The feed intake of grazing sheep differing in age, breed, previous nutrition and live weight

Abstract

Two flocks of Merino wethers ranging in age from 3 to 87 months grazed a poor (L) or high (H) quality pasture for 3 months. The flocks were then combined, and intake was estimated while the sheep grazed four different pastures in succession. In a second experiment, flocks of Merino, Border Leicester, Southdown and Dorset Horn ewes of varying ages grazed in succession six pastures on which intakes were estimated and live weights recorded. The digestibility of the diet selected, as estimated from the faecal nitrogen concentration, declined with age by 0-053 units per month in Exp.(2) and curvilinearly in Exp. (1). In both experiments faecal output of sheep of similar breed receiving similar treatments increased with age to approximately 3 years and declined thereafter. In neither experiment was there a significant allometric relationship between intake and live weight.The intake of the L group was consistently greater than that of the H group when both groups grazed together. The differences were correlated with the quantity of green feed available. The faecal output of Dorset Horns, Merinos, Southdowns and Border Leicesters at 28-7 months of age was calculated to be 451, 402, 346 and 588 g per day respectively in Exp. (2). Mean digestibility of the diet selected estimated by the faecal nitrogen procedure was 65-1, 63-0, 64-7 and 64-5 units at 28-7 months for the Dorset Horns, Merinos, Southdowns and Border Leicesters respectively. Differences between breeds in faecal output and in the digestibility of the diet were significant.It is frequently assumed that intake of grazing lated exponents of 0-82 ±0-13 and 0'91±0-14 for animals varies with some function of live weight, the relationship between organic matter intake and and the allometric equation, Y = aW b where Y is live weight of penned and grazing Blackface, intake and W is live weight has been used to de-Border Leicester x Blackface, Shetland and Cheviot scribe such a relationship (e.g. Holmes, Jones & sheep varying in age from 1 to 2 years. A negative Drake-Brockman, 1961). It seems unlikely that relationship between intake and live weight for any single relationship will be generally applicable sheep varying in condition was reported by Allden since differences in live weight may result from & Scott Young (1964) who observed that grazing differences in age, in breed and in the previous level sheep which had been subjected to a low plane of of nutrition. In addition differences in pasture nutrition consumed up to 20% more feed than a availability may limit the degree to which sheep control group. can express potential differences in voluntary Two experiments are reported here which were intake.undertaken to examine further the intake of grazHadjipieris, Jones & Holmes (1965) and Arnold ing sheep varying in live weight, age, breed and pre-(1966) observed higher intakes per unit live weight vious nutritional history. In Exp. (1), two flocks of by young than by adult sheep, although Arnold Merino wethers ranging in age from 7 to 91 months (1966) found that the...

Relationship between live weight, age and dry-matter intake for beef cattle after different levels of food restriction

“…Langlands (1968) reached a similar conclusion for sheep of four different breeds and different nutritional levels. Langlands (1968) reached a similar conclusion for sheep of four different breeds and different nutritional levels.…”

Comparative studies of the influence of sward conditions on the ingestive behaviour of cows and sheep

“…The estimates of mean daily herbage intake derived from ingestive behaviour variables (Table 6) were substantially higher than other published values for similar classes of stock (Langlands, 1968;Hodgson and Milne, 1978;Hodgson and Jamieson, 1981) and it is logical to assume that one or more of the three variables shown in Table 3 must have been overestimated. Overestimation of intake per bite may result from positive bias in estimates of the weight of extrusa collected or negative bias in measuring the number of bites taken during a collection.…”

The Consumption of Perennial Ryegrass and Red Clover by Grazing Lambs

“…The assumption was made that there were no real differences in the digestibility of the diet selected, and the differences between the estimates of herbage intake for experienced and inexperienced lambs are due entirely to differences in faecal output (Table 3). This is not necessarily a valid assumption, but the available evidence (10,12,13) indicates that any differences in selection which may have occurred would be much too small to explain the differences in the estimates of herbage intake. Also, the fact that there were no significant differences in the botanical composition of the herbage remaining after grazing by experienced and inexperienced animals ( Table 2) suggests that the assumption is reasonable.…”