Elevating glucose and insulin secretion by carbohydrate formulation diets in late lactation to improve post-weaning fertility in primiparous sows.

Primiparous (P1) sows commonly lose excessive body reserves to meet energy requirements for maintenance and milk production during lactation, and consequently, post-weaning reproductive performance may be compromised. The present studies determined whether ad libitum feeding a glucogenic carbohydrate diet (CHO) during late lactation could stimulate insulin and glucose secretion (experiment 1) and improve subsequent litter size (experiment 2). For experiment 1, 15 P1 sows, and for experiment 2, 99 P1 sows (198.5 ± 2.7 kg) were allocated randomly according to suckled litter size (≥10 piglets), either to a CHO diet (14.3 MJ DE/kg, 19.8% crude protein) or a standard lactation diet (control; 14.2 DE MJ/kg, 19.5% crude protein) at 8 days before weaning. The CHO diet aimed to provide glucogenic content (extruded wheat, dextrose and sugar) as energy sources instead of fat sources without changing total dietary energy. Pre-prandial plasma glucose and insulin concentrations were not influenced by treatments. However, post-prandial plasma glucose and insulin concentrations and their peaks were both higher (p < .05) compared to the control treatment. Body weight loss during lactation was relatively low at 3%-4% for both treatments and did not differ between control and CHO treatments (-7.6 ± 1.6 vs -5.4 ± 1.2 kg; p > .05). Second litter size was not influenced by diet (p > .05), but the weaning-to-mating interval was shorter in CHO sows (p < .05). This study demonstrates that providing an enriched CHO diet in late lactation did influence post-weaning follicle growth but did not improve subsequent litter size. This may be due to the primiparous sows in this study not experiencing severe negative energy balance and there was no second litter syndrome in this farm which limited the ability of diet to improve sow fertility.

Advances in Breeding Management and Use of Ovulation Induction for Fixed-time AI.

The objective of the breeding herd is the predictable and consistent production of high quality pigs. To achieve this objective, an appropriate number of females need to be mated in each breeding week and they should maintain their pregnancy and deliver large litters. Many factors can impact achievement of optimal sow productivity, particularly breeding management. Most matings will involve artificial insemination (AI), and successful AI requires deposition into the cervix (or beyond) of sufficient viable high quality sperm at an appropriate time relative to ovulation. This is facilitated by improved knowledge of the sow's ovarian function prior to and during her oestrous period. Realization of the importance of establishing an adequate sperm reservoir in the oviduct at an appropriate time relative to ovulation has led to advances in the management of AI. The future of AI will likely involve insemination of single doses of high genetic merit semen, potentially having a reduced sperm concentration which is made possible by knowledge of the effect of site of sperm deposition on sow fertility. In particular, knowledge of when a sow is likely to ovulate during a natural or induced oestrous period will prove invaluable in the maintenance of herd productivity. This review will examine options for breeding management, including the control of oestrus and ovulation, on sow herd reproductive performance.

Influence of gonadotrophin-induced first oestrus on gilt fertility.

The aim of this study was to determine the association between the oestrous response of pre-pubertal gilts to gonadotrophin injection or boar exposure and their subsequent farrowing rate and litter size. At 154 days of age, randomly selected pre-pubertal gilts received an intramuscular injection of 400 IU equine chorionic gonadotrophin plus 200 IU human chorionic gonadotrophin (PG600(®) ; Merck Animal Health; n = 181). From the remaining pool of animals not treated with hormones, the first gilts showing signs of oestrus were selected to act as controls (n = 201). Boar exposure began at 155 days of age for both groups, and gilts were bred at a weight of approximately 130 kg. Comparisons were made between PG600(®) -treated gilts exhibiting oestrus or not within 7 days post-injection (early and late responders, respectively) and control gilts exhibiting oestrus or not within 30 days after beginning of boar exposure (select and non-select control gilts, respectively). By 162 days, oestrus was detected in 67.5% of PG600(®) -treated gilts compared with 5.7% of control gilts (p < 0.0001). The proportion of animals observed in oestrus at least three times before breeding was greater for select control gilts compared with early and late responder PG600(®) -treated gilts (p ≤ 0.001). There were no significant differences in farrowing rate and litter size between the four treatment groups. These data indicate that PG600(®) is an effective tool to induce an earlier oestrus in gilts, that subsequent farrowing rate and born alive litter size compare favourably to that of select gilts and that gilts failing to respond promptly to hormonal stimulation do not exhibit compromised fertility.

