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

The use of antibiotics as growth promotors in the food animal industry has led to the generation of antibiotic resistant microorganisms, which are a major health risk to humans. Therefore, bans and limitations, including the FDA’s veterinary feed directive, have been placed on the use of antibiotics as growth promotors, and there has been a push to find an adequate alternative. In the laying hen, probiotics and/or prebiotics have shown promise as they help promote the colonization of beneficial bacteria in the GI tract of the host, increase feed efficiency, increase egg production, and provide protection against pathogenic bacteria. In this feeding trial, Leghorn HyLine W36 hens were fed diets supplemented with either 0.05% IMW50(prebiotic), 0.05% CALSPORIN (probiotic), 0.05% IMW50 and 0.05% CALSPORIN, or a control diet with no prebiotic or probiotic additive. The birds were maintained on this diet from 1 day to 66 weeks of age, over which time feed intake and egg production was measured. From 37 to 65 weeks of age, every 3-5 weeks, egg quality was evaluated through specific gravity, egg weight, albumen height, and eggshell breaking force measurements. At 6, 16, 32, and 64 weeks of age, the microbiota population in the ileal digesta was evaluated using T-RFLP analysis methods. Then at 64 weeks of age, splenic IFN-γ, IL-6, IL-10, and IL-12 expression was measured by RT-qPCR. Unexpectedly, fluctuations in feed disappearance were observed, potentially linked to factors such as changes in diet type, temperature variations, feed wastage, or a technical error. Birds on CALSPORIN-containing diets showed resilience and maintained egg production during a decline in feed disappearance, suggesting enhanced capabilities in digesting larger particle sizes. However, there were trade-offs, as egg quality parameters slightly decreased in supplemented diets. CALSPORIN alone showed a promising effect on survival probability. Microbial diversity in the ileum increased with CALSPORIN, but the IMW50 alone led dysbiosis, possibly impacting infection resistance. Additionally, the combined supplementation of IMW50 and CALSPORIN may have introduced a disruption in immunological homeostasis.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Day old Dekalb XL-link pullets were randomly assigned to eight dietary treatments of 100 birds each. The percent crude protein (CP) with the respective weeks fed in parentheses for each treatment (T) was as follows: T1. control 18(0-6), 15(6-14) and 12(14-20); T2. 18(0-1), 12(1-8), 15(8-14) and 18(14-20); T3. 18(0-1), 12(1-10), 15(10-16) and 18(16-20); T4. 18(0-1), 12(1-12), 15(12-16) and 18(16-20); T5. 16(0-1), 12(1-10), 15(10-16) and 18 ( 16- 20 ); T6 . 16 ( 0-1 ) , 12 ( 1-12 ) , 15 ( 12 -16 ) and 18 ( 16- 2 0); T7. 20(0-1), 12(1-10), 15(10-16) and 18(16-20); and T8. 20(0-1), 12(1-12), 15(12-16) and 18(16-20). All diets were fed ad lib. The control pullets were heavier for most of the 20-week growing period. Skeletal growth was highly correlated with body weight, however body size was not different at 20 weeks. Cumulative feed intake of the control fed birds was significantly greater than five of the reverse protein fed birds. Feed conversion and protein intake suggested a potential economic advantage in reverse protein feeding. At 20 weeks of age, 576 pullets were transferred to laying cages and fed a common diet. No differences in body weight were seen at 28 weeks of age. Livability was not affected by dietary treatment. Hen-day and hen-housed figures showed significant treatment effects during the first 28-day period only. No significant differences were seen in egg weight, % egg size, egg mass, egg specific gravity, shell deformation, Haugh units or any feed trait. Reverse protein feeding appeared to offer promise as a method of restricting growth in egg-type pullets. The significance of effects on egg production traits may have been masked by small sample size. / M.S.

