Effect of gonadotropin treatment on estrus, ovulation, and litter size in weaned and anestrous sows

Effects of kisspeptin-10 on the reproductive performance of sows in a fixed-time artificial insemination programme

Kisspeptin (KP) is a major positive regulator of the hypothalamo-pituitary-gonadal axis and affects female reproductive cyclicity in mammals. It offers an attractive alternative strategy to control reproduction in fixed-time artificial insemination (FTAI) protocols. We aimed to evaluate the effects of different doses of kisspeptin-10 (KP-10) on sow reproductive performance in FTAI protocols. One hundred ninety-eight weaned sows were divided into three groups at random. A FTAI-GnRH group of sows (n = 98) received 100 µg (2 mL) gonadotropin-releasing hormone (GnRH; gonadorelin) by intramuscular injection at 96 h after weaning (t = 0 h); FTAI-KPL (KPL: low-dose KP-10, n = 50), and FTAI-KPH groups of sows (KPH: high-dose KP-10, n = 50) received 0.5 or 1 mg KP-10 (2 mL) respectively at 96 h after weaning. Sows were checked twice daily for oestrus. Ultrasonographic evaluations were performed to determine the follicular diameter and time of ovulation; blood samples were collected immediately before injection (t₀ = 0 min) and at 15, 30, 45, 60, 75, 90 min, 24 and 48 h postinjection. Sows were inseminated at 112 and 132 h after weaning. The oestrus rates (96 vs 92%; 96 vs 88%) and weaning-to-oestrus intervals (98.9 vs 98.6 h; 98.9 vs 97.1 h) were not affected by treatment, but oestrus in the FTAI-KPL group was significantly longer than in the FTAI-GnRH group (38.7 vs 30.0 h; P < 0.05). The peak LH concentrations were 1.29 times greater than at t₀ = 0 in the FTAI-GnRH group, and 1.45 and 1.44 times greater than at t₀ = 0 in the FTAI-KPL and FTAI-KPH groups, respectively. Follicular diameters and pregnancy rates (86 vs 88%, 86 vs 80%, respectively) did not differ between the treatments. Moreover, the total numbers of piglets born and those born alive did not differ among the three groups. These findings suggested that 0.5 mg KP-10 given at 96 h after weaning could be used in FTAI programmes to manage batch farrowing in sows.

Ovulatory Response of Weaned Sows to an Altered Ratio of Exogenous Gonadotrophins

Simple Summary

Efficient pork production relies on a consistent supply of market pigs. To achieve breeding targets, gonadotrophins can be administered at weaning to stimulate estrus onset. The present study examined the impact of supplemental human chorionic gonadotrophin activity (i.e., hCG), during a follicular phase induced by a standard gonotrophin protocol (i.e., PG600), in both ovarian follicular development and fertility in multiparous sows. The results confirmed that supplemental hCG at 24 h after PG600 increased follicle growth and reduced the interval to ovulation, but also increased the incidence of follicle cysts and reduced pregnancy success.

Abstract

At weaning, 33 mixed parity Hypor sows received either an injection of 400 IU equine chorionic gonadotrophin and 200 IU human chorionic gonadotrophin (hCG) (PG600; n = 13), PG600 with an additional 200 IU hCG 24 h later (Gn800; n = 11), or served as non-injected controls (n = 9). All gonadotrophin treated sows received an injection of 750 IU hCG at 80 h after weaning to induce ovulation (designated as time 0 h). At 0, 24, 36, 40, 44, 48, and 60 h, all sows were subject to transrectal ultrasonography to determine numbers and sizes of large (>6 mm) follicles and time of ovulation. The interval from injection of 750 IU hCG to ovulation was shorter in Gn800 compared to PG600 sows (p = 0.02), and more Gn800 sows had ≥9 preovulatory follicles compared to PG600 and controls (p = 0.02 and 0.003, respectively). Follicular cysts were evident in both PG600 and Gn800 sows.

