N.M. Soede

Myometrial activity around estrus in sows: spontaneous activity and effects of estrogens, cloprostenol, seminal plasma and clenbuterol

A new, nonsurgical, open-end catheter technique was used to study spontaneous uterine activity around estrus in sows, and the effects of estrogens, seminal plasma, cloprostenol, and clenbuterol on uterine activity. In the first experiment, uterine activity was studied in 14 multiparous, cyclic sows, during one or more estrous cycles, from day -4 to day 4 of the cycle (day 0: first day of standing estrus). From a few days before estrus until estrus, the percentage of sows showing any uterine contractions increased from 55 to 100%, and frequency and mean amplitude of uterine contractions for these sows increased from 15 to 22/h, and from 20 to 40 mmHg on average. After estrus, uterine activity decreased. There were large differences between sows in uterine activity, which were consistent over the days of the cycle. In the second experiment, 11.5 microg of estrogens in 100 ml saline (n = 17), 100 ml seminal plasma (n = 5), 1 mg cloprostenol in 100 ml saline (n = 10), 0.30 mg clenbuterol in 100 ml saline (n = 11), or 100 ml saline (n = 5) was infused IU, after recording spontaneous activity. Infusion with saline or seminal plasma did not affect uterine activity. Estrogens increased frequency of contractions. Cloprostenol increased both frequency and amplitude of contractions. Clenbuterol reduced both frequency and amplitude of contractions. In conclusion, this study shows that spontaneous uterine activity in sows is increased around estrus, and it supports the role of estrogens in boar seminal plasma in affecting uterine activity around mating. Further, this study has yielded possible tools to study the relation between uterine activity and sperm transport.

Effects of different sexual stimuli on oxytocin release, uterine activity and receptive behavior in estrous sows

This study was designed to assess effects of exogenous oxytocin (OT) on uterine activity, and to compare three different sexual stimuli in their effects on OT release, uterine activity and receptive behavior in estrous sows. Uterine activity was recorded nonsurgically, by transcervical insertion of an open-end catheter into the caudal part of the uterine lumen. After recording spontaneous uterine activity, exogenous OT was administered (Experiment 1), or one of the following stimuli was applied to the sow (Experiment 2): tactile stimuli, i.e. manual stimulation of the sows back and flanks, tactile stimulation in combination with boar pheromone spray (5alpha-androstenon), or tactile stimuli in the presence of a boar. Both exogenous OT and endogenously released OT increased uterine activity. The effect depended on the uterine activity before treatment, with the effect being greater in those sows with lower uterine activity before treatment. In Experiment 2, boar presence was the only stimulus that elicited a clear, surge-like release of OT, and also clearly increased uterine activity. Release of OT was not necessary for induction of receptive behavior: tactile stimulation alone and in combination with pheromone spray elicited a standing response in one third of the sows, but had no effect on OT release.

Oestrus, ovulation and peri-ovulatory hormone profiles in tethered and loose-housed sows

Multiparous sows that had been tethered during lactation were put in two different housing conditions after weaning (Day 0); the sows were either tethered by neck chain, or individually housed in a pen of approximately 6 m2. After two months, ten tethered and eleven loose housed sows were used to assess stress and reproductive parameters. Stereotypic behaviour after the afternoon feeding was assessed from Day 18 onwards; at Day 53 stereotypic behaviour tended to occur during a higher percentage of time in the tethered sows (P = 0.11) and at Day 66, the differences were significant (tethered, 78 +/- 5 vs. loose-housed, 40 +/- 10% of time (mean +/- sem); P = 0.03). At Day 35 and 55, cortisol profiles after afternoon feeding were similar for the two groups of sows (P > 0.10). Around oestrus (approximately Day 64), the profiles of oestradiol-17 beta, luteinizing hormone and progesterone were measured and proved to be similar for both treatment groups (P > 0.10). The duration of oestrus was shorter in the tethered sows (42 +/- 4 vs. 63 +/- 2 h; P < 0.001) and, consequently, the timing of ovulation during oestrus (h after onset of oestrus) was advanced in the tethered sows (28 +/- 2 vs. 41 +/- 2; P < 0.001). The duration of ovulation did not differ (tethered, 2.9 +/- 0.5 vs. loose-housed, 2.1 +/- 0.2 h; P = 0.16). The sows were sacrificed at Day 5 after ovulation; ovulation rate, fertilization rate, embryo development and embryo diversity were similar for the two groups, as were adrenal weight and size of adrenal cortex. Duration of oestrus and the levels of stereotypies at Day 60 tended to be negatively related in the tethered sows (P = 0.07), but not in the loose-housed sows (P = 0.65). In conclusion, sows that had been tethered during pregnancy and lactation, and were housed loose or were tethered again at weaning within two months differed both in stereotypic behaviour and in duration of oestrus, without apparent effects on reproductive hormones.

