Semen from 70 males of the White Leghorn and Broad Breasted White parental breeds and their F1 generation of reciprocal crosses was used to artificially inseminate over 500 females. Some 6,000 eggs obtained from the inseminated females were examined for fertility. [...]

Chicken strains divergently selected for either abdominal fat deposition, avian leukosis (ALV) resistance or Marek's disease (MD) resistance were analyzed for restriction fragment length polymorphism (RFLP) in the growth hormone gene (GH). A total of four polymorphisms were identified, one at a SacI restriction site (PS1) and three at MspI restriction sites (PM1-PM3). Restriction mapping indicated that all polymorphisms were in exons and/or introns and not in flanking regions of the gene. Selection for abdominal fat composition significantly affected the frequency of polymorphisms at PM2, but not at the other restriction sites (p $<$ 0.0004). The PM2$ sp{+}$ allele (presence of a restriction site) was fixed in the fat line and occurred at a frequency of 63% in the lean line. Selection for ALV-resistance resulted in significant differences in the frequency of polymorphisms at PS1 and PM3. Selection for MD resistance also affected the frequency of polymorphisms at PS1 and PM3.

No description available.

No description available.

Radioreceptor binding studies were carried out in broiler chickens in order to characterize adrenergic receptors on their abdominal fat adipocytes. The radioligands ($ sp3$H) DHA and ($ sp3$H) YOH were used to identify $ beta$- and $ alpha sb2$-adrenoceptors respectively. The determination of receptor criteria indicated that the optimal protein concentration for the simultaneous binding of both receptor types was between 0.35 and 1.0 mg/ml. Pharmacological specificity for both $ beta$- and $ alpha sb2$-adrenoceptors was demonstrated using receptor specific antagonists and an agonist. Saturation isotherms indicated that ($ sp3$H) DHA and ($ sp3$H) YOH labelled with high affinity, a homogenous population of non interacting $ beta$- and $ alpha sb2$-binding sites respectively. Scatchard analysis of the saturation data for ($ sp3$H) DHA revealed a Kd value of 8.1 nM and a Bmax value of 420 fmol/mg protein, while ($ sp3$H) YOH binding had a Kd value of 7.0 nM and a Bmax value of 68 fmol/mg protein. The variation in $ beta$- and $ alpha sb2$-adrenoceptor binding parameters was then investigated on the abdominal fat pad adipocytes of male and female broiler chickens at 4, 6 and 9 weeks of age. Scatchard analysis of the binding data for $ beta$-adrenoceptors indicated that Bmax values were greater in male and female broilers at 9 weeks of age (p $<$ 0.05) and that overall Bmax values were greater in females than in males (p $<$ 0.05). Scatchard analysis of $ alpha sb2$-adrenoceptor binding revealed that in females Bmax values remained constant but differed at all ages in males. The $ beta$-adrenoceptor Bmax values were always significantly greater (p $<$ 0.05) than the corresponding $ alpha sb2$-adrenoceptor Bmax values. / These results established for the first time the existence of adrenergic receptors on broiler chicken adipocytes using a radioreceptor binding assay. Although the physiological implication of these receptors is not known, it is a critical step toward the understanding of the influence of the adrenergic system on adipose tissue metabolism in avian species.

The objectives of this study were to identify genetic variants, develop the respective haplotypes (combination of alleles) and investigate the association of identified variants with economically important traits in two candidate genes. The first gene was Phosphoenolpyruvate carboxykinase (PEPCK) which is a key regulatory enzyme of gluconeogenesis. The second candidate gene, Ornithine decarboxylase (ODC), is a rate-limiting enzyme in polyamine biosynthesis. It has a significant role in DNA synthesis and cell proliferation. We first analyzed the genetic variability of PEPCK-C, the gene which codes for the cytosolic form of PEPCK. A 3792 by segment of 5'-region of the PEPCK-C gene (pos. -1723 to 2069) was sequenced in 32 White Leghorn chickens (a total of 64 genomes). A total of 19 single nucleotide polymorphisms (SNPs) were identified. We then analyzed the genetic variability of ODC. A 5 kb sequence of 3' end of the gene was sequenced in 20 White Leghorn chickens (a total of 40 genomes). A total of 63 variant sites were identified. The rate of insertion/deletion in ODC was 16%, whereas neither deletions nor insertions were present in PEPCK-C. Gene trees were constructed for both genes assuming maximal parsimony. This led to the delineation of 6 haplotypes in PEPCK-C. Two of the SNPs coincided with RFLP detectable by the restriction enzymes AciI and BstEII, respectively. Three haplotypes in ODC were defined. In the next step, White Leghorn chickens from a non-selected closed population were typed for these two PEPCK-C RFLP. The two RFLP gave rise to three alleles (or haplotype classes), which in turn defined six genotypes. A comparison of genotypes revealed significant differences in feed efficiency (FE) and residual feed consumption (RFC). There was significant interaction between PEPCK-C genotypes and mitochondrial PEPCK (PEPCK-M) genotypes defined by an RFLP. The latter enzyme catalyzes the same reaction, but is located in the matrix of t

