Effect of surgical sterilisation on body composition of male and female emus (Dromaius novaehollandiae)

Abstract

Animal Production in Australia 1998 Vol. 22 EFFECT OF SURGICAL STERILISATION ON BODY COMPOSITION OF MALE AND FEMALE EMUS (Dromaius novaehollandiae) K.M. WILLIAMSA, P.J. SHARPB and G.B. MARTIN A B A Faculty of Agriculture, The University of Western Australia, Nedlands, WA 6907 Roslin Institute, Midlothian, EH259PS, UK Emus are farmed for their meat, leather from skin, and oil production from fat. The birds do not reach slaughter size until at least twelve months of age and, in some circumstances, are grown until they become sexually mature. This is associated with aggressive behaviour during the breeding season which is during the autumn and winter months, with consequent damage to the skins, and a loss of appetite which causes a loss of fat. To manage the behavioural problems, sterilisation of the birds to prevent sexual maturation was considered. In addition, such treatment might lead to deposition of extra fat, as has been shown for migratory quail (Boswell et al. 1993). Therefore a comparison was made of the body composition of surgically sterilised male and female emus. In November 1996, 17 female and 22 male emus were slaughtered. Of these, six females and seven males had been surgically sterilised at eight weeks of age, leaving eleven females and fifteen males as sham-operated, gonad-intact controls. At slaughter, birds were two years and two months old and had been raised by Dromaius Australia Ltd under standard commercial practices on their farm at Mount Gibson, WA. The live weight of the birds directly before slaughter was recorded. After they were killed, the head was removed, as were the feathers and the legs below the hock joint. The skin was then removed and the subcutaneous fat was collected. After all of the internal organs were removed, the carcase was weighed to give a total weight of skeleton plus muscles. From the internal organs, the gonads (two testes or one ovary) were dissected and weighed, and the abdominal fat was removed and added to the subcutaneous fat to give a total fat weight. The following day, the muscles were removed from the skeleton and weighed. The statistical analysis was by ANOVA. Table 1. Comparison of body composition of male and female emus Sex (kg) Female controls Female surgery s.e.d. Significance Male controls Male surgery s.e.d. Significance All females All males s.e.d Significance Number (kg) 11 6 Liveweight (kg) 44.68 46.00 1.191 0.50 39.97 39.64 1.885 0.865 45.15 39.86 1.282 < 0.001 Carcase (kg) 21.35 21.48 1.073 0.899 20.07 19.71 0.882 0.688 21.39 19.96 0.649 0.034 Fat (g) 8.96 10.60 1.022 0.131 7.55 7.80 0.951 0.797 9.54 7.63 0.662 0.007 Meat 13.90 14.18 0.576 0.624 13.38 13.23 0.561 0.794 14.00 13.33 0.383 0.090 Gonad 19.70 3.40 3.94 < 0.001 7.02 0.00 0.991 < 0.001 13.94 4.79 1.725 < 0.001 15 7 17 22 s.e.d. is the standard error of the difference of the means In the castrated males, the testes were removed completely at surgery. In the sterilised females it was difficult to remove all of the ovarian tissue, but there was a significant reduction in gonadal weight. Sterilisation had no effect on any other body characteristic measured. The data were therefore pooled to allow comparison between the sexes. The females were heavier and had larger carcases and more fat than the males. In conclusion, female emus produce more fat than males, but sterilisation of either sex does not appear to alter production of meat or oil. BOSWELL, T., HALL, M.R. and GOLDSMITH, A.R. (1993). J. Zool. 231, 627-644. 335