Effects of frequency of supplementation of low-quality gestation diets on beef cow performance from mid-gestation through lactation and preweaning calf performance

Objective: This study's objective was to determine whether supplementation and frequency of supplementation for low-quality roughage diets were sufficient for cows to maintain condition during gestation, wean a healthy calf, and become pregnant for bearing a calf on a yearly basis. Materials and Methods: Pregnant crossbred beef cows (2016; n = 102, BW = 661 +/- 89; 2017, n = 76, BW = 727 +/- 100 kg) were allocated in mid-gestation to 1 of 5 nutritional regimens in a completely randomized design. Nutritional regimens (DM basis) included (1) 70% haylage, 30% millet straw fed ad libitum (HAYL); (2) haylage fed at 1.0% DM basis of cow BW with ad libitum millet straw (MSHAYL); and (3) MSHAYL fed an energy-protein supplement (0.22% of BW) at 1 d/wk, (4) 2 d/wk, or (5) 3 d/wk. Growth performance and body condition were evaluated from the second trimester until weaning. Results and Discussion: The HAYL cows had greater (P < 0.001) DMI, ADG, and fat deposition versus MSHAYL cows. Gestation length was shorter (P = 0.06) in cows fed HAYL versus MSHAYL, with no differences in pregnancy rates or calf preweaning ADG and weaning weights (P > 0.05). Most cow growth performance traits were not affected (P > 0.05) by supplementation or supplementation frequency. Implications and Applications: Supplement use at this rate cannot be recommended because there were no improvements in cow performance that would justify its purchase. Although feeding the MSHAYL ration alone could be viable, there are concerns for fetal programming effects that would affect progeny performance.