Effect of Modified Eros Centre on Some Reproductive Parameters of the Sow

The effect of a modified eros centre on weaning to oestrus interval, follicle size, ovulation and farrowing rate and total born litter size was investigated. In modified eros centre 94.4% and in group housing 79.1% of the sows (p < 0.01) expressed oestrus within 10 days post‐weaning. Weaning to oestrus interval was shorter (p < 0.001) for sows kept in modified eros centre. The interval from onset of oestrus to the time of ovulation was longer for sows in group housing (p=0.05). The time of ovulation was negatively correlated (r=?0.50) with the interval from weaning to oestrus (p=0.005). The time of ovulation after onset of oestrus was significantly (p < 0.05) shorter for sows expressing oestrus within 2–4 days of weaning, compared with the animals that expressed oestrus between days 5 and 6 post‐weaning and was shortest for sows expressing oestrus after day 6 post‐weaning. Farrowing rate was not affected by a modified eros centre. Litter size tended to be smaller in group‐housed weaned sows (p=0.10). The timing of last artificial insemination relative to time of ovulation did not affect litter size (p > 0.10). The implication of these results is that a modified eros centre may improve some of the post‐weaning oestrous parameters of the sow.     

Fixed‐time post‐cervical artificial insemination in weaned sows following buserelin use combined with/without eCG

Fixed‐time post‐cervical artificial insemination (FTAI) drastically reduces labour requirements and increases the use of boars with higher genetic merit. This study evaluated the efficiency of eCG administration combined with/without the GnRH agonist buserelin for the induction and synchronization of ovulation in weaned sows submitted to FTAI. The sows were allocated into three groups. In the control group, the first artificial insemination was performed at the onset of oestrus and repeated every 24 hr. In the eCG+GnRH group, sows received 600 IU eCG at weaning and buserelin (10 μg) after 86–89 hr of eCG, and in the GnRH group, sows received only buserelin after 86–89 hr of weaning. The hormone‐treated sows received a single FTAI after 30–33 hr of buserelin application. All the sows were inseminated with homospermic doses (1.5 × 10⁹ sperm cells/50 ml). The interval between weaning and ovulation was shorter (p < .05) in the eCG+GnRH (133.3 hr) and GnRH (135.9 hr) groups than the control (141.5 hr) group. In the eCG+GnRH group, the sows ovulated earlier (p < .05) than those in the GnRH group (44.5 vs. 48.2 hr after buserelin administration). The reproductive performance of GnRH sows was not compromised when only sows exhibiting oestrus at the time of insemination were considered, but lower farrowing rate and smaller litter size were observed in eCG+GnRH sows. The reproductive performance of eCG+GnRH sows was primarily compromised because the insemination was performed outside the optimal time relative to ovulation; therefore, it is advisable to inseminate them before 116–122 hr after weaning.     

The Post‐Cervical Insemination does not Impair the Reproductive Performance of Primiparous Sows

The study evaluated the reproductive performance of primiparous sows submitted to post‐cervical insemination (PCAI) compared with cervical artificial insemination (CAI). Difficulty with catheter introduction, the occurrence of bleeding or semen backflow during insemination, and volume and sperm cell backflow up to 60 min after insemination were also evaluated. Sows were homogenously distributed, according to body weight loss in lactation, lactation length, weaned piglets, weaning‐to‐oestrus interval and total born in previous farrowing, in two treatments: PCAI (n = 165) with 1.5 × 10⁹ sperm cells in 45 ml (2.4 ± 0.04 doses per sow) and CAI (n = 165) with 3 × 10⁹ sperm cells in 90 ml (2.5 ± 0.04 doses per sow). During PCAI, sows were inseminated in the absence of boars. Transabdominal real‐time ultrasonography was performed at oestrus onset, immediately before the first insemination and at 24 h after last insemination. There was no difference (P > 0.05) between treatments in farrowing rate (91.5% × 89.1%) and litter size (12.5 × 11.9 piglets born, respectively for PCAI and CAI sows). Successful passage of the intrauterine catheter in all the inseminations was possible in 86.8% (165/190) of sows initially allocated to PCAI treatment. Difficulty of introducing the catheter in at least one insemination did not affect the reproductive performance of PCAI sows (P > 0.05). Bleeding during insemination did not affect (P > 0.05) the farrowing rate in both treatments, but litter size was reduced in CAI and PCAI sows (P ≤ 0.06). Percentage of spermatozoa present in backflow within 1 h after insemination was greater in CAI than PCAI sows (P < 0.01). More than 85% of primiparous sows can be successfully post‐cervical inseminated with doses containing 1.5 × 10⁹ sperm cells in the absence of the boar during insemination without impairing the reproductive performance.     

