A comparison of immunological, chemical and surgical castration of Nelore bulls

Abstract

The objective was to compare effects of immunological, chemical and surgical castrations on testicular characteristics, scrotal surface temperatures, sperm quality, and serum testosterone concentrations in Bos indicus bulls. Eighty Nelore bulls (∼20 mo) were grazed on pasture, fed a supplement and slaughtered at ∼480 kg. Bulls were allocated into four groups (n = 20/group). The control group (CON) was non-castrated and there were three castration methods: immune (IMM - Bopriva®), injected on D-30, D30 and D60; chemical (CHE), an intratesticular injection of 40% CaCl2 + 0.5% dimethylsulfoxide on D0; and surgical (SUR) on D0. The CHE group were surgically castrated on D60, due to testicular swelling and necrosis of scrotal skin. Most scrotal surface temperatures (infrared thermography) were significantly higher on D15 in CHE and SUR compared to CON, due to inflammation. All bulls were subjected to a breeding soundness evaluation on D-7 and slaughtered on D220. Scrotal circumference and testicular volume did not differ among groups (P > 0.05) at D0, but at D15, both end points were highest (P < 0.05) in the CHE group (due to swelling), although both end points were smaller for IMM versus CON (P < 0.05) at D60 and D150. Sperm motility in the IMM group was ∼50 and 10% of that in the CON group on D60 and D150, respectively. For the IMM group, serum testosterone concentrations were similar on D0 and D15 (but ∼50% of CHE or SUR on D0, attributed to the first treatment on D-30), and had decreased ∼70% on D60 and D150, whereas in the CHE and SUR groups, there were ∼80–90% decreases in testosterone after D0. In conclusion, immunological castration was a viable alternative to surgical castration, as it supressed testosterone production and spermatogenesis, with the benefits of being much less invasive, with better animal welfare and less stress.