Peri‐oestrus Hormone Profiles and Follicle Growth in Lactating Sows with Oestrus Induced by Intermittent Suckling

This study describes follicle dynamics, endocrine profiles in multiparous sows with lactational oestrus compared with conventionally weaned sows (C). Lactational oestrus was induced by Intermittent Suckling (IS) with separation of sows and piglets for either 12 consecutive hours per day (IS12, n = 14) or twice per day for 6 h per occasion (IS6, n = 13) from day 14 of lactation onwards. Control sows (n = 23) were weaned at day 21 of lactation. Pre-ovulatory follicles (> or =6 mm) were observed in 100% of IS12, 92% of IS6 and 26% of C sows before day 21 of lactation and in the remaining 74% C sows within 7 days after weaning. All sows with pre-ovulatory follicles showed oestrus, but not all sows showed ovulation. Four IS6 sows and one IS12 sow developed cystic follicles of which two IS6 sows partially ovulated. Follicle growth, ovulation rate and time of ovulation were similar. E(2) levels tended to be higher in IS sows (p = 0.06), the pre-ovulatory LH surge tended to be lower in IS12 (5.1 +/- 1.7 ng/ml) than in C sows (8.4 +/- 5.0 ng/ml; p = 0.08) and P(4) levels were lower in IS12 and IS6 than in C sows (at 75 h after ovulation: 8.8 +/- 2.4 ng/ml vs 7.0 +/- 1.4 ng/ml vs 17.1 +/- 4.4 ng/ml; p < 0.01). In conclusion, sows with lactational oestrus induced by IS are similar to weaned sows in the timing of oestrus, early follicle development and ovulation rates, but the pre-ovulatory LH surge and post-ovulatory P(4) increase are lower.

Improving adaptation to weaning: Effect of intermittent suckling regimens on piglet feed intake, growth, and gut characteristics

Daily separation of sows and piglets during lactation, intermittent suckling (IS), improves feed intake and postweaning adaptation in piglets. The aim of the current study was to determine how, in piglets that have been subjected to IS, age at weaning and the duration of the preceding IS period contribute to postweaning adaptation through effects on feed intake, growth, and gut characteristics. All piglets had ad libitum access to creep feed from d 7. Litters were subjected to conventional weaning (CW) or to 1 of 3 IS regimens. In CW, litters (n = 29) had continuous access to the sow until weaning (d 26, d 0 = farrowing). During IS, litters had access to the sow between 1600 and 0600 h. Litters in the IS treatments were subjected to IS 1) from d 19 onward and weaned at d 26 (IS19-7D, n = 33), 2) from d 19 onward and weaned at d 33 (IS19-14D, n = 28), or 3) from d 26 onward and weaned at d 33 (IS26-7D, n = 33). The IS19-7D regimen resulted in a relative growth check within the first 2 d after weaning similar to CW litters (72 +/- 13 and 90 +/- 7%, respectively), but in a greater piglet growth (P = 0.014) and feed intake (P = 0.001) between d 2 and 7 postweaning. Moreover, IS19-7D was not associated with a (further) reduction in villus height as observed at d 2 postweaning in CW litters. In IS piglets weaned after an extended lactation (d 33), a markedly smaller weaning-associated relative growth check was observed shortly postweaning (11 +/- 18 and 32 +/- 19% for IS19-14D and IS26-7D litters, respectively). In these litters, feed intake and growth within the first 2 d after weaning were slightly greater when piglets were subjected to IS for 2 wk (IS19-14D) rather than for 1 wk (IS26-7D; P = 0.032 and P = 0.037 for feed intake and growth, respectively). Irrespective of duration of IS, weaning at d 33 with IS was not associated with a reduction in villus height. Irrespective of treatment, plasma citrulline concentrations were reduced at d 2 and 8 postweaning compared with the values at weaning (P < or = 0.01). No correlation was observed between postweaning plasma citrulline concentrations and postweaning small intestinal villus height. This study indicates that 1 wk of IS before weaning at d 26 of lactation improves feed intake and growth between d 2 and 7 postweaning and does not result in a reduction of villus height as observed in CW piglets, although it did not prevent a profound growth check shortly after weaning. However, combining 1 wk of IS with an extended lactation improved postweaning adaptation markedly in terms of growth, feed intake, and gut characteristics. Increasing the duration of IS from 1 to 2 wk slightly improved growth and feed intake shortly after weaning, but the contribution to postweaning adaptation seemed to be relatively small compared with extending lactation.

