- Email: [email protected]
Treatment of swine summer infertility syndrome by means of oxytocin under field conditions
ELSEVIER
TREATMENT
OF SWlNE SUMMER INFERTILITY SYNDROME OXYTOClN UNDER FIELD CONDITIONS
BY MEANS
OF
I‘. J. Pefia. J. C. Dominguez, M. Carbajo, L. Anel and B. Alegre Department of Reproduction and Obstetrics Faculty of Veterinary Medicine, University of Leon Campus de Vegazana, 24071 Leon Spain Received for publication: Accepted:
March 28, 1997 October 21, 1997
ABSTRACT Endogenous oxytocin is released by the sow at the time of mating in response to stimulation by the boar, which may explain, at least partially, the importance of the relationship between the boar’s courting activity and the subsequent reproductive performance of the sow. The aim of this study was to determine the effects on reproductive performance of supplementing AI doses with exogenous oxytocin during the low fertility season. At an intensive piggery in northwest Spain 3 experimental groups were randomly formed and observed throughout the year. Group 1 sows were inseminated with semen supplemented with 4 IU oxytocin. Group 2 sows received 4 IU oxytocin injected through the vulvar lips mucosa at the time of insemination. Group 3 sows were inseminated without oxytocin and served as the controls. During the low fertility season the results for each group were as follows: farrowing rate 77.02, 56.25 and 54.39%. and litter size 10.7BO.28, 10.45~kO.31 and 8.53rt0.34 respectively. It is concluded that the addition of oxytocin to seminal doses just before AI is an easily applicable, effective method for increasing fertility and litter size during the summer months. Q 1998 by Elsewer Science
Inc
Key words: pig. summer infertility, treatment, oxytocin TNTRODIJCTION The tendency among pigs towards impaired reproductive efficiency during the summer has been reported by several authors, with Mac Lean being one of the first (13). The main symptom of summer infertility syndrome is a marked drop in fertility, as evidenced by a reduction in the number of sows farrowing (6, 12, 21) together with a major decrease in litter size (6, 14). The profitability of pig production depends on the number of pigs marketed per sow per year, so f&-rowing rate and litter size are, therefore, important factors determining both productivity and profitability. The addition of oxytocin and its analogues to the inseminate has been the subject of several studies (IO, 16), with most showing increases in the farrowing rate but. this increase has not always been significant (7). Nevertheless, herds with low fertility usually experience a significant improvement in their reproductive efficiency when inseminated with the supplemented semen. Since fertility during the summer is usually low, and since no data exist Thmgenology 49829+336, 0 1998 by Elsewr Science
1998 Inc.
0093-691x/98/$19.00 PII s0093-691x(98)00032-6
Theriogenology
830
concerning the effect of semen additives such as oxytocin during the low fertility season, we designed a clinical trial using oxytocin in conjunction with insemination to evaluate the reproductive efficiency of sows mated during the summer months. MATERIALS
AND METHODS
The study was performed in an intensive piggery of 932 sows in northwest Spain. The experimental animals consisted of Landrace x Yorkshire sows, which were kept in breeding groups of 12. On this farm artificial insemination is practiced systematically using the seminal rich fraction diluted in a commercial seminal solvent which formula is not given (MR-AB)a ensuring at least 3 x 109 sperm cells per loo-ml insemination dose. Semen was collected from 9 hybridb boars and was used for artificial insemination within 24 h. After estrus detection (standing reflex using the back pressure test without presence of the boar) the sows were inseminated first at the observed estrus and again 24 h later. The boar was not present at insemination. and sows were checked for estrus twice daily. Throughout the year 3 experimental groups of 20 sows each vvere randomly formed for each month of the year. Homogeneous parity among SOWSin the different groups was maintained. The sovvs were between their first and eighth parity and were penned individually adjacent to the boars’ stalls. The average parity (meant%M) for each treatment group (oxy/tocin added to semen, oxytocin injected into the vulva and controls) was respectively as follows: Season I- 5.57kO.29. 4.4650.33 and 4.91+0.30; Season 2. 5.01+0.38, 4.83kO.32 and 4.71?0.36: Season 3- (low fertility season) 4.36kO.31, 4 83kO.32 and 5.12iO34 and Season 4- 4.26t0.33, 4.25+0.30 and 3.63i0.32. Weaning-to-estrus interval for each group was not recorded. Group I sows were inseminated with semen doses to which 4 IU {of oxytocin (oxyvet8 )” were added just before insemination by means of an insulin syringe. The 4 UI dose of oxytocin was chosen because is practical for on farm use (i.e., 115 of a ml-which is easy for pig producers to use) Before administration the seminal dose was homogenized by gentle shaking. Group 2 sows received 4 IU oxytocin injected through the vulvar lips mucosa with an insulin syringe at the time of insemination Group 3 served as the control group and were inseminated without oxytocin treatment. Pregnancy diagnosis was based on the lack of oestrus symptoms 21 to 23 d after insemination. At 110 d of gestation, sows were moved into farrowing crates where they remained until the litter was weaned at approximately 28 d post farrowing. During gestation the sows received a diet formulated to provide 13.1 MJ/Kg -’ and 16.4 % crude protein. Water was provided ad lihitum.
