Gemelaridade em vacas leiteiras: incidência e a sua influência no desempenho produtivo em explorações do Litoral Norte de Portugal
Ficheiros
Data
2014-08-25
Autores
Título da revista
ISSN da revista
Título do Volume
Editora
Resumo
O presente trabalho teve como principal objetivo determinar a incidência de partos gemelares em vacas leiteiras, assim como avaliar a sua influência na produção em explorações do Litoral Norte de Portugal. Pretendeu-se ainda, avaliar a incidência de diversas doenças incluindo refugos e/ou mortes em vacas com partos gemelares, assim como a viabilidade dos vitelos ao parto e nos dias subsequentes. Foram recolhidos dados de 1109 partos ocorridos em 18 explorações leiteiras, durante os anos de 2010, 2011 e 2012. Os animais foram divididos em 2 grupos consoante apresentassem parto gemelar ou simples, correspondendo estes últimos ao grupo controlo, quando usado. A incidência de partos gemelares foi de 4,2% (47/1109; P<0,001), com variações (P<0,05) do n.º de fetos por parto entre explorações. A incidência de partos gemelares esteve positivamente correlacionada (r=0,73; n=18; P<0,01) com o n.º de partos totais em cada exploração. A maioria dos gémeos nascidos foi do sexo masculino (61,7%; 58/94; P=0,001). De todos os partos gemelares ocorridos, 51,0% (24/47) correspondeu a partos em que os vitelos eram de sexos opostos, 36,2% (17/47) eram ambos machos e 12,8% (6/47; P<0,001) eram ambos fêmeas. Destes gémeos, 63,8% (60/94) foram nados-vivos e 36,2% (34/94; P<0,001) foram nados-mortos ou morreram nos primeiros 3 dias. A duração da gestação gemelar foi de 268,8 ± 7,7 dias (± D.P.; n=12) e a gestação simples de 278,1 ± 6,6 dias (n=200; P<0,001). No entanto, o intervalo entre partos foi similar entre gestações gemelares (389,8 ± 31,6 dias; n=10) e simples (403,5 ± 79,7 dias; n=133; P>0,05). Em 70,2% (33/47; P<0,001) dos casos, a vaca apresentou alterações patológicas, morte ou refugo até um mês pós-parto, sendo que 69,7% (23/33; P=0,001) destas anomalias corresponderam a retenção placentária. Em vacas de 2ª lactação, a produção de leite aos 305 dias, foi maior quando estas apresentavam gestação gemelar (12621,6 ± 4036,7 kg; n=11) do que simples (10185,1 ± 2533,6 kg; n=159; P<0,01). No entanto, foi observado, que independentemente da paridade, vacas com partos gemelares apresentaram uma menor produção diária, durante o 1º mês de lactação após o parto, (34,2 ± 11,9 kg; n=31) do que vacas com partos simples (39,9 ± 11,7 kg; n=131; P<0,01). Já a produção acumulada, obtida a partir de cada um dos 5 primeiros contrastes leiteiros após o parto, foi similar (P>0,05) entre grupos, mesmo considerando o efeito da paridade. Concluímos que a incidência da gemelaridade em vacas leiteiras é afetada por fatores relacionados com a dimensão (n.º de partos) da exploração. A elevada ocorrência de partos gemelares com pelo menos um macho coloca restrições, destas gestações, ao programa de reposição de fêmeas nas explorações. Embora tenha sido observada uma maior produção de leite durante a gestação gemelar, estima-se que vacas com partos gemelares produzam, durante o 1º mês após o parto, menos leite (kg/dia) do que vacas com partos simples, provavelmente devido à elevada ocorrência de doenças, principalmente do foro reprodutivo. No entanto, esta diminuição não parece afetar a produção acumulada posterior.
