Effects of dietary starch and protein levels on milk production and composition of dairy cows fed high concentrate diet

Özet

Abstract Twenty eight Holstein cows (averaged 41±31.5 and 82±24 days in milk, and 30.4±3.49 and 29.0±2.22 kg/d milk yield) were fed a high concentrate diet (70:30 concentrate to forage) to examine effects on milk production and composition. The cows were randomly assigned to receive four dietary treatments according to a 2 x 2 factorial arrangement. Factors were starch (14% and 22%) and protein (15% and 18%). Wheat straw was used as forage source. The study lasted 6 weeks. Dry matter intake was not affected (P> 0.05) by the dietary treatments in the study. Milk yield increased with increased dietary protein level (P< 0.01). Milk urea nitrogen concentrations were affected by dietary protein and starch levels, but there was no interaction effect. Nitrogen efficiency (Milk N/N intake) was decreased by increasing in dietary protein level (P< 0.01). In conclusion, the cows fed total mixed ration (TMR) containing low level of wheat straw responded better when dietary protein increased. But, efficiency of N use and N excretion to the environment were worsened. Key words: Dairy cattle, milk composition, protein, starch, wheat straw