Milk production and composition, rumen fermentation parameters, grazing behavior of dairy cows supplemented with different forms and amounts of corn grain

The objectives were to compare milk production and composition, change in b ody weight and body condition score, lumen fermentation parameters and graz ing patterns by cows when supplemented with different forms and amounts of corn grain. In experiment 1, 36 Holstein cows were supplemented with either 6, 6, 6, or 4 kg/d of dry matter of high moisture corn, coarsely ground co rn, finely ground corn, or high moisture corn in two equal daily feedings, respectively. Milk yield (30.3 kg/d), milk protein (2.97%), and milk urea N (14.7 mg/dl) were not different among treatments. Body weight change and b ody condition score change were similar (23.1 kg and -0.24) for the 10-wk s tudy. During experiment 2, four rumen cannulated cows in midlactation were supplemented with 6 kg/d of dry matter from either coarsely ground corn or high moisture corn in two equal feedings after milking. After the p.m, milk ing, ruminal pH was measured and rumen fluid samples mere collected from co ws to determine ammonia N and volatile fatty acids at 0.5, 1, 2, 3,...8 h p ost-corn feeding during grazing. Ruminal pH values were similar for corn su pplements, and, with one exception, were 6.0 or below between 5 and 8 h. Ru minal ammonia-N concentrations reached a maximum at 7 h also. In experiment 3, 40 cows were observed for grazing behavior every 30 min for two consecu tive days. Cows grazed an average of 6.4 h/d, 4.1 h in the afternoon and 2. 3 h in the morning. Milk yield, milk composition, change in body weight, an d body condition were similar regardless of the type or amount of corn supp lemented.