H. K. Andersson

Aggressive and sexual behaviour of growing and finishing pigs reared in groups, without castration

Abstract Aggressive and sexual behaviour in entire males and females were studied on 408 pigs. The sum of aggressive interactions in the pen during routine feeding (ALP) was lowest in single-sex pens with females. ALP was higher at 132 than at 155 days. High ALP correlated with high average growth rate. Aggressive interactions in a competition test (IA) increased after slaughter of the three fastest-growing pigs in a pen (at 155 days), although the slaughtered pigs had initiated the most IA earlier (at 132 days). Entire male pigs displayed more sexual behaviour (mounting) than females. In 15% of entire males and 6% of females there were health problems specifically involving lameness or injured legs or feet. Five entire males and one female were euthanized in response to lameness or leg fracture. The rearing of entire male pigs may cause welfare problems, given their higher levels of aggression and sexual behaviour.

Photoperiodic effects on pubertal maturation of spermatogenesis, pituitary responsiveness to exogenous GnRH, and expression of boar taint in crossbred boars

Forty-eight weaned, winter-born crossbred males (average age of 42 days) were exposed to either a natural photoperiod (January-June at 60 degrees N, Control) or one of two artificial photoperiods (1400 lx) in light-sealed rooms. The Spring/Summer group was exposed to an artificial photoperiod simulating conditions from the vernal equinox (mid-March) to August at 60 degrees N and the Autumn/Winter group to a photoperiod, simulating conditions from the autumnal equinox (mid-September) to February at 60 degrees N. Plasma samples were collected biweekly until the pigs were slaughtered, after reaching 115 kg, and analysed for testosterone, estrone sulfate, thyroxine and prolactin. Additionally, three animals per treatment (n = 9) were injected with gonadotropin-releasing hormone (GnRH) and plasma samples were collected every 15 min and analysed for luteinizing hormone and testosterone. Boar taint, carcass composition and reproductive traits were measured at slaughter. Live-weight gain from start to slaughter was lower among the Control animals compared with the Autumn/Winter and Spring/Summer animals. There was a peak in plasma testosterone in both the Spring/Summer and Autumn/Winter groups at 71 days of age, whereas plasma testosterone in the Control group remained at prepubertal levels. At 113 and 127 days of age, the Control group had somewhat higher testosterone levels than the Spring/Summer group, but at 141 days of age and on the day before slaughter, the Autumn/Winter group had a higher mean plasma testosterone concentration. There were no differences between treatments in the endocrine response to the GnRH challenge. Bulbourethral gland weight at slaughter was lower in the Spring/Summer group than in the Autumn/Winter group. The percentage of proximal cytoplasmic droplets was higher in the Spring/Summer group than in both the Control and Autumn/Winter groups. Spermatogenesis at the time of slaughter was clearly more mature in animals in the Autumn/Winter group than in those in the Spring/Summer and Control groups. Fat androstenone was lower in the Spring/Summer group than in the Control group. In the sensory evaluation, the Spring/Summer group had less boar taint than the Autumn/Winter group. Artificial short days with moderate initial changes in photoperiod, stimulated spermatogenesis compared with long days, in accordance with the pattern seen in European Wild Boars (Sus scrofa). Boar taint was also affected with higher scores in the Autumn/Winter group than in the Spring/Summer group, although this was not clearly indicated by the traditional measurements of boar taint-fat contents of androstenone and skatole.

Seasonal alterations in circadian melatonin rhythms of the European wild boar and domestic gilt.

The aims of the present study were: 1) to determine if the European wild boar exhibits a circadian pattern of melatonin secretion under its natural light environment; 2) to compare this pattern with the pattern in domestic pigs reared under the light environment typical for domesticity; and 3) to determine if there are seasonal alterations in melatonin rhythms. Four to six young, pure‐bred, European wild boars and four to six cross‐bred (Yorkshire×Finnish Landrace) domestic gilts were sampled at 2‐hr intervals for 48 hr at the spring/autumn equinoxes and summer/winter solstices. Samples were obtained via saphenous arterial catheters from the wild boars and via ear vein catheters from the domestic gilts. The ambient light intensity was recorded simultaneously with sampling both outdoors and indoors. Following ether extraction, the serum samples were assayed for melatonin using a commercial RIA (Bühlman®). All the experimental animals exhibited a distinct circadian pattern in melatonin secretion, with high concentrations occurring during the scotophase. There was no difference in scotophase melatonin response between the wild boars and domestic gilts in any season in terms of mean melatonin concentration or peak value. The mean duration of increased melatonin secretion (more than two standard deviations over a mean photophase concentration) in 24 hr in the wild boars in spring, summer, autumn and winter, was 10, 6, 11 and 17 hr, respectively, and in the domestic gilts, 9, 8, 12 and 11 hr, respectively. These results demonstrate the existence of circadian rhythm in melatonin secretion in both the European wild boar and domestic pig. In both groups, the duration of secretion is subject to seasonal alterations. The results suggest no difference in photoperiodic‐melatonin transduction between the European wild boar and domestic pig whether due to altered genotype or reduced light environment.