<p>Early life stress is something that animals used in production often have to experience. What we do not know is if there are any consequences of this treatment later on in life. Zebra finches postnatal treated with the stress hormone corticosterone showed an exaggerated and prolonged stress response later on. To examine the effects of early life stress 77 White Leghorn chicks were used, half of them was stressed from postnatal day 1-14 and then tested between 47-63 days of age. The tonic immobility (TI) test is a commonly used test to evaluate the fearfulness and stress reaction in fowl. The chicks were placed on their back in a V-shaped wooden cradle and TI was induced by applying light pressure on the breast and neck. The number of inductions required to induce TI was recorded as well as the time until the first alert head movement and the total duration of the TI. The birds were tested in a calm environment but also after a stressful situation. There were no differences in the total duration of the TI reactions. However, stressed animals tended to need more induction attempts than the control animals. While looking at the time elapsed until the first head movement stressed chicks had a significantly lower duration. This indicates a dullness or shift in the stress response of the treated birds and there seem to be a more exaggerated response in the males.</p>

Early life stress is something that animals used in production often have to experience. What we do not know is if there are any consequences of this treatment later on in life. Zebra finches postnatal treated with the stress hormone corticosterone showed an exaggerated and prolonged stress response later on. To examine the effects of early life stress 77 White Leghorn chicks were used, half of them was stressed from postnatal day 1-14 and then tested between 47-63 days of age. The tonic immobility (TI) test is a commonly used test to evaluate the fearfulness and stress reaction in fowl. The chicks were placed on their back in a V-shaped wooden cradle and TI was induced by applying light pressure on the breast and neck. The number of inductions required to induce TI was recorded as well as the time until the first alert head movement and the total duration of the TI. The birds were tested in a calm environment but also after a stressful situation. There were no differences in the total duration of the TI reactions. However, stressed animals tended to need more induction attempts than the control animals. While looking at the time elapsed until the first head movement stressed chicks had a significantly lower duration. This indicates a dullness or shift in the stress response of the treated birds and there seem to be a more exaggerated response in the males.

Social support is thought to give animals benefits from social partners, such as improved coping with challenges. The aim of this study was to investigate differences in social support in the red junglefowl (RJF) and a domestic layer strain, the White Leghorn (WL). A runway test consisting of two compartments with unfamiliar and familiar stimulus animals was used to measure social motivation before and after a stressful experience. Total number of test animals was 56 divided into four groups; male and female WL as well as male and female RJF. Results showed that females preferred to stay close to familiar conspecifics after stress treatment. Before stress treatment there was little difference between either sex of WL while RJF males and females chose different zones. Females preferred familiar conspecifics, indicating that they rely more on familiar social stimuli for social support. Males of the two breeds behaved differently towards stimulus animals. WL males showed aggression towards familiar stimulus animals while RJF males directed aggression towards unfamiliar stimulus animals. Indication of sexual behavioural dimorphism was supported while further research is needed in domestication effects on social support in chickens.

When animals are stressed they use a trait called social support to alleviate their stress responses. With domestication many traits from the ancestor red junglefowl have changed in the domesticated breed white leghorn. White leghorns are bred to be able to live in large groups where it becomes hard to recognize every chicken. They are therefore not as dependent of familiar stimuli birds for social support as red junglefowl. Our hypotheses were that red jungle males would be more interested in unfamiliar stimuli birds than white leghorn male before stress due to their territoriality. We tested total 56 chickens in an open field test. The test arena was divided in three zones and the time the focal birds spent in each zone was recorded. The focal bird was recorded in 300 seconds before being stressed by being suspended in a net and then recorded again in 300 seconds. The results showed that social support and social behaviour differs between females and males for both breeds. No significant differences were found between the breeds. There was a tendency for significant of breed (P=0.08) effects in the central zone unstressed. The two interactions before stressed between breed and sex, central zone (P&lt;0.01) and unfamiliar zone (P&lt;0.01) had significant effects. We observed fights between white leghorn males and familiar stimuli. Waltzing did also occur in red jungle males in front of unfamiliar. In conclusion, numeric differences can be seen but not large enough to be significant and our hypotheses are not confirmed.

