Our aim was to evaluate the effects of single or mixed sex fattening of boars and split marketing (SM) on pig welfare. Female (n = 10), male (n = 10) and mixed sex (n = 10) groups were fattened to 105 kg. Two focal pigs per pen were selected for continuous behaviour observations and skin lesion inspections. Aggressive and sexual behaviours were recorded during feeding. One week prior to slaughter the three heaviest pigs in half of the pens were marketed. There was more sexual behaviour in mixed and male groups. However, there was less agonistic behaviour in mixed and female compared to male groups. SM male groups tended to have higher lesion scores than non-SM male groups. There was more mounting in non-SM mixed groups than in both SM and non-SM female groups. The welfare of boars was improved in mixed sex groups but females fared better in single sex groups. Split marketing reduced the welfare of pigs in male groups but improved pig welfare in mixed groups.

Pigs subjected to heat stress (HS) decrease their feed intake and growth. The objectives of the experiment were to determine the effects of live yeast (LY) supplementation (Saccharomyces cerevisiae var boulardii CNCM I-1079) on feeding behaviour, energy metabolism and faecal microbiota composition of finishing boars (n 10) housed in a respiration chamber at thermoneutrality (7 d at 22°C) or during HS (seven plus six days at 28°C). Dietary LY supplementation increased DM intake (P = 0·01) whatever the ambient temperature, whereas HS decreased feed intake whatever the dietary supplementation (P = 0·01). Dietary LY supplementation increased the number of meals (P = 0·02). Energy retention was higher with dietary LY supplementation (P < 0·01) but decreased during HS (P < 0·01). The skin temperature of the supplemented pigs was lower at thermoneutrality and increased during HS to a lesser extent than that of non-supplemented pigs (P < 0·01). Faecal microbiota composition was determined using 16S rRNA gene sequencing. Treponema, Christensenellaceae R-7, Ruminococcaceae UCG-002, Rikenellaceae RC9, Clostridium sensu stricto 1 and Romboutsia genera and some bacteria belonging to Alloprevotella, Oxalobacter and Anaeroplasma genera were more abundant under HS. LY supplementation attenuated HS effects on Romboutsia abundance, while decreasing the abundance of some bacteria from Ruminoccocus, Coprococcus, Peptococcus and Oxalobacter genera and increasing the abundance of beneficial bacteria from Lactococcus and Subdoligranulum genera. Our results suggest that higher level of the keystone species Ruminococcus bromii at thermoneutrality may be one of the causes for higher energy retention observed under subsequent HS.

Immunocastration or vaccination against boar taint can be used as alternative for surgical castration of male piglets. The vaccine is administrated twice. After the second vaccination (V2), the pigs behave like barrows instead of boars and their feed intake increases which may result in a lower lean meat percentage. The timing of V2 is therefore crucial to find the right balance between the advantages of entire males and barrows. In this study, we evaluated the effect of time post second injection within the advised time frame (4 v. 6 weeks before slaughter) on behaviour, performance, carcass and meat quality of immunocastrated male pigs. In total, 180 animals (hybrid sow×Piétrain): 60 gilts, 60 male pigs vaccinated 6 weeks before slaughter (IM-6) and 60 male pigs vaccinated 4 weeks before slaughter (IM-4), all slaughtered at comparable slaughter weights. After 20 weeks of age, IM-6 showed more inactive behaviour at the expense of playing and aggressive behaviour. Daily feed intake (DFI), daily gain (DG) and feed conversion ratio (FCR) did not differ significantly between IM-6 and IM-4. Gilts had a lower DFI and DG in the late finishing phase and a higher FCR overall compared with both IM groups. Gilts showed a higher lean meat content compared with both IM groups. Earlier vaccination increased dressing percentage, which could partly be explained by the lower weight of the gastrointestinal tract, but not by testes weight. Meat quality traits and palatability did not differ significantly between IM-6 and IM-4. Vaccination of immunocastrates at 6 compared with 4 weeks before slaughter improved the calmness in the stable and the dressing percentage, while maintaining performance and carcass characteristics.

