Responses of Dairy Cows Fed Alfalfa Silage Supplemented with Phosphorus, Copper, Zinc, and Manganese

Abstract

Thirty-three Holstein-Friesian cows (21 multiparous, 12 uniparous) were allocated randomly to three treatments 14 wk prepartum and fed through 22 wk postpartum. Each cow individually was fed alfalfa silage to 2%, dry matter, of body weight and high moisture grain corn to exceed National Academy of Sciences-National Research Council recommendation for energy by 10% and soybean meal to meet that for protein. The basal diet was supplemented with phosphorus, copper, zinc, and manganese to supply either 100%, 150%, or 200% of recommendations for these minerals. A trend for increased dry matter intake and decreased total milk yield caused a slight linear decrease in yield/intake with increased mineral supplementation. However, milk protein percentage increased linearly with increased mineral supplementation, and lactose and fat were unaffected. No reproductive traits differed. There was, however, a trend for cows supplemented with minerals at 200% recommendations to have fewer days to first estrus. Inorganic phosphorus in blood increased linearly with increased mineral supplementation as did retentions of all supplemented minerals. No effects on lactational or reproductive performance were adverse in cows fed alfalfa silage (1.27% calcium, 16.5% crude protein, dry matter basis) as the sole forage. Therefore, supplementation with phosphorus, copper, zinc, and manganese above recommendations may be necessary only when alfalfa silage contains more than 1.5% calcium.