Relationship between Major Mineral Balance and Milk Yield of Lactating Cows at Thermal Neutrality Zone

Abstract

Four lactating Holstein cows were housed in two independently controlled climatic rooms, where the temperature was kept at 18°C and the relative humidity was maintained at 60% constantly. Lactating cows were fed concentrate, beet pulp, Fall Panicum silage, and corn silage and the ratio of roughage to concentrate was 1:1. The experiment was done by Youden square design for 2 weeks per treatment, in which 4 feeding levels (0, 30, 50 and 70% of the total roughage DM) of Fall Panicum silage were provided. Major mineral concentration in Fall Panicum silage was higher than that in corn silage, but dietary levels of major minerals were almost adequate for lactating cows. There was a significant negative correlation (P⟨.05) between Ca concentration in milk and milk yield, and also a significant negative correlation (P⟨.01) between P or Mg concentration in milk and milk yield. Also, there was a significant negative correlation (P⟨.05) between Ca retention and milk yield, and significant positive correrations (P⟨.05) between Ca absorption and P absorption and between Ca retention and P retention. It is suggested that Ca and P stores in the body of lactating cow may be utilized for their requirement at the stage of high milk yielding in order to supply the lack of Ca and P intake from the feed and at the stage of decreased milk yield Ca and P may be recovered in the body. Since Mg and Na intakes of lactating cows were higher than their requirements, Mg and Na retentions were positive. Also, K retention of lactating cows tended to decrease when corn silage was fed at high level, because K concentration in corn silage was low.