Consequences of different dietary energy sources during follicular development on subsequent fertility of cyclic gilts

The objective of the present study was to investigate the effects of dietary-induced insulin enhancement during the late luteal phase on subsequent fertility of gilts. Fifty-two littermate cyclic gilts were subjected to dietary treatments where two energy sources were tested: corn starch (T1) and soybean oil (T2). The experimental diets were supposed to provide similar amounts of dietary energy, but from different sources. Gilts were fed ad libitum, starting day 8 of the estrous cycle, until the next standing heat. Blood sampling was performed in a subgroup of 20 gilts on days 14 and 21 of the cycle for analyses of glucose and insulin, and after ovulation detection until 18 h after ovulation for progesterone. All gilts were slaughtered on day 28 of pregnancy and the reproductive tracts recovered for further analysis. T1 gilts showed higher postprandial insulin peak on days 14 and 21 and lower glucose levels 4 h after feeding on day 14 (P<0.05), however, there were no treatment effects on plasma progesterone concentrations. Dietary energy sources did not affect average daily feed intake, body weight and backfat on day 28 of pregnancy. Estrous cycle length, estrus duration and time of ovulation were not affected by previous nutritional treatments either. T1 gilts showed higher ovulation rates, number of embryos, embryo weight and placental weight (P<0.05). There were no treatment effects on pregnancy rate, embryo survival rate and volume of amniotic fluid. A positive correlation between progesterone concentration 18 h after ovulation and ovulation rate was observed (r=0.75; P<0.01). These results suggest that it is possible to manipulate dietary insulin response in cyclic gilts and, thus, improve reproductive efficiency when feeding starch as the main energy source during the late luteal and follicular phases of the cycle.     

Supplemental progesterone during early pregnancy exerts divergent responses on embryonic characteristics in sows and gilts

Progesterone (P4) plays a key role in pregnancy establishment and maintenance; during early pregnancy, P4 stimulates the production and release of uterine secretions necessary for conceptus growth prior to implantation; therefore, exogenous P4 supplementation may improve embryo development. This study evaluated the effects of supplementation during early pregnancy with long-acting injectable progesterone or altrenogest on embryonic characteristics of sows and gilts. Thus, a total of 32 sows and 16 gilts were used. On day 6 of pregnancy sows and gilts were allocated to one of the following groups: non-supplemented; supplemented with 20 mg of altrenogest, orally, from days 6 to 12 of pregnancy; supplemented with 2.15 mg/kg of long-acting injectable progesterone on day 6 of pregnancy. Animals were killed on day 28 of pregnancy, and ovulation rate, embryo survival, embryo weight, crown-to-rump length, uterine glandular epithelium and endometrial vascularization were assessed. Treatments had no effect on pregnancy rate, embryo survival or endometrial vascular density (P > 0.05). Non-supplemented gilts presented larger and heavier embryos compared to gilts from supplemented groups (P < 0.05). Sows in the altrenogest group presented larger and heavier embryos compared to non-supplemented sows and sows supplemented with long-acting injectable progesterone. In conclusion, supplementation of sows and gilts with progestagen from day 6 of pregnancy can be used as a means to improve embryo survival without deleterious effects.     

Effect of hCG administration at the onset of oestrus on early embryo survival and development in Meishan gilts

A study was designed to advance the time of the ovulatory luteinizing hormone (LH) surge in Meishan gilts by human chorionic gonadotrophin (hCG) administration at the onset of oestrus and assess the effect on embryo survival and development. Twelve Meishan gilts were observed six times daily for oestrous behaviour and bred at 24, 36 and 48 h after observed oestrous onset. Six of those gilts were administered an ovulatory dose of hCG (500 IU) at observed oestrous onset. Blood samples were collected at oestrous onset (Day —2) and on Days 0, 2, 6, 9, 13, 16, 20, 23, 27 and 30 of gestation. All gilts were slaughtered on Day 30 of gestation and embryo survival and conceptus development assessed. Ovulation rate did not differ between control and hCG treated gilts (18.5 and 17.7 respectively; P>0.1) while the number of live conceptuses per gilt (17.2 and 12.8 respectively; P<0.08) and embryo survival rate (92.1 and 75.8% respectively; P<0.1) both tended to be reduced by the hCG treatment. Placental weight (17.2 and 23.1 g; P<0.01) was significantly increased in hCG treated gilts, while embryo weight (1.2 and 1.4 g; P<0.06) and placental length (42.8 and 47.2 cm; P<0.07) both tended to be increased in hCG treated gilts. Crown rump length (P>0.1) and allantoic fluid volume (P>0.1) did not differ between the treatment groups. Serum progesterone concentrations did not differ with treatment overall (P>0.1) but were significantly elevated (P< 0.05) at 48 h postoestrus in the hCG treated gilts compared to control gilts. Overall, these results indicate that advancing the time of the LH surge to oestrous onset, as in European breeds, compromised embryo survival and suggests that the longer time interval between oestrous onset and ovulation is important for the high rate of embryo survival in the Meishan pig.     

