Effects of bypass fat on energy balance, milk production and reproduction in grazing crossbred cows in the tropics

This study was designed to investigate the effects of supplementation with a calcium soap of long chain fatty acids (ByFat ®) on energy balance, milk production and reproduction of suckling crossbred cows, grazing star grass in the tropics. ByFat was supplied at 1.8% of estimated dry matter intake (3% of live weight). Twenty-four cows were used in a 2 × 2 × 2 factorial design from calving to 98 days postpartum. Treatments were control (C) vs. ByFat, dry vs. rainy season, and primiparous vs. multiparous cows. There was no interaction between season or parity and diet. Milk yield was not different between diets (12.1 kg/day for ByFat, 11.7 kg/day for C), although cows fed ByFat were more persistent and lost body condition at a faster rate than control cows. ByFat had no effect on reproductive performance, possibly due to reduced grass DM intake (8.80 vs. 10.70 kg/day), which resulted in no treatment difference in energy balance or metabolic hormones. It was concluded that supplementation with a calcium soap of long chain fatty acids is not effective for improving energy balance or reproductive performance in low-merit grazing cows in the tropics.