Chronic intermittent stress exposure and access to grass silage interact differently in their effect on behaviour, gastric health and stress physiology of entire or castrated male growing-finishing pigs

Castration and alternatives in pig: advantages and disadvantages

Sixty entire male pigs (Large White × Landrace × Duroc crossbred) were individually reared from 45 to 114 kg liveweight in a 2 by 3 factorial experiment to determine the interactive effects of sex (entire male pigs v. male pigs immunologically castrated using Improvac with vaccinations administered at 13 weeks of age and 5 weeks before slaughter) and a ractopamine feeding program (constantly fed 0 or 5 ppm ractopamine for 26 days before slaughter v. a step-up program where 5 ppm of ractopamine was fed for 14 days followed by 10 ppm ractopamine for the final 12 days before slaughter) on growth performance, carcass composition and pork quality. Following the second vaccination, immunocastrated pigs ate more (P < 0.001) and grew faster (P < 0.05) than entire male pigs without affecting feed conversion efficiency. Dietary ractopamine supplementation for the last 26 days before slaughter improved feed conversion ratio (P = 0.024) and daily gain (P = 0.046). Dietary ractopamine supplementation also increased carcass total tissue (P = 0.023) and total lean (P = 0.027) content without affecting the objective meat quality (P > 0.05) in both entire and immunocastrated male pigs. The effects of dietary ractopamine and immunocastration were additive, such that pigs that were immunocastrated and received ractopamine grew 18% faster than control entire males. However, a step-up program of ractopamine supplementation did not provide further improvements in growth performance and carcass composition when compared with constant 5 ppm ractopamine supplementation. These findings indicate that ractopamine supplementation improved growth performance in entire and immunocastrated male pigs, thereby offering a means of improving growth performance of entire males without detrimental effects on pork quality.

ABSTRACTTo avoid boar taint before slaughtering, late castration by immunisation against gonadotrophin releasing hormone or immunocastration has been developed. The current study aimed at determining whether differences in feed efficiency between castrated male (CM), immune castrated (IM) and entire male pigs (EM) can be explained by differences in nutrient plasma profiles after a meal. In this study, 24 male pigs (n = 8/type) were enrolled between 14 to 19 weeks of age. Entire and IM pigs ate less and were more feed efficient than CM pigs (p < 0.05). The postprandial plasma profiles of glucose, insulin, urea and amino acids (AA) were determined before (d –6), just after (d 8) and well after (d 16) the decrease in testicular hormones in IM pigs. For each test day, pigs were fasted overnight and subsequently fed a small meal (400 g). On d –6, postprandial profiles of plasma glucose of IM pigs did not differ from the two other types of pigs. On d 8, EM pigs had a greater average plasma glucose concentration than IM and CM pigs (p < 0.05) but the profiles did not differ. On d 16, the differences between profiles of glucose suggest a lower clearance of glucose in EM compared with IM and CM pigs. Plasma insulin did not significantly differ between the three types. Plasma urea profiles did not differ between CM, EM and IC pigs on d –6 whereas CM pigs showed higher plasma urea concentrations than EM and IM thereafter (p < 0.01). Among AA, Lys plasma concentrations were greater in CM than in EM and IM pigs on d –6, d 8 and d 16 (p < 0.05), whereas on d 16 plasma Hypro concentrations were lower in CM than in EM and IM pigs (p < 0.05). The finding that plasma glucose profiles were modified by immunocastration much faster and earlier than urea and AA profiles, suggest that the decrease in testicular hormones impacted energy metabolism more rapidly than protein metabolism.

