Effect of Feeding Silage of Early and Late Maturing Corn Planted at Two Population Densities to Lactating Dairy Cows

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Abstract
In two experiments, 36 multiparous Holstein cows were used to evaluate silages from early or late maturing hybrid corn, each planted at two population densities, 75,000 and 150,000 plants/ha. Silages in Experiment 1 were 1) an early and 2) a late maturing corn planted at 75,000 plants/ha, and in Experiment 2 1) an early and 2) a late maturing corn were planted at 150,000/ha. Cows in Experiment 1 were group-fed a total mixed ration in a 50:50 concentrate:forage ratio, whereas in Experiment 2, cows were individually fed a total mixed ration in a proportion of 60:40. In both experiments 75% of the forage was corn silage. Cows fed the rations containing the early and late corn planted at 75,000 plants/ha had similar milk production, composition, DM intake, efficiency of milk production, rumen pH, and concentration of NH3 N and VFA. Cows fed the rations containing the early corn at 150,000 plants/ha had higher total milk production, DM intake, and total rumen VFA concentration than cows fed the late corn. Cows fed the late corn had higher milk fat test and feed efficiency. No differences were observed for milk protein, BW, rumen pH, and NH3 N. If corn is planted at high population densities, it may be advantageous to plant a late hybrid. At low population densities the nutritive value for both hybrids was similar.