Effect of sexual stimulation on concentrations of 5α-androstenone and testosterone in the peripheral plasma of boars reared individually

Six Yorkshire boars were reared from 107 days of age in individual pens. No female pigs were housed in the same building. When the boars were 200 days old, sows in oestrus were introduced to the pens of five boars and remained with the boars for 2 days. No oestrous sow was introduced to the pen with the sixth boar. Plasma 5α-androstenone and testosterone concentrations were low between 107 and 200 days of age in all boars. The maximum mean concentrations of these two steroids during this period were 6.18 ± 0.72 and 3.04 ± 1.02 ng/ml, respectively. Plasma 5α-androstenone concentrations increased with advancing age (P < 0.01). A similar trend was not seen for plasma testosterone concentrations. Plasma concentrations of 5α-androstenone and testosterone increased by 247 ± 27% (P < 0.02) and 1212 ± 204% (P < 0.001), respectively, in the samples drawn 24 h after the introduction of the sexually receptive sows. The maximal mean concentrations recorded following sexual stimulation were 12.90 ± 1.80 and 17.51 ± 1.96 ng/ml for 5α-androstenone and testosterone, respectively. The control boar also showed increases in plasma 5α-androstenone (221%) and testosterone (751%) concentrations in the same period, probably in response to auditory and olfactory stimuli originating in the pens nearby with introduced oestrous sows.     

Sexual development and performance in boars exposed prenatally to triamcinolone

The objectives of this study were 1) to investigate the effects of triamcinolone exposure prenatally upon the gonadotropin-gonadal system and 2) to determine whether prenatal exposure affects the onset of puberty and postpuberal development in boars. Two or four litter-mate Yorkshire boars were randomly selected from five litters from sows fed unsupplemented diets and from seven litters from sows fed triamcinolone-supplemented diets. The boars were studied from birth through 30 wk of age. During this 30-wk period, the boars were bled once every 4 wk and testicular and body weight measurements were taken every 2 wk. From weeks 20 to 30 the boars were exposed weekly to an estrous gilt. During this time, the onset and frequency of mounting and ejaculation were recorded and the quality of the semen collected was evaluated. At slaughter, additional data on the male reproductive tract were collected. The prepartal feeding of triamcinolone to sows did not affect either the boars' weight gain or testicular volume during the 30-wk experimental period. Plasma concentrations of testosterone or cortisol also did not differ (P > 0.10) between the groups of boars. However, mounting and ejaculation occurred earlier in triamcinolone-exposed boars, suggesting that prepartal treatment of sows with triamcinolone may have enhanced the development of sexual behavior and onset of puberty in their offspring.     

The effect of the MC4R gene on boar taint compounds,sexual maturity and behaviour in growing-finishing boars and gilts

Societal pressure to ban surgical castration of male piglets is rising due to animal welfare concerns, thus other methods to prevent boar taint need to be explored. Genetic selection against boar taint appears to be a long-term sustainable alternative. However, as boar taint is linked to reproductive hormones, it is important to consider possible negative side effects such as delayed sexual maturity or changes in behaviour. We reported earlier that the melanocortin-4 receptor (MC4R) marker can be used to reduce boar taint levels in fat of boars. The objective of this study was to evaluate whether MC4R marker-assisted selection for lower boar taint prevalence affects plasma levels of boar taint compounds and testosterone; sexual maturity; behaviour; skin lesions; and lameness in boars and gilts. Using an intervention study with a 2×2 design, 264 boars and gilts differing on position 893 of the MC4R gene (AA v. GG) were compared. The MC4R polymorphism did not affect the plasma concentration of either androstenone or testosterone at different time points, whereas the concentration of skatole was significantly lower (P=0.003) and the concentration of indole tended to be lower (P=0.074) in GG compared with AA boars. A higher percentage of gilts of the GG genotype were in puberty at slaughter age compared with AA gilts (P<0.001). The age of the boars at sexual maturity (as indicated by the first positive preputial smear test) did not differ between AA and GG boars. In contrast, weight of GG boars at sexual maturity tended to be lower (P=0.065). During the period from 6 weeks of age to slaughter, boars and gilts of the GG genotype showed more playing behaviour (P=0.015) and less passive and feeding behaviour (P=0.003). They showed more skin lesions on their back and caudal area (P=0.022), and tended to show more skin lesions on their head and anterior area (P=0.093) compared with AA animals. In conclusion, the polymorphism in the MC4R gene can be used as a marker without negative effects on reproduction characteristics in boars and gilts. Genetic selection towards a lower prevalence of boar taint will lead to more active pigs with more skin lesions. Management strategies may therefore be necessary to reduce skin lesions in the selected animals.     

