The effects of high rates protected fat in rations of high yielding dairy cows on production efficiency and digestibility

Abstract Text: Due to the rise in grain price, there is an increased use of fat in rations of dairy cows in Israel; however, the effects of high rates have never been examined in the Israeli rations. Therefore, the objectives were to determine the effects of increasing rate of calcium soap of fatty acids (CSFA) on yields, efficiency and digestibility. Forty-two multiparous dairy cows were divided into 3 treatment groups according to milk, parity and days in milk (DIM), and fed diets containing: (i) Low fat (LF) – 4.7% ether extracts (EE; 1.7% CSFA); (ii) Moderate fat (MF)- 5.8% EE (2.8% CSFA) and (iii)  High fat (HF) - 6.8% EE (3.9% CSFA). The diets were isonitrogenous (16.5%), but energy content was 1.8 in the HF compared to 1.78 Mcal/kg DM in the LF and MF diets. Rumen samples were taken 3 times in one day (2 h pre-feeding, at feeding and 2 h post-feeding) for pH and rumen measurements. The data were analyzed using the PROC MIXED model of SAS and the model included parity, DIM and related covariate data. No differences were observed in milk and FCM (4%) yields, or fat and lactose percentages and yields among groups. A trend of decreased protein percentage in milk with increasing EE content in diet was observed (P< 0.08), and higher protein yields were observed in LF and MF than in HF. No differences were observed in dry matter intake (DMI) or energy intake among groups. Efficiency of converting DMI to milk was also similar, but conversion of DMI into FCM (4%) was higher in MF and HF than in LF. Rumen pH was higher in MF and HF than in LF, with no differences in rumen ammonia concentrations. Total VFA concentration in rumen was higher in LF than in MF and HF groups, and apparent digestibility of DM and organic matter (OM) was higher in the LF than in both other groups. In conclusion, although apparent digestibility of DM and OM was lower in MF and HF, no detrimental effects of high rate of CSFA supplementation (up to 3.9% of the diet) on milk yields and efficiency were observed.

Keywords: CSFA, Digestibility, Efficiency