Effect of excessive, hormonally induced intrauterine crowding in the gilt on fetal development on day 40 of pregnancy

Selection for litter size may result in an increase in uterine crowding due to a faster increase in ovulation rate than in litter size. Increased ovulation rate does not result in a proportionally increased number of piglets born alive. In this study, the effect of ovulation rate on vitality characteristics of fetal-placental units at d 40 of pregnancy was investigated. For this, 43 Large White gilts were treated with hormones to induce superovulation. Average ovulation rate was 45.16 +/- 13.22; average number of vital fetuses at d 40 of pregnancy was 17.09 +/- 3.61 that weighed 11.26 +/- 1.99 g; their placenta weighed 31.88 +/- 14.79 g; and they occupied 11.69 +/- 4.90 cm of the uterus. Loss in oocytes (i.e., that did not result in a vital fetus at d 40) increased with increasing ovulation rate and occurred before (early mortality; P = 0.0003) and after implantation (late mortality, i.e., traces visible at d 40; P < 0.0001). With respect to the vital fetuses, increased ovulation rate resulted in decreased fetal (P = 0.0008) and placental weight (P = 0.0008) and decreased length of the area in the uterus that was occupied by the placenta (P = 0.0011). Strong correlations existed between placental and fetal weight [0.68; 95% confidence interval (CI) = 0.64 to 0.72], and placental weight and length (0.78; 95% CI = 0.74 to 0.82). Fetal-placental characteristics were weakly correlated to distance to the implantation sites of neighboring fetuses, a measure of crowdedness [-0.002 (95% CI = -0.042 to 0.038) with fetal weight to 0.16 (95% CI = 0.12 to 0.20) with placental length]. Increased ovulation rates, but more specifically increased late mortality rates, have negative effects on the remaining vital fetuses with respect to the fetal (P = 0.0085) and placental weight (P < 0.0001) and length of the implantation site (P = 0.0016). The most extreme effect was on placental weight, in which a uterus with <10 cases of late mortality was on average 25% greater than placental weight in a uterus with >18 cases of late mortality (P < 0.0001). Furthermore, increased ovulation rates resulted in decreased within litter variation for fetal (P = 0.0018) and placental weight (P = 0.0084). At increased ovulation rates, the number of live fetuses remained similar, but placental development is impaired and the growth of the fetus is retarded compared with reduced ovulation rate, with effects likely lasting into adult life.

Timing of insemination relative to ovulation in pigs: effects on sex ratio of offspring.

The objective of the present study was to identify effects of the interval between insemination and ovulation in pigs on the sex ratio and sex ratio dispersion of offspring. Crossbred sows that had farrowed 2 to 9 litters were weaned (Day 0) and came into estrus between Days 3 and 7 after weaning. Ultrasonography was performed every 6 h, from 12 h after the onset of estrus until ovulation had been observed. The sows were inseminated once at various intervals from the onset of estrus. At farrowing, the numbers of viable piglets and dead piglets were recorded per sow. In four 12-h intervals between insemination and ovulation (36 to 24 h before ovulation, 24 to 12 h before ovulation, 12 to 0 h before ovulation and 0 to 12 h after ovulation), the total number of piglets was (mean+/-SEM) 10.8+/-1.2 (n=15); 13.4+/-0.7 (n=23); 13.2+/-0.9 (n=21); and 12.1+/-1.0 (n=16), respectively (P>0.05). The percentage of male piglets per litter in the four 12-h intervals was 52.1+/-3.6, 50.5+/-2.7, 54.9+/-2.8 and 47.8+/-4.5, respectively (P>0.05). Sex ratio was not influenced by litter size (P>0.05), and its distribution was normally dispersed (i.e., as expected under a binomial distribution) in all 4 intervals between insemination and ovulation (P>0.05).

