In most countries, male pigs are physically castrated soon after birth to reduce the risk of boar taint and to avoid behaviours such as fighting and mounting. However, entire male pigs are more feed efficient and deposit less fat than barrows. In addition, many animal welfare organizations are lobbying for a cessation of castration, with a likelihood that this could lead to inferior pork unless an alternative method is used to control boar taint. An alternative to physical castration is immunization against gonadotrophin releasing factor (GnRF) which allows producers to capitalize on the superior feed efficiency and carcass characteristics of boars without the risk of boar taint. From a physiological perspective, immunized pigs are entire males until shortly after the second dose, typically given 4 to 6 weeks before slaughter. Following full immunization, there is a temporary suppression of testicular function and a hormonal status that resembles that of a barrow. Nutrient requirements will be different in these two phases, before and after full immunization. Given that there have been few published studies comparing the lysine requirements of entire males and barrows in contemporary genotypes, it is useful to use gilt requirements as a benchmark. A series of meta-analyses comparing anti-GnRF immunized boars and physical castrates and use of nutritional models suggest that the lysine requirement of entire males before the second immunization is 5% higher than for gilts, from 25 to 50 kg BW, and by 8% from 50 to 95 kg. Given that the penalty in growth performance for having inadequate dietary lysine is greater in males than in gilts or barrows, it is important to ensure that lysine requirements are met to obtain the maximum benefits of entire male production during this phase. After the second immunization, the lysine requirement of immunized males decreases and may become more like that of barrows. In addition, a consistent effect of full immunization is a marked increase in voluntary feed intake from about 10 days after the second dose. Putting these together, the estimated lysine requirement, expressed in terms of diet composition, falls to 94% of the gilt level. Although general principles can be described now, further research is needed to fully define the lysine requirements of immunized boars. It is important that the temporal pattern of tissue deposition rates and feed intake be explored to be incorporated into models to predict nutrient requirements over the period of rapidly changing metabolism.Keywords: finishing pigs, growth, boars, nutritional requirements, immunological castration. ImplicationsMale pigs immunized against gonadotrophin releasing factor are physiologically entire males for most of their life and as such they should be fed as entire males at least up until the second immunization. Shortly after that time, testicular function is suppressed and the hormonal and metabolic status rapidly adjusts to resemble that of a physical castrate. As a consequence, feed intake and tissue deposition ch...

Forty lactating multiparous Yorkshire sows were used to test the hypothesis that reducing dietary CP and supplementing with crystalline amino acids (CAA) increases dietary N utilization for milk production during early and peak lactation. Sows were assigned to 1 of 4 diets: 1) 16.0% CP (as-fed; analyzed contents; HCP); 2) 15.7% CP (MHCP); 3) 14.3% CP (MLCP); 4) 13.2% CP (LCP); diet HCP was formulated using soybean meal and corn as the only Lys sources. The reduced CP diets contained CAA to meet requirements of the limiting AA. Sow and piglet BW were measured on d 1, 3, 7, 14, 18, and 21 of lactation. Nitrogen retention was measured on sows between d 3 and 7 (early) and d 14 and 18 (peak) of lactation. Milk true protein output was calculated from estimated milk yield and analyzed true protein concentration. Sow BW change (overall mean: -4.2 ± 3.37 kg over the 21-d lactation period) and average daily DM intake (overall mean: 4.05 ± 0.18 and 6.12 ± 0.20 kg/d, early and peak lactation, respectively) did not differ between diets. Nitrogen intake decreased as dietary CP concentration decreased (114.3, 106.0, 107.4, and 99.0 ± 5.29 g/d and 169.5, 168.3, 161.2, and 145.1 ± 5.29 g/d for HCP, MHCP, MLCP, and LCP in early and peak lactation, respectively; L: < 0.05). Sow loin eye area loss tended to increase as dietary CP concentration decreased (Linear (): = 0.082). Litter growth rate (LGR) over the 21-d lactation period tended to increase with decreasing dietary CP concentration (L: = 0.084). In early lactation, N retention (N intake- fecal and urinary N) and milk true protein and casein output were not affected by dietary treatment. In early lactation, as dietary CP decreased, N retained as percentage of N intake tended to increase (L: = 0.093) and estimated efficiency of using retained N for milk N output was not influenced by dietary CP concentration. In peak lactation, N retention (122.5, 123.8, 121.2, and 109.0 ± 4.88 g/d for HCP, MHCP, MLCP, and LCP, respectively) decreased (L: < 0.05), N retained as percentage of N absorbed (N intake - fecal N) increased (L: < 0.05), milk casein yield increased ( = 0.051), and estimated efficiency of using retained N for milk N output (44.5, 51.0, 54.9, and 62.9 ± 5.9% for HCP, MHCP, MLCP, and LCP, respectively) increased (L: < 0.05). Feeding lactating diets reduced in CP from 16.0% to 14.3% with CAA inclusion as partial replacement for limiting AA improved N retention and N utilization efficiency for milk protein production in peak lactation, while these effects were less pronounced in early lactation.