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.

Porcine circovirus type 2 (PCV2) causes great economic losses in growing pigs and there are several reviews on disease manifestations and lesions associated with PCV2 in growing pigs. Reproductive failure in breeding herds, predominately associated with increased numbers of mummies and non-viable piglets at parturition, is one of the disease manifestations of PCV2 infection. Boars shed low amounts of infectious PCV2 in semen for extended time periods, and vertical transmission of PCV2 to fetuses during PCV2 viremia of the dam has been experimentally confirmed. However, intrauterine-infected piglets often are clinically normal. Nevertheless, pigs infected with PCV2 by the intrauterine route can be born viremic, possibly contributing to horizontal spread of PCV2 within the breeding herd and into the nursery. Shedding of PCV2 in semen and prevalence of intrauterine-infected piglets can both be greatly reduced by PCV2 vaccination well ahead of expected PCV2 exposure. This review is a discussion on current knowledge on the effects of PCV2 infection in the dam and in in utero fetuses, including clinical signs, lesions, diagnosis and prevention through vaccination. Infection of boars with PCV2, the potential for PCV2 transmission via semen and prevention of PCV2 shedding are also discussed.

With the ongoing social pressure on surgical castration of pigs, an increase in the population of pigs that are either not castrated or immunocastrated (IC) can be expected. In both cases, their nutrient requirements and performance will differ from surgically castrated pigs and will require changes in their management. Immunocastration is performed by giving two injections of a modified gonadotrophin-releasing hormone component along with an adjuvant, at least 4 weeks apart. This paper describes the reported differences in growth performance and carcass quality of IC male pigs in comparison with boars (BO) and barrows (BA). Theoretically, IC pigs remain physiologically boar until the second vaccination and therefore, growth may be comparable with BO until this second vaccination. From then on, IC male pigs consume more feed than BO and grow faster when fed ad libitum. IC showed a faster growth and better feed conversion ratio than BA. When fed restrictedly, BO grow faster and more efficiently than BA and IC. IC have a lower carcass yield than BA and BO, whereas meat percentage is intermediate.

Fumonisins, a group of toxic metabolites produced by the genus Fusarium, are known to be consumed by farm animals and are the causative agent or a suspected contributing factor in farm animal diseases. Pigs are particularly susceptible to fumonisins. Reproductive inefficiency is recognized as the most costly limiting constraint to efficient animal production. To account for potential reproductive effects of fumonisin in boars, dietary fumonisin B1 (FB1) was fed to 24 male Large White weanling pigs, 8 to 9 weeks of age. The animals were randomly assigned to four diets containing 5.0, 10.0, 15.0 and 0.2 mg FB1/kg constituting diets 1, 2, 3 and control diet, respectively. After 6 months, semen samples were collected from the pubertal boars and analysed. After the semen collection, all the pubertal boars were killed by decapitation, their reproductive systems dissected and the weights of the testes and epididymides as well as the volumes of the testes recorded. Dietary FB1 did not influence both the relative weights of the testes and epididymides as well as the volumes of the testes. Except for the semen volume and spermatozoa morphological abnormalities, all the semen characteristics studied decreased in a dose-dependent manner and the decrease was statistically significant (P < 0.05). The sperm concentration, total sperm and motile sperm per ejaculate of the animals on diet 3 were 83.3%, 79.1% and 59.6% of the controls, respectively. The dietary FB1 levels influenced the mass activities of the semen, which ranged from very turbulent motion for animals on the control diet to absence of wave motion for those on diet 3. The study revealed that male weanling pigs for breeding should not be exposed to dietary FB1 higher than 5 mg/kg for optimum reproductive performance. The results of this present study suggest that the recommendation of 10 mg/kg by the United States Food and Drug Administration as the maximum level of total dietary fumonisins was above the no-observable-effect level of dietary fumonisin for swine.

