% x 11,1% e em 2000 de 51,4% x 20,0%, para o DP e DC, respectivamente. Não foi observada diferença no intervalo entre partos. A taxa de prenhez no primeiro acasalamento foi menor que o esperado, devido possivelmente à baixa CC no início do acasalamento e à baixa recuperação durante o mesmo. Mesmo assim, o DP propiciou melhor CC às vacas durante o primeiro acasalamento, possibilitando índices reprodutivos significativamente melhores aos do desmame convencional.Palavras-chave: condição corporal, desempenho reprodutivo, idade de desmame, taxa de prenhez, vacas de corte Weaning Data and the Reproductive Performance of Beef CowsABSTRACT -The experiment was run at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, located in the district of Eldorado do Sul, Brazil. The objective of the study was to evaluate the effect of the date of early (01/05/99) or conventional (03/26/99) weaning on the reproductive performance of multiparous beef cows during two mating seasons, 98/99, and the subsequent, 99/00. Fifty cows had their calves weaned with an average age of 91 days old and a minimum liveweight of 70 kg (early weaning = EW), and 43 cows had calves weaned with an average age of 170 days old and mean liveweight of 131.2 kg (conventional weaning = CW). The mating periods were from 12/01/98 to 02/26/99 and from 12/06/99 to 02/28/00. Cows of EW had higher daily liveweight gains and better body condition (BC) than CW during the first breeding season (0.828 kg x 0.549 kg; 2.4 x 2.0; P<0.05). The pregnancy rate in 1999 was 40.0% x 11.1% and in 2000 it was 51.4% x 20.0% for EW and CW, respectively. There was no difference in the calving intervals. The pregnancy rate at first mating was lower than the expected, probably due to the low BC at beginning of the mating season and to the low recovery during the mating period. The EW improved cows BC during the first mating, making possible significantly better reproductive rates than the CW. ., v.31, n.3, p.1223-1229, 2002 IntroduçãoOs custos crescentes da pecuária de corte e a importância econômica do incremento dos índices reprodutivos incentivam o desenvol...

Effects of the weaning age of calves on somatic development and on reproductive performance of beef cows

“…These results are consistent with those obtained by , Moojen et al (1994), Simeone & Lobato, (1996); Restle et al (2001), and Almeida et al (2002), who found that cows submitted to early weaning presented higher pregnancy rates as compared to conventionally-weaned cows.…”

“…This resulted in a 39-day reduction in calving interval related to better nutritional conditions as compared to 2004/2005. This is consistent with the findings by Short et al (1972) and Montiel & Ahuja (2005), who also mention that the presence of calf with the cow causes a significant increase in the duration of post-calving anestrus, and consequently, of the calving interval. Almeida et al (2002), studying early weaning at 91 days, as carried out in the first year of the present study, observed an average calving interval of 399.2 days, which is similar to the result of 397.4 days that was obtained in this study. Those authors stated that this is not an optimal interval, because to obtain one calf/year, the required interval would be ± 365 days, as verified in the second year of observation, when weaning age was reduced to 67 days.…”

“…Under these conditions, lactating cows do not present good reproductive performance (Almeida et al, 2002) and do not supply their calves with enough milk to promote proper development (Restle et al, 2004).…”

“…The higher weight gain and the better body condition of cows whose calves were submitted to early weaning have a direct effect on their subsequent reproductive performance (Moojen et al, 1994;Simeone & Lobato, 1996;Lobato et al, 2000;Restle et al, 2001;Almeida et al, 2002).…”

“…According to Almeida et al (2002), despite the improvement of reproductive indexes when early weaning is used, the indexes themselves may not allow beef cattle production to be economically feasible. The authors conclude focusing on the importance of cow body weight and body condition at weaning, because, when negatively influenced by previous poor nutritional management (cows in that study grazed on low availability native pastures, with 730.5 kg DM/ha), reproductive performance is compromised.…”