The main objective of the study was to determine how phase feeding manipulation affects growth performance, feed cost, carcass characteristics and quality of meat from broiler chickens. A total of 180 day old un-sexed broiler chicks (Cobb 500) were separated into 3 dietary treatments of 60 birds per treatment and each treatment was replicated 3 times with 20 birds per replicate. The dietary treatments were as follows: T1 (starter 1-7 days; grower 8-21 days; finisher 22-35 days), T2 (starter 1-14 days; grower 15-21 days, finisher 22-35 days) and T3 (starter 1-14 days; grower 15-28 days; finisher 29-35 days). Feed intake and body weight gains were recorded weekly in kilograms. Average daily gain and feed conversion ratio were computed weekly. At day 35, the chickens were slaughtered and 12 representative breast muscles from each treatment were used for the determination of muscle pH (pH1, pH24 and pH48) and colour coordinates (Lightness – L*, redness – a* and yellowness – b*) in triplicate at 1 hour, 24 hours and 48 hours post-mortem.Feed intake (FI), feed conversion ratio (FCR), average daily gain (ADG) and average body weight at slaughter (ABW) were not significant (P>0.05) amongst the treatments. The most cost efficient feed (which accumulated the cheapest cost feed per kg were) T1 (R11.32) and T3 (R11.32) although there was a slight difference in the gross profit of these treatments T1 (R45.71) and T3 (R44.48). Carcass characteristics were the same (P > 0.05) across the treatments except for the wing, thigh, drumstick and the breast (P < 0.05). T2 had the highest wing weight (166.63±8.60), T1 (113.03±8.60) and the lowest in T3 (74.46±8.60). The thigh weight were greater (P<0.05) in T2 (185.69±4.34); T1 (185.54±4.34) compared to T3 (166.97±4.34) which was lower. Treatments 1 (204.17±6.57), T2 (197±6.57) had heavier (P<0.05) breast weights than T3 (186.06±6.57). Dietary treatments had no significant effect (P > 0.05) on pH of the breast meat. No differences were observed in colour during the 1 hour period after slaughter. At 24 hours after slaughter, the L* values were different (P < 0.05) in T1 and T2 (44.3 ± 0.37; 43.7 ± 0.37), respectively, T1 and T3 were the same. The a*-values were different (P < 0.05) at 48 hours after slaughter for T1 and T3 (4.5 ± 0.27; 3.4 ± 0.27), T2 was the same as T1. It was therefore, concluded that since manipulation of starter phase did not have adverse effects on growth performance, gross profit, slight statistical difference in meat quality attributes and carcass characteristics. Therefore, the manipulation of starter diet has the potential to be used in broiler production.

Effects of feeding Moringa oleifera leaf meal as an additive on growth performance of chicken, physico- chemical shelf-life indicators, fatty acids profiles and lipid oxidation of broiler meat The main objective of the study was to determine the effect of M.oleifera leaf meal (MOLM) as an additive on growth performance, carcass characteristics, physico-chemical shelf-life indicators (colour, ultimate pH, driploss), fatty acids profiles and lipid oxidation of meat from broilers. A total of 432 1day old unsexed broiler chicks (Aviane 48) were randomly allocated to four dietary treatments (TRTS) in 72 cages. There were 18 cages per treatment and each cage allocated 6 chicks. Water and feed was provided at ad libitum. The feeding phases were, prestarter (0-7 Days), starter (8-18 Days), grower (19-28 Days), finisher (29-35 Days). The four TRTS contained graded levels of MOLM at 1000g/ton, 750g/ton, 500g/ton, and 0g/ton (control), respectively. The birds were slaughtered at 35 days of age. Breast muscles were sampled for meat, ultimate pH (pHu ), colour, drip loss over a 7 days shelf-life test. After each day’s test sub-samples were dipped in liquid nitrogen and kept at -180 C for thiobarbituric acid reactive substances determination. On Day1 and Day 7 extra sub-samples were also kept at -180 C for fatty acids analysis.The TRTS had no effect on average feed intake (AFI), feed conversion