Dynamics of nitrogen retention in entire male pigs immunized against gonadotropin-releasing hormone1

Abstract

Immunization against GnRH reduces the occurrence of boar-taint-causing compounds in entire male pigs and is likely to alter growth performance, including whole-body protein deposition (PD; N retention × 6.25). Thirty-six male pigs were used to determine the effects of immunization against GnRH with GnRH analog on N retention and plasma urea nitrogen (PUN; a measure of AA catabolism). Four treatments were used: 1) conventional, early castrates (EC), 2) entire male pigs (EM), 3) entire male pigs immunized with GnRH analog (IM), and 4) entire male pigs surgically castrated after 6 wk of age (between 25 and 40 kg BW; late castrates; LC). The GnRH analog was injected at 30 and 70 kg BW. Within each of 9 litters, 4 males were randomly assigned to the 4 treatments. Pigs were fed corn- and soybean-meal-based diets that were not limiting in essential nutrients for high PD. Five consecutive N balances were conducted between d -9 and -4, 1 and 7, 9 and 16, 20 and 26, and 30 and 36, relative to administration of the booster dose of GnRH analog at d 0. Blood was sampled on d -4, -1, 2, 5, 8, 11, 14, 19, 28, and 37. There was an interactive effect of treatment and time on N retention (P < 0.001). Across periods, N retention for EC and LC were similar (32.7 vs. 33.6 g/d) and lower than EM (39.2 g/d, P < 0.001). The N retention in EM and IM were similar up to d 7 (37.8 vs. 38.5 g/d), tended to be greater for EM than IM between d 9 and 16 (38.4 vs. 34.9 g/d, P = 0.07) and was greater for EM than IM after d 20 (40.9 vs. 34.9 g/d, P < 0.05). Between d 9 and 36, N retention in IM was similar to EC and LC. The PUN concentrations were similar in EC and LC across sampling times (15.50 vs. 15.86 mg/dL) and greater than EM (9.33 mg/dL, P < 0.05). The PUN concentrations were similar in EM and IM up to d 5 (9.88 vs. 9.59 mg/dL), tended to be less in EM than IM on d 8 (9.08 vs. 11.85 mg/dL, P< 0.10), and were lower in EM than IM from d 11 to 37 (8.94 vs. 14.80 mg/dL, P < 0.05). After d 8, PUN concentrations were similar for IM, EC, and LC (14.31, 15.13, and 15.55 mg/dL, respectively). In conclusion, the results of the current study show that N retention and PUN patterns in EC and LC are very similar and lower than those in EM. Between d 7 and 16 after administration of the booster dose of GnRH analog, N retention and PUN in IM changed gradually from EM levels to approach levels in EC and LC, which should be considered when developing feeding programs for IM.

The effect of immunization against GnRF on nutrient requirements of male pigs: a review

“…Mullan, unpublished data). Similar serial N-balance observations (Huber et al, 2012) and data from trials in respiration chambers (J. Noblet et al, unpublished data) also indicate that a sharp decrease in amino acid requirements of immunized boars (in addition to the usual decrease because of increased BW) occurs during the third week after the second immunization.…”

“…The rate of lean tissue deposition of immunized males appears to be maintained Dunshea et al, 2008;Moore et al, 2009) or decreased slightly Rikard-Bell et al, 2009;Huber et al, 2012) compared with that of entire males until approximately 4 weeks after the second immunization. Similarly, the rate of protein deposition, as measured continuously in respiration chambers, was maintained in the 4 weeks after the second immunization (J. Noblet, E. Gonzalo, E. Labussiè re, S. Dubois and J. van Milgen, unpublished data).…”

Effect of feed restriction and initial body weight on growth performance, body composition, and hormones in male pigs immunized against gonadotropin-releasing factor12

“…This was the case regardless of BW at the second immunization against GnRF or feeding level. This result is supported by Bauer et al (2009), Huber et al (2013, and Moore et al (2016). The increase in PUN concentration is caused by the drop in anabolic hormones in IC male pigs, resulting in decreased nitrogen retention (Claus et al, 2007).…”

Standardized ileal digestible lysine requirements of male pigs immunized against gonadotrophin releasing factor1

“…In a nitrogen retention experiment, Huber et al (2013) found that by approximately d 8 after the second immunization against GnRF, the PUN concentration tended to be less in entire males compared with IC males with the PUN concentrations of IC males approaching those of physical castrates between d 7 and 16 following the second immunization against GnRF. In agreement with the current experiment, Bauer et al (2009) also found that PUN concentrations began to increase within 10 d after the second immunization against GnRF whereas Claus et al (2007) found that the PUN concentration increased immediately after the second immunization against GnRF.…”

“…In agreement with the current experiment, Bauer et al (2009) also found that PUN concentrations began to increase within 10 d after the second immunization against GnRF whereas Claus et al (2007) found that the PUN concentration increased immediately after the second immunization against GnRF. Huber et al (2013) attributes the differences in changing PUN concentrations following the second immunization between studies to variation in feed intake and protein deposition patterns.…”