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A four-chamber indirect calorimeter was constructed to evaluate energy utilization by laying hens as affected by dietary energy, protein and amino acid levels and by housing temperature. Heat production was measured by indirect calorimetry and metabolizable energy was determined for each diet. Net energetic efficiency was calculated as the slope of the regression of energy balance (metabolizable energy intake - heat production) on metabolizable energy intake. Hens fed diets formulated without protein specifications to provide amino acid levels equivalent to those provided by 14.5 or 16% protein, had higher (P < .05) net energetic efficiencies than hens fed diets formulated with specified protein levels. Addition of 3% animal fat to the higher (16% protein) amino acid diets produced the greatest increases (P < .05) in net efficiency, but decreased (P < .05) efficiency in the lower (14.5% protein) amino acid diet formulated without a protein specification. Metabolizable energy available for production was improved (P < .05) with animal fat additions to all but the diet formulated to the higher (16% protein) amino acid levels. Animal fat, cottonseed oil, corn oil, cod liver oil and safflower oil were used to determine effects of fat source on energy utilization by laying hens at 21.1 C. Higher net efficiencies were obtained for the cottonseed and safflower oil diets (99.1 and 99.8%, respectively) than for the basal diet (90.6%) or the other fat sources (cod liver oil = 86.0%, corn oil = 87.3%, animal fat = 91.1%). Full vs. meal (two 1-hr periods daily) feeding and total sulfur amino acid deficiency effects on energy utilization were evaluated. Meal feeding reduced (P < .05) metabolizable energy available for production while increasing (P < .05) maintenance metabolizable energy requirements. Feeding regime did not reverse the decline (P < .05) in net efficiency (89.2-89.7 to 81.7-82.6%) observed with total sulfur amino acid deficiency. Hens were fed either 7% animal fat or 7% corn oil and maintained at 10, 21.1 and 32.2 C to study effects of fat source and temperature on energy utilization. From 10 to 32.2 C, net energetic efficiency increased from 87.6 to 92.6% with animal fat. Corn oil showed the highest net efficiency (93.9%) at 10 C, while animal fat was highest (92.6%) at 32.2 C. Hens fed animal fat required the most (P < .05) maintenance metabolizable energy and had the highest (P < .05) fasting heat productions at each temperature.

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Call number: LD2668 .T4 1985 R336 / Master of Science

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The objectives o-f this research were to investigate the effects of blending Canbra or Canola oil with other oils or fats on the nutritive value and autoxidative stability of the blended oils, and to investigate the possibility of using hydrolyzed oils (free fatty acids) in the study of fatty acid balancing. Canbra oil (containing 6.1% erucic acid) was blended with sunflower oil or animal lard 1/1 (w/w). Canola oil (0.55% erucic acid) was blended with sunflower oil in the ratios 9/1, 8/2, 7/3, 6/4 and 5/5. The nutritional value was assayed using growing chicks fed lipid at 3% in a practical diet during a 4 week feeding period. Evaluation was made using body weight, weight gain, feed consumption, feed conversion, feed digestibility, lipid digestibility, total fatty acid digestibility, metabolizable energy and individual fatty acid digestibility. Results show that Canbra oil is equivalent to animal lard but significantly inferior to sunflower oil. Blending Canbra oil and sunflower oil or animal lard improved chick growth and fatty acid utilization over that demonstrated by the Canbra oil alone. Canola oil was equivalent to sunflower oil and soybean oil in supporting chick growth. The 7/3 and 5/5 blends showed synergistic improvement in promoting growth, fatty acid, protein and metabolizable energy utilization. It was concluded that Canola oil is nutritionally equivalent to either sunflower oil or soybean oil and that blending with sun-flower oil further improved its nutritional value. Oil blending rendered no significant detrimental effects on stability. The fatty acids of hydrolyzed Canola and sunflower oil showed nutritive performance equivalent to that of the intact oils. The fatty acids of a hydrolyzed 5/5 blend of Canola oil and sunflower oil showed reduced absorption of some fatty acids and the fatty acids of hydrolyzed soybean oil showed reduced diet and fatty acid absorption relative to the intact oils. These results demonstrate that feeding hydrolyzed oils may be a useful method of investigating fatty acid balance but more research is required in this area. / Land and Food Systems, Faculty of / Graduate