efficiency (FCE), and on average daily gain (ADG). Slaughter weight (SW), carcass weight (CW), dressing percentage and gizzard weight (GW) values were similar in all TRTS. Liver weight (LW), heart weight (HW), and gastro-intestinal fat (GIF) differed in all the TRTS, with treatment 2 having the highest value of HW (28.3±2.55), and LW (44.2±1.60) was the highest on treatment 4 . The pH values in all TRTS were constant from Day1 to Day5, reached peak on Day6, and then declined on Day7. Meat from broilers given treatment 1 with MOLM (1000g/ton) had the highest lightness (L*) values. The redness (a*) values were the highest in meat from treatment 2 (750g/ton MOLM). Treatments had no effect on yellowness (b*) values and on drip loss of the breasts. During storage L* values were high from Day1 to Day5 and decreased from Day6 to Day7. Drip loss increased with storage time as expected. Treatment 4 (control) had the highest proportions of poly-unsaturated fatty acids (PUFA) (30.3±1.87). Treatment 1 (1000g/ton) had the highest proportion of saturated fatty acids (SFA) (60.9±1.87). Treatment 1 (1000g/ton) had the highest proportion of SFA (60.9±4.30). Treatment 2 (750g/ton) had the highest n-6/n-3 ratio than other TRTS. Days had no effect (P>0.05) on PUFA, SFA, and n-6/n-3 ratio. Treatment 1 had a highest amount of malondialdehyde (MDA), treatment 4 had no effect (P>0.05) on MDA . Storage time had an effect (P<0.05) on MDA levels, except for on Day1 and Day7. Day2 had the highest amount of MDA (0.7±0.08). The use of MOLM as an additive in broiler diets reduced lipid oxidation in meat, and maintained the quality of the broiler meat during storage. It also did not have any adverse effects on the growth performance of broilers. Therefore, it has the potential to be used as an additive in broiler diets.

Calcium status is a major factor in the regulation of reproductive activity in the hen. Restriction of dietary calcium (Ca) or vitamin D (D) is assumed to cause cessation of ovulation through decreased plasma calcium concentrations. Several studies suggest that there may be a threshold level of ionized calcium (Cai) below which ovulation will not proceed. The objectives of this thesis were to determine how Cai concentration is involved in the process of ovulation by comparing Ca and D-deficient hens, that had ceased laying, with control birds that were laying normally. A secondary objective was to determine the effects of multiple blood sampling (MBS) on the hen's ovulatory cycle. SCWL hens were divided into three groups-control, Ca-deficient and D-deficient groups and fed respective diets. Control birds were serially sampled every two hrs for 24-26 hrs immediately after oviposition until the next oviposition. Deficient birds, that had ceased laying for 10 to 14 days, were sampled at the same time. MBS was achieved with an indwelling vascular access port. Six birds/experimental group were used. Control birds were bled two weeks later from late afternoon until the following day at the same time. Whole blood was analyzed for Cai. Separated plasma was analyzed for total calcium (Cat), inorganic phosphorus (Pi), estrogen (E₂), progesterone (P₄) and l,25(OH)₂D₃ concentrations. Tibiae were ashed for mineral content. In expt. 1, the effect of MBS on the ovulatory pattern of hormones and ions was observed by sampling control birds twice, using two different time courses. Patterns and concentrations of the hormones and ions, regardless of time course, were similar to previous studies. Overall treatment effects were only significant between treatments with regards to total calcium and estradiol concentrations. The large loss of plasma proteins during the bleeding regime resulted in a steady decline in Cat over the 26 hrs, however, it was still within the physiological range of laying birds. . E₂ concentrations were also affected due to interruption of the laying sequence. However, this can be avoided since some birds continued to lay. In expt. 2, the control group had significantly higher mean plasma