Reproductive development in young boars exposed to sexually mature, nonpregnant sows and gilts

Thirty Yorkshire boars were allotted by litter to one of two treatment groups. Fifteen boars were reared, from 14 to 22 wk of age, in fenceline contact with mature sows and gilts that were randomly exhibiting estrus. Fifteen littermates of these boars, reared without exposure to females, served as controls. Boar-to-boar sexual behaviors were observed 1 hour daily from 16 to 22 wk of age. At ages 14 to 30 wk, boars were weighed at 4-wk intervals. Five boars per treatment were slaughtered when 22 wk old and twelve others (six per treatment) when 30 wk old. Vesicular gland, bulb of the prostate gland, bulbourethral gland, and each testis, cauda epididymis, and combined caput and corpus epididymis were closely trimmed and weighed. Left cauda epididymal sperm and left testis elongated spermatids were determined by homogenization and hemacytometer counting. At 26, 30, and 38 wk of age, boars were tested for mating efficiency by exposure to an estrous gilt. Boars exposed to females tended to be lighter at 22 wk and were lighter at 30 wk (P<.05). Total male-to-male sexual acts from 16 to 22 wk were correlated with mating-efficiency score at 26 and 30 wk (r = .69 and .68, respectively; (P<.05)). Correlation between testicle size and total testicle elongated spermatids was high at 30 wk of age (r = .92; P<.001). Results indicated that exposing young boars to mature females had limited effects on the boars' reproductive development; however, there were strong indications of a relationship between boar behavior during rearing and postpuberal mating performance.     

Reproductive performance of wild boar females in Portugal

Reproductive tracts of 214 female wild boars collected in Central Portugal between October and February over the period 1997 to 2001 were examined. From this material, we were able to determine reproductive phenology (conception and birth periods) as well as age and weight of sows at puberty, ovulation rates of adults, foetal sex ratio, levels of intrauterine mortality, final litter size and postnatal mortality. Differences between year, region, age and body weight were analysed. A total of 66.8% of the females examined were gestating or lactating and 96.3% of these weighed >40 kg. The highest proportions of pregnant sows were found in the adult age/weight classes (74%). None of the juvenile females (1 year old and younger) were lactating and only 7% was pregnant. The average number of foetuses/female (4.1 ± 1.2SD) and that of corpora lutea per female (4.6 ± 1.7SD) increased from lighter and younger to heavier and older wild sows. Foetal sex ratio was biased towards males (1.3:1). Observed intrauterine mortality rate (9.7%) and postnatal mortality (6.3%) were among the lowest recorded in European wild boar populations. The productivity rate of the Central Portuguese wild boar population was calculated as 1.1 young per individual in the population. Conception and birth periods did not differ significantly between the considered 4 years. Birth synchronisation was pronounced in all the years, with a peak of births occurring in March.     

