Follicle development in pigs: State of the art.

Understanding the factors and pathways involved with recruitment, atresia, and selection of follicles in the pig, may provide insight into approaches to limit fertility failures. Antral follicles depend upon FSH to the 2-3 mm stage, become codependent upon LH at 4-5 mm, and rely on LH when >5 mm. Within the follicle, gonadotropin binding, steroids, growth factors, and inhibin interact to determine the fate of the follicle. Continuous recruitment appears likely for follicles, and once >1 mm, they may have a limited period for survival, before selection or atresia. If true, then the number of healthy follicles that can respond to a hormone signal for selection, could vary by size and development stage. Which follicles are selected may depend upon their age, numbers of capillaries, granulosa and thecal cells, and FSH and LH receptors. This might also suggest that factors such as management, nutrition, and stress in prior weeks, could affect different cohorts of follicles to determine which of those from the ovarian population will be selected.

Effects of nursing a large litter and ovarian response to gonadotropins at weaning on subsequent fertility in first parity sows.

Post-weaning fertility failures occur more often in parity 1 (P1) sows due to high metabolic demands for lactation and their inability to meet energy requirements for maintenance, growth, and reproduction. We hypothesized that body condition loss occurs more frequently in P1 sows nursing a large litter, resulting in impairment of ovarian follicle development during lactation and post-weaning, which can negatively impact estrus and subsequent fertility. At 24 h post-farrowing, P1 sows (n = 123) were assigned to treatment (TRT) based on sow weight and the number of functional teats to receive a high number (HN, 15 to 16) or low number (LN, 12) of nursing piglets. At weaning, sows in each TRT were assigned to receive PG600 or None (Control). During lactation, sow body measures were obtained and ovarian follicles were assessed in mid-lactation and post-weaning. Lactation data were analyzed for the effects of TRT, and fertility data after weaning were assessed for TRT x PG600, but there were no interactions (P > 0.10). During lactation, 22.2 % of HN sows lost ≥ 4 piglets due to death or removal, and so these sows were excluded from further analysis. The HN sows were lighter (-6.2 kg), had less backfat (-1.0 mm), had lower body condition score (-0.4), and lost more nursing piglets (-1.2) than LN sows (P < 0.05). However, HN sows weaned more pigs (14.0) than LN sows (11.0). There was no effect of TRT on wean to estrus interval (4.2 d), but the interval was 0.5 days shorter for PG600 (P = 0.004) than control. There were no effects of TRT or PG600 on estrus within seven days after weaning (87.3 %), but PG600 induced smaller (P = 0.002) follicles at estrus (6.7 mm) than control (7.3 mm). In the subsequent parity, there were no effects of TRT or PG600 on farrowing rate (93.9%) and total born (13.2). Overall, HN sows lost more piglets and body condition but still weaned more pigs without any detrimental effects on subsequent reproductive performance.

The motivation for this study was to determine if assigning parity one (P1) sows to nurse a large number of piglets (15 to 16) would cause substantial body condition loss and have detrimental consequences for fertility after weaning. The results showed that when P1 sows nurse 15 to 16 piglets, they lose more body condition and more piglets than P1 sows nursing 12 piglets. However, there was no impact on the fertility of these sows. This study demonstrates that P1 sows can nurse a high number of piglets and still have a high potential to be fertile after weaning their piglets. Still, there is potential to improve management to avoid excessive weight loss in sows and piglet losses.

Effects of a high-protein, high-fiber diet rich in antioxidants and l-carnitine on body weight, body composition, metabolic status, and physical activity levels of cats after spay surgery.

Spay and neuter surgeries are useful in controlling pet populations, but increase obesity risk due to increased appetite, decreased metabolic rate, and decreased energy expenditure. Dietary management may help limit post-spay weight gain, but few research studies have been conducted in cats. Therefore, the objective of this study was to evaluate the effects of a high-protein, high-fiber diet (HPHF) compared to a moderate-protein, moderate-fiber diet (MPMF) in female cats following spay surgery. Twenty healthy female cats (9.5 ±â€…0.1 mo) were used. After a 4-wk baseline phase with cats fed MPMF to maintain body weight (BW), 16 cats were spayed and allotted to MPMF (n = 8) or HPHF (n = 8), with the remaining cats being sham-operated and fed MPMF (n = 4). Cats were fed to maintain BW for 12 wk and then allowed to eat up to twice that amount for another 12 wk. Daily food intake, twice weekly BW, and twice weekly body condition scores (BCS) were assessed. Back fat thickness (BF) using ultrasound, body composition using dual-energy X-ray absorptiometry (DEXA), feline body mass index (fBMI), body fat percentage estimates using zoometry measurements, serum metabolites, and voluntary physical activity levels were measured prior to spay (week 0) and every 6 wk post-spay. A treatment*time effect was observed for food intake (g/d), but not caloric intake (kcal ME/d). Caloric intake was affected by time and treatment, being reduced over the first 12 wk and reduced at higher amounts in HPHF and MPMF cats vs. sham cats. BW, BCS, and body fat percentage were affected over time. Treatment*time effects were observed for blood urea nitrogen, alkaline phosphatase, and fructosamine, whereas blood triglycerides, total cholesterol, creatinine, total protein, phosphorus, and bicarbonate were affected by time. Physical activity was reduced over time. Our results demonstrate that spay surgery affects food intake, BW, metabolism, and physical activity of cats. Dietary intervention in this study, however, led to minor changes.

