Delaying Postpartum Supplementation in Cows Consuming Low-Quality Forage Does Not Alter Cow and Calf Productivity

Abstract

Reducing the amount of supplemental feed postpartum without affecting productivity may enhance profitability of cow-calf operations. Therefore, sixteen 2-yr-old fall calving cows were used to evaluate effects of delaying postpartum supplementation on milk production, serum metabolites, and cow and calf BW change. Cows were stratified by calving date and randomly assigned to one of two treatments: 908 g/d of a 46% CP supplement beginning 5 d postpartum (Supp5, n = 7); or 908 g/d of the same supplement beginning 30 d postpartum (Supp30, n = 9). Supplements were formulated to provide 425 g/d of CP with 225 g coming from ruminally undegradable protein (RUP), and were fed twice weekly. Cows were daily fed 8.2 kg chopped sudangrass hay (5.5% CP, 74% NDF, OM basis) during lactation. Cows and calves were weighed before feeding on two consecutive days on d 0, d 30, and d 80 postpartum. Milk production and constituents were evaluated on d 90. Cow BW was not different at d 0 (P = 0.21) and 80 (P = 0.12) between treatment groups. Cows receiving supplement starting on d 5 postpartum were heavier (P = 0.04) than Supp30 cows on d 30. However, no differences (P ≥ 0.17) were found in BW change or ADG during the duration of the study. Milk production was similar (P = 0.99) for postpartum supplementation treatments. No differences (P ≥ 0.27) were observed in milk fat, lactose, protein, or solids-non-fat. However, there was a tendency (P = 0.09) for milk urea nitrogen to be greater for cows receiving supplement on d 5 than d 30 of lactation. Serum urea nitrogen was greater (P = 0.02) in cows receiving Supp5 than cows receiving Supp30. Serum non-esterified fatty acid (NEFA) and glucose concentrations were not different (P ≥ 0.40) between treatment groups. Calf BW and average daily gain (ADG) was not influenced (P ≥ 0.81) by timing of initial postpartum supplementation. These results indicate that withholding supplementation during the first 30 d postpartum may change pattern of cow BW loss without affecting net BW loss, milk production, or calf growth. Therefore, timing of postpartum supplementation can be manipulated to reduce amount of feed provided without sacrificing cow or calf productivity.