Immunization against gonadotropin-releasing factor (GnRF) in market gilts: Effect on growth and carcass parameters, and impact of immunization timing

Using an economic simulation model to identify key drivers of profitability and estimate the environmental sustainability impact of immunization against gonadotropin-releasing factor (GnRF) in male and female pigs intended for market

An existing model was used to identify key drivers of profitability and estimate the impact on environmental sustainability when immunizing finishing pigs against GnRF with Improvac®. The model estimated performance and economic differences between immunized (IM) and non-IM pigs from the perspective of producers and packers, based on two recent meta-analyses in male and female pigs. It was populated with data from 9 countries in four continents (Europe, Asia, North and Latin-America). One-way sensitivity analyses (OWSA) were used to define key drivers of profitability. When changing the country specific input data over a range of ±20%, most OWSA did not reverse the mathematical sign of incremental net return between IM and non-IM pigs as calculated in base case analyses. Only the difference in feed conversion rate between IM and untreated female pigs was a key driver of profitability. The parameters with the highest impact on outcomes were similar across countries and expectable (feed costs), or explainable (parameters with statistical differences between IM and non-IM pigs in meta-analyses). In both single-gender herds, Improvac® reduced the environmental impact of pig production by improving feed efficiency (FE), the key driver of environmental burden. In a 50/50 mixed gender herd, IM pigs consumed less feed and gained more weight in 7 out of 9 countries; in the other two countries the FE calculated for the additional weight gain in IM pigs was >1.00, i.e., each additional kilogram of weight gain was associated with less than one additional kilogram of feed consumed.

Evaluation of Improvest effects on production parameters of gilts from two different genetic sire lines

The objective was to evaluate the effects of Improvest on the performance and carcass characteristics of gilts from two different genetic sire lines and the performance of Improvest gilts with castrated male pigs. It was hypothesized that performance parameters observed for Improvest gilts would be similar to barrows, thus narrowing the performance gaps between traditionally managed gilts and barrows. Pigs were from Large White/Landrace dams and either Duroc-Pietrain (DP) or Duroc (D) sires. Females within each genetic sire line were randomized by weight to receive the first dose of Improvest (IMP) on day 25 of the study or to serve as a nontreated control (DP IMP gilt (n = 6 pens; 19 pigs/pen), D IMP gilt (n = 6 pens; 19 pigs/pen), DP CON gilt (n = 6 pens; 19 pigs/pen), D CON gilt (n = 6 pens; 19 pigs/pen). The second dose of Improvest was administered 6 wk later (i.e., day 67). Barrows did not receive Improvest (DP barrow [n = 10 pens; 19 to 20 pigs/pen], D barrow [n = 10 pens; 19 to 20 pigs/pen]). Average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F) were measured at 21 d intervals throughout the duration of the study. The targeted weight for pigs to be marketed was 133 ± 2.5 kg. Carcass characteristics and loin quality parameters were evaluated on a subset of pigs (n = 283). Improvest-treated gilts of both genetic lines had increased (P ≤ 0.05) ADG and ADFI compared to untreated gilts during the post-second dose intervals with values exceeding that of barrows from day 84 to marketing. Overall, DP IMP gilts had increased (P ≤ 0.05) G:F post-second dose compared to DP CON gilts and DP barrows, yet all other treatments were similar. As pigs were marketed at a similar weight, there was no difference in the final weight, however, DP IMP gilts and DP barrows reached market weight sooner (P ≤ 0.05) than DP CON gilts (109.9 and 111.8 vs. 114.3 ± 0.8 d). Backfat and loin weight were greater (P < 0.01) in IMP gilts versus CON gilts, while IMP gilts and barrows had similar values within each respective genetic sire line. There were no differences between treatments (P ≥ 0.08) for pH and instrumental color of the loins. When the pass rate of loins (Japanese color score ≥ 3.0 and marbling ≥ 2.0) was evaluated, IMP gilts were at intermediate values between CON gilts and barrows for each respective genetic sire line. Overall, Improvest within a genetic line improved gilt carcass measurements so that they were more similar to barrows.