Spay surgery helps control pet populations, but increases obesity due to increased appetite, decreased metabolic rate, and decreased energy expenditure. Our objective was to evaluate the effects of high-protein, high-fiber diet (HPHF), and moderate-protein, moderate-fiber diets (MPMF) in female cats following spay surgery. Of the 20 cats used, 16 were spayed and fed MPMF (n = 8) or HPHF (n = 8) and four were sham-operated and fed MPMF. Cats were fed to maintain body weight (BW) for 12 wk and then allowed to overeat for 12 wk. Food intake, BW, body condition scores (BCS), back fat thickness, body composition, feline body mass index, body fat percentage estimates, serum metabolites, and physical activity levels were measured. Over the first 12 wk, caloric intake was reduced at higher amounts in spayed versus sham cats. BW, BCS, body fat percentage, and physical activity levels were altered over time. Our results demonstrate that the diets tested had minor effects, but spaying affected cat food intake, BW, metabolism, and physical activity.

Effects of physical or fenceline boar exposure and exogenous gonadotropins on puberty induction and subsequent fertility in gilts.

The present study was part of a larger experiment that evaluated litter of origin effects on gilt production. The objectives of this study were to determine the effect of physical or fenceline boar exposure and exogenous gonadotropins on puberty induction and subsequent fertility in a commercial farm environment. The experiment was performed in three replicates. Prepubertal gilts were assigned by pen (13/pen) to receive 15 min of daily Fenceline (FBE, n = 153) or Physical (PBE, n = 154) Boar Exposure (BE) for 3 weeks starting at 184 d of age in a purpose-designed Boar Exposure Area (BEAR). At the start of week 3, prepubertal gilts were randomly assigned to receive PG600 or none (Control). From weeks 4 to 6, estrus was checked using only FBE. During weeks 1 to 3, measures of reproductive status were obtained weekly or until expression of estrus. Upon detection of first estrus, gilts were relocated into stalls and inseminated at second estrus. PBE reduced age (P = 0.001) and days to puberty (P = 0.002), increased the proportion of gilts in estrus (P = 0.04) in week 1 (38.3 vs. 27.5%), and tended (P = 0.08) to improve estrus in week 2 (37.6 vs. 26.1%) compared to FBE, respectively. In week 3, more prepubertal gilts receiving PBE-PG600 exhibited estrus (P = 0.04; 81.8%) compared to PBE-Control (40.3%), FBE-PG600 (56.4%), and FBE-Control (47.8%). Overall, expression of estrus through week 6 tended (P = 0.08) to be greater for PBE than FBE (91.5 vs. 85.0%). PBE increased (P ≤ 0.05) or tended to increase (P > 0.05 and ≤0.10) service and farrowing rates in parities 1 through 4, but within parity, there were no effects (P > 0.10) on pig production or wean to service interval. Analyses also indicated that weeks from start of boar exposure to puberty, litter of origin traits, and follicle measures at puberty were related to the subsequent fertility. The results of this study confirm the advantages of using increased intensity of boar exposure, combined with PG600 treatment, for effective induction of pubertal estrus in a commercial setting.

Investigation into the variation in follicular and endocrine responses of prepubertal gilts treated with exogenous gonadotropins.

