Considerable attention has been placed in recent years on delivering more nutrients to calves and heifers, and thus achieving faster growth rates and more efficient readiness for breeding.
But hitting aggressive growth targets – more than 2.2 pounds per day – poses a downside risk for developing dairy heifers, according to Dr. Jim Quigley, Technical and Research Manager with Provimi North America.
“Feeding excess energy prior to puberty creates the risk of fat deposition in mammary tissue,” advises Quigley. “We call the growth stage during which mammary tissue is most quickly developing its ‘allometric’ growth phase.
“Allometric growth refers to the concept that the mammary system grows faster than the animal as a whole,” Quigley continues. “Typically, allometric growth occurs through puberty, which will occur at about 9 to 13 months of age. Increasing rate of gain will cause heifers to reach puberty at an earlier age. Until puberty, we should be especially careful about delivering excess energy in the diet, particularly if the protein-to-energy ratio is out of balance.”
Quigley offers two key pieces of advice in this regard:
(1) Make sure the protein-to-energy ratio in the heifer’s diet is correct. Feeding excessive energy without protein will cause the energy to be deposited as fat.
(2) Strive to achieve pre-pubescent weight gains of about 1.75 to 2.00 pounds (800 to 900 grams) per day.
“Gains higher than this may be possible, but that doesn’t mean they’re advisable,” cautions Quigley. “Highly aggressive heifer-feeding programs become more risky in terms of mammary fat deposition.”
For guidelines on appropriate protein-to-energy ratios and other nutritional advice for growing heifers, Quigley recommends this resource from the University of Wisconsin.