Two experiments were conducted to determine standardized ileal digestibility (SID) of AA (Exp. 1) and net energy (Exp. 2) in two black soldier fly larvae meal (BSFLM) samples [full fat (FF; 42.5% CP, as-fed) and defatted (DF; 40.8% CP; as-fed)] for growing pigs. Two cornstarch-based diets were formulated with FF and DF BSFLM as the sole sources of AA. A nitrogen-free diet was also used and the corn starch:sucrose:oil ratio was kept constant among diets to calculate DE by difference method. In each Exp., pigs were fed 2.8 × estimated maintenance energy requirement. In Exp. 1, 8 ileal-cannulated barrows (25.1 ± 0.41 kg initial BW) were used in a replicated 2 × 2 Latin square design (n = 8). In each period, pigs were adapted to diets for 5 days followed by 2 days of continuous ileal digesta collection for 8 hours. The SID of AA were calculated using basal endogenous losses for pigs fed a nitrogen-free diet. In Exp. 2, 8 barrows (23.4 ± 0.54 kg initial BW) were used in a partially replicated Latin square design (n = 8). In each period, pigs were adapted to diets for 7 days, followed by 5 days of total urine collection and fecal grab sampling. The SID of CP (80.6 ± 1.1 %) and Lys (88.0 ± 1.4 %) were not different between FF and DF BSFLM. The SID of Arg, Val, Ala, and Pro tended to be less, and the SID of Met tended to be greater for the FF versus the DF BSFLM (P = 0.034, 0.090, 0.053, 0.065, 0.074, respectively). Digestible energy (4927 vs 3941± 75 kcal/kg), ME (4569 vs 3396 ± 102 kcal/kg), and predicted NE (3477 vs 2640 ± 30 kcal/kg, using equations from Noblet; 3479 vs 2287 ± 28 kcal/kg, using equations from Blok, respectively) were greater for the FF versus the DF BSFLM (P &lt; 0.05). The apparent total tract digestibility of NDF and ADF were greater for the FF versus the DF BSFLM (P ≤ 0.05). Both FF and DF BSFLM had high SID for most AA, however, FF BSFLM was a better source of net energy for growing pigs. Therefore, both FF and DF BSFLM could be used as protein alternatives in growing pig diets.

Effects of total replacement of soybean meal ( SBM ) with defatted black soldier fly larvae meal ( BSFLM ) on egg production and quality, organ weight, and apparent retention ( AR ) of components were investigated in Shaver White hens from 28 to 43 wk of age. A total of 108 birds, (6 birds/cage) were assigned to three diets (6 replicates/diet). Diets were control corn–SBM diet and two additional diets made with the addition of either 10 or 15% BSFLM. Diets met or exceeded breeder specifications, contained TiO 2 as an indigestible marker, and were prepared in pellet form. Birds had free access to feed and water throughout the experiment. Hen-day egg production ( HDEP ) was monitored daily. Feed intake ( FI ) and body weight ( BW ) were monitored in 4-wk intervals. All eggs laid on the sixth day of wks 31, 35, 39, and 43 were used for egg weight ( EW ), Haugh units ( HU ), yolk color ( YC ), shell breaking strength ( SBS ), and shell thickness ( ST ). Excreta samples were collected for 3 consecutive days on wk 33 for AR and two birds/cage were necropsied at the end. There were no ( P > 0.05) diet effects on HDEP, FI, and HU. Inclusion of BSFLM linearly decreased ( P < 0.05) egg mass and feed conversion ratio ( FCR ) and quadratically increased ( P < 0.05) BW. There was no ( P > 0.05) interaction between diet and sampling time point on egg quality parameters. Inclusion of BSFLM increased SBF and YC linearly ( P < 0.05) and ST quadratically ( P = 0.028). Inclusion of BSFLM quadratically ( P ≤ 0.01) reduced empty ceca weight and increased liver weight and had no effect ( P > 0.05) on gizzard, small intestine, and pancreas weights. Feeding BSFLM linearly ( P = 0.001) and quadratically ( P = 0.007) increased apparent metabolizable energy ( AME ). Data showed that defatted BSFLM resulted in deeper orange yolks and improved eggshell quality; however, unfavorable FCR linked to lighter eggs as well as heavier birds and liver warrants further investigations.

