Effect of sow parity on vaginal electrical impedance

The influence of sow parity on the changes of vaginal impedance after weaning was examined. Sows were monitored twice a day for oestrus via exposure to a sexually mature boar. The criterion for confirmation of ovulation was an increase in plasma progesterone levels above 12.5 nmol l(-1) 8 and 12 days after oestrus onset. The impedance measurements were carried out by a four-terminal method. In sows of all parities, the vaginal impedance decreased gradually after weaning (P < 0.01) and increased during oestrus (P < 0.01). No significant impedance changes were observed thereafter. The vaginal impedance was higher in sows above 6 parities than in sows from parities 1 to 5 from the beginning of oestrus to 14 days after oestrus onset. The impedance was also higher in sows of parity 6 than in sows of parity 1 from the beginning of oestrus to 14 days after oestrus onset and in sows from parities 2 to 5 than in sows of parity 1 from 2 to 4 days after oestrus onset. The difference in average impedance values between sows above 6 parities and sows of parity 1 was two-fold in oestrus compared to the luteal phase. In all measured places of the vagina from the cervix to 6 cm from the cervix, a similar significant increase of impedance was observed during oestrus. The results indicate that the parity of sows affects the electrical impedance of vaginal mucosa measured by means of a four-terminal method.     

Relationship between opposite changes of vaginal and vestibular impedance during estrous cycle in sows

Several bioimpedance techniques have been developed for noninvasive monitoring of reproductive events occurring in cyclic gilts and sows. Our objective was to compare the changes of vaginal and vestibular impedance during the porcine estrous cycle (experiment 1). In addition, we examined the causes of impedance variations in the vaginal vestibule during periestrus (experiment 2). The vaginal and vestibular impedance were measured with specially designed instruments. Sows were monitored for estrus via exposure to a sexually mature boar. The impedance in the vagina decreased gradually after weaning (P<0.01) reaching its nadir 2 days before estrus and increased during estrus to near maximum 2 days after estrus onset (P<0.01). The vaginal impedance during diestrus reached approximately the same level as on the weaning day. In contrast, the impedance in the vaginal vestibule increased gradually after weaning, then markedly during estrus (P<0.01) reaching its maximum 2 days after the onset of estrus followed by an abrupt decrease during early diestrus (P<0.01). The vestibular impedance after early diestrus reached almost the same level as before estrus. A significant negative correlation was found between the vaginal impedance in proestrus and vestibular impedance in periestrus. In experiment 2, interaction of the interval from weaning to estrus and parity significantly influenced the vestibular impedance in periestrus. The breed of sows did not affect the impedance in the vaginal vestibule through the whole experiment. From the present study we conclude that closely related inverse changes of the vaginal and vestibular impedance take place in pigs during the estrous cycle.     

Relationship of vaginal impedance with speed of return to oestrus after weaning, oestrous behaviour, parity and lactation length in cyclic sows

The effect of weaning to oestrus interval, oestrus duration, parity, lactation length, breed and their interactions on changes of vaginal impedance in sows after weaning and during oestrus was examined. The impedance measurements were carried out by a four-electrode method. The interval from weaning to oestrus was significantly longer in sows with the length of lactation 21-25 days than 26-30 days and 31-36 days and in primiparous than multiparous sows. The interval from weaning to oestrus was negatively correlated with the length of lactation (r=-0.21; P<0.05), parity (r=-0.36; P<0.01) and oestrus duration (r=-0.26; P<0.01). The weaning to oestrus interval, oestrus duration, parity and lactation length had a significant effect and the breed of sows had no influence on the vaginal impedance in peri-oestrus. The decrease of vaginal impedance after weaning was delayed in sows with a longer weaning to oestrus interval and in primiparous than multiparous sows. The decline of vaginal impedance during peri-oestrus was more gradual in sows with a longer interval from weaning to oestrus, shorter lactation, primiparous sows and sows with the length of oestrus 36 h and 72 h and more. The nadir of vaginal impedance occurred earlier before oestrus in sows with a shorter oestrus. The interaction of weaning to oestrus interval with parity and oestrus duration and the interaction of oestrus duration with parity significantly affected the vaginal impedance in weaned sows. In conclusion, the weaning to oestrus interval, oestrus duration, parity and lactation length considerably influence the vaginal impedance in sows during peri-oestrus. The findings indicate that the impedance technique may be a useful method for a study of factors and processes that accelerate or slow down the return to oestrus after weaning and affect oestrus duration in sows.     

