Abstract
A study was made of grazing intensity effects by imposing on irrigated pasture stocking rates of 1.35, 2.25, 3.06, 3.93 and 4.68 steers per acre. A group of steers fed soilage from the same pastures served as a positive control similar to what might be expected from pasturing forage without the superimposed animal influence. To increase the precision of the comparisons, body composition, intake and digestibility of the forage were added to the usual measurements of weight gains, clipping yields and chemical composition of the forage. Increased stocking rate decreased yield of the forage as the season progressed. No carry-over influence, however, was found the following season. Yield of forage from the soilage treatment was greater during the latter part of the season than from pasture treatments. The digestible energy content of the forage consumed by the soilage steers was 126 meal, per 100 lb. For pasturing, a light stocking rate allowed the steers freedom to select a more nutritious forage, 130 to 132 meal., whereas heavy stocking forced the steers to consume a less nutritious forage, 122 meal, per 100 lb. As grazing intensity increased from 1.35 to 4.68 steers per acre, feed and energy intake decreased, weight gain decreased and the energy content of the carcass decreased. In this pasture experiment maximum production per animal was not the proper measure. Production per acre was more realistic. As stocking rate increased the animals harvested and consumed more of the forage and digestible energy per acre even though consumption decreased per animal. A most important animal-plant interaction was present because liveweight gain and corrected carcass production per acre increased to a point, about four animals per acre, and then rapidly decreased. Increasing the stocking rate increased consumption of forage per acre, but here also consumption per animal was low enough so that too much forage was used for maintenance rather than gain and per-acre production decreased as a consequence. A wide range in grazing intensity, 2.25 to 4 steers per acre, allowed close to maximum corrected carcass production per acre. This seems to indicate that a pasture operator has a wide latitude in stocking rate. A highly significant correlation (0.85) was found between digestible energy intake and forage available per animal as determined by pregrazing clipping. Soilage compared to pasturing at the same stocking rate resulted in greater per-acre consumption of digestible energy and a 32% increase in corrected carcass production. Copyright © . .