Influence of light, dietary amino acid levels, feeding space, and ambient temperature on male broiler body weight, feed efficiency, percentage abdominal fat, and incidence and severity of leg abnormalities was studied in two experiments. Broilers subjected to intermittent light (1 hr on:2 hrs off) had heavier 49 day body weights, and similar feed efficiencies than birds given continuous illumination. Feeding high [106 and 114% of NRC for lysine and total sulfur amino acids (TSAA), respectively] versus low (100% of NRC for lysine and TSAA) amino acid diets, improved body weight and feed efficiency at market age. Providing broilers with increased feeding space (from 1.47 to 2.94 cm/bd) resulted in improved body weight at market age. Birds under high ambient temperatures (29 to 26° C) had significantly higher feed efficiencies at four weeks of age than those given low temperatures (29 to 18° C). However, at market age broilers provided low temperatures had significantly greater gains with similar feed efficiencies. Birds fed high amino acid diets had significantly more abdominal fat than those given low amino acid diets. Light, feeding space, ambient temperature and relative humidity had no significant effect on percentage abdominal fat. Broilers provided intermittent light had significantly fewer and less severe leg abnormalities than birds under continuous illumination. Dietary amino acids, ambient temperature and relative humidity had no significant effect on the incidence or severity of the leg disorders. / Master of Science

Four experiments were conducted to compare adipocyte dynamics and body composition among adult chickens from lines differing in growth rate and feed consumption. In Experiment I, forced caloric overconsumption increased weight gain and fat deposition, with concomitant increases in the total adipocyte DNA content of the assayed fat depots. Injections of DNA-specific [methyl³H] thymidine resulted in higher radioactivity levels in the fat depots of forced versus ad libitum or restricted-fed birds. Evidently, stimulation of fat deposition in adult chickens can be associated with adipocyte hyperplasia. A second experiment was conducted to histologically examine the effects of forced caloric overconsumption on adipocyte size, number, and distribution in the retroperitoneal fat depot of adult weight-line birds. Similarly to Experiment I, force feeding increased fat deposition, resulting in increases in the retroperitoneal fat depot total adipocyte DNA content. The lipid/adipocyte DNA ratio also decreased during rapid depot expansion. This resulted in an increase in the small adipocyte population of the force fed birds when adipocyte diameter was increasing. Subsequently, when the constraints of force feeding were removed, adipose depot reduction occurred, with the mobilization of lipid from small as well as large adipocytes. In a third experiment, the effects of estrogen administration and partial lipectomy were examined. In addition to the weight-line birds, a commercial broiler breeder stock was utilized. Estrogen administration depressed body weight gain and abdominal fat deposition when compared to placebo implanted birds. Partial lipectomy depressed body weight, fat deposition, and abdominal fat total adipocyte DNA content. Lipectomy modified several components of carcass composition without altering feed intake. No indication of a compensatory hyperplastic response to lipectomy was indicated. A final experiment was conducted examining the effects of forced body weight fluctuations on body composition of male and females from the weight-selected lines. Although numerous first-order interactions were detected, force-feeding resulted in transient modifications in carcass composition and fat deposition which were more apparent in the high than low weight line, in females than males. After release to ad Iibitum feeding, the differences resulting from force feeding were reduced. / Ph. D. / incomplete_metadata