The mating behavior and reproduction performance in a multi-sire mating system for pigs

An important aim of organic animal production is to allow natural animal behaviour. Regarding reproduction techniques, artificial insemination is permitted but natural mating is preferred. The outdoor multi-sire system, where the sows are placed in large paddocks with a group of boars, is one example of a service system, which complies well with the organic ideals of facilitating natural animal behavior. However, very little knowledge is available about such system. Seven groups of in total of 47 sows and 31 boars were observed to study the mating behavior in an outdoor multi-sire mating system and the subsequent reproduction results. The time of start of courtship, behavior and the cause of disruption if the courtship was terminated, were recorded each time a boar courted a sow. All aggressive interactions between the boars were also recorded to estimate the boar ranking order. The observations revealed numerous poor quality matings, a huge variation in the number of times sows are mated, and overworked boars. Only 35% of all copulations lasted 2 min or more and 63% of all copulations were disrupted, mainly by competitor boars. The higher social status of the boar, the more copulations did it disrupt (p < 0.05). The outcome was an unacceptable variation in reproduction results. Only 71% of all estrus sows conceived, corresponding to a pregnancy rate of 77% of all mated sows. A large inter-group variation in reproduction performance was observed, indicating scope for improvements. In some groups all sows showed estrus and all sows conceived. Recommendations for improvement of the system are proposed.     

Active immunization of boars against gonadotropin releasing hormone. II. Effects on libido and response to testosterone propionate

Of 20 sexually mature Duroc boars showing normal libido, 10 were actively immunized against gonadotropin releasing hormone (GnRH). After immunization against GnRH, boars showed minimal sexual interest in an estrous female, while untreated boars showed normal libido. Eight of the boars actively immunized against GnRH were randomly assigned to treatment (T) or control (C) groups. Boars in the T and C groups were given testosterone propionate or vehicle, respectively, on Days 0, 5, 10, and 15. Boars in both groups were observed for libido in the presence of an estrous female every 4 d for 28 d. Mean libido score for T boars increased gradually until all boars displayed maximum libido on Day 20, but libido returned to low levels on Day 28. In contrast, C boars remained sexually inactive throughout the study. The results of this study indicate that active immunization of sexually mature boars eliminates sexual behavior and that sexual behavior can be restored quickly by administering testosterone propionate.     

Reproductive consequences of a reciprocal chromosomal translocation in two Duroc boars used to provide semen for artificial insemination

Cytogenetic analysis of 58 boars at an artificial insemination (AI) centre revealed the presence of a reciprocal chromosome translocation, rcp(1;11)(q−;p+), in two Duroc boars. Pedigree analysis of these two boars suggested familial transmission of the chromosome rearrangement. The reproductive consequences of this translocation were determined in a herd of sows that had received semen doses from these and other boars. All sows underwent multiple AI, with different groups established retrospectively depending on the percentage of semen doses provided by the carrier boars ([number of carrier boar doses/total number doses provided] x 100): 0%, 25%, 50%, 75%, 100%. The fertility rates (percentage of successful multiple AIs/total multiple AIs) recorded for multiple AI including semen doses from the carrier boars were not significantly different from those recorded when all semen doses were supplied by normal-karyotype boars. A reduction in litter size of 29.38% was observed, however, in litters sired by one of the carrier boars when its participation in multiple AI was 100%. The number of live-born piglets per litter gradually decreased (P < 0.05) as the percentage participation in multiple AI (25, 50, or 75%) of the carrier boar increased. In addition, both carrier boars sired some piglets with signs of cleft palate and complex malformations of the front legs; these died soon after birth. In conclusion, the boars carrying the translocation rcp(1;11)(q−;p+) showed reduced reproductive performance.     

Effects of boar contact and housing conditions on estrus expression in sows

In this paper, the authors review the effects of boar contact and different components of boar presence on onset and expression of estrus in weaned sows. Evidence is presented that boar contact may influence LH release, onset of follicle development and timing of ovulation after weaning. Once the sow is in estrus it is important that she shows estrous behavior, because her expression of estrus determines whether she will be inseminated. Boar contact or components thereof affect expression of estrus in sows. There are distinct differences between different components of boar contact in their effectiveness in the induction of estrous behavior (standing response) in sows. Habituation to boars (due to frequency of boar contact or housing of boars near sows) also affects estrus expression in sows. It is important to inseminate sows at the correct moment relative to ovulation. The use of different estrus detection protocols (e.g., by giving sows different levels of boar stimuli during estrus detection) may result in the definition of distinct periods of estrus that may help to predict the moment of ovulation. However, results to date are not very encouraging. Besides boar stimuli, the housing conditions of sows may affect onset of estrus and estrus expression. This paper focuses on social sow-to-sow interactions. The effects of group housing (as compared to individual housing) on onset of estrus and expression of estrus are equivocal. These effects likely depend on factors like aggression between pen mates, reproductive status of pen mates and social rank of sows within the group.     