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°C; between 15:00 h and 21:00 h, vaginal temperature was on average 38.5 ± 0.01°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.     

Effect of probe location on changes in vaginal electrical impedance during the porcine estrous cycle

The impedance technique is one of many methods that can be used for noninvasive monitoring of reproductive events occurring in cyclic animals. The influence of the depth of probe insertion on changes in vaginal impedance in sows during the estrous cycle was examined. Sows were checked twice a day for estrus via exposure to a sexually mature boar. The criterion for confirmation of ovulation was an increase in plasma progesterone levels above 4.0 ng/ml 8 and 12 days after the beginning of estrus. The impedance measurements were carried out using a four-terminal method at a distance of 8, 10, 12, 14, 16 and 18 cm from the vulva. In all six locations of the vagina the mean impedance values decreased gradually after weaning (P<0.01), achieved a nadir 1-2 days before estrus and increased during estrus (P<0.01). It was found that the probe location within the vagina and the parity of sows significantly affected the impedance measured by means of a four-terminal method. The study suggests that the causes of impedance fluctuation are not only technical but also include a number of poorly understood biological causes.     

Reproductive performance of purebred landrace and Yorkshire sows in Thailand with special reference to seasonal influence and parity number

The purpose of this study was to analyze reproductive performance in purebred Landrace and Yorkshire sows with special reference to seasonal influence and parity number, under tropical conditions where day length is almost constant throughout the year. Data from three purebred sow herds in Thailand during the period from 1993 to 1996 were analyzed. The two breeds were present in all three herds. The analysis comprised records of 3848 Landrace sow litters and 2033 Yorkshire sow litters. The statistical models included the fixed effects of month, year, parity, breed of the sow, herd, and two-way interactions of breed-parity, breed-herd, breed-month, breed-year, parity-month, month-herd, year-herd and month-year. The random effect of sow within breed was included in all models. Analysis of covariance was performed to analyze the effect of temperature, humidity and heat index on number of total born per litter (NTB), weaning to first service interval (WSI) and farrowing rate (FR). Landrace sows had significantly higher NTB (0.6 piglets), number of live born per litter (0.5 piglets), and average birth weight (0.13 kg) than Yorkshire sows (P<0.001). Farrowing rate was 3.9% higher in Landrace sows than in Yorkshire sows (P<0.01). However, Yorkshire sows had significantly shorter WSI (P<0.001) and significantly higher proportion of sows served within 7 days after weaning (P<0.01) than Landrace sows. No breed differences were found in number of stillborn per litter and weaning to conception interval. Parity had significant effect on all reproductive parameters analyzed. Number of total born and live born per litter was significantly lower for sows farrowing during the rainy season than in other seasons. Farrowing rate was low for sows mated during the hot and rainy season. Weaning to service interval and WSI7 were prolonged for sows weaned during the hot and rainy season. Reproductive performance was significantly unfavorably influenced by elevated temperature and heat index after mating (NTB and FR) or during lactation (WSI).     

Effect of birth litter size, birth parity number, growth rate, backfat thickness and age at first mating of gilts on their reproductive performance as sows