A study on primiparous sows of the ability to show standing oestrus and to ovulate after weaning. Influences of loss of body weight and backfat during lactation and of litter size, litter weight gain and season

The ability to show standing oestrus and to ovulate within 10 days of weaning was studied in 240 purebred Swedish Yorkshire primiparous sows, fed according to a conventional feeding regime during lactation. The sows were weighted and backfat depth was recorded at farrowing and at weaning. Oestrus control was performed daily and blood samples for determination of plasma progesterone were drawn regularly in 205 sows. The distribution among the sows of the first standing oestrus after weaning had 2 peaks. The first peak occurred within 10 days of weaning and the second 24-30 days after weaning. Twelve per cent of the sows ovulated without showing standing oestrus within 10 days of weaning and 4% had an anovulatory first oestrus within the same time. Significant differences in age at farrowing and in loss of weight and backfat during lactation were found between sows which both showed standing oestrus and ovulated within 10 days of weaning and sows which neither showed standing oestrus, nor ovulated within the same time. The season during which weaning occurred significantly influenced the ability to show standing oestrus and ovulate within 10 days of weaning. Among the sows which both showed standing oestrus and ovulated within 10 days of weaning, significant positive correlations were found between weight loss, litter size, litter weight gain and the interval from weaning to first standing oestrus.     

Effect of β‐carotene on health status and performance of sows and their litters

A total of 48 sows were allocated to four groups (12 sows per group) at the 99th day of pregnancy and were treated throughout two consecutive breeding cycles, as follows: (a) control group: no treatment; (b) group BC1: 400 mg β‐carotene/sow/day via feed from 7 days prior to the expected farrowing, until the 30th day postservice; (c) group BC2: 400 mg β‐carotene/sow/day via feed from 7 days before weaning up to service, followed by 200 mg β‐carotene until the 30th day postservice; and (d) group BC inj: four intramuscular (i.m.) injections of 200 mg β‐carotene/sow (on the 100th day of pregnancy, on the day of farrowing, on the day of weaning and on the first day of oestrus). Serum β‐carotene equivalents, vitamin A and IgG concentrations were determined in sows at several times of the breeding cycle. Moreover, serum IgG concentrations were determined in piglets on the second day of lactation and at weaning. Data relating to sow reproductive parameters and litter parameters were also recorded. It was shown that concentrations of serum β‐carotene equivalents were elevated only in the BC inj group during lactation and at service, while serum vitamin A concentrations were also elevated in the BC inj group only at oestrus. There was no effect of β‐carotene on the oestrus intensity score, the weaning‐to‐oestrus interval, the number of returns to oestrus per sow and the farrowing‐to‐farrowing interval. The number of piglets born alive was greater in the BC inj group compared with the controls, while the litter size at weaning was greater in the groups BC1, BC2 and BC inj compared with the control group (p < 0.05). Supplementation of β‐carotene did not appear to influence the serum IgG concentration in sows and piglets.     