Domestication has taken place over thousands of years and during that time we have bred animals on different traits. The red jungle fowl is the ancestor to all domesticated chicks, including the white leghorn which is used in egg production. The domestication of the red jungle fowl has resulted in behavioral changes between itself and domesticated breeds, such as white leghorn. In this study we examine how these two breeds handle stress and whether or not they use social support when coping and recovering from a stress experience. The study took place in a built arena with two stimuli animals on each side. There the animal was studied for 5 minutes, stressed for 3 minutes and studied again for 5 minutes. We found that the red jungle fowl males spent more time in the unfamiliar zone before stress than males of the white leghorn. Our results also showed that the females of white leghorn and red jungle fowl spent more time in the familiar zone than males after being stressed. This is an indication that they are more dependent on social support from familiar animals after stress than the males are. Aggressive behavior was also observed among the males. Red jungle fowl males acted aggressively towards the unfamiliar stimuli animals and the white leghorn towards the familiar stimuli animals. In conclusion, we found that the females where in greater need of social support than the males. / Biologi

Memoria para optar al Título Profesional de Médico Veterinario / Con el continuo crecimiento de la población mundial, la constante preocupación por el bienestar animal y la apertura de los mercados internacionales, la industria avícola se ha visto en la obligación de reducir sus costos al máximo para así poder entregar un producto lo más económico posible al consumidor, sin descuidar la calidad del mismo. Esta disminución de costos no puede llevarse a cabo a través del aumento en la densidad de las aves por jaula, lo que implica un menor bienestar, ya que la legislación es cada día más exigente al respecto. Es por esto, que se hace indispensable minimizar los costos de producción y uno de ellos son las pérdidas producidas por la ruptura de la cáscara del huevo. El proceso de biomineralización de la cáscara del huevo es realizado por poblaciones celulares especializadas del oviducto, que actúan como una línea de ensamblaje a medida que el huevo avanza a través de éste. Esta biocerámica resulta de la interacción controlada entre una fase orgánica y una inorgánica. Estructuralmente la cáscara del huevo está constituida por cuatro capas, las cuales del interior al exterior son: capa de las membranas de la cáscara, capa mamilar, capa en empalizada, capa cuticular. Durante su formación, la cáscara del huevo es altamente susceptible a ser alterada por diversos factores, entre ellos el estrés. Los factores estresantes son responsables de una serie de defectos en la calidad de la cáscara del huevo que disminuyen su valor comercial e incluso pueden llevar a la perdida total en algunos casos. Desde hace muchos años diversos autores han evaluado la calidad de la cáscara del huevo tomando en consideración diversas características, distintas condiciones ambientales y usando una gran variedad de técnicas tanto directas como indirectas. Para el presente estudio se utilizaron gallinas White Leghorn, las cuales fueron divididas en subgrupos e inyectadas con 1 mg de adrenalina por vía subcutánea a distintas horas post ovipostura para evaluar el efecto del estrés adrenérgico sobre la calidad de la cáscara del huevo. Las características evaluadas fueron resistencia y espesor de la cáscara con y sin membranas, las cuales se compararon mediante una prueba de t de dos colas. Mediante microscopía electrónica de barrido se analizó la ultraestructura de estas cáscaras de huevo. El análisis de los resultados muestra que no existe diferencia estadísticamente significativa entre el grupo tratado y el control, tanto para resistencia a la compresión mecánica como para el espesor de la cáscara con y sin membranas, sin embargo al realizar un estudio ultraestructural de las cáscaras de los huevos de las gallinas que efectivamente respondieron al tratamiento con adrenalina se observaron diversas alteraciones que explicaban su baja resistencia y espesor de cáscara. Esta falta de diferencia significativa podría deberse a la gran variación individual que existe en la respuesta al tratamiento y en el tiempo de recuperación. No obstante lo anterior el análisis ultraestructural mostró que las alteraciones observadas, como presencia de cuerpos A y B, confluencia de mamilas, líneas de fractura, columnas de distinto grosor y tamaño, alteraciones en las membranas de la cáscara, presencia de cristales de calcita entre las columnas, concordaban con el tiempo post ovipostura en que las gallinas eran tratadas y la estructura del huevo que estaba en formación. Niveles de estrés agudo, comparables a los producidos por la administración de adrenalina, se producen al disturbar a las gallinas por incursiones no habituales de personal, aves silvestres u otros animales en los galpones de postura. / Proyecto Fondap 11980002