Influence of perioestrous suprabasal progesterone levels on cycle length,oestrous behaviour and ovulation in heifers

In order to induce suprabasal plasma concentrations of progesterone after luteolysis and to determine their effect on oestrous behaviour and ovulation, heifers subcutaneously received silicone implants containing 2.5 (n = 4), 5 (n = 4), 6 (n = 3), 7.5 (n = 3) or 10 (n = 4) g of progesterone, or an empty implant (controls, n = 5) between days 8 and 25 of the cycle (ovulation designated Day 0). Growth of dominant follicles and time of ovulation were determined by ultrasound, and signs of oestrus were recorded and scored. Blood was collected at 2–4 h intervals from Days 15 to 27 and assayed for progesterone concentration. In all heifers, plasma concentrations of progesterone sharply decreased during Days 16–18. Control heifers had their lowest progesterone levels on Days 20.5 and 21, standing oestrus on Day 19.5 ± 0.4 (mean ± SEM), and ovulated on Day 20.7 ± 0.4. A similar pattern was observed in heifers treated with 2.5 and 5 g progesterone. Heifers treated with 6, 7.5 and 10 g of progesterone showed an extended (P < 0.05) interovulatory interval. Onset of prooestrus and time of maximum expression of signs of oestrus were not significantly different from those in controls. However, there was an absence of standing oestrus in most of the cases, signs of oestrus lasted longer (P < 0.05) and were weaker in intensity when doses increased. In these groups, the lowest progesterone concentrations were attained shortly after implant removal. Some heifers treated with 6 and 7.5 g of progesterone had standing oestrus and post oestrous bleeding as seen in the controls but ovulation occurred from Days 24.5 to 27. When plasma progesterone concentrations were over 1 nmol 1⁻¹, disturbed oestrus and delayed ovulation occurred. The extended period of prooestrus and oestrus and delayed ovulation were similar to that described in cases of repeat breeding. It is suggested that suprabasal plasma concentrations of progesterone, after luteolysis, may lead to asynchrony between onset of oestrus and ovulation and consequently be a cause of repeat breeding in cattle.     

Reproductive performance of heifers induced to oestrous asynchrony by suprabasal plasma progesterone levels

Suprabasal progesterone concentrations around oestrus have induced disturbances in oestrous behaviour and ovulation. To determine whether fertility in such an altered oestrus can be maintained at normal levels with additional inseminations (AI) until ovulation, fertility was compared in heifers (n = 11) inseminated in normal oestrous cycles and thereafter in cycles in which the animals were treated with progesterone in order to create suprabasal concentrations after luteolysis. The treatment consisted of silicone implants containing 10.6 mg kg⁻¹ of progesterone inserted subcutaneously on Day 8 of the oestrous cycle (day of ovulation designated Day 0) and removed on Day 25. Both in control oestrous cycles and oestrous cycles under progesterone treatment, growth of the ovulatory follicle and ovulation were determined by frequent ultrasound scanning. Blood was collected frequently for further analysis of progesterone, oestradiol-17β and luteinising hormone (LH). Insemination was performed 12 h after onset of standing oestrus. if ovulation did not occur 24 h after AI, heifers were inseminated again until ovulation. Pregnancy was diagnosed by ultrasound 25 days after ovulation.In control oestrous cycles, plasma progesterone decreased to 0.3 ± 0.3 nmol 1⁻¹. Duration of oestrus was 22.9 ± 2.0 h, the interval from onset of oestrus to ovulation was 32.4 ± 2.3 h and the interval from LH peak to ovulation was 28.6 ± 1.4 h. The interovulatory interval was 20.7 ± 0.6 days. In oestrous cycles in treated heifers, progesterone decreased to 1.0 ± 0.3 nmol l⁻¹ (P > 0.10) and the interovulatory interval was prolonged to 23.5 ± 1.0 days (P < 0.05). Standing oestrus lasted 47.2 ± 12.0 h (P = 0.09, n = 7). The interval from the onset of oestrus to ovulation was 59.4 ± 13.0 h (P = 0.08) and the interval from LH peak to ovulation 25.8 ± 1.3 h (P > 0.10). The prolonged oestrus was associated with increased (P < 0.05) growth of the ovulatory follicle and higher (P < 0.05) release of oestradiol-17β. Conception rates were 90% and 46% (P < 0.05), and the numbers of AI per heifer were 1.1 ± 0.1 and 3.4 ± 0.6 (P < 0.01) for control oestrous cycles and after treatment, respectively.The induction of suprabasal concentrations of progesterone caused asynchronies similar to those observed in cases of repeat breeding. The repeated AI did not maintain fertility at normal levels. It is suggested that the extended growth of the ovulatory follicle may cause impaired oocyte maturation or it may alter the maternal milieu owing to the prolonged release of oestradiol.     

