Effects of Dietary Starch and Crude Protein Levels on Milk Production and Composition of Dairy Cows Fed High Concentrate Diet

Abstract

Effects of two dietary levels of starch and crude protein on performance of dairy cow fed low roughage level (70:30 concentrate to roughage) were investigated. Twenty eight Holstein cows were randomly assigned to one of four dietary treatments in a 2 x 2 factorial arrangement. Factors were two dietary level of starch (14% and 22%) and crude protein (15% and 18%). Wheat straw was used as sole roughage source. The study was continued 6 weeks. Dry matter intake was not affected (P>0.05) by the dietary treatments in the study. Milk and protein yield (kg/d) were higher (P<0.05) with higher dietary crude protein level at each starch level. Milk urea concentrations were affected (P<0.01) by dietary protein levels with a value being higher by high dietary protein level. Nitrogen efficiency (Milk N/N intake) was decreased by increasing dietary crude protein level in the diet (P< 0.01). In conclusion, the cows fed TMR containing low level of wheat straw responded better when dietary protein increased. But, efficiency of N use decreased and N excretion to the environment increased.