The present study was performed to evaluate retrospectively the influence of birth litter size, birth parity number, performance test parameters (growth rate from birth to 100kg body weight and backfat thickness at 100kg body weight) and age at first mating (AFM) of gilts on their reproductive performance as sows. Traits analysed included remating rate in gilts (RRG), litter size, weaning-to-first-service interval (WSI), remating rate in sows and farrowing rate (FR). Data were collected from 11 Swedish Landrace (L) and 8 Swedish Yorkshire (Y) nucleus herds and included 20712 farrowing records from sow parities 1-5. Sows that farrowed for the first time during 1993-1997, having complete records of performance test and AFM, were followed up to investigate their subsequent reproductive performance until their last farrowing in 1999. Analysis of variance and multiple regression were applied to continuous data. Logistic regression was applied to categorical data. The analyses were based on the same animals and the records were split into six groups of females, i.e. gilts, primiparous sows, and sows in parities 2-5, respectively. Each additional piglet in the litter in which the gilt was born was associated with an increase of her own litter size of between 0.07 and 0.1 piglets per litter (P<0.001). Gilts born from sow parity 1 had a longer WSI as primiparous sows compared with gilts born from sow parity 4 (0.3 days; P<0.05) or parity 5 (0.4 days; P<0.01). Gilts with a higher growth rate of up to 100kg body weight had a larger litter size (all parities 1-5; P<0.05), shorter WSI (all parities 1-5; P<0.05) and higher FR (parities 2 and 5; P<0.05) than gilts with a lower growth rate. Gilts with a high backfat thickness at 100kg body weight had a shorter WSI as primiparous sows (P<0.001) compared with low backfat gilts, and 0.1 piglets per litter more as second parity sows (P<0.01). A 10 day increase in AFM resulted in an increase in litter size of about 0.1 piglet for primiparous sows (P<0.001) and a decrease (P<0.05) for sow parities 4 and 5.     

Sexual motivation in relation to social rank in pair-housed sows

The influence of social subordination on sexual motivation during oestrus was studied using 36 sows of which 24 treatment sows were housed in pairs and 12 control sows were housed individually in 12 and 6 m(2) pens, respectively. Video recordings were made from 07:00 h to 19:00 h during the first 2 days after grouping, which took place 3 days after weaning of the piglets. Based on the aggressive interactions between the pair-housed sows, their rank was determined. From day 4 after weaning, a test for sexual proceptive behaviour was carried out twice daily and back-pressure test was carried out four times daily in order to detect standing oestrus. When standing oestrus had occurred, transrectal ultrasonographical scans were also carried out in order to determine if ovulation took place. The proceptivity test took place in a T-maze with a 2 m x 10 m runway ending in two 1.5 m x 1.5 m goal boxes each adjacent to a stimulus compartment. One compartment contained an adult sexually experienced boar and the other was empty. Latency to and duration of time spent close to the boar and time spent presenting were recorded during the 10-min test period. On the first day that standing oestrus had been detected, a test for sexual receptivity was also carried out by introducing the sow to a mature boar in his home pen (9 m(2)). Sexual- and fear-related behaviour of sow and boar were recorded until mating was terminated or the sow had spent 5 min in the pen without mating being initiated. During oestrus the proceptivity test showed a significant increase (P < 0.05) in the time spent standing close to the boar and in presenting for single-housed sows and for pair-housed dominant sows, but not for subordinate sows. During oestrus subordinate sows spent significantly less time standing close to the boar than the dominant sows (P = 0.01) and the same tended to be the case for presenting (P = 0.07). In the receptivity test more subordinate sows than dominant sows fled (40% versus 0%, P = 0.001) and more subordinate sows than dominant sows squealed (58% versus 15%, P = 0.02) as a response to boar stimulation. In both tests, the single-housed sows differed neither from the dominant nor the subordinate sows. There was however no difference between the groups in the weaning to oestrous interval, duration of oestrus and number of piglet born. In addition, all the sows ovulated. The results indicate that social subordination can have significant consequences for sexual motivation in sows. Subordinate sows showed fear-related behaviour in response to boar stimulation even when they were in standing oestrus. Thus, both heat detection and mating may be impaired in subordinate sows. The results emphasise the importance to alleviate the social stress experienced by subordinates as well as the need for stock people to pay special attention to these animals when they are to be mated or inseminated.     

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.     

