”Avaliação de fatores genotípicos, fenotípicos e nosológicos associados à duração da gestação na vaca leiteira”
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2018-04-12
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O parto é o momento de maior importância na dinâmica de uma exploração leiteira. A sua complexidade exige procedimentos especiais de maneio dos animais envolvidos no período imediatamente anterior de forma a minimizar a ocorrência de distocias e a preparação da vaca para a nova lactação. Para que se consiga prever de forma adequada a data do parto, é essencial conhecer a duração da gestação (DG) e quais os fatores com ela associados. O presente trabalho debruçou-se sobre o estudo da associação de diversos fatores com a DG. Os dados utilizados na sua elaboração provieram de uma exploração de bovinos de leite da região de Barcelos. O período de tempo considerado engloba aproximadamente 17 anos (janeiro de 2000 – junho de 2017), envolvendo 1263 partos. Além da DG, avaliaram-se os parâmetros sexo do vitelo, raça dos progenitores, efeito individual do progenitor, mês e ano do parto, ocorrência de partos simples ou gemelares, mortalidade perinatal e neonatal e duração da lactação consequente ao parto e respetiva produção leiteira. A DG foi, em média, de 278,3±5,6 (± desvio-padrão) dias, sendo que a gestação envolvendo vitelos machos (279,3±5,3 dias; n=623) foi mais longa, em média, 1,6 dias, do que a de fêmeas (277,7±5,5 dias; n=588; P <0,001). Observou-se uma diferença de 2,3 dias entre a gestação de vacas primíparas (276,7±5,3 dias; n=382) e multíparas (279,0 ± 5,6 dias; n=881; P<0,001). A raça do progenitor influenciou significativamente (P<0,001) a DG. As vacas inseminadas com touros das raças Limousin (284,2±7,1 dias; n=18), Aberdeen Angus (280,0±5,5 dias; n=75) e Brown Swiss (282,0±5,9 dias; n=46) apresentaram uma DG maior do que as inseminadas com raças Holstein-Friesian (277,8±5,4 dias; n=972) ou Red Holstein-Friesian (275,7±5,1 dias; n=22). Os partos gemelares (272,8±6,5 dias; n=52) apresentaram menos 5,7 dias de gestação do que os partos simples (278,5±5,5 dias; n=1211; P<0,001). Os partos ocorridos durante o mês de janeiro (279,9±5,3 dias; n=133) tiveram mais 2 a 3 dias de gestação do que os ocorridos durante os meses mais quentes: maio (277,2±5,0 dias; n=106), junho (277,2±5,6; n=92) e julho (276,8±5,7 dias; n=95; P<0,001). Observou-se ainda uma maior percentagem de mortalidade neonatal (P<0,001) à medida que a DG se afastou da média. Verificou-se ainda que a DG aumentou (P<0,001) com o aumento da produção média diária na lactação seguinte e a estimada aos 305 dias.Com os dados obtidos foi possível determinar que, dos vários fatores que afetaram a DG, a gestação gemelar, a raça do pai e os meses mais quentes foram os que mais variação promoveram (3 ou mais dias). No entanto, especial atenção deve ser dada às novilhas, uma vez que neste grupo, além de se observar um encurtamento da DG, há maior propensão para mortalidade neonatal. Além da determinação da gemelaridade, o sexo fetal pode ser usado como preditor, em situações de uso de sémen sexado e/ou de avaliação ecográfica. Finalmente, a DG está positivamente associada com uma maior produção leiteira na lactação subsequente.