Cat and Pi concentrations and bone ash than both the deficient groups. Control and D-deficient groups had similar mean Cai concentrations, however, the ovulatory profile of the control group had a significant cyclic pattern over the 24-26 hrs, whereas, both deficient groups did not vary significantly over the 24 hrs. Plasma Pi concentration in the control group, not previously described, was cyclic in nature, related to the egg laying cycle. Plasma l,25(OH)₂D₃ concentrations were significantly higher in the Ca-deficient group than the control group. D-deficient birds had detectable levels of plasma 1,25(OH)₂D₃, but it was significantly lower than the control group. Plasma E₂ and P₄ concentrations were significantly higher in the control group In conclusion, it would appear that an inter-relationship exists among Cai, Pi and 1,25(0H)₂D₃ and the reproductive hormones. A threshold concentration of Cai may be the trigger for ovulation, perceived at the level of the pituitary, hypothalamus or ovary. A threshold of Pi and a window of l,25(OH)₂D₃ concentration may also have permissive roles in ovulation. In addition, MBS, regardless of time course, can be used as a method for determining ovulatory profiles in individual birds without seriously affecting ionic and hormonal concentrations and patterns. / Land and Food Systems, Faculty of / Graduate

Hypomelanosis, a severe reduction in pigmentation, is a widespread phenomenon which affects many different vertebrate species, including humans and chickens. The cause(s) of various forms of hypomelanosis is (are) not known. The aim of this study was to determine the cause of hypomelanosis in a breed of white chickens (White Plymouth Rock x Pile Game). It was hoped that this hypomelanotic breed may provide insight into the etiopathogenesis of certain human hypomelanotic disorders, such as vitiligo and albinism. To determine whether melanocytes are present in the hypomelanotic skin, two melanocyte-specific assays were carried out, in situ DOPA histochemistry and a sensitive radiometric assay for tyrosinase. The results show that active tyrosinase was present in 8, 9 and 10 day skins. However, unlike normal black skin, the level of tyrosinase did not increase with age, suggesting that the melanocytes either die or that they do not continue to synthesise tyrosinase. Ultrastructurally, these melanocytes appeared to be morphologically normal and they did not show signs of premature degeneration. Unlike black chick melanocytes, however, they contained very few premelanosomes and fully melanised melanosomes were never observed, suggesting that hypomelanosis results from the arrested development (melanisation) of melanosomes in vivo. Two different experiments were carried out to determine whether this blockage in melanogenesis is intrinsic in the melanocyte or whether it is caused by extrinsic environmental factors. The outcome of these studies were conflicting: 1) In culture, white chick neural crest cells produced pigment, suggesting that the melanocyte is not defective. However, ultrastructural examination of these cultured melanocytes showed that they contained a large proportion of partially melanised melanosomes. 2) Black chick neural crest cells migrated into white skin explants and contributed towards pigment in the developing feathers, suggesting that the white chick tissue environment is also not defective. The results hint that hypomelanosis in the white chicks is caused by the interaction of at least two genetic defects: an intrinsic mutation of the melanocyte, as well as an extrinsic mutation in the melanocyte environment that, in combination, exert an inhibitory influence on melanin synthesis. This study shows that, in situ, white chick melanocytes share some features with ty-pos albino melanocytes and may be representative of this pigmentary disorder. White Plymouth Rock x Pile Game chicks may also be useful as a model for the multi-faceted disorder, vitiligo.

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No description available.