Thesis (MScAgric)--University of Stellenbosch, 2000 / ENGLISH ABSTRACT: A flock of 500 Hybro broiler breeders were employed to study the effect of different levels of protein and energy on production and body composition. The daily lysine intake of the birds were 900, 1050, 1200 and 1350 mg respectively, each fed in diets with a daily energy intake of 1800 and 2000 kJ ME to provide a 4 x 2 factorial design. Lysine was used as the reference amino acid in the experiment and all other amino acids were kept in a constant ratio in every experimental diet. The total production was divided into 3 periods of 13 weeks each (week 23 - 35; week 36 - 48 and week 49 - 61) to determine the effect of the treatments over time. Production was evaluated by hen day production; egg weight (g/egg); egg mass (g/day); fertility; hatchability; chicks/hen/week; feed conversion and day old chick weight. Hen day production was significantly (P < 0,05) lower at the high energy intake for period week 49 to 61. Energy and protein levels significantly increased egg weight. Effect of protein was consistent during all three periods of production. Egg mass output had a significant (P < 0,05) response to increasing levels of protein for the total period of production. The birds on the high energy diet produced a significant higher egg mass per hen during the first period of production (week 23 - 35). Hatchability was reduced (P < 0,05) by the higher energy intake for the total period of production and this effect was very significant (P < 0,01) during the final period of production. Similar to hen day production, the higher energy had a significant (P < 0,05) negative effect on the amount of chicks produced. The well-known correlation between egg weight and chick weight was confirmed with the regression equation: Chick weight = 10,5 + 1,22 x Egg weight. Both energy and protein had a significant (P < 0,01) positive effect on chick weight. The feed conversion was lower at increasing levels of amino acid intake (P < 0,01). Higher energy intake significantly (P < 0,05) increased hen weight and protein had a very significant effect during the first period of production (P < 0,01). The isotope dilution technique (tritiated water) was used to estimate the body composition of the breeders. This was done at 5 different periods (week 27, 35, 43, 52 and 61) of the production period to establish changes in requirements over time. Significant correlation were found between carcass moisture and waterspace (R2 = 0,76); fat % and carcass moisture (R2 = 0,78); protein % and waterspace (R2 = 0,35) and fat % and waterspace (R2 = 0,46). The regression equations obtained from these correlation were employed to determine excess energy and lysine consumed at different ages. Energy requirements were calculated according to the effective energy (EE) system and the conventional ME system. According to effective energy the lower energy intake was not sufficient and the maximum requirement was calculated to be 1942 kj EE/day. The metabolizable energy calculations indicated sufficient intakes at every treatment with the maximum requirement 1746 kj ME/day. The lysine requirement was found to be in excess of 1050 mg lysine per day. The recommendation for daily lysine intake is 1200 mg/day and the energy intake of breeders should be 1900 to 2000 kj ME/day from week 23 to 35 and can be reduced to 1800 kj ME/day in the final period of production. / AFRIKAANSE OPSOMMING: Om die effek van verskillende vlakke energie en proteïen op produksie en liggaamsamestelling te ondersoek is 'n trop van 500 Hybro braaikuiken teelouers gebruik. Die daaglikse lisien inname van die henne was onderskeidelik 900, 1050, 1200 en 1350 mg, wat elk by 'n daaglikse energie inname van 1800 en 2000 kJ ME verskaf is, in 'n 4 x 2 faktoriale ontwerp. Alle aminosure is in 'n konstante verhouding met die verwysings aminosuur lisien in die rantsoen ingesluit. Om te evalueer of daar veranderinge oor 'n tydperk plaasvind weens die verskillende behandelings is die produksie periode in drie periodes van 13 weke elk verdeel (week 23 - 35; week 36 - 48 en week 49 - 61). Die produksie standaarde wat gemeet is, is hen dag produksie, eiergewig (g/eier), eiermassa (g/dag), vrugbaarheid, uitbroeibaarheid, kuikens/hen/week, voeromset en dagoud kuikenmassa. Hen dag produksie was betekenisvol (P < 0,05) laer by die hoër energie innames in die laaste periode van 49 tot 61 weke. Energie en proteïen het eiergewig betekenisvol (P < 0,01) verhoog. Die effek van hoër vlakke proteïen was konstant in alle produksie periodes. Die daaglikse eiermassa (g/dag) het ook saam met stygende vlakke proteïen verhoog en hierdie effek was vir die totale periode van produksie. Energie het die eiermassa in die eerste periode van produksie (week 23 - 35) verhoog. Uitbroeibaarheid is verlaag (P < 0,05) vir die totale periode van produksie deur die hoër energie inname en die effek was selfs groter (P < 0,01) in die finale periode van produksie. In ooreenstemming met die hen dag produksie is die aantal kuikens geproduseer negatief beïnvloed deur die hoër energie inname (P < 0,05). Die korrelasie wat bestaan tussen eiermassa en kuikenmassa is bevestig deur die regressie: Kuikenmassa = 10,5 + 1,22 x Eiermassa. Energie en proteïen het kuikenmassa betekenisvol (P < 0,01) verhoog. Voeromset was laer by stygende vlakke van proteïen inname (P < 0,01). Die hoër energie inname het henmassa ook betekenisvol (P < 0,05) verhoog en proteïen het dieselfde effek slegs in die eerste periode van produksie gehad (P < 0,01). Die liggaamsamestelling van teelhenne is bepaal met behulp van die isotoop verdunnings tegniek (tritium water). Dit is bepaal op 5 verskillende stadiums in die produksie periode (week 27, 35, 43, 52 en 61) om die moontlike verandering in behoeftes oor tyd vas te stel. Betekenisvolle korrelasies is gevind tussen karkasvog en die waterspasie (RZ= 0,76); vet % en karkasvog (R2 = 0,78); proteïen % en waterspasie (R2 = 0,35) en vet % en waterspasie (R2 = 0,46). Die regressie vergelykings van hierdie korrelasies is gebruik om die hoevelheid surplus energie en lisien ingeneem te bepaal. Die" effective energy" sisteem en die konvensionele ME sisteem is gebruik in die bepaling van energie behoeftes. Volgens die " effective energy" was die energie inname nie voldoende by die laer energie innames nie en die maksimum behoefte is bereken as 1942 kJ EE/dag. Die maksimum energie behoefte volgens metaboliseerbare energie is bereken as 1746 kj ME/dag. Die lisien behoefte moet hoër as 1050 mg/dag wees. Die aanbeveling van die daaglikse lisien inname is 1200 mg/dag en die energie inname moet 1900 tot 2000 kj/dag wees tot 35 weke produksie en kan daarna verlaag word na 1800 kJ ME/dag.