| Popis: |
Thirty-six lactating Holstein cows (80 DIM) were divided into four groups to compare steam-rolled corn with a density of 489g/L, steam-flaked sorghum grain (360g/L), dry-rolled sorghum grain (643g/L), and an equal mixture of dry-rolled and steam-flaked sorghum grain. Each grain treatment constituted 42% of the TMR. A 14-d pretreatment period was used to allot cows to treatment and to adjust treatment means by covariance analysis. Treatment was for 80 d and included a 14-d digestibility trial using Cr 2 0 3 as a marker. Intake of DM was higher for mixed than for flaked sorghum. Milk yield, FCM yield, and milk fat percentage were not altered by treatment, but cows fed steam-flaked sorghum had higher percentages of protein, lactose, and SNF in milk and greater milk protein yield than those fed dry-rolled sorghum. Percentages of milk lactose and SNF were greater for cows fed flaked sorghum than for those fed steam-rolled corn or the sorghum mixture. Digestibility of OM was higher for flaked sorghum than for steam-rolled corn or rolled sorghum, and digestibilities of CP and NDF were highest for dry-rolled sorghum. Total tract starch digestibility was lowest for cows fed dry-rolled sorghum (70%), highest (92%) for those fed steam-flaked sorghum, and intermediate (82%) for those fed rolled corn and the sorghum mix. Milk yield for cows fed steam-flaked sorghum grain was equal to or superior to that of cows fed steam-rolled corn. Steam flaking of sorghum grain markedly increased starch digestibility and percentage milk protein compared with dry rolling. |
