The effects of season, diet selection and production level on feeding behaviour and milk yield properties of dairy cows

The aim of the study was to investigate the effects of season, feeding method and production level on milk yield and composition, and feeding behaviour of dairy cows. Two seasons (winter and summer), two feeding methods (TMR and choice-feeding) and production level (high and low yielding) were tested in a complately randomized design with 2x2x2 factorial arrangement with 5 replicates. TMR was composed with corn, barley, soybean meal, corn gluten meal, wheat bran and alfalfa hay grounded in 1.5-2 cm size (40%). The diet selected by cows had higher ME and lower fiber content due to high preferences to grain and low preferences to alfalfa hay(P<0.05). Dry matter and nutrient intakes were affected by season and intakes were higher for Winter than for Summer (P<0.05). Choice feeding decreased nutrient intake due to changes in diet preferences and low dry mater intake (P<0.05). Production level had significant effects on feed intake as percentage of body weight, milk production efficiency, ME, ADF, NDF and ether extract intakes (P<0.05). High yieding cows had higher values for those parameters than low yielding cows. Main effects had significant effects on milk composition (P<0.05). Solid non fat, protein, casein content during winter were higher than those during summer. Dry matter, fat and urea in milk were higher for cows fed TMR than those of choice fed cows. Solid non fat, protein and casein content were higher for low yielding cows than those high yielding cows while lactose content of milk was lower for low yielding cows than high yielding cows. Season had significant effects (P<0.05) on physiological parameters such as respiration rate, pulse rate, skin temperature and rectal temperature of cows and these walues were higher during summer than during winter. . Feeding behaviour was also affected by season and feeding methods (P<0.05). Meal lenght, total meal lenght, meal size were lower for summer than winter but meal number was higher during summer compared to winter. TMR fed cows had high number of meal than choice fed cows due to low intermeal interval in those cows. Inconclusion, while the cows having different production levels did not change their diet preferences, they changed their total feed intake significantly to control their nutrient intakes. This could be probably resulted from high feed intake capacity of cattle.