Abstract: A study was conducted to evaluate the effect of two levels of hay particle size and diet DM on dairy cows performance in barley base diets. Eight cows in early lactation stage were allocated to four dietary treatments in a change over design with factorial arrangement of 2×2 including two levels of alfalfa particle size (5 and 20 mm) and two levels of TMR dry matter (without and with adding water up to 50% DM). Diets were similar in net energy content and chemical composition. Water addition resulted in reduction in percentage of diet particles in the pan and increasing physical effective factor (pef) in both levels of alfalfa particle size (p<0.01). Experimental treatments had no effect on milk production although a trend of milk fat reduction was observed with reduction of the hay particle size (p = 0.06). Milk protein, Lactose and SNF content of the produced milk were not influenced by the treatments. Milk production efficiency was showed a trend to change with diet DM changes (p = 0.06). Blood pH and bicarbonate content, NH3-N concentrations and fecal pH were not affected by the treatments but water addition resulted in significant reduction in ruminal pH (p = 0.02). TMR particle size had no effect on eating time, but in the wet diets a significant reduction in eating time of peNDF (min kg-1) (p = 0.02) and eating time of NDF (min kg-1) (p = 0.05) was found. Conversely hay particle size reduction significantly decreased rumination time when expressed as min day-1 (p = 0.02) and min kg-1 of diet NDF (p<0.01). Treatments had no effect on feces particle size, body weight, DMI and NDF intake by the cows.
A. Hosseinkhani , R. Valizadeh , A. Naserian , M.D. Mesgharan and F.E. Shahroodi , 2007. Effect of Alfalfa Hay Particle Size and Water Addition to Barely Base Diets on Dairy Cows Performance in Early Lactation. Journal of Animal and Veterinary Advances, 6: 1482-1488.