An association analysis of sow parity,live-weight and back-fat depth as indicators of sow productivity

Understanding how critical sow live-weight and back-fat depth during gestation are in ensuring optimum sow productivity is important. The objective of this study was to quantify the association between sow parity, live-weight and back-fat depth during gestation with subsequent sow reproductive performance. Records of 1058 sows and 13 827 piglets from 10 trials on two research farms between the years 2005 and 2015 were analysed. Sows ranged from parity 1 to 6 with the number of sows per parity distributed as follows: 232, 277, 180, 131, 132 and 106, respectively. Variables that were analysed included total born (TB), born alive (BA), piglet birth weight (BtWT), pre-weaning mortality (PWM), piglet wean weight (WnWT), number of piglets weaned (Wn), wean to service interval (WSI), piglets born alive in subsequent farrowing and sow lactation feed intake. Calculated variables included the within-litter CV in birth weight (LtV), pre-weaning growth rate per litter (PWG), total litter gain (TLG), lactation efficiency and litter size reared after cross-fostering. Data were analysed using linear mixed models accounting for covariance among records. Third and fourth parity sows had more (P<0.05) TB, BA and heavier BtWT compared with gilts and parity 6 sow contemporaries. Parities 2 and 3 sows weaned more (P<0.05) piglets than older sows. These piglets had heavier (P<0.05) birth weights than those from gilt litters. LtV and PWM were greater (P<0.01) in litters born to parity 5 sows than those born to younger sows. Sow live-weight and back-fat depth at service, days 25 and 50 of gestation were not associated with TB, BA, BtWT, LtV, PWG, WnWT or lactation efficiency (P>0.05). Heavier sow live-weight throughout gestation was associated with an increase in PWM (P<0.01) and reduced Wn and lactation feed intake (P<0.05). Deeper back-fat in late gestation was associated with fewer (P<0.05) BA but heavier (P<0.05) BtWT, whereas deeper back-fat depth throughout gestation was associated with reduced (P<0.01) lactation feed intake. Sow back-fat depth was not associated with LtV, PWG, TLG, WSI or piglets born alive in subsequent farrowing (P>0.05). In conclusion, this study showed that sow parity, live-weight and back-fat depth can be used as indicators of reproductive performance. In addition, this study also provides validation for future development of a benchmarking tool to monitor and improve the productivity of modern sow herd.     

Body weight loss during lactation and its influence on weaning-to-service interval and ovulation rate in Landrace and Yorkshire sows in the tropical environment of Thailand

The aim of this study was to investigate the ovulation rate and the weaning-to-service interval (WSI) of sows in relation to their body weight loss during lactation in tropical climatic conditions. Effect of lactation length (LL), number of total born piglets, number of live born piglets, litter birth weight, average piglet birth weight, number of pigs weaned, litter weaning weight and average pig weaned weight on sow weight loss during lactation were also studied. This study was conducted in two commercial purebred sow herds (A, B) in the central part of Thailand from August to December 1997. The herds had both Landrace (L) and Yorkshire (Y) sows. The 123 sows (55 L and 68 Y) in herd A and 153 sows (95 L and 58 Y) in herd B, parity 1-4, were weighed within 4 days after farrowing and at weaning. Lactation length, litter size at birth and at weaning, litter weight at birth and at weaning, and WSI were recorded for each of these sows. In herd A, 52 sows (20 L and 32 Y) were examined once by laparoscopy between days 8 and 14 after AI-service. These sows had farrowed at least seven piglets in the previous parturition. The numbers of corpora lutea (CL) in both ovaries were counted, and were assumed to equal the ovulation rate. L-sows had significantly (P < 0.05) higher relative weight loss during lactation (RWL) than Y-sows. The RWL increased by 0.7% for each extra pig weaned. When LL increased by 1 day, within the interval of 17-34 days, RWL decreased by 0.6%. Sows with a high weight loss had significantly (P < 0.05) longer WSI than sows with medium or low weight loss. Weight loss had a significant (P < 0.05) effect on WSI in parity 1 and 2 sows. Y-sows had more CL than L-sows (15.7 versus 14.0) (P < 0.05). RWL, parity and regression on lactation length had no significant effect on number of CL. In conclusion, sows with higher number of pigs weaned lose more weight. Under the restricted feeding regime applied, high weight loss during lactation prolongs WSI in parity 1 and 2 sows, but has no influence on the ovulation rate at first oestrus after weaning. The ovulation rate is higher in Yorkshire than in Landrace sows. The ovulation rate is independent of parity.     

Oestrus and LH responses to oestradiol during lactational anoestrus in Chinese Meishan and large white sows.

