Over numerous years, breeding herds have faced challenges to sustainability with poor profitability, impact of disease, export market instability, limited labor, and increasing environmental and animal welfare regulations. Many of these scenarios are expected to continue, but their impact lessened with adjustments in management, technology, and business. The prospects for success in the future for the pig industry in various locations are based on costs of pig production efficiency and projections for domestic and export markets. Sow farms are expected to increase in size to meet large retailer needs, while smaller farms will fill domestic regional markets. The risk of PRRS in breeding herds and loss of pigs and infertility will continue to be a major concern for producers. Changes in sow housing will likely continue with designs that meet welfare requirements and allow for practical management of the breeding herd. Trends for selection and increase in litter size will continue but will include measures for birthweight and survival, and traits for heat stress and disease resistance. Changes in boar semen production and AI procedures are unlikely since fertility measures are very high. But advances in technology for identifying fertile and time of ovulation, or procedures that aid in selection of sperm or induction of ovulation, could facilitate reduction in the number of sperm used to produce a litter of pigs.

Buserelin acetate, a synthetic analog of gonadotropin-releasing hormone (GnRH), is used to induce ovulation and enable fixed-time artificial insemination (FTAI) in swine. Evaluating the pharmacokinetics of buserelin acetate is crucial for optimizing its application in precisely controlling ovulation timing and enhancing the effectiveness of FTAI in pigs. This study investigates the pharmacokinetics of buserelin acetate following intramuscular administration in gilts. Ten healthy prepuberty gilts (Landrace × Yorkshire × Duroc) with an average body weight of 72.0 ± 3.4 kg were included in the study. Before treatment, all ten gilts underwent surgical implantation of an indwelling venous catheter to allow repeated blood samplings for pharmacokinetic assessment. On Day 3 after surgery, each gilt received an intramuscular injection of 100 μg buserelin acetate (25 mL of 4 μg/mL Receptal, MSD Animal Health, USA). Blood samples (5 mL each) were collected 14 times from each gilt via the jugular catheter at the following time points: 0, 2, 5, 10, 15, 20, 30, and 45 min, as well as 1, 1.5, 2, 3, 4, and 6 h post-injection. Blood samples were collected into heparinized tubes, centrifuged to separate the plasma, and stored at -20°C until analysis. Plasma buserelin concentrations were then determined using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). The LC-MS/MS system operated in positive ion mode using electrospray ionization with multiple reaction monitoring. Buserelin was quantified based on precursor/product ion pairs identified in the chromatogram. The calibration curve for buserelin acetate in pig plasma showed high linearity (R2 ≥ 0.99), with a lower limit of quantification of 0.30 μg/L. The findings showed that the average maximum plasma concentration (Cmax) of buserelin acetate was 2.21 ± 0.72 μg/L, occurring at 0.30 ± 0.10 h (Tmax) after administration. The elimination half-life (T1/2) was 0.51 ± 0.03 h. The area under the concentration-time curve from 0 to the last measurement point (AUC0-t) was 7.30 ± 0.87 μg·h/L. The clearance rate (CL) was 0.20 ± 0.03 L/h/kg, and the apparent volume of distribution (Vd) was 0.13 ± 0.05 L/kg. These results suggest that buserelin acetate from Receptal is rapidly metabolized and eliminated in gilts, emphasizing the need for precise timing of administration to maintain effective drug concentrations.

