Brown midrib sorghum in diets for lactating dairy cows

In Experiment 1, 16 Holstein cows were assigned to one of four diets in rep licated 4 x 4 Latin squares with 4-wk periods to measure dietary effect on short-term lactational performance. Additionally, 3 fistulated cows were as signed to the same diets in a 3 x 4 Youden square design with 4-wk periods to measure ruminal rate and extent of fiber digestion, fractional passage r ate of fiber, ruminal pH, and concentration of volatile fatty acids. Diets comprised 65% of brown midrib (BMR) forage sorghum, standard forage sorghum , alfalfa or corn silages and 35% concentrate. Experiment 2 was conducted w ith 30 Holstein cows in early lactation to evaluate the same BMR sorghum hy brid in a 10-wk study with 35.3% standard sorghum, BMR sorghum, or corn sil ages as dietary treatments. Milk production was significantly higher for br own midrib than for standard sorghum in Experiment 1. Ruminal pH and acetat e to propionate ratio did not differ among diets. The fractional passage ra te of silage was not significantly different among the forages. In situ ext ent of ruminal fiber digestion was significantly higher for BMR than for st andard sorghum, but rate of fiber digestion was not different. Similarly, i n Experiment 2, in vitro extent of fiber digestion was significantly higher for BMR sorghum than for standard sorghum. Dry matter intake and body cond ition score were not significantly different between cows fed BMR and stand ard sorghum, but cows fed BMR sorghum resulted in long-term milk production greater than cows fed standard sorghum and similar to cows fed corn silage .