Journal of Animal Science, Vol 72, Issue 1 220-228, Copyright © 1994 by American Society of Animal Science

JOURNAL ARTICLE

Influence of sugary-Brawn2 or dent corn at two forage levels on intake, digestion, and milk production by dairy cows

M. C. Willcox, R. D. Shaver, J. G. Coors and K. K. Batajoo
Department of Agronomy, University of Wisconsin, Madison 53706.

Sugary-Brawn2 (su-Bn2) corn endosperm contains higher concentrations of watersoluble polysaccharides than dent corn. Eight multiparous Holstein cows averaging 48 d in milk and 667 kg BW at trial initiation were in a replicated 4 x 4 Latin square design with 28-d periods. Only cows in one square were ruminally cannulated. Treatments were su-Bn2 or dent corn and 45 or 60% of ration DM as alfalfa silage arranged as a 2 x 2 factorial within each square. Diets, formulated to contain 19% CP, were fed as total mixed rations twice daily. Intake of DM and milk yield averaged 26.8 and 39.9 kg/d, respectively, and were not affected by treatment (P > .10). Sugary-Brawn2 corn decreased milkfat percentage (3.27 vs 3.45%), particularly for the low-forage diet (3.15 vs 3.40%). Milk protein percentage was higher (3.15 vs 3.10%) for low-forage diets but was not affected (P > .10) by corn type. Ruminal pH was lower for low-forage diets. Feeding su-Bn2 corn decreased ruminal pH only at 4 h after feeding. Total VFA in ruminal fluid (millimolar) 6 h after feeding were higher, whereas acetate molar percentage and acetate:propionate ratio were lower for su-Bn2 corn. Ruminal in situ evaluation of su-Bn2 and dent corn revealed a larger soluble fraction, a faster rate of degradation, and higher availabilities of both DM and starch for su-Bn2 corn. Ruminal in situ rate of degradation and availability of alfalfa hay DM were reduced by su-Bn2 corn. Total tract apparent digestibilities of DM, CP, and starch were greater for su-Bn2 diets.(ABSTRACT TRUNCATED AT 250 WORDS)