Effects of dietary energy and protein sources and sprinkler treatment on milk yield and milk composition of dairy cows under high temperature

Jury : Prof. Dr. Hasan Rüştü KUTLU: Prof. Dr. Murat GÖRGÜLÜ: Prof. Dr. Kemal ÖZKÜTÜK: Prof. Dr. Behiç ÇOŞKUN: Asst. Prof. Dr. A. Galip ÖNALIn the present study three trials were conducted to evaluate effectiveness ofmanagement and nutritional practices on milk yield and composition, and physiologicalresponses of heat-stressed dairy cows. The experiments were carried out in 2x2 factorialarrangement in a 4x4 Latin Square design. In the first experiment, which were carried out in2002, sprinkler+fan (SF) and protected fat inclusion in the diet (PF, 2.54% on DM basis)were tested. In the second experiment, which were carried out in 2002, SF and fish mealinclusion (FM, 3.67% on DM basis) in the diet were tested. In the third experiment, whichwere carried out 2003, effects of soya bean oil (SBO, 3.81% on DM basis) and fish meal(FM, 3.67% on DM basis) inclusion in the diet were tested.In the experiment 1 and 2, the cows received mild heat stress for 9 h and moderateheat stres for 7 h. SF decreased (P<0.05) rectal and skin temperature and respiration rate. SFimproved milk yield for 1.22 kg in the first trial (P=0.17) and 2.21 kg in the second trial. PFincreased FCM and fat yield (P<0.05) and tended to increase milk yield (P=0.15) and fatcontent (P=0.07). FM had no effect on milk yield but tended to increase milk protein contentand totol N (P=0.12).The cows in the trial 3 received mild heat stress for 14 h and moderate heat stress 10h. SBO increased rectal temperature, respiration and heart rates 0.14ºC, 8.94 number/secondand 2.13 number/second, respectivelly. Additionally, SBO increased milk yield (P<0.01) for1.04 kg but decreased milk fat content (P<0.05) for %18.27. Milk yield was not affected byFM, but BW gain was increased by FM (P=0.09).It could be concluded that applying management practices e.g. sprinkler+fan couldminimize negative influences of heat stress more effective than nutritional manipulation. Theresults also suggested that fat inclusion could be more beneficial than rumen undegradableprotein (fish meal) inclusion in the diet under heat stress.Key Words: Heat stress, fat, fish meal, sprinkler+fan, coolingII