Protein turnover in pigs: A review of interacting factors

Protein turnover defines the balance between two continuous and complex processes of protein metabolism, synthesis and degradation, which determine their deposition in tissues. Although the liver and intestine have been studied extensively for their important roles in protein digestion, absorption and metabolism, the study of protein metabolism has focused mainly on skeletal muscle tissue to understand the basis for its growth. Due to the high adaptability of skeletal muscle, its protein turnover is greatly affected by different internal and external factors, contributing to carcass lean-yield and animal growth. Amino acid (AA) labelling and tracking using isotope tracer methodology, together with the study of myofiber type profiling, signal transduction pathways and gene expression, has allowed the analysis of these mechanisms from different perspectives. Positive stimuli such as increased nutrient availability in the diet (e.g., AA), physical activity, the presence of certain hormones (e.g., testosterone) or a more oxidative myofiber profile in certain muscles or pig genotypes promote increased upregulation of translation and transcription-related genes, activation of mTORC1 signalling mechanisms and increased abundance of satellite cells, allowing for more efficient protein synthesis. However, fasting, animal aging, inactivity and stress, inflammation or sepsis produce the opposite effect. Deepening the understanding of modifying factors and their possible interaction may contribute to the design of optimal strategies to better control tissue growth and nutrient use (i.e., protein and AA), and thus advance the precision feeding strategy.

Novel gels and films to mask boar taint in entire male pork

Boar taint masking strategies were developed using hydrocolloids and spices to produce edible gels and films. Carrageenan (G1) and agar-agar (G2) were used for the gels and gelatin (F1) and alginate+maltodextrin (F2) for the films. The strategies were applied to both castrated (control) and entire male pork with high levels of androstenone and skatole. The samples were evaluated sensorially by a trained tasting panel through quantitative descriptive analysis (QDA). Lower hardness and chewiness of entire male pork, with high levels of boar taint compounds object of study, were found with the carrageenan gel, due to the better carrageenan gel adherence to the loin. The films showed that the gelatin strategy tended to have a certain "sweet" taste, and a higher overall masking than the alginate+maltodextrin film. In conclusion, a trained tasting panel found that gelatin film masked boar taint the most, followed by the alginate+maltodextrin film and the carrageenan-based gel.

Relationship between energy intake and growth performance and body composition in pigs selected for low backfat thickness

Genetic selection of pigs over recent decades has sought to reduce carcass fat content to meet consumer demands for lean meat in many countries (e.g.: Australia). Due to the impacts of genetic changes, it is unknown whether the carcass fat measures are still responsive to energy intake. Thus, the present experiment aimed to quantify the relationship between tissue composition and dietary energy intake in finisher pigs selected for low carcass backfat. Intact male and female pigs (n=56 for each sex; PrimegroGenetics, Corowa, NSW, Australia) were fed seven different amounts of an amino acid adequate wheat-based diet containing 14.3 MJ digestible energy (DE)/kg to provide the following daily DE intakes- 25.8, 29.0, 32.6, 35.3, 38.5, 41.5 and 44.2 (ad libitum) MJ DE/d for males, and 25.8, 28.9, 32.0, 35.6, 38.3, 40.9 and 44.5 (ad libitum) MJ DE/d for females between 60 kg and 108 kg live weight. Body composition of anaesthetised pigs was measured using the Dual Energy X-ray Absorptiometry (DXA) method when individual pigs reached 108 kg, and protein, fat and ash deposition rates were calculated. Pigs were slaughtered on the 2nd day post-DXA scan for carcass backfat measurement. The results showed that the carcass backfat thickness (standardized at 83.7 kg carcass) increased by 0.125 mm for every MJ increase in daily DE intake in male pigs (P = 0.004; R2 = 0.130), but carcass backfat of female pigs (standardized at 85.1 kg carcass) was not responsive to daily DE intake. Whole-body fat composition and fat deposition rate increased linearly (both P < 0.01) in male pigs but quadratically (both P < 0.01) in female pigs in response to DE intake. Every MJ increase of daily DE intake increased the rate of daily protein deposition by 3.8 g in intact male pigs (P < 0.001; R2 = 0.781) and by 2.5 g in female pigs (P < 0.001; R2 = 0.643). In conclusion, the selection for low backfat thickness over the last two decades has altered the response of fat deposition and backfat thickness to energy intake, particularly in female pigs. Despite this change, the linear relationship between DE intake and protein deposition rate was maintained in these modern genetics.