The aim of our study was to investigate the effect of rearing system (mixed or single-sex) on performance and carcass quality of entire male and female pigs slaughtered at around 90 or 115 kg live weight. We also studied the combined effect of live weight and dietary supplement of raw potato starch (RPS) on technological meat quality for both sexes, and boar taint compounds in entire male pigs. Furthermore, we investigated pre-slaughter routines (pen-wise or mixing with unfamiliar pigs) and sexual maturity. A total of 408 growing/finishing pigs were included in this two-year study. Performance did not differ significantly between entire male and female pigs irrespective of rearing system, except for daily weight gain in the interval from 90 kg to slaughter. Mixed pigs had significantly higher daily weight gain in this interval than single-sex pigs. Entire male pigs had higher carcass lean meat content than female pigs (1.6 percentage units). Technological meat quality differed only slightly between the sexes. Females reared in mixed pens were sexually more mature than female pigs reared in single-sex pens, and mature females had higher growth rate but lower meat content in carcasses than immature females. In contrast, female contact did not influence sexual maturity of entire male pigs. Mixing entire male pigs with unfamiliar pigs at the abattoir resulted in more damaged skin compared with pen-wise keeping whereas female pigs had almost no visible skin damage. We therefore recommend that entire male pigs are not mixed with unfamiliar pigs during transport and at the abattoir, because of fighting and subsequent skin damage. The levels of skatole in fat were significantly lower in high-weight entire male pigs fed RPS compared to high-weight pigs without RPS. Androstenone levels in fat were high in all groups.

The effect of antemortem handling on behaviour, carcass yield and lean meat quality was determined on Lacombe and Yorkshire entire male pigs mixed within breed 24 h prior to slaughter and on entire males and gilts that were not mixed. In the period immediately after repenning (mixing), 40% of all recorded pen activity was observed, while 17% and 10% of the pen activities were recorded at 6 and 12 h after repenning. During the period immediately after transport to the abattoir, 33% of all pen activities were observed. Mixed pigs accounted for 78% of all activity. Yorkshire male pigs were three times as active as Lacombe male pigs during shipping. Thirty-six percent and 14% of the mixed Yorkshire and Lacombe male pigs had moderate skin blemishes, compared with 12% for unmixed Yorkshire male pigs. Moderate skin blemishes were absent in the unmixed Lacombe male and all female pigs. Dressing percentage and carcass shrinkage were unaffected by mixing during shipping. Dressing percentage was 23 g kg−1 higher in female than in male pigs, while male pigs had 20 g kg−1 greater lean than female pigs. Ultimate pH (48 h) was similar among unmixed pigs (5.53), but higher in mixed Lacombe (5.61) and Yorkshire (5.74) entire male pigs. Based on subjective meat quality evaluation, firm and dry pork was observed in 11% and 43% of the mixed Lacombe and Yorkshire male pigs, but was absent in unmixed male pigs. However, no consistent objective meat quality differences between unmixed male and female pigs were observed. Unmixed entire male pigs had superior carcass composition characteristics, with lean meat quality attributes at least equivalent to those of female pigs (e. g. pH, drip loss, CIE L*, hue angle). Mixing entire male pigs prior to slaughter had marginal but significant effects on carcass blemish scores and meat quality, particularly among Yorkshire pigs. This study suggests entire males, with appropriate antemortem handling, can produce superior carcasses, more efficiently and with pork quality at least equivalent to that of female pigs. Key words: Swine, behaviour, mixing, entire males, carcass yield, meat quality

Long-term effects of castration, chronic intermittent social stress, provision of grass silage and their interactions on performance and meat and adipose tissue properties in growing-finishing pigs

Abstract. The aim of the present research was to study the chemical composition, technological traits and intensity of boar taint of meat in entire male (EM) and surgically castrated male (CM) pigs. The study included 46 male pigs, cross F1 (Landrace x Danube White), fattened to average live weight 90 kg. In terms of chemical composition, the higher water and lipid content of the meat of entire male pigs, compared to the meat of surgically castrated male pigs was not statistically significant. A significant difference in the meat’s technological traits – pH values, water-holding capacity, cooking losses and tenderness between the two groups of male animals ware not found. The influence of the factor “castration” was reported in trait marbling of meat (p&lt;0.001). There were statistically significant differences in the values of L*, b* and Hue angle, defining the color characteristics of the meat.