a Kubus S A Madrid. Spain b Gentuca Hypor S. A La CoruAa, ’ Bayer
S A Barrelona,
Spain
Span
Theriogenology
831
The following parameters were studied: return to estrus rate, farrowing index and litter size (total number born). The dependent variable litter size was analyzed by the least squares method using the general linear models procedure of SAS (I 8). The statistical study was made according to the 1node1.
Where yijkl is the observatron for each trait, u is the mean, Ti is the effect of the treatment (i = I, 3). Sj is the effect of the season (j = 1. 4). ‘TSij is the effect ofthe interaction treatment-by-season, Pk is the effect ofthe parity (k = 1. 8). eijhl is the residual effect. ‘[‘he independent variable was season (Season 1. January to March; Season 2. /April to June; Season -3, July to September; and Season 4. October to December). Comparison between means was made using Duncan’s multiple range test. A separate analysis WBS conducted for each season. Fertility and return to estrus were analyzed using the Chi-square method and a comparison between means technique (2).
The effects ofoxytocin added to the semen dose or injected through the vulvar lips on return to estrus, the farrowing rate and litter size are shown in Tables 1 to 4. Both oxytocin treatments improved reproductive efficiency of the sows inseminated during the summer, although only the results for the oxytocin enriched inseminate group were significant. The farrowing rate was 18.36% higher for sows inseminated with semen containing 4 IU oxytocin compared with control sows, while return to estrus rate during the summer was 2 1.64% higher for control sows than for those treated with oxytocin 411 I. The effects ot’ the treatment on litter sire wet-c :,imilar, with an increase in litter size of 2.24 piglets when 0x4 tocin was added to the insemination dose and 1.92 pig1et.s when it was injected through the vulvar 11~s. In seasons other than the summer only slight insignificant increases in farrowing rates were observed, while litter size was significantly higher in the oxytocin treated groups throughout the year except during Season 1 (January to March) in sows receiving oxyrocin injected into the vulvar mucosa.
a32
Theriogenology
‘Table 1. Return to estrus, f&rowing rate and litter size for sows inseminated with semen supplemented with 4 IU oxytocin, for those injected with 4 IU oxytocin into the vulva at the time of AI and for the controls during the low fertility summer period (Season 3 July to September).
-
Number of sows return to estrus rate (%) farrowing rate(“b) Litter size (n)
-
Treatment ____Oxytocin (4 IU) Oxytocin. (4 IU) added to injected into semen the vulvar lips 63 64 22.22 i 5.23 a 37.50 2 6.05a’b 73.02 i 5.59 a 56.25 2~6.20 ab 10.45+0,3 1 c 10.77+0.28 ’
Within a row values with different superscripts are significantiy P
Controls
57 43.86 + 6.57 b 54.39 + 6.59 b 8.53k0.34d
different a-b, PcO.05; c-d,
Iable 2. Return to oestrus. farrowing rate and litter size for sows inseminated with semen supplemented with 4 IU oxytocin for those injected with 4 IU oxytocin into the vulva at the time of AI and for the controls during the winter (Season I, January to March).
