Can Nutrition Mistakes in Rearing
Heifers Affect Subsequent Milk Production?
Dr. Ronald L. Boman
USU Extension Dairy Specialist
While I was visiting a dairy farm this past month, the dairyman mentioned that the heifers he raises don�t milk as well as the springer heifers that he buys. My initial reaction was to place the blame on the fact that this producer has a long history of using herd bulls and not artificial insemination. Although this definitely was part of the problem, I soon discovered that after weaning the heifers were being fed rather high levels of grain mix without adequate protein and only limited amounts of forage. The heifers were gaining weight, but they were not growing in stature. I immediately thought of the work from Michigan State University that indicated that the rate of mammary growth was 3.5 times the rate of body growth. These workers found that excessive energy intake during the pre-pubertal period (3 to 10 months of age) had a negative effect on the mammary system and decreased subsequent milk production. I then remembered the work at Cornell University that demonstrated that it is the balance of protein and energy absorbed from the intestine which is important, rather than simply the amount of energy metabolized. They fed heifers diets balanced for carbohydrate and protein fractions to gain 1.6, 1.9, or 2.1 lbs/day during the pre-pubertal period with age at first calving of 24, 22, and 21 months, respectively. Mammary development as evidenced by first lactation milk yield was not compromised by the increased rates of growth during the pre-pubertal period as long as dietary protein was adequate and balanced with energy.
I was able to give the dairyman a mini workshop on protein nutrition for dairy calves and heifers which I will repeat here as a reminder to all of us:
1. The protein content of milk replacers for �enhanced early nutrition� should be 26 to 28% and the protein should come from milk solids. The customary 1 lb of a 20/20 calf starter will only produce gains of slightly more than � lb/day. Two lbs/day of a higher protein milk replacer are required for body weight gains of slightly less than 2 lbs/day. The fat content should be no higher than 15%, because higher levels reduce the consumption of calf starter. In fact, Illinois data suggest that a maximum of 12 to 15% fat in the milk replacer may be optimal for high rates of lean tissue growth.
2. The protein content of the calf starter should be at least 19 to 20% (dry matter basis), and for �enhanced early nutrition� the protein should be 22 to 24% and come from proteins with a good balance of essential amino acids.
3. Canadian workers found that 16.6% crude protein in the ration was optimal for Holstein heifers from 71 to 126 days of age. From 127 to 182 days, 14% crude protein in the dry matter was optimal. Ration crude protein of 12.7% seems to be optimal for Holstein heifers from 600 to 800 lbs. Once heifers are pregnant, the National Research Council recommends 14% crude protein for Holstein heifers from 990 to 1100 lbs and 13% crude protein from 1200 to 1400 lbs body weight.