Vaginal temperature is not related to the time of ovulation in sows

The relationship between vaginal temperature and ovulation time was studied in sows. The vaginal temperature was measured continuously between Day 4 and Day 10 after Altrenogest-treatment in 10 sows. Oestrus was checked with a vasectomized boar at 8-h intervals, and during oestrus, ovulation time was checked with transrectal ultrasonography at 2-h intervals between 07:00 h and 23:00 h. Two sows ovulated between 23:00 h and 07:00 h, and these sows were taken out of the experiment. In the eight remaining sows, a clear day/night rhythm in vaginal temperature was found: between 03:00 h and 09:00 h, vaginal temperature (LSM +/- sem, corrected for sow) was on average 38.2 +/- 0.01 degrees C; between 15:00 h and 21:00 h, vaginal temperature was on average 38.5 +/- 0.01 degrees C (P < 0.001). Between 4 days before ovulation and 2 days after ovulation, no changes in temperature could be found that were related to ovulation time in any of the sows. Therefore, in sows, changes in vaginal temperature cannot be used as a predictor for ovulation time, and consequently cannot be used to predict the best time for insemination.

Early embryo survival and development in sows with lactational ovulation.

During lactation, daily separation of sow and piglets, intermittent suckling (IS), can induce lactational oestrus and ovulation. This study examined effects of IS on subsequent early embryo survival and development. Multiparous Topigs40 sows were separated from their piglets for either 12 consecutive hours per day (IS12, n = 13) or two times for 6 h per day (IS6, n = 10) from day 14 of lactation onwards until 23 days after ovulation. Control sows (C, n = 17) were weaned at day 21 of lactation. Oestrus was shown in all treatments within 5 days after the start of treatment. Sows were inseminated each day of oestrus and slaughtered at D23 after ovulation. Intermittent suckling did not significantly affect pregnancy rates of sows (75% IS12 vs 78% IS6 vs 94% C; p > 0.10). Embryo survival was not significantly affected by IS (IS12: 57%; IS6: 51%; p > 0.10) although it seemed to be lower than in C sows (70%). Some parameters of embryo, placental and uterine development were affected by IS, especially in the IS6 group. IS6 embryos had shorter placentas (17.5 +/- 1.2 cm; p < 0.05) than C (20.3 +/- 1.4 cm) and IS12 sows (20.9 +/- 0.7 cm) were smaller and less developed than C sows (p < 0.05). In conclusion, embryo survival does not seem significantly affected by IS, although numerical differences were great. Embryo development, however, was negatively affected in IS6 sows possibly due to a combination of high milk production, stress and lactational effects on uterine development.

An increased feed intake during early pregnancy improves sow body weight recovery and increases litter size in young sows

This study evaluated the effect of feeding level and protein content in feed in first- and second-parity sows during the first month of gestation on sow BW recovery, farrowing rate, and litter size during the first month of gestation. From d 3 to 32 after the first insemination, sows were fed either 2.5 kg/d of a standard gestation diet (control, n = 49), 3.25 kg/d (+30%) of a standard gestation diet (plus feed, n = 47), or 2.5 kg/d of a gestation diet with 30% greater ileal digestible AA (plus protein, n = 49). Feed intake during the experimental period was 29% greater for sows in the plus feed group compared with those in the control and plus protein groups (93 vs. 72 kg, P < 0.05). Sows in the plus feed group gained 10 kg more BW during the experimental period compared with those in the control and plus protein groups (24.2 ± 1.2 vs. 15.5 ± 1.2 and 16.9 ± 1.2 kg, respectively, P < 0.001). Backfat gain and loin muscle depth gain were not affected by treatment (P = 0.56 and P = 0.37, respectively). Farrowing rate was smaller, although not significantly, for sows in the plus feed group compared with those in the control and plus protein groups (76.6% vs. 89.8 and 89.8%, respectively, P = 0.16). Litter size, however, was larger for sows in the plus feed group (15.2 ± 0.5 total born) compared with those in the control and plus protein groups (13.2 ± 0.4 and 13.6 ± 0.4 total born, respectively, P = 0.006). Piglet birth weight was not different among treatments (P = 0.65). For both first- and second-parity sows, the plus feed treatment showed similar effects on BW gain, farrowing rate, and litter size. In conclusion, an increased feed intake (+30%) during the first month of gestation improved sow BW recovery and increased litter size, but did not significantly affect farrowing rate in the subsequent parity. Feeding a 30% greater level of ileal digestible AA during the same period did not improve sow recovery or reproductive performance in the subsequent parity.