Influence of prepartum feed levels on colostrum production and farrowing performance in highly prolific sows in a tropical environment.

Currently, there is a lack of data on the effects of altering feed levels on sow performance and piglet characteristics during the transition period in tropical environments. The present study determined the effect of sow feed levels during the transition period on colostrum yield, colostrum immunoglobulin (Ig) G, colostrum intake of piglets, farrowing duration, proportion of stillborn piglets per litter (SB) and the incidence of farrowing assistance in highly prolific sows. A total of 114 Landrace × Yorkshire crossbred sows and their offspring (n = 2 072) were included in the experiment. Sows were assigned to different feed supply levels from entry to farrowing at 110 days of gestation until farrowing based on their parity number. Three feed-level groups were the control group who received 3.0 kg/day of lactation feed (n = 40), treatment 1 group who received 3.6 kg/day of gestation feed (n = 39) and treatment 2 group who received 4.0 kg/day of lactation feed (n = 35). Colostrum samples (5 ml) were obtained from the sows within 3 h after the onset of farrowing for IgG assay. Piglets were weighed immediately after birth and then again 17-24 h later to estimate their colostrum intake. Colostrum yield was determined by aggregating the colostrum intake of piglets within the litter. The total number of piglets born, SB and farrowing duration were 18.2 ± 3.8, 7.5% and 259.1 ± 138.1 min, respectively. Among these sows, 28.9% experienced a farrowing duration exceeding 300 min and 50.9% required assistance during farrowing. Interestingly, piglets in the treatment 2 group demonstrated a greater colostrum intake (403.1 ± 14.9 g) compared to the control group (360.6 ± 15.1 g, P = 0.046) and the treatment 1 group (361.0 ± 12.9 g, P = 0.033). On average, colostrum yield of sows in the treatment 2 group tended to be higher than in the control group (+0.5 kg, P = 0.081), but did not differ from the treatment 1 group (+0.3 kg, P = 0.191). No significant differences in farrowing duration, SB, farrowing assistance, or colostrum IgG concentration were found across various feed-level groups (P > 0.05). In conclusion, the study showed that raising lactation feed by 1.0 kg/day prefarrowing increased piglet colostrum intake and tended to boost sow colostrum production, without significantly affecting farrowing duration, stillbirth rates, or need for assistance.

Review: Can early-life establishment of the piglet intestinal microbiota influence production outcomes?

The gastrointestinal tract microbiota is involved in the development and function of many body processes. Studies demonstrate that early-life microbial colonisation is the most important time for shaping intestinal and immune development, with perturbations to the microbiota during this time having long-lasting negative implications for the host. Piglets face many early-life events that shape the acquisition and development of their intestinal microbiota. The pork industry has a unique advantage in that the producer has a degree of control over what piglets are exposed to, providing conditions that allow for optimum piglet growth and development. An influx of publications within this area has occurred in recent times and with this, interest surrounding its application in pork production has increased. However, it can be difficult to distinguish which research is of most relevance to industry in terms of delivering repeatable and reliable production outcomes. In this review, we describe the literature surrounding research within pigs, predominantly during the preweaning period that has either provided solutions to industry problems or is generating information targeted at addressing relevant industry issues, with the focus being on studies demonstrating causation where possible. This review will provide a basis for the development of new studies targeted at understanding how to better support initial intestinal microbiota colonisation in order to improve piglet health and survival.

