heat stress

protected fat

fish meal

sprinkler+fan

cooling

Two studies were conducted to evaluate 1. the effectiveness of sprinkler+fan (SF) and fish meal (FM) and 2. SF and protected fat (PF) in alleviation of heat stress in dairy cows in mid lactation. The studies were carried out in 2 × 2 factorial arrangement, in a 4 × 4 Latin square design on four multiparous lactating dairy cows. The treatments in the first trial were 1. no SF and no FM, 2. no SF and 3.67% FM in the diet (on DM basis), 3. SF and no FM and 4. SF and 3.67% FM. The treatments in the second trial were 1. no SF and no PF, 2. no SF and 2.54% PF in the diet (on DM basis), 3. SF and no PF and 4. SF and 2.54% PF. Cows were fed with isoenergetic and isonitrogenic TMR, containing 2.52 Mcal ME/kg DM and 180 g CP/kg DM. The cows received mild heat stress for 9 h (from 07.00 to 10.00 and from 17.00 to 23.00) and moderate heat stress for 7 h (from 10.00 to 17.00) daily for the entire experimental period. SF decreased (P<0.05) rectal and skin temperature and respiration rate. SF improved milk yield for 2.21 kg in the first trial (P<0.07, 19.24 vs 21.45 kg d^-1) and 1.22 kg in the second one (P=0.15, 19.47 vs 20.69 kg d^-1). FM had no effect on milk yield of neither cooled nor no cooled cows, but tended to increase (P=0.12) milk protein, independently from SF application. Additionally, PF increased FCM and fat yield (P<0.05) and tended to increase (P=0.07) milk fat content independently from SF application. The results of both studies suggest that applying sprinklers plus fan can improve milk yield better than nutritional manipulation using either FM or PF. The results also suggested that PF could be more beneficial than FM under heat stress condition when the dietary protein level is high.