Effect of altering the ratio of exogenous gonadotropins on reproductive performance of primiparous sows during the seasonal infertility period

At weaning, 150 primiparous sows were assigned sequentially to receive 400 IU equine chorionic gonadotropin (eCG) with 200 IU human chorionic gonadotropin (hCG) (Gn600), or 400 IU eCG with 400 IU hCG (Gn800), or served as untreated controls. Compared with control and Gn600, the Gn800 had increased estrus response by day 7 and reduced wean-to-estrus intervals (P < 0.05). Compared with controls, both Gn600 and Gn800 increased numbers of large follicles (≥6 mm) at estrus detection (P < 0.05) and the subsequent farrowing rates (P < 0.05). Litter size was unaffected. These data demonstrate the efficacy of supplemental hCG for alleviating effects of seasonal infertility in primiparous sows.

Progesterone and pregnant mare serum gonadotropin improve the reproductive capacity of long-term non-oestrus replacement gilts

Context It is a common problem that replacement gilts exhibit delayed oestrus and non-oestrus in pig production. Aims This study explored the use of progesterone and pregnant mare serum gonadotropin (PMSG) to promote oestrus and to restore the reproductive capacity of sows. Methods A total of 90 long-term non-oestrus replacement gilts were randomly divided into three groups. Group A consisted of 30 sows that were normally fed for 20 days, followed by injections of 1000 IU of PMSG on the morning of the 21st day and 100 μg of gonadotropin-releasing hormone on the 24th day. Group B consisted of 30 sows that were continuously fed with altrenogest (20 mg/head.day) for 18 days, followed by injections of 1000 IU of PMSG on the morning of the 21st day and 100 μg of gonadotropin-releasing hormone on the 24th day. Group C (control group) consisted of 30 sows that were normally fed for 20 days, followed by injections of 3 mL of physiological saline on the morning of the 21st day and 3 mL of saline on the 24th day. Oestrus identification was performed in all three groups, and sows underwent artificial insemination after the injection of gonadotropin-releasing hormone or saline. Key results We found that the follicles of long-term non-oestrus replacement gilts were not developed, and follicle diameters were &lt;4 mm. The oestrus rate and pregnancy rate of the sows in Group B were significantly lower than those in Group A (30% vs 66.7% and 66.7% vs 90%) respectively. There was no difference in the litter size between Group A and Group B (11.2 vs 11.5). The sows in Group C exhibited no oestrus and no pregnancy. After treatment with progesterone and PMSG, the follicle diameters of sows in oestrus were significantly greater than those of sows in non-oestrus, and the levels of oestradiol, luteinising hormone and follicle-stimulating hormone were significantly higher than those of sows in non-oestrus. Conclusions This study showed that progesterone and PMSG treatment can alter the reproductive hormone levels and follicle diameters in long-term non-oestrus replacement gilts, promote oestrus and restore reproductive capacity in sows. Implications This study provides a method for the use of hormone-treated gilts to maximise the reproductive potential of gilts.

Seasonal infertility in gilts and sows: Aetiology, clinical implications and treatments

In gilts and sows, the summer-autumn period often is characterized by reduced fertility. Heat stress and long photoperiods during the warm season can cause a reduction in feed intake and an imbalance of the hypothalamic-hypophysial-ovarian axis. The increased variability in the interval between oestrus onset and ovulation results in an increased number of poorly timed inseminations. The altered endocrine activity compromises follicular and corpora luteal development, reduces oocyte quality and increases embryo mortality. This paper reviews current knowledge on the metabolic and endocrine mechanisms associated with seasonal infertility in gilts and sows and describes some pharmacological approaches that can be utilized to counter this infertility.

Effect of a GnRH analogue (peforelin) on the litter performance of gilts and sows

Background

Maintaining optimal reproductive and litter performance is essential for meeting economic targets in commercial pig production. Treatment with exogenous gonadotropins in sows after weaning or in gilts after altrenogest treatment has been used to stimulate follicular development leading to more piglets born and eventually higher birth weights. The effect of peforelin on litter performance was investigated in 212 gilts, primi- and pluriparous sows in three herds. Animals were randomly allocated to three treatments 24 h after weaning: peforelin (P group), eCG (E group), and physiological saline solution (C group). Numbers of total, liveborn and stillborn piglets and mortality rate during lactation were recorded. Birth weights and coefficient of variation in weights within litter were assessed. All parameters were compared among treatments.