Effects of long-term treatment with the GnrH agonist deslorelin (Suprelorin®) on sexual function in boars

Immunization against GnRH has been proven effective for boar taint removal, and long-term treatment with GnRH analogues has been shown to suppress GnRH dependent reproductive processes in several species. This study was conducted to treat boars (n = 5) with Suprelorin®, i.e., an implant that contains 4.7 mg of the long-acting GnRH analogue deslorelin, and to test the effects on sexual function. Insertion of the implant occurred at the age of 5 weeks and animals were observed until market age at 26-27 weeks. Surgically castrated (n = 4) and intact boars (n = 3) served as controls. Testes growth was markedly reduced and steroidogenesis (testosterone, estrone, estrone sulphate, estradiol 17β) as well as spermatogenesis suppressed in 4 of 5 GnRH treated boars, respectively. The remaining fifth boar resumed testes growth after week 17 of age and had high hormone concentrations when tested at weeks 26 and 27. Restoration of spermatogenesis was observed at 34 weeks of age. There were no effects of treatment on general health, nor were there local inflammatory reactions. Results indicate that suppression of sexual functions in boars due to long-term treatment with the GnRH agonist deslorelin through an implant such as Suprelorin® is possible and can last for several months up to market age; thus it has potential as an alternative to other methods used for boar taint removal. Because the maximum duration of suppression seems to vary between boars, further studies are necessary to refine the treatment.     

Effects of increased levels of supplemental vitamins during the summer in a commercial artificial insemination boar stud

Heat stress due to increasing extremes in ambient temperature and humidity results in reduced semen quality in boars. This has caused reduced efficiency of the swine industry, requiring more boars to breed the same number of sows. Vitamins such as vitamin C (VC) and E (VE) have been shown to improve semen quality in boars. Recently, vitamin D has been shown to improve semen quality in boars. The purpose of this experiment was to evaluate the effects of increased supplemental vitamins on boar reproduction during the summer season in a commercial boar stud. One hundred and sixty Pig Improvement Company (PIC) terminal line boars (n = 32 per treatment) and 39 maternal, heat-sensitive boars (n = 7 or 8 per treatment) were randomly allocated to treatment and fed a corn and soybean meal-based diet adjusted based on individual boar body condition score. A control (CNT) diet was used that met PIC recommendations for boars. Increased supplementation of specific vitamins was given in the form of a top-dress and consisted of CNT wheat middlings, CNT plus VC (560 mg/day), CNT plus 25-hydroxy vitamin D₃ (VD) (125 µg/day), CNT plus VE (275 mg/day) and CNT plus VC, VD and VE (CDE). The experiment was split into three periods based on maximum daily high temperatures in the barn, where period 1 was weeks 1 to 4, period 2 was weeks 5 to 11 and period 3 was weeks 12 to 14. Semen was collected from boars as needed using the stud’s normal production schedule and was analyzed for sperm quantity and quality characteristics. There were no dietary effects on semen volume, sperm concentration or total sperm production (P ≥ 0.553). Total motility of sperm was not impacted by diet (P = 0.115); although, VC tended (P = 0.064) to have a greater progressive motility than CDE. Percentages of morphologically normal sperm and normal acrosomes were not affected by dietary supplementation (P ≥ 0.157). Period effects were observed for most semen quality parameters, with quality generally becoming reduced over time. The present study demonstrates that increased supplementation of vitamins beyond PIC recommendations was not beneficial for boar reproduction during the summer.     

