Effects of Supplementation with Lasalocid and Synchronization with Melengesteral Acetate on Heifers to Improve Reproductive Efficiency

Robert A. Lane, William L. Nobles, F. Doug Blackard


Forty crossbred heifers were utilized in an experiment at the Sam Houston State University Country Campus Agricultural Complex to determine the effects of an ionophore (Iasalocid) and a synchronization feed additive (melengesteral acetate) on improving weight gains and reproductive efficiency in first estrus heifers. Ten heifers each were assigned to four equal size paddocks in a randomized block design for 136 days with feeding treatments consisting of; (1) oat/rye forage + 2lbs/head/day cot. tonseed meal(csm) + lasalocld, (2) oat/rye forage + csrn, (3) dormant pasture + bermudagrass hay + csm with lasalocid, and 4) dormant pasture + bermudagrass hay + csm.
The last nine days of the trial, each treatment group was randomly divided into two equal groups (20 animals each) with all beifers fed .5 mg/bd/d of melengesteral acetate (M GA) in the csm. One group was then injected with 25 mg each of prostaglandin to encourage heat sychronization. All animals were inseminated via artifical insemination techniques 80 hrs. later.
Analyses of variance indicate that the oat/rye forage was re-sponsible for greater weight gains and larger frame sizes regard-less of lasalocid supplementation. The synchronization treat-ment did not result in improved conception rates among the heifers via artifical insemination techniques, however 70% of the heifers were bred within 60 days following the treatment period.


Melengesteral acetate; Lasalocid; forage; estrus synchronization

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