Estrus synchronization affects WNT signaling in the porcine reproductive tract and embryos

The purpose of the study was to investigate an effect of estrus synchronization with prostaglandin (PG) F_2α and PMSG/hCG on WNT4, WNT5A, WNT7A, β-catenin (CTNNB1) and E-cadherin (CDH1) gene expression. The weight of the uterus, morphometrical parameters of the endometrium and the number of CL were recorded. The analysis of estradiol (E₂), prostaglandin (PG) F_2α and E₂ content in the uterine luminal flushings (ULFs) and progesterone (P₄) level in the blood serum were conducted. RNA was isolated from endometrial, luteal and embryonic tissue of pregnant non-synchronized (Control; n = 15) and pregnant synchronized (PGF_2α/PMSG/hCG; n = 15) pigs. Whereas there was no change in uterine weight, differences in height of endometrial surface and glandular epithelium were found. However, height of the endometrium, number of the glands and capillaries were unaffected. The total number of the CLs was higher (P < 0.05) in animals treated with PGF_2α/PMSG/hCG. The amount of E₂ and P₄ was lower (P < 0.05, P < 0.001, respectively) in pregnant gilts administrated with PGF_2α/PMSG/hCG. The concentration of PGF_2α in ULFs was not affected by hormonal management, while PGE₂ was higher (P < 0.01) in hormonally in comparison to non-hormonally treated pigs. The content of WNT4 mRNA in conceptuses increased on particular Days studied in Control and PGF_2α/PMSG/hCG administered animals. WNT7A and CTNNB1 were affected by PGF_2α/PMSG/hCG treatment in both conceptuses (P < 0.001, P < 0.05) and endometrial tissue (P < 0.001, P < 0.01). The PGF_2α/PMSG/hCG treatment resulted in elevated expression of WNT4 (P < 0.001) and CTNNB1 (P < 0.05) in luteal tissue in comparison to the Control gilts. Moreover, luteal amount of WNT5A mRNA was higher in PGF_2α/PMSG/hCG animals in comparison to the Control group (P < 0.05). Presented data show that exogenous hormones administration can affect gene expression in the porcine reproductive tract and embryo.     

Attainment of puberty in female pigs: Influence of boar stimulation

The object of the present study was to investigate whether the presence of a boar is of importance for the age at puberty and the expression of external heat symptoms in female pigs. Altogether 60 crossbred gilts were purchased at an age of 12 weeks and grouped, three or four per pen, in three separate barns (treatment groups A, B and C). Treatment group A: Boars were kept in adjacent pens to the gilts during the whole period. One vasectomized boar was penned with the gilts daily for 20 min during the experimental period, which started at a mean age of 142 days. Treatment group B: Boars were kept in adjacent pens to the gilts during the whole period. Treatment group C: No boars were kept in the barn at any time.The study was performed six times. Daily heat control was carried out during the experimental period, which was terminated when the gilts had passed at least two oestrous cycles. Blood samples for progesterone analysis were taken once a week. Laparoscopy was performed in all gilts after their first observed heat. The gilts were slaughtered after their third or fourth heat. The effects of treatment group were estimated by the method of least squares analysis.All gilts except one showed external heat symptoms at regular intervals during the experimental period. A few gilts did not stand for the boar at each oestrous period, regardless of oestrous number. Gilts belonging to group A showed their first oestrus on average 20 days earlier than gilts in group B and 35 days earlier than gilts in group C. These differences were highly significant (P < 0.001). The stimulatory effect of the boar on the age at puberty varied between the six experimental groups and the interaction between treatment and experimental groups was significant (P < 0.01).     

Estrus synchronization affects WNT signaling in the porcine reproductive tract and embryos