B-mode ultrasonographic evaluation of paired testicular diameter of mature boars in relation to average total sperm numbers

Crossbred, meat-type terminal sire boars (n = 215) were randomly assigned by age group (240-300, 301-360, 361-420, 421-480, 481-540, 541-600, and >721 days). Stud boars were on a once or twice weekly semen collection schedule. Testis diameters, in duplicate, were obtained using B-mode ultrasonography. Summation of average left and right testis diameter within boar gave the paired testicular diameter (PTD). Average ejaculate volume, sperm concentration (sperm/ml), and total sperm numbers for each boar were determined using composite data (average values) obtained from the last four semen collections. There was a <0.5cm difference between left and right testis diameters, with the left testis being the larger of the two testes (P = 0.03). There was no difference in PTD found between age groups in this study. Conversely, a dramatic increase in average total sperm numbers (ATSN) was observed between boars of 240-300 days (57.0+/-27.4 x 10(9) sperm) and up to 420 days (118.6+/-33.6 x 10(9) sperm) of age. The ATSN (127+/-32.5 x 10(9) sperm) remained constant for the 421-480 to >721-day age groups. The correlation between PTD and ATSN was low (r = 0.24) in this study. The results of this study demonstrate that normal boars should exhibit <0.5cm diameter difference between testes. As observed in other studies, the left testis was usually larger than the right testis. Correlation of total sperm numbers in a boar ejaculate using a composite ejaculate score (average values) and PTD measurements obtained using B-mode ultrasonography was poor when used in boars >8 months of age.     

The importance of the courting behaviour of the boar on the success of natural and artificial matings

Two studies were carried out at a commercial piggery to examine the importance of the courting behaviour of the boar on the fertility of both natural and artificial matings. In the first study the sexual behaviour of 24 breeding boars of known conception rate was observed. A significant correlation (r = + 0.48, P < 0.05) was found between the number of times the boar nosed the sides of the female and his conception rate record. In the second study 68 sows that were housed singly or in pairs were either artificially inseminated or briefly courted by a boar prior to artificial insemination. Allowing sows that were housed in pairs to be courted by a boar increased conception rate from 62.1 to 86.7% (P > 0.05) and litter size from 8.6 to 10.3 (P < 0.05) while for those sows housed singly these two parameters were decreased from 66.7 to 50.0% (P > 0.05) and 11.9 to 6.7 (P < 0.05), respectively. The two studies demonstrate the importance of the sociosexual environment on the fertility of natural and artificial matings.     

Assessment of sexual behavior and effect of semen collection pen design and sexual stimulation of boars on behavior and sperm output--a review

The importance of sexual behavior and factors influencing sexual behavior of AI boars has received minimal study. The majority of studies reviewed used a very small number of boars. A sexual behavior index (SBI) has been developed for naturally mating boars but not for AI boars. Some studies have reported significant correlations between sexual behavior traits and semen characteristics; while other studies did not find significant correlations. A new semen collection pen design (Reicks Design) has reduced the duration of time a boar requires to mount a dummy sow after entering the collection pen and the duration of time needed to exit the collection pen after ejaculation. In general, the observation of another boar mounted on the dummy sow prior to collection, releasing the penis after extension, exposing boars to non-estrous gilts for 2 days before collecting semen, placing a non-estrous gilt underneath a dummy, and removing the boar for 2 min after first mount did not enhance the number of sperm cells collected. Treatment of boars with PGF2alpha has facilitated the training of sexually experienced boars to mount a dummy sow but not that of sexually inexperienced boars. In general, the treatment of boars with PGF2alpha did not increase the total number of spermatozoa ejaculated.     

Farm and management characteristics associated with boar taint

Pig farms in the Netherlands producing boars have different levels of boar taint prevalence, as assessed by sensory evaluation with the human nose at the slaughter line. With a questionnaire to 152 Dutch pig producers (response rate 59%), farm and management characteristics were identified that are potentially associated with farm-level boar taint prevalence. Lower farm-level boar taint prevalence was associated with a smaller group size, a smaller pen surface per boar, newer housing equipment, not practicing restricted feeding in the last period before delivery, a longer fasting period before slaughter, a higher stocking weight and a lower fraction of boars from purebred dam line sows or from Pietrain terminal boars. These characteristics can be used to develop farm-level intervention strategies to control boar taint. More research effort is needed to establish causal relationships.     