Transcript abundance of amino acid transporters, ß-casein, and α-lactalbumin in mammary tissue of periparturient, lactating, and postweaned sows.

The objective of these experiments was to test the hypothesis that transcript abundance of cationic AA transporter- and milk protein-encoding genes increase in the porcine mammary gland in response to higher lactation demand. Genes of interest included those encoding for the milk proteins α-lactalbumin (α-LA) and ß-casein (ß-CN; LALBA and CSN2, respectively), and AA transporter b(0,+)AT, y(+)LAT1, y(+)LAT2, ATB(0,+), CAT-1, and CAT-2b (SLC7A9, SLC7A7, SLC7A6, SLC6A14, SLC7A1, and SLC7A2, respectively). Mammary tissue was biopsied from 4 sows on d 110 of gestation (prepartum), on d 2 (early postpartum), on d 5 (early), and d 17 (peak) of lactation, and on d 5 after weaning (postweaning), and mRNA of target genes quantified by reverse transcription quantitative PCR. Compared with prepartum, CAT-1, ATB(0,+), y(+)LAT2, ß-CN, and α-LA mRNA abundance was higher at early lactation, whereas compared with early lactation, only CAT-1 and α-LA mRNA abundance was higher at peak lactation. The CAT-2b, y(+)LAT1, and b(0,+)AT mRNA abundance did not differ when comparing either prepartum or peak lactation to early lactation. Compared with peak lactation, postweaning mRNA abundance of CAT-1, ATB(0,+), α-LA, and ß-CN decreased, y(+)LAT2, CAT-2b, and b(0,+)AT remained unchanged, and y(+)LAT1 increased. The mRNA abundance of y(+)LAT2 increased from early postpartum to early lactation, and remained unchanged for CAT-1, ATB(0,+), α-LA, and ß-CN. From prepartum to peak lactation, the mRNA abundance of CAT-1, y(+)LAT2, and ATB(0,+) was positively correlated with that of ß-CN and α-LA. In conclusion, the expression of genes encoding for y(+)LAT1, CAT-2b, and b(0,+)AT remained unchanged in porcine mammary glands over prepartum to peak lactation period, whereas expression of genes encoding for CAT-1, ATB(0,+), and y(+)LAT2 was upregulated and positively correlated to expression of genes encoding for the mammary synthesized milk proteins ß-CN and α-LA.

Effect of hCG on early luteal serum progesterone concentrations in PG600-treated gilts.

Gilt oestrus and ovulation responses to injection of a combination of equine chorionic gonadotrophin (eCG) and human chorionic gonadotrophin (hCG) (PG600) can be unpredictable, possibly reflecting inadequate circulating LH activity. The objective of this study was to determine the effect of PG600 followed by supplemental hCG on gilt ovarian responses. In experiment 1, 212 Hypor gilts (160 day of age) housed on two farms in Spain received intramuscular (i.m.) injections of PG600 (n = 47), or PG600 with an additional 200 IU hCG injected either concurrently (hCG-0; n = 39), or at 24 h (hCG-24; n = 41) or 48 h (hCG-48; n = 45) after PG600. A further 40 gilts served as non-injected controls. Ovulation responses were determined on the basis of initial blood progesterone concentrations being <1 ng/ml and achieving >5 ng / ml 10 d after the PG600 injection. The incidence of ovulating gilts having progesterone concentrations >30 ng/ml were recorded. During the study period, 10% of control gilts ovulated whereas 85-100% of hormone-treated gilts ovulated. There were no significant differences among hormone groups for proportions of gilts ovulating. The proportions of gilts having circulating progesterone concentrations >30 ng/ml were increased (p < or = 0.02) in all hCG treated groups compared with the PG600 group. In experiment 2, a total of 76 Hypor gilts at either 150 or 200 days of age were injected with PG600 (n = 18), 400 IU eCG followed by 200 IU hCG 24 h later (n = 20), PG600 followed by 100 IU hCG 24 h later (n = 17), or 400 IU eCG followed by 300 IU hCG 24 h later (n = 21). Blood samples were obtained 10 days later for progesterone assay. There were no effects of treatment or age on incidence of ovulation, but fewer 150-day-old gilts treated with PG600 or 400 IU eCG followed by 200 IU hCG had progesterone concentrations >30 ng / ml. We conclude that hCG treatment subsequent to PG600 treatment will generate a higher circulating progesterone concentration, although the effect is not evident in older, presumably peripubertal, gilts. The mechanism involved and implications for fertility remain to be determined.