The purpose of the study was to investigate an effect of estrus synchronization with prostaglandin (PG) F_2α and PMSG/hCG on WNT4, WNT5A, WNT7A, β-catenin (CTNNB1) and E-cadherin (CDH1) gene expression. The weight of the uterus, morphometrical parameters of the endometrium and the number of CL were recorded. The analysis of estradiol (E₂), prostaglandin (PG) F_2α and E₂ content in the uterine luminal flushings (ULFs) and progesterone (P₄) level in the blood serum were conducted. RNA was isolated from endometrial, luteal and embryonic tissue of pregnant non-synchronized (Control; n = 15) and pregnant synchronized (PGF_2α/PMSG/hCG; n = 15) pigs. Whereas there was no change in uterine weight, differences in height of endometrial surface and glandular epithelium were found. However, height of the endometrium, number of the glands and capillaries were unaffected. The total number of the CLs was higher (P < 0.05) in animals treated with PGF_2α/PMSG/hCG. The amount of E₂ and P₄ was lower (P < 0.05, P < 0.001, respectively) in pregnant gilts administrated with PGF_2α/PMSG/hCG. The concentration of PGF_2α in ULFs was not affected by hormonal management, while PGE₂ was higher (P < 0.01) in hormonally in comparison to non-hormonally treated pigs. The content of WNT4 mRNA in conceptuses increased on particular Days studied in Control and PGF_2α/PMSG/hCG administered animals. WNT7A and CTNNB1 were affected by PGF_2α/PMSG/hCG treatment in both conceptuses (P < 0.001, P < 0.05) and endometrial tissue (P < 0.001, P < 0.01). The PGF_2α/PMSG/hCG treatment resulted in elevated expression of WNT4 (P < 0.001) and CTNNB1 (P < 0.05) in luteal tissue in comparison to the Control gilts. Moreover, luteal amount of WNT5A mRNA was higher in PGF_2α/PMSG/hCG animals in comparison to the Control group (P < 0.05). Presented data show that exogenous hormones administration can affect gene expression in the porcine reproductive tract and embryo.     

Relationship of length of uterus in prepubertal pigs and number of corpora lutea and fetuses at 30 days of gestation

Relationships of the length of the uterus at one reproductive stage to the length at other stages and the effect on potential litter size were determined. In Experiment 1, the length of the uterus was measured in situ at 20, 60, or 100 days of age at laparotomy with 20 gilts in each of the three age groups. Forty days after the initial measurement, the uterus was again measured in situ, gilts were ovariectomized and hysterectomized, and associations among uterine measurements at the two different stages were determined. Correlations between uterine length in situ and between uterine length and weight 40 days later were all greater than 0.75 (P < 0.001). The length of one uterine horn increased from 13.9 cm at 20 days of age to 36.7 cm at 140 days of age (P < 0.01). In Experiment 2, 66 gilts were unilaterally hysterectomized and ovariectomized (UHOX) at 150 days of age and the ovary was weighed. Length of the one horn was measured in 36 gilts. At 10 days after first estrus, the length of the remaining uterine horn was measured at laparotomy and corpora lutea were counted in 53 gilts. In 15 of the 53 gilts the remaining uterine horn was removed to obtain uterine weights. At the second or third estrus, 38 gilts were mated and at Day 30 of gestation, 31 gilts were pregnant. The gilts were killed, and the length of the uterus measured and corpora lutea (CL) and fetuses were counted. The length of one uterine horn at 150 days of age was 70 cm with a range of 47–110 cm. At 10 days after first estrus, length had increased to a mean of 141 cm with a range of 86–194 cm and at 30 days of gestation the mean was 244 cm with a range of 186–311 cm. There were 12.2 CL at first estrus, which was not different from 12.4 CL at the second or third estrus. The mean number of fetuses in one horn at 30 days of gestation was 9.5 with 77% prenatal survival. Length of uterine horn at 150 days of age was correlated with uterine horn length (r = 0.56, P < 0.001) at 10 days after first estrus and number of live fetuses (r=0.39, P<0.05) at 30 days of gestation. At Day 10 after first estrus, uterine length was not correlated with the number of CL, whereas at Day 30 of gestation, the number of CL and uterine length were correlated with the number of live fetuses in those gilts with below the mean number of live fetuses, but not in those gilts with above the mean of live fetuses. The number of live fetuses (r=0.66, P < 0.001) and fetal survival (r=0.63; P < 0.001) were correlated with uterine horn length in pregnant UHOX gilts. Length of the prepubertal uterus gives an indication of postpubertal length and the potential litter size in pigs.     

Effect of estrus induction on prostaglandin content and prostaglandin synthesis enzyme expression in the uterus of early pregnant pigs

