Search

The aim of this study was to evaluate the effects of dietary supplementation with different fish oils (rich in PUFA) vs. hydrogenated animal fat (SFA) on semen production and quality, fatty acid composition, and preservation properties in boars under controlled and commercial conditions. In Exp. 1 (in a research station), 44 boars, allocated to 4 dietary treatments, received daily 2.5 kg of basal diet with a supplement of 1) 62 g of hydrogenated animal fat (AF, n = 12); 2) 60 g of menhaden oil containing 18% docosahexanoic acid (DHA) and 15% eicosapentanoic acid (EPA; MO, n = 11); 3) 60 g of tuna oil containing 33% DHA and 6.5% EPA (TO, n = 11); and 4) 60 g of menhaden oil and 2 mg/kg of biotin (MO+B, n = 10). Biotin is a critical factor in the elongation of PUFA. Semen was collected according to 3 successive phases: phase 1 (twice per week for 4 wk); phase 2 (daily collection for 2 wk); and phase 3 (twice per week for 10 wk). Experiment 2 was conducted in commercial conditions; 222 boars were randomly allocated to AF, MO, and TO treatments. Semen was collected twice weekly over a 6-mo period. All diets were balanced to be iso-energetic and provided an equivalent of 989 mg of vitamin E per day. Classical measurements of sperm quantity and quality were done for both experiments. Experiment 1 showed, after 28 wk of supplementation, a massive transfer of n-3 PUFA into sperm from boars fed fish oil diets (MO and TO). No differences were observed among dietary treatments for libido (P > 0.30), sperm production (P > 0.20), or percentage of motile cell (P > 0.20). Unexpectedly, MO+B diet reduced the percentage of normal sperm compared with the other treatments (P < 0.03). In conclusion, although it modified the fatty acid composition of sperm, supplementation of boars with dietary fish oils, rich in long chain n-3 fatty acids, did not influence semen production or quality postejaculation. Key words: boar, fish oil, n-3 fatty acid, reproductive performance, semen quality, spermatozoa doi: 10.2527/jas.2009-2779

The objectives of this study were 1) to determine whether selection toward less subcutaneous fat thickness at constant intramuscular fat content in pigs is related to tissue-specific changes in the expression of lipogenic enzymes acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase (SCD), and A% desaturase ([DELTA]6d); and 2) to investigate tissue specific distribution of the porcine ACC, SCD, and [DELTA]6d. The study was conducted on 20 purebred Duroc barrows. Ten animals were from a group selected for decreased subcutaneous fat thickness at constant intramuscular fat content (experimental group). The other 10 animals were from the unselected (control) group. Distribution of ACC, SCD, and [DELTA]6d was investigated in semimembranosus muscle (SM), subcutaneous adipose tissue (SA), liver (L), kidney (K), heart (H), diaphragm (D), rectus capitis muscle (RCM), and abdominal fat (AF). The enzyme expression was studied in 10 animals in the case of SM and SA and in 4 animals in the case of other tissues. The following expression pattern was established for ACC: SM [less than or equal to] H = K [less than or equal to] D< RCM < L < AF = SA, whereas the expression patterns for SCD and [DELTA]6d proteins were SM < H < RCM < D < L < K < AF = SA and RCM = SM = D < L [less than or equal to] H < SA < K < AF, respectively. Expression of ACC and SCD proteins was less in subcutaneous adipose tissue of the experimental animals when compared with the control group (P < 0.001). However, no difference (P > 0.1) in ACC and SCD protein expression between the control and experimental groups was observed in SM. Expression of [DELTA]6d protein did not differ between the control and experimental groups for SA (P = 0.47) or SM (P = 0.31). There was a positive relationship between muscle SCD protein expression and intramuscular fat content (r = 0.48, P < 0.05). Intramuscular fat content did not correlate with ACC or [DELTA]6d protein expression (P = 0.23 and P = 0.80, respectively). We conclude that SCD might be an effective potential biomarker for intramuscular fat deposition. Key words: intramuscular fat, lipogenic enzyme expression, meat quality, pig, subcutaneous fat doi: 10.2527/jas.2009-2091

This study investigates the effects of age/weight and castration on the fatty acid composition and the qualities of pork and pork fat. Thirty hybrid male pigs (50% Meishan x 50% Large White) were used. Fifteen were castrated within the first two days of age and the other fifteen remained entire. At 12 weeks of age, the pigs were divided into three groups, each consisting of five castrates and five boars. Animals were fed a basic standard commercial pelleted diet for 30,60 or 90 days and then slaughtered, so that the actual age of the pigs at slaughter was 114, 144 and 174 days respectively. Parameters considered for carcass quality were carcass weight, initial pH (pH45) and ultimate (final) pH (pHu), and P2 backfat thickness. For pork and pork fat qualities, the following parameters were considered: backfat firmness, slip point, sensory attributes and adipose tissue fatty acid composition. Increasing age/weight significantly increased carcass weight and P2 backfat thickness (P Key words: pigs, backfat, fatty acids, castration, quality, INTRODUCTION Meat and meat product qualities can be seriously affected by the fatty acid composition of the muscle and adipose tissues. The composition and quality of fat in pigs can [...]

