PSXI-16 - Evaluation of supplementation strategies for beef cattle bale-grazing grass hay in Winter

Methods of supplementing beef cows while bale grazing grass hay were investigated in a study conducted for four winters, from 2016 to 2019, at the Central Grasslands Research Extension Center near Streeter, ND. Starting in the fall of each year, cows were assigned to eight groups of similar total body weight (BW) and allowed to bale graze one of four bale grazing treatments as follows: a) grass hay, b) grass hay supplemented with alfalfa hay, c) grass hay supplemented with corn DDGS, and d) grass hay treated with a liquid supplement. Two-day body weights and body condition scores (BCS) were taken at the start and end of the study. Final BW were greater (P ≤ 0.05) when cows were supplemented with DDGS and least when cows were not supplemented. Average daily gains were influenced by method of supplementation and year (P ≤ 0.025). When winters were cold, supplementation with alfalfa hay or a liquid supplement were not adequate to maintain cows resulting with weight loss. Final BCS were greatest (P ≤ 0.05) when cows were supplemented with DDGS and lowest on grass hay. Similarly, change in BCS was greatest in DDGS-supplemented cows and lowest on grass hay only. Calf birth weights, weaning weights and daily gains were not influenced (P > 0.05) by method of supplementation. Results suggest that method of supplementation during bale grazing should be based on prevailing environmental conditions during winter. In severely cold winters, good-quality alfalfa hay or a liquid supplement are not adequate to meet requirements of pregnant beef cows in mid-gestation. Under such conditions, supplements such as corn DDGS will be needed to meet animal requirements. Supplementation with good-quality alfalfa hay or grass hay treated with a liquid supplement may be an option during mild winters.