Evaluated were correlated responses to 54-generations of divergent selection for 8-week body weight (BW) and of BW at other ages and reproductive traits. Evaluated first was the influence of scaling on phenotypic responses to selection, phenotypic correlations of means and standard deviations, and unadjusted vs. standardized responses. Measured was BW at 4 (BW4), 8 (BW8), 24 (BW24), and 38 (BW38) weeks of age. Correlations between means and standard deviations were positive and greater in the LWS than HWS. Scaling masked the degree more than the pattern of response and was line specific with the magnitude of response greater in the LWS than HWS. While BW ratios across ages were not influenced by scaling in LWS, they were evident in HWS. Also measured were correlated responses of reproductive traits in selected and relaxed lines. Traits were age at first egg (AFE), body weight at first egg (WFE), their ratio (WAFE), and hen-day normal egg production (HDP). Although sexual maturity was delayed, the effect was more pronounced in the low than high weight lines. Selection for low BW decreased WFE, WAFE and HDP. Selection for high BW resulted in lower HDP, while WFE and WAFE were generally higher. Minimum AFE, WFE and WAFE in relation to sexual maturity were line specific. Opposition between relaxed and artificial selection resulted in a higher reproductive performance and fitness with relaxed than artificial selection. Overall, results demonstrate that correlated responses to long-term divergent selection were masked by scaling and negative correlated reproductive responses. / Master of Science

The investigation reported here involved truncation-type individual selection in divergent directions for body weight at eight weeks of age in White Rocks. Phenotypic changes of selection and unselected traits within lines were measured for females from the P₁ through the F₇ generation. Unselected traits were 24 and 38-week body weight, egg weight, age at first egg and percentage egg production to January 1. The following were analyzed and discussed: 1. Direct response of eight-week body weight to selection, 2. Correlated responses and estimates of realized heritabilities, 3. Genetic correlations between the selected and unselected traits, 4. Phenotypic and environmental correlations between selected and unselected traits, and 5. The prediction of correlated responses. The realized heritabilities of unselected traits based on the expected secondary selection differential were relatively uniform and consistent with those reported in the literature. Genetic correlations obtained from realized heritabilities of the selected and unselected traits were uniform and consistent with those of others. The significant increase of environmental correlations between selected trait and 24 and 38-week weight and percentage egg production during the eight generations indicated genotype-environment correlations. Such correlations may cause further difficulties in the development of a breeding stock possessing a large broiler weight, small adult weight and high egg production. Predicted correlated responses of these three traits were lower than the actual responses and may reflect these relationships. / Master of Science

The effects of genetic and social factors influencing ingestive behaviors, growth, livability, and dietary self-selection were investigated in three experiments. In Experiment I, ingestive behaviors, livability, and body weight were measured in lines of White Plymouth Rock chickens selected for high (HW) and low (LW) juvenile body weight reared in cages and floor pens as line-separate (S) and line-intermingled (I) flocks in three replicated trials. Body weights of Line HW chicks in cages, livability of Line LW chicks in cages, and ingestive behaviors of Line LW chicks in floor pens were higher in I than S flocks. Experiments II and III were designed to determine the ability of young chicks to discriminate among diets differing in amino acid content. In Experiment II, growth, feed intake, and feed preferences for diets varying in content of lysine, methionine, or tryptophan were measured in Line HW and a line of White Leghorns (HA) selected for high antibody response to sheep erythrocytes. Chicks were fed one of seven diets which were either balanced (Diet A), or slightly (1) or moderately (2) deficient in lysine (L), methionine (M), or tryptophan (T) for seven days. Chicks were then offered a choice between Diet A and the diet fed for seven days (3 to 10 days of age). Line HW chicks eventually showed a consistent preference for Diet A to all but Diet L1. For diet preference, interactions between time and diet were common in Line HW and the causes of these interactions were discussed. Line HA chicks preferred Diet A to M2, but otherwise did not choose between diets. Growth of Line HW chicks was reduced by feeding Diets L2, L1, and M2, but growth was not affected in Line HA. In Experiment III chicks from Lines HW, HA, and LW were provided a choice among diets with .85, .58, and .44 % methionine from one day of age. Line HW discriminated among diets with different methionine content from five days of age, but chicks did not make a consistent choice until after a period of deficiency. After a period of deficiency, Line HW chicks consistently chose the diet with .85 % methionine. Line HA chicks consumed more of the diet in slight excess of their methionine requirement and the reason for this is not clear. Line LW chicks did not discriminate among diets at any time during the trial. These results indicate that several factors interact to influence ingestive behaviors, growth, livability, and dietary self-selection in different genetic lines of chickens. / Master of Science