Production Results and Technological Meat Quality for Pigs in Indoor and Outdoor Rearing Systems

The objective of the study was to compare production results and technological meat quality for pigs born outdoors and reared indoors or outdoors during the summer period. A total of 279 pigs was reared in a large pen on deep litter, or outdoors. Daily weight gain and lean meat percentage were higher for pigs outdoors than indoors during year one (864 vs. 841g; 56.9 vs. 55.9%), but were similar for year two (859 vs. 844g; 55.9 vs. 55.6%). Outdoor pigs grew faster when fed ad libitum, but slower during the second phase when restricted, with inferior feed conversion. Most technological meat quality traits (surface and internal reflectance, marbling, pHBF, filter paper wetness, cooking loss and maximal Warner-Bratzler shear force) were similar between rearing systems, whereas pHLD was higher indoors. Total work of Warner-Bratzler shear force was lower in outdoor reared pigs. Maternal sire breed (Duroc or Landrace) and sex (castrate or gilt) did not notably affect meat quality traits. RN genotype had a stronger impact on meat quality than rearing system. It can be concluded from the similarities in production results and meat quality in both systems, that both indoor and outdoor rearing are good alternatives for summer rearing of pigs.

Influence of artificial light regimens on sexual maturation and boar taint in entire male pigs

To determine if artificial light regimens could influence sexual maturation and boar-taint factors in entire male pigs, 48 weaned, winter-born crossbred males (52-64 days old) were exposed to either a natural photoperiod (January-June, 60 degrees N, Control, n= 16) or to one of two artificial photoperiods (1400 1x) in light-sealed rooms. We exposed the Spring group to an increasing artificial photoperiod (January - June, 60 degrees N, n=16) and the Autumn group to a decreasing one (July-December, 60 degrees N, n = 16). Plasma samples were collected bi-weekly until the pigs were slaughtered, after reaching 115 kg. Boar taint, carcass composition and reproductive traits were measured at slaughter. Plasma testosterone increased earlier in the Autumn group than in the Control and Spring groups, but the difference was only transient. Estrone sulfate concentrations remained low in the Autumn group, whereas they increased in the Control and Spring groups, indicating a lack of synchrony between testicular androgen and estrogen production in the Autumn group. In the beginning of the study, when the Autumn group was subjected to long days, plasma prolactin was higher in the Autumn group than in the Spring group, but the relation was reversed 14 weeks later when the spring group was exposed to long days. Weight of reproductive organs (epididymidal weight and the total weight of the testes, epididymides and the bulbourethral glands relative to carcass weight) were lower in the Autumn and Spring groups than in the Control group. The Spring and Autumn groups had lower concentrations of skatole in fat compared with the Control group, whereas no clear difference was detected between groups in concentrations of androsterone in fat or in the sensory evaluation of boar taint. Estimated lean meat percentage was lower among animals in both the Autumn and Spring groups compared with the Control group. This study shows that photoperiod can influence male pubertal development and boar-taint factors in the domestic pig.

Effect of extra maternal feed supply in early gestation on sow and piglet performance and production and meat quality of growing/finishing pigs

The influence of differentiated extra maternal feed allowance during early gestation on maternal performance and postnatal development of the progeny from gilts and sows was investigated. Four different feed allowances of the same diet (Control [C], +35% [T35], +70% [T70], +100% [T100]) were assigned to 20 crossbred gilts (Swedish Landrace×Swedish Yorkshire), which continued as sows with the same feed allowance the following parity. The progeny was uniformly raised and slaughtered at a live weight of 110 kg. Additional maternal feed allowance resulted in significantly more weaned piglets per sow but not per gilt. Piglet numbers did not increase from T35 to T70/T100. Piglet birth weight did not increase due to maternal feeding. The intra-litter variation in piglet birth weights was similar between the treatments. Independent of the additional feed allowance, all gilts and sows had similar weights after weaning and had good body condition. The growth rate of progeny from sows was negatively related to maternal feed supply; for progeny from gilts, no clear trend of nutritional influence could be observed. Carcass and technological meat quality was not affected by maternal feeding treatment. Birth weight positively affected later growth performance (daily weight gain), carcass quality (lean meat content, back fat, proportion of muscles in ham/loin), whereas technological meat quality was unaffected.

The photophase light intensity does not affect the scotophase melatonin response in the domestic pig.

This study investigated the effects of the photophase light intensity on the scotophase melatonin response. Twelve, 8-month-old crossbred gilts were allocated to three groups of four and housed in temperature- and lighting-controlled climate rooms. The rooms had a light intensity of 40, 200 or 10,000 lx and a light-dark cycle of 12 L:12 D. The gilts were allowed to acclimatize to a new lighting regimen for 1 week before being sampled at 2h intervals for 24h. Following the sampling, pigs were transferred under a different light intensity, allowed to adjust for 1 week and sampled again. The procedure was repeated three times so that all the groups went through all three lighting regimens (light intensities). All the gilts exhibited a clear circadian serum melatonin rhythm under each lighting regimen with high melatonin concentrations occurring during the scotophase. There was no difference in the scotophase melatonin response in terms of mean concentrations or duration of increased melatonin levels within or between the groups under different lighting regimens. There was considerable inter-individual variation in the dark phase melatonin response but the individual profiles were consistent under the different lighting regimens. It is concluded that when a certain threshold light intensity (<40lx) is exceeded, the photophase light intensity has no effect on the scotophase melatonin response. These results imply that extremely high light intensities during the photophase would provide no additional benefits compared with normal comfortable light intensity, if artificial lighting programs were introduced to commercial piggeries in order to reduce seasonal effects on reproduction.