Since the removal of in feed antibiotics in the past few years commercial poultry production is especially sensitive to the health of the small intestine. Healthy small intestines balance nutrient absorption and defensive barrier functions to ensure the chicken is able to meet the whole-body nutritional needs and is able to help prevent internalization of pathogens or potentially toxic components. This balance can only be maintained under stable conditions. When a disturbance event occurs the intestine imbalances until a new, and less efficient, balance can be achieved. The objective of this dissertation is to propose a novel model to understanding intestinal homeostasis in the face of various disturbance events. Chapter 2 investigated the effects of Runting Stunting Syndrome on broiler chickens in four different groups of chicks displaying clinical symptoms. The major finding in this study was that in two of the four groups the expression of stem cell gene Olfactomedin 4 was absent from the crypt though other functional genes were found to still be expressed there. Chapter 3 characterized intestinal gene expression following a single challenge of Eimeria acervulina in broiler chickens. During Eimeria infection gene expression of multiple host defense peptide genes were decreased compared to uninfected chickens. Further, Eimeria infected chickens increased cell proliferation within the crypt and post-peak infection showed signs of intestinal recovery. Additionally, chapter 3 developed a novel method for visualizing Eimeria as it infects the intestine. In chapters 4 and 5 cell type population changes during the peri-hatch intestinal maturation process were evaluated. Peri-hatch intestinal maturation is critical for the successful transition from embryonic to post-hatch life. Chapter 4 profiled changes in proliferative cells and gene expression of various stem cell marker genes during the peri-hatch period: the last three days of embryogenesis and the first week post-hatch. The stem cell marker gene Leucine Rich Repeat Containing G Protein-Coupled Receptor 5 (Lgr5) decreased during the post-hatch period while Olfactomedin 4 increased post-hatch. Both stem cell genes were expressed within the intestinal crypt, though prior to hatch Lgr5 was expressed in the lamina propria and villi as well. Additionally, the marker of proliferation Ki67 gene was expressed in cells throughout the intestine prior to hatch but became restricted to the crypts and along the center of the villi. Chapter 5 assessed the effect of providing probiotics to late term embryos via in ovo feeding (IOF). The effects of IOF were primarily observed on embryonic day 20 (e20), roughly 48 hours after IOF. On e20 the embryos in ovo fed probiotics in saline had increased expression in the ileum of Peptide Transporter 1 (PepT1) a marker gene for enterocytes and Mucin-2 (Muc2) a marker gene for goblet cells compared to non-injected control embryos. Also, on e20 the embryos in ovo fed saline only had numerically increased PepT1 and Muc2 compared to non-injected control embryos. The difference in responses between the probiotic and saline fed embryos on e20 suggests different routes of stimulation. These investigations illustrate various possible scenarios and means of investigating intestinal homeostasis during disturbance events. / Doctor of Philosophy / In healthy birds, the small intestine absorbs nutrients while preventing the free passage of microbes or toxic chemicals into the body. The two functions: absorption and barrier exclusion seem contradictory, but a balance is struck to ensure both functions continue. This balance-point, homeostasis, persists until an event disturbs it. Once disturbed the balance-point is changed and the intestine is unable to maintain both functions, until a new balance is found following recovery. The objective of the dissertation is to better understand intestinal homeostasis, through four different research projects. Experiment 1 characterized the intestinal cell population changes in broiler chickens during Runting Stunting Syndrome, a viral infection. The major finding of this chapter was that a stem cell gene, that is normally robustly expressed was not expressed in some groups of infected chicks but not all. Experiment 2 investigated the intestinal response of broiler chickens to Eimeria acervulina, an intestinal parasitic infection. Eimeria, which infects intestinal enterocytes, caused a decrease in defensive genes during the peak of infection. Then after the peak the intestine began to recover, as indicated by increased cell proliferation. Experiment 3 profiled changes in the expression patterns of stem cell and proliferation genes in the small intestine during the last days before hatch and the first week post-hatch. Pre-hatch stem and proliferative gene expression occurred in the crypt and villus, but became restricted to the crypt early during the post-hatch period. Experiment 4 assessed the effect of feeding probiotics to embryos before hatching on intestinal gene expression. Embryos fed probiotics had increased Mucin-2 and Peptide Transporter 1 gene expression in the last segment of the intestine, the ileum compared to non-fed embryos 48 hours after feeding. Additionally, treatments fed saline also showed increased gene expression, though to a lesser extent. Together these projects illustrate various disturbances to intestinal homeostasis and how intestinal cells change and respond during the disturbance and recovery periods.

