Influence of particle size on the effectiveness of the fiber in barley silage

We used eight multiparous Holstein cows in a 4 x 4 Latin square design to e valuate the effects and possible interactions between silage particle size and concentrate level on chewing activities and productivity of cows fed ba rley-based total mixed rations (TMR). Diets were designed with two forage-t o-concentrate ratios (low forage, 45:55, high forage 55:45), combined with two theoretical chop lengths of barley silage (short = 4.68 mm and long = 1 8.75 mm). Diets were formulated to provide similar and above-minimum neutra l detergent fiber recommended for cows in early lactation. Increasing silag e particle size of the forage did not affect dry matter intake. The 3.5% fa t-correct milk and fat yields trended higher for increased particle size. P ercent milk protein was higher for short particle size. Increasing the conc entrate levels in the diets increased proportions of milk protein and lacto se, but not milk fat. Cows fed short silage spent 90 min less per day chewi ng and ruminating than did those on long silage. Total chewing activity per kilogram of forage intake was higher for cows on long silage compared with those on short silage diets. Although a reduction in silage particle size did not depress milk fat, rumination and chewing activity were significantl y reduced. These results suggest that particle size of the silage may have dominant control over chewing activity despite adequate neutral detergent f iber intakes.