To investigate endocrine mechanisms associated with the occasional occurrence of fertile oestrus during lactation in the high prolific Chinese Meishan (MS) breed, the incidence of oestrus and changes in plasma luteinizing hormone (LH) levels before and after oestradiol benzoate (OB, 15 micrograms/kg body weight) administration on day 22 was compared in 4 MS and 6 Large White (LW) sows. All sows exhibited oestrus in response to OB. Only 1 sow (MS) ovulated in response to OB, became pregnant and farrowed. Mean plasma LH levels before OB were low (MS: 0.38 +/- 0.06 ng LH/ml, LW: 0.29 +/- 0.04 ng LH/ml, ns). LH levels above 2 ng/ml (surge) occurred in 2/4 MS and 2/6 LW sows at 60 +/- 5 h after OB. The MS sow that ovulated had an LH surge level of 4.5 ng/ml plasma at 40 h after OB. These results indicate minor breed differences in the control of LH secretion during lactational anoestrus.     

Automatic detection of lameness in gestating group-housed sows using positioning and acceleration measurements

Lameness is an important issue in group-housed sows. Automatic detection systems are a beneficial diagnostic tool to support management. The aim of the present study was to evaluate data of a positioning system including acceleration measurements to detect lameness in group-housed sows. Data were acquired at the Futterkamp research farm from May 2012 until April 2013. In the gestation unit, 212 group-housed sows were equipped with an ear sensor to sample position and acceleration per sow and second. Three activity indices were calculated per sow and day: path length walked by a sow during the day (Path), number of squares (25×25 cm) visited during the day (Square) and variance of the acceleration measurement during the day (Acc). In addition, data on lameness treatments of the sows and a weekly lameness score were used as reference systems. To determine the influence of a lameness event, all indices were analysed in a linear random regression model. Test day, parity class and day before treatment had a significant influence on all activity indices (P<0.05). In healthy sows, indices Path and Square increased with increasing parity, whereas variance slightly decreased. The indices Path and Square showed a decreasing trend in a 14-day period before a lameness treatment and to a smaller extent before a lameness score of 2 (severe lameness). For the index acceleration, there was no obvious difference between the lame and non-lame periods. In conclusion, positioning and acceleration measurements with ear sensors can be used to describe the activity pattern of sows. However, improvements in sampling rate and analysis techniques should be made for a practical application as an automatic lameness detection system.     

Shifting sows: longitudinal changes in the periparturient faecal microbiota of primiparous and multiparous sows

Knowledge of periparturient longitudinal changes in sow microbiota composition is necessary to fully understand her role in the development of the piglet microbiota, but also to improve gut health and performance of the sow in lactation. Primiparous sows face the challenge of partitioning nutrients to support maternal growth in addition to supporting foetal growth and the demands of lactation. Additional metabolic stress present during the periparturient period may induce changes in the microbiota profile between primiparous and multiparous sows. Using 16S rRNA gene sequencing, the study aimed to characterise the longitudinal changes in the periparturient microbiota and identify differences within the sow microbiota profile associated with parity. Faecal samples from primiparous (n = 13) and multiparous (n = 16) sows were collected at four different time points (day - 6, - 1, 3 and 8) in relation to farrowing (day 0). Microbiota richness was lowest on day 3 and - 1 of the periparturient period (P < 0.05). Microbiota community composition, assessed by weighted and unweighted UniFrac distances, demonstrated longitudinal changes, with day 3 samples clustering away from all other sampling time points (P < 0.05). The relative abundance of several genera segregated gestation from lactation samples including Roseburia, Prevotella 1, Prevotella 2, Christensenellaceae R-7 group, Ruminococcaceae UCG-002 and Ruminococcaceae UCG-010 (P < 0.01). Furthermore, day 3 was characterised by a significant increase in the relative abundance of Escherichia/Shigella, Fusobacterium and Bacteroides, and a decrease in Alloprevotella, Prevotellaceae UCG-003 and Ruminococcus 1 (P < 0.001). Primiparous sows had overall lower periparturient microbiota diversity (P < 0.01) and there was a significant interaction between parity and sampling time point, with primiparous sows having lower microbiota richness on day - 6 (P < 0.001). There was a significant interaction between sow parity and sampling time point on microbiota composition on day - 6 and - 1 (unweighted UniFrac distances; ≤ 0.01) and day 8 (weighted and unweighted UniFrac distances; P < 0.05). Whilst no significant interactions between sow parity and sampling day were observed for genera relative abundances, multiparous sows had a significantly higher relative abundance of Bacteroidetes dgA-11 gut group and Prevotellaceae UCG-004 (P < 0.01). This study demonstrates that the sow microbiota undergoes longitudinal changes, which are collectively related to periparturient changes in the sow environment, diet and physiological changes to support foetal growth, delivery and the onset of lactation, but also sow parity.     