Sexual motivation in relation to social rank in pair-housed sows

The influence of social subordination on sexual motivation during oestrus was studied using 36 sows of which 24 treatment sows were housed in pairs and 12 control sows were housed individually in 12 and 6 m(2) pens, respectively. Video recordings were made from 07:00 h to 19:00 h during the first 2 days after grouping, which took place 3 days after weaning of the piglets. Based on the aggressive interactions between the pair-housed sows, their rank was determined. From day 4 after weaning, a test for sexual proceptive behaviour was carried out twice daily and back-pressure test was carried out four times daily in order to detect standing oestrus. When standing oestrus had occurred, transrectal ultrasonographical scans were also carried out in order to determine if ovulation took place. The proceptivity test took place in a T-maze with a 2 m x 10 m runway ending in two 1.5 m x 1.5 m goal boxes each adjacent to a stimulus compartment. One compartment contained an adult sexually experienced boar and the other was empty. Latency to and duration of time spent close to the boar and time spent presenting were recorded during the 10-min test period. On the first day that standing oestrus had been detected, a test for sexual receptivity was also carried out by introducing the sow to a mature boar in his home pen (9 m(2)). Sexual- and fear-related behaviour of sow and boar were recorded until mating was terminated or the sow had spent 5 min in the pen without mating being initiated. During oestrus the proceptivity test showed a significant increase (P < 0.05) in the time spent standing close to the boar and in presenting for single-housed sows and for pair-housed dominant sows, but not for subordinate sows. During oestrus subordinate sows spent significantly less time standing close to the boar than the dominant sows (P = 0.01) and the same tended to be the case for presenting (P = 0.07). In the receptivity test more subordinate sows than dominant sows fled (40% versus 0%, P = 0.001) and more subordinate sows than dominant sows squealed (58% versus 15%, P = 0.02) as a response to boar stimulation. In both tests, the single-housed sows differed neither from the dominant nor the subordinate sows. There was however no difference between the groups in the weaning to oestrous interval, duration of oestrus and number of piglet born. In addition, all the sows ovulated. The results indicate that social subordination can have significant consequences for sexual motivation in sows. Subordinate sows showed fear-related behaviour in response to boar stimulation even when they were in standing oestrus. Thus, both heat detection and mating may be impaired in subordinate sows. The results emphasise the importance to alleviate the social stress experienced by subordinates as well as the need for stock people to pay special attention to these animals when they are to be mated or inseminated.     

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

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

The effect of modified eros centre, outdoor raising or conventional group housing on breeding gilts and its effects on reproductive performance over four parities

The present study was conducted in a large Croatian "built up unit". The objective of the study was to determine if an indoor modified eros centre (MEC) compared to indoor or outdoor group housing of gilts, influenced the onset of puberty of gilts and the reproductive performance of the evaluated females (n = 783) over four parities. The gilts were from the same nucleus herd. Gilts of same age (140-150 days of age), body condition (body condition score of 3-4) and similar genetics (four-way cross females), during the same season (January to April 1999), were randomly divided at arrival into three groups and treated as follows:MEC gilts (n = 279): These were placed into indoor MEC pens in groups of 8-10. The gilts had continuous fenceline contact to boars (one boar to two groups of gilts, boars were changed daily) and to shortly weaned oestrous sows. Gilts were regrouped and dislocated at 10-day intervals. Outdoor gilts (n = 263): These were kept in groups of 8-10 on a large pasture (80-100 m2 per group). The animals had fenceline contact to mature boar for 5-10 min daily. Control indoor gilts (n = 241): These were housed indoors in large pens in groups of 8-10. The animals had fenceline contact to mature boars for 5-10 min daily. Each outdoor group had an insulated hut with straw bedding. All gilts were fed ad libitum with the same commercial diet. Housing gilts in MEC resulted in earlier (P < 0.001) onset of estrus (MEC: 174.8 +/- 2.4 days, indoor group housing: 207.6 +/- 4.1 days, outdoor group housing: 187.4 +/- 2.1 days) and lower (P < 0.001) farrowing rate to first service (MEC: 70.97%, indoor group housing: 89.73%, outdoor group housing: 89.62%). Farrowing rate of regularly returning MEC gilts to second service was 95.00%. First total-born litter size, first liveborn litter size, first wean-to-estrus interval (WEI), percent of sows bred after first weaning, second total-born litter size, second liveborn litter size, average third and fourth total-born and liveborn litter size, number of sows having four litters, number of litters per sow, total number of pigs per sow, total number of liveborn pigs per sow showed no significant differences between the groups. More (P < 0.05) sows were culled in outdoor group. Compared to MEC and outdoor housing, indoor housed sows suffered higher (P < 0.05) percentage of anoestrus.     

