Thesis (MPhil (Animal Sciences))--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Over the last few decades various authors have reported the influence of day old chick quality on integrated broiler industries. Although various methods of determining chick quality have been reported, defining a good or a first grade day old chick can be problematic as it involves many subjective measurements. Incubation temperature (embryo temperature) is probably the biggest, most influential factor during incubation on chick quality. High temperatures cause the most damage. It leads to poor growth, stress, black buttons, threads, weak chicks, chicks with poorly erupted down that are bleached in appearance, low hatchability, late embryonic death and early broiler mortality. This trial was designed to test whether 37.2, 37.4 or 37.5ºC was the optimum incubation temperature for hatching Hybro G+ chicks with superior quality. The parameters that were measured were the chick length, bodyweight, and the yolk residue of the day old chicks of the flocks set at different setter temperatures. After hatching, 1 440 chicks (480 chicks per temperature treatment) were placed at a broiler facility where the daily mortalities, weekly bodyweight gain and feed conversion were recorded and calculated. The age of the breeder flock had a significant effect on all three parameters measured in the incubation trial with p values of <0.001, <0.001 and 0.005 respectively. There were no significant differences in chick quality parameters due to different incubation temperatures. The age x temperature interaction could be attributed to the large influence of the age of the breeder on egg size and consequently chick parameters. The results could be related to the fact that bigger eggs from older breeder flocks have higher initial egg mass, which will result in heavier embryos and thus converted to a larger day old chick. The performance trial performed after the incubation trial showed no significant effect of the incubation temperature on 7-day and daily mortalities, weekly bodyweight gain and feed conversion efficiency to 42 days of life. The lack of effects observed in these trials could be attributed to the small range of temperatures used in addition to the difficulties brought about the use of multi-stage incubators.

During the 21 day incubation period, the fertile egg provides nutrients such as fatty acids for energy and polyunsaturated fatty acids (PUFA) for membrane synthesis to the developing chick. The hypothesis tested in the present study is that the type of PUFA fed to the breeder hen can alter tissue lipid composition and PUFA metabolism in the progeny during growth. The objective of the present study was to test two different sources of PUFA (n-3 or n-6) on: 1) egg production, egg, and chick quality; and 2) changes in tissue PUFA composition and metabolism in progeny during growth. Fertilized eggs (n=240) were collected from Ross breeder hens (n=45) fed one of the three experimental diets containing 3.5% fish (long chain n-3), flax (18:3 n-3), or safflower oil (18:2 n-6). The egg and yolk weight was lowest for eggs from hens fed fish oil (P=0.09, P=0.02). The chick weight on day of hatch was 41.2, 45.3, and 43.3g, for fish, flax, and safflower, respectively (P=0.003). In the second experiment fertilized eggs were collected from Lohman Brown layer hens (n=75) fed a control, high n-3, or low n-3 diet. Chicks were raised up to day 14 on a control diet lacking long-chain n-6 and n-3 fatty acids. Chick tissue samples (gastrointestinal tract, liver, and blood) were collected on day 1, 7, and 14 and were subjected to fatty acid (FA) and interleukin-6 (IL-6) analysis. The long-chain n-6 to long chain n-3 ratio was lowest in the duodenum, jejunum, ileum, and liver from chicks hatched from fish oil fed hens (P<0.001) up to day 14. Interleukin-6 was lowest in liver (P=0.009) and serum on day of hatch, for fish oil chicks. The results from this study show that the diet fed to breeder hens alters progeny tissue PUFA composition and lipid metabolism during early development in avians. The long term effects of maternal diet manipulation on progeny growth and lipid metabolism need to be investigated in detail. / Graduation date: 2013