Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2006
Publication Date: 3/19/2007
Citation: Kreider, D.L., Coffey, K.P., Caldwell, J.D., Coblentz, W.K., Montgomery, T.G., Whitworth, W., Mcnew, R., Ogden, R.K. 2007. Reproductive performance, blood urea nitrogen, and blood glucose concentration in beef heifers grazing annual ryegrass in the spring and supplemented at different intervals prior to timed AI [abstract]. Journal of Animal Science. 85(supplement 2):119.
Technical Abstract: In successive years (n=36 and n=40), 76 Gelbvieh x Angus heifers at 12 to 14 months of age were sorted by weight and randomly allocated to one of eight bermudagrass pastures overseeded with annual ryegrass in order to determine the impact of supplemented rumen degradable carbohydrates at different intervals prior to breeding on conception rate (CR) to artificial insemination (AI), overall pregnancy rate (PR), serum urea nitrogen (SUN) and serum glucose (GLU) concentrations. Heifers grazed pastures during March, April, and May. Two replicates were provided no supplement (C); three replicates each were provided 1.4 kg/hd of supplement (32.5% ground corn, 32.5% cracked corn, 30% wheat middlings, and 5% liquid molasses) at approximately 0930 h daily, beginning either 60 (60S) or 30 (30S) d before timed AI. Heifers in each of the two treatment groups received supplement for 30 days, regardless of treatment. Supplement for 60S was discontinued at the time 30S was initiated. Heifers were weighed without prior removal from pasture and water at the initiation of the study and at approximately 28-d intervals. Serum samples were gathered at 1230 h and 1530 h on d 7 following the start of supplement and on the d before timed AI. CR to timed AI was 42, 62, and 48% for C, 30S, and 60S, respectively, but did not differ between treatments (P=0.31). PR was 92, 86, and 78% for C, 30S, and 60S and did not differ between treatments (P=0.42). SUN was not altered by treatment (P=0.95), or time of day (P=0.68), but was affected by month (P<0.001). SUN decreased, averaging 24.1±2.5, 15.5±2.4, and 10.5±2.4 mg/dl (mean±SE) for March, April, and May respectively. GLU differed between months, averaging 90.8±3.8, 90.5±3.2 and 101.6±3.3 mg/dl (mean±SE) for March, April, and May respectively. There was also a time of day by month interaction (P<0.001) for GLU. Timing of supplementation in this study did not affect conception to AI or overall pregnancy rates.