|Hall, J - VIRGINIA TECH|
|Staigmiller, Robert - RETIRED USDA-ARS|
Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Other
Publication Acceptance Date: September 1, 1997
Publication Date: N/A
Technical Abstract: A study was conducted to evaluate the influences of nutritional management, trace mineral supplementation, and exogenous progesterone on attainment of puberty in beef heifers. One hundred eighty heifers were assigned at weaning to blocks and treatments. Treatments included two dietary regimens (corn silage vs pasture + oatlage), trace mineral supplementation, and puberty induction strategy (with or without progestin implant). Heifers receiving pasture + oatlage were managed on grass-legume pastures from October 14 until December 14, and then placed in pens and fed an oatlage-based diet through May 1994. Heifers on the corn-silage based diet were housed in pens throughout the study. Norgestomet was implanted in half of the heifers on April 11 for 10 d. Progestin implant increased (P < .05) the number of heifers puberal by the end of the study compared to nonimplanted heifers (88% vs 70%). Fewer implanted heifers tended (P < .10) to be pregnant at fall palpation than nonimplanted heifers (83.5 vs 92.1%). Trace mineral supplementation decreased (P < .05) first service conception rates but did not affect total AI pregnancy rates. Plasma copper levels were below recommended levels in heifers fed oatlage-based diets without trace minerals. We conclude that heifers can be placed on regrowth in irrigated pastures during the fall and still make acceptable gains for attainment of puberty the following spring and that progesterone treatment can aid in inducing heifers to reach puberty.