Number of sows Return to oestrus rate (%) Farrowing rate(%) Litter size (n:)
Treatment Oxytocin (4 IU) Oxytocin. (4 IU) added to injected into semen the vulvar lips 61 56 6.56 F 1.00 7.14i 1.12 8X.52+4.08 92.86k3.44 12.20*0.X?” 10.76+0.29’ --
Controls
71 9.86k 3.53 87.32k3.94 10.12+0.27d
Within a row values with different superscripts are significantly different c-d. P
833
Theriogenology
Table 3. Return to estrus, farrowing rate and litter size for sows inseminated with semen supplemented with 4 IU oxytocin, for those injected with 4 IU oxytocin into the vulva at the time of insemination and for the controls during the spring (Season 3, April to June).
Number of sows Return to oestrus rate(%) Farrowing rate I %) Litter size (n) --
Oxytocin. (4 IU) added to semen 59 I 1.86 i- 4.20 86.44 + 4.56 I 1.98F0.‘9 -
Treatment Oxytocin, (4 IU) injected into the vulvar lips 62 16.13T4.67 80.65? 5.01 1 I .29&0.29’
Controls
60 23.33k5.46 76.67k6.23 I 0.09~0.30d --
Within a row \;alues with different superscripts are significantly different c-d, P
834
Theriogenology
Although there are some studies on semen additives such oxytocin (IO, 16) as well as on treating summer infertility (8, 9), to the authors’ knowledge this is the first report to focus on the use of semen additives to minimize summer infertility. Oxytocin added to seminal doses just prior to use is an efficacious treatment for summer infertility, and our results support previous findings indicating the beneficial effect of using semen additives such oxytocin in low fertility herds. (5). Sperm transport is defined as the movement of spermatozoa up the female reproductive tract from the site of deposition of semen (cervix and corpus uteri) to the site of fertilization (ampulla of the oviduct). Oxytocm is know to increase both uterine and oviductal contractions (I 7) and intrauterine infusion of oxytocin increases sperm transport (1). Supplementation of extended (100 ml) semen with 4 IU oxytocin may have enhanced sperm transport along the female genital tract thus increasing the farrowing rate and litter size in our experiment. Artificially inseminated sows lack adequate boar stimuli at the time of AI (3. Il. 15. 19, 20). and this may be especially marked during the summer. In our study herd estrus detection is performed without a boar, so the lack of adequate stirnuli may be especially manifested. Boar stimuli are normally olfactory, tactile, visual and auditory. During courting the boar emits frothy saliva produced in the submaxillary salivary glands, and urinates frequently (19). The saliva and urine of mature boars contain large quantities of the pheromones Sa-androstenone and 3a-androstenol. Tactile contacts are mainly directed toward the snout, the ano-genital region and the sides of the sow. Furthermore, during courting the boar grunts. which may act as an auditory stimulus. The effects of a number of boar stimuli on sperm transport have been evaluated: Mattioli et al. (15) sprayed 5tr androstendione in front of the sow‘s snout for 2 set and found a 2-to-10 fold increase in oxytocin withm 8 min. A 40-fold rise occurred in peripheral oxytocin levels during mating. while little or no increase was observed in sows artificially inseminated (3). The addition of oxytocin may mimic stimuli from the boar and rhus enhance sperm transport under conditions. when boar stimuli at insemination are low. During the low fertility season, oxytocin improved litter size when added to the seminal dose or injected through the vulvar lips at the time of Al, but it failed to enhance the conception rate and farrowing rate injected through the vulvar mucosa. The effect on litter size could be attributable to an increase in the ovulation rate or, more likely, to an improvement in fertilization of the o\a (ie.. same number of ovulations in all sows but differences in fertilization of ova or survival and development of embryos). The same mechanism may explain the increase in the number of sows farrowing. We have observed that even though oxytocin failed to increase farrowing rates in other seasons, it was effective increasing litter size throughout the year; thus it is a method for increasing the number of piglets horn in herds with small litters. In conclusion. the addition of oxytocin (4 IL) to the inseminate just before the Al is an easily applicable and effective method for maximizing fertility during the summer months and increasing litter size during this normally low fertility season. These results indicate the importance ot. further studies on sperm transport mechanisms and ovulation-stimulating substances present in seminal plasma (4. 1 I ) which may affect the success of swine AI, especially during the summer.