Prostaglandins (PGs) play a pivotal role in maternal recognition of pregnancy and implantation in pigs. In the present study, PGE₂, PGF_2α, and PGFM (PGF_2α metabolite) content, as well as PGE₂ synthase (mPGES-1) and PGF_2α synthase (PGFS) expression was investigated in early pregnant gilts with natural (n = 21) and PMSG/hCG-stimulated (n = 19) estrus. Endometrial tissue samples, uterine luminal flushings (ULFs), and blood serum were collected on days 10-11, 12, and 15 after insemination. Additionally, day 15 conceptuses were collected for mPGES-1 and PGFS protein expression. Effect of estrus induction was observed on day 15 of pregnancy, when the content of PGE₂ in the uterine lumen was fourfold lower in gonadotropin-stimulated gilts in comparison to controls (P < 0.001). Decreased PGE₂ content in ULFs of gonadotropin-treated pigs was preceded by lower endometrial mPGES-1 gene expression in hormonally-stimulated animals in comparison to control gilts (P < 0.01). On the other hand, estrus induction with PMSG/hCG resulted in higher PGE₂ accumulation in the endometrial tissue on day 15 of pregnancy (P < 0.01). Furthermore, PGF_2α content in the endometrium and PGFM levels in blood serum were lower in gonadotropin-treated gilts, especially on day 12 after insemination when compared to control gilts (P < 0.01). Finally, PGFS expression in day 15 conceptuses was decreased in animals with hormonally-induced estrus. We conclude that PMSG/hCG stimulation of prepubertal gilts to induce estrus results in changes of PG production and secretion during early pregnancy, which, in turn, may affect conceptus development, implantation, and the course of pregnancy.     

Equine chorionic gonadotropin pretreatment 15 days before fixed-time artificial insemination improves the reproductive performance of replacement gilts

Fixed-time artificial insemination (FTAI) technology uses exogenous reproductive hormones to regulate the sexual cycle and ovulation of sows without oestrus identification, which improves the sow breeding utilisation rate, reduces the number of non-productive days, and elevates the efficiency of pig farm management. In this study, we aimed to optimise FTAI procedures. Healthy 190-day-old and about 90 kg Large White × Landrace crossing breed replacement gilts (n = 166) which were of unknown reproductive status were randomly selected and divided into three groups: a control group (n = 62), an eCG-15D group in which the gilts were pretreated with equine chorionic gonadotropin (eCG) injection 15 days before starting FTAI (n = 50), and an eCG-20D group pretreated with eCG injection 20 days before starting FTAI (n = 54). All three groups were then subjected to the same conventional FTAI procedure. Pigs were orally administered Altrenogest (ALT, 20 mg per pig per day) for 18 days and then 42 h after ALT feeding was stopped, they were injected with 1 000 IU eCG followed by 100 μg GnRH 80 h later. The gilts were inseminated for the first time 24 h after gonadotropin-releasing hormone (GnRH) injection and then again 16 h later. After 42 h of ALT feeding, gilts in the eCG-15D group displayed a higher follicular diameter until artificial insemination (AI) than those from the other groups (P < 0.05). In addition, the ovulation times were the most synchronised in the eCG-15D group, with 100% of the gilts ovulating before the second AI on day 25 of FTAI. Furthermore, the gilts in the eCG-15D group achieved the highest pregnancy rate (92%), farrowing rate (90%), total pigs born (11.59), and pigs born alive (11.18). Together, the findings of this study demonstrate that reproductive performance can be optimised by pretreating gilts with eCG 15 days before conventional FTAI.     

Synchronization of oestrus in gilts with altrenogest: effects on ovulation rate and foetal survival

Previous studies have shown that use of altrenogest resulted in a high rate of fertility and increased litter size compared with controls under conditions of practical pig production. The present study was designed to evaluate whether ovulation rate and/or foetal survival were increased by altrenogest using crossbred gilts derived from one herd (n = 227) and introduced in the same piggery over 12 months. Each gilt was allocated to a treated group (n = 103) receiving an individual daily dose of 20 mg of altrenogest for 18 days in its feed or a control group (n = 124) after puberty had been diagnosed, (197 ± 1 day; mean ± SEM). They were inseminated (double AI) at the second induced or natural oestrus. Pregnancy was diagnosed by ultrasonography at Days 22 and 42 post-insemination in the absence of return to oestrus. Pregnant gilts were slaughtered at 48 ± 3 days of pregnancy following the second examination. The number of living and dead foetuses were recorded before uterine contents (foetuses and placentae) were weighed and the number of corpora lutea (CL) per ovary counted.Precise synchronization of oestrus was observed after the end of the progestogen administration, with 93% of the gilts in oestrus by Days 5 to 7. For the controls, the interval from first to second oestrus ranged from 17 to 25 days in 93% of the control gilts. The pregnancy rate was 89.3% for treated gilts and 77.4% for controls (P < 0.05). The ovulation rate was increased by the treatment (15.4 ± 0.3 vs 14.6 ± 0.3; mean ± SEM, P < 0.02). Although the altrenogest group had more foetuses (11.1 vs 10.6), this difference was not significant (P > 0.14). The percent of foetal survival was similar in both groups (64.9%; P > 0.27). The foetal and placental weights differed only between dams and increased with stage of gestation. The increase in litter size through feeding altrenogest was associated with an increased ovulation rate.     