The gonadotropin compound, PG600, is used to induce estrus in prepubertal gilts, but responses can be variable. This study was conducted to evaluate PG600 effects on follicles, estrus, ovulation and estrogen production. Prepubertal gilts (n = 50) were treated with PG600. Gilts were evaluated for estrus while daily boar exposure was occurring. A sub-population of gilts (n = 12) were slaughtered on Day 3 to assess cytochrome P450 aromatase (CYP19) immunohistochemical staining in ovarian antral follicles. Ovaries of the remaining gilts (n = 38) were evaluated on Day 3 using ultrasonography and blood samples were collected for quantifying estradiol-17ß. On Day 3 following administration of PG600, 94.0 % of gilts had large follicles, but only 76.3 % had expressed behavioral estrus by Day 6. Furthermore, 92.1 % of gilts had ovulations, with 16.6 corpora lutea/gilt. There was no association of number of large follicles on Day 0 or 3 with occurrence of estrus or ovulation (P >  0.05). Estradiol-17ß concentrations on Day 3 did not differ (P >  0.05) in anestrus compared to estrual gilts and varied in gilts with large antral follicles. Immuno-detection of CYP19 on Day 3 was greater (P <  0.01) in large and medium compared to small follicles, (64.3 %, 34.2 % and 14.7 %, respectively). Results validate there is a dissociation of large follicle development with estrogen production on Day 3 in gonadotropin-treated gilts. These results indicate failure to express estrus may be due to follicle variation in estrogen production or response to estrogen feedback at the hypothalamus.

Effects of the number of sperm and site of uterine semen deposition on conception rate and the number of embryos in weaned sows receiving a single fixed-time insemination.

Reducing the number of sperm needed to produce a litter with artificial insemination (AI) allows greater use of higher genetic merit boars. Induced ovulation with single fixed-time artificial insemination (SFTAI), combined with intrauterine (IUI) or deep uterine insemination (DUI), could improve fertility with low numbers of sperm. The objectives of the study were to determine the fertility effects of sperm numbers and the site of insemination. At weaning (0 h), sows (n = 534) were assigned by parity and estrus induction method (equine chorionic gonadotropin [eCG] or Control) to receive 1,200 × 106 sperm by IUI; 600, 300, or 150 × 106 sperm by IUI or DUI; or 75 × 106 sperm by DUI. At 80 h postweaning, sows received OvuGel and 26 h later a SFTAI using pooled semen. Sows were exposed to boars once daily and ultrasound was performed to determine follicle size and time of ovulation. Following SFTAI, sows were slaughtered 27 d after AI to determine pregnancy and litter traits. Data were analyzed using different models to test for effects of estrus induction, interaction of three levels of sperm (600 to 150) with two levels for site (IUI vs. DUI), and the overall effects of AI method (eight treatments). There was no effect (P > 0.05) of estrus induction on estrus (93%) within 5 d of weaning or on follicle size (6.1 mm) at OvuGel, but wean-to-estrus interval (3.8 vs. 4.0 d) was slightly reduced (P < 0.01) as was AI-to-ovulation interval (15.9 vs. 17.0 h, P = 0.04) for eCG and Control, respectively. There was no effect (P > 0.05) of estrus induction on pregnancy rate (78.6%), number of corpora lutea (CL; 21.7), or number of viable embryos (12.2). There was no effect of number of sperm or site of insemination and no interaction (P > 0.05) on pregnancy rate (range: 80.9% to 70.5%), but AI occurring after ovulation reduced the pregnancy rate (P < 0.02). The total number of embryos (range: 16.5 to 10.3) was not affected by estrus induction, number of sperm, or site of insemination (P > 0.05), but was influenced by AI treatment (P < 0.01). Treatments with a higher number of sperm (1,200 and 600) had more embryos compared with those with a lower number of sperm (300 to 75). The numbers of embryos also increased with the number of CL (P < 0.0001). These results suggest that the lower number of sperm affects litter size more than the pregnancy status. Acceptable fertility can be achieved with low numbers of sperm when using a SFTAI and uterine deposition, but AI-to-ovulation interval and ovulation rate influence final fecundity.

Effects of flush feeding strategy before breeding on reproductive performance of modern replacement gilts: impacts on ovulation rate and litter traits.

