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How Immunological Castration Affects Pig Carcase Quality

22 February 2014

Immunologically castrated male pigs lost more liveweight during transport and lairage than physically castrated males, intact males or gilts, according to new research from the University of Illinois.

The immunologically castrated animals has a one percentage point higher lean cutting yield than those that had been physically castrated.

Researchers at University of Illinois and Zoetis have determined which tissue components contributed to the reduction in carcass yield of immunologically castrated (IC) barrows when compared to physically castrated (PC) barrows.

In a paper published in Journal of Animal Science, the group, with D.D. Boler as first-named author, explain that the carcass yield of an IC barrow is less than the carcass yield of a PC barrow. This has historically been attributed to the presence of testicles but the testes have only accounted for approximately 0.25 per cent of live weight.

Their experiment included PC barrows, intact males, IC barrows, IC barrows fed ractopamine hydrochloride and gilts.

When the pigs reached 15 weeks old, they were weighed, assigned to treatments (intact male or IC barrow) and penned in groups of four pigs per pen.

Pigs designated for immunological castration were given injections at approximately 16 weeks old and approximately 20 weeks old. Pigs were eligible for harvest 33 days after the second injection when the average weight of the pen reached 130kg.

Immunologically castrated barrows lost on average 0.7 per cent units more liveweight during transport and lairage than PC barrows, intact males or gilts.

Physically castrated barrows had a 1.43 per cent unit advantage over IC barrows in carcass yield. The differences in yield can be attributed to differences in testicles, reproductive tract, intestinal mass, gut fill and some visceral organs.

Testicle weight accounted for a 0.28 per cent unit reduction in carcass yield of IC barrows when compared to PC barrows. Additional reproductive tract weights accounted for differences of 0.10 per cent units.

Intestinal mass (empty large intestine, small intestine, and stomach) was 0.2 per cent units heavier in IC barrows than PC barrows. Livers from IC barrows were 200g heavier (P<0.05) and kidneys were 40g heavier than the same organs in PC barrows. These 2 organs combined for a 0.15 per cent unit difference in carcass yield between IC and PC barrows.

Gut fill, testicles, reproductive tract, intestinal mass and the liver and kidney accounted for 0.97 of 1.43 per cent unit differences in carcass yield between IC and PC barrows.

Immunologically castrated barrows had less marbling than PC barrows but there were no other differences in pork quality parameters.

Cutability differences were less than reported in previous experiments, added Boler and co-authors. However, IC barrows still had a 1.0 per cent unit advantage in lean cutting yield and a 0.7 per cent unit advantage in carcass cutting yield over PC barrows.


Boler D.D., C.L. Puls, D.L. Clark, M. Ellis, A.L. Schroeder, P.D. Matzat, J. Killefer, F.K. McKeith and A.C. Dilger. 2014. Effects of immunological castration (Improvest) on changes in dressing percentage and carcass characteristics of finishing pigs. J. Anim. Sci 92(1):359-368. doi: 10.2527/jas.2013-6863

Further Reading

You can view the full report (fee payable) by clicking here.

January 2014

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