The SJBRC cow herd was has generally been managed under commercial conditions similar to those of other ranches in the Four Corners area. The cow herd grazed native range typified by native grasses, sagebrush, scrub oak brush and Ponderosa pine. The grazing season lasted from mid-May to mid-December. Typical stocking rates were 40 acres per cow-calf unit. Some irrigated pastures were utilized as available. Winter conditions necessitated the feeding of harvested forages and, beginning in 1988, the grazing of cornstalks in northern New Mexico.
Calves, born primarily in March and April, were maintained with the cows in pastures of native grasses until weaning at approximately 205 days of age. The 60 day calving season was established in 1967. Prior to that time, the season extended for 90 days. At weaning, adjusted weaning weight ratios were used to determine which bull calves were to be castrated. A post-weaning-gain bull test was established in 1948 for station bulls as well as interested cooperators. The test became known as the Four Corners Bull Test
. Over the years, the test has varied in length. In 1949 it was 84 days and from 1950-1956 it was 112 days. From 1957 to 1987, it was 140 days, from 1988-1995, it was a 120 day test, and from 1995 to present it is once again a 112 day test. After weaning, bulls were placed on a three week warm up ration prior to beginning the gain test.
Sire selection from 1956-1966 was based on an index of I = weaning weight plus 50 times postweaning average daily gain. Since 1966, selection of sires has primarily focused on preweaning and postweaning average daily gain but without an index. Generally, inbred sires were retained as herd sires and outside sire use was minimized.
After weaning, replacement females were managed in a drylot on a high roughage diet designed to produced average gains of 1.0 to 1.25 pounds per day until breeding at 13-15 months of age. Selection of replacement heifers was dependent upon age, weight and the need for females within line or linecross groups. Brood cows were culled on health, structural soundness and fall pregnancy test results. Open females rarely remained in the herd. Approximately 40 percent of the heifers were retained at weaning for consideration as replacements. Herd replacement rate was maintained at an annual rate of 25 percent.