AbstractThe effects of two feed levels offered during two estrous cycles before insemination were evaluated on the reproductive performance of gilts. A total of 93 gilts (PIC Hendersonville, TN) were individually housed and manually fed twice a day with 2.1 or 3.6 kg/d of a corn and soybean meal-based diet (3.15 Mcal ME/kg and 0.64% standardized ileal digestible lysine), during two estrous cycles before breeding (cycle 1, between first and second estrus; cycle 2, between second and third estrus). Gilts were weighed at the beginning of the experiment, at second and third estrus, and at slaughter (30.2 ± 1.2 d of gestation). Follicles were counted at second estrus, and the embryo-placental units and the corpora lutea were individually counted, measured, and weighed at slaughter. Gilts fed 3.6 kg/d had greater BW gain during cycle 1 and cycle 2 (P < 0.001; + 9.8 kg and + 10.0 kg, respectively) becoming heavier at second and third estrus (P < 0.001). At second estrus, gilts fed 3.6 kg/d had 1.6 more medium-large follicles (P = 0.074) but no difference in follicle size (P = 0.530) was observed. Gilts fed 3.6 kg/d in cycle 1 or cycle 2 had a greater ovulation rate at third estrus (P < 0.016) than those receiving 2.1 kg/d. Also, 3.6 kg/d in cycle 2 increased early embryo mortality (P = 0.006; 2.3 vs. 1.1 dead embryos) and consequently reduced total embryo survival (P = 0.002; 84.6 vs. 90.1%). Gilts fed 3.6 kg/d during cycle 1 had two more total embryos (P < 0.001; 17.2 vs. 15.1) and two more vital embryos on day 30 (P < 0.001; 16.7 vs. 14.5) in comparison with gilts fed 2.1 kg/d. The coefficient of variation for placental length was greater for gilts fed 3.6 kg/d during cycle 1 (P = 0.003). No further significant effects of feeding levels were observed on embryo and placental traits (P ≥ 0.063). These results suggest that the feeding level during the first cycle after pubertal estrus is crucial to set ovulation rate and potential litter size for breeding at next estrus. However, flush feeding gilts before insemination can negatively impact litter size by reducing embryo survival when breeding at third estrus.

Effects of feeding melatonin during proestrus and early gestation to gilts and parity 1 sows to minimize effects of seasonal infertility1.

This study tested whether supplemental melatonin given to mimic the extended nighttime melatonin pattern observed in the higher fertility winter season could minimize infertility during summer and fall in swine. Exogenous melatonin was fed during periods coinciding with follicle selection, corpus luteum formation, pregnancy recognition, and early embryo survival. Experiments were conducted at a commercial farm in 12 sequential replicates. In Exp. 1a, mature gilts (n = 420) that had expressed a second estrus were assigned by weight to receive once daily oral Melatonin (MEL, 3 mg) or Control (CON, placebo) at 1400 h for 3 wk starting before insemination at third estrus. In Exp. 1b, parity 1 sows (n = 470) were randomly assigned by lactation length to receive MEL or CON for 3 wk, starting 2 d before weaning. Follicles, estrus, pregnancy, and farrowing data were analyzed for the main effects of treatment, season (4-wk periods), and their interaction. Environmental measures were also analyzed for reproductive responses. In Exp. 1a, there was no effect (P > 0.10) of MEL on age at third estrus (203 d), follicle size after 7 d of treatment (5.0 mm), estrous cycle length (22.6 d), return to service (9.2%), farrowing rate (FR, 80.0%), or total born pigs (TB, 13.6). However, there was an effect of season (P = 0.03) on number of follicles and on gilts expressing estrus within 23 d of the previous estrus (P < 0.005). In Exp. 1b, there was no effect of MEL (P > 0.10) on follicle measures, wean to estrous interval, FR (84.0%), or TB (13.0). But MEL (73.5%) reduced (P = 0.03) estrous expression within 7 d of weaning compared with CON (82.0%) and season (P = 0.001) decreased FR by ~14.0% during mid summer. Also, gilts and parity 1 sows exposed to low light intensity (<45 lx) during breeding had reduced conception (-8%) and farrowing (-15%) rates, compared with higher light intensity. Similarly, high temperatures (>25 °C) during breeding also reduced gilt conception rates by 7%. Although there was clear evidence of seasonal fertility failures in gilts and sows, MEL treatment did not improve fertility in gilts and reduced estrus in parity 1 sows. It is possible that differences in lighting and thermal environments before breeding could explain the differential response to MEL in sows and gilts.

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Factors influencing follicle development in gilts and sows and management strategies used to regulate growth for control of estrus and ovulation1.

