Elevated fat skatole levels in immunocastrated, surgically castrated and entire male pigs with acute dysentery

The effects of different immunocastration protocols on meat quality traits and boar taint compounds in male Bísaro pigs

Immunocastration can be an alternative to surgical castration in Bísaro pigs when there is a need to keep animals on the farm until at least 8 months old. As an autochthonous breed, some particularities must be addressed when doing immunocastration, for which 3 different protocols were tested and two control groups were made with surgically castrated males (SC) and boars (Bo). Two protocols were made in prepubertal pigs, with two (E2) and three inoculations (L3) in the first cycle, and another in adults (A2) with only two inoculations. Physicochemical parameters and boar taint compounds quantification and sensory analysis of the meat from the studied pigs were assessed. Immunocastration provided intermediate values between surgically castrated pigs and entire males, with low levels of boar taint compounds. The L3 group provided closer results to SC, which was also corroborated by the sensory analysis. Although the other two protocols had no significant differences with Bo, there was a positive tendency towards them. As is, the L3 protocol was promising as a good alternative to surgical castration, maintaining the characteristic attributes of the Bísaro pig meat.

Effect of Changes in Dietary Net Energy Concentration on Growth Performance, Fat Deposition, Skatole Production, and Intestinal Morphology in Immunocastrated Male Pigs

Nutritional requirements of heavy immunocastrated (IM) pigs and therefore appropriate feeding strategies have not yet been determined. Thus, the effects of changes in dietary net energy (NE) content were studied in 41 IM pigs, fed ad libitum diets with low, medium, and high NE content (LNE, MNE, and HNE diets, with 8.5, 9.3, and 10.0 MJ NE/kg, respectively), from 84 days of age until slaughter at an average age of 172 days and an average body weight of 122.5 kg. In the period from 143 to 170 days of age, there was a tendency for a greater NE intake (p = 0.08) in pigs fed the HNE diet along with greater (p < 0.01) backfat gain. Dietary treatment affected carcass composition, as lower backfat thickness (p = 0.01) and lower area of fat over the longissimus muscle (p = 0.05) were observed in the LNE and MNE pigs. In addition, greater lean meat content (p = 0.04) was observed in the LNE pigs. Reducing the NE of the diet by replacement of cereals and soybean meal with high-fiber ingredients resulted in lower indole production in the ascending colon (p < 0.01) and greater skatole production (p < 0.01) in the cecum. Greater villus area, width, height and perimeter, crypt depth, and thickness of the intestinal mucosa in the jejunum, ileum, ascending colon, and descending colon were found in the LNE group (p < 0.01) than in the HNE group, while those in the MNE group was intermediate. Cell proliferation was not affected by dietary treatment (p > 0.05). The present results show that a reduction in dietary NE concentration lowers lipid deposition, without affecting performance or energy efficiency in IM pigs. This technique provides an advantage in terms of improved leanness, without affecting growth rate in IM pigs after immunization, which is particularly important when the backfat thickness is a determinant of carcass value and IM pigs are fattened to higher weights (e.g., in heavy pig production) or when a longer delay between immunization and slaughter is practiced.

Evaluation of Coated Biochar as an Intestinal Binding Agent for Skatole and Indole in Male Intact Finishing Pigs

The ban on piglet castration without anaesthesia poses a challenge for the meat industry since alternatives ensuring the production of flawless pork have to be established. The aim of this study was to evaluate the effects of biochar on skatole and indole concentration in faeces and plasma on a small scale in finishing boars to prove whether biochar was suitable for use in commercial pork production. Moreover, it was investigated whether biochar affects faecal properties or the performance. For a four-week trial period, 54 boars (bodyweight 97.2 ± 6.88 kg) were divided into three groups. The control (BC0) received no dietary biochar, one group received a diet containing 4% coated biochar (corresponding to 2% pure biochar) for the final two experimental weeks (BC2), and another group for the entire four weeks (BC4), respectively, prior to slaughter. Skatole and indole concentrations were measured in faeces and plasma at the beginning, in the middle and at the end of the trial. Mean skatole concentrations did not differ between groups, but in BC2 faecal skatole was significantly decreased at day 26, whereas in BC4 initial and final faecal skatole levels did not differ. At day 15 and 26, the faecal dry matter content was significantly higher in pigs fed the biochar diet (p < 0.05).