Effects of dietary menhaden oil on growth and reproduction in gilts farrowed by sows that consumed diets containing menhaden oil during gestation and lactation

In sows, n-3 fatty acids increase litter sizes, however, effects on gilt reproductive development have not been adequately studied. Moreover, not determined are effects of feeding n-3 fatty acids to sows on reproduction in offspring. The objective here was to determine effects of 4% dietary menhaden oil on growth and puberty in gilts farrowed by sows fed menhaden oil. Sows (n = 44) were assigned to: (1) control gestation and lactation diets, or (2) diets including menhaden oil. For primiparous sows only, total litter size and born alive were greater (P < 0.05) in females fed menhaden oil. Conversely, pigs from primiparous controls were heavier (P < 0.05) than pigs from primiparous sows fed menhaden oil (parity by diet interactions, P < 0.01). Diet did not affect (P > 0.20) other sow and litter characteristics. At weaning, 84 gilts from control- or menhaden oil sows were placed three gilts per pen and provided control diets or diets containing menhaden oil. Nursery and grow-finish feed intake and feed efficiency were similar (P > 0.21) for gilts from the different sows and weight gain was similar (P > 0.24) for gilts fed control or menhaden diets. Gilts fed menhaden oil tended to eat less in the nursery (1.18±0.08 kg v. 0.98±0.08 kg; P = 0.09) and overall (1.83±0.04 kg v. 1.72±0.04 kg; P = 0.06). Thus, overall feed to gain was greater (2.52±0.03 v. 2.33±0.03; P < 0.01) and nursery (2.12±0.04 v. 1.80±0.04; P = 0.10) and grow-finish (3.07±0.19 v. 2.58±0.19; P = 0.08) feed to gain tended to be greater, for control gilts. Age at puberty was greater (P = 0.02) for gilts from menhaden oil-fed sows (205.1±3.2 days) compared to gilts from controls (193.9±3.2 days) and tended to be greater (P = 0.09), for controls (203.5±3.2 days) compared to gilts fed menhaden oil (195.5±3.2 days). A tendency existed (P = 0.09) for greater follicular fluid in gilts fed menhaden oil, however, ovulation rate and ovarian, luteal and uterine weights were not affected by sow diet, gilt diet or the interaction (P > 0.23). Feeding gilts menhaden oil enhanced feed efficiency and hastened puberty onset. Gilts from sows consuming menhaden oil exhibited delayed puberty and retaining females from sows fed this feedstuff may be ill advised.     

Allelic variation in the erythropoietin receptor gene is associated with uterine capacity and litter size in swine

