U.S. Dairy Forage Research Center, 1995 Research Summaries Effect of Grinding High Moisture Corn on Its Utilization by Dairy Cows Fed Alfalfa

blood and milk urea, and DM and starch digestion, estimated using indigestible ADF as an internal marker, were determined during the trial. Stimulation of MPS by HMC and GHMC was assessed from ammonia disappearance in duplicate in vitro incubations. Results and Discussion Changes in ammonia concentration in ruminal in vitro incubations conducted with HMC and GHMC are shown in Figure 1. Grinding of HMC significantly (P <.01) decreased ammonia at 3, 4, 5 and 6 h of incubation, presumably by stimulating ruminal MPS. The results from the in vitro incubations reflected those observed in the lactation trial, which are summarized in Table 1. There were no differences in BW gain despite DMI being lower on diet HMC. Grinding of HMC significantly increased digestibility of DM and starch. The higher DMI and improved digestibility were reflected in improved yield of milk and milk components, particularly on diet GHMC; grinding of HMC resulted in equivalent production between diets HMC + E and GHMC. Although there was no difference in milk yield among the HMC + E, GHMC and GHMC + E diets, yields of fat, protein, and SNF were lower on diet GHMC + E than on diets HMC + E and GHMC. This result may have been related to hot weather occurring during the middle four weeks of the 12-week trial and not due to an adverse effect of feeding RUP. During the first four weeks of the trial, cows fed the GHMC + E diet produced more milk than those fed the GHMC diet but, after a four-week heat wave starting in week 5, cows receiving the GHMC + E diet began to decline. This may have resulted from greater incidence of sub-clinical mastitis in cows fed the GHMC + E diet because, by chance, the cows assigned to this diet had higher SCC before the trial. Moreover, their SCC increased more during the trial. As a result, the main effects of ESBM and grinding cannot be seen clearly because the two factors interacted (P =.06). Efficiency of milk yield (weekly milk yield divided by weekly DMI) was not different among the treatments. However, N efficiency was higher for the HMC and GHMC diets than for the tw