Increasing use of semen from superior sires can accelerate genetic improvement when using a single fixed-time AI (SFTAI) to reduce the number of sperm required to produce a litter. The objectives of this study were to: 1) Assess whether follicle development, ovulation, and insemination was altered by parity and season in OvuGel and Controls; 2) Determine the impact of Day of OvuGel administration and estrus in Controls; and 3) Evaluate OvuGel and Control interactions with parity and season on farrowing rate and litter size. The experiment was performed in replicates in summer and fall with sows assigned from Monday and Thursday wean groups by parity to OvuGel or Control after weaning (Day 0). Sows received OvuGel (n = 1,636) on Days 3, 4 or 5 based on proestrus or estrus symptoms and then a SFTAI 24 h later. Controls with a wean to estrus interval of 3 to 6 d (n = 1,676) received an AI on each day standing. Ovaries of a sub-population of the Thursday weaned sows (n = 445) were scanned by ultrasound. The number (17.5) and size (7.0 mm) of ovulatory follicles on Day 4 did not differ between treatments, but P1 and P2 sows had smaller follicles and sows weaned in Sep-Oct had fewer and smaller sized follicles (P ≤ 0.05). OvuGel increased (P = 0.004) ovulation by Day 6 (92.2%) compared to Control (79.4%). Sows with large follicles on Day 4 were more likely to ovulate (87.8%, P < 0.0001) by Day 6 than those with medium (62.1%). Although there was no interaction with parity, ovulation was lower in the Control for parities 1, 2, and ≥ 7. OvuGel treatment on Days 3 or 5 reduced (P = 0.0003) farrowing rate (FR) by 7 to 11% and were excluded from further analyses. Day 4 OvuGel treatment had no effect on FR (86.7 vs. 87.4%) or total born (TB) compared to Control (13.2 vs. 13.4), respectively. Interactions were due to OvuGel improving FR in P1 sows (87.9 vs. 76.5%) and for sows weaned in Jul-Aug (89.2 vs. 83.4%) compared to Control, respectively. There was an effect of day of weaning that was linked to semen storage (P = 0.02) indicating 4 to 5 d (84.5%) reduced FR compared to ≤ 3 d (91.3%). The effect was evident with the SFTAI but not Control and was thought to originate with changes in fertility with additional days of handling and storage in summer. The results indicate OvuGel treatment on Day 4 at proestrus or estrus and followed by a SFTAI has great potential to mimic the fertility performance of conventionally inseminated sows.

Volatile organic compounds (VOCs) in boar secretions function as key semiochemicals that influence gilt reproductive behavior and facilitate puberty onset. Identifying these compounds is essential for understanding the mechanisms underlying the boar effect. This study aimed to characterize and compare VOCs in urine, preputial fluid, and preputial swabs of intact and castrated boars to identify potential pheromone candidates involved in sexual communication. Two groups of Duroc pigs were studied: five intact boars (1-3 years old) routinely used to induce estrus in replacement gilts, and five castrated boars at the end of the fattening period (average age 154 days, 90-100 kg). All animals were clinically healthy and maintained under similar climatic, housing, and nutritional conditions. Fresh urine (5 ml), preputial fluid (5 ml), and preputial swabs were collected, stored at 4 °C, and analyzed within 5 h. VOCs were extracted by headspace solid-phase microextraction and identified using gas chromatography-mass spectrometry. A total of 23 VOCs were detected across sample types, exhibiting diverse odor properties, including minty, woody, fruity, and sulfurous notes, which could act as sexual attractants. Quantitative analysis revealed that fenchol, styrene, 3-carene, 2-ethylhexanal, and cyclopentanol, 3-methyl- were significantly higher in intact boar urine (P < 0.05), whereas p-thymol and 2,2',5,5'-tetrachlorobiphenyl were more abundant in castrated boars. In preputial fluid, intact males had elevated 3-carene, α-terpineol, styrene, 2-hexanol, and cyclohexyl methyl sulfide compared with castrated males (P < 0.05). Preputial swabs from intact boars also showed higher levels of cyclohexyl methyl sulfide, 3-carene, β-terpineol, dodecane, 2,6,11-trimethyl-, and isocineol related terpenoids compared with castrated males (P < 0.05). In conclusion, this study identified several VOCs, including 3-carene, α-pinene, α-terpineol, and cyclohexyl methyl sulfide, as potential pheromone candidates contributing to sexual signaling and the boar effect.

Identifying the reproductive status of replacement gilts at the appropriate age can improve mating efficiency and reduce non-productive days. This study aimed to evaluate the reproductive status of gilts and assess the accuracy of a serum progesterone strip test. A total of 112 Landrace × Yorkshire gilts, aged 196-238 days, were enrolled. Estrus detection was performed daily from 189 days of age using the back-pressure test with fence-line boar exposure. Blood samples were collected from all gilts, and serum progesterone levels were determined using both ELISA and a progesterone lateral flow assays (LFAs) strip test. Puberty was defined by an ELISA-based serum progesterone concentration ≥5.0 ng/ml. The LFAs employed a competitive assay using a monoclonal antibody against progesterone. A single test line indicated a 'positive' result (pubertal), while two lines indicated 'negative' (prepubertal). To perform the test, 2-3 drops of serum were applied to the strip, with results read after 15 min. Based on ELISA, 51.8 % of gilts were pubertal and 48.2 % were prepubertal. Pubertal gilts had significantly higher serum progesterone levels than prepubertal gilts (30.8 ± 11.4 vs. 0.8 ± 0.8 ng/ml; P < 0.001). The LFAs correctly identified 98.2 % of pubertal gilts and 94.4 % of prepubertal gilts, yielding a sensitivity of 98.2 % and specificity of 94.4 %. In conclusion, the progesterone strip test demonstrated high accuracy and shows strong potential for on-farm use in identifying pubertal gilts based on serum progesterone concentration.

