Effects of diet particle size and supplemental hay on mitigating subacute ruminal acidosis in high-producing dairy cattle.

摘要

Achieving maximum milk production in dairy cows increases the risk of subacute ruminal acidosis (SARA), a severe digestive disorder that is an economic concern for producers. High-producing dairy cattle require more dietary energy in order to meet the demands of increased milk production. High energy diets, however, are low in physically effective NDF (peNDF) and high in starch. Starch sources in the diet are often processed in a manner to optimize starch availability in the rumen and the fiber sources are often highly digestible and short in particle length. As a result, these types of diets are highly fermentable in the rumen and often lack the structural characteristics needed to maximize rumination time and the flow of salivary buffers into the rumen. The result is reduced pH in the rumen and increased risk of acidosis. While it is critical to meet the energy requirements of high-producing cows, acidosis must be avoided to ensure high milk production and efficient use of feed. There is growing evidence that dairy cows will select feeds with high ruminal buffering capacity in an attempt to attenuate the effects of low ruminal pH. Four experiments were carried out on early to mid-lactation Holstein dairy cows to investigate the effects of corn silage particle size and supplemental hay on feed preference, ruminal fermentation, dry matter intake, and milk yield and components during an induction of SARA. Together, these experiments provide valuable observations in regards to feeding supplemental hay as a nutritional management strategy to mitigate SARA. Feeding supplemental long hay to high-producing dairy cattle experiencing SARA was found to be beneficial and helped maintain dry matter intake, alleviate low ruminal pH, and blunted the shift of FA towards trans-10, C18:1. In addition, when fed with short cut corn silage, providing long supplemental hay helped accelerate recovery from SARA.;Key words: subacute ruminal acidosis, particle size, dry matter intake, diet selection, ruminal pH.