Factors that affect follicle health and growth can influence estrus, ovulation, conception, and litter size. Since the majority of the breeding herd is composed of sows, production schedules are established based on synchronized follicle growth following weaning. Insemination of sows over a 3- to 4-d period after weaning facilitates farrowing over fewer days and helps improve the uniformity of pigs at weaning. Synchronized inseminations of the group are reduced when disturbance to the follicular phase results in delayed estrus. The failure of >15 follicles to uniformly progress beyond the 6.0 mm size within 4 d during the follicular phase is associated with delayed estrus and ovulation, reduced ovulation rate, and reduced farrowing rate. In sows, the follicular phase is initiated at weaning by removal of the suckling inhibition, whereas in cycling gilts, luteolysis and clearance of progesterone begins the process. The timing and patterns of follicle-stimulating hormone and luteinizing hormone stimulation to the ovary determine follicle health and selection for ovulation. Interestingly, abnormal wean-to-estrus intervals in sows and deviations from a 19- to 22-d estrous cycle in gilts are associated with reduced fertility. However, in both cases, it is not entirely clear whether the abnormal intervals are a direct result of problems occurring prior to or only during the follicular phase. In prepubertal gilts, the signal for initiating the follicular phase remains elusive, but could reside in differential sensitivity and response to hormone signals at the level of the ovary and brain. Although the mechanisms are not clear, factors such as boar exposure, stress, feed intake, growth rate, and birthweight have been shown to stimulate an early follicular phase. In contrast, inhibitors to follicle growth have been associated with season, heat stress, photoperiod, negative energy balance, poor body condition, slow growth, fewer parities, and short lactation length. Hormonal aids for inducing and delaying the follicular phase, as well as for inducing ovulation are available to aid in synchronized breeding schedules.

Contribution of semen trait selection, artificial insemination technique, and semen dose to the profitability of pig production systems: A simulation study.

The economic impact of selection for semen traits on pig production systems and potential interaction with artificial insemination (AI) technique and semen dose remains partially understood. The objectives of this study were to compare the financial indicators (gross return, net profit, cost) in a three-tier pig production system under one of two selection strategies: a traditional strategy including nine paternal and maternal traits (S9) and an advanced strategy that adds four semen traits (S13). Maternal traits included the number of pigs born alive, litter birth weight, adjusted 21-day litter weight, and the number of pigs at 21 days, and paternal traits included days to 113.5 kg, back fat, average daily gain, feed efficiency, and carcass lean percentage. The four semen traits included volume, concentration, progressive motility of spermatozoa, and abnormal spermatozoa. Simultaneously, the impact of two AI techniques and a range of fresh refrigerated semen doses including cervical AI with 3 × 10(9) (CAI3) and 2 × 10(9) (CAI2) sperm cells/dose, and intrauterine AI with 1.5 × 10(9) (IUI1.5), 0.75 × 10(9) (IUI0.75), and 0.5 × 10(9) (IUI0.5) sperm cells/dose were evaluated. These factors were also evaluated using a range of farrowing rates (60%-90%), litter sizes (8-14 live-born pigs), and a selected semen collection frequency. The financial impact of the factors was assessed through simulation of a three-way crossbreeding system (maternal nucleus lines A and B and paternal nucleus line C) using ZPLAN. The highest return on investment (profit/cost) of boars was observed at 2.33 collections/wk (three periods of 24 hours between collections). Under this schedule, a significant (P < 0.0001) interaction between the selection strategy and the AI technique-dose combination was identified for the gross return; meanwhile, significant (P < 0.0001) additive effects of the selection strategy and AI technique-dose combination were observed for the net profit. The highest gross return was obtained under S13 with IUI0.75 and IUI0.5. The net profit of S13 was 34.37% higher than the traditional S9 (P < 0.0001). The net profit favored IUI0.5 with relative differences of 4.13%, 2.41%, 1.72%, and 0.43% compared to CAI3, CAI2, IUI1.5, and IUI0.75, respectively. The advanced selection strategy proposed including four semen traits is recommended on the basis of the higher profitability relative to the traditional strategy.

Recent advancements in the hormonal stimulation of ovulation in swine.

Induction of ovulation for controlled breeding is available for use around the world, and conditions for practical application appear promising. Many of the hormones available, such as human chorionic gonadotropin (hCG), gonadotropin-releasing hormone (GnRH) and its analogs, as well as porcine luteinizing hormone (pLH), have been shown to be effective for advancing or synchronizing ovulation in gilts and weaned sows. Each of the hormones has unique attributes with respect to the physiology of its actions, how it is administered, its efficacy, and approval for use. The timing for induction of ovulation during the follicle phase is critical as follicle maturity changes over time, and the success of the response is determined by the stage of follicle development. Female fertility is also a primary factor affecting the success of ovulation induction and fixed time insemination protocols. Approximately 80%-90% of female pigs will develop mature follicles following weaning in sows and synchronization of estrus in gilts. However, those gilts and sows with follicles that are less developed and mature, or those that develop with abnormalities, will not respond to an ovulatory surge of LH. To address this problem, some protocols induce follicle development in all females, which can improve the overall reliability of the ovulation response. Control of ovulation is practical for use with fixed time artificial insemination and should prove highly advantageous for low-dose and single-service artificial insemination and for use with frozen-thawed and sex-sorted sperm.