Theriogenology
835 REFERENCES
1. Baker R D. Dzuik P J, and Norton H W. Effect of volume of semen, number of sperm and drugs on transport of sperm in artificially inseminated gilts. J Anim Sci 1968. 27:88-93. 2. Carrasco J L. El metodo estadistico en la investigacibn medica. Madrid: Ciencia 3 S.A.1986 3. Claus R, and Schams D. Influence of mating and intra - uterine oestradiol infusion on peripheral oxytocin concentrations in the sow. J Endocrinol 1990; 126:361-365. 4. Claus R. Physiological role of seminal plasma components in the female reproductive tract. J Reprod Fertil 1990: 40 (Suppl): I 17-l 3 1. 5. Domingucz J C. Anel L. Carbajo M. Boixo J C, PeAa F J. Addition of oxytocin to swine semen and its effect on fertility and prolificit!;. 12th Int. C’ongr. Anim. Reprod. AI. 1992; 3:1404-1405 6. DominyucL J C. Peiia F J. Anel L. C’arba.jo M. Swine summer infertility syndrome in northwest Spain. Vet Ret 1996: 139:93-94 7. Flowers W I. and Esbcnshade K L. Optimizing management of natural and artificial matings in swine J Reprod Fertil 1993 48 (Suppl):217-228. 8. Greer 1: B. Gardner 1 A and Wright G I~..Failure of dietary vitamin c’ supplementation to prevent seasonal infertility Austr J I-xp Agric 1987; 27:343-347. 9. Hennesy 1) I’ and Johnston N. 6. I’he use of PMSG to prevent summer infertility in pigs, Proceedings of the ltith annual conference of the Australian Society for Reproductive Biology Melbourne Australia Paper no 99. 1984. IO. Henze A. and Jurk Ii.. Recent results on Ihe addition of uterotropic substances to the insemination dose in gilts and sows Monastshefte fur Veterinarmedizin. 1986: 41:8078 IO .abstr I I. Hunter. M. G. and Weisak, T. Evidence for and implications of follicular heterogeneity in pigs. J Reprod Fertil 1990: 40 (Suppl):l63-177. 12. Love R J, I-vans Cr. Kupliec C. Seasonal effects on fertility in gilts and sows. J Reprod Fertil 1993 38 (suppl):l91-206 13. MacLean (1 W. Observations on non-infectious infertility in sows. Vet Ret 1969: 85: 675682. 14. Martinat-Botte F. Thatcher W W and Terqui M. Seasonal variations of pig litter size In: Seren F. Mattioli M (eds). Definition of the Summer Infertility Problem in the Pig Lusemburg. Office for Official Publications of the European Communities 1987: 63-70. 15. Mattioli M. Galeatti G. Conte F, and Seren E, Effect of 5 01 andost -16-ene-3-one on oxytocin release in estrus sows. Thcriogenolog~y 1986 25:399-403. 16. Odehnal F. Barth 1‘. and Jost K. The etfect of Depotocin8 (carbetocin) added to insemination doses of boar semen on the conception of‘ sows and their fertility. Pig News lnfor. 1990: I I : 203 abstr. 17. Reeves J J. Indocrinology of reproduction In: Hafez I! S E (ed), Reproduction of Domestic Animals, Philadelphia: I,ea and Febiger: 1987: 85-106. 18. SAS!S’TAT” Llser’s Guide, Release 6.03 SAS Institute. Cary N C:l988 19. Signoret 3 P ‘l‘he reproductive behavior tjl‘piys in relation to fertility. Vet Ret 1971; 88:3438.
836 20. Soede N M. Boar stimuli around insemination review. Anim Reprod Sci 1993; 32: 107- 125.
Theriogenology affect reproductive
processes in pigs: a
2 1. Te Brake J H A and Aalbers J G. Effect of season on the fertility of sows and on application of A. I. In: Seren. E. Mattioli M (eds) Definition of the Summer Infertility Problem in the Pig. Luxemburg: Office for Official Publications of the European Communities:1987; 83 89.