The use of frozen semen in the swine industry is limited by problems with viability and fertility compared with liquid semen. Part of the reduction in sperm motility and fertility associated with cryopreservation may be due to oxidative damage from excessive or inappropriate formation of reactive oxygen species (ROS). Chemiluminescence measurements of ROS are not possible in live cells and are problematic because of poor specificity. An alternative approach, flow cytometry, was developed to identify viable boar sperm containing ROS utilizing the dyes hydroethidine and 2', 7'-dichlorodihydrofluorescein diacetate as oxidizable substrates and impermeant DNA dyes to exclude dead sperm. The percentage of sperm with high mitochondrial transmembrane potential was determined by flow cytometry using the mitochondrial probe 5, 5', 6, 6'-tetrachloro-1, 1', 3, 3'-tetraethylbenzimidazolylcarbocyanine iodide with propidium iodide staining to exclude nonviable cells. Sperm were incubated with and without ROS generators and free radical scavengers. Basal ROS formation was low (less than 4%) and did not differ (P = 0.26) between viable fresh and frozen-thawed boar sperm. In addition, fresh and frozen-thawed viable sperm were equally susceptible (P = 0.20) to intracellular formation of ROS produced by xanthine/ xanthine oxidase (94.4 and 87.9% of sperm, respectively). Menadione increased (P < 0.05) ROS formation, decreased (P < 0.05) JC-1-aggregate fluorescence intensity, and decreased (P < 0.05) motion variables by 25 to 60%. The mechanism of inhibition of motility by ROS formation may be related to a decrease in mitochondrial charge potential below a critical threshold. Catalase and superoxide dismutase treatment in the presence of xanthine/xanthine oxidase indicated that hydrogen peroxide was the primary intracellular ROS measured. Further, catalase, but not superoxide dismutase, was capable of attenuating ROS-induced inhibition of motility. Whereas basal intracellular hydrogen peroxide formation was low in viable fresh and frozen-thawed boar sperm, both were quite susceptible to external sources of hydrogen peroxide. Key words: 5, 5', 6, 6'-tetrachloro-1, 1', 3, 3'-tetraethylbenzimidazolylcarbocyanine iodide, cryopreservation, flow cytometry, hydroethidine, motility

In pork production, the efficiency of dietary protein (AA) use is low, resulting in urinary excretion of large quantities of nitrogen as urea. Use of AA and formation of urea are under enzymatic regulation, suggesting genetic regulation. The current study examined the effects of sire line, sire, and sex on growth characteristics and plasma urea nitrogen (PUN) concentrations in the offspring of 11 Duroc sires and 11 Landrace sires bred to Yorkshire-Landrace dams. Plasma samples were obtained at approximately 107 (age class = 107 d), 128 (age class = 128 d), and 149 (age class = 149 d) d of age from 511 boars, gilts, and barrows group-penned and fed standard finishing diets. Body weight and backfat (BF, mean of 3 measurements) were recorded at the time of blood sample collection. Sex, age class, and their interaction influenced (P < 0.01) BW, BF, and PUN. Predicted traits (i.e., ADG, BW at 21 wk, average daily change in BF, BF at 21 wk, and the mean of 3 PUN measures) were generated. Means ([+ or -] SD) were: ADG, 888 [+ or -] 204 g; BW at 21 wk, 94.2 [+ or -] 12.5 kg; average daily change in BF, 0.083 [+ or -] 0.052 mm; BF at 21 wk, 13.8 [+ or -] 3.0 mm; and the mean of 3 PUN measures, 16.2 [+ or -] 4.4 mg/dL. Predicted weight traits were influenced (P < 0.05) by sire line, and sex influenced (P < 0.01) all predicted traits. Heritability estimates for PUN at 107, 128, and 149 d of age were 0.35 [+ or -] 0.15, 0.21 [+ or -] 0.13, and 0.16 [+ or -] 0.12, respectively. Phenotypic correlations of PUN with growth and fat traits were low. Genetic correlations of PUN measured at 107 d with growth and fat traits were low. However, genetic correlations of PUN measured at 128 or 149 d with growth and fat traits ranged from 0.81 to 0.95. Determination of PUN, as herein, may be of sufficient precision to allow its use in a selection protocol. Selection of pigs with superior growth performance and low PUN may result in a greater efficiency of dietary nitrogen use and a reduced negative environmental impact. Key words: genetic influence, growth, plasma urea nitrogen