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

Pigs immunized against gonadotropin-releasing factor (GnRF) have increased carcass fatness compared to entire males; however, the timing of this increase in fatness after the second immunization against GnRF has not been determined. An experiment was conducted to identify and compare the growth performance, body composition, and physiological changes in immunocastrated males (IC males) at different BW and feeding levels. A total of 64 pigs were used in a 2 × 2 × 2 factorial experiment with the treatments being 1) sex (entire males or IC males), 2) initial BW (45.9 kg [light] or 78.3 kg [heavy]), and 3) feeding regime (2.5 times maintenance [restricted] or ad libitum). The pigs were individually housed, and the diets were fed for 4 wk after the second immunization against GnRF until slaughter at either 68.4 kg BW (light) or 105.8 kg BW (heavy). Immunocastrated males on a restricted feed intake had a lower ADG compared to entire males from d 15 to 28 and d 0 to 28 ( 0.011 and 0.011, respectively). Fat deposition was not affected by sex from d 0 to 14, but from d 15 to 28 IC males deposited 45 g/d more fat than entire males ( = 0.025). Immunocastrated male pigs fed ad libitum deposited 87 g/d more fat from d 15 to 28 than entire males fed ad libitum ( = 0.036). However, there was no difference in fat deposition between IC males and entire males when feed intake was restricted from d 15 to 28. Plasma urea nitrogen levels were greater in IC males compared to entire males from d 7 after the second immunization against GnRF ( 0.05 for d 7, 10, 14, 21, and 28). Plasma concentrations of IGF-1 were lower for IC males compared to entire males on d 3, 7, 10, and 28 ( 0.05 for all days). The following conclusions were made: 1) when pigs are immunized at a light BW (50 kg) and/or are on a restricted feed intake, they have a reduced propensity to deposit fat; however, the restriction in feed intake adversely affects growth rate. 2) The majority of fat deposition for males immunized at heavy BW (80 kg) occurs from d 15 to 28 after the second immunization against GnRF.

Effects of dietary protein-to-energy ratio on rate of growth, protein deposition and tissue composition of pure Iberian boars prior to extensive production

Thirty entire male Iberian (IB) pigs of 12 kg initial BW were used to study the effects of dietary protein-to-energy ratio on performance, body protein accretion, and tissue composition. Two nutritional regimes were supplied at 3 stages of growth (Phase I, from 12 to 30 kg BW; Phase II, from 30 to 45 kg BW; and Phase III, from 45 to 100 kg BW): the first regime (RefP/E) was formulated to provide optimum protein-to-energy ratios for castrated IB pigs at several stages of growth from 10 to 100 kg BW; the second (IncP/E), for which an overall increase of 2.5 g digestible protein/MJ ME was provided, would allow an increased potential for lean tissue growth presumably well above that expected for the entire male of an obese pig breed. The pigs were surgically castrated at 45 kg BW and slaughtered at about 100 kg BW. In Phases I and II, in which feed was provided ad libitum, no significant differences between dietary treatments in ADG (580 ± 10 and 740 ± 11 g, on average, respectively), G:F (0.475 ± 0.004 and 0.362 ± 0.005, on average, respectively), and gain:ME intake ratio (37.8 ± 0.4 and 26.1 ± 0.4 g/MJ, on average, respectively) were found ( > 0.05). After surgical castration, for the entire fattening period (Phase III), ADFI was fixed and highly restricted. A lower gain:ME intake ratio (14.0 vs. 15.1 g/MJ; < 0.01) was obtained when the diet with the highest digestible protein:ME ratio was offered (IncP/E). With this regime, body protein accretion significantly improved in the IB boar growing from 12 to 45 kg BW, irrespective of the stage of growth, although the amount of protein accreted was notably enhanced at the later stage (75 vs. 85 g/d in Phase I [ < 0.05] and 110.5 vs. 151 g/d in Phase II [ < 0.001]). However, the efficiency of utilization of dietary N remained unchanged irrespective of the diet fed ( > 0.05). In contrast, in the fattening stage, similar daily rates of N retention ( > 0.05) were found, in spite of the observed differences in digestible N intake ( < 0.001). We concluded that the protein (lysine) requirements of the IB boar growing from 12 to 30 kg BW and from 30 to 45 kg BW are met with the supply of 11.5 and 10.2 g digestible protein of ideal AA pattern/MJ ME (0.80 and 0.71 g digestible lysine/MJ ME), respectively. As surgical castration is programmed to be abandoned in European Union by 1 January 2018, this information will be important for the efficient production of the immunologically castrated IB pig, at the earlier stages of growth.

