Influência dos períodos de serviço anterior e corrente e do período seco anterior sobre a produção de leite na raça holandesa

Abstract

RESUMO -O objetivo deste trabalho foi avaliar os efeitos dos períodos de serviço anterior e corrente e do período seco anterior ajustados simultaneamente como efeitos fixos em modelo de touro para produção de leite até 305 dias, contendo ainda os efeitos fixos de rebanho-ano-estação, grupo genético e idade da vaca e os efeitos aleatórios de touro e vaca. Foi usada matriz de parentesco, que incluiu o touro, o seu pai e sua mãe. O mesmo modelo com exclusão da idade da vaca foi usado para produção de leite até 305 dias ajustada à maturidade. As soluções nas análises foram obtidas usando-se o método da máxima verossimilhança restrita e o algoritmo livre de derivada. Polinômios ortogonais foram ajustados para suavização das soluções. Soluções e valores previstos para produção até 305 dias não foram apresentados, por terem seguido mesma tendência da produção até 305 dias ajustada à maturidade. A produção até 305 dias ajustada à maturidade aumentou 950 kg, quando o período de serviço anterior variou de 20 a 300 dias. Este aumento foi de 802 kg para a mesma variação do período de serviço corrente. Vacas com período seco de 60 a 80 dias obtiveram a produção de leite mais alta na lactação seguinte. Valores estimados da heritabilidade foram 0,02 para o período de serviço e 0,08 para o período seco, quando a produção total foi considerada no modelo, e 0,12 quando foi excluída. Fatores multiplicativos foram estimados para o ajustamento da produção de leite para os efeitos de período de serviço e seco.Palavras-chave: fatores de ajustamento, período de serviço, período seco, produção de leite, raça holandesa Effects of the Previous and Present Days Open and of the Previous Dry Days Period on the Milk Production of the Holstein BreedABSTRACT -The objective of this work was to evaluate the effects of previous and present days open and previous dry days period fitted simultaneously as fixed effects using a sire model for 305-day milk production, still containing the fixed effects of herdyear-season, genetic group, age of cow and the random effects of sire and cow. An additive relationship matrix that included the bull, its sire and its mother was used. The same model with the exclusion of the age of cow was used to the milk production adjusted to a 305-day mature equivalent basis The analysis solutions were obtained using derivative free restricted maximum likelihood. Solutions were smoothened with orthogonal polynomials. Predicted values for 305-day milk production were not presented because they followed the same trend as did milk production adjusted to a 305-day mature equivalent basis. As previous and present days open increased from 20 to 300 days, the milk production increased 950 and 802 kg, respectively. Cows with days dry between 60 to 80 days obtained higher milk production in the following lactation. Heritability estimates were .02 for days open and .08 for days dry, when total milk production was considered in the model, and .12 when it was excluded. Multiplicative adjustment factors were developed to adjust productio...

The relationship between dry period length and milk production of Holstein dairy cows in tropical climate: a machine learning approach

“…In our study, it was estimated that milk production after a zero-and a 30-d dry period were 4% (323 kg) and 1% (35 kg), respectively, lower than 50 d, which was found to be the length with the highest milk yield. Our results were lower that what was found by Teixeira et al (1999), who reported a reduction of 438 and 421 kg on 305-d milk yield of cows with a dry period of 30 and 0 d compared to a more conventional 50-d dry period length under tropical climate. Studies conducted under more mild climates reported a reduction on milk yield associated with shorting the dry period ranging from 1 to 18% (Bachman and Schairer, 2003;Annen et al, 2004a).…”

“…Our results were lower that what was found by Teixeira et al . (1999), who reported a reduction of 438 and 421 kg on 305-d milk yield of cows with a dry period of 30 and 0 d compared to a more conventional 50-d dry period length under tropical climate. Studies conducted under more mild climates reported a reduction on milk yield associated with shorting the dry period ranging from 1 to 18% (Bachman and Schairer, 2003; Annen et al ., 2004a).…”

“…The economic implication of the reduction or extension of the dry period not only depends on the volume of milk produced, but also its composition. In addition to the reduction of production associated with short dry periods, our results also indicated a negative relationship between long dry periods and milk production and its components, which is similar to what has been previously reported (Teixeira et al ., 1999; Bachman and Schairer, 2003; Kuhn et al ., 2006). No revenue is generated from milk selling while the animal is dry and an unnecessarily long dry period would have a negative impact on profitability (Delgado et al ., 2017).…”

“…For instance, the regeneration of the mammary gland epithelial tissue during the dry period might be delayed or compromised by high environment temperatures, potentially having a negative effect on milk production (Fabris et al ., 2019). The available evidence indicates a negative association of dry periods shorter or longer than 60 to 79 d with milk production (Teixeira et al ., 1999), but the relationship with milk components still requires evaluation, especially considering the implementation of genetic selection programmes for milk production (Boligon et al ., 2005; Canaza-Cayo et al ., 2016). Therefore, it is necessary to evaluate the relationship between the dry period length and milk production, but also its components in animals kept under tropical conditions to establish an ideal duration to maximize production.…”

Fatores de variação e parâmetros genéticos dos períodos de serviço e seco em bovinos da raça Holandês no estado de Minas Gerais

“…Estes menores valores parecem estar relacionados às melhores condições de manejo nutricional e reprodutivo proporcionados. O PS médio encontrado para as vacas de alto nível de produção assemelha-se ao verificado por TEIXEIRA et al (1995), o qual foi de 80 dias.…”