Reproductive efficiency depends on detection of estrus, which may be influenced by housing and boar exposure. This experiment investigated the effects of housing system and boar contact on measures of estrus in weaned sows. Mixed-parity sows were randomly assigned to be weaned into gestation crates away from boars (AWC, n = 45), into pens away from boars (AWP, n = 42), or into pens adjacent to a mature boar (ADJ, n = 46). Estrus detection was initiated at approximately 0700 (0 h) and again at 0.25-, 0.5-, 1-, 2-, 4-, and 8-h intervals beginning on d 4 and continuing through d 7 following weaning. Estrus detection involved observation of the standing response after application of nose-to-nose boar exposure, backpressure, and side rubbing. For the AWC sows, a mature boar was moved to the front of the crates for a 10-min period and then removed. Sows housed in AWP were moved approximately 15 m to an empty pen adjacent to a mature boar for a 10min period, and then returned to their pen. Sows housed ADJ were not moved and estrus detection was performed in their home pen for a 10-min period. The proportion of sows expressing estrus within 7 d from weaning was lowest for ADJ (80%, 37/46) compared with AWP (98%, 41/42) and AWC (96%, 43/45; P < 0.05). There was an effect of interval from weaning to estrus on the percentage of sows expressing estrus, but there was no interaction with treatment. Sows in AWC and AWP (4.7 d) had decreased (P = 0.01) intervals from weaning to estrus compared with ADJ (5.2 d). The duration of estrus was also shorter (P < 0.001) for ADJ (45 h) compared with AWC (58 h) or AWP (62 h). There was a treatment x interval x day of estrus effect for the percentage of sows expressing estrus. After detection of the first standing response on the first day of estrus, only 62 to 82% of sows were detected standing over the next 2 h for all treatments. However, at 4 to 8 h, this increased to 85 to 98% for the AWC and AWP sows, but Key Words: Boar Exposure, Crates, Estrus, Housing, Pens, Sows

Crossbred progeny sired by either Duroc or Pietrain boars, normal for the ryanodine receptor gene, were evaluated for carcass composition and meat quality. Boars from each breed were mated to Yorkshire or [F.sub.1] Yorkshire-Landrace females. A total of 162 offspring was evaluated for carcass and meat quality traits at a common age (approximately 26 wk of age). Duroc-sired progeny had heavier (108.0 vs. 103.0 kg, P < 0.001) and longer carcasses (86.9 vs. 84.8 cm, P < 0.01), whereas Pietrain-sired pigs had less backfat at the first rib (44.6 vs. 47.7 mm, P < 0.01), last lumbar vertebrae (20.9 vs. 23.0 mm, P < 0.05), and 10th rib (23.0 vs. 25.5 mm, P < 0.01). No difference between Pietrain and Duroc progeny was detected for fat depth at the last rib (27.8 vs. 28.8 mm, respectively). Pietrain progeny had a higher percentage of lean at slaughter (52.6 vs. 50.7, P < 0.05) and higher dressing percentage (74.0 vs. 73.1, P < 0.01). Primal cut weights were collected with Pietrain progeny having a greater percentage of carcass as ham (23.0 vs. 22.4, P < 0.01) and loin (21.6 vs. 21.2, P < 0.05), whereas Duroc progeny had a higher percentage of belly weight (12.0 vs. 11.7, P < 0.05). Percentages of Boston butt (8.8 vs. 9.0) and picnic shoulder (9.9 vs. 9.9) were similar for Duroc vs. Pietrain progeny. Total weight of these five primal cuts, as a percentage of carcass weight, was higher for Pietrain progeny (75.2 vs. 74.3, P < 0.01). With heavier carcass weight, Duroc progeny had greater primal cut weights as a function of age. Subjective meat quality scores for color, marbling, and firmness (1 to 5 scale) were more favorable for Duroc-sired progeny. Furthermore, chops from Duroc progeny had higher 24-h pH (5.53 vs. 5.48, P < 0.001) and Minolta a * (17.33 vs. 17.04, P < 0.05) with less percentage drip loss (2.88 vs. 3.80, P < 0.001). No differences were detected between Duroc- and Pietrain-sired progeny for Minolta L * (54.77 vs. 55.37) or b * (7.58 vs. 7.58) objective color scores, percentage cooking loss (28.63 vs. 29.23), or Warner-Bratzler shear force (6.94 vs. 7.11 kg). Both sire breeds have beneficial traits that can be utilized in commercial pork production and merit further study. Key Words: Breeds, Carcass Composition, Meat Quality, Pigs