TREATMENT
OF SWlNE SUMMER INFERTILITY SYNDROME OXYTOClN UNDER FIELD CONDITIONS
BY MEANS
OF
I‘. J. Pefia. J. C. Dominguez, M. Carbajo, L. Anel and B. Alegre Department of Reproduction and Obstetrics Faculty of Veterinary Medicine, University of Leon Campus de Vegazana, 24071 Leon Spain Received for publication: Accepted:
March 28, 1997 October 21, 1997
ABSTRACT Endogenous oxytocin is released by the sow at the time of mating in response to stimulation by the boar, which may explain, at least partially, the importance of the relationship between the boar’s courting activity and the subsequent reproductive performance of the sow. The aim of this study was to determine the effects on reproductive performance of supplementing AI doses with exogenous oxytocin during the low fertility season. At an intensive piggery in northwest Spain 3 experimental groups were randomly formed and observed throughout the year. Group 1 sows were inseminated with semen supplemented with 4 IU oxytocin. Group 2 sows received 4 IU oxytocin injected through the vulvar lips mucosa at the time of insemination. Group 3 sows were inseminated without oxytocin and served as the controls. During the low fertility season the results for each group were as follows: farrowing rate 77.02, 56.25 and 54.39%. and litter size 10.7BO.28, 10.45~kO.31 and 8.53rt0.34 respectively. It is concluded that the addition of oxytocin to seminal doses just before AI is an easily applicable, effective method for increasing fertility and litter size during the summer months. Q 1998 by Elsewer Science
Inc
Key words: pig. summer infertility, treatment, oxytocin TNTRODIJCTION The tendency among pigs towards impaired reproductive efficiency during the summer has been reported by several authors, with Mac Lean being one of the first (13). The main symptom of summer infertility syndrome is a marked drop in fertility, as evidenced by a reduction in the number of sows farrowing (6, 12, 21) together with a major decrease in litter size (6, 14). The profitability of pig production depends on the number of pigs marketed per sow per year, so f&-rowing rate and litter size are, therefore, important factors determining both productivity and profitability. The addition of oxytocin and its analogues to the inseminate has been the subject of several studies (IO, 16), with most showing increases in the farrowing rate but. this increase has not always been significant (7). Nevertheless, herds with low fertility usually experience a significant improvement in their reproductive efficiency when inseminated with the supplemented semen. Since fertility during the summer is usually low, and since no data exist Thmgenology 49829+336, 0 1998 by Elsewr Science
1998 Inc.
0093-691x/98/$19.00 PII s0093-691x(98)00032-6
Theriogenology
830
concerning the effect of semen additives such as oxytocin during the low fertility season, we designed a clinical trial using oxytocin in conjunction with insemination to evaluate the reproductive efficiency of sows mated during the summer months. MATERIALS
AND METHODS
The study was performed in an intensive piggery of 932 sows in northwest Spain. The experimental animals consisted of Landrace x Yorkshire sows, which were kept in breeding groups of 12. On this farm artificial insemination is practiced systematically using the seminal rich fraction diluted in a commercial seminal solvent which formula is not given (MR-AB)a ensuring at least 3 x 109 sperm cells per loo-ml insemination dose. Semen was collected from 9 hybridb boars and was used for artificial insemination within 24 h. After estrus detection (standing reflex using the back pressure test without presence of the boar) the sows were inseminated first at the observed estrus and again 24 h later. The boar was not present at insemination. and sows were checked for estrus twice daily. Throughout the year 3 experimental groups of 20 sows each vvere randomly formed for each month of the year. Homogeneous parity among SOWSin the different groups was maintained. The sovvs were between their first and eighth parity and were penned individually adjacent to the boars’ stalls. The average parity (meant%M) for each treatment group (oxy/tocin added to semen, oxytocin injected into the vulva and controls) was respectively as follows: Season I- 5.57kO.29. 4.4650.33 and 4.91+0.30; Season 2. 5.01+0.38, 4.83kO.32 and 4.71?0.36: Season 3- (low fertility season) 4.36kO.31, 4 83kO.32 and 5.12iO34 and Season 4- 4.26t0.33, 4.25+0.30 and 3.63i0.32. Weaning-to-estrus interval for each group was not recorded. Group I sows were inseminated with semen doses to which 4 IU {of oxytocin (oxyvet8 )” were added just before insemination by means of an insulin syringe. The 4 UI dose of oxytocin was chosen because is practical for on farm use (i.e., 115 of a ml-which is easy for pig producers to use) Before administration the seminal dose was homogenized by gentle shaking. Group 2 sows received 4 IU oxytocin injected through the vulvar lips mucosa with an insulin syringe at the time of insemination Group 3 served as the control group and were inseminated without oxytocin treatment. Pregnancy diagnosis was based on the lack of oestrus symptoms 21 to 23 d after insemination. At 110 d of gestation, sows were moved into farrowing crates where they remained until the litter was weaned at approximately 28 d post farrowing. During gestation the sows received a diet formulated to provide 13.1 MJ/Kg -’ and 16.4 % crude protein. Water was provided ad lihitum.
