Proceedings of the New Zealand Society of Animal Production.
1961, 21: 92-108
Proceedings of the New Zealand Society of Animal Production.
1961, 21: 92-108
Maintenance requirements of the grazing sheep were in all cases higher than those of pen-fed sheep of the same weight. The increase was only 10 to 30% for heavy sheep grazing in good pasture, but amounted to 50 to 100% for the medium and low weight sheep maintaining weight in progressively poorer pastures.
The maintenance requirement of medium and low weight grazing Merinos was considerably reduced when their weight was controlled, not by continuous access to poor pastures, but by restricted access (1% to 4 hours daily) to a good pasture.
The maintenance requirements of the pen-fed Romneys were similar to, and of the pen-fed Merinos were lower than, the amount specified by the usual ration scales and approximately equal to twice basal metabolism, while the requirements of the grazing sheep were generally a good deal higher, for both breeds.
The apparent increase in maintenance requirements, which was felt to be well outside possible experimental error or bias, roughly matched the increase in grazing time but seemed too great to be explained solely as energy spent in locomotion. Energy expenditure might be higher in hard grazing conditions because of extra work performance in grazing from a very short sward, or through the existence of an adrenal, or similar, "stress" mechanism, causing increased heat production of metabolic or endocrine origin. Further work is planned to test these suggestions.
Keywords: NZSAPAB;