Supplementation of diets for lactating sows with zinc amino acid complex and gastric nutriment-intubation of suckling pigs with zinc methionine on mineral status, intestinal morphology and bacterial translocation in lipopolysaccharide-challenged weaned pigs.

Sixty-four pigs from 16 sows were used to evaluate addition of zinc amino acid complex (ZnAA) to lactating sows and gastric nutriment-intubation of zinc methionine (ZnMet) to suckling pigs on mineral status, intestinal morphology and bacterial translocation after weaning. Sows were fed a barley-based diet supplying 120 ppm zinc (Zn; control) or the control diet supplemented with 240 ppm Zn from ZnAA. At birth, day-10 and day-21 (weaning) of age, pigs from each litter were nutriment-intubated with 5 ml of an electrolyte solution without or with 40 mg Zn from ZnMet. At weaning, 24 h prior to the collection of small and large intestinal lymph nodes and sections of the duodenum, jejunum and ileum, the pigs received an intramuscular injection of saline without or with 150 microg/kg body weight of Escherichia coli O26:B6 lipopolysaccharide (LPS). With the exception of a tendency (p = 0.09) for lower serum concentration of copper in pigs at weaning from ZnAA-supplemented sows, there were no differences (p > 0.1) than for pigs from control-fed sows for mineral status or intestinal morphology. Nutriment-intubation of ZnMet increased serum (p = 0.001) and liver (p = 0.003) Zn concentrations, number of goblet cells per 250 microm length of jejunal villous epithelium (p = 0.001) and tended (p = 0.06) to enhance jejunum mucosa thickness. Interactive effects (p < 0.05) for higher jejunal villi height and villi:crypt ratio and increased ileal goblet cell counts were apparent for pigs from ZnAA-supplemented sows that also received nutriment-intubation of ZnMet. Challenge with LPS increased (p = 0.05) ileal villous width. Nutriment-intubation of ZnMet decreased (p = 0.05) anaerobic bacteria colony forming unit counts in the large intestinal mesenteric lymph nodes. In conclusion, nutriment-intubation of ZnMet increased serum and liver tissue concentrations of Zn and resulted in limited improvement to intestinal morphology of weaned pigs.

Supplementation of diets for gestating sows with zinc amino acid complex and gastric intubation of suckling pigs with zinc-methionine on mineral status, intestinal morphology and bacterial translocation in lipopolysaccharide-challenged early-weaned pigs.

Eighty male pigs from 20 litters were used to evaluate dietary addition of 250mg/kg of Zn from zinc amino acid complex (ZnAA) to sows during the last trimester of gestation and gastric intubation of 40mg Zn from soluble zinc methionine (ZnMet) to suckling pigs at birth and on day 7 and 14 (weaning) on small intestinal morphology, Zn status and bacterial translocation in early-weaned pigs. At weaning, pigs were challenged with an intramuscular injection of saline without or with 120microg/kg BW of lipopolysaccharide (LPS; from Escherichia coli O26:B6) and were euthanized 24h later prior to collection of intestinal lymph nodes and small intestinal sections. Zinc concentration in serum 7 days after birth and at weaning were higher in pigs from ZnAA-supplemented sows and those receiving gastric intubation with ZnMet (P=0.05 and P<0.0001, respectively). Post-weaning liver tissue concentrations for Zn (P<0.0001) and Fe (P=0.04) were higher and for Cu lower (P<0.0001) in pigs intubated with ZnMet. Pigs from ZnAA-supplemented compared with control-fed sows tended (P<0.1) to have increased villi height and villus:crypt ratio in the jejunum and higher (P=0.1) goblet cell counts in the ileum. Goblet cell counts of ZnMet-intubated (P=0.03) and LPS-challenged pigs (P=0.05) were also higher in the jejunum. Supplementation of ZnAA to gestating sows increased (P=0.04) E. coli colony forming unit counts in the small intestinal mesenteric lymph nodes of early-weaned pigs. In conclusion, dietary addition of ZnAA to gestating sows and gastric intubation of ZnMet improved Zn status of suckling pigs.