Purpose of this study was to (1) compare egg production of dubbed and non-dubbed females, (2) determine the social relationships between and among dubbed and non-dubbed females in large and small flocks maintained under various housing conditions, and (3) determined egg quality, sexual maturity, mortality, body weight and other traits of economic importance in dubbed and non-dubbed chickens. The studio involved two large flocks, each consisting of 170 Leghorn-type hybrid females and eight small flocks each composed of six White Rock females. In all flocks, the combs and wattles were removed from half of the birds. One of the large flocks was housed in a conventional type house while the other was housed in a modified solar house. The results obtained on birds in the large flocks indicate that there were no significant differences between comb treatment for any of the following traits: age of the first egg, age at 50 percent production, fall and spring egg weight, Haugh units, specific gravity, yolk mottling, blood and meat spots, body weight at 72 weeks of age, liveability and fertility. Differences between comb treatments for percentage egg production to 72 weeks of age were also not significant on a yearly basis; however, a significant comb treatment x month interaction was found. The dubbed birds laid at a higher rate during the colder months, while during the warmer months the undubbed females were superior in egg production. A definite effect from dubbing was observed in the social behavior in both the large and small flocks. In both types of flocks, the dubbed birds were subordinate to non-dubbed ones. Chickens maintained in the conventional type house reached sexual maturity significantly later and weighed significantly less than those in the modified solar house. The moisture content of the litter in the former house was significantly higher than that in the latter house during the colder months of the year. Differences between houses for other traits measured were not significant. / M.S.

The concentration of reduced blood glutathione, feed efficiency, oxygen consumption, and growth were studied in two lines of chickens that had undergone divergent selection for body weight at eight weeks of age. The latter three traits were studied in two light environments, continuous illumination and a ratio of 8 hours light to 16 hours darkness. The dissertation involved two experiments and chickens from the S₁₁, S₁₂, and S₁₃ generations of the high and low weight lines. Blood glutathione, body weight, and percentage packed cell volume were measured in S₁₁ generation males at 1, 4, 7, 10, 13, 16, 19, 28, 56, 112, and 168 days of age. Males from the high weight line were heavier at all ages and had a higher packed cell volume at 28 days of age and thereafter than those from the low weight line. Blood glutathione was consistently greater in the high line than in the low line with the largest differences between lines occurring at the younger ages. The influence of light environments on growth, feed efficiency, and oxygen consumption was studied in two trials utilizing chicks from the S₁₁ and S₁₂ generations. Body weights and feed efficiencies were measured at 14, 28, 42, and 56 days of age and oxygen consumption at 28 and 56 days of age. Chicks from the high weight line were heavier at all ages and they had consistently superior feed efficiencies and lower rates of oxygen consumption than those from the low line. Chicks maintained under continuous illumination were heavier and had superior feed efficiencies than those reared in restricted light. Oxygen consumption of chicks reared in restricted light was greater than that for those under continuous light when the measurements were obtained during the day i.e. the time of their photoperiod. No differences were observed between light environments when determinations were made in the evening, showing a diurnal rhythm between the day and evening measurements. To obtain more information on the metabolism of these lines, oxygen consumption was measured at 28, 42, and 56 days of age on a sample of S₁₃ generation males. The results agreed with those obtained in the S₁₂ generation in that oxygen consumption was lower for males from the high weight line than for those from the low weight line. The primary conclusions from these experiments are that divergent selection for high and low body weight results in correlated responses of blood GSH, feed utilization, and metabolic rates. Further, although different light environments may result in varying responses in feed utilization and metabolic rates, line x light environments interactions were not important for traits other than body weight. / Ph. D.

This study was conducted to determine the effect of egg weight on hatchability and chick hatch-weight of Cobb 500 broiler chickens. A total of 396 Cobb 500 hatchable eggs classified according to three different egg weight groups as small: (<49 g) medium: (50-59 g) and large: (60-69 g) were used in the experiment. A complete randomized design of three treatments with three replicates and each replicate having” 44 eggs was used for the experiment. Simultaneously a linear type equation was used to determine the relationship between egg size and responses in hatchability values and chick hatch-weight. Results indicated that large-sized eggs produced chicks with higher (P<0.05) hatch-weight than medium and small-sized eggs. However, no differences were detected with fertility rate percentage, hatchability percentage and percentage hatch of fertile. It was therefore concluded from the result of the present study that sorting of Cobb 500 broiler chicken breeder eggs by weight prior to incubation might be advantageous in producing uniform size Cobb 500 broiler chicken hatchlings to meet specific market demands with improved efficiency. / Agriculture and  Animal Health / M. Sc. (Agriculture)