A single nucleotide polymorphism (SNP; C vs. T) that creates an extra GATA-1 site (T allele) in intron 4 of the swine erythropoietin receptor (EPOR) gene was discovered and a genotyping assay for this SNP was developed. A total of 402 gilts from lines selected either at random (control), for ovulation rate (OR) or for uterine capacity (UC) for 11 generations were unilaterally hysterectomized-ovariectomized (UHO) at 160 days of age, mated at approximately 250 days of age and slaughtered at 105 days of pregnancy. Blood samples and spleens were collected from each foetus and the numbers of corpora lutea (CL) and live foetuses, the weights of each foetus and placenta, and each foetal haematocrit were recorded. In addition, intact gilts from the OR line or from a Yorkshire, Landrace, Duroc, crossbred line (BX) were mated and farrowed. At farrowing, the numbers of fully formed and live piglets were recorded for each litter. Genomic DNA was isolated for both the UHO and intact gilts, from foetuses from the UHO gilts that were heterozygous for the EPOR SNP, and from the boars from the BX line and were then used to determine EPOR SNP genotypes. Only CC and CT gilts were observed in the control, OR and UC selected lines. Presence of the EPOR T allele was associated (P < 0.05) with increased UC in these gilts. The number of heterozygous and homozygous foetuses did not differ within UHO litters, or did EPOR genotype influence foetal haematocrit. In intact gilts from the OR line, litter size was significantly associated (P < 0.05) with EPOR SNP genotype. Finally, results from intact gilts of the BX line, in which both the gilt and the boar genotypes were known, allowed an analysis to determine the effect of the gilt and/or the foetal genotype on litter size. This analysis indicated that the predicted foetal genotype (with gilt genotype as covariate) was associated with litter size (an increase of 2.6 +/- 1.0 piglets born alive predicted for homozygous T litters compared with homozygous C litters, P < 0.01) whereas the effect of the gilt genotype (adjusted for foetal genotype) on litter size was not significant. These results indicate that the EPOR SNP is associated with UC and litter size in two distinct populations and could be useful in increasing litter size in swine that are not limited in OR.     

Effects of oestrous synchronization with altrenogest in gilts on endometrial and embryonic characteristics

The use of altrenogest (ALT) supplementation for oestrous synchronization improves subsequent reproductive performance of gilts and sows. However, the causes of this improvement in reproductive performance after ALT treatment are not fully/clearly understood. The objective of this study was to evaluate the effects of ALT supplementation for oestrous synchronization in gilts on the endometrial glands and embryonic development characteristics at 28 days of pregnancy. Pregnant gilts were divided into two experimental treatments: Control (did not receive ALT; n = 9 gilts) and ALT (ALT feeding at 20 mg/day for 18 days; n = 9 gilts). At 28 days of pregnancy, six gilts from each treatment were slaughtered, and reproductive tracts were immediately evaluated. There was no statistical difference (P > 0.05) between treatments regarding ovulation rate, number of embryos, number of vital embryos and number of non-vital embryos. Embryo weight, length and embryonic vesicle weight were lower in ALT treatment compared with Control (P < 0.01), and it was lower in the cervical uterine region compared with apex uterine region, respectively (P < 0.05). Higher values of gland duct area, gland duct perimeter, percentage of the glandular area and total endometrial area were observed in ALT treatment compared with Control (P < 0.05). The use of ALT during 18 days for oestrous synchronization in gilts increased the gland duct area, perimeter and total endometrial area but did not increase the embryo number and embryo size at day 28 of pregnancy.     

Increased ovulation rate in gilts after oral administration of epostane

In Phase I of this study to enhance ovulation rate and hence litter size, gilts received 0 (sham control), 0.625, 1.25, 2.5 or 5.0 mg epostane/kg body weight on Days 10, 11 and 12 of the oestrous cycle (5 gilts/group). After epostane treatment, plasma progesterone concentrations were reduced (P less than 0.01) in a dose-related manner, % progesterone decline = 21.30 x square root of (dose) + 10.45, R2 = 0.70, but recovered to pretreatment levels by 24 h. In Phase II the effects of epostane on ovulation rate and litter size were tested at two study centres. At each centre 108 gilts were treated with the same doses of epostane as used in Phase I and the doses were given for 7 days (Days 15-21) or 12 days (Days 10-21) during the first oestrous cycle. Gilts were inseminated twice during the oestrus after treatment and were slaughtered 30 days later. Mean (+/- s.d.) ovulation rate was 16 +/- 2.7 (N = 8) and 21 +/- 4.0 (N = 61) for control and epostane-treated gilts in Centre A and 12 +/- 2.4 (N = 5) and 17 +/- 3.8 (N = 55) respectively in Centre B (P less than 0.01 for both) and was dose related (ovulation rate = 3.38 x square root of (dose) + 16.17, R2 = 0.31). The effects of 7- or 12-day epostane treatment on ovulation rate were not different (P greater than 0.05), indicating that effects of treatment after Day 14 of the oestrous cycle are most important to subsequent ovulation frequency.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary l-arginine supplementation to gilts during early gestation on foetal survival, growth and myofiber formation