Calving is the most important moment in a dairy farm. Its complexity requires special management procedures for the animals involved, mainly during the pre-partum period, in order to minimize the occurrence of dystocia and to prepare the females for the new lactation phase. Additionally, it is essential to know the gestation length (GL) and associated factors to accurately predict the date of parturition. The present work aimed to evaluate associations of several factors with the GL. The data used in its elaboration came from a bovine dairy farm located in the region of Barcelos (Portugal). The considered period of time encompasses approximately 17 years (January of 2000 – June of 2017), involving 1263 parturitions. Despite the GL, the calf sex, parental breed, bull individual effect, month and year of calving, occurrence of single or twin fetuses, perinatal and neonatal mortality, and lactation length and respective milk production after delivery were evaluated. The GL was 278.3±5.6 (± DP) days. The GL involving male calves (279.3 ± 5.3 days; n=623) was 1.6 days longer than the females (277.7 ± 5.5 days; n=588; P<0.001). There was a difference of 2.3 days between the gestation of primiparous cows (276.7 ± 5.3 days; n=382) and multiparous (279.0 ± 5.6 days; n=881; P<0.001). It was observed that cows inseminated with service sire from Limousin breed (284.2 ± 7.1 days: n = 18), Aberdeen Angus (280.0 ± 5.5 days; n=75) and Brown Swiss (282.0 ± 5.9 days; n=46) had a longer gestation period than cows inseminated with Holstein Friesian sire’s (277.8 ± 5.4 days; n=972;P<0.001) and Red Holstein Friesian (275.7 ± 5.1 days; n=22). Twin births (272.8 ± 6.5 days; n=52) presented less 5.7 days of GL than single-births (278.5 ± 5.5 days; n=1211; P<0.001). Births occurred during January (279.9 ± 5.3 days; n=133) had more 2-3 days of gestation than those occurring in the hottest months: May (277.2 ± 5.0 days; n=106), June (277.2 ± 5.6; n = 92) and July (276.8 ± 5.7 days; n = 95; P < 0.001). The neonatal mortality rate was higher for GL far from mean (P<0.001). It was observed that GL increases (P<0.001) with the increase of daily production and standardized milk yield. In conclusion, the gemelarity, the breed of the father and months of hot season were the factos involved in high GL variation (3 or more days). However, special attention should be given to heifers, despite the short PL, this females group show more percentage of neonatal mortality. The gemelarity and fetal sex can be used as a GL predictor, when sexed semen and/or ultrasonographic examination is performed. Finally, GL is associated with increased dairy production in subsequent lactation
Calving is the most important moment in a dairy farm. Its complexity requires special management procedures for the animals involved, mainly during the pre-partum period, in order to minimize the occurrence of dystocia and to prepare the females for the new lactation phase. Additionally, it is essential to know the gestation length (GL) and associated factors to accurately predict the date of parturition. The present work aimed to evaluate associations of several factors with the GL. The data used in its elaboration came from a bovine dairy farm located in the region of Barcelos (Portugal). The considered period of time encompasses approximately 17 years (January of 2000 – June of 2017), involving 1263 parturitions. Despite the GL, the calf sex, parental breed, bull individual effect, month and year of calving, occurrence of single or twin fetuses, perinatal and neonatal mortality, and lactation length and respective milk production after delivery were evaluated. The GL was 278.3±5.6 (± DP) days. The GL involving male calves (279.3 ± 5.3 days; n=623) was 1.6 days longer than the females (277.7 ± 5.5 days; n=588; P<0.001). There was a difference of 2.3 days between the gestation of primiparous cows (276.7 ± 5.3 days; n=382) and multiparous (279.0 ± 5.6 days; n=881; P<0.001). It was observed that cows inseminated with service sire from Limousin breed (284.2 ± 7.1 days: n = 18), Aberdeen Angus (280.0 ± 5.5 days; n=75) and Brown Swiss (282.0 ± 5.9 days; n=46) had a longer gestation period than cows inseminated with Holstein Friesian sire’s (277.8 ± 5.4 days; n=972;P<0.001) and Red Holstein Friesian (275.7 ± 5.1 days; n=22). Twin births (272.8 ± 6.5 days; n=52) presented less 5.7 days of GL than single-births (278.5 ± 5.5 days; n=1211; P<0.001). Births occurred during January (279.9 ± 5.3 days; n=133) had more 2-3 days of gestation than those occurring in the hottest months: May (277.2 ± 5.0 days; n=106), June (277.2 ± 5.6; n = 92) and July (276.8 ± 5.7 days; n = 95; P < 0.001). The neonatal mortality rate was higher for GL far from mean (P<0.001). It was observed that GL increases (P<0.001) with the increase of daily production and standardized milk yield. In conclusion, the gemelarity, the breed of the father and months of hot season were the factos involved in high GL variation (3 or more days). However, special attention should be given to heifers, despite the short PL, this females group show more percentage of neonatal mortality. The gemelarity and fetal sex can be used as a GL predictor, when sexed semen and/or ultrasonographic examination is performed. Finally, GL is associated with increased dairy production in subsequent lactation
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produção de leite , vacas leiteiras