The Effect of Lupinus albus on Growth Performance, Body Composition and Satiety Hormones of Male Pigs Immunized against Gonadotrophin Releasing Factor

Two hundred and ninety four pigs were used with the aim to develop a dietary management strategy using Lupinus albus L. (albus lupins) to reduce the increase in feed intake and subsequent increase in carcass fatness in pigs immunized against gonadotrophin releasing factor (immunocastrates; IC males) and entire male pigs in the late finishing stage. From day (d) 0 to 28, IC males fed the control diet grew faster (p = 0.009) than entire males fed the control diet but there was no difference in growth rate between sexes for pigs fed albus lupins for 14 days pre-slaughter (Albus 14) or pigs fed albus lupins for 28 days pre-slaughter (Albus 28). From d 15 to 28, IC males receiving the Albus 14 diet grew more slowly (p < 0.001) than entire males receiving the Albus 14 diet. From d 15 to 28 (p < 0.001), IC males fed the control diet ate more feed than entire males fed the control diet, although there was no difference between sexes in feed intake of the Albus 14 and Albus 28 diet. Immunocastrates had a lower backfat when fed either Albus 14 or Albus 28 compared to the control diet, although there was no difference between diets for entire males. There was also a trend for pigs on the Albus 14 and Albus 28 diets to have a higher lean deposition (p = 0.055) and a lower fat deposition (p = 0.056) compared to the pigs on the control diet. Pigs fed the Albus 28 diet had a lower plasma ghrelin concentration compared to pigs fed the Albus 14 or the control diet (p = 0.002). Pigs fed the Albus 28 diet had a higher peptide YY concentration than those fed the control or albus 14 diet (p = 0.004). The inclusion of albus lupins at 20% in the diets of IC male pigs for either 14 or 28 days pre-slaughter was successful in reducing feed intake, body fat and backfat to similar levels of entire males. However, the growth rate of the IC male pigs was impacted more than would be desirable.

The Effect of Lupinus albus and Calcium Chloride on Growth Performance, Body Composition, Plasma Biochemistry and Meat Quality of Male Pigs Immunized Against Gonadotrophin Releasing Factor

Simple Summary

Pigs immunized against gonadotrophin releasing factor (immunocastrated (IC) males) have an increased feed intake, growth rate, back fat and fat deposition compared to entire males. It is desirable to develop management strategies to limit the increase in feed intake and fat deposition in IC males. This experiment used in-feed ingredients (Lupinus albus (albus lupins) or a combination of calcium chloride and sodium tri-polyphosphate (mineral salts)) to try to suppress the voluntary feed intake of IC male pigs and subsequently fat deposition. Mineral salts decreased feed intake with no effect on fat deposition while albus lupins reduced both feed intake and fat deposition in pigs.

Abstract

Two hundred and ninety-four pigs were used to assess the effect of two ingredients (Lupinus albus (albus lupins) or a combination of calcium chloride and sodium tri-polyphosphate (mineral salts)) on growth performance, body composition and objective meat quality of pigs immunized against gonadotrophin releasing factor (immunocastrates) and entire male pigs in the late finishing phase. Pigs fed mineral salts ate less feed than those fed the control diet with no effect on growth rate (p > 0.05), backfat (p > 0.05) or fat deposition (p > 0.05). Pigs fed albus lupins had a reduced feed intake (p < 0.001 for all time periods), lower growth rate (p < 0.001 for all time periods), lower backfat (p < 0.005) and decreased fat deposition (p < 0.001 for all time periods) compared to those fed the control diet or mineral salts. From day (d) 0–28 pigs fed mineral salts had a better feed conversion ratio (p = 0.001) than those fed albus lupins who in turn had an improved feed conversion compared to the control diet. Immunocastrates had thicker backfat than entire males at the end of the experiment (p < 0.001), however, feeding albus lupins to immunocastrated males reduced backfat thickness to similar to entire males fed the control diet (p = 0.01). With the exception of the increased muscle pH at 45 min post-exsanguination in mineral salts and albus lupins compared with the control diet (p = 0.03) there was no effect of diet on objective pork quality. Pork from IC males had a higher ultimate pH (p < 0.001), was lighter (L*; p = 0.003), more yellow (p = 0.008) and had a higher drip loss (p < 0.001) compared to entire males. Albus lupins show potential in reducing the increase in feed intake and backfat associated with immunocastration. Mineral salts may be useful in situations where a reduction in feed intake and an improvement in feed conversion is desired and reducing fat deposition is not the objective.

