The effects of varying dosages of 25-hydroxycholecalciferol [25(OH)D3] in commercial diluent injected into the amnion of developing broiler embryos were investigated in a preliminary trial and 2 consecutive main trials. Evaluation of the results of the preliminary trial showed that the in ovo injection of 0.60 micrograms of 25(OH)D3 is capable of increasing its subsequent levels by approximately 3 fold in the circulation of broiler embryos on 19.5 days of incubation. Similarly, results of the 2 main trials showed that the in ovo injection of 0.60 micrograms of 25(OH)D3 significantly improved hatchability on day 21 of incubation and the subsequent performance and bone characteristics of broilers through 28 days of post-hatch age. In conclusion, it is suggested that the in ovo injection of 25(OH)D3 at a 0.60 micrograms dose may be used to effectively improve hatchability, and the performance and bone characteristics of Ross ~ Ross 708 broilers.

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.