On-farm prevalence of and potential risk factors for boar taint

Boar taint is an unpleasant taste and odor that can occur in entire male pigs and is caused by androstenone, skatole, and to a lesser extent indole accumulating in fat tissue. In the present observational study, we evaluated an extensive list of such potential risk factors which influence boar taint: social hierarchy and puberty attainment, housing, health, preslaughter conditions, season, feed, carcass composition, slaughter weight or age, and breed. Details on these factors were collected by interviews with the participating farmers, observations on each farm by trained observers and farmers, as well as slaughterhouse data. Twenty-two farms (in West- and East-Flanders, ranging from 160 to 600 sows, selected on suitability) raising entire male pigs were included in the study to evaluate the link between boar taint and potential risk factors related to the farm and slaughter batch (114 slaughter batches and 16 791 entire male pigs in total). Average olfactory boar taint prevalence was 1.8 ± 0.8%. Boar taint prevalence varied also within farms up to a maximum range between slaughter batches of 9.1% which suggests an effect of factors varying between slaughter batches such as season or other variables varying between slaughter batches. Less aggressive behavior at the end of fattening as well as lower skin lesion scores at fattening as well as at slaughter could be associated with less boar taint. The same might be said for sexual behavior, though less convincingly from this study. Measures that reduce aggression and stress have therefore have the potential to lower boar taint prevalence. The same might be said for sexual behavior, though less convincingly from this study. Furthermore, boar taint prevalence was generally higher in winter than in summer, which is relevant from a planning perspective for the slaughterhouses to seek alternative markets. Finally, increased CP gave significantly lower boar taint prevalences. This may to some extent be explained by the negative association between boar taint and lean meat percentage, as increased dietary CP levels promote the carcass lean meat percentages which can then be associated with lower boar taint levels.

Influence of Housing Conditions on Reliability of Immunocastration and Consequences for Growth Performance of Male Pigs

Simple Summary

Surgical castration of male piglets is societally criticized as it is painful and violates the integrity of the animals. Pork production with boars and immunocastrates are possible alternatives. Even if immunocastration is an animal-welfare-friendly alternative, its market share is low and the reliability of this technique is discussed controversially within the pork chain. Currently, the number and the reason for non-responders to vaccination are not clear. Various factors may contribute to impaired immune response including adverse and stressful housing conditions. This study, therefore, examines the influence of different housing conditions on the immune response after two Improvac^® vaccinations. To determine vaccination success, testosterone concentrations, GnRH-binding, and boar taint compounds were evaluated. Furthermore, the growth performance of male pigs was compared. The results show that immunocastration is reliable under different housing systems and prevents boar taint. Moreover, the growth performance of immunocastrates is high and even superior to that of boars and barrows after the 2nd vaccination. Accordingly, immunocastration is not only animal-welfare-friendly but also economically attractive and suitable for different housing systems.

Abstract

Immunocastration is a sustainable alternative to piglet castration but faces limited market acceptance. The phenomenon of non-responders has not to date been examined in detail, but adverse and stressful housing conditions (e.g., mixing of groups) might impair the success of vaccinations. Therefore, we evaluated the influence of housing conditions on the immune response after two Improvac^® vaccinations at an age of 12 and 22 weeks, respectively. Boars, immunocastrates and barrows (n = 48 each) were assigned to three different housing conditions (n = 36 enriched, n = 36 standard n = 72 repeated social mixing). Immune response was quantified by measuring GnRH-binding and its consequences for testosterone concentrations, development of the genital tract and boar taint. Growth performance was evaluated via average daily gain (ADG). GnRH-binding and testosterone levels revealed that immunocastration reliably suppressed testicular functions after the 2nd vaccination. Housing conditions did not modify testicular function but influenced ADG as animals under mixing grew slower than those under enriched conditions. Gonadal status had only a slight impact on ADG except in immunocastrates, which showed a temporarily higher ADG after the 2nd vaccination. The results show that immunocastration is a reliable procedure under different housing conditions and competitive in terms of growth performance.