Some assisted reproductive technologies (ART) are used commonly in animals throughout much of the world, most often to improve agricultural animal reproduction. For example, the advances in artificial insemination (AI) technology have enabled animal breeders to collect, extend, and store the sperm from sires with improved genetic traits for breeding multiple females at different locations. Advances in semen processing technology have enabled the development of sex sorting of sperm and alternative forms of storage. Embryo transfer is an ART that is fairly common commercially in cattle and in vitro fertilization is becoming more common. Most other ART are used primarily in animals as research tools.

Administering exogenous GnRH at the onset of standing estrus induces ovulation within ∼37.5 ± 3.3 h by stimulating LH secretion, narrowing the optimal insemination window. This study evaluated the effects of supplementing extended boar semen with a GnRH analog (buserelin) for fixed-time AI on conception rate, farrowing rate, and litter size under tropical field conditions. A total of 741 French Landrace × Yorkshire females (319 gilts, 422 sows) were used across nine replicates. After estrus detection, females were randomly assigned to four groups: control (n = 191), 10-IM (n = 183; 10 μg buserelin i.m.), 5-S (n = 181; semen + 5 μg), and 10-S (n = 186; semen + 10 μg). Gilts were inseminated at 0, 12, and 24 h; sows at 12, 24, and 36 h post-estrus. Litter data were collected from 223 farrowings: control (29 gilts, 34 sows), 10-IM (16 gilts, 35 sows), 5-S (29 gilts, 25 sows), and 10-S (27 gilts, 28 sows). Across groups, average farrowing rate was 88.9 %, with total number of piglets born per litter (TB) 17.0 ± 4.0, number of piglets born alive per litter (BA) 15.2 ± 3.5, stillborn 1.0 ± 1.5, and mummified fetuses 0.5 ± 1.2. No significant differences in conception or farrowing rates were found. The 5-S group had a significantly higher litter weight than the control group (24.5 ± 2.0 kg vs. 19.4 ± 0.7 kg; P = 0.018). Gilts receiving 5 μg buserelin in semen had significantly higher TB, BA, and litter weight (P < 0.05), while 10 μg increased litter weight without affecting TB. In sows, no significant improvements were observed. These results suggest that supplementing semen with low-dose GnRH analog can improve gilt productivity under tropical conditions and merits further investigation.

Climate change has been linked to increasing temperatures and weather extremes. Certain regions around the world become more susceptible to environmental hazards that limit pig production and reproductive fertility. Environmental measures that link to pig fertility are needed to assess change, risk and develop solutions. Sub-populations of pigs display lower fertility in summer and are susceptible to heat stress. In the context of a warming climate, elevated temperatures and number of heat stress days increase body temperature and change the physiology, behavior, feed intake, and stress response of the pig. These changes could alter follicle development, oocyte quality, estrus expression, conception and litter size. In boars, sperm quality and production are reduced in response to summer heat stress. Nevertheless, while temperature increases have occurred over the years in some warmer locations, other regions have not shown those changes. Perhaps this involves the measures used for heat stress assessment or that climate is buffered in more temperate areas. Reductions in pig fertility are not always evident, and depend upon climate, year, genotype and management. This could also involve selection, as females more susceptible to heat stress and fertility failure, are subsequently culled. In the years from 1999 to 2020 when increases in global temperature from baseline occurred, measures of female fertility improved for farrowing rate and litter size. Progressive reduction in fertility may not be apparent in all geo-locations, but as temperatures increases become more widespread, these changes are likely to become more obvious and detectable.

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. Lay Summary 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. A proportion of primiparous sows nursing a large litter lose more body weight and a greater number of piglets during lactation compared to those nursing fewer piglets. However, the prolific modern sow demonstrated excellent potential to wean more piglets without detrimental consequences to subsequent fertility.