Repeat breeding and subsequent reproductive performance in Swedish Landrace and Swedish Yorkshire sows

The objective of the present study was to analyse the association between repeat breeding (RB) in gilts/sows and their subsequent reproductive performance as well as the impact of interactions between repeat breeding and factors like parity number, boar breed, season and mating type (MT) on subsequent reproductive performance in Swedish Landrace (L) and Swedish Yorkshire (Y) sows. Data analysed included 7040 sows (3654 L and 3386 Y), farrowing during January 1994 until December 1999 in 11 L and 8 Y nucleus herds. The study was assigned as a cohort design and the aim was to study gilts/sows from their first mating as gilts until mating after third parity. Analysis of variance was applied to continuous data and logistic regression was applied to categorical data. Percentages of litters as a result of repeat breeding in sow parities 1-3 were 6.1, 12.0 and 6.3% for L sows and 6.7, 13.1 and 7.4% for Y sows. For parity 3, the incidence of litters resulting from repeat breeding was significantly higher (P<0.001) in Y than in L sows. The proportion of irregular return to oestrus (>24 days after first mating) was higher (P<0.01) in primiparous sows than in multiparous sows (69% versus 61%). On average, litters resulting from repeat breeding were larger (P<0.001) than litters resulting from non-repeat breeding (NR) (about 0.5 piglets per litter) in both L and Y sows. For Y sows, if the previous litter was a result of repeat breeding, the subsequent reproductive cycle had 2.7% higher RR (P<0.05) and 2.4% lower FR (N.S.) compared with sows that were not repeat bred. The same trend was found in L sows (1.4% higher RR and 1.3% lower FR) but the differences were not significant. Among the sows removed from the herds, about 24% of L and 28% of Y were culled due to reproductive problems (gilts not included). In addition, a number of sows from these nucleus herds were also culled due to low breeding value and poor conformation.     

Fertility of sows injected with exogenous oestradiol and/or gonadotrophins to control post-weaning oestrus

In the first of two experiments 28 multiparous sows were allocated to one of the following treatments 2 days after weaning at approximately 35 days post partum: (1) untreated; (2) i.m. injection 10 μg oestradiol benzoate (OB)/kg body weight (b.wt.); and (3) i.m. injection 20 μg OB/kg b.wt. Sows were bred at first post-weaning oestrus and ovulation rate assessed at slaughter. The mean interval from weaning to oestrus in each group was: (1) 5.6 ± 0.2; (2) 4.7 ± 0.2; and (3) 4.7 ± 0.2 days; the mean ovulation rates in groups 1 and 2 (18.7 ± 0.6 and 17.4 ± 1.8, respectively) were significantly higher (P < 0.01) than that of 12.0 ± 1.7 for treatment 3 sows. Two untreated and one each of the treated sows were not cycling at slaughter.In the second experiment 75 multiparous sows weaned at 28 ± 3 days post partum (day 0) were evenly allocated with respect to parity to one of four treatment groups: (1) untreated; (2) i.m. injection 10 μg OB/kg b.wt. on day 2; (3) PG600 (400 iu PMSG + 200 iu hCG) injection subcutaneous day 0; and (4) combined PG600/OB treatment as in (2) and (3) above. Sows were bred naturally at the first post-weaning oestrus and fertility assessed at farrowing. Control animals had a significantly longer (P < 0.05) weaning to oestrus interval (4.53 ± 0.25 days) compared to treatment 2 (4.03 ± 0.13) treatment 3 (3.97 ± 0.12) and treatment 4 (3.81 ± 0.07) sows. Sows treated with PG600 alone showed a significant increase (P < 0.05) in numbers born live compared to pre-treatment values. A smaller and non-significant increase in numbers born live in control sows (probably related to increasing parity) was not observed in either OB- or PG600/OB-treated animals.These results suggest that with further modification of the treatments, a system may be developed for introducing fixed-time artificial insemination (AI) or mating as a means of controlling the reproductive performance of the weaned sow.     