A total of 240 newly weaned pigs (5.25 ± 0.15 kg BW) were used to determine the dietary omega-6-to-omega-3 (ω-6:ω-3) fatty acid ratio that optimized growth performance and immune responses when fed corn and soybean meal (SBM)-based diets with low protein quality. Pigs were randomly assigned to 1 of 5 dietary treatments (n = 6 pens per treatment; day 0 of study): [1] positive control (High; included animal proteins and 5% corn oil), [2] negative control (Low0; corn- and SBM-based and 5% corn oil), or 1 of 3 Low diets with increasing supplementation of fish oil to replace corn oil: [3] 1.25% (Low1.25), [4] 2.5% (Low2.5), [5] 5% (Low5) to achieve 5:1, 3:1, and 1:1 ω-6:ω-3 ratios, respectively. Pigs were fed dietary treatments in 2 phases for 7 and 14 d, respectively, followed by a common phase III diet for 21 d. On day 6 and 20, 12 pigs per treatment were immune sensitized with 0.5 mg ovalbumin (OVA) and 0.5 mg Quil A adjuvant in 1 mL saline. The dermal hypersensitivity response (DHR) was evaluated on day 40 in these same pigs, using intradermal injection of OVA; changes in skin-fold thickness were measured. On day 21, 4 pigs per pen were immune challenged with LPS (30 µg Escherichia coli LPS per kg BW) or saline (n = 12); rectal temperature was monitored over 3 h. During phase I only, ADG, ADFI, and G:F were greater for pigs fed the High diet vs. those fed the Low diet (P < 0.05), and increased with increasing fish oil supplementation up to 2.5% (Low2.5), but decreased for pigs fed the Low5 diet (quadratic; P < 0.05, P = 0.086, and P < 0.05 for ADG, ADFI, and G:F, respectively). On day 21, LPS increased rectal temperature (vs. saline at 1-, 2-, and 3-h post-challenge; P < 0.001); fish oil supplementation reduced rectal temperature 2-h post-challenge in the Low-fed pigs (linear; P < 0.05). On day 22, serum haptoglobin was greatest for pigs fed Low0 and decreased with increasing fish oil supplementation (linear; P < 0.05). Immunization with OVA induced a serum anti-OVA IgG response, which was reduced on day 34 among pigs fed Low diets with increasing fish oil supplementation (linear; P = 0.050). On day 40, and 6 h after intradermal injection of OVA, the DHR was least for pigs fed the Low2.5 diet (P< 0.05). Inclusion of 2.5% fish oil (3:1, ω-6:ω-3) optimized growth performance during the early nursery phase when pigs were most sensitive to diets with low protein quality; the ideal ω-6-to-ω-3 fatty acid ratio may differ when using immune responses as the major outcome.

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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.

One hundred and forty-four newly weaned pigs (6.74 ± 0.23 kg initial BW; 21 days of age) were used to determine the effect of partially replacing animal protein sources with black solider fly larvae meal (BSFLM) in nursery diets on growth performance, gut morphology, and immune response. After weaning, pigs were placed in 24 pens (6 pigs per pen) and pens were randomly assigned to one of four dietary treatments (study d 0; n = 6), which were fed over 3 phases (phases I, II, and III were fed for 7, 14, and 21 days, respectively). Two nursery diets were formulated with 25% (LowFF) and 50% (HighFF) of the animal protein sources replaced by full fat BSFLM. Conventional nursery diets including animal protein sources without (CON-) and with antibiotics (220 mg Aureomycin per kg of complete feed; CON+) served as controls. On day 8, two pigs per pen were sacrificed to collect organ weights and for intestinal histomorphological measurements. On days 9 and 23, two pigs per pen were vaccinated with the novel antigen ovalbumin (OVA). Blood samples were collected on days 9, 23, and 38 to assess concentrations of plasma haptoglobin and OVA-specific immunoglobulins G (IgG) and IgG1. On day 38, the same two pigs per pen underwent a dermal hypersensitivity test and skin-fold thickness was measured at 0, 6, 24, and 48 h post-intradermal injection with OVA. Pigs fed the CON- had greater ADFI and lower G:F in phase 2 versus those fed CON+ and HighFF diets (P &lt; 0.05 and P &lt; 0.05); intermediate ADFI was observed for pigs fed the LowFF diet. Overall in the nursery period, ADG (496 ± 13 g), ADFI (743 ± 23 g), G:F, and final BW (27.61 ± 0.66 kg) were not different among dietary treatments. There were no differences in organ weights, jejunal or ileal villus heights, or crypt depths among dietary treatments. There were no differences in OVA-specific IgG, IgG1, or plasma haptoglobin among dietary treatments at any of the blood sampling times. Although not different, pigs fed the LowFF, HighFF, and CON+ diets had respectively 2.0, 1.7, and 1.4× greater dermal hypersensitivity response to OVA versus those fed CON-. Both inclusion levels of BSFLM in nursery diets supported growth performance, gut morphology, and indices of immune function not different from the CON+, which suggest that full fat BSFLM can replace at least 50% of animal protein sources in nursery diets of pigs without any deleterious effects on pig growth.