The effect of numbers of frozen-thawed boar sperm and addition of prostaglandin F2α at insemination on fertility in pigs.

Frozen-thawed boar sperm (FTS) has reduced fertility compared to liquid semen. Exogenous prostaglandin administered at insemination has been reported to improve cases of low fertility. This experiment tested the effect of number of FTS and addition of prostaglandin (PGF2α) on fertility. The experiment was performed in replicates using weaned sows (n=24) and synchronized gilts (n=94). All females were induced into estrus using PG600® at weaning or following estrus synchronization. At estrus, females received 0.5, 1.0, or 2 billion motile FTS (n=9 boars) with 0 or 5mg of PGF2α added into each AI dose at insemination. Inseminations occurred at 24 and 36h after onset of estrus and ovulation was monitored by ultrasound. Pregnancy and litter size were determined for sows at farrowing and d 50 of gestation for gilts at slaughter. There was no effect of PGF2α and no interaction with dose of FTS or parity on fertility (P>0.10). Pregnancy rate was affected by FTS dose (P<0.001) with 2.0×10(9) (76.3%) greater than 0.5×10(9) (46.2%) and 1.0×10(9) sperm (48.8±8.0%). Pregnancy rate was not affected by parity (P>0.10) but was influenced by boar (P<0.05). Number of fetuses was also affected by FTS dose (P<0.001) with 2.0×10(9) (10.1) and 1.0×10(9) (9.4) producing more pigs than 0.5×10(9) sperm (6.9±0.9). Litter size was also affected by parity (P=0.001) and boar (P<0.01). These results indicate that AI using 2.0×10(9) FTS can result in acceptable pregnancy rates and litter sizes but with no measurable benefit for addition of prostaglandin.

Novel and traditional traits of frozen-thawed porcine sperm related to in vitro fertilization success.

Cryopreserved semen allows the use of single ejaculates for repeated analyses, potentially improving IVF consistency by eliminating interejaculate variability observed with fresh semen. However, the freezing and thawing processes result in compromised sperm function and IVF success. Semen samples are often screened for motility before use for IVF. Samples that are below a designated motility threshold may be discarded. Our objectives were to determine if post-thaw sperm motility, other traits that may be indicative of sperm function, or a novel assay of oviduct binding were related to IVF success. Semen from 16 boars was cooled to 15 °C for overnight shipment before cryopreservation. Semen was thawed and motility was recorded microscopically and confirmed using computer-automated sperm assessment. Each sample was tested by IVF in two to three independent replicates. Regression and correlation analyses were employed to determine the interrelationships between sperm traits and the relationships between post-thaw motility, sperm-oviduct binding and IVF outcomes. Among the sperm traits examined, sperm acrosome integrity was negatively correlated with post-thaw motility (r(2) = 0.64) but not with IVF results. The number of sperm bound to oviduct aggregates was correlated with IVF polyspermy rates (r(2) = 0.62, P < 0.05) but less with overall IVF rates (r(2) = 0.31, P > 0.10). There was some relationship of post-thaw motility with IVF monospermic fertilization (P = 0.06, r(2) = 0.08) but not to other IVF outcomes. Our results indicate that post-thaw motility of frozen-thawed boar sperm is strongly related to acrosome integrity but has limited use for predicting IVF success. The number of sperm bound to oviduct cells was related to IVF polyspermy rates and may be more indicative of in vitro sperm function than traditional sperm motility and acrosome status evaluation.

Impact of swine reproductive technologies on pig and global food production.

Reproductive technologies have dramatically changed the way pigs are raised for pork production in developed and developing countries. This has involved such areas as pigs produced/sow, more consistent pig flow to market, pig growth rate and feed efficiency, carcass yield and quality, labor efficiency, and pig health. Some reproductive technologies are in widespread use for commercial pork operations [Riesenbeck, Reprod Domest Anim 46:1-3, 2011] while others are in limited use in specific segments of the industry [Knox, Reprod Domest Anim 46:4-6, 2011]. Significant changes in the efficiency of pork production have occurred as a direct result of the use of reproductive technologies that were intended to improve the transfer of genes important for food production [Gerrits et al., Theriogenology 63:283-299, 2005]. While some technologies focused on the efficiency of gene transfer, others addressed fertility and labor issues. Among livestock species, pig reproductive efficiency appears to have achieved exceptionally high rates of performance (PigCHAMP 2011) [Benchmark 2011, Ames, IA, 12-16]. From the maternal side, this includes pigs born per litter, farrowing rate, as well as litters per sow per year. On the male side, boar fertility, sperm production, and sows served per sire have improved as well [Knox et al., Theriogenology, 70:1202-1208, 2008]. These shifts in the efficiency of swine fertility have resulted in the modern pig as one of the most efficient livestock species for global food production. These reproductive changes have predominantly occurred in developed countries, but data suggests transfer and adoption of these in developing countries as well (FAO STAT 2009; FAS 2006) [World pig meat production: food and agriculture organization of the United Nations, 2009; FAS, 2006) Worldwide Pork Production, 2006]. Technological advancements in swine reproduction have had profound effects on industry structure, production, efficiency, quality, and profitability. In all cases, the adoption of these technologies has aided in the creation of a sustainable supply of safe and affordable pork for consumers around the world [den Hartog, Adv Pork Prod 15:17-24, 2004].

