Effects of the plane of nutrition on growth and the development of carcass quality in lambs Part I. The effects of High and Low planes of nutrition at different ages

• Published in: The Journal of agricultural science 1952-01, Vol.42 (1-2), p.1-92
• Main Authors: Pálsson, H., Vergés, Juan B.
• Format: Article
• Language: English
• ISSN: 0021-8596; 1469-5146
• DOI: 10.1017/S0021859600058718

1. Two series of half-brother-sister lambs of balanced sexes have been reared on widely different (High and Low) planes of nutrition from the end of the third month of foetal life to 41 weeks of age. The effect of this on the growth in live weight and relative development of the body proportions has been studied. 2. The feeding of the mothers of the experimental lambs during the last 2 months of pregnancy was such that the High-Plane mothers gained 39·5 lb. live weight during pregnancy as compared with a gain of 1 lb. only in the Low-Plane group. The single lambs from both groups were of equal weight at birth, while on the average each individual twin was 47% heavier in the High-Plane than in the Low-Plane group. 3. In post-natal life the High-Plane lambs were fed so as to allow them to grow at their maximum rate and the feeding of the Low-Plane ones was controlled so as to allow them to grow at a slow but uniform rate. Lambs from both groups were killed at birth, at 9 weeks old and at 41 weeks old. At 9 weeks old the Low-Plane lambs killed had an average live weight of 14·3 lb. and the High-Plane ones 61·5 lb.; at 41 weeks old the respective weights were 69·5 and 180 lb. 4. The study of the age changes in the High-Plane lambs further proved the theory put forward by Hammond (1932) that in the sheep in post-natal life the different anatomical regions and tissues of the body grow differentially and in a definite order of development. The dressed carcass is later maturing than the organs and offal parts as a whole. 5. Of all the organs in the body the brain is the earliest developing, followed closely by the eyes. The thoracic organs as a whole are earlier maturing than the abdominal organs. Of the former, the thyroids, lungs and trachea and the heart are the earliest maturing in that order, while the thymus glands are later maturing. Of the alimentary tract, the oesophagus and the abomasum are the earliest developing parts, while the rumen and reticulum are much later maturing, growing at nearly twice the rate of muscle in the carcass from birth to 41 weeks. Of the other abdominal organs, the kidneys are earliest maturing, growing at approximately similar rate as the lungs and trachea, and slower than the heart in post-natal life. The abdominal fats are the latest maturing of all the organs, and of these kidney fat is the earliest maturing and the caul fat the latest. 6. The marked heterogonic growth of the organs appears to be related to their function. Th