Sexual maturation and morphological development of the reproductive tract in large white and prolific Chinese Meishan pigs

Body weight of Large White gilts was greater at birth, weaning, 5 months of age and at slaughter; however, Meishan gilts reached puberty at an earlier age (91 +/- 2 vs 192 +/- 3 days, P less than 0.01), had longer periods of oestrus (60 +/- 2 vs 49 +/- 2 h, P less than 0.01) and experienced more oestrous cycles (7 +/- 0.4 vs 4 +/- 0.4, P less than 0.01) before slaughter. The interoestrous interval was longer (P less than 0.01) for Large White gilts (19.8 +/- 0.2 vs 19.1 +/- 0.2 days). At slaughter, uterine length (P less than 0.05), uterine weight, width of uterine horns, endometrial surface area, endometrial weight and percentage of uterine weight represented by endometrium was greater (P less than 0.01) for Large White gilts. However, breed differences were not significant when slaughter weight was included in analyses as a covariate. This indicated that development of the reproductive tract was proportionate to body weight at slaughter for each breed. When body weight at slaughter was included as a covariate, effects of day of the oestrous cycle and pregnancy on uterine width, uterine weight, endometrial surface area and endometrial weight were detected (P less than 0.01) and for uterine length there was a day-by-status interaction (P less than 0.01). Total number of CL (P less than 0.05) and total ovarian weight (P less than 0.05) were also greater for Large White gilts independent of body weight at slaughter. There were more CL in left ovaries for Meishan (8.1 +/- 0.4 vs 6.6 +/- 0.4) and Large White (8.4 +/- 0.4 vs 7.9 +/- 0.5) gilts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Management practices associated with reproductive performance in Holstein cows on large commercial dairy farms

As a result of the increase in herd size and the intensification of production, the complexity of reproductive management has been growing in dairy herds. The aim of our study was to examine the associations of management practices and reproductive performance in Holstein cows on large commercial dairy farms. Management practices applied to cows were surveyed between 22 May and 6 November 2015 in 34 large Holstein-Friesian dairy herds in Hungary. Individual data of 23 784 cows that calved between 1 January 2014 and 31 December 2014 in the surveyed herds were gathered. Associations between the management practices and the reproductive parameters were analyzed by mixed effects models. Regarding heat abatement we found that ventilation with sprinklers was associated with the shortest breeding interval (P<0.01), the shortest calving to conception interval (P<0.01), and the highest odds of being pregnant by 200 days in milk (P<0.01). Solely ventilation showed similar (P>0.05) results to lack of heat stress protection. It was also revealed, that lack of a well-established voluntary waiting period (VWP) or a VWP shorter than 50 days was associated with less days to first service (P<0.01), shorter breeding interval (P<0.01) and calving to conception interval (P<0.05), as well as higher odds of carrying a calf by 200 days in milk (P<0.01) compared with those using a VWP of at least 50 days. Those farms that applied transrectal ultrasonography were more likely to use ventilation with sprinklers (P<0.05), hormonal synchronization (P<0.01) and to perform early pregnancy diagnosis followed by pregnancy recheck (P<0.05). The application of transrectal ultrasonography with one of the aforementioned practices was associated with reduced days to first service (P<0.05), shorter breeding interval (P<0.05) and higher odds of pregnancy at 200 days in milk (P<0.05). Our study highlights the management practices most closely related to improved reproductive performance, which are, therefore, suggested to be applied on dairy farms, considering the local circumstances of the individual farms.     

The influence of handling by humans on the behaviour,reproduction and corticosteroids of male and female pigs

The influence of three handling treatments on the behaviour, reproduction and free corticosteroid concentrations was studied in 15 male and 30 female pigs. Two handling treatments, considered as pleasant and unpleasant, were imposed for 5 min, three times per week from 11 weeks of age. The third handling treatment involved minimal contact with humans from 11 weeks of age. In a 3-min test at 18 weeks, pigs in the pleasant treatment were quicker (P<0.01) to enter an area within 0.5 m of the experimenter and had more interactions (P<0.05) with the experimenter than pigs in the unpleasant and minimal treatments. Gilts in the unpleasant treatment had a lower (P<0.05) pregnancy rate at the second oestrus when mated to non-experimental boars than gilts in the pleasant treatment (33.3 and 87.5%, respectively). Boars in the unpleasant treatment had smaller (P<0.05) testicles at 23 weeks of age and attained a coordinated mating response at a later age (P<0.05) than boars in the pleasant treatment (53.2 and 63.3 cm², and 192 and 161 days, respectively). In addition, pigs in the unpleasant treatment had higher (P<0.05) free corticosteroid concentrations in the absence of humans at 20 weeks (gilts) and 27 weeks (boars) than pigs in the pleasant treatment (boars and gilts combined, 2.4 and 1.7 ng ml⁻¹, respectively). For many of the reproductive parameters, the effect of the minimal handling treatment was intermediate to that of the other two treatments. It was concluded that the unpleasant handling treatment resulted in a chronic stress response, with consequent adverse effects on reproduction.     