The objective of this experiment was to determine if increasing lysine in the diets of immunologically castrated (IC) male pigs would increase percentage fat free lean and carcass cutting yields when compared with physical castrates. The anti-gonadotropin-releasing factor (GnRF) immunological product (Improvest, Pfizer Animal Health) is used worldwide to immunologically castrate entire male pigs to control boar taint and take advantage of the inherent ability of the entire male to deposit more muscle, less fat, and grow more efficiently than physically castrated males. The immunization process essentially allows the pig to grow as an entire male pig for most of its life and then removes any boar odor (boar taint) before slaughter. Reported lean meat advantages may also provide economic benefits to the domestic meat industry. Approximately 1,200 male pigs [physical castrates, IC males, and entire males] were each assigned to 1 of 4 diet programs which differed in lysine content. In each case, lysine was fed in a conventional step-down program that culminated with the following concentrations in the late finishing diet: physical castrates fed low lysine (0.7%), IC fed low lysine (0.7%), IC fed low/medium lysine (0.8%), IC fed medium/high lysine (0.9%), IC fed high lysine (1.0%), and entire males fed high lysine (1.0%). At 25 wk of age (5 wk post-second injection), pigs were individually weighed and the 2 pigs (n=96) in each pen closest to the median pig BW were selected and slaughtered. The right side of each carcass was dissected into soft tissue, skin, and bone. Proximate composition was determined on the soft tissue to determine percentage fat-free lean. The left side of each carcass was weighed and initially fabricated into ham, loin, belly, and whole shoulder. Each primal piece was weighed again and further fabricated into respective subprimal cuts. Immunological castration did not change (P>0.05) shear force values or ultimate pH when compared with either physical castrates or entire males. Marbling appeared to decrease as dietary lysine was increased among IC males. As expected, IC males had a greater (P<0.05) percentage fat-free lean than physical castrates but less (P<0.05) than entire males. Immunologically castrated males fed diets with medium/high and high lysine had greater (P<0.05) lean cutting yields and carcass cutting yields than physical castrates. Lean cutting yield and carcass cutting yields appeared to increase as dietary lysine was increased among IC males. Overall, immunological castration improved carcass cutability, increased percentage fat free lean, and had no effect on pork quality when compared with physical castrates.

Influence of chicory roots (<i>Cichorium intybus</i>L<i>)</i>on boar taint in entire male and female pigs

The effects of immuno- and surgical-castration on the behaviour and consequently growth of group-housed, male finisher pigs

Expression and activities of hepatic cytochrome P450 (CYP1A, CYP2A and CYP2E1) in entire and castrated male pigs

In the first chapter, the objective was to determine the metabolizable and net energy requirements for maintenance and production of entire males and immunocastrated males from 70 to 130 kg of body weight, using the factorial method. Sixty entire male pigs were randomly assigned to a performance trial with four treatments (ad libitum, 75%, 50%, and 25% of the ad libitum feed), with 12 replicates and one pig per pen. The parameters of the energy model were established using the comparative method for protein and fat deposition through the Dual-Energy X-ray Absorptiometry (DEXA) approach. Energy requirements for weight gain were determined based on body energy content and the efficiency of energy utilization for weight gain. Metabolizable energy (ME) and net energy (NE) requirements for maintenance (MEm and NEm) were 160.33 and 134.52 kcal/kg BW0.75 per day, respectively, for entire males. The efficiency of utilization of ME for NE was 0.84, estimated from the slope of the linear regression equation of retained energy as a function of metabolizable energy (ME) intake. The ratio of lean to fat mass decreased during the growth period and was more pronounced in immunocastrated males, indicating that fat retention becomes more energy-efficient as body weight increases. Entire male pigs are less demanding in net energy for gain (NEg) than immunocastrated males. The ME and NE requirements for production (MEp and NEp) were 4.498 and 3.779 kcal per kilogram of body weight for entire males, and 5.298 and 4.451 kcal for immunocastrated males, respectively. The second chapter evaluated digestible lysine (DLys) levels in the diet of immunocastrated male pigs during the finishing phase regarding performance, in vivo body composition, carcass traits, and meat quality, as well as to determine DLys requirements. Sixty immunocastrated male pigs were randomly allotted to five treatments with DLys levels of 0.55, 0.61, 0.68, 0.75, and 0.82%, respectively, in 12 replicates. Overall, performance improved in response to increasing DLys levels. Carcass yield and loin weight increased linearly (P &lt; 0.05) with increasing DLys levels, whereas loin area (LA) showed a quadratic increase (P &lt; 0.05). Meat quality was affected, showing a linear increase in sarcomere length, drip loss (P &lt; 0.10), and color values a* and b* (P &lt; 0.05), as well as changes in the chemical composition of loin chops, with a quadratic decrease for intramuscular fat and crude protein in dry matter (P&lt; 0.05). Body composition was affected, with a linear increase in fat mass gain and a quadratic increase in bone mineral content (BMC) gain (P &lt; 0.05); however, only total body fat gain increased significantly. The DLys requirement was estimated at 0.74% for carcass parameters (carcass yield and loin weight) using the quadratic model, and for ADG using the linear-plateau model. A daily intake of 33 g DLys/day for 1.79 kg/day of ADG, or 17.90 g DLys per kg of body weight gain, is recommended for immunocastrated male pigs housed individually during the finishing phase. Keywords: nutritional requirements; body composition; DEXA; factorial method.