Effects of lysine intake during late gestation and lactation on blood metabolites, hormones, milk composition and reproductive performance in primiparous and multiparous sows

Modern genotype primiparous and multiparous sows (Yorkshire x Landrace, n=48) were used to evaluate effects of dietary lysine intake during late gestation and lactation, and their interaction on reproductive performance. Sows were randomly allotted to two gestation lysine (G, 0.6% or 0.8% lysine) treatments based on parity in a 2 x 2 factorial arrangement, and each treatment had 12 replicates comprising 1 sow. Then all the sows were assigned to two lactation lysine (L, 1.0% or 1.3% lysine) treatments within parity and gestation treatments in a 2 x 2 x 2 factorial design, and each treatment comprised six replicates with 1 sow/replicate during lactation. Feeding higher lysine level during gestation increased sow body weight and backfat thickness (P=0.001) and body condition was better (P=0.001) in multiparous than that of primiparous sows. Both of the lysine levels during lactation and parity influenced sow body condition and reproductive performance (P<0.05). Higher lysine intake during lactation increased the concentrations of total solids (P=0.024), protein (P=0.001) and solids not-fat (P=0.042) in colostrum and total solids (P=0.001), protein (P=0.001), fat (P=0.001) and solids not-fat (P=0.005) in milk. Protein concentration of milk was greater (P=0.001) in multiparous sows than that of primiparous sows. Feeding of high lysine diets resulted in an increment of plasma urea N (P=0.010; P=0.047) and a decrease of creatinine (P=0.045; P=0.002) on the day of postfarrowing and weaning, respectively. Furthermore, as lysine intake increased, the secretions of insulin, FSH, and LH were increased (P<0.05) and multiparous sows showed higher (P<0.05) concentrations of FSH and LH pulses on the day of postfarrowing and weaning, respectively. These results indicated that higher lysine intake than that recommended by NRC [NRC, 1998. Nutrient Requirements of Swine, 10th ed. National Academy Press, 458 Washington, DC] could improve sow performance during late gestation and lactation. Furthermore primiparous sows need higher lysine intake than multiparous sows. Moreover, nutritional impacts on reproduction may be mediated in part through associated effects on circulating LH concentration.     

Effects of parity, season, gonadotropin releasing hormone and altered suckling intensity on the interval to rebreeding in sows

Two experiments were conducted to determine the effects of a) parity and season of the year on the interval from weaning to rebreeding in sows and b) altered suckling intensity (ASI) and gonadotropin releasing hormone (GnRH) on the postpartum interval in primiparous and multiparous sows. Experiment I included 406 weaning-to-rebreeding intervals in 172 primiparous and multiparous sows. Primiparous sows returning to estrus during the spring and summer months had a longer (P<0.001) rebreeding interval (11.0 d) than the other groups (5.7 d). In Experiment II, 32 sows were assigned to a factorially designed experiment. The factors were ASI, GnRH and parity. Treatments were begun 7 d before weaning (about 4 wk of age). The ASI was accomplished by separating the sow from her litter for 12 h each day. The average interval from the beginning of treatment to the onset of estrus was 13.4 d and was not affected (P>0.33) by ASI, GnRH, parity or their interactions. None of the factors was found to affect the average weaning weight of the piglets (P>0.05); however, piglets in the ASI group were heavier (P<0.03) at 1-wk postweaning than those in the no-ASI group. The results showed that primiparous sows returning to estrus during the spring and summer months had the longest rebreeding interval. Additionally, neither GnRH nor ASI, separately or in conjunction, decreased the postpartum interval in sows.     