The effects of l-arginine on porcine foetal development and myogenesis were determined. Twenty Swiss Large White gilts were randomly allocated to either the control (C) or l-arginine treatment (A). In addition to the standard gestation diet, A-sows received 26 g l-arginine daily from days 14 to 28 of gestation. At day 75 of pregnancy, sows were sacrificed and the number and weight of foetuses were recorded. From each litter, the lightest, heaviest and the ones with an average foetal weight (FtW) were selected. Primary (P), secondary (S) and total myofiber number as well as S/P ratio were determined in the semitendinosus (ST) and rhomboideus (RH) muscles. In A-sows, the number of viable foetuses (13.0 v. 9.3) and total FtW (4925 v. 3729 g) was greater (P ⩽ 0.04) than in C-sows. Compared to C-sow foetuses, the ST of A-sow foetuses had 7% more (17 699 v. 16 477; P = 0.04) P myofibers and the S/P ratio in both muscles was lower (ST = 20.3 v. 21.5; RH = 24.1 v. 27.1; P ⩽ 0.07). Regardless of the maternal diet, the S myofiber number and the S/P ratio in both muscles were greater (P ⩽ 0.01) in foetuses with a high FtW compared to low FtW. These data suggest that l-arginine supplemented to gilts during early gestation enhanced foetal survival and in the ST positively affected the primary phase of myofiber formation.     

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.     

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.     

Critical periods for foetal mortality in gilts identified by analysing the length distribution of mummified foetuses and frequency of non-fresh stillborn piglets

The objective of this study was to investigate the timing of foetal mortality in gilts of a segregating F2 cross of Large White and Meishan pigs on the basis of the length distribution of mummified foetuses and the frequency of non-fresh stillborn piglets in order to establish whether critical periods for foetal mortality exist. All expelled conceptuses and placentae of 192 farrowing gilts with a normal health status were meticulously investigated to recover all mummified foetuses. The length of each mummified foetus was measured. The predicted number of foetuses present per gilt at the early foetal stage of gestation was calculated as the sum of numbers of mummified foetuses and non-fresh stillborn, fresh stillborn and liveborn piglets. Foetal loss was calculated as the sum of mummified foetuses and non-fresh stillborn piglets. The average foetal mortality rate per gilt was 8.7%. In total 162 mummified foetuses were found (average 0.84 per litter), ranging in length from 0.4 to 33.0 cm. This indicates a range in foetal age at death of approximately 35-100 days. Although mummified foetuses of all lengths within the above mentioned range were found, relatively many had a length of less than 4 cm or of 10-21 cm. The total number of non-fresh stillborn piglets (i.e. late foetal deaths) was 58 (average 0.30 per litter). It can be concluded that foetal mortality occurred in these gilts throughout the period from day 35 to term, with relatively high incidences at the early foetal stage (days 35-40), shortly after mid-pregnancy (days 55-75) and after approximately day 100 of gestation. These three periods coincide with reported periods of change in porcine placental growth.     

The reproductive response to the male effect of 7- or 10-month-old female goats is improved when photostimulated males are used