Maternal backfat depth in gestating sows has a greater influence on offspring growth and carcass lean yield than maternal feed allocation during gestation

A commercial pig spends nearly half of its life in utero and its nutrition during this time can influence birth weight and postnatal growth. We hypothesised that postnatal growth is increased in pigs raised by sows with a high backfat depth and high level of energy intake during gestation compared with sows with a low backfat depth and low level of energy intake during gestation. This was tested in a 2×3 factorial design experiment with 2 factors for gilt backfat depth (Thin and Fat) and 3 factors for gestation feed allowance (Restricted, Control and High). Between d 25 and d 90 of gestation, Thin gilts (n=68; 12±0.6 mm P2 backfat) and Fat gilts (n=72; 19±0.6 mm P2 backfat) were randomly allocated, as individuals, to a gestation diet (6.19 g/kg lysine, 13.0 MJ DE/kg) at the following feed allowances: 1.8 kg/day (Restricted); 2.5 kg/day (Control) and 3.5 kg/day (High). For the remainder of gestation and during lactation all gilts were treated similarly. At weaning (day 28), 155 piglets were sacrificed and 272 were individually housed and followed through to slaughter (day 158). At day 80 of gestation, fasted Thin Restricted gilts had lower serum IGF-1 concentrations than Thin High or Thin Control fed gilts (P<0.001). Pigs born from Fat gilts had greater backfat depths (P<0.05), a lower lean meat yield (P<0.05) and were heavier (P<0.05) at slaughter than pigs born from Thin gilts. Gilt gestation feed allowance had only transitory effects on average daily gain and feed conversion efficiency and had no effect on pig weight at slaughter (P>0.05) or lean meat yield (P>0.05). In conclusion, gilts with a backfat depth of ~19 mm at insemination produced pigs that were heavier and fatter at ~158 days of age than those born from gilts with ~12 mm backfat depth at insemination. Maternal body condition during gestation had a more predominant influence on growth parameters of the offspring, such as weight at slaughter and backfat depth, than did feed level during gestation.     

Behavioural,endocrine and immune responses to repeated social stress in pregnant gilts

Pregnant sows are exposed to various stressors in intensive pig husbandry that may have negative consequences on their health, reproductive performances and welfare. Social stress is one of these challenges, because gestating sows have to be housed in groups according to EU guidelines (2001/88/CE). The purpose of this study was to determine the consequences of repeated social stress in pregnant female pigs on their behavioural, endocrine and immunological responses and on pregnancy outcome. Pregnant gilts were submitted to a repeated social stress procedure induced by housing unfamiliar gilts in pairs changed twice a week between days 77 and 105 of gestation (S group, n = 18). Control gilts were housed in stable pairs during the same period (C group, n = 18). Agonistic behaviour was observed during the first 3 h after each grouping. Skin lesions were numbered 2 h after each grouping. Salivary cortisol was measured before and repeatedly during the 4 weeks of grouping. Gilts were immunized against keyhole limpet haemocyanin (KLH) on days 81 and 95 of gestation. Immunoglobulins G against KLH, proliferative responses to concanavalin A, lipopolysaccharide, pokeweed mitogen and KLH and peripheral blood leukocyte numbers were evaluated 1 week before the first grouping and 3 days after the last one. Agonistic interactions and skin lesions were observed in S gilts at each grouping, although there was a decline between the first and the last grouping (P < 0.05). The repeated social stress induced a sustained endocrine response as shown by elevated salivary cortisol levels from 1 to 48 h after grouping in S gilts compared to C gilts. The cellular as well as the humoral immunity and the leukocyte numbers were not influenced by social stress. Gestation length tended to be shorter in S gilts (P = 0.09), but litter size, piglet weight or mortality at birth were not affected. Variability of the response of S gilts to groupings was partly explained by their average success value determined according to the outcome (defeat or win) of all the groupings. In conclusion, our study demonstrates that the application of repeated social stress to pregnant gilts during the last third of their gestation repeatedly activates their hypothalamo–pituitary–adrenal axis but does not impair their immune function and pregnancy outcome.     

