WAXY CORN AS A REPLACEMENT FOR DENT CORN FOR LACTATING DAIRY-COWS

Waxy and dent corn starch differences were compared in diets of early lactating dairy cows. Thirty multiparous Holsteins averaging 568 +/- 7 6 kg body weight (BW) and 50 +/- 24 d in lactation were randomly assig ned at two locations to three treatments to evaluate: (1) the extent t o which replacing dent corn in the diet with recently developed waxy h ybrids affects milk yield and composition; and (2) to document changes in the concentration of blood and ruminal metabolites of dairy cattle fed waxy corn compared to dent corn. A 3 X 3 Latin square design was used to test the treatments: control, (100% dent corn in grain mix), d ent + waxy (50% dent and 50% waxy corn in grain mix), and waxy corn (1 00% in grain mix). Total mixed rations (TMR) formulated to be isonitro genous at 17.2% crude protein and isocaloric at 1.72 Meal net energy f or lactation per kg of DM, were fed twice daily to individual cows in Calan gates (North Dakota State University Dairy Research Center) or i n tie stalls (University of Minnesota, Crookston Dairy Research Center ) for 15 weeks. Rumen, blood and milk samples were collected during th e fifth week of each period. Ruminal acetate, isobutyrate, isovalerate and total volatile fatty acid (VFA) concentrations were lower (P < 0. 05) when waxy corn was added to the diet. Serum urea nitrogen and milk fat percentage were decreased (P < 0.05) in rations where the grain c oncentrate was comprised of waxy corn. Blood glucose and insulin conce ntrations were unchanged (P > 0.05) by treatment. There was no differe nce in milk yield or total milk solids indicating similar lactational performance among treatments using waxy and dent corn. (C) 1998 Elsevi er Science B.V.