Boar and gilt pigs from three genotypes (with 0, 0·25 and 0·50 Duroc inclusion level) were reared from 30 to 90 kg live weight on seven feeding regimens which involved combinations of diet formulation and feeding level. A diet of conventional energy and protein level (CEP; 14·2 MJ/kg digestible energy, 205 g/kg crude protein, 10 g/kg lysine) and a diet of higher energy and lower protein (HELP; 14·7 M]/kg digestible energy, 166 g/kg crude protein, 7·0 g/kg lysine) were used. One treatment involved feeding the HELP diet ad libitum, with the other six treatments involving feeding the CEP diet ad libitum, restricted, or in combinations of ad libitum and restricted. A total of 721 animals comprising similar numbers of boars and gilts were used to estimate sex differences for growth performance, carcass and meat quality, and eating quality. Tissue growth rates were predicted from regression equations based on P2fat depths or ham-joint dissection, developed from subsamples of animals that were subjected to full-side dissection. Overall when compared with gilts, boars grew faster (838 v. 799 gtday, P < 0·001), had improved food conversion ratios (2·39 v.2-55, P < 0·001) but had similar daily food intakes and lean and subcutaneous fat growth rates. Lean tissue food conversions did not differ significantly between the sexes. Killing-out proportions were higher for gilts (0·766 v. 0·749 , P < 0·001), however P2 backfat thickness and lean proportions did not differ between the sexes. The firmness of the mid-back fat, assessed subjectively and using a penetrometer, was greater for gilts than for boars. The tenderness of pork loin chops, assessed by a trained sensory panel, was judged to be better for boars than for gilts but there was no sex difference in overall acceptability. The fat from boars had a higher level of abnormal odour and boar odour. There was a sex × dietary treatment interaction for boar odour with the HELP diet producing the highest levels and the biggest difference between the sexes for odour scores.

The effects of short-term exposure to high ambient temperatures on gas exchange, heat production (HE), respiration rate (RR) and rectal temperature were evaluated individually with boars of approximately 100 kg live weight. The boars were of different breeds with four of Yorkshire (YS), eight of Danish Landrace (DL), out of which three were found stress susceptible by the halothane test (DLH+), eight of Duroc (DR) and eight of Hampshire (HS) breeds. After 1 h rest in the respiration chamber at 17·0°C the gas exchange measurements started with al-h basal period at 17 °C, followed by 2h of heating during which temperature increased to 35·0 °C (period I) and then further to 39·7X1 (period II). Then cooling of the chamber started, and after 1 h (period III) temperature had decreased to 21·8°C, and after the 2nd h of cooling (period IV) temperature was 18·2 °C. The gas exchange was measured for each hour from 09.00 h (basal period) until 14.00 h (period IV). RR was recorded every 15 min. Rectal temperatures were measured when the animals were removed from the chamber. The gas exchange and HE increased slowly during period I but rapidly in period II, followed by decreasing values in the cooling periods. HS and DLH+ had considerably higher gas exchange and HE than other breeds in these two periods and the values remained high during period III. In period IV all breeds had gas exchange rates and HE below those of the basal period. RR increased slightly in period I and then a sharp increase followed during period II. Maximum RR was recorded in period III with an average of 183 breaths per min for all breeds. RR increased earlier and more steeply in HS and reached the highest mean value of 236 breaths per min. Four HS boars salivated heavily during heat stress and rectal temperatures of these animals were 39·7 °C when removed from the chamber compared with close to 39·0 °C for all other breeds. It was concluded that there were considerable breed differences in response to heat stress and that DLH+ and HS were more severely stressed than boars ofYS, DL and DR.