Effect of an anti-gonadotropin-releasing factor vaccine on sexual and aggressive behaviour in male pigs during the finishing period under Australian field conditions

OBJECTIVE

The objective of this study was to evaluate the effectiveness of an anti-gonadotropin-releasing factor vaccine in controlling sexual and aggressive behaviour of male pigs in the late finishing period under Australian field conditions.

METHODS

Male pigs from four consecutive batches over a 4-month period were randomly assigned to two groups: an untreated control group (n = 434) or a group treated with Improvac® (n = 433). The vaccine was administered at 10 and 16 weeks of age. Pigs were housed under commercial conditions in ecoshelters, a commonly used housing system in Australia in which pigs are kept in large pens often containing >100 animals. The occurrence of sexual and aggressive behaviours was recorded and evaluated after second vaccination until slaughter at 22 weeks of age.

RESULTS

Male pigs treated with Improvac demonstrated significant reductions in mounting, fighting, pushing, head butting and tail manipulation when compared with control animals.

CONCLUSION

This study confirms that vaccination with Improvac can improve the welfare of entire male pigs by inhibiting sexual and aggressive behaviour.

Influence of a gonadotropin-releasing hormone vaccine and dietary standardized ileal digestible lysine level on growth performance and carcass quality of grower-finisher pigs

The aim of this study was to assess the effect of standardized ileal digestible (SID) Lys levels of the diet on the growth performance, carcass characteristics, and meat quality of entire males (EM), surgical castrates (SC), and males vaccinated with a gonadotropin-releasing hormone (GnRH) vaccine (GV). In total, 252 crossbred pigs were fed 6 different experimental diets consisting of 3 sexes (EM, SC, and GV pigs) and 2 dietary SID Lys levels (2008 CVB standard SID Lys recommendation [Std] or 15% extra SID Lys [+15]) according to a 3-phase feeding scheme (d 0 to 35, 35 to 70, and 70 to 105 of experiment) with 6 pens per treatment and 6 pigs per pen. To determine if dietary SID Lys could be reduced for GV males after the second vaccination, an additional dietary treatment was included (GV+15-Std). The GV males on the GV+15-Std were fed the diet with 15% extra SID Lys in the starter and grower phases and the standard SID Lys level in the finisher phase. First vaccination was administered to pigs at the start of the experiment (23.4 kg BW and 63.6 d of age), and the second vaccination occurred 6 wk before slaughter (77.2 kg BW and 126.6 d of age). Until the second vaccination, GV pigs showed a lower (P ≤ 0.05) ADFI than SC but similar to EM. After the second vaccination, GV pigs had an intermediate (P ≤ 0.05) G:F between EM and SC. The GV+15 pigs showed a better G:F (P ≤ 0.05) than GV pigs fed the GV+15-Std diet in the finisher phase. No differences in the growth rate of the pigs were observed. The SC had a greater (P ≤ 0.05) carcass weight and dressing percentage than EM and GV pigs. The GV-Std pigs had a lower (P ≤ 0.05) meat percentage and greater (P ≤ 0.05) backfat thickness than the GV+15 pigs. The GV pigs and SC fed the standard SID Lys diet had a greater (P ≤ 0.05) percentage of SFA in the subcutaneous fat than EM+15 pigs. On the other hand, SC showed the greatest (P ≤ 0.05) concentration of MUFA compared to EM and GV pigs. The SC and GV pigs had a lower (P ≤ 0.05) PUFA percentage in the subcutaneous fat than EM fed the standard SID Lys diet.