The exposure of adult, female, Mediterranean goats during anoestrus to males with induced sexual activity via photostimulation, induces a very high percentage of ovulations. The present work examines the ability of photostimulated bucks to improve the male effect-induced reproductive response of young does over that induced by non-stimulated bucks. A 2×2 factorial experiment was designed, consisting of doe age and buck photoperiod treatments. During seasonal anoestrus, 41 does aged 7 (n=19) or 10 (n=22) months were subjected to the male effect on 10 April; half of each group was exposed to males rendered sexually active by prior exposure to 3 months of long days (16 h of light/day) from 31 October (PHOTO bucks), and half to males maintained under the natural photoperiod (CONTROL bucks). Oestrous activity was recorded daily by direct visual observation of the marks left by male-worn marking harnesses over the 32 days following the bringing of the sexes together (introduction). Doe body weight and body condition were determined weekly. Ovulation was detected by measuring plasma progesterone concentrations twice per week over the 3 weeks after introduction. The ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The interaction doe age × buck photoperiod treatment had no effect on any outcome. The percentage of females showing ovulation or oestrus was higher in the does exposed to PHOTO bucks (85% v. 43% for those exposed to CONTROL bucks) they also showed higher fertility (75% v. 43%) and productivity (1.05±0.17 v. 0.57±0.16 kids born per doe serviced) (all P values at least P<0.05). The 10-month-old group showed higher percentage of females showing ovulation, oestrus, fertility and productivity than the 7-month-old does after the male effect (females showing ovulation: 82% v. 42%; showing oestrus: 73% v. 42%; fertility: 73% v. 42% and productivity: 1.09±0.17 v. 0.47±0.14 goat kids born per doe serviced; respectively, all P values at least P<0.05). The present results show that the use of photostimulated males improves the reproductive performance of 7- and 10-month-old does, and may contribute towards increasing their productivity and lifetime reproductive performance.     

The effects of PG600 and boar exposure on oestrus detection and potential litter size following mating at either the induced (pubertal) or second oestrus

Within gilt pools, incidences of delayed puberty attainment, failure to exhibit regular oestrous cycles and low first litter size are often high. Boar exposure is an effective method of accelerating puberty; however, the timing of gilt response can vary greatly. Although, PG600 (400 IU of PMSG and 200 IU of hCG; Intervet) can induce a rapid and synchronous ovulatory response, thus providing an alternative to boar contact, the quality of the response is often variable. This study compared the effect of PG600, either alone (NBC) or in conjunction with boar exposure (BC), on puberty attainment and maintenance of oestrous cyclicity. The effects of first mating these gilts at the hormonally induced (pubertal) or second oestrus on ovulation rate and early embryo survival were also studied. Eighty Large White cross terminal (Duroc) line gilts were used in this study. The study was conducted in two blocks, with 10 gilts allocated to each of the four treatments in each block. Gilts were artificially inseminated at the allocated oestrus, with the reproductive tracts collected at 26.5+/-0.29 days after first mating (mean+/-S.E.M.), and the number of corpora lutea and viable embryos recorded. Mean days-to-puberty was significantly reduced (P<0.05) when gilts received both PG600 and boar exposure as opposed to PG600 alone (5.7+/-0.15 versus 6.9+/-0.37 days; P<0.01). The proportion of gilts exhibiting an ovulatory response to PG600 was similar for the BC and NBC treatment groups (0.88 and 0.84); however, the proportion of gilts exhibiting visible signs of oestrus in response to PG600 was significantly higher for the BC compared to the NBC treatment groups (0.81 versus 0.49; P<0.05). Boar contact resulted in a numerical, but not significant, increase in the proportion of gilts exhibited a second oestrus (1.00 versus 0.76). There was no significant effect of boar contact on ovulation rate, embryo number or survival. Although ovulation rate was unaffected by oestrus at mating, embryo number was significantly increased (P<0.05) following mating at the second compared to the first oestrus (11.2+/-0.96 versus 7.8+/-1.17). In conclusion, the current data indicate that the timing of puberty attainment and oestrus detection are significantly improved when PG600 treated gilts receive full boar contact. Further, it is evident that mating gilts at their second as opposed to the hormonally induced oestrus significantly increases embryo number at day 26 post-mating.     

