The expected and observed changes in the intake of three hays by sheep after shearing

Abstract

I . The effect of shearing Merino wethers on their voluntary intake of three hays of different digestibilities was studied in two experiments.2. In Expt I , six groups of ten wethers in metabolism crates were given lucerne (a goodquality) hay, setaria (a medium-quality) hay and pangola (a poor-quality) hay ad Zib., at an average room temperature of 25'. The sheep of one of the two groups given each hay were shorn at the beginning of the experimental period. For 4 weeks after shearing, the shorn sheep given lucerne hay had significantly lower intakes than the unshorn sheep. The intake of setaria was similar for the shorn and unshorn sheep, and the shorn sheep had significantly higher intakes of pangola than the unshorn sheep in the period 3-5 weeks after shearing. 3. Expt 2 was conducted similarly to Expt I , but using fifty-two wethers at an average room temperature of 13' and using a different lucerne hay. The shorn sheep ate less lucerne than the unshorn sheep only in the 1st week after shearing. The shorn sheep had higher intakes of setaria and pangola hay than the unshorn sheep during the 3rd-5th weeks after shearing. At the lower ambient temperature of Expt 2, the increases in hay intake of the shorn sheep were greater, compared with those of the unshorn sheep, than they were in Expt I.4. Shearing was not followed by any consistent changes in the digestibilities of the hays.The differences in the amounts of dry matter digested by the shorn and unshorn sheep were closely related to their dry-matter intakes.5. It was concluded that the intake of poor-quality hay by sheep could increase in response to an increase in energy expenditure produced by shearing, although this response often occurred 2-3 weeks after shearing. Thus ruminal fill and rate of passage, which are generally considered to control the intake of roughages of low digestibility, may be responsible only for the shortterm control of food intake. .The lucerne-fed sheep in both experiments increased their weights and had digestible dry-matter intakes nearly twice as high as the setaria-fed and pangola-fed sheep. The decreased intakes of lucerne hay of the shorn sheep suggested that some mechanism, other than one regulating energy balance, was controlling intake in these experiments.The long-term control of food intake in the adult monogastric animal is believed to be maintained by mechanisms which balance energy intake against energy expenditure so that the reserve of energy (as fat) is maintained (Kennedy, 1961). Numerous experiments have been conducted on the factors controlling food intake in the ruminant, and in these experiments, variation in energy expenditure has necessarily been minimized. For instance, in a study of the hay intake of sheep in metabolism crates Blaxter, Wainman & Wilson (1961) found that the intake of food was closely related to its apparent digestibility. This general effect was also observed when sixty-R G z 9AT.

The effect of increased energy demand through walking exercise on intake and ruminal characteristics of sheep fed a roughage diet

“…Although empty-body weight tended to decrease with exercise in the present study (Table 2) this decrease was not statistically significant. However, the duration of increased energy demand was much shorter in this case than in the experiment of Minson & Ternouth (1971).…”

“…The work of Graham, Nicol & Christopherson (1982) suggests that these increases are also obtained through increased rumen tissue weight and a concomitant increase in rumen fill. Body weight losses in the study by Minson & Ternouth (1971) indicated a negative balance between energy demand and energy supply. Although empty-body weight tended to decrease with exercise in the present study (Table 2) this decrease was not statistically significant.…”

“…(1980) ascribed these increased intakes to an increase in energy output through milk production. The study by Minson & Ternouth (1971) with sheared sheep also showed an increase of up to 20% in consumption of low quality roughages during cold stress. The work of Graham, Nicol & Christopherson (1982) suggests that these increases are also obtained through increased rumen tissue weight and a concomitant increase in rumen fill.…”

“…The increases in be overcome in order to increase voluntary roughage roughage consumption observed during cold exconsumption and hence animal production. Com-posure (Minson & Ternouth, 1971) and lactation parisons of voluntary roughage intake of lactating (Marsh, Curran & Campling, 1971) coincide with and non-pregnant non-lactating ruminants suggests significant increases in energy demand. This suggests that it is possible.…”

Climatic adaptation in recently shorn merino sheep

“…The depression persisted for at least three weeks in the WL group, while the WG group increased their intake. The data of both Weston (1970) and Minson and Ternouth (1971) also indicate a post-shearing depression of intake in conditions which were cooler than the tilermoneutral conditions specified by Graham et al (1959) for newly shorn sheep with similar food intakes. This depression is increased and extended for a longer time under ambient temperatures between -3 and 8oc (Lynch unpublished).…”