Performances, meat quality and boar taint of castrates and entire male pigs fed a standard and a raw potato starch-enriched diet

In Europe there is increasing concern about the common practice of surgical castration of piglets without anaesthesia. One possible alternative to completely avoid castration is entire male pig production. Thus, the objective of the study was to compare the growth performance, carcass characteristics, organ weights, meat quality traits, fat score and boar taint compounds in the adipose tissue of group-penned entire male pigs and castrates. Furthermore, the effect of raw potato starch (RPS) fed for 7 days prior to slaughter was determined. Pigs (n = 36) were blocked by BW into 12 blocks (3 littermates/block) and assigned to three experimental groups: surgical castrates (C); entire males (EM); and entire males offered RPS (30 g RPS/100 g diet) for 7 days prior to slaughter (EM+). Pigs had ad libitum access to the feed from 22 to 107 kg, individual feed intake was recorded daily and BW once a week. Entire males grew slower (EM: 771, EM+: 776 v. C: 830 g/day; P < 0.01), consumed less feed (EM: 1.87, EM+: 1.89 v. C: 2.23 kg/day; P < 0.01) and were more efficient (feed conversion ratio: EM: 2.42, EM+: 2.44 v. C: 2.69 kg/kg; P < 0.01) than C. Compared to C, carcass dressing percentage was lower (EM: 79.4, EM+: 79.4 v. C: 81.6%; P < 0.01) and percentage of valuable cuts was higher (EM: 57.3, EM+: 56.5 v. 52.6%; P < 0.01) in entire males. The hearts (EM: 426, EM+: 425 v. C: 378 g), kidneys (EM: 387, EM+: 378 v. C: 311 g), bulbourethral (EM: 200, EM+: 195 v. C: 7 g) and salivary glands (EM: 99, EM+: 94 v. C: 42 g) were heavier (P < 0.001) in entire males than in C. Meat quality traits did not (P > 0.05) differ among experimental groups but the adipose tissue was more unsaturated in entire males than in C as indicated by the higher fat scores (EM: 69.1, EM+: 67.2 v. C: 63.6; P < 0.01). Feeding RPS reduced (P = 0.04) the skatole tissue concentrations (expressed in μg/g lipid) in EM+ (0.22) compared to EM (0.85), whereas androstenone and indole levels were not (P 0.60) affected (EM: 1.7 and 0.10, EM+: 2.0 and 0.09, respectively). Although the current results confirmed the high efficiency of entire males compared to castrates, the observed high androstenone levels represent a major challenge to implement entire males production.

Pig meat quality from entire males

This paper constitutes an updated review of the production and meat quality aspects of rearing entire male pigs. Since a major obstacle in rearing entire males is the incidence of boar taint, possible methods for detection are also summarised. Safe and fast methods for detection of boar taint would be valuable in avoiding complaints from consumers. Pig meat quality is determined by many aspects, among which odour and taste are the most important attributes. Odour may be negatively affected by the presence of a pheromonal steroid, androstenone, and a fermentation product of l-tryptophan, skatole. Male pigs are surgically castrated in many countries to minimise the risk of accumulation of high levels of androstenone and skatole. Raising entire male pigs is more profitable because they have superior production characteristics and improved meat quality due to leaner carcasses and higher protein content, as compared to castrated pigs. Furthermore, surgical castration is negative from an animal welfare point of view. In most studies, no differences in sensory quality have been found between lean meat from entire male pigs with low levels of androstenone and skatole and pork from castrates and females. The question that remains is: which substances are responsible for boar taint besides androstenone and skatole and whether they need to be considered? The threshold values used for androstenone and skatole might also be too high for highly sensitive persons. Recent research shows that a human odorant receptor, ORD7D4, is involved in sensitivity to androstenone. If the ORD7D4 genotypes of consumer and expert panels are known, this might facilitate consumer studies in the future. There is still a great need for rapid on/at-line detection methods in abattoirs for identifying carcasses with unacceptable levels of boar taint compounds. Several emerging rapid technologies with a potential for boar taint detection have been investigated. They represent various measurement principles such as chemical sensor arrays (electronic noses), mass-spectrometry fingerprinting, ultra-fast gas chromatography, gas-phase spectrometry and biosensors. An industrial detection method should allow 100% correct classification of both acceptable and not-acceptable samples with regard to boar taint sorting criteria. There are, however, still too high a percentage of false negatives ranging from 5% to 20%. In addition, these methods do not yet seem to fulfil the industrial specifications with regard to cost efficiency, simplicity and analysis time. There is still no dedicated measurement technology available for on/at-line detection of boar-tainted carcasses that measures both androstenone and skatole.