Results

Over all parities, no difference was found among treatments in litter size nor mortality rate, but birth weights were significantly lower in the E group. Stillbirth numbers in pluriparous sows were 2.2, 0.9 and 1.4 for P, E and C groups, respectively (p = 0.04). Piglets in the P group had significantly higher live born birth weights in gilts, compared to the E group (1.36, 1.26, 1.32 kg (p < 0.02) for P, E and C group, respectively). No significant differences were found for the other investigated parameters.

Conclusions

Peforelin treatment showed no improvement of litter performance compared to no treatment.

Human chorionic gonadotrophin in early gestation induces growth of estrogenic ovarian follicles and improves primiparous sow fertility during summer

Reduced summer farrowing rates may be due to inadequate corpora luteal (CL) support. Porcine CL become dependent on LH from 12 d of pregnancy and the embryonic estrogen signal for maternal recognition of pregnancy (MRP) is initiated at about 11-12 d after insemination. We hypothesised that injection of the LH analogue human chorionic gonadotropin (hCG) would induce growth of estrogenic follicles and, by mimicking the signal for MRP and stimulating progesterone secretion, increase primiparous sow fertility. In Experiment 1, during a 28 d lactation 53 mixed parity sows were full-fed either throughout lactation (n=16) or until 18 d and then feed restricted during the last 10 d of lactation (n=36). At 12 d after mating restrict-fed sows were injected with 1000IU hCG (n=17) or were not injected (n=19); the full-fed sows acted as non-treated positive controls. Transrectal ovarian ultrasound exams were performed on days 12, 16, 20, 24, and 28; blood samples were obtained on days 12, 14, and 15 for estradiol and progesterone assay. For Experiment 2, during the summer months primiparous sows received 1000IU hCG 12 d after mating (n=28) or were non-injected controls (n=27). Pregnancy status was determined at 28 d and sows allowed to go to term to determine farrowing rates and litter sizes. In Experiment 1, injection of hCG increased (P<0.001) follicle diameter and serum concentrations of estradiol (P<0.01) and progesterone (P<0.05). There were no effects of lactation feeding level on wean-estrus interval, farrowing rate or subsequent litter size. In Experiment 2, hCG injection was associated with a higher pregnancy rate (P<0.05) and farrowing rate (P<0.08). There was no effect on litter size. These data confirm that hCG stimulates growth of estrogenic follicles and CL function, and improves primiparous sow fertility during the summer months.

An evaluation of gonadotropin-releasing hormone analogue administered to gilts and sows on subsequent reproductive performance and piglet birth weight

Background

The present study investigated the effect of peforelin (Maprelin®), a gonadotropin-releasing hormone (GnRH) analogue, administration in gilts, primiparous and pluriparous sows in a high productive farm on sow reproductive performance and piglet quality at birth.

Methods

In a 400 sow herd, gilts, primiparous and pluriparous sows were randomly allocated to 2 groups: peforelin treated (peforelin = P-group) or no treatment (control = C-group). Animals were injected 48 h after the last altrenogest treatment (gilts) or 24 h post weaning (sows). Weaning-to-estrus interval (WEI), estrus rate (ER), farrowing efficiency index (FEI), farrowing rate (FR), number of total (TBP), live (LBP) and stillborn piglets (SBP), mummies (MM) and live piglet index (LPI) were assessed and compared between treatment groups. To assess piglet quality at birth, 6033 piglets from 426 litters were weighed individually within 24 h after birth (BW; birth weight).

Results

No significant difference between treatment groups could be observed for WEI, TBP, LBP, SBP and MM. The ER was significantly (P = 0.0119) higher (93.2 %) in the P-group as compared to the C-group (87.2 %). Peforelin treatment did not affect farrowing rate. Both FEI and LPI were significantly (P = 0.0078) better in the P-group as compared to the C-group. Overall, no effect of peforelin treatment on piglet birth weight could be observed, although specific subcategories (1st parity and older (5+ parity) sows) did have a significant impact of treatment on birth weight. During late summer (August-September) all treated gilts and sows took advantage from peforelin treatment with a significant improvement of piglet birth weight.