This study investigated the effects of dietary tyrosine or tryptophan supplementation on immunity and brain neurotransmitter levels after antigen challenge. Chickens were given 0.1%, 0.5% or 1% supplemental dietary L-tyrosine or L-tryptophan prior to the injection of sheep red blood cells (SRBC). The 0.1% tyrosine supplementation increased primary IgM and secondary IgG titers at some time periods in Leghorns and decreased secondary IgM titers at Day 5 in broilers, while 0.1% tryptophan addition decreased Leghorn secondary IgM titers and increased secondary IgG titers at Day 9 and broiler secondary IgM titers at Day 9. The phytohemagglutinin (PHA) wattle response in Leghorns and broilers and resistance of Leghorns to E. coli challenge were not affected with the 0.1% supplemental level. With higher levels, 0.5% tyrosine supplementation increased Leghorn primary IgM titers at Day 11. In broilers, 0.5 and 1% tryptophan supplementation decreased secondary total antibody titers at Day 2, while the secondary IgM titers at Day 6 with the 0.5% tyrosine supplementation were higher than those with 1% tyrosine or tryptophan supplementation. The 0.5% or 1% tryptophan supplementation also lowered stressed broiler primary IgM titers at Day 3. After pooling the titer results within two dietary supplemental levels (0.5% and 1%) of a given amino acid, the tyrosine treatment appeared to suppress antibody response in unstressed broilers, but not stressed ones, while tryptophan displayed a suppressive trend in broilers under both situations. Supplementation with 0.5% or 1% dietary tyrosine did not alter brain catecholamine or serotonin (5-HT) levels in Leghorns. In contrast, 0.5% or 1% dietary tryptophan supplementation generally increased 5-HT, and its metabolite 5-HIIAA, and S-HIAA/5-HT ratios in the diencephalon, telecephalon, and brain stem in Leghorns. Tryptophan supplementation caused a dose-response increase in S-IIT and S-IHIAA levels of the brain stem. The results demonstrated that 0.5-1% dietary tryptophan supplementation suppressed broiler, but not Leghorn, antibody response, and the mechanism was probably via enhancing 5-IIT synthesis and release. The results also suggested that lower levels (0.1-0.5%) of dietary tyrosine supplementation may enhance immune response in Leghorns and stressed broilers, but ingesting large quantity of tyrosine, occurred in broilers, suppresses the response. / Master of Science

Vocalizations of the domestic chicken were recorded and analyzed by quantitative and qualitative methods in two experiments. In Experiment 1, recordings were made from males and females from two lines of White Leghorn chickens housed in individual battery cages. Five call types: crow, disturbance call, baaks, fear-squawks, and moans were distinguished. No significant differences were found between lines for any of the parameters measured. Crows consisted of four parts, with the combination of the durations of the various segments suggesting that they contribute to recognition among individuals. Both sexes emitted disturbance calls, baaks, fear-squawks, and moans. When comparisons were made between sexes for number of disturbance notes per second and length of fear-squawks no significant differences were found. Signal grading was shown by increased rates of disturbance notes and the addition of baaks as an individual became more upset. Three groups of eight-week old White Leghorn chickens subjected to different handling regimes emitted different vocalizations when held in the hand of the observer. Birds habituated to the handler gave mainly contentment calls while the other groups emitted peeps (distress calls), fear trills or alarm notes. A previously unreported melodic flock call was heard from White Rock chickens that were moved to a new pen at eight weeks of age. Experiment 2 consisted of comparisons between two commercial egg-laying stocks maintained under high-intensity battery cage housing. Data obtained at approximately 35 weeks of age from both stocks in the same house showed low frequencies of pecks and threats. Pullets from stock B had significantly more pushes and steps than those from stock A. The vocalizations emitted by stock B exhibited an increased range of frequencies in comparison to those by stock A. This difference was attributed to an increased number of disturbance calls and baaks and suggests that vocal behavior may be a means of assessing the social environment of chickens maintained in battery cages. / M.S.

An attempt was made to study the effects of a tranquilizer (metoserpate hydrochloride), specifically designed for poultry, on the neonatal approach response of domestic chicks. Acquisition of this response was accomplished in a straight alley on birds ranging in age from 24 to 120 hours old. Testing of this response was done when all birds were 144 hours old under a no-drug condition. At 168 hours of age all subjects were subjected to extinction procedures. The strength of the response was measured in terms of latency to start as well as time spent traversing the alley. Resistance to extinction was measured in terms of the latencies mentioned above as well as number of trials to extinction. The results of the present study show a peak in imprinting susceptibility between 72 and 96 hours after hatching. The tranquilizer had a traditional interference effect except for those birds exposed on Day 3 while the injection control procedure had an enhancement effect on birds treated on Days 4 and 5. In addition, there were no differences observed during extinction between groups. / Master of Science