Semen collection from three boars was performed twice a week, and doses (100 ml each) of semen diluted with Beltsville Thaw Solution (BTS) extender were prepared containing 1 × 109, 3 × 109 and 5 × 109 spermatozoa. Diluted semen was then stored at 17°C for a maximum of 120 h. Percentage of motile spermatozoa (PMS) and type of spermatozoa motility (TSM) were determined by microscopic examinations performed at 24-h intervals, from zero time (beginning of storage at 17°C) up to 120 h of storage, and a sperm motility index (SMI) calculated. Sows (no. = 360) were divided into nine experimental groups (40 sows per group) and a combination of number of spermatozoa per dose and storage time was used for artificial insemination in each group. All the animals were inseminated twice at 12 and 36 h after detection of standing oestrus by a teaser boar. Return and farrowing data including litter size were recorded. PMS, TSM and SMI decreased significantly (P < 0·01) from 48 h up to 120 h of storage, this being more marked in semen doses of 5 × 109 spermatozoa. When semen stored for up to 24 h was used, no significant differences (P > 0·05) regarding return rates and farrowing rates were observed among the three groups inseminated with semen containing different numbers of spermatozoa per dose. Inseminations with semen doses of 1 × 109 and 3 × 109 spermatozoa stored for 48 to 72 h have significantly lower return rates (P < 0·05) and significantly higher farrowing rates (P < 0·05) than with doses of 5 × 109 spermatozoa. Inseminations with semen stored for more than 72 h gave relatively higher return rates and lower farrowing rates. Semen storage time and number of spermatozoa per dose appeared to reduce litter size only where semen doses of 5 X109 spermatozoa were inseminated after storage for more than 48 h.

Seven replicates of five littermate boar Landrace pigs were used to evaluate the effects of (a) reducing the food intake within the practical range or (b) reducing energy intake without reducing protein intake, between 33 and 90 kg live weight on growth, nitrogen balance and carcass characteristics. Three levels of food intake (ad libitum, 0·90 and 0·80 ad libitum) were used and the dietary protein contents ranged from 250 to 312 g crude protein per kg dry matter (DM) to equalize protein intake with reduced food intake. All the diets were of similar amino acid composition, and lysine per kg DM ranged from 14·3 to 17·9 g. The food was given twice daily. Balance trials were conducted at 45 and 65 kg live weight and all pigs were slaughtered at 90 kg live weight to assess carcass characteristics. Reducing food intake or only energy intake significantly reduced live-weight gain (P < 0·001). Reducing food intake decreased nitrogen retention (P < 0·01) during the 65-kg balance period. Reducing food intake had no effect on fat thickness measurements but measurements at shoulder (P < 0·001), mid back (P < 0·001), C(P< 0·01) and P2 (P < 0·05) decreased and lean: fat in rumpback increased (P < 0·05) when energy intake was reduced. The weights of small intestine (P < 0·001), large intestine (P < 0·05), liver (P < 0·05) and kidneys (P < 0·05) were significantly reduced as food intake was reduced. Energy is more limiting than protein when the intake of a diet providing for optimal growth of high potential boars is reduced between 33 and 90 kg live weight.

The effect of reducing energy intake within the practical range or reducing energy intake without reducing protein intake on chemical composition of gain, whole-body protein turn-over and energy metabolism was studied between 33 and 90 kg live weight with seven replicates of five littermate boar Landrace pigs. Three levels of food intake (ad libitum, 0·90 and 0·80 ad libitum) were used and the dietary protein contents ranged from 250 to 312 g crude protein (CP) per kg dry matter (DM) to equalize protein intake with reduced food intake. All the diets were of similar amino acid composition and were offered twice daily as pellets. There was no effect of dietary treatment on the DM, CP and fat contents (g/kg) of the empty body (EB), but fat content and fat: protein ratio in EB tended to decrease with reduction of food intake or energy intake. The relationship between energy intake and protein deposition was linear and the mean maximum protein retention was 187 g/day. Retention of DM (P < 0·001), protein (P < 0·001), fat (P < 0·001), energy (P < 0·001) and ash (P < 0·01) decreased linearly with reducing food intake or energy intake. The calculated residual heat production was 0·604 MJ metabolizable energy per kg M0·75 per day. The dietary treatments had no effects on composition of longissimus dorsi, fillet, liver, kidney, backfat or kidney fat. The nitrogen flux, nitrogen synthesis and breakdown tended to decrease with reduction in food intake or energy intake though the effects were not statistically significant. Nitrogen accretion decreased significantly (P < 0·05).