Conclusion

Peforelin treatment had a significant impact on ER, FEI and LPI. Moreover, piglet birth weight improved for specific sow subcategories (1st parity and older sows) and for all gilts and sows during the late summer infertility period.

Pathological evaluation of reproductive system of porcine reproductive and respiratory syndrome virus-vaccinated and nonvaccinated anestrus sows and gilts

The purpose of the study was to evaluate pathologically the reproductive system of nonvaccinated and porcine reproductive and respiratory syndrome virus (PRRSV)-vaccinated sows/gilts, as well as the assessment of vaccination impact on their endometrium/myometrium and ovaries. In a farrow-to-finish farm, all sows and gilts were systematically vaccinated with a PRRSV-inactivated vaccine for a period of 18 months. During the last semester before the beginning of the trial, the genital organs (uterus and ovaries) from 50 females (nonvaccinated primiparous and multiparous sows that did not exhibit signs of estrus until 10 days post-weaning) were collected at the slaughterhouse for gross and microscopic examination (parity 1 to >6). Respectively, during the following three semesters after the implementation of the experimental PRRSV vaccination scheme, the genital organs from 75 vaccinated sows-25 samples taken along the period of each semester-were also collected. Gross examinations included measurements of uterine horn (thickness and diameter) and ovaries (diameter). Microscopic examination focused on histopathological examination of ovarian cysts or other cystic formations and evaluation of the endometrium and myometrium. Measurements of uterine horn's thickness/diameter and ovaries' diameter were at normal levels, and no significant differences were found on gross examination between vaccinated and nonvaccinated females. The results of histopathological examinations did not show lesions of endometritis or myometritis, but revealed ovarian cystic formations with a diameter of >2 cm that were luteinizing cysts. The presence of these luteinizing cysts was significantly lower in PRRSV-vaccinated animals, compared to nonvaccinated, three semesters (p=0.017) after the start of vaccinations and for the total trial period (p=0.009).

Effect of a GnRH analogue (Maprelin) on the reproductive performance of gilts and sows

The ability of peforelin (l-GnRH-III) to stimulate follicular growth, FSH release, and estrus in gilts after altrenogest treatment and in sows after weaning was investigated. In three farrow-to-wean herds, with at least 600 sows and average production performance, 216 gilts, 335 primiparous, and 1299 pluriparous sows were randomly allocated to three treatments: peforelin (M group: Maprelin), eCG (F group: Folligon), and physiological saline solution (C group). Animals were treated 48 hours after their last altrenogest treatment (gilts) or 24 hours after weaning (sows). The weaning-to-estrus interval, estrus duration, estrus rate (ER), pregnancy rate, and total born (TB), live born, and stillborn (SB) numbers were recorded and compared between treatments for the different parity groups (gilts and primiparous and pluriparous sows). Follicle sizes were measured in representative animals from each group on the occasion of their last altrenogest treatment or at weaning, and also on the occasions of their first (FS1) and second (FS2) attempted inseminations. Blood samples were taken to determine FSH concentrations at weaning and 2 hours after injection, and progesterone concentrations 10 days after the first insemination attempt. The relative change in FSH concentrations was calculated. Significant differences were found for ER within 7 days of weaning in pluriparous sows (95%, 91%, and 90% for the M, F, and C groups, respectively, P = 0.005). Gilts in the F-group had high TB numbers, and pluriparous sows in the M group had high SB numbers (TB gilts = 13.6, 15.4, and 14.9 [P = 0.02] and SB pluriparous sows = 1.8, 1.4, and 1.7 [P = 0.05] for the M, F, and C groups, respectively). The M group had the highest FS1 (for gilts) and FS2 (for pluriparous sows) values: FS1 = 5.4, 4.9, and 4.9 mm [P = 0.02] and FS2 = 6.8, 5.3, and 6.3 mm [P = 0.03] for the M, F, and C groups, respectively. There were no significant differences between the different treatments within each parity group with respect to any of the other variables. Overall, peforelin treatment had small but positive effects on the ER and follicle growth in certain parity groups but did not seem to affect litter sizes or FSH and progesterone levels in sows on the occasions of the corresponding examinations.