Studies of compensatory growth in sheep

Abstract

A number of observations have been made on 5-to 6-month old wether Hampshire sheep undergoing uninterrupted growth (36-2% gain in shrunk wool -free live weight over 58 days), undernutrition (a 21-7 % fall in body weight over 27 days) and then followed by compensatory growth (a gain of 62-2 % in live weight over 52 days).Sheep being underfed had increased, and compensating sheep had decreased, apparent digestibility coefficients of feed dry matter compared to control sheep. Sheep undergoing compensatory growth drank more water, ingested more food per unit body weight, laid down less body fat, more protein and retained more water in their bodies than did control sheep. Tritiated water allowed estimation of total body water with an accuracy comparable to other reports in the literature.Changes in the weight and in RNA-P and DNA-P content of anterior pituitary, thyroid and adrenal glands were measured. Sheep thyroid glands were examined histologically to assess relative TSH outputs and no significant differences detected.R a t bio-assay of cavernous sinus plasma for somatotrophin and ACTH activity was made on these sheep. Somatotrophin was detected, but experimental groups did not statistically significantly differ in relative potency (TJ.S.P. units/ml fresh plasma). Compensating sheep had. significantly lower plasma somatotrophin potency per unit empty body-weight values than did the underfed sheep.No ACTH activity was detected in the sheep plasma of the several groups. During severe undernutrition the anterior pituitary gland decreased in size, but not in cell numbers, and still elaborated somatotrophin. Decrease in body size tends to increase the ratio of circulating somatotrophin per unit body size and thus may facilitate, in a permissive manner, the enhanced growth rate of animals undergoing compensatory growth.Restitution and gain of body size by compensatory growth is accompanied by hypertrophy of the anterior pituitary gland. This gland, after compensatory growth, showed evidence of enhanced synthesizing capacity.TNTT? ODTTO' TTO' Nr ^n a P r e v i°u s report on the body composition of 1191 animals (pigs, sheep, cattle;Reid et al. 1968) Compensatory growth occurs when previously some results were given of an experiment whose under-fed animals are given more food. I t expresses objective was to study the effect of submaintenance itself, for a variable period, as an enhanced rate of energy intake on the body composition of sheep but gain compared to that of similar, but continuously detailed body composition and endocrine gland fed, animals and is commonly experienced by the data were not given. grazing animal. The physiological basis of compenDetailed body composition data on 30 sheep are satory growth is obscure. Wilson & Osbourne (1960) given in the present paper because, of all the conhave reviewed this subject.siderable number of dietary treatments imposed on i A G s 79

Changes in body composition of sheep selected for high and low backfat thickness, during periods of ad libitum and maintenance feeding

“…The relative rate of fat deposition was greater during the premaintenance feeding period than during the postmaintenance feeding period. This was consistent with the results of Keenan et ah (1969), McManus et al (1972) and Little and Sandland (1975) who showed a decreased deposition of fat relative to the body after a period of interrupted growth. These studies have generally shown little effect of an interruption in growth pattern on the deposition of carcass lean or bone, which is consistent with our results.…”

Growth performance and metabolic changes in lambs and steers after mild nutritional restriction

“…In contrast to the steer trial no depression of digestibility was observed in the RR lambs offered a rapidly fermentable concentrate diet (Table 3). McManus, Reid & Donaldson (1972) and Drew & Reid (1975) also noted reduced digestibilities in compensating lambs but Asplund, Hedrick & Haugeback (1975) did not. The high digestibilities reported by Thornton et ah (1979) on the 1st day of realimentation appear to be due to applying the faecal output from the preceding period of near starvation feeding to the ad libitum intake on the 1st day of realimentation.…”

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

“…However, it is also necessary to bear in mind that other authors (Blaxter and Wood, 1951;Keenan, McManus, Scoggins, Myers and Freer, 1968;Morris, 1968;McManus, Reid and Donaldson, 1972) have found evidence that would indicate that restricted animals have a lower basal metabolism per unit of metabolic weight which still further reduces their maintenance requirements. This could be considered as a simple and acceptable explanation for the observed process of compensatory growth occurring after a period of restriction.…”