a Kubus S A Madrid. Spain b Gentuca Hypor S. A La CoruAa, ’ Bayer
S A Barrelona,
Spain
Span
Theriogenology
831
The following parameters were studied: return to estrus rate, farrowing index and litter size (total number born). The dependent variable litter size was analyzed by the least squares method using the general linear models procedure of SAS (I 8). The statistical study was made according to the 1node1.
Where yijkl is the observatron for each trait, u is the mean, Ti is the effect of the treatment (i = I, 3). Sj is the effect of the season (j = 1. 4). ‘TSij is the effect ofthe interaction treatment-by-season, Pk is the effect ofthe parity (k = 1. 8). eijhl is the residual effect. ‘[‘he independent variable was season (Season 1. January to March; Season 2. /April to June; Season -3, July to September; and Season 4. October to December). Comparison between means was made using Duncan’s multiple range test. A separate analysis WBS conducted for each season. Fertility and return to estrus were analyzed using the Chi-square method and a comparison between means technique (2).
The effects ofoxytocin added to the semen dose or injected through the vulvar lips on return to estrus, the farrowing rate and litter size are shown in Tables 1 to 4. Both oxytocin treatments improved reproductive efficiency of the sows inseminated during the summer, although only the results for the oxytocin enriched inseminate group were significant. The farrowing rate was 18.36% higher for sows inseminated with semen containing 4 IU oxytocin compared with control sows, while return to estrus rate during the summer was 2 1.64% higher for control sows than for those treated with oxytocin 411 I. The effects ot’ the treatment on litter sire wet-c :,imilar, with an increase in litter size of 2.24 piglets when 0x4 tocin was added to the insemination dose and 1.92 pig1et.s when it was injected through the vulvar 11~s. In seasons other than the summer only slight insignificant increases in farrowing rates were observed, while litter size was significantly higher in the oxytocin treated groups throughout the year except during Season 1 (January to March) in sows receiving oxyrocin injected into the vulvar mucosa.
a32
Theriogenology
‘Table 1. Return to estrus, f&rowing rate and litter size for sows inseminated with semen supplemented with 4 IU oxytocin, for those injected with 4 IU oxytocin into the vulva at the time of AI and for the controls during the low fertility summer period (Season 3 July to September).
-
Number of sows return to estrus rate (%) farrowing rate(“b) Litter size (n)
-
Treatment ____Oxytocin (4 IU) Oxytocin. (4 IU) added to injected into semen the vulvar lips 63 64 22.22 i 5.23 a 37.50 2 6.05a’b 73.02 i 5.59 a 56.25 2~6.20 ab 10.45+0,3 1 c 10.77+0.28 ’
Within a row values with different superscripts are significantiy P
Controls
57 43.86 + 6.57 b 54.39 + 6.59 b 8.53k0.34d
different a-b, PcO.05; c-d,
Iable 2. Return to oestrus. farrowing rate and litter size for sows inseminated with semen supplemented with 4 IU oxytocin for those injected with 4 IU oxytocin into the vulva at the time of AI and for the controls during the winter (Season I, January to March).