Differential effects of natural palm oil, chemically- and enzymatically-modified palm oil on weight gain, blood lipid metabolites and fat deposition in a pediatric pig model

BACKGROUND

Increasing prevalence of obesity and overweight in the Western world, continue to be a major health threat and is responsible for increased health care costs. Dietary intervention studies show a strong positive association between saturated fat intake and the development of obesity and cardiovascular disease. This study investigated the effect of positional distribution of palmitic acid (Sn-1, 2 & 3) of palm oil on cardiovascular health and development of obesity, using weaner pigs as a model for young children.

METHODS

Male and female weaner piglets were randomly allocated to 4 dietary treatment groups: 1) pork lard (LRD); 2) natural palm olein (NPO); 3) chemically inter-esterified PO (CPO) and 4) enzymatically inter-esterified PO (EnPO) as the fat source. Diets were formulated with 11% lard or with palm olein in order to provide 31% of digestible energy from fat in the diet and were balanced for cholesterol, protein and energy across treatments.

RESULTS

From 8 weeks onwards, pigs on EnPO diet gained (P<0.05) more weight than all other groups. Feed conversion efficiency (feed to gain) over the 12 week experimental period did not vary between treatment groups. Plasma LDL-C content and LDL-C/HDL-C ratio in pigs fed natural PO tended to be lower compared to all other diets. The natural PO lowered (P<0.02) the plasma triglyceride (TG) content relative to the lard or EnPO diets, but was not different from the CPO diet. The natural PO diet was associated with lower (P<0.05) saturated fat levels in subcutaneous adipose tissue than the CPO and EnPO diets that had lower saturated fat levels than the lard diet. Female pigs had lower lean and higher fat and fat:lean ratio in the body compared with male pigs. No difference in weight gain or blood lipid parameters was observed between sexes.

CONCLUSIONS

The observations on plasma TG, muscle and adipose tissue saturated fatty acid contents and back fat (subcutaneous) thickness suggest that natural palm oil may reduce deposition of body fat. In addition, dietary supplementation with natural palm oil containing palmitic acid at different positions in meat producing animals may lead to the production of meat and meat products with lower saturated fats. An increase in fat content and a decrease in lean content in female pigs resulted in an increased body fat:lean ratio but gender had no effect on blood lipid parameters or insulin concentrations.

Reducing the length of time between slaughter and the secondary gonadotropin-releasing factor immunization improves growth performance and clears boar taint compounds in male finishing pigs

The objective of this study was to evaluate whether altering the timing of the secondary anti-gonadotropin-releasing factor (GnRF) immunization closer to slaughter in male finishing pigs would reduce the increase in P2 fat depth (6.5 cm from the midline over the last rib), while still limiting the incidence of boar taint. Entire male pigs are immunized against GnRF to reduce the concentration of testicular steroids that in turn limits the incidence of boar taint. Additionally, testicle measurements and color measurements were taken to examine whether they could be used to differentiate nonimmunized entire males from immunized male pigs. A total of 175 Large White × Landrace entire male pigs aged 16 wk (59 kg of BW) were used in a completely randomized design with 5 treatment groups based on the time that pigs received the secondary immunization before slaughter. Pigs were housed in groups of 7 and randomly allocated to 1 of 5 treatments with 5 replicates per treatment. The treatment groups were as follows: no secondary immunization before slaughter, and the secondary immunization given at 2, 3, 4, or 6 wk before slaughter. The P2 fat depth levels were reduced (P = 0.054) with the secondary immunization closer to slaughter (11.7, 11.3, 12.8, 12.6, and 13.7 mm for no secondary immunization, secondary immunization at 2, 3, 4, and 6 wk before slaughter, respectively). Androstenone concentration did not exceed the generally accepted industry sensory threshold of 1.0 µg/g of fat, and both androstenone concentration in the adipose tissue and testosterone concentrations in the blood were suppressed (P < 0.001) in all immunized pigs regardless of timing of the secondary immunization compared with pigs that did not receive the secondary immunization. Skatole concentration of all pigs in the experiment did not exceed the generally accepted industry sensory threshold of 0.2 µg/g. Testes weight was reduced (P < 0.001) with increased time between slaughter and the secondary immunization. Immunized pigs, regardless of time before slaughter, had greater L* (lightness) and b* (yellowness) color of the testicle surface (P < 0.001 and P = 0.020, respectively), and less a* (redness) color compared with entire males (P < 0.001). The study provides further evidence of the efficacy of the anti-GnRF immunization and indicates that the secondary immunization can be moved closer to slaughter, while still limiting the incidence of boar taint. Testicle measurements and color measurements together could provide a method of discrimination between carcasses from immunized entire males clear of boar taint and tainted carcasses.