Sexual behavior of castrated boars treated with prostaglandin F2α

The objectives were to test the hypothesis that exogenous prostaglandin F_2α (PGF_2α) temporarily restores sexual behavior of castrated boars, and to evaluate effects of PGF_2α on serum hormone concentrations. At 35 d after castration, nine lean-type adult boars were randomly assigned to three treatments in a 3 × 3 latin square (with three replicates). Treatments were three doses of PGF_2α doses (0, 10, and 20 mg) and three periods of treatment, with 5 d between each period. Serum testosterone (T) concentrations were non-detectable at the start of the experiment. Serum concentrations of estradiol (E2), LH, prolactin (PRL), and cortisol were unaffected (P > 0.05) by PGF_2α treatment. The interval from treatment to ejaculation in boars treated with 10 mg (758 s) or 20 mg (660 s) PGF_2α did not differ, but were different (P < 0.05) from control boars (>1 800 s). Ejaculation duration and false mounts differed (P < 0.05) between control boars and boars treated with 10 or 20 mg PGF_2α. In conclusion, PGF_2α treatment did not change serum concentrations of T, E2, LH, PRL, or cortisol, but restored sexual behavior. This restoration may have been due to an effect of PGF_2α directly in specific areas of the brain, or indirectly via release of other hormones that stimulated areas in the brain that affected sexual behavior.     

Early sexual maturity in local boars of Northeastern India: age-related changes in testicular growth, epididymal sperm characteristics and peripheral testosterone levels

The present study reports the age related changes in the peripheral testosterone levels, testicular and epididymal growth and development and cauda epididymal spermiogram in local pigs of Northeastern India, which attain sexual maturity around 3 months of age. Local boars (n = 20) were castrated at monthly intervals from 2 to 6 months of age (4 boars per month) to study the testicular growth and development and the epididymal spermiogram. Blood samples, collected from local boars (n = 6) at monthly intervals from 2 to 6 months of age, were analyzed for testosterone levels by radioimmunoassay. Compared to Hampshire boars, significantly (P < 0.05) high testosterone levels were observed in the local boars as early as 2 months of age. The mean (± SEM) level of testosterone in the local boars at 2, 3 and 4 months of age was 11.89 ± 1.52, 20.45 ± 1.33 and 20.38 ± 2.0 ngml⁻¹, respectively. Though there was consistently significant (P < 0.05) difference in the body weight between Hampshire and local pigs, the same was not observed in case of testicular weight except at 3 and 6 months of age. In line with the above observation, the testis:body weight ratio (gram testis per kg body weight) was significantly (P < 0.05) higher in the local boars compared to the Hampshire boars at any time of observation, which ranged from 0.8 to 1.0 in case of Hampshire and from 2.3 to 3.0 in local boars. The sperm concentration in the cauda epididymal fluid of local boars at 2, 3 and 6 months of age was 2255 ± 186.6, 3685 ± 103.8 and 4325 ± 146.2 million/ml, respectively and the sperm motility, viability and total abnormality was 73.3, 75.2 and 6.2%, respectively at 3 months of age. Taken together, the testosterone level, testicular growth and development and epididymal spermiogram indicate the trait of early sexual maturity in the local pigs as compared to Hampshire.