The effect of boar exposure during artificial insemination (AI) on semen backflow, fertilization, and embryo quality was evaluated. Gilts (~170 d) were induced into estrus with PG600, and ovulation was synchronized using hCG 72 h later. Estrus detection was initiated after PG600 and continued at 12-h intervals. At estrus, gilts were allotted to receive boar exposure (BE, n = 20) or no boar exposure (NBE, n = 20) during AI. Gilts receiving NBE were identified to be in estrus prior to AI and the boar was then removed for 1 h, whereas gilts in the BE group received 15 min of exposure during AI. Insemination occurred in crates at 12 and 24 h after onset of estrus with 3 x [10.sup.9] sperm/80 mL. Backflow was collected continuously with samples taken at time 0, (during AI), and at 0.25, 0.5, 0.75, 1, 2, 4, and 8 h after first and second AI. The effect of treatment was evaluated for time of insemination (min), backflow (mL), and sperm in backflow samples. Oviducts were flushed 2 d after first AI to evaluate the effect of treatment on fertilization rate, accessory sperm numbers on embryos (scored 1 to 5), and embryo quality. There was no effect of first or second AI; therefore, data were pooled. Average duration of AI was 3.7 [+ or -] 0.2 min and was not influenced by BE (P < 0.10). However, during the initial stage of AI, BE reduced the volume of semen (18.6 vs 32.4 [+ or -] 3 mL) and the number of sperm lost (0.8 vs 1.3 [+ or -] 0.15 x [10.sup.9] sperm) compared to NBE (P < 0.05). There was a treatment x time effect (P < 0.05) for volume of backflow. By 45 min, the BE gilts lost more volume (9.0 vs 3.6 mL) compared to the NBE group, but sperm loss did not differ. Between 1 and 8 h after AI, neither volume nor sperm loss was influenced by treatment. By 8 h, total leakage (65 vs 63 mL) and total sperm loss (1.6 x [10.sup.9] vs 1.8 X [10.sup.9] sperm) were not influenced by BE (P > 0.10). However, more accessory sperm (P < 0.01) were found on embryos for the NBE ([greater than or equal to] 11 sperm/embryo) compared to BE embryos ([less than or equal to] 10 sperm/embryo). Despite this observation, percentages of fertilized embryos (99.5 [+ or -] 0.5 %) and number of embryos (11.5 [+ or -] 0.1) were not different (P > 0.10). In conclusion, AI in the presence of a mature boar did not affect total semen leakage, sperm loss, fertilized embryos, or embryo quality. The importance of boar exposure during insemination was evident from less leakage during insemination, but had no effect on fertility; this suggests that the elimination of boar exposure during AI may not be deleterious to reproductive performance. Key Words: Artificial Insemination, Boars, Fertilization, Gilts, Pigs, Semen

In weaned sows, reduced reproductive performance can result from failure or delayed return to estrus or improper timing of insemination. This experiment evaluated the effect of increased frequency of boar exposure and adjusted mating times on reproductive performance. Sows of mixed parity were weaned ~18.7 d after parturition and allotted by genotype, parity, and lactation length to boar exposure frequency of once daily (1X, n = 66), twice daily every 12 h (2X, n = 61), or three times daily exposure at 8-h intervals (3X, n = 60). Sows were weaned into crates and boar exposure was initiated 3 d after weaning. Once estrus was detected, ultrasound was performed every 8 h to determine time of ovulation. All sows were artificially inseminated twice in the 1X group at 0 and 24 h, in the 2X group at 12 and 24 h, and in the 3X group at 16 and 32 h after onset of estrus. The weaning-to-estrus interval was not influenced by treatment and averaged 4.5 d. The percentage of sows expressing estrus in 8 d was higher (P < 0.05) for 1X (97.3%) compared with 2X (92.8%) but not the 3X group (94.0%). The percentage of sows ovulating after estrus was not influenced by treatment (P > 0.10) and averaged 96.5%. Estrus-to-ovulation interval was not affected by treatment (44.7 h) but was influenced by weaning-to-estrus interval (P < 0.0001). Length of estrus was influenced by treatment (P < 0.001), with estrus in the 1X (46.6 h) shorter than in the 2X (60.0 h) and 3X (67.0 h) treatments, and also by weaning-to-estrus interval (P < 0.001). The percentage of first inseminations occurring within 24 h before ovulation was increased (P < 0.001) in the 2X (62%) and 3X (66%) groups compared with the 1X group (28%) and was also influenced by parity (P < 0.001) and weaning-to-estrus interval (P < 0.05). The percentage of second services within 24 h before ovulation was not increased by any factor and averaged 78%. Farrowing rates were not increased (P > 0.10) for 2X (87.2%) and 3X (83.1%) treatments compared with 1X (75.0%). Total pigs born was also not affected by treatment, although 2X (11.2) and 3X (10.7) numbers were greater than 1X (10.0). It appears that once-daily estrus detection combined with delayed mating could achieve optimal reproductive performance. Key Words: Boars, Estrus, Farrowing Rate, Ovulation, Reproduction, Sows