Number of sows Return to oestrus rate (%) Farrowing rate(%) Litter size (n:)
Treatment Oxytocin (4 IU) Oxytocin. (4 IU) added to injected into semen the vulvar lips 61 56 6.56 F 1.00 7.14i 1.12 8X.52+4.08 92.86k3.44 12.20*0.X?” 10.76+0.29’ --
Controls
71 9.86k 3.53 87.32k3.94 10.12+0.27d
Within a row values with different superscripts are significantly different c-d. P
833
Theriogenology
Table 3. Return to estrus, farrowing rate and litter size for sows inseminated with semen supplemented with 4 IU oxytocin, for those injected with 4 IU oxytocin into the vulva at the time of insemination and for the controls during the spring (Season 3, April to June).
Number of sows Return to oestrus rate(%) Farrowing rate I %) Litter size (n) --
Oxytocin. (4 IU) added to semen 59 I 1.86 i- 4.20 86.44 + 4.56 I 1.98F0.‘9 -
Treatment Oxytocin, (4 IU) injected into the vulvar lips 62 16.13T4.67 80.65? 5.01 1 I .29&0.29’
Controls
60 23.33k5.46 76.67k6.23 I 0.09~0.30d --
Within a row \;alues with different superscripts are significantly different c-d, P
834
Theriogenology
Although there are some studies on semen additives such oxytocin (IO, 16) as well as on treating summer infertility (8, 9), to the authors’ knowledge this is the first report to focus on the use of semen additives to minimize summer infertility. Oxytocin added to seminal doses just prior to use is an efficacious treatment for summer infertility, and our results support previous findings indicating the beneficial effect of using semen additives such oxytocin in low fertility herds. (5). Sperm transport is defined as the movement of spermatozoa up the female reproductive tract from the site of deposition of semen (cervix and corpus uteri) to the site of fertilization (ampulla of the oviduct). Oxytocm is know to increase both uterine and oviductal contractions (I 7) and intrauterine infusion of oxytocin increases sperm transport (1). Supplementation of extended (100 ml) semen with 4 IU oxytocin may have enhanced sperm transport along the female genital tract thus increasing the farrowing rate and litter size in our experiment. Artificially inseminated sows lack adequate boar stimuli at the time of AI (3. Il. 15. 19, 20). and this may be especially marked during the summer. In our study herd estrus detection is performed without a boar, so the lack of adequate stirnuli may be especially manifested. Boar stimuli are normally olfactory, tactile, visual and auditory. During courting the boar emits frothy saliva produced in the submaxillary salivary glands, and urinates frequently (19). The saliva and urine of mature boars contain large quantities of the pheromones Sa-androstenone and 3a-androstenol. Tactile contacts are mainly directed toward the snout, the ano-genital region and the sides of the sow. Furthermore, during courting the boar grunts. which may act as an auditory stimulus. The effects of a number of boar stimuli on sperm transport have been evaluated: Mattioli et al. (15) sprayed 5tr androstendione in front of the sow‘s snout for 2 set and found a 2-to-10 fold increase in oxytocin withm 8 min. A 40-fold rise occurred in peripheral oxytocin levels during mating. while little or no increase was observed in sows artificially inseminated (3). The addition of oxytocin may mimic stimuli from the boar and rhus enhance sperm transport under conditions. when boar stimuli at insemination are low. During the low fertility season, oxytocin improved litter size when added to the seminal dose or injected through the vulvar lips at the time of Al, but it failed to enhance the conception rate and farrowing rate injected through the vulvar mucosa. The effect on litter size could be attributable to an increase in the ovulation rate or, more likely, to an improvement in fertilization of the o\a (ie.. same number of ovulations in all sows but differences in fertilization of ova or survival and development of embryos). The same mechanism may explain the increase in the number of sows farrowing. We have observed that even though oxytocin failed to increase farrowing rates in other seasons, it was effective increasing litter size throughout the year; thus it is a method for increasing the number of piglets horn in herds with small litters. In conclusion. the addition of oxytocin (4 IL) to the inseminate just before the Al is an easily applicable and effective method for maximizing fertility during the summer months and increasing litter size during this normally low fertility season. These results indicate the importance ot. further studies on sperm transport mechanisms and ovulation-stimulating substances present in seminal plasma (4. 1 I ) which may affect the success of swine AI, especially during the summer.
