Corn grain endosperm type and brown midrib 3 corn silage: ruminal fermentation and N partitioning in lactating cows.
Interactions of endosperm type of corn grain and the brown midrib 3 mutation (bm3) in corn silage on ruminal fermentation and microbial efficiency of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72 +/- 8 d in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design experiment with a 2 x 2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous) and corn silage type (bm3 or isogenic normal). Diets contained 26% neutral detergent fiber and 30% starch. Increasing ruminal starch digestibility by replacing vitreous corn grain with floury grain reduced mean and minimum ruminal pH. Brown midrib 3 corn silage reduced mean and minimum ruminal pH and increased total volatile fatty acid concentration. Ruminal pH was positively associated with rate of valerate absorption. Although floury endosperm reduced acetate:propionate ratio in both control and bm3 corn silage diets, it had a greater effect on reducing acetate:propionate ratio for control silage compared with bm3 corn silage. Nonammonia N flow to the duodenum did not differ among treatments and no effects of treatment were detected for microbial N and nonammonia, nonmicrobial N flow. Although treatment effects on ruminal fermentation and ruminal pH were observed, few interactions of treatment were detected and treatments did not affect flow of N fractions to the intestines.
Taylor
C C
CC
Department of Animal Science, Michigan State University, East Lansing 48824-1225, USA.
Allen
M S
MS
D000818:Animals; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D004043:Dietary Fiber / Q000008:administration & dosage / Q000378:metabolism; D004063:Digestion; D004386:Duodenum / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000032:analysis / Q000378:metabolism*; D005260:Female; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007774:Lactation / Q000378:metabolism / Q000502:physiology; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism*; D011897:Random Allocation; D012417:Rumen / Q000737:chemistry / Q000378:metabolism / Q000382:microbiology*; D012820:Silage; D013213:Starch / Q000008:administration & dosage / Q000378:metabolism; D003313:Zea mays / Q000235:genetics*
D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D013213:Starch; D009584:Nitrogen