Graduation date: 1984

Graduation date: 1979

A series of trials was conducted with Polypay (P), Coopworth (CP), Hampshire (H), and crossbred ewes over a two year period at three locations to assess the effects of ewe body condition and pre-lambing supplementation on ewe productivity. Supplementation trials were conducted at all three locations in Year 1 using P (OSU), CP (Farm 1), and crossbred ewes (Farm 2), and at OSU in Year 2 using P ewes. Supplementation consisted of one pound of whole corn daily in addition to the routine ration being fed to the controls. Supplementation began four weeks prior to lambing and continued to parturition. Body condition trials were conducted concurrently at OSU using CP, H, and crossbred ewes in the first year and CP ewes in the second year. A body condition trial was also conducted at Farm 1 (CP ewes) in the second year. At OSU, Polypay ewes were mated to CP, P, and H rams, CP ewes were mated to CP and H rams, and H ewes were mated to H rams. On the commercial farms, CP ewes (Farm 1) were mated to CP rams, and crossbred ewes (Farm 2) were mated to Suffolk rams. Ewes in supplementation trials were condition scored on a five point scale(1=very thin; 5=very fat)at the time of allocation to treatments six weeks pre-lambing, and ewes in all trials were scored one week prior to lambing. In addition, in Year 2 P and CP ewes at OSU were scored and weighed at mating, post-mating, mid-gestation, pre-lambing, and weaning. Production traits recorded included litter size at birth, total weight of lamb born (TWB), lamb survival, and individual lamb weaning weights (WWT). The various components were combined to calculate total weight of lamb weaned (TWW) by each ewe as the measure of total lamb production. In most trials, higher ewe body condition score pre-lambing (CSL) was associated with heavier TWW. The heavier TWW was the result of both increased lamb survival and heavier individual lamb WWT. Supplementation increased both CSL and subsequent TWW; the increase in TWW was accounted for entirely through improved CSL. The response to supplementation was not consistent over ewe genotypes; crossbred ewes showed a greater increase in CSL than purebred ewes, and likewise a greater response in TWW. While supplementation increased ewe productivity, a comparison of control vs supplemented ewes which were at the same body condition prelambing (CSL = 3.0) indicated that ewes which were previously thin did not perform as well as ewes which had been maintained in good condition throughout gestation. While supplementation raised their CSL to the same level, their lambs exhibited both lower survival and lighter WWT. Comparison of the expense of supplementation with the increased TWW indicated a feed cost of about $.30 per extra pound of lamb weaned. At typical lamb market prices of $.60/lb, identification and supplementation of thin ewes pre-lambing would be a profitable management strategy for sheep producers. / Graduation date: 1994

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on June 11, 2009). Includes bibliographical references.

