Chemical sterilisation as an alternative to spaying of heifers

Summary

​Alternatives to surgical sterilisation of female cattle may help improve animal welfare outcomes. The aim of this study was to investigate if administration of potential chemosterilants by transvaginal, ultrasound guided intraovarian injection offer an alternative to surgical sterilisation. Bos indicus heifers were treated with intraovarian injections of either saline (n = 10), CaCl2 (n = 10), zinc gluconate (ZG; n = 10), or a combination of CaCl2 and ZG (Ca + ZG; n = 10) and then exposed to a bull from 82 to 84 days after treatment.

After treatment total ovarian mass at slaughter was less in heifers treated with CaCL2 compared to the other treatments (P<0.05) but concentrations of haptoglobin, anti-müllerian hormone and total oocyte counts did not differ (p>0.150). Pain responses were observed in heifers treated with ZG and ZG and CaCl2 but not in heifers treated with saline or CaCl2. Complete regression of one ovary was observed in 40% (4/10) of the heifers treated with CaCl2. Pregnancies were recorded in ≥ 70% of heifers administered each treatment. Results suggest that the treatments used were not able to sterilise most Bos indicus heifers but treatment with CaCl2 has the potential to cause complete ovarian atrophy without causing detectable pain.