Effects of estrus suppression on performance and carcass quality of gilts

Improvac® (Zoetis, Florham Park, NJ, USA; marketed as Innosure® in Colombia) is an anti-GnRF vaccine for the immunological castration (IC) of male pigs for the control of boar taint. However, there is very limited information available about the effects of IC on female pigs by temporal suppression of estrus. The objective of this study was to compare performance and carcass quality of immunocastrated vs. normally maturing females raised in a commercial farm.

229 crossbred gilts (LW x LD x Pi) with initial average weight of 23.0 kg (SD=3.0) were randomly allocated to one of two treatment groups: T1) Control: 107 gilts in 6 pens received a 2mL subcutaneous injection of a 5% dextrose solution at 17 and 22 weeks of age; T2) IC: 122 gilts in 7 pens received two 2mL subcutaneous injections of Improvac behind the ear at 17 and 22 weeks of age. The 13 pens used were similar, allocating 18 pigs at 1.2 m2/pig, with water and feed offered ad libitum. Both treatment groups received the same diet meeting or exceeding recommended nutritional requirements (NRC, 2012) and included 10ppm ractopamine ClH (Paylean®, Elanco) for the last 4 weeks before slaughter at 28 weeks of age.

IC gilts showed significantly higher Average Daily Feed Intake (ADFI; +8.1%, 173 g; 2.27 vs 2.10 kg/day; P< 0.005), Average Daily Gain (ADG; +5.7%, 53 g; 966 vs 913 g/day; P< 0.028) and final weight (FW; +4.8%, 6.47 kg; 140.8 vs 134.3 kg; P< 0.027) than control gilts. Feed conversion rate for both groups was the same (2.45). IC gilts increased ADFI in the last 5 weeks of the study compared with control gilts (3.29 vs 2.64 kg/day; SD: 0.19 and 0.24, respectively), coinciding with the transition to a castrated phase (about one week post second dose of Improvac). Back fat was significantly higher in IC vs. control gilts (20.9 vs 17.7 mm; P< 0.0001), but the total lean meat yield was similar for both treatments (62.6 vs 63.0 kg/carcass; P> 0.05).

IC is a new tool that may help to improve productivity and carcass quality of gilts. The temporary castration induced after the second dose led to increased feed consumption, daily growth and final market weight with no negative impact on feed conversion ratio. The substantial increase observed in feed intake after the second dose opens opportunities to optimize the nutritional program according to the production objectives. Depending on the market preferences, the increase in fat deposition can also be desirable for high quality pork products. More studies are needed to better understand the implications for pork producers.

Disclosure of Interest: J. H. Agudelo-Trujillo Conflict with: research supported by Zoetis, P. A. Guzmán-González Conflict with: research supported by Zoetis, J. F. Gómez-Betancur Conflict with: Zoetis employee, A. Aldaz Conflict with: Zoetis employee.