Effects of breeding at the second oestrus or after post-weaning hormonal treatment with altrenogest on subsequent reproductive performance of primiparous sows

This study investigated the effects of breeding at the second oestrus after weaning or after feeding an orally active progestagen (altrenogest) on the subsequent reproductive performance of primiparous sows. After 3 weeks of lactation, 663 weaned sows of two genotypes were allocated into three groups: G1--breeding at the first oestrus after weaning; G2--breeding at the second oestrus after weaning and G3--treatment with altrenogest for 5 days after weaning and breeding at the first oestrus after the end of the treatment. Body weight at breeding was lower in G1 and G3 than in G2 sows (p < 0.05). The interval to show oestrus was similar for G1 and G2 groups (p > 0.05) but higher (p < 0.05) than that observed in G3 group. Within genotype A, percentages of females in oestrus within 10 days were not different (p > 0.05) among groups, whereas in genotype B, more G1 and G2 sows (p < 0.05) showed oestrus than G3 sows. In both genotypes, lower farrowing rates were observed in G3 than in G1 and G2 sows (p < 0.05) and a greater litter size (p < 0.05) was observed in G2 sows. In genotype A, the number of total born piglets was similar for G1 and G3 groups (p > 0.05), whereas in genotype B, G1 sows had a greater litter size than G3 sows (p < 0.05). Body weight at weaning and at breeding was similar (p > 0.05) between farrowed and non-farrowed sows in all groups. Reproductive performance is not improved in primiparous sows treated with altrenogest during 5 days after weaning. The reproductive performance of genotype B sows is compromised in Control and Altrenogest-treated sows but not in those bred at the second oestrus after mating. Breeding at the second oestrus after weaning allows primiparous sows to gain weight between weaning and service, and increases their farrowing rate and subsequent litter size.     

Uterine Insemination with a Standard AI Dose in a Sow Pool System

The effect of uterine AI with a standard dose of spermatozoa on fertility of the sow was studied in a field trial. The trial involved a sow pool system with 440 sows using AI as the primary method of breeding. Sows were twice a day checked for oestrus symptoms by back pressure test in front of a boar on days 3–6 after weaning. When in standing heat, sows were randomly allocated into either a uterine insemination group (UTER, n = 157) or standard AI group (CONT, n = 169) and bred accordingly using 3 billion spermatozoa in 80 ml of extender. In both treatment groups, insemination was repeated once if the sow was still receptive 24 h later. Using pregnancy (farrowed or not) and live‐born litter size as the outcome variables, a logistic and linear regression approach, respectively, was taken to study the effect of the following factors: treatment (UTER vs CONT), AI operator, breed, satellite herd preceding weaning, parity, weaning‐to‐oestrus interval and length of lactation. Overall, live‐born litter size was 11.3 ± 2.9, repeat breeding rate 4.2% and farrowing rate 91.2%. In the UTER group, 93.6% of inseminated sows farrowed, whereas farrowing rate for the CONT group was 88.8% (p = 0.13). Intrauterine insemination with a standard AI dose did not result in a significant improvement in the live‐born litter size (11.5 ± 2.8 for the UTER and 11.1 ± 3.0 for the CONT sows, respectively, p = 0.13). However, the preceding satellite herd had a highly significant effect on the live‐born litter size (12.4 ± 2.6; 11.1 ± 2.9; 10.8 ± 2.9 and 10.9 ± 2.9 for the four satellite herds, p < 0.01). We conclude that uterine insemination did not have a significant effect on live‐born litter size and farrowing rate and we also conclude that satellite herd appears to have a major effect on fertility in a sow pool system.     

Sow performance and maternal behaviour in organic and conventional herds

Abstract

The study evaluates the first three parities of 144 Swedish Landrace×Yorkshire sows from three certified organic and three conventional commercial piglet-producing herds. Sows and litters were weaned at seven and five weeks post partum (pp) in organic and conventional herds, respectively. Herdsmen judged sow behaviour and maternal ability at farrowing, two weeks pp and at weaning. Herdsmen collected registrations of litter size, litter weight and sow fat status at farrowing and at weaning. Piglet mortality and oestrous signs were registered continuously during the nursing period. Sows in organic herds were scored to be more cautious among piglets, and to have better nursing behaviour and maternal ability in early lactation than sows in conventional herds. Piglet mortality was higher in organic than in conventional herds. Oestrus during lactation was only observed among sows in organic herds, and sows showing oestrus during lactation were fatter at weaning.     