This work aims to evaluate how supplementing a commercial freezing media with butylated hydrox-ytoluene (BHT), or reduced glutathione (GSH), or their combination affected in-vitro measures of boar sperm after cryopreservation. One ejaculate was collected from 30 high-fertility boars in a weekly collection rotation. Samples were diluted 1:1 in an extender and cooled before overnight shipping at 17 degrees C to the freezing lab. On arrival, samples were split into the treatments with the following additions before cryopreservation; 1) semen without additional antioxidants (Control), 2) semen with 1 mM BHT, 3) semen with 2 mM GSH, and 4) semen with 1 mM BHT+2 mM GSH. Semen was evaluated for motility kinetics at 30,120, and 240 min after thawing. Flow cytometry assessments were performed at 60 min after thawing. At all-time points evaluated, total and progressive motility were greater (P < 0.05) in semen cryopreserved with GSH than in Control. No (P > 0.05) differences between Control and other treatment groups were observed in viability, or acrosomal and mitochondrial membrane integrity; however, the proportion of capacitated spermatozoa were reduced (by-21.17%) in semen treated with BHT + GSH compared to Control (P < 0.05). In contrast, there was a higher (P < 0.05, +21.18%) superoxide anion production in the Control than in the BHT + GSH. For IVF, semen cryopreserved with both anti-oxidants (BHT + GSH) had a negative (P < 0.05) impact on fertilization rate (-54.11%) compared to Control. However, for the blastocysts rate, there were more (+22.75%) blastocysts (P < 0.05) for BHT compared to Control. These results indicate that commercial media supplemented with GSH increased motility but impaired in vitro fertilization rate. On the other hand, media supplemented with BHT improved the in vitro fertilizing ability of the frozen-thawed sperm cells. Therefore, we suggest the supplementation with 1 mM of BHT in the formula of commercial freezing media used in the present experiment.(c) 2023 Elsevier Inc. All rights reserved.

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.

When preserving sperm in the liquid or cryopreserved state, seminal plasma (SP) components within ejaculates can alter fertilizing capacity of these gametes. Depending on the species or how semen is collected, volume and concentration of SP components varies considerably. The SP contains substances essential for maintenance of sperm viability and fertility; however, these components can be deleterious depending on quantity, or duration of time before there is removal of SP from sperm in semen processing. Substances that impair (e.g., BSP – bull; HSP-1 – stallion; Major seminal plasma protein PSPI - boar) or improve (e.g., spermadhesin PSP-I - boar) spermatozoa fertilizing capacity have been identified. Depending on individual males, species, and semen collection procedures, SP removal may be beneficial before preservation in the liquid or cryopreserved state. In some cases, SP that is removed can be added back to thawing extender with there being positive effects in thawed sperm and for sperm viability in the female reproductive tract. In this review article, there is a focus on different effects of SP in samples of cooled and cryopreserved semen from four domestic species (pigs, horses, cattle, and sheep) with there being emphasis on how SP modulates the function and morphology of sperm cells before, during, and after preservation in the refrigerated or cryopreserved state. The present review is part of the Festschrift in honor of Dr. Duane Garner who made major contributions to the area of focus in this manuscript as evidenced by the many times his research is cited in this manuscript.

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±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, 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 (wk 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, while 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.

This study was conducted to evaluate whether there were differences in viability of cryopreserved semen when using two different freezing (Minitube Cryoguard - F1 or Androstar (R) CryoPlus - F2) and thawing (Minitube Cryoguard Thawing solution - T1 or Androstar (R) Plus - T2) extenders. Ejaculates were collected, diluted (1:1), and cooled before shipping at 17 degrees C overnight. Samples were aliquoted in cryopreservation extender F1 or F2. Four straws from each treatment sample were thawed and diluted in T1 or T2, resulting in four treatments (F1-T1, F1-T2, F2-T1, and F2T2). The sperm in diluted semen were evaluated for motility kinetics at 30, 180, and 360 min after thawing. The integrity assessments of the plasma and acrosomal membranes were performed at 30 and 360 min after thawing. There was no interaction between F x T x Time (P > 0.05), and no interaction between F x T (P > 0.05). The sperm progressive motility (PMOT) as time postthawing increased was greater (P = 0.015) when dilutions occurred using F1 compared with F2 extender. Sperm thawed in T1 had a greater TMOT (P = 0.008) and PMOT (P = 0.033) at all times evaluated. The sperm plasma and acrosomal membrane integrity (AIMI) were greater (P = 0.009) when samples were preserved in F1 compared to F2 extender. The use of T2, as compared with T1 thawing extender, resulted in an enhanced integrity of the plasma and acrosomal membranes (P = 0.008). It is concluded different combinations of commercial freezing extenders and thawing solutions have effects on the quality of cryopreserved boar semen in vitro.