Calm Merino ewes have a higher ovulation rate and more multiple pregnancies than nervous ewes

In 1990, two selection lines of Merino sheep were established for low and high behavioural reactivity (calm and nervous temperament) at the University of Western Australia. Breeding records consistently showed that calm ewes weaned 10% to 19% more lambs than the nervous ewes. We hypothesise that calm ewes could have a higher ovulation rate than nervous ewes and/or calm ewes could have a lower rate of embryo mortality than nervous ewes. We tested these hypotheses by comparing the ovulation rate and the rate of embryo mortality between the calm and nervous lines before and after synchronisation and artificial insemination. Merino ewes from the temperament selection lines (calm, n=100; nervous, n=100) were synchronised (early breeding season) for artificial insemination (day 0) (intravaginal sponges containing fluogestone acetate and eCG immediately after sponge withdrawal). On day-17 and 11 ovarian cyclicity and corpora lutea, and on days 30 and 74 pregnancies and embryos/foetuses were determined by ultrasound. Progesterone, insulin and leptin concentrations were determined in blood plasma samples from days 5, 12 and 17. Ovarian cyclicity before and after oestrus synchronisation did not differ between the lines, but ovulation rate did (day-17: calm 1.63; nervous 1.26; P<0.01; day 11: calm 1.83; nervous 1.57; P<0.05). Ovulation rate on day 11 in nervous ewes was higher than on day-17. Loss of embryos by day 30 was high (calm: 71/150; nervous: 68/130); but nervous ewes had a lower proportion (15/47) of multiple pregnancies compared with calm ewes (30/46; P<0.01). Reproductive loss between days 30 and 74 represented 7.3% of the overall loss. Temperament did not affect concentrations of progesterone, but nervous ewes had higher insulin (32.0 pmol/l±1.17 SEM; P=0.013) and lower leptin (1.18 μg/l±0.04 SEM; P=0.002) concentrations than calm ewes (insulin: 27.8 pmol/l±1.17 SEM; leptin: 1.35 μg/l±0.04 SEM). The differences in reproductive outcomes between the calm and nervous ewes were mainly due to a higher ovulation rate in calm ewes. We suggest that reproduction in nervous ewes is compromised by factors leading up to ovulation and conception, or the uterine environment during early pregnancy, that reflect differences in energy utilisation.     

Oestrus cycle characteristics and prediction of ovulation in Catalonian jennies

The Catalonian donkey breed is in danger of extinction, and much needs to be learned about the reproductive features of its females if breeding and conservation programmes are to be successful. This study reports the oestrous behaviour, oestrus cycle characteristics and dynamic ovarian events witnessed during 50 oestrous cycles (involving 106 ovulations) in 10 Catalonian jennies between March 2002 and January 2005. These jennies were teased, palpated transrectally and examined by ultrasound using a 5 MHz linear transducer—daily during oestrus and every other day during dioestrus. Predictors of ovulation were sought among the variables recorded.The most evident signs of oestrus were mouth clapping (the frequent vertical opening and closing of the mouth with ears depressed against the extended neck) and occasional urinating and winking of the vulval lips (homotypical behaviour). Interactions between jennies in oestrus were also recorded, including mounting, herding/chasing, the Flehmen response, and vocalization (heterotypical behaviour).Nine jennies ovulated regularly throughout the year; one had two anovulatory periods (54 and 35 days). The length of the oestrus cycle was 24.90 ± 0.26 days, with oestrus itself lasting 5.64 ± 0.20 days (mean ± S.E.M.) and dioestrus 19.83 ± 0.36 days. The incidence of single, double and triple ovulations was 55.66% (n = 59), 42.45% (n = 45) and 1.89% (n = 2), respectively. No significant difference was seen in the number of ovulations involving the left and right ovaries (52.63% [n = 70] compared to 47.37% [n = 63] respectively; P > 0.05). The mean interval between double ovulation was 1.44 ± 3.98 days. The mean diameter of the preovulatory follicle at day −1 was 44.9 ± 0.5 mm; the mean growth rate over the 5 days before ovulation was 3.7 mm/day.Data on preovulatory changes in oestrous behaviour, follicle size, follicle texture, the echographic appearance of the follicle and uterus, and uterine tone were subjected to stepwise logistic regression analysis to detect predictors of ovulation. The logit function showed the best predictors to be follicle size, follicular texture and oestrous behaviour. Certain combinations of these three variables allow the prediction of ovulation within 24 h with a probability of >75%.     