Effects of continuous elevated cortisol concentrations during oestrus on concentrations and patterns of progesterone, oestradiol and LH in the sow

This study investigated the effect of continuous elevated cortisol concentrations during standing oestrus on time of ovulation and patterns of progesterone, oestradiol and luteinising hormone (LH) in sows. The elevation of cortisol concentrations was achieved through repeated intravenous injections of synthetic adrenocorticotropic hormone (ACTH) every 2 h for approximately 48 h, from the onset of the second standing oestrus after weaning. Treatment was terminated when ovulation was detected (monitored by transrectal ultrasonography every 4h) or when the sow had received a maximum of 24 injections. The dose of ACTH (2.5 microg/kg) was chosen to mimic the cortisol concentrations seen during mixing of unfamiliar sows. The sows (n=14) were surgically fitted with jugular vein catheters and randomly divided into a control (C group where only NaCl solution were injected) or an ACTH group. Blood samples were collected every 2 h. In parallel with the blood sampling, saliva samples for cortisol analyses were taken from eight sows before onset of treatment and from four of the sows during treatment. There was no difference in time from onset of standing oestrus to ovulation between the two groups. The interval between the peaks of oestradiol and LH to ovulation was prolonged in the ACTH group compared to the C group (p<0.05), with a tendency towards an earlier decline of oestradiol in the ACTH group. Cortisol and progesterone concentrations were significantly elevated during treatment in the ACTH group (p<0.001), with cortisol peak concentrations occurring between 40 and 80 min after each ACTH injection. Cortisol concentrations in saliva and plasma were highly correlated (p<0.001). In conclusion, elevated cortisol concentrations from the onset of standing oestrus increase progesterone concentrations and prolong the interval between oestradiol and LH peaks to ovulation, the latter possible due to an early decline in oestradiol concentrations and a change of the LH peak outline. The effect these hormonal changes have on reproductive performance need to be further investigated. Saliva samples might be a useful and non-invasive method to assess cortisol concentrations in sows.     

Impact of ACTH administration on the oviductal sperm reservoir in sows: the local endocrine environment and distribution of spermatozoa

The objective of the study was to investigate if short-term stress in sows (simulated by injections of synthetic adrenocorticotrophic hormone (ACTH)) during standing oestrus had a negative effect on the local environment in the utero-tubal junction (UTJ) and isthmus and the distribution of spermatozoa in these segments. Fourteen sows were monitored for ovulation using ultrasonography in two consecutive oestruses. The sows were fitted with jugular catheters and, from onset of the second oestrus, blood samples were collected every second hour. In the 2nd oestrus, seven sows were given ACTH every second hour, from the onset of standing oestrus until the sow ovulated (ACTH-group), whereas the other seven sows remained as controls (C-group) and were given NaCl solution. The sows were artificially inseminated 16-18 h before expected ovulation. Six hours after ovulation the sows were anaesthetised, and blood samples were repeatedly taken from veins draining the uterus and the UTJ-isthmus, respectively. This oviduct was thereafter removed and divided in four adjacent sections consisting of: (i) the UTJ, (ii) the first, and (iii) the second isthmus segment prior to (iv), the ampullary-isthmic junction (AIJ) and the ampulla. The three first-mentioned segments were flushed to retrieve spermatozoa, whereas the last one was flushed to collect oocytes/ova. The number of spermatozoa attached to the zona pellucida was counted. The concentrations of cortisol in jugular blood of the ACTH-group sows during the time of ACTH-injections were significantly higher than of the C-group sows (p<0.05), as were the levels of progesterone (p<0.001). Progesterone and cortisol concentrations measured in the blood samples draining the UTJ-isthmic region 6 h after ovulation did not significantly differ between the groups, but the C-group displayed significantly higher concentrations of progesterone in the UTJ-isthmic region compared with the levels measured in parallel samples taken of jugular blood (p<0.01). The C-group, but not the ACTH-group, also displayed a significant elevation in progesterone concentration 6h after ovulation compared with the basal levels before ovulation (p<0.01). Numbers of retrieved spermatozoa were not significantly different between the C-group and the ACTH-group. However, there was a tendency for a larger number of spermatozoa among sows in the ACTH-group, especially in the isthmic segment adjacent to the AIJ. In conclusion, simulated stress induced by injections of ACTH during standing oestrus results in elevated concentrations of progesterone before ovulation and may interfere with the rise of progesterone after ovulation. However, ACTH-injections appeared to augment transport of spermatozoa through the female genital tract of pigs.