Effect of hCG treatment on the oestrous and ovulation responses to FSH in prepubertal gilts.

To ensure sufficient numbers of pregnant females, particularly at hotter times of the year, hormonal induction of gilt oestrus may be necessary. However, the gilt oestrus and ovulation responses to gonadotrophin treatment have often proven unpredictable. The objective of this study was to examine possible reasons for this unpredictability. Prepubertal gilts (approximately 150 days of age, n = 63) were assigned to one of three treatments: injection of 300 IU hCG (n = 15); pre-treatment with 100 mg FSH in polyvinylpyrrolidinone administered as 2 x 50 mg injections 24 h apart, followed by 600 IU eCG at 24 h after the second FSH injection (n = 23); or FSH pre-treatment as above followed by 300 IU hCG at 24 h after the second FSH injection (n = 25). To facilitate oestrus detection, gilts were exposed to a mature boar for 15 min daily for 7 days. Blood samples were obtained on the day of eCG or hCG injection and again 10 days later and gilt ovulation responses determined based on elevated progesterone concentrations. The oestrus responses by 7 days were 6.7%, 17.5% and 64.0% for gilts treated with hCG, FSH + eCG and FSH + hCG, respectively (p < 0.001). The oestrous gilt receiving hCG alone and one oestrous FSH + hCG gilt did not ovulate, all other oestrous gilts ovulated. A further two anoestrous FSH + eCG-treated gilts ovulated. These data suggest that FSH pre-treatment facilitated the development of ovarian follicles to the point where they became responsive to hCG, but had little effect on the response to eCG.

Effect of eCG or eCG Plus hCG on oestrus expression and ovulation in prepubertal gilts.

To meet weekly breeding targets, it is occasionally necessary to inject exogenous gonadotrophins to induce oestrus in prepubertal gilts. However, the gilt oestrus response to equine chorionic gonadotrophin (eCG) either alone or in combination with human chorionic gonadotrophin (hCG) can be unpredictable. The objective of the present study was to examine possible reasons for this unpredictability. Prepubertal gilts (90 kg and 153 days of age, n = 109) received an injection of either 600 IU eCG or a combination of 400 IU eCG and 200 IU hCG (PG600), or were non-injected controls, and were then exposed to a mature boar for 15 min daily for 7 days for oestrus detection. At the time of injection, real-time ultrasound revealed that the gilt ovaries had primarily 1-2 mm follicles. Blood samples were obtained at time of hormone injection (day 0) and at days 3, 7 and 10 for assay of serum progesterone concentrations. The oestrus responses by 7 days were 15.5%, 73.3% and 0%, for eCG, PG600, and control gilts, respectively (p < 0.001). The oestrus response improved (p < 0.05) with increasing body weight. Based on circulating progesterone levels, all oestrous gilts ovulated except for four of the PG600 gilts. Failure to express oestrus in PG600 gilts was not associated with a premature rise in progesterone.

Effects of oxytocin and carbetocin on farrowing performance.