Immunisation against gonadotrophin-releasing hormone (GnRH) increases growth and reduces variability in group-housed boars

It is generally accepted that entire boars are leaner and more efficient than barrows but that they have poorer meat quality with an increased risk of boar taint. An additional issue in producing boars to meet market specifications is variation in growth performance, which may be exacerbated by high levels of aggression and mounting behaviour in group-housed animals. Immunisation against gonadotrophin-releasing hormone (GnRH), leading to immunological castration, offers a means of reducing aggression and mounting behaviour while maintaining most of the production efficiencies associated with entire boars. A total of 120 control boars, 120 immunised boars and 60 barrows (physically castrated at 5 days of age) were used in a study conducted in two replicates. Each replicate consisted of two pens each of boars, immunised boars and barrows, each pen containing 15 pigs, and two blocks of 15 individually-housed boars and immunised boars. The group-housed pigs had access to two single place electronic feeders per pen. Immunised boars were given the anti-GnRH vaccine (Improvac) at 14 and 18 weeks of age. In the 2 weeks immediately after the secondary immunisation at 18 weeks, average daily gain was greater in the immunised boars than the boars or barrows, particularly in those that were group housed, as indicated by the interaction (P = 0.035). From 18 to 23 weeks of age average daily gain was greater (P = 0.005) in immunised boars than in control boars and barrows and was greater (P < 0.001) in individually- than in group-housed pigs. The average daily gain of group-housed immunised boars and individually-housed control boars were similar over the 5-week period after secondary immunisation (1090 vs 1099 g/day), being ~20 and 15% higher than the group-housed control boars and barrows, respectively. The average daily feed intake was greater (P = 0.011) in immunised boars than in control boars with barrows intermediate. The standard deviation of bodyweight increased with age but was lower (P from 0.032 to 0.09) in immunised boars than in control boars and barrows between 18 and 22 and 17 and 21 weeks of age. Carcass fighting damage and pork pH were higher (P < 0.05) for control boars than for immunised boars or barrows. In conclusion, immunisation against GnRH increased average daily gain and average daily feed intake while decreasing variation in bodyweight and improving carcass and pork quality.

Temporal growth and development of body tissues of pigs as assessed by X-ray computed tomography

Data from 54 hybrid (mainly Large White × Landrace) pigs, comprising 18 male, 18 female and 18 castrated pigs, were used to quantify and mathematically describe the temporal growth and development of body tissues of live pigs. The pigs were 31.1 ± 3.6 kg liveweight (LW) and 70 ± 1 day of age (mean ± s.d.) at the start of the study, were individually penned, fed ad libitum and were weighed weekly. Computed tomography (CT) imaging was used to determine the weights of lean, fat and bone tissues of each pig at five different times during the study, which corresponded to ~30, 60, 90, 120 and 150 kg LW. The highest age and LW achieved by a pig were 31.4 weeks and 166.6 kg, respectively. A nonlinear mixed effects model of Gompertz function with sigmoidal behaviour was fitted to the data for each of the three sexes (male, female and castrate) to study the temporal growth and development of CT LW and the body tissues (lean, fat and bone). The estimate for CT LW at maturity was 237.5, 198.6 and 210.1 kg for males, females and castrates, respectively, and the corresponding prediction for the point of inflection (maximum growth rate) was 87.4, 73.1 and 77.3 kg. The predicted point of inflection for lean tissue was 47.0, 37.5 and 34.3 kg for males, females and castrates, respectively. In general, male pigs were the leanest, and castrates were the fattest, with females in between. Within sex, the ages at the point of inflection for lean tissue and bone tissue were lower than those for CT LW, whereas those for fat tissue were higher than those for CT LW. The percentage of bone tissue in the body generally remained stable with age (e.g. castrates had 9.2 and 9.0% at 14 and 26 weeks of age, respectively), whereas the percentage of lean tissue decreased with age (e.g. castrates had 61.3 and 50.4% at 14 and 26 weeks of age, respectively), and that of fat tissue increased with age (e.g. castrates had 16.8 and 25.8% at 14 and 26 weeks of age, respectively). Accurate mathematical models are required to develop management strategies to optimise pig production. The results of this study indicate that serial data on live pigs generated by CT imaging technology can be used to describe temporal growth and development of LW and body tissues of pigs using sigmoidal growth functions.