The effects of chronic environmental stress on parturition and on oxytocin and vasopressin secretion in the pig

Previous work has suggested that an acute behavioural confinement in mid-partum can inhibit oxytocin secretion and prolong delivery in the pig, an effect that is opioid mediated. The present experiment investigated the effect of longer-term (chronic) behavioural confinement, that has previously been shown to elevate total plasma cortisol, on speed of delivery and on plasma oxytocin and lysine vasopressin concentrations during the peri-parturient period in primiparous pigs (gilts). Five days before their expected parturition (farrowing) date, gilts with preplaced jugular catheters were either confined to farrowing crates that severely restricted maternal behaviour, or housed in pens that permitted free movement and maternal behaviour (e.g. nest building). Blood samples were taken continuously from 24 h before the birth of the first piglet (BFP) to 6 h post-BFP, and for oxytocin on Days 1, 2, and 7 following parturition (Days P1, P2, P7). Both oxytocin and vasopressin were strongly influenced by parturition (P<0.001). There was no overall effect of chronic crating on either hormone, but crated and penned gilts did show significant differences with respect to the pattern of both oxytocin and vasopressin concentrations over time (P<0.05 in both cases). Oxytocin and vasopressin first increased in crated and penned gilts from 3 h pre-BFP (P<0.05). Crated gilts subsequently showed greater increases in both oxytocin and vasopressin over the first hour of delivery than penned gilts (mean oxytocin (pmol 1⁻¹): 53.3±8.5 vs. 39.7±5.0 for crated vs. penned gilts; mean vasopressin (pmol l⁻¹):4.4±0.7 vs. 2.0±04 for crated vs. penned gilts; both P<0.05). For oxytocin, crated gilts then showed subsequent declining concentrations relative to penned gilts (P<0.05). For vasopressin, penned gilts reached similar concentrations as crated gilts in the third hour post-BFP before vasopressin concentrations in both groups declined. Crated gilts also gave birth to piglets faster in the early stages of delivery (e.g. mean interval between Piglets 2 and 3 (min): 9.6±2.5 vs. 25.6±8.54 for crated and penned gilts, respectively: P<0.02). We conclude that confinement of gilts to a farrowing crate for 5 days neither adversely affects the progress of delivery in the primiparous pig nor the secretion of posterior pituitary hormones involved in parturition.     

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.     

Urea production and arginine metabolism are reduced in the growth restricted ovine foetus

Urea production may be impaired in intrauterine growth restriction (IUGR), increasing the risk of toxic hyperammonaemia after birth. Arginine supplementation stimulates urea production, but its effects in IUGR are unknown. We aimed to determine the effects of IUGR and arginine supplementation on urea production and arginine metabolism in the ovine foetus. Pregnant ewes and their foetuses were catheterised at 110 days of gestation and randomly assigned to control or IUGR groups. IUGR was induced by placental embolisation. At days 120 and 126 of gestation, foetal urea production was determined from [¹⁴C]-urea kinetics and arginine metabolism was determined from the appearance of radioactive metabolites from [³H]-arginine, both at baseline and in response to arginine or an isonitrogenous mixed amino acid supplementation. Urea production decreased with gestational age in the embolised animals (13.9 ±  3.1 to 11.2 ±  3.0 μmol/kg per min, P ≤ 0.05) but not in the controls (13.3 ±  3.5 to 14.8 ±  6.0 μmol/kg per min). Arginine supplementation increased urea production in both groups, but only at 126 days of gestation (control: 15.0 ±  8.5 to 17.0 ±  9.4 μmol/kg per min; embolised: 11.7 ±  3.1 to 14.3 ±  3.1 μmol/kg per min, P ≤ 0.05). Embolisation reduced foetal arginine concentrations by 20% ( P ≤ 0.05) while foetal arginine consumption was reduced by 27% ( P ≤ 0.05). The proportions of plasma citrulline and hydroxyproline derived from arginine were reduced in the embolised animals. These data suggest that foetal urea production and arginine metabolism are perturbed in late gestation after placental embolisation.     