During sow parturition, there is need for an alternative uterotonic to oxytocin with less potency so piglets are not at risk of hypoxia and stillbirth. In this study, there was examination of carbetocin, a longer lasting analogue of oxytocin, and whether the lesser contractile force and duration resulting as a consequence of this treatment would improve piglet survivability. Following delivery of the first piglet, sows were serially assigned by parity to receive injections of 10 IU oxytocin (n = 35), 0.07 mg carbetocin (n = 36), or serve as a non-injected control (n = 30). The incidence of dystocia and stillbirths was recorded. To estimate liveborn piglet viability, umbilical cord blood samples were obtained from pigs 1, 2, 3 and 8, 9, 10, and lactate content was quantified to assess hypoxia during delivery. A blood sample collected at 24 h was assayed for total protein in plasma (%) as an indicator of colostrum intake. Treatment with oxytocin and carbetocin reduced farrowing duration (P = 0.023) and sows treated with carbetocin had piglets with the least umbilical cord blood lactate (P = 0.008) and plasma protein (P = 0.005) concentrations. These data indicate carbetocin has the efficacy to accelerate piglet delivery and reduce piglet hypoxia, although the reason for reduced plasma protein with this treatment remains unexplained.

Practical application of seminal plasma.

Natural mating deposits a large number of sperm in a high volume of seminal plasma. Semen processed for AI has the seminal plasma greatly diluted, and processing of boar sperm for cryopreservation removes all seminal plasma. Boar sperm were evaluated for the impact of seminal plasma on the functional status of boar sperm. Seminal plasma prevented or reversed capacitation in frozen-thawed boar sperm. However, supplementing frozen-thawed semen doses with 10% seminal plasma did not significantly affect the number of sperm found in the utero-tubal sperm reservoir, nor did it affect farrowing rates.

Role of luteinizing hormone in primiparous sow responses to split weaning.

In 45 primiparous sows, we examined endocrine, ovarian and reproductive responses to split-weaning or five injections per day of 800 ng GnRH from 18 to 21 days of lactation. There was no effect of treatment on absolute or changes in sow weight or backfat depth during lactation. Average piglet growth rates were similar among treatments except that piglets suckling split-weaned sows grew faster (p < 0.05) during days 18-21. On day 18, mean plasma LH concentrations and LH pulse frequency remained relatively stable in conventionally weaned sows but increased (p < 0.01) in response to split-weaning and GnRH. Prior to weaning on day 21, mean plasma LH concentrations remained elevated in GnRH-treated sows but had returned to control levels in split weaned sows. There was no treatment effect on preweaning LH pulse frequency noted on day 21. Weaning was associated with an increase in plasma LH concentrations in all the treatment groups. Mean plasma IGF-I remained relatively constant in conventionally weaned and GnRH sows, decreased in response to split weaning on day 18 (p < 0.02), but were elevated (p < 0.03) in split wean sows on day 21. On the day after weaning, split wean sows had more (p < 0.04) ovarian follicles >or=3 mm than conventionally weaned sows, with GnRH sows being intermediate. The wean-to-oestrus interval was reduced in split-wean sows compared with those conventionally weaned (p < 0.01), with GnRH sows being intermediate. There was no effect of treatment on ovulation rates, numbers of embryos, or embryonic survival rates. These data indicate that split-weaning of litters results in a more rapid return to oestrus after weaning and that this effect is associated with a transient acute increase in circulating gonadotrophins and earlier resumption of ovarian follicular development.

Effect of prior insemination of dead sperm and gestation housing management on gilt fertility.

Danbred gilts at about 120 kg were group housed for estrous detection. At detection of estrus, gilts either remained in pens (P) or were re-housed into individual gestation stalls (S) and were inseminated (DS), or not (SC), with a dose of frozen/thawed dead semen. Groups were P-DS (n = 81), P-SC (n = 70), S-DS (n = 98) and S-SC (n = 90). All gilts were inseminated with semen containing viable sperm at the second detected estrus and 24 h later. Pregnant gilts that were stall housed were moved to pens 35 d after insemination. There were no effects of insemination or housing management on farrowing rates or litter sizes.