Our objective was to study the effects of housing conditions and the amount of boar contact in a protocol for estrus detection on estrus detection rate, timing of onset of estrus, duration of estrus, and timing of ovulation. After weaning, 130 multiparous sows were assigned to three treatments: HI, in which 52 sows were housed individually in crates and received a high amount of boar contact during estrus detection; HG, in which 52 sows were housed in groups and received a high amount of boar contact; and NI, in which 26 sows were housed individually in crates and received a normal amount of boar contact. Estrus detection was performed every 8 h. For each treatment, the standing response to three levels of stimuli was recorded: a back pressure test (BPT) by a man (man-estrus), presence of a teaser boar (spontaneous-estrus), and BPT in the presence of a teaser boar (boar-estrus). In addition, for HI and HG, the standing response to a fourth level of stimuli was recorded: BPT in a detection-mating area, surrounded by four boar pens (DMA-estrus). To detect ovulation, ultrasonography was performed every 4 h during estrus. Of 117 sows that ovulated, 46% showed man-estrus, 56% spontaneous-estrus, 90% boar-estrus, and 97% DMA-estrus. Mean onset of man-estrus was 107 h (SD 26) after weaning, of spontaneous-estrus was 106 h (SD 22) after weaning, of boar-estrus was 99 h (SD 21) after weaning, and of DMA-estrus was 93 h (SD 22) after weaning. Duration of man-estrus was 22 h (SD 14), of spontaneous-estrus was 29 h (SD 16), of boar-estrus was 42 h (SD 20), and of DMA-estrus was 55 h (SD 18). The high amount of boar contact reduced the number of sows showing man-estrus (P < .05; 41% for HG and HI vs 68% for NI) and reduced duration of boar-estrus (P < .05; 43 h for HG and HI vs 52 h for NI). Duration of DMA-estrus for HG and HI was similar to duration of boar-estrus for NI. Onset of estrus and timing of ovulation were not affected by amount of boar contact. Group housing did not affect detection rate and duration of estrus, but it did postpone average onset of estrus by 10 h, paralleled by a postponement of ovulation. In conclusion, estrus expression is similar at the highest level of stimuli in different protocols for estrus detection. Including higher levels of stimuli in a protocol reduces estrus expression at lower levels of stimuli. This reduction indicates adaptation of sows to a given protocol for estrus detection. Group housing can delay ovulation and related behavioral estrus. Key Words: Sows, Estrus, Ovulation, Boars, Housing

Physiological and behavioral traits of sexually mature boars were compared between episodes of copulation and sexual frustration in order to determine reliable indicators of the differences in emotional states. Ten boars, approximately 6 mo of age, were trained to mount a stationary artificial sow (ArtSow) and to ejaculate when digital pressure was applied to the extended penis. This method of semen collection is the typical procedure of the industry. All 10 boars used in this study were fully trained to this procedure before the onset of the study. Each boar was subjected to trials in which one of the following two treatments was applied. In the control (CTRL) treatment, boars were treated the same as during their training (i.e., allowed to complete ejaculation). In the frustration (FRUS) treatment, boars were allowed to mount the ArtSow, but because no manual pressure was applied to the extended penis, ejaculation never occurred. Blood was collected via indwelling catheters before onset of the trial, during exposure to the ArtSow, and after returning to their home pen. Concentrations of testosterone, cortisol, and (beta)-endorphin were quantified. Behavior of the boars was recorded during exposure to the ArtSow and for 30 min after return to their home pen. Relative to preexposure levels, serum cortisol increased (P < .05) during CTRL exposure and after exposure to both treatments (CTRL; P < .04 and FRUS; P < .06). Serum testosterone did not change during and after either treatment. Serum concentrations of (beta)-endorphin did not change during or after CTRL trials, but serum (beta)-endorphin was greater (P < .05) during FRUS than during CTRL trials. Behavioral analysis revealed that boars spent less time lying down and more time moving about their home pen (P < .05) after a FRUS than after a CTRL trial. In summary, serum cortisol did not allow us to distinguish between the excitement of copulation and the negative affect associated with sexual frustration, whereas increases in serum (beta)-endorphin and motor activity seemed to be indicators of the negative emotional state of sexual frustration in trained boars. Key Words: Boars, Hydrocortisone, Endorphins, Behavior, Stress, Affect