The feeding biology of three euphausiid species, Euphausia vallentini (adults and juveniles), E. longirostris and Nematoscelis megalops was investigated during austral autumn (April/May) of 1998 and 1999, in the vicinity of the Prince Edward Islands (Southern Ocean). Data on the abundance and biomass of these species, estimated from bongo net tows, were investigated. Trophic position was assessed using gut contents and stable nitrogen isotope measurements. Feeding rate and daily carbon ration were estimated using the gut fluorescence and the gut fullness techniques. Vertical migrations into the surface waters at night were found to be strong for Euphausia vallentini adults and juveniles. Associated with these migrations were clear diel feeding patterns. Insufficient data during daylight hours for E. longirostris made it impossible to determine diel feeding patterns, but high feeding activity did occur during dark hours. Nematoscelis megalops did not show any distinct diel feeding pattern, but slightly higher gut fullness indices in the late afternoon suggested that feeding activity may have been highest during this period. For both Euphausia spp. high gut pigment levels were recorded in 1999, which corresponded to higher ambient chlorophyll a concentrations for that year. Highest initial gut pigment levels and highest ingestion rates were found for Euphausia longirostris in both years and lowest values were observed for N. megalops. High phytoplankton and low metazoan contributions to the diet of Euphausia vallentini juveniles, as shown in the gut content analysis, and low stable nitrogen isotope ratios (ð¹⁵N = 1.39±0.31), both indicated that this group was principally herbivorous. The results of gut content analysis of the adults of E. vallentini were similar to those of the juveniles, however, stable nitrogen isotope results showed that there was a higher degree of omnivory (ð¹⁵N = 3.81±0.66). Daily ration estimates from the gut fluorescence and fullness techniques showed that between 3.3 and 25.7 % of E. vallentini adults total daily carbon ration was derived from autotrophic sources. Although the contribution of carnivory to the diet was difficult to determine, the adults of this species may be considered omnivorous. Irrespective of the degree of carnivory, a dietry shift with an increase in size was evident for this species. Gut content analysis for Euphausia longirostris showed that this species consumed large amounts of both phytoplankton and metazoan prey and this was reflected in the stable nitrogen isotope results (ð¹⁵N = 6.88±0.60). These findings were supported by the results of the daily carbon ration estimates which showed that autotrophic carbon contributed between 6.9 and 20.3 % of the daily carbon consumption. The gut content analysis suggested that N. megalops was omnivorous, and the stable nitrogen isotope results place it in a trophic position equivalent to that of E. longirostris (ð¹⁵N = 6.83±0.78). Calculations from daily ration estimates suggested that only 3.1 % in 1998, and 3.2 % in 1999, of the carbon ingested was of autotrophic origin. This species may therefore be considered carnivorous. Implications of the findings of this study are discussed in terms of carbon cycling in the Southern Ocean.

Tydens embrio ontwikkeling groei weefsel deur selvermeedering, maar soos wat soogdiere volwassendheid nader vind groei net plaas deur sel vergroting. Volwassenheid word beskou as wanneer spiergroei ‘n maksimum bereik. Groei sluit die neerlegging van vet in, maar spiermassa is van primêre belang. Die groeikurwe (Fig 1) waarin massatoename teenoor ouderdom vergelyk word, volg ‘n sigmoidale kurwe (Owens et al, 1993). Onder ideale toestande is die groeitempo van lammers relatief konstant van kort na geboorte totdat die helfte van volwassemassa bereik word, waarna dit geleidelik afneem tot volwassenheid (Black, 1983). Die afname in groeitempo begin gewoonlik met die bereiking van puberteit (Owens et al, 1993).

Magister Scientiae - MSc (Biodiversity and Conservation Biology / Beach-cast kelp (the most widely used feed for commercially grown South African abalone) is plentiful during winter months when periodic storms cause kelp to wash ashore. During summer, however, this resource is not always readily available and farmed abalone are often starved for short periods. The aim of this research was to assess how periodic kelp starvation influences growth of the commercially grown abalone, Haliotis midae Linnaeus. / South Africa

Please read the abstract in the section 00front of this document / Thesis (PhD Agric (Animal Science))--University of Pretoria, 2006. / Animal and Wildlife Sciences / unrestricted

An investigation was carried out into the effects of some dietary factors on the serum cholesterol and serum total lipid levels in both normal and hyperthyroid chicks. Dietary factors investigated were the effects of two levels of protein, two levels of fat, and two levels of vitamins. Basal diets were fed at either a 20% or 26% protein level and when dietary fat was investigated the dextrose of the basal diet was substituted for a hydrogenated vegetable oil to make up 12% of the diet. The vitamin supplement in the high vitamin diets fed consisted of additional amounts of the following B complex vitamins: choline chloride, calcium panthothenate, folacin, niacin and riboflavin. Chicks were rendered hyperthyroid by feeding diets containing 0.02% iodinated casein. Hypothyroidism was induced by the feeding of 0.1% thiouracil. Normal chicks showed lower levels of serum cholesterol and serum total lipids when they were fed basal diets consisting of 26% protein level than when fed basal diets consisting of a 20% protein level. Normal chicks fed high fat diets showed higher levels of serum cholesterol and serum total lipids than normal chicks fed low fat diets. Normal chicks fed diets low in the B complex vitamins showed higher levels of serum cholesterol than normal chicks fed diets high in the B complex vitamins. The growth rate of chicks rendered hyperthyroid varied. In many instances hyperthyroid chicks grew at a significantly faster rate than normal chicks while in some instances no differences were noted. In some cases chicks rendered hyperthyroid showed depressed growth rates. No clear explanation could be given for such an effect on the growth rate of hyperthryoid chicks. It seems reasonable, however, to suspect that seasonal changes may affect thyroid activity and consequently the growth rate of the chicks in question. No differences were noted between the serum cholesterol and serum lipid levels from hyperthryoid chicks fed the basal diets containing 20%, and 26% protein. Hyperthyroid chicks, however, showed lower levels of serum cholesterol than normal chicks when the diet fed was low in the B complex vitamins, calcium panthothenate, choline chloride, folacin, niacin and riboflavin. The effect on the serum cholesterol and serum total lipids when the chicks were rendered hyperthyroid varied. The results suggest some interaction between thyroid state and diet on the serum cholesterol and serum total lipids. / Land and Food Systems, Faculty of / Graduate