Theriogenology
835 REFERENCES
1. Baker R D. Dzuik P J, and Norton H W. Effect of volume of semen, number of sperm and drugs on transport of sperm in artificially inseminated gilts. J Anim Sci 1968. 27:88-93. 2. Carrasco J L. El metodo estadistico en la investigacibn medica. Madrid: Ciencia 3 S.A.1986 3. Claus R, and Schams D. Influence of mating and intra - uterine oestradiol infusion on peripheral oxytocin concentrations in the sow. J Endocrinol 1990; 126:361-365. 4. Claus R. Physiological role of seminal plasma components in the female reproductive tract. J Reprod Fertil 1990: 40 (Suppl): I 17-l 3 1. 5. Domingucz J C. Anel L. Carbajo M. Boixo J C, PeAa F J. Addition of oxytocin to swine semen and its effect on fertility and prolificit!;. 12th Int. C’ongr. Anim. Reprod. AI. 1992; 3:1404-1405 6. DominyucL J C. Peiia F J. Anel L. C’arba.jo M. Swine summer infertility syndrome in northwest Spain. Vet Ret 1996: 139:93-94 7. Flowers W I. and Esbcnshade K L. Optimizing management of natural and artificial matings in swine J Reprod Fertil 1993 48 (Suppl):217-228. 8. Greer 1: B. Gardner 1 A and Wright G I~..Failure of dietary vitamin c’ supplementation to prevent seasonal infertility Austr J I-xp Agric 1987; 27:343-347. 9. Hennesy 1) I’ and Johnston N. 6. I’he use of PMSG to prevent summer infertility in pigs, Proceedings of the ltith annual conference of the Australian Society for Reproductive Biology Melbourne Australia Paper no 99. 1984. IO. Henze A. and Jurk Ii.. Recent results on Ihe addition of uterotropic substances to the insemination dose in gilts and sows Monastshefte fur Veterinarmedizin. 1986: 41:8078 IO .abstr I I. Hunter. M. G. and Weisak, T. Evidence for and implications of follicular heterogeneity in pigs. J Reprod Fertil 1990: 40 (Suppl):l63-177. 12. Love R J, I-vans Cr. Kupliec C. Seasonal effects on fertility in gilts and sows. J Reprod Fertil 1993 38 (suppl):l91-206 13. MacLean (1 W. Observations on non-infectious infertility in sows. Vet Ret 1969: 85: 675682. 14. Martinat-Botte F. Thatcher W W and Terqui M. Seasonal variations of pig litter size In: Seren F. Mattioli M (eds). Definition of the Summer Infertility Problem in the Pig Lusemburg. Office for Official Publications of the European Communities 1987: 63-70. 15. Mattioli M. Galeatti G. Conte F, and Seren E, Effect of 5 01 andost -16-ene-3-one on oxytocin release in estrus sows. Thcriogenolog~y 1986 25:399-403. 16. Odehnal F. Barth 1‘. and Jost K. The etfect of Depotocin8 (carbetocin) added to insemination doses of boar semen on the conception of‘ sows and their fertility. Pig News lnfor. 1990: I I : 203 abstr. 17. Reeves J J. Indocrinology of reproduction In: Hafez I! S E (ed), Reproduction of Domestic Animals, Philadelphia: I,ea and Febiger: 1987: 85-106. 18. SAS!S’TAT” Llser’s Guide, Release 6.03 SAS Institute. Cary N C:l988 19. Signoret 3 P ‘l‘he reproductive behavior tjl‘piys in relation to fertility. Vet Ret 1971; 88:3438.
836 20. Soede N M. Boar stimuli around insemination review. Anim Reprod Sci 1993; 32: 107- 125.
Theriogenology affect reproductive
processes in pigs: a
2 1. Te Brake J H A and Aalbers J G. Effect of season on the fertility of sows and on application of A. I. In: Seren. E. Mattioli M (eds) Definition of the Summer Infertility Problem in the Pig. Luxemburg: Office for Official Publications of the European Communities:1987; 83 89.