Published online by Cambridge University Press: 27 March 2009
The growth and feed intakes of Corriedale wether sheep when grown from 30 to 50 kg body weight by five different growth paths are described.
Group A (control) grew continuously (fed ad libitum). After reaching ca; 40 kg body weight, group B and C animals lost 21% of their initial body weight over 9 and 18 weeks and at 122 and 63 g/day, respectively, and began realimentation at 30 kg body weight. Group D and E animals were ca. 50 kg body weight when weight loss was imposed and they lost body weight at similar rates (125 and 157 g/day) respectively. Animals in group D lost 34% of their initial body weight over 18 weeks and began realimentation at 30 kg body weight (the same as groups B and C). Group E animals lost 23% of their initial body weight over 9 weeks to begin realimentation at 35 kg body weight. Except during periods of weight loss, animals were fed ad libitum. Compensatory growth was observed in all groups which had lost weight, with early recovery growth rates 1·6–1·8 times higher than control sheep of the same weight.
Rate of body-weight loss did not induce any significant differences in response to realimentation but results (groups B and C) suggest that the more rapid the loss, the more rapid will recovery be during realimentation. When sheep at different body weights lost the same proportion of their initial body weights, the heavier sheep (group E) attained final slaughter weight quicker than the lighter sheep (group B). When the proportion of body weight lost to reach a particular lower body weight was varied (groups B and D), the greater weight loss was associated with higher and more persistent growth rates during realimentation.
After weight loss, ad libitum dry-matter intake was significantly lower during the first 10 kg of gain during realimentation in all treatment groups (B, C, D, E) than in control group A. There were no differences between treatment groups in recovery of dry-matter intake.
Gross efficiency in all treatment groups was higher than in the control group A during the first 10 kg of recovery of body weight, but it then declined rapidly. This increase in gross efficiency was considered to be due to a combination of increased growth rates, reduced feed intakes and lower maintenance requirements. When the complete growth paths from 30 to 50 kg were considered, there were no significant differences in total feed consumed by the sheep following the five different growth paths.