Effects of L‐citrulline supplementation on heat stress physiology,lactation performance and subsequent reproductive performance of sows in summer

Lactating sows are susceptible to heat stress (HS). Part of the thermoregulatory response to HS is to increase peripheral blood flow, which is mediated in part by the vasodilator, nitric oxide (NO). Therefore, the aim of this experiment was to determine the effect of supplementation of L‐citrulline, a NO precursor, on symptoms of HS, lactation performance and subsequent reproductive performance of sows in summer. A total of 221 summer farrowing mixed parity sows were fed either a control diet or supplemented with 1% L‐citrulline upon entry to the farrowing house (6 ± 1.8 days for mean ± standard deviation [SD] before farrowing) until weaning (26 ± 1.5 days). The average daily minimum and maximum temperature in the farrowing house was 21.0 ± 1.88 and 29.2 ± 3.82°C (mean ± SD). Rectal temperature, respiration rate, and plasma and urinary nitrite and nitrate (NOx) of sows were measured on the 19th day post‐farrowing. Supplemental L‐citrulline in the diet did not affect the number of piglets born alive, feed intake of sows, body weight or backfat thickness of sows at weaning, or litter weight gain. L‐citrulline tended to reduce piglet pre‐weaning mortality rate from 18.6% to 15.6% (p = 0.058). L‐citrulline reduced the respiration rate of sows compared to the control diet at 17:00 hr (Time × Diet, p < 0.001); however, rectal temperature was not affected. L‐citrulline tended to increase urinary NOx concentrations (127 vs. 224 µM, p = 0.057) but not plasma NOx concentrations. L‐citrulline did not affect farrowing rate or number of piglets born alive in the subsequent parity. In conclusion, L‐citrulline supplementation reduced respiration rate of lactating sows and reduced piglet pre‐weaning mortality rate in summer. Whether the effects were due to a NO‐dependent mechanism requires further validation.     

The Effect of Post-Ovulatory Artificial Insemination on Sow Reproductive Performance

In order to increase reproductive performance, sows are usually inseminated several times during oestrus. In practice, this results in a significant number of sows receiving one or more post‐ovulatory inseminations. This study was carried out to determine the percentage of sows that receive one or more post‐ovulatory inseminations and the effect of such treatment on reproductive performance. The results were analysed from a total of 1298 sows on two farms. It was observed that more than 70% of the sows received at least one post‐ovulatory insemination and approximately 20% received two or more. There was no observed effect on the rate of return to oestrus, farrowing rate or litter size (p > 0.05).     

Verification of the usefulness of Estrophan inj. Spofa in the control of reproductive parameters in sows after weaning of piglets]

Cloprostenol, a prostaglandin F2-alpha analogue, used in the Czechoslovak preparation Oestrophan ing. Spofa was tested by a new nontraditional use. The effect of cloprostenol use on reproductive parameters of sows after piglet weaning was followed in a set of 456 experimental and 434 control sows. The effect of single intramuscular instillation of cloprostenol was tested in five partial observations: to multiparous sows at a dose of 175 micrograms on the day of weaning (experimental group no. 1), on day 1 after weaning (group no. 2), 500 micrograms on day 1 after weaning (group no.3), to primiparous sows at a dose of 500 microgram on day 1 after weaning (group no. 4). The treatment used in group no. 4 was also applied to 42 primiparous sows kept on a farm with regular occurrence of post-weaning anoestria of sows (experimental group no. 5). These parameters were evaluated: dynamics of oestrus onset within five, and/or ten, days after weaning, average length of the weaning--first insemination interval, conception rate after the first insemination in dependence on terminated deliveries and parameters of piglet litter. Cloprostenol application did not have a statistically significant effect on the evaluated reproductive parameters. The percentage of multiparous, and/or primiparous, sows in which the oestrus onset was not detected by the 10th day after weaning, did not show any large differences in the various experimental and control groups (17.09 vs. 16.55%, 23.53 vs. 32.56%, 13.66 vs. 18.13%, 29.54 vs. 30.30%; P > 0.05). On the farm with regular occurrence of post-weaning anoestria there were 73.81% of primiparous sows with oestrus onset after cloprostenol instillation and 71.43% primiparous sows without treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproductive Performance of Purebred Swedish Landrace and Swedish Yorkshire Sows: I. Seasonal Variation and Parity Influence