Relationships between blood concentration of FSH and testicular size and daily sperm production were evaluated with data obtained from five studies originally designed to investigate regulation of FSH secretion in Meishan (MS), White composite (WC), and crossbreds of these. A minimum of three blood samples/boar were obtained at greater than 4-d intervals for determination of FSH, and testes were obtained at castration or slaughter. In a random sample of boars, FSH was fivefold greater (P < .01) in MS than in WC boars (n = 22/group). Daily sperm production (DSP)/gram of testis (estimated by counting elongated spermatid nuclei in testicular homogenates) was similar in the groups, but testicular weight (TWT), adjusted for body weight, was less (P < .01) in MS than in WC, yielding lower total daily sperm production (TDSP; P < .05) in MS boars. In four populations (one with MS, one with WC, and two with crossbreds; n = 34 males), boars were selected for extremes in FSH concentrations from larger groups. Across all populations, a threefold greater plasma FSH concentration was associated with a 32% smaller TWT (P < .01). Coincident with increased FSH, TDSP was 33% less (P < .05). In 48 MS x WC boars that were selected for divergence in plasma FSH during pubertal development (4 to 6 mo of age), this divergence was retained at 1 yr (P < .01). Retrospectively, the divergence in FSH was also apparent at 2 and 8 wk of age (P < .05), and the boars with elevated FSH had smaller testicles, lower DSP, and lower TDSP (P < .01). These studies document a negative relationship in mature boars between FSH secretion and testicular size accompanied with decreased TDSP. Key Words: Swine, Testes, FSH

Four experiments were conducted to elucidate the effects of porcine somatotropin (pST, growth hormone) on circulating testosterone concentrations in boars. In Exp. 1, jugular-cannulated obese boars were administered 4 mg recombinant (r) pST/d for 24 d before collection of samples at 15-min intervals over 6 h for measurement of pST, testosterone, and LH. Somatotropin treatment decreased plasma concentrations of testosterone and LH (P < .05). In Exp. 2, White composite boars were administered rpST with imp]ants (4 mg/d) for 10 to 28, 16 to 28, or 22 to 28 wk of age. Reductions in testosterone concentrations were proportional to the length of time rpST was administered; boars treated for 18 wk had the lowest testosterone concentrations. Concentrations of LH declined throughout the study in rpST-implanted boars but remained static in untreated, control boars. In vitro production of testosterone and dehydroepiandrosterone/dehydroepiandrosterone sulfate was unaffected by rpST treatment, and hCG stimulation of in vitro androgen secretion was similar in rpST and control treatments. In Exp. 3, i.v. injection of pituitary pST (USDA-B1; 5 [[micro]gram]/kg BW) into jugular-cannulated White composite and Meishan boars resulted in an acute increase in circulating LH followed by an increase in testosterone concentrations, which then declined to below preinjection levels at 6 to 7 h after pST injection. Multiple injections, two or four per day, of 5 [[micro]gram] pST/kg BW resulted in decreased testosterone concentrations in White composite boars, whereas in Meishan boars testosterone concentrations were unaffected (Exp. 4). Concentrations of LH were not different from control values in either breed, but in both breeds, four injections of pST per day produced lower LH concentrations than did two injections per day (P < .01). Depression of circulating concentrations of androgens in boars requires extended periods of pST treatment. Key Words: Pigs, Somatotropin, Testosterone, Testes

The objectives of this study were to determine whether circulating concentrations of gonadotropins and gonadal hormones of boars were altered as a result of selection of pigs for size of testes or for embryonal survival and(or) number of ovulations. Included in Exp. 1 and 2 were boars with the greatest estimated paired weight of testes (TS) and boars from a control (C) line. Concentrations of FSH were similar (P > .10) in boars from the TS and C lines. In Exp. 3, 4, and 5, circulating concentrations of FSH and 17[Beta]-estradiol ([E.sub.2]) were evaluated in neonates, during pubertal development, and in mature boars of lines selected for an index of number of ovulations and embryonal survival (I), and data were compared to those for boars from a respective C line. Concentrations of [E.sub.2] were not different in boars from the I line and those from the C line during the early neonatal period but were greater (P < .05) in boars of the C line than in those from the I line during pubertal development. Concentrations of FSH were greater (P Key Words: Follicle-Stimulating Hormone, Luteinizing Hormone, Testosterone, Estrogen, Ovulation, Boars