Effect of intrauterine infusion of recombinant bovine interferon αI1 on luteal phase duration and oxytocin-induced release of 13,14-dihydro-15-keto-prostaglandin F2α in postpartum beef cows

The objective of this study was to determine if oxytocin-induced release of prostaglandin F₂α (PGF_2α; measured by the stable metabolite, 13,14-dihydro-15-keto-prostaglandin F₂α (PGFM)) was inhibited following intrauterine infusion of bovine interferon-α_I1 (rboIFNα_I1) into postpartum cows anticipated to have short estrous cycles following first ovulation postpartum. Cows expected to have short estrous cycles were assigned to receive twice daily intrauterine infusions of either placebo (SCP; n = 11) or 2 mg rboIFNα_I1 (SCIFN; n = 14) on Days 1–16 following hCG injection (2500 IU; day 0) on Days 30 or 31 postpartum. On Day 5 following hCG, each cow was injected with 100 IU oxytocin (i.v.) to induce the release of uterine PGF_2α (as measured by PGFM). Other treatment groups consisted of cows expected to have normal estrous cycle lengths following pretreatment with a 9 day norgestomet implant on Days 21 or 22 postpartum followed by hCG injection to induce ovulation. Cows expected to have normal estrous cycle lengths received twice daily intrauterine infusions of either placebo from Days 1 to 16 of the cycle and 100 IU oxytocin (i.v.) on Day 5 (NCPE; n = 11) or twice daily infusions of placebo (NCPL; n = 7) or rboIFNα_I1 (NCIFN; n = 10), from Day 13 post-hCG injection until luteolysis. Oxytocin was injected (100 IU; i.v.) into cows in the NCPL and NCIFN groups on Day 16. The calculated areas under the curve (arbitrary PGFM units) were: 164 ± 18 units, 96 ± 16 units, 93 ± 18 units, 137 ± 27 units and 53 ± 20 units for SCP, SCIFN, NCPE, NCPL and NCIFN, respectively (SCIFN < SCP; NCIFN < NCPL; P < 0.015). Mean luteal phase length was calculated as the number of days from injection of hCG until progesterone declined to below 0.5 ng ml⁻¹ and was: 6.7 ± 1.0 days, 10.5 ± 0.9 days, 12.0 ± 1.0 days, 18.0 ± 1.3 days and 20.7 ± 1.1 days for SCP, SCIFN, NCPE, NCPL and NCIFN, respectively (SCP < SCIFN = NCPE < NCPL = NCIFN; P < 0.01). In summary, luteal phase lengths were increased and oxytocin-induced release of PGFM was reduced by rboIFNα_I1 infusion in cows anticipated to have short luteal phases.     

Induction of fertile oestrus in seasonally anoestrous ewes with low doses of Gn-RH

Oestrus, conception and lambing performance were assessed in progesterone-primed seasonally anoestrous ewes induced to ovulate with gonadotrophin-releasing hormone (Gn-RH), which was administered intravenously for 48 h as either injections of 250 ng at 2-h intervals (n = 15) or as a continuous infusion at the rate of 125 ng/h (n = 12) or 250 ng/h (n = 12).In $\text{14}\text{15}$ of the ewes injected with Gn-RH, a preovulatory LH peak was recorded at a mean time interval of 33.9 ± 1.8 h after the start of treatment. All ewes displayed oestrus and all ovulated, with a mean ovulation rate of 1.67 ± 0.13. Eleven ewes were diagnosed as pregnant and subsequently lambed. Following infusion of Gn-RH, preovulatory LH peaks were recorded in $\text{21}\text{24}$ ewes at a mean time of 36.1 ± 2.9 h (125 ng/h) and 34.7 ± 2.0 h (250 ng/h). All but two of the ewes displayed oestrus and $\text{23}\text{24}$ ovulated. The group mean ovulation rates of 1.27 ± 0.14 (125 ng/h) and 1.75 ± 0.22 (250 ng/h) were not significantly different. Eleven of the 22 ewes mated were diagnosed as pregnant and produced live lambs.These results suggest that fertility of Gn-RH-induced ovulations in seasonally anoestrous ewes is comparable to that apparent in ewes ovulating spontaneously during the breeding season.