The Nebraska Ranch Practicum: An Insight into Cow and Calf Production from Varying Precipitation and Two Weaning Dates

Data from the Nebraska Ranch Practicum teaching herd (Red Angus × Simmental) were analyzed to determine if spring precipitation and weaning date affected cow-calf performance at the Gudmundsen Sandhills Laboratory, Whitman, NE. Recorded precipitation values from April, May, and June were used to calculate an average precipitation from 2000 to 2014. Precipitation levels were grouped based on one standard deviation above or below the 15-yr average, resulting in below-average (DRY, n = 79), average (AVG, n = 82), or above-average precipitation (WET, n = 80) categories. Crude protein and TDN were determined from diets of esophageally fistulated cows collected during the same 15 yr period. Although precipitation impacted forage quality, stocking rate was adjusted so forage quantity was not limited for grazing each yr. Calves were either weaned in September or November. Calves weaned in September grazed subirrigated meadow, whereas the unweaned calf and cow grazed native range. Calves weaned in November weighed more (P < 0.01; 222 vs 189 ± 3 kg, Nov. vs Sept.) than September-weaned calves at the November weaning date. However, the September weaning date resulted in greater (P ≤ 0.01) cow BW and BCS in November and January than November weaning. Calf BW was greater (P ≤ 0.01) in DRY yr compared with AVG and WET yr. Cow BW did not differ (P ≥ 0.20) in June, July, and November; however, cows in DRY yr tended to weigh more (P = 0.06) in September than AVG-yr cows. In addition, DRY-yr cows weighed more (P < 0.01) in January than cows managed in AVG or WET yr. Above-average precipitation in August and September during the DRY yr resulted in new plant growth and higher CP in fall diets, likely explaining increased cow BW. Cows classified in the WET yr had greater (P < 0.01) BCS in July and September than AVG or DRY cows. Body condition score, however, did not differ (P ≥ 0.17) among precipitation levels in November and January (5.3 ± 0.07). In September, DRY-yr cows had increased (P = 0.04; 5.5 vs 4.6 ± 0.28 kg, DRY vs WET) milk production compared with WET-yr cows. Precipitation did not affect (P = 0.95) pregnancy rates (94 ± 3%). In summary, cow production traits were not negatively impacted in a below-average precipitation yr, and calves weighed more in below-average than average or above-average precipitation yr.