Nine boars were used to evaluate effects of breeding facility design and sexual activity on plasma cortisol concentrations. In one breeding facility (conventional), boars were housed individually in small pens, and female pigs were mated in those boar pens. In another breeding facility (Detection-Mating Area [DMA] system), boars were housed individually in stalls, and female pigs were mated in a specific mating pen adjacent to the front of stalls where boars were housed. After 51 d of housing treatment, a catheter was surgically implanted in the cephalic vein for collection of blood samples. Daytime profiles (hourly collections from 0900 to 1700) of cortisol did not differ among boars in the two treatment groups. Cortisol was greater (P < .01) in the morning than in the afternoon. Administration of ACTH increased (P < .001) plasma cortisol in boars, but breeding facility did not affect the ACTH-induced changes in cortisol concentrations. There was a treatment x time interaction (P < .02) for cortisol after sexual stimulation, and the magnitude and duration of increase in cortisol were greater (P < .05) in the DMA treatment group. Cortisol was greater (P < .001) after than before mating for both treatment groups. An acute increase in plasma cortisol concentration in boars seems to be a normal biological response to sexual activity. However, magnitude and duration of the increase in cortisol may be influenced by breeding facility design and mating procedure. There is no evidence, based on physiological data, that housing boars in stalls in the DMA system has any adverse effects on their welfare. Key Words: Cortisol, Boars, Breeding Facility, Pigs

Body, testis, and epididymis weights were recorded and homogenization-resistant sperm nuclei were counted to determine daily sperm production and the number of sperm stored within the cauda epididymis (CAUDASP) in 145 boars of a control line (C) and 128 boars of a line selected for increased predicted weight of testis (TS) at 150 d of age. Random samples of boars were evaluated at five ages between 70 and 450 d in Generation 8 and 15 ages between 70 and 296 d in Generation 9. Data were analyzed using an animal model that included the fixed effect of line and the linear, quadratic, and cubic effects of age. Variance components were estimated using a DFREML algorithm. Boars of the TS and C line did not differ in body weight (P > .05) in Generation 8. In Generation 9, boars of line TS were heavier between 118 and 198 d of age (P < .001); thereafter, body weights of the lines were similar (P > .05). The increase in organ weights for the testes and epididymides between 70 and 160 d of age were greater (P < .01) for boars of line TS in each generation, and differences between the lines in testis weights established around puberty were maintained at 450 d of age. Daily sperm production and CAUDASP increased more rapidly at younger ages and plateaued at greater values (P < .05) in boars of line TS. At ages less than 200 d, boars of line TS produced more sperm per gram of parenchyma than control boars. Selection for greater predicted weight of paired testes resulted in increased body weight at younger ages, increased daily sperm cell production at all ages, and larger numbers of sperm stored in the cauda epididymis of young boars. Key Words: Boar, Spermatozoa, Selection, Testes

Weights of testes and epididymides, body weight, and morphometric measurements of testicular tissue of 75 boars of a line selected for eight generations for predicted weight of testes at 150 d of age and 75 boars of a randomly selected control line were used to evaluate the effects of selection on testicular development at 70, 100, 130, 160, and 450 d of age (n = 15 boars per line per age). Body weights for boars of the select and control line did not differ (P Key Words: Pigs, Selection, Testes, Seminiferous Tubules, Leydig Cells

Twenty-four Yorkshire boars and six barrows approximately 8 mo of age were used to evaluate the effects of a GnRH agonist (GnRH-A) on circulating concentrations of LH and testosterone (T), concentrations of skatole in fat, and concentrations of 16-androstene steroids in fat and salivary glands. Pigs were assigned to five groups of six pigs each: L200, boars injected with 200 ||micro^gram^ of GnRH-A/kg BW; L50, boars injected with 50 ||micro^gram^ of GnRH-A/kg BW; Boar, boars treated with vehicle; Castrate, males castrated on the same day that Groups 1 to 3 received injections; and Barrow, males castrated as neonates. Pigs in L200, L50, and Boar were only given one injection. Blood samples were taken twice daily from d -2 to 28 for determinations of T and LH concentrations and at 15-min intervals for 6 h on d -1, 1, 7, 14, 21, and 28 for characterization of pulsatile LH release. Pigs were slaughtered on d 30, and samples of backfat and salivary glands were collected for quantification of skatole and 16-androstene steroid concentrations. The LH concentrations increased immediately following GnRH-A injection in L200 and L50 (P |is less than^ .001) and then declined to pretreatment values by approximately 29 h after treatment. Serum T concentrations in L200 and L50 increased after GnRH-A treatment (P |is less than^ .0001) and then decreased to less than pretreatment concentrations by d 5 in L200 (P |is less than^ .001) and by d 8 in L50 (P |is less than^ .01). Concentrations of 16-androstene steroids in fat were less (P |is less than^ .05) in L200 and Barrow than in Boar. Concentrations of 16-androstene steroids in salivary glands were less (P |is less than^ .01) in |L200, L50, Castrate, and Barrow than in Boar. Concentrations of skatole were less than. 12 ||micro^gram^/g of fat in all groups, and no differences were detected in skatole concentrations across the five groups (P |is greater than^ .15). Testicular weights decreased (P |is greater than^ .05) by 48.6% in L200 and 31.9% in L50 by the end of experiment relative to those of Boar. Our results indicate that injecting young mature boars with GnRH-A initially stimulates both LH and T secretion, followed by a reduction in T concentrations to less than pretreatment concentrations. Concentrations of 16-androstene steroids in fat and salivary glands and testicular size also were reduced by GnRH-A treatment.

