EFFECT OF NUTRITIONAL MANAGEMENT, TRACE MINERAL SUPPLEMENTATION, AND NORGESTOMET IMPLANT ON ATTAINMENT OF PUBERTY IN BEEF HEIFERS

We conducted a study to evaluate the influences of nutritional managem ent, trace mineral supplementation, and exogenous progesterone on atta inment of puberty in beef heifers. Heifers (n = 180) were assigned at weaning to blocks and treatments. Treatments included two dietary regi mens (corn silage vs pasture + oatlage), trace mineral supplementation , and puberty induction strategy (with or without progestin implant). Heifers that received pasture + oatlage were managed on grass-legume p astures from October 14 until December 14 and were then placed in pens and fed an oatlage-based diet through May 1994. Heifers fed the corn silage-based diet were housed in pens throughout the study. Norgestome t was implanted in half of the heifers on April 11 for 10 d. Progestin implant increased (P < .05) the number of heifers that had attained p uberty by the end of the study, compared with nonimplanted heifers (89 % vs 71%). Trace mineral supplementation did not affect percentage of heifers that reached puberty before the implant period. Plasma copper levels were below recommended levels in heifers fed oatlage-based diet s without trace minerals. We conclude that heifers can be placed on re growth in irrigated pastures during the fall and still make acceptable gains for attainment of puberty the following spring and that progest in treatment can aid in inducing heifers to reach puberty.