Two experiments were conducted each using one batch of six Landrace littermate, entire male, pedigree pigs in a Latin-square change-over study of the effects of energy intake on nitrogen and energy metabolism over the range 33 to 88 kg live weight. One animal from each litter was slaughtered at 33 kg body weight to obtain initial body composition data. Five feeding levels (80, 100, 120, 140 and 160g/kg M0·63) were used during five consecutive metabolism trials each of 11-days duration, excreta being collected during the last 7 days. The pigs were housed in individual metabolism cages and the diets were offered in liquid form (approx. 300 g dry matter (DM) per kg) twice daily at 09.00 and 16.00 h. Heat production was measured for 1 day during each balance period in an open-circuit respiration chamber. The average daily gain, nitrogen retention, heat production and energy retention increased linearly (P < 0·001) with increasing metabolizable energy (ME) intake. The relationship between energy intake and protein deposition was linear up to levels above the normal ad libitum consumption of energy. Protein deposition potential of these high genetic potential pigs was at least 200 g/day, and tended to be constant between 35 and 85 kg live weight. From the combined results of experiments 1 and 2, the energy requirement for maintenance was 0·982 MJ ME per kg M0·63 per day and the decrease in protein deposition was approximately 6 g/MJ reduction in ME within the range of practical energy intakes.

Genotype × environment interaction for age at puberty was evaluated using gilts from the Nebraska Gene Pool population derived from lines selected randomly (RS; no. = 48) or for seven generations for decreased age at puberty (AP; no. = 73). Age at puberty was evaluated in two environments: boar exposure for 15 min daily (BE) or no boar exposure (NBE). Pigs were randomly assigned to treatment and mixed into groups of 20 in pasture lots. Oestrous detection was initiated when the oldest gilt in a pen was 125 days of age. Blood samples were taken weekly and assayed for progesterone. Gilts were considered to have expressed oestrus if they exhibited lordosis or had consecutive weekly blood samples with progesterone values above 6·4 × 109 mol/1 (2 μ, g/l). Gilts were removed from the pen upon confirmation of puberty or at 250 days of age. Two gilts failed to reach puberty by 250 days so this value was assigned as their age at puberty. Least-squares analyses of variance were used to analyse the data. A model including line, sire within line, farrowing group, treatment and line × treatment interaction was fitted to the dependent variables age at puberty and percentage cycling by 185 days. Line and treatment each affected age at puberty (P < 0·05) but did not interact. Least-square mean ages at puberty were 154 (s.e. 4·5), 164 (s.e. 4·7), 164 (s.e. 6·1) and 179 (s.e. 5·9) days for AP-BE, AP-NBE, RS-BE and RS-NBE, respectively. Treatment affected percentage of gilts cycling by 185 days (P < 0·05). Least-square percentages were 91 (s.e. 6·9), 76 (s.e. 71), 84 (s.e. 9·2) and 65 (s.e. 8·9) % for AP-BE, AP-NBE, RS-BE and RS-NBE, respectively. These results indicate that expression of response to selection for decreased age at puberty in the gilt is not dependent on stimuli from the boar.

An experiment was conducted to study the effect of feeding level and semen collection frequency on semen quantity and quality of 62 Yorkshire boars at two artificial insemination centres during 10 successive periods of 2 weeks. The experiment had a 2 × 2 factorial design with two feeding levels (2·75 and 3·5 kg/day) and two semen collection frequencies (three and five times in 2 weeks).

