Growing consumer awareness about animal welfare has led to the assessment of the impact of common farming practices, such as physical castration, on animal well-being under production conditions. Physical castration is used in livestock industries to prevent indiscriminate breeding, control aggression, and improve meat and carcass quality. In terms of animal welfare, physical castration causes pain, decreased growth performance, infection, and mortality. An alternative approach to castration is thus warranted that will ensure optimal growth without compromising the castrated animal's wellbeing. Immunocastration has proved to be an effective method of suppressing the development and functioning of the reproductive system in various domesticated and wildlife species. The effect of immunocastration on production performance is welldocumented for both swine and cattle. Although ram lambs used for meat production are often physically castrated, information regarding the potential application of immunocastration in sheep is limited. However, immunocastration may potentially improve the welfare, performance, and meat quality of ram lambs used in commercial meat production systems. The purpose of this review is to compare the application and the effects of immunocastration on male livestock to highlight and motivate the need for further research into its use on ram lambs.

Ostrich chick mortality was studied in 2522 chicks that were hatched artificially during the 1999/2000 breeding season. High levels of mortality were observed, with 1978 (78.4 %) of these chicks dying before 90 days after hatching. Atotal of 46.7 %(1177) of these chicks died before 28 days of age, and a further 30.7 %(801) died between 28 and 90 days post-hatching. Chick mortality to 28 days of age could not be conclusively related to sex, day of external pipping or breeder diet. Mortality rates were higher (P < 0.05) at the beginning and end of the breeding season than in the middle months. Differences in mortality levels of chicks incubated in different incubators could be related to the time of the breeding season during which the incubator was mostly used. The regression of chick mortality to 28 days of age on day-old chick mass followed a 2nd-degree polynomial. Chicks with day-old masses below 762.5 g were particularly at risk of dying before 28 days after hatching. Chicks hatching from eggs where excessive water loss to 35 days of incubation (>18 %) was recorded were also at risk of succumbing before 28 days of age. Chick mortality percentages for the period from 28 to 90 days of age exceeded 80 %in chicks weighing an average of 1050 g at 28 days. Mortaliy percentages declined sharply at higher live masses, to between 20 and 30 % in chicks weighing ?1950 g. This 'core' level of mortality remained throughout, even in the heaviest chicks. It was concluded that the high levels of chick mortality could be related to stress in chicks, resulting from an inability to adapt to the rearing environment. The high subsequent mortality percentages of low live mass chicks that survived to 28 days after hatching could probably be attributed to residual setbacks suffered earlier. Abetter understanding of the underlying principles involved in ostrich chick mortality in intensive rearing environments is required for progress in this field, resulting in more predictable survival rates under these conditions.

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Estimates of genetic parameters for reproductive traits, live weight and body measurements were obtained using data from a pair-mated ostrich flock at Oudtshoorn in South Africa. Reproductive traits included total egg and chick production, along with hatchability percentage. Live weight, chest circumference and tail circumferences were recorded at the commencement and cessation of breeding. Heritability estimates (h(2)) were 0.23 for egg production, 0.20 for chick production, 0.10 for hatchability, 0.20 to 0.34 for live weight, 0.12 for chest circumference and 0.30 to 0.38 for tail circumference. Female permanent environmental effects (c(2)) amounted to 0.18 for egg production, 0.18 for chick production, 0.21 for hatchability, 0.32 to 0.36 for live weight and 0.23 to 0.32 for chest circumference. Service sire exerted significant effects only on hatchability (0.22) and subsequently chick production (0.09). Genetic correlations of reproductive traits with live weight were low to moderate, variable in sign, and did not differ significantly from zero. Correlations between live weight recorded at the beginning and end of the breeding season were unity for additive genetic and permanent environmental effects. Egg and chick production were highly correlated genetically and phenotypically, with the genetic correlation exceeding the theoretical limit. In unconstrained analyses, hatchability was positively related to chick production, including at the service sire level. Selection gains in the current flock and future generations are likely. No significant adverse relationships were found between live weight, body measurements and reproductive traits.