Muscular function and functional mobility of faller and non-faller elderly women with osteoarthritis of the knee.

Falls are a major concern in the elderly population with chronic joint disease. To compare muscular function and functional mobility among older women with knee osteoarthritis with and without a history of falls, 15 elderly women with a history of falls (74.20 +/- 4.46 years) and 15 without a history of falls (71.73 +/- 4.73 years) were studied. Muscular function, at the angular speed of 60, 120, and 180 masculine/s, was evaluated using the Biodex Isokinetic Dynamometer. The sit-to-stand task was performed using the Balance Master System and the Timed Up and Go test was used to determine functional mobility. After collection of these data, the history of falls was investigated. A statistically significant difference was detected in the time taken to transfer the center of gravity during the sit-to-stand test (means +/- SD; non-fallers: 0.35 +/- 0.16 s; fallers: 0.55 +/- 0.32 s; P = 0.049, Student t-test) and in the Timed Up and Go test (medians; non-fallers: 10.08 s; fallers: 11.59 s; P = 0.038, Mann-Whitney U-test). The results indicated that elderly osteoarthritic women with a history of falls presented altered functional mobility and needed more time to transfer the center of gravity in the sit-to-stand test. It is important to implement strategies to guarantee a better functional performance of elderly patients to reduce fall risks.

Effect of sperm numbers and time of insemination relative to ovulation on sow fertility.

We examined the effect of inseminating mixed parity sows (n=231) once with fewer sperm at different times relative to ovulation. Lactation length was 19 days and sows received an IM injection of 600 IU equine chorionic gonadotrophin (eCG) 12 h before weaning. At 80 h after eCG injection, sows received an IM injection of 5 mg porcine luteinizing hormone (pLH). Predicted time of ovulation (PTO) was 38 h after pLH injection. Sows were assigned by parity to receive a single transcervical artificial insemination (AI) at either 6 or 24 h before PTO with semen doses containing either 2.5 or 1.25x10(9) sperm. A positive control group of sows (n=49) was subject to conventional AI 24 and 6 h before PTO. Detection of estrus was performed in the presence of a boar and only sows exhibiting estrous behavior at the assigned time of AI were included in the study. Farrowing rate for sows receiving 2.5x10(9) sperm at 6 h before PTO was greater than that for sows receiving 1.25x10(9) sperm at 24 h before PTO (85% versus 61%, P<0.05). All other groups were intermediate. There was no effect of time of AI or sperm numbers on subsequent litter size. These data indicate that single insemination of fewer sperm may compromise sow fertility, even when performed transcervically, if not appropriately timed relative to ovulation.

Response to gonadotrophins differs for gilts from female- and male-biased litters.

In several species, females masculinised by abnormal androgen exposure in utero have poor reproductive performance and gilts born into litters with a male bias are likely exposed to greater androgen concentrations prenatally than gilts born into female-biased litters. At 24h of age, piglet plasma testosterone concentrations in gilts from male-biased litters (>60% male; n=22) or female-biased litters (>60% female; n=27) were not different. At 18 wks of age, all gilts received an injection of 400IU equine chorionic gonadotrophin plus 200IU human chorionic gonadotrophin to stimulate oestrus. Two weeks after the injection gilts were slaughtered and ovaries collected for determination of numbers of corpora lutea (CL). Compared to gilts from female-biased litters, gilts from male-biased litters were more likely to ovulate (86.0% vs 59.5%, P=0.047) and had more CL (13.1±1.5 vs 7.2±1.7, P=0.015). The present data indicate an effect of birth litter sex-bias on pre-pubertal physiological development, possibly involving organisational effects at the ovarian cellular level impacting on future ovarian function. Potential impacts on subsequent fertility remain to be determined.

Lactational oestrus and reproductive performance following a delayed limited nursing schedule in primiparous sows.