The objective of this retrospective study was to investigate the causes of variation in the reproductive performance of purebred Swedish Landrace (L) and Swedish Yorkshire (Y) sows. Data analysed comprised farrowings from 1994 through 1997 from 19 Swedish nucleus herds and included 20 275 litters from 6989 purebred sows (3598 L and 3491 Y). The main traits analysed were litter size, weaning-to-first-service interval (WSI), farrowing rate, remating rate and age at first farrowing. Analysis of variance was used for the statistical analysis of quantitative data. Logistic regression analysis was applied for binary data using the GLIMMIX macro in the SAS program. Factors included in the analyses were breed of sow, breed of boar, parity number, herd-year combination within breed, mating type (natural mating or artificial insemination), lactation length and month of the year. L sows, compared with Y sows, produced larger litters [11.61 vs 11.54 total born/litter (ns) and 10.94 vs 10.58 born alive/litter (P<0.001)] and had a longer WSI (5.5 vs 5.4 days, P<0.001), a higher farrowing rate (82.8 vs 80.9% units, P<0.05) and a lower remating rate (6.2 vs 8.8% units, P<0.001). On average, L sows were younger at first farrowing than Y sows (355.6 vs 368.6 days, P<0.001). The seasonal influence on WSI was greater for primiparous sows than for multiparous sows. Primiparous sows weaned from June to October had a longer WSI than those weaned from January to May or in November (P<0.05). Mating in August resulted in the lowest farrowing rate and the highest remating rate. The seasonal influence on farrowing rate and WSI was more pronounced in Y sows than in L sows. However, season had no significant influence on litter size in either L or Y sows.     

Dietary administration of probiotics to sows and/or their neonates improves the reproductive performance,incidence of post‐weaning diarrhea and histopathological parameters in the intestine of weaned piglets

Probiotics have gained considerable attention with respect to their beneficial effects on livestock performance and health. The most significant effects of probiotics on the gut microbiota and the host animals take place when they are included in diets during particularly stressful periods such as weaning and/or at the beginning of the lactation period. The probiotics Bacillus mesentericus strain TO‐A at 1 × 10⁸ colony forming units (CFU)/g, Clostridium butyricum strain TO‐A at 1 × 10⁸ CFU/g and Enterococcus faecalis strain T‐110 at 1 × 10⁹ CFU/g were used. Litter weight at delivery and ratio of return to estrous improved significantly (17% and 24% improvement, respectively) by probiotic administration to sows (0.2% (w/w)). Furthermore, the feed intake of the probiotics‐administered sows was greater than that of the control sows during the late lactation period. Post‐weaning diarrheal incidence and growth performance was improved by probiotics administration to neonates (0.02% (w/w)), while the combined use of probiotics in sows and their neonates induced the enlargement of villous height and prevented muscle layer thinning in the small intestine of weaning piglets. The administration of probiotics of three species of live bacteria improved the porcine reproductive performance around stressful periods of sows (farrowing) and piglets (weaning). [Corrections added on 26 April 2016, after first online publication: ‘Enterococcus faecalis strain T‐100’ has been corrected to ‘Enterococcus faecalis strain T‐110’ in the above paragraph and in the ‘Probiotics’ section under the Materials and Methods heading.]     