The first experiment was designed to determine if the antigenicity of egg yolk diluter could be eliminated by the addition of specific antibodies. Two virgin heifers were immunized with 20% yolk - 2.1% citrate - 7% glycerol with penicillin and streptomycin. Non-immune serum and immune sera having titers of 1:640 and 1:2560 were collected and frozen. Serum antibody titers were determined by the passive hemagglutination test. Utilizing equivalent proportions test it was determined that 80 volumes of anti-egg-yolk-diluent sera titered 1:2560 was necessary to neutralize 1 volume of 20% egg yolk diluent. The second experiment examined the effect of immune sera against egg yolk diluter upon the viability of bovine spermatozoa in that diluter. Using a split-ejaculate technique, 7 ejaculates from 3 bulls were diluted in egg yolk-citrate diluter or skimmilk diluter, cooled, glycerolated and stored at S°C. On the first day after semen dilution, complement-fixed immune serum titered 1:2560, 1:640 and non-immune serum were added to aliquots of diluted semen (1:9 v/v). Aliquots of each diluter without serum served as controls. Each treatment was evaluated immediately after addition of serum and again after 48 hr storage at 5°C. Percent intact acrosomes, percent motility and percent agglutination were measured from unfixed smears at 0, 3, 6 and 9 hr of incubation at 37°C. Both immune and non-immune serum treatments were characterized by head to head agglutination. Within both diluters, there were no significant differences in motility or intact acrosomes due to immune and nonimmune sera. However, all serum treatments were significantly higher (P < .01) in motility and percent intact acrosomes than the non-serum controls. The overall percent intact acrosomes across all hours, days and diluters were 77.9, 81.1, 81.2 and 81.7 for control, non-immune serum, 1:640 serum and 1:2560 serum, respectively. Differences in the percent head to head agglutination were not due to anitbody titer of the serum. / Master of Science

Prolactin-releasing peptide (PrRP) is an endogenous hypothalamic neuropeptide that when exogenously injected increases food intake in chickens, but decreases it in rodents and goldfish. We designed three sets of experiments to elucidate the mechanisms of PrRP's orexigenic effect in chicks. In experiment one, food and water intake were evaluated in chicks after receiving intracerebroventricular (ICV) injection of the vehicle, 0.75, 3, 12, 47 or 188 pmol PrRP. The administration of 12 and 47 pmol PrRP increased food intake for up to 120 min after injection, and 188 pmol increased it for up to 180 min. The lowest effective dose was 3 pmol, which increased food intake for up to 60 min after injection. Water intake was not affected. To investigate the molecular mechanisms, c-Fos immunohistochemistry was performed and mRNA expression of some appetite-associated neurotransmitters was measured in chicks that received either vehicle or 188 pmol of PrRP. The rostral paraventricular nucleus (PVN) was activated which coincided with increased neuropeptide Y (NPY) mRNA expression in the whole hypothalamus. In experiment two, food and water intake were evaluated in chicks fed a high carbohydrate (HC), high fat (HF) or high protein (HP) diet after ICV injection of vehicle, 3 or 188 pmol PrRP. Chicks fed the HP diet increased food intake at a lower dose than chicks fed HF and HP diets after ICV PrRP injection. In addition, ICV injection of vehicle, 3 and 188 pmol PrRP were performed in chicks fed all three diets, and ICV PrRP injection induced preferential intake of the HP diet over HC and HF diets. The expression of some appetite-associated neuropeptides in the hypothalamus was also measured in chicks fed the HC, HF or HP diet after ICV injection of vehicle or 188 pmol PrRP. There was a diet effect on mRNA abundance of all appetite-associated genes measured (P < 0.05), with greater expression in chicks fed the HF or HP than HC diet. While neuropeptide Y (NPY) mRNA abundance was similar between vehicle and PrRP-injected chicks that consumed HP or HF diets, expression was greater (P < 0.05) in PrRP- than vehicle-injected chicks that consumed the HC. In experiment three, the orexigenic effect of PrRP was tested in chicks selected for low (LWS) and high (HWS) body weight after central administration of vehicle, 24, 94 and 375 pmol PrRP. The LWS chicks had a lower threshold and higher magnitude of food intake increase in response to PrRP injection. Results demonstrate that PrRP is a potent orexigenic factor in chickens and that effects are likely mediated through the hypothalamus. The orexigenic effect of PrRP was influenced by dietary macronutrient composition, and diet in turn influenced the food intake response to PrRP. These results may contribute to a novel understanding of appetite regulation. / Master of Science

