Nonstructural carbohydrate and protein effects on rumen fermentation, nutrient flow, and performance of dairy cows.
Four multiparous Holstein cows fitted with rumen and duodenal cannulas were used in a 4 x 4 Latin square with 20-d periods. Four diets were formulated for high and low rumen availabilities of nonstructural carbohydrate and protein. Cows were milked and fed three times daily. Milk production averaged 39 kg/d and was unaffected by treatment. Dry matter intake and 4% FCM production were increased by 1 kg/d for cows fed the low rumen-available nonstructural carbohydrate diets. Milk protein percentage was elevated when either the high rumen-available nonstructural carbohydrate or high rumen-available protein diets were fed. Low rumen-available protein diets increased duodenal passage of total essential AA but did not increase passage of Arg, Ile, and Met. Passage of bacterial N was highest (262 g/d) when high rumen-available nonstructural carbohydrate was combined with high rumen-available protein and was lowest when high rumen-available nonstructural carbohydrate was combined with low rumen-available protein (214 g/d). Diets with low rumen availabilities of protein were not advantageous, possibly because duodenal passage of one or more of the limiting AA was not increased. Passage of bacterial N to the duodenum was highest when rumen availabilities of both nonstructural carbohydrate and protein were high.
Department of Dairy and Animal Science, Pennsylvania State University, University Park 16802.
J M
JM
Aldrich
L D
LD
Muller
G A
GA
Varga
L C
LC
Griel
D000596:Amino Acids / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000502:physiology*; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D004043:Dietary Fiber / Q000008:administration & dosage / Q000378:metabolism; D004044:Dietary Proteins / Q000494:pharmacology*; D004386:Duodenum / Q000378:metabolism / Q000382:microbiology; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005260:Female; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007774:Lactation; D009584:Nitrogen / Q000378:metabolism; D012417:Rumen / Q000382:microbiology / Q000502:physiology*
D000596:Amino Acids; D001426:Bacterial Proteins; D004040:Dietary Carbohydrates; D004043:Dietary Fiber; D004044:Dietary Proteins; D005232:Fatty Acids, Volatile; D000641:Ammonia; D009584:Nitrogen