The effect of tumor necrosis factor α (TNFα), interleukin 1β (IL1β) and interleukin 6 (IL6) on endometrial PGF2α synthesis, metabolism and release in early-pregnant pigs

Cytokines produced by the porcine uterus and embryos may be involved in the regulation of endometrial prostaglandin synthesis, metabolism, and release. We studied the effect of tumor necrosis factor α (TNFα), interleukin 1β (IL1β) and interleukin 6 (IL6) on: 1) endometrial release of prostaglandin F₂α (PGF₂α), 2) expression of the terminal enzyme of PGF₂α synthesis - PGF synthase mRNA (PGFS mRNA), 3) secretion of PGF₂α metabolite - 13,14-dihydro-15-keto PGF₂α (PGFM) by the endometrium and 4) presence and activity of endometrial NAD-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). The effects of cytokines were determined on days 10-11 and days 12-13, e.g., before and during maternal recognition of pregnancy, and on days 15-16, e.g., during the peri-implantation period and compared with its effect in cyclic gilts on corresponding days of the estrous cycle. TNFα did not affect endometrial release of PGF₂α in pregnant and cyclic pigs. IL1β enhanced endometrial PGF₂α release on days 12-13 and 15-16 in pregnant and cyclic pigs, respectively. IL6 increased PGF₂α release mainly on days 15-16 of pregnancy. Expression of PGFS mRNA was decreased by IL1β on days 12-13 of pregnancy (P < 0.05) and increased in response to IL1β, TNFα and IL6 on 12-13 (P < 0.05) and 15-16 (P < 0.01) of the estrous cycle. IL1β increased release of PGFM in gravid pigs on days 12-13, 15-16 and in non-gravid pigs 10-11 and 15-16 of the cycle. On days 15-16 of pregnancy TNFα and IL6 increased endometrial secretion of PGFM. We determined that in porcine endometrium NAD-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is present. In gravid pigs, the highest expression of endometrial 15-PGDH occurred during days 12-13 of pregnancy, while in non-gravid pigs during days 10-11 of the estrous cycle. These data provide new evidence that TNFα, IL1β, IL6 are involved in the regulation of endometrial synthesis, release and metabolism of PGF₂α to protect CL during early pregnancy or to facilitate its regression in cyclic females.     

Supplementary corpora lutea monitoring allows progestin treatment interruption on day 70 of pregnancy in non-cyclic recipient mares

The present study evaluated the effect of altrenogest treatment during 70 or 120 days of gestation on pregnancy maintenance in non-cyclic recipient mares and correlated the hormonal interruption findings with number, supplementary corpora lutea (SCL) formation period, and plasma progesterone (P4). Twenty five mares were used as recipients during anestrus, transitional or ovulatory phase and were assigned into groups according to altrenogest treatment period (70ALT, 120ALT or Control groups) or reproductive status at beginning of treatment (Anestrus, Transition or Cyclic/Control groups). Mares were evaluated by ultrasonography and quantification of plasma progesterone to monitor pregnancy status, SCL formation and P4 profile. After hormonal withdrawal, abortion was only observed on group 70ALT. The days of first SCL formation were similar (p = 0.32) in the 70ALT and 120ALT groups and greater (p < 0.01) than the Control group. In addition, the first SCL formation period occurred later during gestation in the anestrus group than in the transitional or cyclic mares. Progesterone synthesis in non-cyclic mares occurred in more advanced gestational period and showed lower concentration during the 120 days in relation to cyclic mares. It is suggested that progestin treatment interruption in non-cyclic recipient mares at 70 days of gestation allows pregnancy maintenance when SCL are observed and at 120 days enables maintenance in all recipient mares. In addition, the first SCL development period occurs in different gestational phases during pregnancy among anestrus, transitional and cyclic mares. This study improves the understanding of pregnancy physiology and enables progestins treatment interruption on day 70 of pregnancy in non-cyclic pregnant recipient mares.     