Marijuana has been used for medicinal and recreational purposes for thousands of years. Many people think of marijuana in the context of an illegal drug. Because of the antimarijuana attitude, research with cannabinoids was neglected for a long time. Although this substance is related to social problems, scientists are interested in its action and possible medicinal properties. Since the identification of the structure of Î 9--tetrahydrocannabinol, the main psychoactive ingredient of marijuana, there has been increased interest in this compound. Following the discovery of two cannabinoid receptors, CB1 and CB2 receptors, it was determined that CB1 receptors are in high density in the central nervous system while CB2 receptors are found primarily in the immune system. The endogenous cannabinoid ligands, anandamide and 2-arachidonoylglycerol, were observed in the central nervous system and peripheral tissues. Endocannabinoids differ from other "classical" neurotransmitters because they do not appear to be stored in synaptic vesicles, and they act as retrograde messengers within the brain. The endogenous cannabinoid signaling system includes cannabinoid receptors, their endogenous ligands called endocannabinoids, and the proteins for their synthesis and inactivation. The cannabinoid system appears to act as a neuromodulatory system. During the past ten years, the endogenous cannabinoid system has been implicated in a variety of physiological functions including pain reduction, motor regulation, learning, memory, and reward. Because obesity and eating disorders are prevalent, scientists are working at the molecular level to study the mechanisms controlling body weight and regulation of food intake. Several of the neuropeptides present in hypothalamic nuclei contribute to energy balance and food intake regulation. Endogenous cannabinoid and cannobinoid receptors are found in the hypothalamus and are associated with the regulation of food intake. Although the mechanisms whereby cannabinoids influence food intake remain unclear, results suggest that the cannabinoid system will be an important target in future studies in obesity. Most research on cannabinoids has focused on their role in food intake regulation in mammalian species. It is important to determine the role of endocannabinoids in other species. The effect of intracerebroventricular injection of agonists and antagonists of both CB1 and CB2 receptors in 8 to 11 week-old male Single Comb White Leghorn and 3 to 6 weeks old male broilers was investigated. It was found that agonists of both the CB1 and CB2 receptor increased food intake significantly; however, the CB2 receptor agonist had a stronger and longer lasting effect. Antagonists of both receptors decreased food intake significantly. The CB1 receptor antagonist appeared to block both cannabinoid receptors in birds, whereas the CB2 receptor antagonist did not block both receptors. Previous studies have indicated that the CB2 receptor is found only outside the brain and spinal cord, and is involved with the immune system. From the present results, it appears that both cannabinoid receptors are present in the chicken brain. Furthermore, the CB2 receptor may also be localize in the chicken brain. There are also differences in cannabinoid system between Leghorn and broilers. / Master of Science

Growth, reproduction, and immunocompetence were measured in lines of chickens maintained under different feeding regimens. Populations included a commercial broiler breeder parent line segregating at a sex-linked feathering locus (K, k⁺) and 4 experimental lines of which 2 had undergone 32 generations of divergent selection for 56-day body weight and 2 were their sublines in which selection has been relaxed for 5 generations. Mild feed restriction of the broiler line from 7 to 27 days of age reduced carcass fat and heterophil:lymphocyte ratios, and increased immune organ weight, antibody titer to sheep red blood cell (SRBC) antigen and livability than ad libitum fed birds. Body weights were similar by 56 days of age, and there was sexual dimorphism for rate of accelerated growth. Long term obesity, but not short term weight gain, was detrimental to reproductive performance, feed utilization, response to SRBC, and resistance to Escherichia coli, lymphoid leukosis and livability of broiler breeder dams. Poorer quality crumbles also reduced reproductive performance. An association between an endogenous viral gene encoding for avian leukosis virus (ev21) and the sex-linked K allele of the Z chromosome was confirmed in the broiler genome. Reproductive performance and feed utilization were inferior for K/- than k⁺/-, notwithstanding a pleiotropic effect of K associated with heavier egg and embryo weights. Variation in residual feed consumption was influenced by feathering genotypes and management practices. Increases in hatchability for the initial period after onset of lay were due to a reduction in early embryo deaths. Egg and 18-day embryo weights, ratios of embryo:egg and yolk:albumen, and proficiency of lipid transfer also increased but the latter was not associated with higher hatchability. Selection for 56-day body weight resulted in a divergence between lines at 21 days of age of 404% for body weight, 279% for feed intake and 138% for feed conversion ratio. Genotype by feeding regimen interactions were observed for growth and appetite development. Early posthatch growth of small intestine was highly correlated with subsequent growth of demand organs. Selection had also resulted in correlated changes in cell size of muscles, but not liver or small intestine which increased in size due to cell hyperplasia. Correlated changes in feed intake mediated synthesis and secretion of digestive enzymes. / Ph. D.