|GUNN, P - Iowa State University|
|LUNDBERG, A - Iowa State University|
|Cushman, Robert - Bob|
|AMUNDSON, O - South Dakota State University|
|WALKER, J - South Dakota State University|
|PERRY, G - South Dakota State University|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/16/2015
Publication Date: 7/1/2015
Citation: Gunn, P.J., Lundberg, A.L., Cushman, R.A., Freetly, H.C., Amundson, O.L., Walker, J.A., Perry, G.A. 2015. Association between circulating blood or plasma urea nitrogen concentrations and reproductive efficiency in beef heifers and cows [abstract]. Journal of Animal Science. 93 (Supplement s3):88-89.
Technical Abstract: The objective was to examine the effect of circulating blood or plasma urea nitrogen concentrations (BPUNC) on reproductive efficiency in beef heifers and suckled beef cows. Data from nulliparous heifers (n = 284) as well as primiparous (n = 241) and multiparous (n = 806) beef cows were compiled across 15 experiments. A single blood sample collected from each female during estrous or ovulation synchronization was analyzed for BPUNC. Only females that were maintained on the same nutritional management scheme (pasture or coproduct-based drylot ration) for at least 1 wk prior to synchronization though the first 21 d of the breeding season were included in the analysis. To determine if BPUNC impacted first service pregnancy rate, cattle were categorized as having BPUNC above or below each integer from 10 to 25 mg/dL. The GLIMMIX procedure of SAS was used for data analysis. The model for each BPUNC classification analysis also included the fixed effects of age classification and nutritional management scheme. Interactions among fixed effects were not significant and removed (P = 0.10). Postpartum interval at synchronization was included in the model as a covariate when applicable and experiment was included as a random effect. Average first-service pregnancy rate across the dataset was 55.6%. Irrespective of age and nutritional management scheme, a BUNC that was associated with decreased pregnancy rates could not be established. In fact, there was a tendency for improved pregnancy rate as BPUNC increased (P = 0.08, r = 0.05) and cattle with BPUNC above 16 mg/dL tended to have greater pregnancy rates (57.0%) than those under 16 mg/dL (54.6%; P = 0.07). There were no differences (P = 0.16) in pregnancy rates between cattle that had BPUNC above or below any other integer from 10 to 25 mg/dL. Based on these data, when cattle are allowed to adapt to a nutritional management scheme prior to breeding and maintained on that diet through the first 21 d of the breeding season, BPUNC do not negatively affect first-service pregnancy rates.