Influence of repeated regrouping on reproduction in gilts

It is generally assumed that stress around oestrus and during early pregnancy reduces reproductive performance of pigs. In our experiment, late prepuberal gilts (age at arrival 225+/-6 days) were housed in groups of four. Stress treatment consisted of once weekly regrouping and twice weekly feed competition of the 28 Stress gilts during 6 consecutive weeks, starting 13 days after arrival. Control gilts (n=28) were not treated. During the 0.5-1.5h after regroupings, Stress animals fought consistently more than the Control animals; up to 13 of the Stress animals fought for at most 60% of the time compared to one Control animal fighting for at most 3.3% of the time. The day before first regrouping, gilts had on average 4.0+/-0.9 skin scratches. By week 6, this number had reduced to 2.1+/-1.0 in Control, but remained 4.0+/-1.3 in Stress gilts (P<0.05). In the afternoon after regroupings, skin scratches increased up to 6.3+/-1.6 in the Stress gilts. Saliva cortisol in the afternoon before regrouping did not differ between weeks 1, 3 and 6, nor did it differ between Stress and Control. In Stress gilts, saliva cortisol was increased in the afternoon of first regrouping, in Batch 2 only (from 1.8+/-0.4 to 4.1+/-0.9 ng/ml; P<0.05). Animals showing a second oestrus within 5 weeks after arrival were inseminated. Duration of second oestrus of these animals was 2.48+/-0.66 days in the Stress gilts (n=24) and 2.21+/-0.58 days in the Control gilts (n=22; P>0.10). At Day 35 after insemination, pregnancy rate was 100% in both groups. Ovulation rate and number of total and vital fetuses was similar (P>0.10). The Stress treatment during a 6-week period around insemination consistently resulted in fighting but did not result in long term effects on cortisol levels and did not impair reproductive performance.     

The effects of post-weaning progestagen treatment (Regumate) of early-weaned primiparous sows on subsequent reproductive performance

This study investigated the effects of feeding the orally active progestagen, altrenogest (Regumate) post-weaning on the subsequent reproductive performance of early weaned sows. Ninety (90) Large White/Landrace first parity sows were randomly assigned to three treatments. Treatment 1 (EW) and treatment 3 (CW) sows were weaned on day 12 and day 24 post-partum, respectively while treatment 2 sows (EW-R) were weaned on day 12 post-partum and received an individual daily dose of 20 mg of Regumate on days 13 to 24 post-partum inclusive. Each sow was mated naturally at least twice at the first post-weaning or post-treatment oestrus and slaughtered on days 25–28 of pregnancy to determine the number of corpora lutea and embryos. Regumate-to-oestrus and weaning-to-oestrus intervals were similar for EW-R and CW sows (6.2 vs. 5.6 days). However, both intervals were significantly shorter (P<0.01) than the weaning-to-oestrus interval of EW sows (7.3 days). An excellent synchronization of oestrus was achieved with Regumate treatment with 97% of treated sows in oestrus within 7 days of Regumate withdrawal compared with 64% for EW sows (P<0.01) and 87% for CW sows (P>0.05). Treatment with Regumate resulted in a significant increase in ovulation rate (16.9 vs. 15.4 and 14.9 for treatments EW-R, EW and CW, respectively; P<0.05) and a non-significant increase in early embryonic survival (77% vs. 68% vs. 68% for treatments EW-R, EW and CW, respectively; P>0.05). These results indicate that Regumate feeding is a potential management tool to alleviate the diminished reproductive performance associated with early weaning regimes since it leads to successful control of oestrus, higher ovulation and embryo survival rates and thus a greater potential litter size.     

Plasma progesterone concentration in relation to ovulation rate and embryo yield in Chios ewes superovulated with PMSG

The main purpose of this work was to investigate the relationship between plasma progesterone concentration and the number of ovulations and/or the number of embryos collected from Chios ewes induced to superovulate with various doses of PMSG.The oestrous cycles of the animals were synchronized by means of MAP intravaginal sponges for 14 days and PMSG was injected i.m. (1500 IU, Group 1; 1000 IU, Group 2; 750 IU, Group 3; 500 IU, Group 4; 0 IU, Group 5) at the time of sponge withdrawal. Seven days after sponge removal and 5 days after mating, mid-ventral laparotomy was performed and the uterine horns and/or oviducts were flushed. The number and diameter of corpora lutea (CL), the number of large (diameter > 0.5 cm) anovulated follicles and the total ovarian response (TOR = CL + large anovulated follicles) were recorded. The embryos were examined under a dissecting microscope and evaluated according to morphological criteria. Blood samples were collected once daily for 4 days starting on the day of sponge withdrawal. One more sample was taken on the day of embryo collection. Progesterone concentration was determined using a conventional ELISA.A significant positive correlation was found between plasma progesterone concentration and number of corpora lutea (r = 0.61, P < 0.001), total diameter of corpora lutea (r = 0.63, P < 0.001), total ovarian response (r = 0.63, P < 0.001), number of eggs (r = 0.51, P < 0.001), number of embryos (r = 0.43, P < 0.001) and number of transferable embryos (r = 0.36, P < 0.01) collected per ewe treated. A negative relation between progesterone concentration (≥ 2 ng ml⁻¹) at the beginning of oestrus and number of corpora lutea (CL) was observed. The investigation of the relationship between ovulation rate and plasma progesterone concentration on the day of embryo collection resulted in the calculation of a formula for the prediction of the response of Chios sheep after superovulation with the specific hormonal regimen.