The effect of nutritional management of dairy cows post-calving and yeast supplementation on milk fatty acid profiles in the first eight weeks of lactation

ALIBRAHIM, R., F. M. MULLIGAN, R. A. PALLADINO, AND K. M. PIERCE

Northen Ireland

Congreso; Advances in Animal Biosciences; 2010

BSAS

Introduction: There is increased focus on earlier turnout of cows to pasture post-calving. However, nutritional management of cows in early lactation can influence milk production and milk composition throughout lactation.  Through effects on rumen pH (Dawson and Hopkins, 1991), yeast supplementation (YS) may influence biohydrogenation of fatty acids (FA) in the rumen and therefore, milk FA profiles. The objective of this experiment was to evaluate the impact of nutritional management of the dairy cow in early lactation on subsequent milk FA profiles. This research is part of a larger study investigating the effect of abrupt introduction of cows to pasture immediately at calving with a more gradual introduction to pasture, and the effect of dietary YS (Yea-Sacc1026 TS, Alltech, INC., Nashville, KY, USA) on rumen physiology at this time. Materials and Methods: The experiment was designed as a 2x2 factorial (grass vs TMR in early lactation +/- YS). The yeast was offered at 10g/hd/d x 108 CFU of live strain S. cerevisiae1026/g, Yea-Sacc1026 TS. Treatments were: 1) Abrupt introduction to pasture post-calving (AP) + YS; 2) AP - YS; 3) TMR for 21 days post-calving (TMR21) + YS and 4) TMR21 - YS. In the dry period (60 days pre-calving) all cows were fed grass silage (GS) ad-libitum. The TMR was provided ad libitum and consisted of 50% maize silage, 45% GS, and 5% wheat straw, and 8 kg concentrate +/- YS. At day 22 post calving, TMR21 cows (+/- YS) received the same diets as AP (+/- YS) cows. Pasture allowance of 20 kg DM/hd/d (measured at a cutting high of 4 cm) was maintained across the trial period. Grazing cows were supplemented with concentrate (+/- YS) at rate of 4 kg/hd/d. Cows were milked x2 daily, and milk yield was recorded at each milking. Milk samples were collected weekly for an 8 week period and were mixed according to their am and pm yield. Feed and milk FA were analyzed by GC according to Palladino et al. (2009). Data were analyzed using PROC MIXED of SAS. Results: Cows fed TMR21 had higher short chain FA (SFA) (P<0.01) and medium chain FA (MCFA) (P<0.05) whilst unsaturated FA(UFA) (P<0.05), UFA:SFA (P<0.01), and long chain FA (LCFA) (P<0.05) were lower compared to AP cows (Table 1). Cis-9 C18:1 was in also higher in milk from AP cows. Yeast supplementation had no effect on milk FA profiles in the current experiment and there was no interaction between diet and YS. Conclusions: Dietary management in early lactation influenced milk fatty acid profiles. Cows offered grass immediately post-calving had higher LCFA, lower SFA, MCFA and UFA:SFA compared to cows offered TMR for the first 3 weeks post-calving. Yeast supplementation had no effect on milk FA profiles in the current experiment. References: Dawson, K. A., and D. M. Hopkins (1991). J. Anim. Sci. 69(Suppl. 1):531. (Abstr.) Palladino, R.A, M. O’Donovan, J. J. Murphy, M. McEvoy, J. Callan, T. M. Boland and D. A. Kenny (2009). J. Dairy Sci. 2009. 92:5212-5223 Statistical Institute. 2006. Users Guide: Statistics. Version 9.1. SAS Institute, Cary, NC.