Effects of Saccharomyces cerevisiae fermentation products (SCFP) and subacute ruminal acidosis (SARA) on feed intake, milk production and component, and fermentation in lactating dairy cows
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Date
2020
Authors
Khalouei, Hamidreza
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Abstract
The effects of two Saccharomyces cerevisiae fermentation products (SCFP) and subacute ruminal acidosis (SARA) challenges on the dry matter intake (DMI), milk production, feed efficiency (FE), calculated as the ratio of the FCM and the DMI, rumen fermentation, and feces composition were determined in 32 lactating Holstein cows. Cows were assigned to four treatments including three SCFP supplementations as follows: i) control; ii), ii)14 g/d Diamond V Original XPC™ (XPC, Diamond V, Cedar Rapids, IA), iii) 19 g/d NutriTek® (NTL, Diamond V, Cedar Rapids, IA), or iv) 38 g/d NutriTek® (NTH, Diamond V, Cedar Rapids, IA) that started 28 d before the expected calving dates. Cows were monitored from wk 4 to wk 9 of lactation. The volume and kinetics of liquid rumen digesta were determined during wk 11. SARA challenges were conducted during wk 5 and wk 8 by switching from a moderate starch (18.6 % DM) to a higher starch (27.9 % DM) diet. These challenges increased the DMI, and the yield of milk and milk protein, but reduced the milk fat yield, the 3.5% fat corrected milk yield (FCM), and feces pH. The challenges also increased the rumen concentrations of propionate, butyrate and total VFA, and reduced those of acetate and ammonia-nitrogen. The SARA challenges only increased the duration of the rumen pH below 5.6 to more than 180 min/d, which was considered the threshold for SARA, in cows receiving the Control, XPC, and NTL treatments. However, even under these treatments, the rumen pH depression was mild. The first and second SARA challenge did not differ in the severity of the depression of rumen and feces pH, but the FE was lower during the second SARA challenge than during the first. The volume and kinetics of liquid rumen digesta were not affected by SCFP treatment.
Fecal pH was the lowest during the NTH treatment, suggesting this treatment shifted the fermentation of starch out of the rumen. The NTL and NTH treatments reduced milk yield, the XPC treatment had a lower milk fat content than the NTH treatment, and the NTL treatment tended to reduce the FCM. Despite this, the SCFP treatments did not affect the FE, calculated as the ratio of the FCM and the DMI. Results show that the NTH treatment attenuated adverse impacts of grain-based SARA on the conditions in the rumen, without reducing milk production, and that repeated SARA challenges may increase the effect of such a challenge on the FE.
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Keywords
Dairy cows, SARA, Saccharomyces cerevisiae fermentation products