In the first 2-week period boars on the high frequency semen collection scheme produced 94 × 109 sperm cells more than boars on the low scheme. In periods 2 to 10 the mean difference was only 18 × 109 sperm cells. Boars on the high feeding level produced 32 × 109 sperm cells more per 2-week period than the boars on the low feeding level (P < 0·05). Boars at the high collection frequency and the high feeding level tended to produce a higher number of sperm cells during periods 2 to 10 than the boars on the high semen collection frequency and the low feeding level (P > 0·05). No effects of food intake or semen collection frequency on semen quality were found.

The effects of dietary protein (151 to 282 g crude protein per kg dry matter (DM)) and lysine (8·5 to 16·4 g/kg DM) on the carcass composition and energy metabolism of entire male pigs, given food close to appetite, was studied from 33 to 88 kg. Four replicates (three Landrace and one Duroc) of four littermates were used. Energy and nitrogen (N) balances were conducted at approximately 35 to 43, 58 to 65 and 78 to 85 kg and body composition was determined at slaughter. There was no effect of dietary treatment on the crude protein content of the empty body (EBW) but the DM (P < 0·001), fat (P < 0·001) and ash (P < 0·05) proportions and fat: protein ratio in EBW (P < 0·01) increased with decreasing dietary protein level. The mean maximum protein retention was 183 g/day. Retention of protein (P < 0·05) and proportion of protein energy in the gain (P < 0·01) decreased linearly and fat retention (P < 0·001) and energy content of the gain (P < 001) increased with decreasing dietary protein. The N retention values calculated from balance data were proportionately 0·21 higher at high protein intakes (509 g/day) and 0·056 higher at low protein intakes (329 g/day) than the values obtained by slaughter. Using the ideal protein system the value for the efficiency of utilization of apparently digested ideal protein for protein deposition (a2) fell linearly (P < 0·001), based on the slaughter data, as dietary protein content increased. Heat production, calculated from slaughter data, was proportionately 0·07 higher than that measured by indirect calorimetry and 0·17 higher than the computed value for heat production using the standard values of energy costs for maintenance and for protein and fat deposition.

Six replicates (five Landrace and one Duroc) of four littermate entire male pigs were used to evaluate the effect of protein level in diets of constant amino acid composition on live-weight gain, efficiency of gain, nitrogen balance and carcass characteristics. The diet contents ranged from 151 to 282 g crude protein (CP) and 8·5 to 16·4 g lysine per kg dry matter (DM) and were studied over two live-weight ranges, 33 to 55 kg and 55 to 88 kg. All the diets had similar metabolizable energy (ME) values (15·0 MJ/kg DM). Pigs were given food twice daily to appetite. Sixteen pigs (four replicates) were used for metabolism trials at 35 to 43, 58 to 65 and 78 to 88 kg live weight and after attaining a live weight of 88 kg they were slaughtered to assess carcass characteristics. Between 33 and 55 kg live weight significantly linear improvements (P < 0·01) in the daily live-weight gain and in the ratio ME: live-weight gain were observed for daily intakes in excess of 300 g ideal protein and 21 g lysine (212 g CP and 12·5 g lysine per kg DM). Between 55 and 88 kg live weight, linear improvements in the same two variables were observed for daily intakes of 395 g ideal protein and 28 g lysine (212 g CP and 12·5 g lysine per kg DM). For the 33 to 88 kg live-weight period the average ME intake was 30 MJ/day and the predicted intakes for maximum growth and food conversion efficiency were in excess of 370 g ideal protein and 26 g lysine. Nitrogen retention improved significantly with increasing dietary crude protein content in all three balance periods. Fat thickness measurements decreased linearly (P < 0·05) and the proportions of lean and fat in rumpback increased and decreased respectively (P < 0·01) as the dietary protein level increased.