No description available.

No description available.

Biological and economic efficiencies of major genes for feather reduction (naked neck and frizzle) and body size reduction (dwarf) in a dual purpose layer strain were evaluated in the subtropical coastal region of South-East Africa (Maputo, Mozambique). The experimental material consisted of eight different genetic groups, two diets (14.4 and 16.2% crude protein) and two climatic seasons. Birds were caged individually in an open-side shelter with natural light. Traits measured were: temperature and relative humidity, body weight, age at first egg, egg weight, egg production, egg quality, feed intake and mortality. The following were calculated: temperature-humidity index (THI), growth rate, persistence, egg mass, feed efficiency, feed conversion, biological efficiency (EM/BWO.75) and productivity (EN/BWo. 75). The main results show that: (1) none of the feather-reduced genes significantly improved egg production or the efficiency of feed utilization, although the naked neck (Na) excelled in terms of the number and mass of eggs produced per metabolic body weight; (2) the dwarf gene (dw) was associated with delayed sexual maturity, production of fewer and lighter eggs, higher persistence, better feed conversion and higher survivability; (3) climatic seasonal effects were observed in all traits analysed, with elevated temperatures restraining body weight gain, the number and weight of the eggs produced, and voluntary feed intake; (4) the lower dietary protein content resulted in decreased egg weight. It was concluded that the normal feathered dwarf is the most suitable genetic group for peri-urban and rural production systems in this region. / Thesis (PhD (Animal Science))--University of Pretoria, 2007. / Animal and Wildlife Sciences / unrestricted

Genetic and nongenetic influences on organ development in chickens were studied. Populations included lines divergently selected for juvenile body weight, reciprocal F₁ crosses between them, and a commercial broiler-breeder parent line segregating for early and late feathering alleles. Nongenetic influences included restricted and <i>ad libitum</i> (AL) feeding regimes. Positive correlated responses to selection for body weight included proportionally larger breast, legs, fat depots and small intestine. Negative responses included fecundity, feather and gizzard weights. The degree of non-additive genetic variation differed among traits but reciprocal effects were negligible. Weights and lengths of organs at specific ages did not necessarily reflect the situation at common body weights suggesting differences in resource allocations among populations. In commercial meat-type chickens, AL feed consumption was near gut capacity and increased rapidly to approximately 140 days of age. Concomitantly, body weights increased to approximately 130 days and then plateaued. Influences of early and late feathering alleles were minor except for weights of feathers. Alternate-day feeding prior to sexual maturity reduced weights of fat depots, feathers and muscles and increased size of the gastrointestinal tract. Effects of every day, skip-one-day and skip-two-day restrictions of feed were generally similar. Chickens adapted quickly to restricted feeding but, when released to AL feeding allocated resources into growth. This reallocation reduced their resistance to an <i>Escherichia coli</i>challenge. Prior to sexual maturity, relative weights and lengths of the gastrointestinal tract decreased with age and relative sizes of fat depots and muscle increased with age. Thereafter relationships of most organs to body weight remained stable. Restricted chickens adapted to fasts by maintaining exogenous energy stores (gastrointestinal tract contents) for longer periods. Unlike those fed AL, they did not became obese and their livability and fecundity were greatly enhanced. / Ph. D.