Management of fertility determines production efficiency. Important fertility measures include detection of estrus (DE), early pregnancy confirmation (EPC), and day of farrowing (DF) with few tools available to diagnose or predict. Electrical impedance spectroscopy (EIS) uses an array of frequencies to determine tissue resistance in relation to change. Our objective was to determine if EIS can predict reproductive events. The study was conducted for DE using weaned sows (n = 135) scanned on D 1-7; EPC used inseminated sows (n = 135) scanned on D 18-20; DF used pregnant sows on D 113 to farrowing. The EIS device used a four-electrode transducer with an internal processor and was connected to a mobile device for operation, reading, and data storage. The device obtained impedance (Ω) and phase data for analysis from 42 frequencies between 1,000 and 29,000 Hz. The device was disinfected and inserted into the vagina with scans requiring ~20 s. Data were uploaded to a server and stored on a website for labeling and analysis. Accuracy was based on DE, EPC on D 30, and DF. Data were analyzed in RStudio using GLM with logistic regression to generate log-likelihood estimates for r2 and associated P values. Predictive models for DE, EPC, and DF included EIS, day of measure, and parity. For DE, prediction was greatest 1 d before and on estrus (r2 = 0.98), moderate 3 to 4 d before estrus (r2 = 0.59), and not predictive ≥4 d before estrus. For EPC, the measures for EIS were not predictive due to limited numbers of non-pregnant sows (3%). For DF, prediction for 1 d before was (r2 = 0.98), for 2 d (r2 = 0.89), and for 3 d (r2 = 0.51). Our preliminary results suggest impedance of the sow vagina can be used to predict events, but more data for failures and days will be needed to improve prediction.

This chapter describes the factors that affect boar fertility, including housing and environment, health and diseases and behaviour, and how to perform semen collection, semen characteristics, cryopreservation and artificial insemination.

Efficient management of gilts requires optimizing boar stimulation to induce a synchronized pubertal estrus for breeding at the optimal stage of body maturity. However, variation in stimulation methods and environment can reduce synchrony, delay puberty, and lead to breeding less than ideal gilts. These issues add open day costs, disrupt animal flow, and can reduce lifetime productivity and longevity. Emphasis on employee training and support with regular assessment and opportunities for feedback can help, especially with daily labor rotation and employee turnover. Certain principles of gilt management, such as methods to maximize boar stimulation, must be applied, while adjusting for available labor and gilt housing. Evaluation for effectiveness often only includes the proportion of gilts mated and those culled due to anestrus. However, a holistic system may need to include gilt selection criteria, pubertal response, and subsequent herd performance. Further, symptoms of estrus vary by gilt, technician interpretation, stimuli applied, and environment. These symptoms can range from clear positive to clear negative or even uncertain and may change within the timeframe of assessment. Effective methods are needed to help producers in gilt selection, evaluation of stimulation, reproductive status diagnosis, and impact of nutrition and environment. Practical approaches that aid in selection based on dam and birth measures, as well as age, growth, and weight are needed. Evaluation of the quality of the stimuli applied from the boar and technician should advance from subjective toward precision. Methods to accurately diagnose the reproductive status of the gilt may include semi or automated sensing systems or manual approaches for measuring hormones, body temperature, vaginal resistance, ovarian and uterine structures, animal behavior, motion, and posture. To be useful, selected methods must be evaluated for their practicality, flexibility in farm systems, costs, accuracy, labor, and actionable perspective.

This study was conducted to determine whether exogenous melatonin affected gilt fertility when there were different housing temperature and lighting conditions. Prepubertal gilts (n = 72) were fed (MEL, 5 mg/day) or not fed (CON) melatonin while housed in rooms where temperatures (31.0 +/- 1 degrees C) and daily lighting (240 lx) duration differed: 8 (8 H); 16 (16 H); or 24 (24 H) h in winter and summer replicates. Gilts were moved into rooms (day 1) and administered PG600 on day 6. Gilts detected in estrus were inseminated and slaughtered on day 33 of gestation to determine pregnancy and litter responses. There was no treatment x room effect on estrus (77.8 %), follicle sizes, or number of corpora lutea, but MEL-treated gilts had a longer (P = 0.02) estrous duration (2.0 d) than gilts of the CON (1.7 d) group. Pregnancy rate (92.6 %) and embryo number (13.5) were not affected by treatment or room conditions. There was a treatment x room effect, however, with embryo survival being less (P = 0.01) by similar to 23 % in gilts of the CON-24H than CON-16H, MEL-8H, and MEL-24H groups. In the summer replicate, there were also fewer large follicles, a lesser estrous detection percentage, viable embryos, and embryo survival rate than during the winter (P < 0.05). Overall, MEL treatment had positive effects on estrous duration and embryo survival, especially in the summer when there were varying lighting regimens and room temperatures in which gilts were housed.

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.

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.