The effect of immunocastration of male and female Duroc pigs on the morphological, mechanical and compositional characteristics of pork belly

Pork belly is an important and heterogeneous cut, characterized by its fat content. Immunocastration is an alternative to surgical castration that can modify the composition of carcasses and cuts and it can affect at its processing. This work compares the morphological, mechanical and compositional characteristics of pork belly of (1) pure Duroc pigs from surgically castrated males (CM), entire females (EF) and immunocastrated females (IF), and (2) Duroc crossbreed pigs from immunocastrated males (IM) and entire males (EM). Two trials were carried out: Trial 1, in which 36 bellies were evaluated, 12 from each sexual type, CM, EF and IF; and Trial 2, where 30 bellies were used, 15 from each sexual type, IM and EM. Results show few differences in bellies from EF and IF, while those from CM were fatter and firmer and with lower polyunsaturated fat. Bellies from IM were longer and firmer than those from EM, and their skin was thinner. IM bellies had higher saturated and lower polyunsaturated fat than those from EM. To conclude, the sex of the pigs affects belly characteristics and this could be a criterion for determining the destination of the bellies in the cutting plant. Immunocastration of pure Duroc females had a lower effect on the belly characteristics when compared to those from entire females, but some differences could be found in the fat distribution. Immunocastration of Duroc crossbred males produces firmer and thicker bellies, with a thinner skin, that could be advantageous for slicing and further processing.

The effect of timing of Improvest administration on growth performance and carcass characteristics in gilts

Improvest (IMP; Zoetis Inc., Parsippany, NJ) has been approved by the U.S. Food and Drug Administration for use in gilts. Improvest is administered twice: the first dose should be administered no earlier than 9 wk of age and the second dose (D2) at least 4 wk after the first dose. The aim of this study was to determine how the timing of IMP before harvest affects growth performance and carcass characteristics in gilts. A total of 1,632 gilts were allocated to four groups (12 pens/treatment; 34 gilts/pen): 1) a control group did not receive IMP; 2) T-early gilts received IMP on day 7 (day 0 = 10 wk postweaning), and D2 on day 40 (i.e., 35 d prior to first removal for harvest); 3) T-medium gilts received IMP on day 21 and D2 on day 56 (i.e., 19 d prior to first removal for harvest); 4) T-late gilts received IMP on day 35 and D2 on day 70 (i.e., 5 d before first removal for harvest). Pigs were selected for harvest by visual observation on days 75, 89, 103, and 117: 1) the heaviest 7 gilts/pen for each treatment on day 75; 2) the heaviest 10 gilts/pen of each treatment at day 89; 3) the heaviest 10 gilts/pen of each treatment on day 103; and 4) the remaining 7 gilts/pen on day 117. Weights and feed disappearance were recorded every 2 wk and during harvest dates to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (Gain:Feed; G:F). Generalized linear mixed models of SAS were used to analyze all variables. The increase in ADFI over Control gilts was observed 15 d post D2 and continued through 77 d post D2, with advantages in ADG occurring between 15 and 35 d post D2. Control and IMP treated gilts had similar G:F 15 to 33 d post D2. The overall ADG and ADFI from day 0 to market, final live weights, and hot carcass weights were significantly greater (P ≤ 0.05) in IMP gilts compared to Control. When G:F based on live weight was averaged across all groups (i.e., from day 0 to market), T-early had the lowest (P ≤ 0.05) G:F compared to Control, T-medium, and T-late gilts, which did not differ. Carcasses from IMP gilts had increased (P < 0.01) backfat, but similar (P = 0.5) Longissimus muscle depth, compared to Control. Within a cohort of similar aged gilts finishing during the summer, this study indicates that the trajectory of growth is enhanced within a similar window post D2 of IMP. Gilts treated with IMP had heavier carcasses with increased backfat and similar Longissimus muscle depth.