J. Anim Sci.
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J. Anim Sci. 1965. 24:697-704.
© 1965 American Society of Animal Science
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Further Studies on the Influence of Stocking Rate on Animal and Forage Production from Irrigated Pasture

J. L. Hull, J. H. Meyer1, Sergio E. Bonilla2 and W. Weitkamp3

University of California, Davis

Abstract

A 3-year study was made of the effects of different grazing intensities (4.5, 9.0, and 13.5 steers per hectare) on beef production from an irrigated orchardgrass-Ladino clover pasture. Animals previously had been fed a low or medium energy intake for 172 days. Forage intake as determined by the chromogen-chromium oxide technique, body composition estimated from carcass specific gravity and energy gain on the different treatments were added to the conventional measurements of weight gain, clipping yield and chemical composition of the forage.

Increased stocking rate decreased total forage production within the season, but no carry-over effect was observed the following year, suggesting that the 35-day recovery period for the pasture was adequate to maintain plant vigor.

As stocking rate increased lignin decreased and protein increased in the available forage, but this was not representative of the forage consumed by the animals because digestibility decreased with increased grazing pressure. Increased stocking rate reduced forage intake, live weight gain, fat corrected carcass and energy gain per animal. Production per hectare was a more appropriate measure. Forage consumption per hectare increased with stocking rate, but consumption per animal can be lowered sufficiently to result in utilization of an increased proportion of the forage for maintenance of the animal rather than for gain. A low energy intake previous to grazing allowed more latitude in stocking rates, from 6.25 to 11.0 steers per hectare, while a previous medium energy intake did not allow a latitude in stocking rates. The data suggest that optimum utilization of irrigated pasture by growing beef steers results from animals previously fed a low plane rather than a higher plane of nutrition.

Compensatory growth of 0.2 kg. increase in daily gain resulted from animals previously fed a low energy ration. The effects of the compensatory growth during grazing were noted in the carcass traits.

The data show that any conclusions from grazing management studies on plant-animal interactions must be based upon considerations of previous treatment of the animals. It was emphasized, moreover, that live weight gain of grazing animals will not lead to valid conclusions, if differences in carcass composition are not considered.

Footnotes

1 Department of Animal Husbandry.

2 Present address: Instituto de Investigaciones Agropecuarias, Castilla 5427, Santiago, Chile.

3 Present address: Agricultural Extension Service, San Mateo, California.






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Copyright © 1965 by the American Society of Animal Science.