Effect of interval between inseminations when using frozen-thawed boar sperm on fertility and fetal paternity in mature gilts.

Multiple artificial inseminations (AI) are used in swine to compensate for variation in time of ovulation and following each insemination, a uterine immune response occurs to remove dead and damaged sperm. There are more dead and damaged sperm inseminated with use of frozen-thawed-semen (FTS) and closer insemination intervals are required to compensate for the reduced lifespan of the sperm. Therefore, the objectives of this experiment were to evaluate the effect of interval between inseminations and estrus to ovulation interval (EOI) on fertility and the impact of each AI using fetal paternity in mature gilts when using FTS. Semen from 11 boars was collected and frozen in 0.5mL straws at 1.4×10(9)cells/mL. Time of estrus was synchronized in gilts (n=191) using Matrix(®) and assigned at estrus to AI treatment: (1) AI at a 4h interval (34 and 38h); (2) AI at an 8h interval (30 and 38h); or (3) AI at a 16h interval (22 and 38h). Ultrasonography was performed to determine time of ovulation. In each treatment, the first and second AI were from unique sires to allow for paternity identification using microsatellite markers. Each sire was represented across first and second inseminations. Gilts received an AI with 2×10(9) motile FTS in 80mL of extender. Pregnancy rate and litter size were assessed at slaughter on Day 33 following AI. Interval between inseminations affected pregnancy rate (P<0.01) with AI intervals of 8 (80%) and 16h (75%) greater than the 4h interval (55%). The EOI also affected pregnancy rate (P<0.001) with increased pregnancy rate for gilts having ovulations by 36h (85%) compared to those having ovulations by 24 (55%) and 60h (47%) but did not differ from those having ovulations at 48h (74%). Total fetuses (10.7), number of normal fetuses (10.2) and embryo survival (70.4%) were not affected by interval between inseminations or EOI (P>0.05). There was an interaction of treatment with EOI (P<0.05). Gilts inseminated at 8 or 16h intervals and with 36 or 48h EOI showed changes (P<0.05) in the proportion of offspring sired by the second AI while gilts inseminated at a 4h interval did not. The results of this study indicate that intervals between inseminations and time of ovulation each affects pregnancy rates but not litter size, but interacts to affect the proportion of offspring sired by the second insemination. This study suggests no detrimental effect of reduced amount of time between inseminations on the fertility of sperm used in a second insemination. For practical application, in a twice daily estrous detection and double AI, the greatest pregnancy rates occur when inseminations are spaced at 8 or 16h intervals to compensate for variation in ovulation.

The impact of dose of FSH (Folltropin) containing LH (Lutropin) on follicular development, estrus and ovulation responses in prepubertal gilts.

FSH is favored over chorionic gonadotropins for induction of estrus in various species, yet little data are available for its effects on follicle development and fertility for use in pigs. For Experiment 1, prepubertal gilts (n = 36) received saline, 100 mg FSH, or FSH with 0.5 mg LH. Treatments were divided into six injections given every 8 h on Days 0 and 1. Proportions of gilts developing medium follicles were increased for FSH and FSH-LH (P < 0.05) compared to saline, but follicles were not sustained and fewer hormone-treated gilts developed large follicles (P < 0.05). No gilts expressed estrus and few ovulated. Experiment 2 tested FSH preparations with greater LH content. Prepubertal gilts (n = 56) received saline, FSH-hCG (100 mg FSH with 200 IU hCG), FSH-LH5 (FSH with 5 mg LH), FSH-LH10 (FSH with 10 mg LH), or FSH-LH20 (FSH with 20 mg LH). FSH-LH was administered as previously described, while 100 IU of hCG was given at 0 h and 24 h. Hormone treated gilts showed increased (P < 0.05) medium and large follicle development, estrus (>70%), ovulation (100%), and ovulation rate (>30 CL) compared to saline. There was an increase (P < 0.05) in the proportion of hormone-treated gilts with follicular cysts at Day 5, but these did not persist to Day 22. These gilts also showed an increase in poorly formed CL (P < 0.05). FSH alone or with small amounts of LH can induce medium follicle growth but greater amounts of LH at the same time is needed to sustain medium follicles, stimulate development of large follicles and induce estrus and ovulation in prepubertal gilts.

