School of Agriculture, Food and Ecosystem Sciences - Theses
Permanent URI for this collection
Search Results
1 - 1 of 1
-
ItemThe physical and functional development of the forestomachs of the lamb( 1960)In this thesis a study of the physical and functional development of the forestomachs of the lamb is presented. The experimental work can be divided into three main fields as follows:- a) Studies on the physical development of the fore- stomachs. b) Studies on the functional development of the reticule-rumen. a) Field work in which the above studies have some direct bearing. The main findings of these studies have a) PhysicaI development of the forestomachs: In grazing lefts the four stomachs have reached their adult proportions by approximately 8 weeks of age. The type of diet can markedly influence the rate of growth of the forestomachs, and in general, it would appear that plant food is needed for the normal development of the forestomachs, and It plant food is excluded from the diet the development of the forestomachs is retarded at about the level found in the 3 week old grazing lamb. The main changes in the histology of the forestomach walls takes place during the last third of foetal life, and the adult his histological features are all present at birth. The major post-natal histological changes are complete by 56 days of age. It would appear that age is the main factor controlling the histological development of the forestomachs, and that plant material is necessary for the full development It of these organs. It was also shown that different diets can cause differences in the appearance of the rumen mucosal surface, stratum granulosum and stratum corneum. b) Funcational development of the reticulo-rumen: It was postulated that the functional development of the reticulo-rumen of the grazing iamb could be divided into three phases - a non ruminant phase (0 - 3 weeks of age), a transition phase (3 - 8 weeks of age) and an adult ruminant phase (8 weeks of age onwards). If plant food was excluded from the diet, the lamb remained in the non- ruminant phase, however, once plant food was fed to these lambs the reticule-rumen function reached the adult levels within one week. c) Field studies: As the forestomachs of the grazing are qualitatively and quantitatively fully developed by approximately 8 weeks of age, it is possible to ween lambs of this age with no check to their growth rate, provided the pastures are relatively high in protein and are not at the late flowering or seeding stages. The milk yield of the grazing ewe measured by the oxytocin technique gave consistently higher recordings throughout Iactation than the conventional lamb suckling technique. By the tenth week of the lactation the milk yield, as measured by both techniques, had fallen by half. There was a high correlation between the milk yield of the ewe and the lamb live weight growth up to seven weeks of age.