The present study aimed to determine the incidence of twinning in dairy cows, as well as to evaluate its influence on production in farms of the North Coast of Portugal. It also intended to assess the incidence of several diseases including culling and/or deaths in cows with twin births, as well as the viability of calves at birth and on subsequent days. Data were collected from 1109 births in 18 dairy farms during the years 2010, 2011 and 2012. The animals were divided into 2 groups according to presentation of twin or simple birth, where the last ones corresponded to the control group, when used. The incidence of multiple births was 4.2% (47/1109; P<0.001), with variations (P<0.05) on the n.º of fetuses per calving between farms. The incidence of twin births was positively correlated (r=0.73; n=18; P<0.01) with the total n.º of births in each farm. Most twins born were male (61.7%; 58/94; P=0.001). Of all twin births occurred, 51.0% (24/47) corresponded to births in which the calves were of opposite sexes, 36.2% (17/47) were both males and 12.8% (6/47; P<0.001) were both females. It was observed that 63.8% (60/94) of these twins were live births and 36.2% (34/94; P<0.001) were stillbirths or died within the first 3 days. The gestation length of twin pregnancy was 268.8 ± 7.7 days (± SD; n=12) and single pregnancy was 278.1 ± 6.6 days (n=200; P<0.001). However, the calving interval was similar between twin pregnancies (389.8 ± 31.6 days; n=10) and single pregnancies (403.5 ± 79.7 days; n=133; P>0.05). In 70.2% (33/47; P<0.001) of the cases, the cow presented pathological changes, died or was culled until one month postpartum, and 69.7% (23/33; P=0.001) of these abnormalities corresponded to retained placenta. In cows of 2nd lactation, milk yield at 305 days was higher when they presented a twin pregnancy (12621.6 ± 4036.7 kg; n=11) than a simple pregnancy (10185.1 ± 2533.6 kg; n=159; P<0.01). However, it was observed that, regardless of parity, cows with twin births had a lower daily production during the 1st month of lactation after parturition (34.2 ± 11.9 kg; n=31) than cows with simple births (39.9 ± 11.7 kg; n=131; P<0.01). The accumulated production, obtained from each of the first 5 postpartum dairy contrasts were similar (P>0.05) between groups, even considering the effect of parity. We conclude that the incidence of twinning in dairy cows is affected by factors related to the size (number of births) of the farm. The high occurrence of twin births with at least one male puts restrictions of these pregnancies to the program of replacement heifers on farms. Although there was a higher milk yield during twin pregnancy, it is estimated that cows with twin births produce less milk (kg/day) during the 1st month after parturition, than cows with single births, probably due to the high occurrence of diseases, especially reproductive diseases. However, this decrease does not seem to affect further cumulative production.
The present study aimed to determine the incidence of twinning in dairy cows, as well as to evaluate its influence on production in farms of the North Coast of Portugal. It also intended to assess the incidence of several diseases including culling and/or deaths in cows with twin births, as well as the viability of calves at birth and on subsequent days. Data were collected from 1109 births in 18 dairy farms during the years 2010, 2011 and 2012. The animals were divided into 2 groups according to presentation of twin or simple birth, where the last ones corresponded to the control group, when used. The incidence of multiple births was 4.2% (47/1109; P<0.001), with variations (P<0.05) on the n.º of fetuses per calving between farms. The incidence of twin births was positively correlated (r=0.73; n=18; P<0.01) with the total n.º of births in each farm. Most twins born were male (61.7%; 58/94; P=0.001). Of all twin births occurred, 51.0% (24/47) corresponded to births in which the calves were of opposite sexes, 36.2% (17/47) were both males and 12.8% (6/47; P<0.001) were both females. It was observed that 63.8% (60/94) of these twins were live births and 36.2% (34/94; P<0.001) were stillbirths or died within the first 3 days. The gestation length of twin pregnancy was 268.8 ± 7.7 days (± SD; n=12) and single pregnancy was 278.1 ± 6.6 days (n=200; P<0.001). However, the calving interval was similar between twin pregnancies (389.8 ± 31.6 days; n=10) and single pregnancies (403.5 ± 79.7 days; n=133; P>0.05). In 70.2% (33/47; P<0.001) of the cases, the cow presented pathological changes, died or was culled until one month postpartum, and 69.7% (23/33; P=0.001) of these abnormalities corresponded to retained placenta. In cows of 2nd lactation, milk yield at 305 days was higher when they presented a twin pregnancy (12621.6 ± 4036.7 kg; n=11) than a simple pregnancy (10185.1 ± 2533.6 kg; n=159; P<0.01). However, it was observed that, regardless of parity, cows with twin births had a lower daily production during the 1st month of lactation after parturition (34.2 ± 11.9 kg; n=31) than cows with simple births (39.9 ± 11.7 kg; n=131; P<0.01). The accumulated production, obtained from each of the first 5 postpartum dairy contrasts were similar (P>0.05) between groups, even considering the effect of parity. We conclude that the incidence of twinning in dairy cows is affected by factors related to the size (number of births) of the farm. The high occurrence of twin births with at least one male puts restrictions of these pregnancies to the program of replacement heifers on farms. Although there was a higher milk yield during twin pregnancy, it is estimated that cows with twin births produce less milk (kg/day) during the 1st month after parturition, than cows with single births, probably due to the high occurrence of diseases, especially reproductive diseases. However, this decrease does not seem to affect further cumulative production.
Descrição
Dissertação de Mestrado Integrado em Medicina Veterinária, Ciências Veterinárias
Palavras-chave
Gemelaridade , Vaca leiteira , Desempenho reprodutivo , Distúrbio da reprodução , Epidemiologia