Effect of number of motile, frozen-thawed boar sperm and number of fixed-time inseminations on fertility in estrous-synchronized gilts.

There are advantages for use of frozen-thawed boar sperm (FTS) as a tool for preservation and transfer of valuable genetic material, despite its practical limitations. It was hypothesized that increasing the number of motile FTS and number of fixed-time artificial inseminations (AI) would improve pregnancy rate and litter size. Semen from six boars was frozen in 0.5mL straws at 500x10(6)cells/mL. Gilts approximately 170 days of age, were induced into estrus with PG600 and synchronized using MATRIX (synthetic progestagen). Following last feeding of MATRIX (LFM), gilts were checked twice daily for estrus. At onset of estrus, gilts were randomly assigned in a 3x2 factorial treatment design to receive 1x10(9) motile FTS (n=19), 2x10(9) motile FTS (n=19), 4x10(9) motile FTS (n=19) in a single AI at 32h after onset of estrus, or 1x10(9) motile FTS (n=18), 2x10(9) motile FTS (n=17), or 4x10(9) motile FTS (n=19) in each of the two AI at 24 and 32h following onset of estrus. Ultrasonography was performed at 12h intervals after estrus to estimate time of ovulation. Reproductive tracts were collected 28-34 days following AI. Estrus occurred at 139+/-2h (mean+/-SE) after LFM and ovulation at 33+/-1h following onset of estrus. Dose and number of inseminations did not interact or individually influence pregnancy rate at slaughter (73+/-4.2%) or numbers of normal fetuses (10.8+/-0.5). However, number of fetuses tended (P=0.14) to increase with double AI but not with dose. Boar did not affect pregnancy rate but did affect number of normal fetuses and embryonic survival (P<0.01). Longer intervals from insemination to ovulation reduced pregnancy rate (P<0.05), number of normal fetuses (P<0.001), and embryonic survival (P<0.01). Ovarian abnormalities at slaughter were associated with reduced pregnancy rate (P<0.001). The results of this experiment indicate that a double insemination using 2x10(9) motile sperm would produce the greatest number of piglets with fewest numbers of frozen sperm used, while double AI with 1x10(9) motile sperm would be most practical for pig production with limited genetic resources. Fertility was also influenced by boar, interval from insemination to ovulation, and gilt ovarian abnormalities.

Evaluation of methodology for administration of porcine FSH for use in estrus induction and for increasing ovulation rate in prepubertal gilts.

Ovulation rate influences production efficiency of oocytes and embryos and depends upon the amount of gonadotropin administered and the ratio of FSH:LH activity. In Experiment 1, gilts (n=135) were assigned to receive 10 or 15 Armour units (AU) of porcine FSH containing 6%, 10%, or 15% LH, whereas controls received PG600. Gilts received 1/6th the FSH dose in six sc administrations at 8-h intervals. There was no treatment effect on incidence of estrus (66%) or cysts (23.9%), or number of corpora lutea (CL, 29.6). However, treatment did affect the percentage of gilts ovulating (P<0.05) with fewer 10 AU FSH with 15% LH-treated gilts ovulating (15%) compared to controls (72%), whereas the other treatments did not differ (range, 44-65%). Experiment 2 tested whether FSH in polyvinlypyrrolidinone (PVP) could induce estrus and ovulation with reduced administration frequency. Gilts (n=105) were assigned to receive 15 AU FSH with 10% LH in one (1P) or two sc administrations (2P) whereas controls received PG600. There was no treatment effect on incidence of estrus (64%) or cysts (22%). However, the percentage of gilts ovulating was lower for 1P (56%), but did not differ (P<0.05) between 2P (83%) and controls (85%). Treatment influenced ovulation rate (P<0.05) with 2P having more CL (24) than controls (12) and 1P (19). Results indicated that 10 and 15 AU FSH induced estrus and ovulation, although high LH content proved detrimental. Further, 15 AU FSH with 10% LH in PVP allowed for reduced administration frequency without compromising ovulation.