Meadow Forage Quality, Intake, and Milk Production of Cows

Abstract

A native mountain meadow was grazed by cows through the summer and fall of 1970 near Gunnison, Colorado. Nutrient concentration and in vitro digestibility were measured from forage samples collected from esophageally-fistulated cows. Total fecal excretion was estimated by the Cr2O3 dilution technique. Forage consumption was calculated from digestibility and fecal-excretion data. Milk production of cows was determined at biweekly intervals by measuring calf weights before and after nursing, followed by machine milking. The cell-wall constituent (CWC) content of the diet increased from 47.2 to 62.1% from mid-June to mid-October. CWC digestibility decreased from 72.8 to 52.3% during the same period. The nitrogen concentration of the diet decreased from 3.1 to 1.2%; whereas the nitrogen concentration in standing forage decreased from 3.8 to 1.4%. Dry-matter consumption averaged 14.7, 12.0, 10.5, and 10.3 kg per day, and mean milk production was 6.0, 4.4, 4.0, and 3.0 kg in 14 hours for Brown Swiss, Charolais x Angus, and San Juan Basin and Commercial Hereford cows, respectively. Daily dry-matter consumption did not change significantly as the season advanced. Daily milk production declined from 5.7 in April to 2.0 kg in November. Animals selectively grazed bluegrass regrowth on drier sites, leaving abundant sedge growth on lightly-grazed wet sites. This grazing pattern resulted in high dietary nutrient levels throughout most of the season.