A series of experiments were conducted to investigate the need by poultry for unidentified factors for maximum growth, egg production, fertility, hatchability and viability. Dehydrated cereal grass and dehydrated alfalfa were fed as supplements to a practical poultry diet. Data collected included body weights, feed consumption, egg production, fertility, hatchability and viability. The experiments were continued through three generations of birds in order to study any long term effects. In order to Investigate the possibility that bacterial synthesis provided a source of unidentified factors In the litter one additional group of adult birds was fed a basal diet and maintained on deep litter while another receiving the same diet was maintained on a raised wire floor. It was found that neither 2.5 nor 5 percent of either dehydrated cereal grass or dehydrated alfalfa had any effect on growth, maintenance of body weight, efficiency of feed utilization, egg production, fertility or hatchability. The presence of dehydrated green feed in the diet reduced the incidence of mortality in chicks during the period from 4 to 12 weeks of age. This effect was noted only when the chicks were under stress due to severe infection with coccidiosis. The dehydrated green feeds had no effect on the incidence of mortality during the first 4 weeks of age, the late growing stage, or the period of egg production. These results indicated that under normal conditions the Ingredients of the basal diet provided adequate amounts of the unidentified factor(s) present in dehydrated green feed. In addition, bacteria synthesis in the litter appeared to provide a source of an unidentified factor necessary for high hatchability. Another series of experiments were conducted in which chicks maintained in battery brooders were fed purified diets supplemented with dehydrated cereal grass, dehydrated alfalfa and forage juice. Various other supplements were added to the diet separately and in combination with the green feed supplements in. an attempt to determine the nature of the unidentified growth factor(s) present in green feeds. The additional supplements included herring meal, penicillin, lactose, the ash of dehydrated cereal grass and the ash of forage juice. In order to study the effect of maternal diet on the response of chicks to unidentified factors, the chicks used were from parent stock variously depleted of the unidentified factors. It was found that dehydrated cereal grass, dehydrated alfalfa and forage juice contain an unidentified factor required by chicks for rapid early growth. This factor differed from the factor present in herring meal. The response to either of these factors was dependent on the presence of the other in the diet. Both dehydrated cereal grass and forage juice, however, appeared to contain small quantities of the herring meal factor. The unidentified growth factor present in dehydrated cereal grass was shown to be carried over from the dam to the chick. The variability in growth rate of the chicks obtained from hens fed the control diet suggested that bacterial synthesis in the litter provided a source of the unidentified factor present in dehydrated green feed. The amount of the factor thus available to the hens varied as conditions were more or less favourable for bacterial growth. The nature of the factor(s) present in the green feed supplements is not clear. A growth response to the ash of dehydrated cereal grass and of forage juice was obtained as well as to the intact supplements. The balance among the various inorganic constituents of the diet may be involved rather than a single mineral. The fact, that a greater growth response was obtained from supplements which increased the acidity In the intestinal tract suggests that these supplements may act Indirectly by affecting the absorption of nutrients. / Land and Food Systems, Faculty of / Graduate