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Comparison of winter feeding systems for the evaluation of beef cow performance, reproductive efficiency and system costs
Extensive winter grazing has been proven as a successful strategy to reduce production and labor costs in a cow-calf operation without much adverse effects on animal health and performance. Two experiments were conducted during the winter of 2012-2013, to evaluate 3 winter feeding systems: (i) field grazing standing whole plant corn (SC; TDN=59.5%, CP=7.8%), (ii) field grazing swathed barley hay (SB; TDN=66.2%, CP=8.5%) and, (iii) barley hay bales fed in drylot pens (DL; TDN=60.1%, CP=12.7%). The specific objectives were to compare beef cow performance, reproductive efficiency and system costs in experiment 1 (EXP 1), and ruminal pH parameters in experiment 2 (EXP 2). In EXP 1, dry pregnant Angus cows (n = 60, body weight (BW) = 651.2 ± 7 kg), stratified by body weight and days pregnant were randomly allocated to 1 of 3 replicated (n = 2) winter grazing treatments for 77 d. Cow BW, body condition score (BCS), and rib and rump fats were measured at the start and end of the trial. Increases in rump fat were greater (P = 0.002) for SC cows compared to DL cows (1.90 mm vs 0.55 mm, respectively). Calves born to cows on SC were heavier (P ˂ 0.001) at birth compared to calves from SB cows (42 vs 40 kg respectively). In EXP 2, 9 cannulated beef heifers were cycled through the 3 winter systems concurrently within EXP 1, in a replicated 3 × 3 Latin square design, for 63d to evaluate effect of forage type on rumen pH. Results from EXP 2 indicated that SB heifers had the lowest (P < 0.003) mean, minimum and maximum rumen pH and greatest duration and area under pH < 5.8 (P< 0.001) compared to heifers on SC and DL winter systems. Economic analysis revealed that total costs were greatest for the DL ($2.29/head/d) compared to SC ($1.78/head/d) and SB ($1.65/head/d) systems. Results suggest that both SC and SB systems are cost effective alternatives to DL system, and do not negatively affect cow body weight or reproductive performance in winter.
Keywords: winter grazing, corn grazing, swath grazing, reproductive performance