Typescript (photocopy) Includes bibliographical references (leaves 223-249) Investigates the relationship between feed conversion efficiency and physiological variables among several lines, generations and breeds of hen fed ad libitum or on restricted amounts of feed; and, of the consequences to egg shell quality of restriction of food supplied to laying hens.

Thesis (MTech. degree in Agriculture.)--Tshwane University of Technology, 2011. / A ten week feeding trial was done with layer hens from 18 weeks of age to investigate whether cowpeas can be used as a single protein source for egg production.

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Typescript (photocopy) / Includes bibliographical references (leaves 223-249) / 249 leaves, [10] leaves of ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the relationship between feed conversion efficiency and physiological variables among several lines, generations and breeds of hen fed ad libitum or on restricted amounts of feed; and, of the consequences to egg shell quality of restriction of food supplied to laying hens. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Physiology, 1982

Typescript (photocopy) / Includes bibliographical references (leaves 223-249) / 249 leaves, [10] leaves of ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the relationship between feed conversion efficiency and physiological variables among several lines, generations and breeds of hen fed ad libitum or on restricted amounts of feed; and, of the consequences to egg shell quality of restriction of food supplied to laying hens. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Physiology, 1982

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In 1957, strains 3 and 4, two highly selected but unrelated strains of Single Comb White Leghorn chickens from Agriculture Canada's Animal Research Station at Ottawa were crossed to establish the Agassiz strain (strain 6). Further selection was imposed on strain 6 for improvements in hen-housed egg production (HHEP) based on part-records to 273 days and maintenance of egg weight, fertility, hatchability and viability. Data from 1957 to 1963 were analysed utilizing the SAS programs. There were no significant improvements in performance for HHEP, but egg weight, fertility, hatchability and viability were maintained. The lack of response to selection for HHEP was probably due to the following reasons: 1) too many traits were considered in the selection program at the same time, 2) negative genetic correlations existed among the selected traits, 3) strict adherence to a selection scheme was not practiced, 4) most of the traits under selection had low heritabilities, 5) the duration of the study was not long enough, and 6) the population size of strain 6 may not have been large enough. There was a significant decrease in body weight at 365 days (-4.33 ± 0.48, p < 0.0009). This decrease may be because of selection within full-sibs for more refined birds with better conformation as parents of the next generation. There were significant decreases in egg specific gravity at 225 and 450 days, and in Haugh units at 225 days, although Haugh units were increasing when measured at 450 days. The mean h²s for HHEP was 0.45, and the mean h²s for egg production to 273 days was 0.20 and the mean h²d for the same trait was 0.33. The mean h²s and h²d estimates for egg weight at 225 days were 0.60 and 0.50, respectively. The mean h²s and h²d for age at sexual maturity were 0.22 and 0.33, respectively, and those for body weight at 365 days were 0.53 and 0.62, respectively. The mean h²s and h²d for egg specific gravity at 225 were 0.64 and 0.33, respectively while those for Haugh units at 225 days were 0.57 and 0.68, respectively. These estimates were consistent with those found in the literature. The sctual selection differentials showed that selection was positive for egg production, while those for egg weight at 225 days were zero, and those for body weight at 365 days showed that selection was in the downward direction on the sires. / Land and Food Systems, Faculty of / Graduate

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