No description available.

Crossbred lambs were injected with L-arginine hydrochloride (arg) to determine the effects of single of multiple arg challenges on growth hormone (GH) secretion. Indwelling jugular catheters were inserted. At the beginning of each of 3 trials, lambs were injected with saline and blood samples were collected for 90 min to establish baseline GH. Blood sampling continued at 5-min intervals until 1 h after the final injection, then at 10-min intervals for one additional hour. In trial 1 arg (.5g/kg) was injected into 6 lambs while the other 6 received a second saline injection. Trial 2 consisted of 3 arg injections given at 1-h intervals. Trial 3 utilized 4 arg injections given at 15-min intervals. Trials 2 and 3 were replicated using a switchback design. Serum GH and insulin were measured by double antibody RIA. Mean GH for treated lambs in trial 1 was 3.89 ng/ml versus 1.74 ng/ml in controls (P<.01). GH peaked 30 min after injection (9.47 ng/ml), declined to 5-times baseline and remained near that level throughout the sampling period. Serum insulin was not different between treatments. In trial 2 arg treated lambs had higher mean GH (2.57 ng/ml) than controls (.86 ng/ml; P<.01). Peaks of GH were observed 20 min after the first injection (7.59 ng/ml) and 1 h after the second injection (5.6 ng/ml). No increase in GH was observed after the third injection. Insulin tended to follow the same pattern, but was not significantly elevated in treated lambs. Differences in trial 3 mean GH between arg-treated lambs (5.25 ng/ml) and controls (1.16 ng/ml) were significant (P<.01). GH peaked (13.8 ng/ml) at 25 min after the first injection, surged again 100 min later (7.4 ng/ml), declined to levels 3-times baseline and remained elevated. Trial 3 insulin levels were significantly higher in treated lambs (.64 ng/ml) compared to control lambs (.15 ng/ml; P<.01). Control lambs showed no significant GH or insulin increases at any time. GH secretion patterns were significantly altered in lambs injected with arg. One arg injection caused GH to peak within 30 min. Further challenges resulted in smaller, delayed rise and persistence of elevated GH levels. Insulin levels tended to increase with arg stimulus, but were not significantly elevated except at extremely high doses of arg. The data reflects a consistent relationship between arg stimulus and serum GH. / Master of Science / incomplete_metadata

Bibliography: leaves 281-316. Presents investigations on pubertal development in South Australian merino ram lambs and examines the effect of active and passive immunizations against oestradiol-17ℓ or oestrone on testicular maturation.

Serum cortisol and immunoglobulin G (IgG) concentrations were measured to investigate the relationship between vitamin A status and immune function in lambs. Twenty-four crossbred ewe lambs were each fed 900 g·d-1 of a carotene—deficient diet composed of 95.5% whole oats, 3% molasses, .5% trace mineral salt and 1% limestone. All lambs were injected monthly with vitamins D and E and with selenium. The 12 control lambs also received a 100,000 IU oral dose of vitamin A palmitate in capsule form every 2 wk. All lambs were challenged by injecting them with 1 mg ovalbumin in 1 ml of Freund’s complete adjuvant. At the time of challenge, serum vitamin A levels for the control and A-deficient (A—def) lambs were 33.3 and 3.1 ug·dl-1 respectively. Blood was collected prior to and 6, 13, 20 and 34 d post—challenge. The lambs were then reschallenged using the same antigen and blood was obtained 1, 2, 6 and 22 d post—challenge. Lambs were sacrificed at the end of the second challenge period. Spleen weights were obtained and gross post—mortem observations were made at this time. / Master of Science

Abstract not available

Abstract not available

Invitro synthesis and degradation capabilities and the cathepsin D activity of the skeletal muscles of experimentally induced Selenium-Vitamin E deficient lambs were investigated. Twenty-one Dorset x Coopworth x Suffolk lambs were blocked by weight and assigned to one of the following treatments: 1) a basal diet of 85% whole shelled corn and 15% mixed grass hay plus a mineral supplement that was low in Se and E (-Se-E), 2) the basal diet and deficient mineral mixture as fed in treatment 1 with the addition of a casein encapsulated fat supplement (-Se-E+fat), 3) the basal diet plus a mineral mixture which contained supplemental Se and E (+Se+E). Upon completion of the feeding trial, lambs which had been receiving the -Se-E treatment had the greatest body and individual muscle weights. The -Se-E+fat treatment had the lowest degradation rates and the highest synthesis rates. Cathepsin D activity was found to be lowest in the -Se-E+fat treatment. The -Se-E treatment was observed to have the highest degradation rate and the next highest synthesis rate indicating an increased rate of muscle turn-over. In all cases, the degradation rates were positively correlated with cathepsin D activity. / Master of Science

This thesis sets out to identify physical and physiological differences between lambs of different birth ranks at birth, and to use this information to identify practical on-farm management strategies which could improve triplet-born lamb survival. Triplet-born lambs, especially the lightest-triplet-born lambs, not only had a greater capacity to lose heat but also had a reduced capacity to produce heat when compared to twin-born lambs. Due to their lighter birth weights, triplet-born lambs had lower plasma thyroxine (T4) concentrations within the first 24 hours of life than twin-born lambs, and within twin- and triplet-born litters, the lightest- and medium-triplet-born lambs had greater plasma lactate concentrations than all twin-born lambs and the heaviest-triplet-born lambs. Independent of lamb birth weight, triplet-born lambs had lower plasma tri-iodothyronine (T3) concentrations within five minutes of birth, and within twin- and triplet-born litters, the lightest- and medium-triplet-born lambs had lower plasma T4 and T3 concentrations within five minutes of birth than all twin-born lambs and the heaviest-triplet-born lambs. It was hypothesised that because triplet-born lambs had a lighter birth weight and lower plasma thyroid hormone concentrations, they would have inadequate thermoregulatory capabilities when compared to twin-born lambs. The lower rectal temperatures of triplet-born lambs within the first hour of life and the lower heat production on a per lamb basis at 24 to 36 hours of age, and the lack of difference in maximum heat production on a per kg of birth weight basis at 24 to 36 hours of age support this hypothesis. Two practical on-farm management strategies trialled in this thesis to improve triplet-born lamb thermoregulation were offering concentrate supplement during late pregnancy to improve lamb birth weights, and maternal iodine supplementation to improve lamb plasma thyroid hormone concentrations. While offering concentrate showed positive effects such as increasing lamb birth weights, colostrum uptake and triplet-born lamb heat production on a per kg of birth weight basis, the results were either inconsistent across experiments or between birth ranks suggesting additional work is required to determine the repeatability and cost effectiveness of these findings. Maternal iodine supplementation offered no iv | P a g e benefits in terms of lamb birth weights, plasma thyroid hormone concentrations or lamb heat production. Further investigations identified that lamb birth weights, thyroid hormone concentrations, glucose and NEFA concentrations are positively associated with maximum heat production at 24 to 36 hours of age. Practical on-farm management strategies which could target these physical and physiological factors may improve triplet-born lamb heat production, and therefore the survival rates of triplet-born lambs.