119 Lysine Requirement of Market Gilts Immunized Against Gonadotropin-releasing Factor on Performance and Carcass Composition

The objectives were to determine if the augmented growth performance of gilts administered anti-gonadotropin-releasing factor (GnRF) would require additional lysine and if anti-GnRF-treated gilts would require additional lysine to enhance carcass characteristics. The study treatments were arranged as a 2×3 factorial: control vs anti-GnRF (day 7 and 84; day 0 = 11 wk of age) and lysine at 100, 110, or 120% of requirement of the control gilts. Pen (n = 60) was the experimental unit (10 pens per treatment with 18 or 19 pigs per pen). There was no lysine × anti-GnRF interactions (P ≥ 0.2). Immunized gilts grew 3.7% faster and consumed 3.9% more feed with similar gain:feed from day 0 to market with increases occurring after the administration of the 2nd anti-GnRF dose. Immunized gilts weighed 3.4-kg more at marketing. The timing of marketing (4- or 6-week post 2nd dose) influenced the effects of anti-GnRF. Hot carcass weight, loin depth, and belly weight and thickness in anti-GnRF treated gilts were similar to control gilts at 4-weeks post 2nd dose but were greater in anti-GnRF vs. control (P ≤ 0.05) when harvested 6-weeks post 2nd dose. Backfat was greater, and lean was less, in immunized gilts vs. controls regardless of time to harvest. In conclusion, gilts immunized against GnRF had heavier carcass weights and required no additional lysine compared to controls.

IMMUNOCASTRATION WITH VACCINATION AGAINST GONADOTROPIN-RELEASING FACTOR (GnRF) ON THE PRODUCTION PERFORMANCE OF RAMS

The objective of this study was to investigate the immunocastration using against gonadotropin-releasing factor (GnRF) with Bopriva® (Zoetis) on the performance of production variables, meat quality, docility, and scrotal circumference in young rams, from Sheep production center “Tupac Amaru”, Junin region, Perú. A total of 60 animals were divided into four treatments: T1, T2, and T3 with 0.50 mL, 0.75 mL, and 1.0 mL of doses with Bopriva®, respectively, and T4 (control - 1.0 mL of placebo (distilled water)), with fifteen animals in each. The variables were measured every 15 days for three months (September to November 2018). Datasets were assessed by one-way ANOVA and subsequent posthoc Tukey´s test to detect significant differences among treatments. The results indicated differences found between treatments with the immunocastration compared with non-castrated animals for final weight, carcass weight and performance, scrotal circumference, and docility. Growth performance and meat quality characteristics were not adversely affected by immunocastration. Likewise, immunocastration with Bopriva proved to be effective to stop scrotal development and consequently reduces the sexual and aggressive behavior of young rams. The dose of 0.5 mL seems to be adequate due showed better performance for most variables compared to other treatments

Preliminary study of the effects of an anti-gonadotropin-releasing factor vaccine at two initial liveweights on the carcass traits and meat quality of bulls

The aim of this experiment was to study the effect of the Improvac® anti-gonadotropin-releasing factor vaccine developed for pigs on the carcass quality and shelf life of meat from Serrana de Teruel bulls at two liveweights at the start of immunisation. The anti-gonadotropin-releasing factor vaccine stopped testosterone production regardless of the liveweight. The carcasses of immunised bulls were less heavy and had poorer conformation than those of entire bulls, although the dressing percentages were similar. Immunisation had no influence on the degree of carcass fatness or intramuscular fat content. Immunisation decreased metmyoglobin formation during storage, especially in light bulls. Immunisation reduces the total meat collage, improving tenderness and reducing the ageing time. Minimum toughness was reached 2 weeks earlier than in entire bulls. Quick tenderisation was achieved regardless of the liveweight at immunisation; therefore, the technique studied here could be effective for producing tender meat and avoiding long periods of maturation. In conclusion, immunisation at any of the initial liveweights trialed may be detrimental to animal performance. However, it was effective in delaying metmyoglobin formation and produced more tender meat than that of entire bulls from the first day, thus reducing the ageing time.