Prevention of anestrus in sows after the 1st and 2d parturition

The procedure of prevention of anoestria after the weaning of piglets was verified in 389 experimental and 332 control sows of the Prestice breed. The set of animals under study included 77 experimental and 122 control primiparae, 68 experimental and 71 control secundiparae, and 244 experimental and 139 control multiparae (i.e. sows with three or more parturitions). The experimental sows were treated with 1000 IU of serum gonadotropin ad usum vet.-Bioveta-(PMSG) the first day after the weaning of piglets and with 300 IU of chorion gonadotropin (HCG) in the Praedyn inj. Spofa preparation together with 1 ml of Dirigestran inj. Spofa (40 micrograms LHRH) 72 hours later. Control sows were not treated with hormones. The treated primiparae and secundiparae respectively, had a significantly higher percentage of oestrus onset within 10 days after weaning and lower occurrence of anoestria over 10 days after weaning by 31.25 per cent (P less than 0.001), and 21.36 per cent (P less than 0.02) respectively as compared with untreated controls. In the set of secundiparae, the studied hormonal treatment speeded oestrus onset by a significant (P less than 0.01) shortening of the interval from weaning to the first insemination by 0.79 day and by a more frequent onset of oestrus within only 5 days after weaning of piglets. The values of the other criteria of reproduction studies, i.e. percentage of pregnancies after the first insemination, total number of born piglets and number of liveborn piglets converted per one litter in treated primiparae and secundiparae did not differ significantly (P greater than 0.05) from the control.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Effects of the Periodical Use of In-feed Chlortetracycline on the Reproductive Performance of Gilts and Sows of a Commercial Pig Farm with a History of Clinical and Subclinical Viral and Bacterial Infections

The objective of this study was to assess the effects of in‐feed chlortetracycline (CTC) as a measure of preventing or minimizing infectious problems of reproductive failure in gilts and sows. In a farm of 400 Large White × Landrace gilts and sows with a clinical history of porcine respiratory and reproductive syndrome (PRRS) virus, the animals were treated with CTC. Treatment consisted of 10 g CTC sow/day for 15 days every 3 months. It improved the health status of sows by decreasing post‐farrowing clinical mastitis and vaginal discharges, abortions, return‐to‐oestrus and irregular return‐to‐oestrus rates. These beneficial effects had a positive impact on the performance of the litter. More piglets were born live and weaned. These positive effects improved with repeated use of CTC. The serological evidence of PRRS virus, Leptospira spp. and Chlamydia spp. and the subsequent beneficial use of the antimicrobial agent indicate that reproductive failure, possibly resulting from the bacterial agents can be controlled with in‐feed use of broad spectrum antimicrobials.     

Reproductive performance in gilts through their first two parities

Fertility data were collected for 766 gilts from 12 breeding and commercial herds. The age at first breeding was 244.5 days and at first farrowing 363.2 days. The litter size was 9.91 piglets born (9.16 live). The farrowing rate at the first service was 87.8%. The total farrowing rate was 95.5% of the mated gilts and 88.4% of all the gilts. 9.8% were repeat breeders. 2.6% of the once mated gilts never returned to oestrus and still did not farrow. The culling rate was 11.6%. The major reason for culling was delayed puberty/anoestrus (7.7%). Of the 565 gilts having a first litter 85.3% were mated after weaning. The age at second farrowing was 541.7 days. The litter size was 10.9 piglets born (10.3 live). The farrowing rate after first service was 83.0%. The total farrowing rate of the 482 sows was 92.9% and of the 565 weaned sows 79.3%. 12.2% were repeat breeders. 4.8% of the sows once mated never returned to oestrus and still did not farrow. The culling rate was 20.7%. Culling because of anoestrus was 4.4%. The month of birth significantly influenced the number of gilts culled because of anoestrus, the age at first breeding and at first and second farrowing. The season also influenced the interval from weaning to service, the percentage of sows served within 7 days of weaning and culled because of anoestrus. No correlation between a high ultrasonic index and lowered fertility was found. The age at first breeding was 1.12 days younger per unit higher ultra-sonic index.     