Monitoring of behavior, sex hormones and boar taint compounds during the vaccination program for immunocastration in three sire lines

Immunocastration (vaccination against boar taint) is an alternative method to prevent boar taint without the need for surgical castration. This study investigates the evolution of boar taint compounds in serum and fat, serum steroid compounds as well as behavior in immunocastrated pigs from 3 sire lines: 15 stress positive Belgian Piétrain (BP), 20 stress negative French Piétrain (FP), and 20 stress negative Canadian Duroc (CD). Hormone and boar taint compounds in serum were determined at 4 time points; boar taint compounds in fat were determined at 3 time points. Behavior, skin lesions, animal and pen fouling were also recorded before the first vaccination (<V1), between the first and second vaccination (<V2), and after the second vaccination (>V2). Aggressiveness, eating and drinking and general activity behavior declined from <V1 to <V2 and > V2 for all sire lines. Pigs from BP were cleaner than FP and CD pigs. Even though immunocastration was effective in general (reduced testosterone, estradiol as well as androstenone in serum) for all sire lines, some individual pigs showed either androstenone or skatole levels in fat above cutoff values. While the immunocastration mechanism works as intended for androstenone, and also for skatole for the three sire lines, the risk of carcasses with boar taint compounds above cutoff levels (respectively 1.9 and 3.7%) still remains to some extent.

Nutrient digestibility, organ morphometry and performance in vaccinated or non-vaccinated Lawsonia intracellularis infected piglets

Background

Lawsonia intracellularis is one of the world’s most important infectious diseases in pork production with regard to economic losses. So far, studies are missing that describe the effects of a natural infection of piglets on the digestibility of nutrients, possible effects on performance and the morphometrics of the intestine depending on whether piglets are vaccinated, clinically healthy or clinically affected with regard to Lawsonia intracellularis induced diarrhoea.

Results

Digestibility studies were performed on a total of 27 eight-week-old piglets with naturally occurring Lawsonia intracellularis infection in a trial with three repetitions. Nine out of 27 animals were vaccinated as suckling pigs with a commercial Lawsonia intracellularis vaccine (vac; Enterisol®Ileitis). Half of the remaining 18 animals were without clinical signs of infection (non-vac/cs-), half showed moderate clinical signs of Lawsonia intracellularis induced diarrhoea (non-vac/cs+). All three groups were fed one identical complete diet ad libitum. Faecal shedding of Lawsonia intracellularis was found in all groups (25 out of 27 animals). Numerically, the mean excretion in the group non-vac/cs + (7.69 ± 1.65 log₁₀ copies/ g faeces) was higher in comparison to the group non-vac/cs- (5.83 ± 2.35 log₁₀ copies/ g faeces) and vaccinated animals (vac: 6.00 ± 2.89log₁₀ copies/ g faeces). The average daily weight gain (ADG; Ø 8.66 day period) differed significantly (vac: 894^a ± 73.3, non-vac/cs-: 857^ab ± 86.3, non-vac/cs+: 785^b ± 137 g/day). The apparent total tract digestibility (ATTD) of nitrogen was significantly lower in clinically affected animals (vac: 83.0^a ± 1.72, non-vac/cs-: 83.9^a ± 2.03, non-vac/cs+: 80.7^b ± 2.57).The total length of the small intestine in clinically affected animals increased significantly (vac: 15.9^ab ± 1.57, non-vac/cs-: 14.6^b ± 1.12, non-vac/cs+: 16.2^a ± 1.37 m). The relative body weight depending on the length of the small intestine was lower for clinically affected animals (vac: 1.72^a ± 0.21, non-vac/cs-: 1.83^a ± 0.17, non-vac/cs+: 1.56^b ± 0.12 kg/m).

Conclusion

These studies show that clinically moderate L. intracellularis infections lead to significantly lower ADGs in comparison to vaccinated animals. The disease is also found in altered intestinal morphometry and reduced total N digestibility if clinical signs occur.

