Repeated Ruminal Acidosis Challenges in Lactating Dairy Cows at High and Low Risk for Developing Acidosis: Feed Sorting

Abstract

An experiment was conducted to determine whether the susceptibility of cows to ruminal acidosis influences feed sorting and whether feed sorting changes during a bout of ruminal acidosis. Eight ruminally cannulated cows were assigned to 1 of 2 acidosis risk levels: low risk (LR, mid-lactation cows fed a 60% forage diet) or high risk (HR, early lactation cows fed a 45% forage diet). As a result, diets were intentionally confounded with milk production to represent 2 different acidosis risk scenarios. Cows were exposed to an acidosis challenge in each of two 14-d periods. Each period consisted of 3 baseline days, a feed restriction day (restricting TMR to 50% of ad libitum intake), an acidosis challenge day (1-h meal of 4 kg of ground barley/wheat before allocating the TMR), and a recovery phase. Ruminal pH was measured continuously for the first 9 d of each period using an indwelling system. Feed and orts were sampled for 2 baseline days, on the challenge day, and 1 and 3 d after the challenge day for each cow and subjected to particle size analysis. The separator contained 3 screens (18, 9, and 1.18 mm) and a bottom pan to determine the proportion of long, medium, short, and fine particles, respectively. Sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. All cows sorted against the longest and finest TMR particles and sorted for medium-length particles. Sorting was performed to a greater extent by the HR cows, and this sorting was related to low ruminal pH. Both HR and LR cows altered their sorting behavior in response to acidosis challenges. For the HR cows, severe acidosis was associated with increased sorting for the longer particles in the diet and against the shorter particles, likely to lessen the effects of the very.

Feeding amount affects the sorting behavior of lactating dairy cows

“…Researchers have previously shown that dairy cows experiencing both acute and chronic bouts of SARA will sort for the longer ration particles and against the shorter ration particles (Yang and Beauchemin 2006;DeVries et al 2008). Given the small amount of long forage particles (B5% of the ration) compared with recommended values (Heinrichs 1996), it is possible that the ration used in the current study caused some degree of SARA.…”

Effect of forage particle length on rumen fermentation, sorting and chewing activity of late-lactation and non-lactating dairy cows

“…Typically cows will sort rations against longer particles and in favor of shorter particles and to a greater degree in rations with greater particle length (Leonardi and Armentano, 2003;Maulfair et al, 2010). However, opposite sorting behavior has been observed in induced severe acidosis where cows sorted against shorter particles (DeVries et al, 2008).…”

Behavioural adaptations of sheep to repeated acidosis challenges and effect of yeast supplementation

“…A recent experiment studied the effects of three repeated acidosis challenges on eight dairy cows fed with total mixed ration (TMR; DeVries et al, 2008;Dohme et al, 2008). The cows had a high or low risk for experiencing acidosis because of their diet and stage of lactation.…”

“…Devries et al (2008) found that cows exposed to two 1-day acidosis challenges at a 14-day inter-challenge interval sort their food in favour of longer particles, especially during the second challenge, but no other behavioural measurements were performed. Behavioural adaptations may reduce the effects of diets carrying high acidosis risk.…”