The effect of immunization against gonadotropin-releasing factor on growth performance, carcass characteristics and boar taint relevant to pig producers and the pork packing industry: A meta-analysis

The aim of this study was to evaluate growth performance, carcass and meat composition of T1) gilts, T2) barrows, T3) immunocastrated (IMC) and T4) entire male (EM) pigs. Twenty eight individually allocated Yorkshire-Landrace x Duroc-Pietrain pigs (68.8 ± 1.2 kg initial BW) were fed a sorghum-soybean meal-based diet (18.4% PC, 3.4 Mcal ME/kg), and water ad libitum. The IMC received two 2-mL subcutaneous injections of an antiGnRH immunological product (Improvac; Zoetis, Mexico) at 115 and 145 days of age. Body weight (BW), ADG, Feed Intake (ADFI), Feed efficiency (G:F) and hot carcass weight (HCW) were registered. Serum testosterone (TEST) was analyzed in blood samples taken at days 115, and 145 of age, and at slaughter, using a commercial ELISA kit (Mexlab, Mexico). Testicles and bulbourethral glands of IMC and EM pigs were weighed. Protein and fat contents were determined (AOAC, 2005) in Longissimus dorsi muscle (LM). Data were analyzed in a randomized block design with two blocks of contemporary pigs utilizing SPSS (v21), and means were compared with Tukey test (P < 0.05). ADFI was similar (P > 0.05) among treatments. Gilts had lower final BW (P < 0.05) than others (121.6 vs. 134.4 kg). IMC and EM had higher (P < 0.05) ADG (0.984 vs. 0.855 kg/d) and G:F (0.208 vs. 0.178 kg/kg) than gilts and barrows. TEST of gilts and barrows remained under 0.1 ng/mL (P < 0.05). At slaughter, IMC had less (P < 0.001) TEST (0.2 vs. 6.8 ng/mL), smaller testicles (0.276 vs. 0.702 kg; P < 0.002), and bulbourethral glands (0.075 vs. 0.202 kg; P < 0.002) than EM. Gilts had less HCW (P < 0.01) than others (99.6 vs. 109.7 kg). LM fat (2.80 ± 0.16%) and protein (22.6 ± 0.37%) content was similar (P > 0.05) among gender. In conclusion, immunologically castrated pigs had better ADG and G:F than barrows and gilts, however lower serum testosterone concentrations than EM pigs.

Simple SummaryRaising entire male pigs and immunocastrates poses various challenges on how the nutrient requirements of these growth-efficient animals can be met. Applying the appropriate nutritional strategy will markedly affect the production efficiency and the carcass and pork quality, but will also control the incidence of boar-tainted carcasses. This paper reviews the current knowledge on the nutritional requirements of entire male and immunocastrated pigs to obtain an efficient growth, low boar taint level, and good carcass and meat quality. We present the reasons for offering entire males ad libitum access to the diets in order to optimize their protein deposition potential. Boar taint is one of the major issues in the production of entire males; therefore, the impact of various skatole- and indole-reducing feed ingredients is discussed regarding their efficiency and the possible mechanism affecting skatole and indole production in the hindgut. Entire males have lean carcasses, so their intramuscular fat content can be lower than that of surgical castrates or females and the adipose tissue can be highly unsaturated. The possible nutritional strategies to counteract these effects are summarized. We conclude that immunocastrates can be fed similarly to entire males until the second vaccination. However, due to the metabolic changes occurring shortly after the second vaccination, the requirements for essential amino acids are markedly lower in immunocastrates than in entire males.