Field experiences with early pregnancy diagnosis by progesterone-based ELISA in sows

In four Kenyan pig breeding units the pregnancy diagnosis of sows has been carried out in two groups: Group 1 (n = 1911): the sows were transrectaly pregnancy tested between Days 17-22 post-mating by ultrasound. Sows testing non-pregnant immediately received one dose of 400 IU pregnant mare serum gonadotropin (PMSG) (equine chorion gonadotropin, eCG) and 200 IU human chorion gonadotropin (hCG). On showing signs of oestrous, the animals were subsequently artificially inseminated (AI). Group 2 (n = 1923): sows were pregnancy tested by serum progesterone (P4)-based enzyme-linked immunosorbent assay (ELISA) on Day 17 post-breeding. P4 concentrations were categorized as positive (> 5 ng/ml) or negative (< 5 ng/ml). Sows testing nonpregnant immediately received one dose of 400 IU PMSG and 200 IU hCG by injection, and were subsequently artificially inseminated. The following parameters were evaluated: sows diagnosed non-pregnant, days from first post-weaning insemination until the sows were inseminated at their first return to oestrus; farrowing rate and total piglets born and number of live-born piglets in litters. The percentage of sows diagnosed non-pregnant in the two groups, as well as the totals of born piglets and of live-born piglets in litters did not differ significantly between the two groups. The number of days from the first post-weaning mating until the sows were artificially inseminated at their first return to oestrus and the administration of eCG and hCG was shorter (P < 0.01) and farrowing rate was higher (P< 0.01) in the ELISA-tested sows.     

The Effect of Post-ovulatory Insemination on the Subsequent Embryonic Loss, Oestrous Cycle Length and Vaginal Discharge in Sows

The aim of present study was to study the effect of post-ovulatory insemination on the subsequent embryonic loss, oestrous cycle length and vaginal discharge in sows. Ten Large White multiparous sows were divided into two groups. Group A sows were inseminated once at 15 h after ovulation. Thereafter, they were ovariohysterectomized on day 11 (n = 5, first day of standing oestrus = day 1) and flushed for recovery of embryos. Group B sows were also inseminated once at 15 h after ovulation. They were further observed for return to oestrus and vaginal discharge (n = 5) after insemination. The endometrium tissues were biopsied from sows with vaginal discharge, embedded with paraffin, stained with haematoxylin and eosin and examined under light microscope. Only two embryos were observed in one of four sows from group A. All embryos had a spherical shape but differed in size (range 1-2 mm). In group B, only one sow had a regular return to oestrus (i.e. on day 23) and another sow had an irregular return to oestrus (i.e. on day 27). The other two sows in this group had shown vaginal discharge on days 20 and 38 after standing oestrus. For the number of leucocytes in the endometrium of sows with vaginal discharge, a large number of lymphocytes and plasma cells were observed in the connective tissue of the subepithelial layer. In conclusion, post-ovulatory insemination resulted in early embryonic loss, a subsequent prolonged oestrus interval and also vaginal discharge (i.e. endometritis) in sows.     

The effect of farrowing duration and parity on preovulatory follicular size and oxytocin release of sows at subsequent oestrus

This study examined the extent to which prolonged farrowing and parity are associated with plasma oxytocin concentrations and follicular development of oestrous sows during subsequent insemination. A total of 30 sows were allocated to two groups based on farrowing duration: (i) SHORT (n  = 14): 159 ± 29 min, (ii) LONG (n  = 16): 533 ± 190 min. The sows were also divided into two parity classes: (i) YOUNG (n  = 14): parity 2.5 ± 0.8, (ii) OLD (n  = 16): parity 6.4 ± 2.3. After weaning, the ovaries were examined daily with transrectal ultrasound. On the second day of oestrus, blood samples were collected for oxytocin (OT ) assay at ?15, ?10, ?5, 0, +1, +2, +3, +4, +6, +8, +10, +15, +20, +25, +30, +40, +50 and +60 min with a boar contact between 0 and +10 min. Boar presence stimulated an increase in OT concentrations (p  <  .05). During boar presence, OT in the LONG group was higher than in the SHORT group (p  <  .01). The sows in the OLD group had a longer farrowing duration than in the YOUNG group (p  <  .05). OT levels and diameters of follicles were more relevant for parity than was the duration of farrowing. We therefore conclude that the OT levels and follicular development of oestrous sows are associated due to parity but difficult to be predicted from the duration of previous farrowing.     