Chicory fructans in pig diet reduce skatole in back fat of entire male pigs

Androstenone, skatole and indole are main compounds responsible for boar taint, an off-odour in meat of some entire male pigs. Several feed ingredients derived from chicory have been reported to reduce fat skatole levels, while results for indole are more contradictory. The skatole-reducing effect is probably based on the prebiotic effects described for fructan compounds. Inulin and oligofructose have a high and low degree of polymerization, respectively. The fermentation rate decreases with an increasing degree of polymerization, which may result in differing effects of the compounds on skatole and/or indole levels. In this study we evaluated the effect of the inclusion of 5% inulin or 5% oligofructose during the last 3weeks before slaughter on carcass quality, concentration of skatole and indole in back fat as well as on the olfactory evaluation of boar taint in fat. Carcass weight did not differ between treatment groups but lean meat percentage increased when feeding oligofructose (P=0.019) compared to the control group, which is relevant for further research. Inclusion of 5% inulin or 5% oligofructose in the finisher diet of entire male pigs significantly reduced the back fat skatole concentration, without influence on indole. Olfactory score for boar taint tended to decrease when oligofructose was added to the diet.

Influence of the inflammatory status of entire male pigs on their pubertal development and fat androstenone

Androstenone production increases during pubertal development and plays a major role in boar taint. The objective of the present study was to evaluate the effect of a subclinical inflammation on the pubertal development of boars and hence on fat androstenone. Contrasted hygiene conditions were applied during rearing to increase the variability of the inflammatory status. Boars from a commercial cross line were allocated at 139±0.9 days of age (Day 0) and 81.3±5.9 kg of live weight either to Good (n=61) or Poor (n=54) hygiene conditions until slaughter at 172.9±4.8 days of age and 116.7±4.5 kg live weight. Inflammatory status, growth and pubertal development were evaluated on Day 0, Day 27 and at slaughter by analysing the blood formula, plasma inflammatory proteins; testosterone and oestradiol, salivary cortisol, rectal temperature, live weight, back fat thickness, weight of reproductive organs and clinical scores of organs (lungs, stomach, snout). Fat was collected on Day 27 by biopsy and at slaughter to measure androstenone concentration. A principal component analysis including inflammatory indicators followed by a clustering procedure was performed to identify pigs with a high (Infl+, n=50) or a low (Infl-, n=65) inflammatory status. Infl+ pigs had more granulocytes/ml, higher concentrations of haptoglobin, C-reative protein and cortisol (P<0.05), lower growth rate and higher lung pneumonia score. However, regardless of stage, the inflammatory status had no significant effect on plasma testosterone or oestradiol, fat androstenone or sexual organ development. Present data suggest that a mild inflammatory status has no influence on pubertal development or fat concentration of androstenone in boars.

Effect of faecal soiling on skatole and androstenone occurrence in organic entire male pigs

Production of entire male pigs could be a future strategy for organic pig production. However, production of entire males leads to increased risk of carcasses with elevated boar taint levels. It is hypothesized that skatole levels in pig meat are affected by faecal soiling and that organic housing facilities can increase the risk of pigs being heavily soiled. Therefore, the overall aim of this study was to investigate if increased pig and pen soiling increases skatole concentration in entire male pigs. In five herds, 1174 organic entire male pigs were reared in four batches across two seasons, summer and winter. Measurements of pig and pen soiling, as well as fat skatole and androstenone concentration and human nose sensory tests of fat odour, were performed. Skatole and androstenone concentrations varied greatly within and between herds with a 10% and 90% percentile for the overall population of 0.02 and 2.25 µg/g for skatole and 0.53 and 4.84 µg/g for androstenone. Human nose positive tests averaged 18.3% with great variation between herds and seasons. Pen soiling had significant effects on pig soiling. Moreover, outdoor pen soiling significantly affected skatole concentration in interactions with herd and season (P<0.001 and P=0.003) and affected human nose positive risk in interaction with herd (P=0.005). Soiling on indoor pen areas did not affect skatole levels and no effect on androstenone was found for any pen area. Soiling of pigs affected both skatole and androstenone levels, with the size of the head and abdomen body areas covered in manure showing significant positive effects on skatole concentration. No effect of density of the manure layer was found on either boar taint measure. Herd significantly affected both skatole and androstenone in fat as well as the human nose positive risk. The human nose test revealed no effect from pig soiling. A large variation in the different boar taint measures was found for both high and low scores of pen and pig soiling, and only a small difference in skatole and androstenone concentrations between the high and low soiling categories was found. Therefore, while increasing the hygiene management could be a strategy for reducing boar taint in production of organic entire male pigs, it should be emphasized that other factors would also need to be considered.