With conventional lactation management, sows only conceive after weaning. However, intermittent suckling (IS) enables follicle growth and ovulation during lactation by reducing the suckling-induced inhibition of gonadotrophins. The current study evaluated IS regimes initiated at Day 21 or Day 28 post farrowing compared to conventional weaning on Day 28, in primiparous sows. Sows (Large White and Large White x Landrace) were randomly allocated to Control (C28; n = 44), IS21 (n = 29) and IS28 (n = 34) treatments at Day 20. Sows in IS21 and IS28 were subjected to intermittent suckling from Day 21 or Day 28 post farrowing. During IS, sows were separated from their piglets for 8 h daily, then weaned 7 d later at Day 28 and Day 35 respectively, whereas piglets in the C28 treatment had continuous access to sows until weaning at Day 28. Percentage of IS sows that showed oestrus during lactation was 59% (16/27) in IS21 and 72% (21/29) in IS28 (P > 0.05). Cumulatively over the lactation and 7 d post-weaning period, 93% of IS21, 85% of IS28 and 93% (31/33) of C28 sows showed oestrus (P > 0.05). Pregnancy rate at Day 30 post mating, for sows that were mated during lactation was 93% (15/16) in IS21 and 95% (20/21) in IS28, whereas C28 sows had a 96% (30/31) pregnancy rate (P > 0.05). No difference was found in the time of oestrus relative to weaning (C28) or onset of IS (IS21 and IS28) (P > 0.05). The IS sows that did not ovulate before weaning all showed oestrus within 7 days from weaning, and the weaning to oestrus interval was similar to control sows (P > 0.05). However, for all IS sows (across IS treatments) that showed lactational ovulation, LH secretion pattern at onset of IS was different (P < 0.05) from the sows that did not ovulate in lactation. Plasma progesterone concentration tended to be lower in the IS21 treatment (P < 0.10) compared to the C28 sows at 4 d after ovulation. The subsequent litter size was not affected by treatments although numerically lower for IS21 (P > 0.05). The present study showed that in modern primiparous sows, lactational oestrus can be induced and pregnancy can be maintained at a similar rate and producing comparable subsequent litter sizes to conventionally weaned sows when IS commenced at four weeks post farrowing. However, when IS commences at three weeks post farrowing, this may affect the percentage of sows showing oestrus in lactation and may potentially influence subsequent litter size.

Control of estrus and ovulation: Fertility to timed insemination of gilts and sows.

It is possible to control follicular development in gilts and sows with the use of hormones including the progestogen altrenogest, GnRH, eCG, hCG, and porcine luteinizing hormone (pLH). These hormones can be used to develop protocols for control of estrus with artificial insemination (AI) timed to estrus detection (timed artificial insemination; TAI) or to control estrus and ovulation with insemination at a fixed time without the requirement of estrus detection (fixed-timed artificial insemination; FTAI). In cyclic gilts, double TAI after protocols based on altrenogest and eCG plus hCG administration can achieve a 70% of farrowing rate. Valuable results can be obtained in weaned sows by the utilization of protocols based on eCG administration at weaning and then GnRH or pLH at estrus onset followed by single or double TAI. In cyclic gilts, single or double FTAI regardless of estrus expression can be applied after protocols based on altrenogest administration followed by eCG and then GnRH, hCG, or pLH some hours later; farrowing rates are similar to control animals inseminated at estrus detection. With sows, a protocol based on eCG administration at weaning and hCG, GnRH, or pLH some hours later followed by single or double FTAI can give fertility rates comparable to control animal inseminated at estrus. Most recently, injection or vaginal deposition of GnRH 96 hours after weaning followed by a single FTAI 24 to 30 hours later is resulting in reproductive performance not different to animals subject to multiple inseminations after natural estrus. It is possible to apply FTAI in lactating sows. The protocols are based on eCG during lactation followed by hCG and FTAI. These protocols will induce ovulation during lactation, but pregnancy rates are reduced. However, in the future, a better knowledge on the effect of hormone administration on follicular dynamics during lactation may allow the development of more effective protocols.