Effects of Protein and Energy Supplementation of Cows Grazing Native Winter Range Forage on Intake and Digestibility

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Abstract
Trials were conducted in November and December of 1976 (trial 1) and in 1977 (trial 2). A daily equivalent of .75 kg of cottonseed meal (trial 1) or .70 kg of soybean meal (trial 2) was fed individually at 2- or 3-day intervals to dry, pregnant, mature cows grazing native fall-winter range (treatment P). Cracked barley (treatment G) was fed to a second group of cows at levels isocaloric with treatment P. A third group (treatment C) served as a control and received no supplement. Forage dry matter intake (DMI) and digestibility (DMD) were determined with chromic oxide and lignin used as indicators. In trial 1, with seven cows per treatment, forage DMI for treatments C, P and G were 8,639, 8,157 and 7,851 g/day, respectively. Respective values for forage DMD were: 54.9, 52.9 and 51.7%; for total DMI: 8,639, 8,898 and 8,537 g/day; and for total DMD: 54.9, 53.2 and 54.2%. All differences were nonsignificant. Average total weight gains for treatment groups ranged from 15.0 to 16.8 kg per animal. In trial 2, with 11 cows per treatment, daily forage DMI was higher for cows receiving treatment P (8,009g; P<.01) than for those receiving treatment C (6,813 g) or G (6,305 g). Forage DMD was lower for G (34.3%; P<.01) than for C (40.6%) or P (43.6%). Daily DMI was 6,813 g for cows receiving treatment C, 8,684 g for those receiving treatment P and 6,961 g for those receiving treatment G (P<.01 for P vs C and P vs G); DMD for respective treatments was 40.6, 46.4 and 38.8% (P<.01 for P vs C and P vs G). Treatment differences in weight change (−15.3 to −21.2 kg per animal) and changes in body condition score were not significant. Differences in forage DMI and DMD and response to supplementation between years were attributed to quantity and quality of forages available to the animals. Copyright © 1980. American Society of Animal Science . Copyright 1980 by American Society of Animal Science