The Effect of Intravaginal Applied GnRH-agonist on the Time of Ovulation and Subsequent Reproductive Performance of Weaned Multiparous Sows

In order to prove the effect of 'fixed time insemination' and insemination at standing oestrus after post-weaning application of GnRH, in a Croatian large breeding unit, 502 sows were assigned to three groups and were artificially inseminated (AI) at their first post-weaning oestrus as many times as they stand, in 24-h intervals. The groups were treated as follows: group 1 (control, n = 160) were AI during their standing reflex; group 2 ['GnRH-fixed time insemination' (GnRH-FT-AI), n = 175] were AI, independent of detection of oestrus and following administration of GnRH-agonist at 96 h post-weaning; group 3 [GnRH insemination at standing oestrus (GnRH-OE-AI), n = 167] the animals were GnRH-agonist treated as group 2 and were AI at their standing reflex. Pre-trial daily average lactational feed intake, average daily feed intake from weaning to oestrus, oestrus within 6 days post-weaning (%), ovulation within 6 days post-weaning (%), weaning-to-oestrus interval (h), duration of oestrus (h), follicle size (mm), interval from oestrus to ovulation (h), subsequent day 24 pregnancy rate (%), farrowing rate (%) and total pigs born were evaluated. Pre-trial average daily lactational voluntary feed intake was 7.1 +/- 0.08 kg in group 1, 7.0 +/- 0.07 kg in group 2 and 7.1 +/- 0.17 kg in group 3 (p > 0.05). Average voluntary daily feed intake from weaning to oestrus was 5.1 +/- 0.3 kg in group 1, 5.2 +/- 0.5 kg in group 2 and 5.2 +/- 0.19 kg in group 3 (p > 0.05). Oestrus was detected within 6 days post-weaning in 134 (83.8%) in control, 164 (93.7%) in GnRH-FT-AI and 155 (92.8%) animals in GnRH-OE-AI groups (p = 0.05). Follicle size did not differ (p > 0.05) among the groups. In control 82.8%, in GnRH-FT-AI 91.5% and in GnRH-OE-AI 91.0% of the sows ovulated within 6 days post-weaning (p = 0.04), and had 80.6, 90.9 and 89.7% 24-day pregnancy rates (p = 0.16), respectively. In GnRH-FT-AI group 90.2%, in GnRH-OE-AI sows 89.7%, in control animals 79.9% farrowing rates were recorded (p = 0.17). Weaning to oestrus interval was 113.1 h in control, 114.1 h in GnRH-FT-AI and 112.6 h GnRH-OE-AI (p > 0.05). Duration of oestrus was significantly shorter in GnRH-FT-AI (44.9 h) and GnRH-OE-AI (48.1 h) animals, compared with the control (62.9 h) sows (p = 0.001). Similarly, the interval from oestrus to ovulation revealed significant (p = 0.004) differences between the groups (control 44.1 h, GnRH-OE-AI 34.1 h and GnRH-FT-AI 32.9 h). GnRH-FT-AI (12.5) and GnRH-OE-AI (12.6) sows had significantly higher (p = 0.01) number of total pigs born (n = 10.4) compared with control sows. GnRH-agonist-gel treatment to the sow shortens duration of oestrus, the interval from oestrus to ovulation, and may eliminate the need for oestrus detection in the hands of skilled personnel.