Carcass quality and technological and sensory meat quality of once-bred gilts in a seasonal outdoor rearing system

Seasonal application of once-bred gilts for piglet and meat production outdoors could be a worthwhile alternative rearing form to normal commercial production. Compared with growing/finishing pigs, payment for sow carcasses is considerably reduced because of an assumed decrease in meat quality and processing properties. The purpose of this study was to compare maiden and once-bred gilts for carcass quality, and technological and sensory meat quality. The control group of 14 gilts (LW*L and LW*D) was reared indoors and slaughtered unmated at an average live weight of 145 kg. In contrast, 38 once-bred gilts of the same breeds were initially reared like the maiden control, inseminated and then housed outdoors from one month before farrowing until slaughter. Carcass traits, technological meat quality (pH, internal and surface reflectance, water holding capacity, commercial processing yield (total yield) and laboratory processing yield (Napole yield), WB shear force and chemical composition of M. longissimus dorsi were measured. Sensory meat quality (taste panel) of oven-baked M. longissimus dorsi and cured and smoked M. semimembranosus et adductor was investigated. Carcass quality traits such as higher lean meat content and lower backfat thickness were preferable with the once-bred gilts. For technological meat quality characteristics, once-bred gilts had lower thawing loss, Napole yield, dry matter and higher total work of WB shear force and intramuscular fat, compared to maiden gilts. In general, sensory meat quality was comparable between the two groups. In processed meat only, once-bred gilts had higher juiciness and salinity and unfavourable increased stringiness, compared to maiden gilts. Thus, once-bred gilts produce valuable carcasses and are suitable for an outdoor seasonal rearing system.

Influence of dietary amino acid level on performance, carcass quality and health of organic pigs reared indoors and outdoors

Abstract The influence of dietary amino acids on performance and carcass quality was studied in 192 organic indoor and outdoor pigs given diets with different amino acid levels (recommended amino acid level, 7% and 14% lower) ad libitum in a two-phase feeding system. During phase 2, daily consumption of lysine, methionine+cystine and threonine was higher for outdoor than indoor pigs independent of amino acid level (p=0.002, 0.004 and 0.006, respectively). The outdoor pigs grew faster during phase 2 than the indoor pigs (p=0.001), although feed conversion ratio did not differ (p=0.358). Dressing percentage was higher for outdoor than for indoor pigs (p=0.011) but lean meat content did not differ (p=0.904). The health status of the pigs was evaluated and showed that the incidence of pigs seropositive to erysipelas was higher outdoors. Ascaris suum was present in both production systems, whereas Eimeria sp. only was found among outdoor pigs. The results indicate a discrepancy between pigs housed in different production systems rather than between pigs directed to different dietary amino acid levels. This suggests that growing/finishing pigs fed ad libitum can compensate for dietary amino acid levels lower than the current Swedish recommendations without affecting production results.

Effects of adrenocorticotrophin (ACTH) and progesterone on luteinising hormone (LH) secretion in recently castrated rams

The goal of the present study was to determine whether ACTH and progesterone have any effect on LH secretion and pulse frequency in recently castrated rams. Six 2-year-old Corriedale rams were castrated in the winter. The day before castration, blood samples were taken in order to establish the precastration LH levels. The rams were divided into an untreated group (group U: n = 2) and a treated group (group T: n = 4). The first treatment consisted of the i.v. administration of 0.5 mg of ACTH on day 20 post-castration, immediately after the first sample had been taken. During the second treatment, subcutaneous progesterone implants were given to group T for 5 days. Control samplings were performed one week before each treatment. Prior to castration, the testosterone levels were low, while after castration they were below the detection limit of the assay. Cortisol and progesterone concentrations were basal before castration in all of the animals and after castration in group U and also in the control samplings for group T. ACTH treatment caused a significant increase in both cortisol and progesterone levels for 3 h (P < 0.001). Progesterone implants raised progesterone levels in group T, but cortisol levels remained basal. Before castration, all animals had low LH levels and hardly any pulse activity was seen. After castration, both the number of LH pulses and the mean LH production increased significantly in all of the animals (P < 0.01). During the ACTH trial, LH pulse frequency was significantly reduced for the first 4 h following ACTH administration (P = 0.013), however, no such differences occurred in the prior control period. No effect was seen on mean LH concentration during the ACTH treatment. Progesterone treatment did not have any effect on either the number of LH pulses nor on LH concentrations (P > 0.05).