The hormone GnRH has a stimulatory effect on gonadotropin synthesis and secretion. The objective of the first study was to evaluate concentrations of FSH and LH in plasma of boars after successive treatment with SB75, a GnRH antagonist. Thirteen boars greater than 1 yr of age (eight White Composite [WC] and five Meishan [MS]) were injected once daily with SB75 (10 [micro]g/kg of body weight) for 4 d. Plasma concentrations of LH and testosterone (T) decreased after 1 h from the first dose of SB75. After 12 h of treatment, LH gradually returned to pretreatment concentrations, but T remained suppressed ([is less than] 2 ng/mL) until after the last injection of SB75. There was a modest, but significant, reduction in FSH during treatment with SB75. The prolonged inhibitory effect of SB75 on suppression of plasma T concentrations, in the presence of pretreatment concentrations of LH, implied direct effects of SB75 at the testis. In the second experiment, testicular tissue from adult boars was incubated in the presence of three doses of human chorionic gonadotropin (hCG; 0, .5, and 5 IU) with SB75 (250 ng/mL) or with Deslorelin, a GnRH agonist (500 ng/mL). Samples of media were collected every hour for 3 h, and concentrations of T and estrone (E1) were determined by RIA. Concentrations of T and E1 increased with time in response to treatment with hCG. Co-treatment with SB75 decreased media concentrations of T (P [is less than] .01) and E1 (P [is less than] .03) compared to controls (77.9 vs 85.7 [+ or -] 2.0 and 4.7 vs 5.3 [+ or -] .2 ng/g). In contrast, treatment with Deslorelin had no effect on the amount of T (P [is greater than] .50) or E1 (P [is greater than] .26) released with all dosages of hCG. These results indicate that a GnRH antagonist has a direct effect on the testis, decreasing amounts of T and E1 released from the Leydig cells; however, treatment with a GnRH agonist had no direct effect on release of these gonadal steroids. Thus, it remains unresolved whether the site of action of GnRH antagonist on testicular steroidogenesis is through a testicular GnRH receptor or through some other mechanism. Key Words: Pituitary, Porcine, Testes, Testosterone

Considerable variation exists in the serum levels of gonadotropins in boars; this results in differential testicular function. Boars (Chinese Meishan, European White composite, and crosses of the two breeds) selected for high and low circulating FSH concentrations were used to define possible differences in pituitary sensitivity to GnRH and GnRH antagonist and gonadal and adrenal responses. After a 2-h pretreatment sampling period, boars were injected with GnRH or GnRH antagonist and repetitively sampled via jugular cannula for changes in serum concentrations of FSH, LH, testosterone, and cortisol. In response to varying doses of GnRH or GnRH antagonist, FSH, LH, or testosterone changes were not different in high-or low-FSH boars. Declines in LH after GnRH stimulation were consistently faster in boars selected for high FSH. Chinese Meishan boars had considerably higher cortisol concentrations than White composite boars (132.2 [+ or -] 28.5 vs 67.4 [+ or -] 26.8 ng/mL, respectively; P [is less than] .01). When select high- and low-gonadotropin Meishan: White composite crossbreds were sampled, cortisol levels were elevated but comparable between the two groups (126.5 [+ or -] 13.7 vs 131.4 [+ or -] 13.4 ng/mL, respectively). After GnRH antagonist lowered LH concentrations, administration of hCG resulted in increased testosterone and cortisol concentrations. Although testosterone concentrations remained high for 30 h, cortisol concentrations returned to normal levels within 10 h after hCG injection. The mechanism by which boars selected for high gonadotropins achieve increased levels of LH and FSH may not be due to differences in pituitary sensitivity to GnRH but to differences in clearance from the circulation. Key Words: GnRH, Hydrocortisone, Testes, Testosterone

The experiment tested for the effects of boar exposure and back-pressure during artificial insemination (AI) on semen backflow and embryo quality. Prepubertal gilts (165 d) were given PG600 followed by hCG 72 h later. Fenceline estrous detection was performed in pens every 12 h beginning 24 h after hCG. At estrus, gilts were allotted to receive boar exposure (BE; n=15) or no boar exposure (NB; n=17). Insemination occurred in crates at 12 and 24 h after onset of estrus with 3x[10.sup.9] sperm/80 mL in Modena extender. Uteri were flushed 2 d after AI to evaluate fertilization, accessory sperm, and embryos. Average duration of AI was 3.5 [+ or -] 0.2 min but was not influenced by BE (P>0.1). Backflow of semen was collected at 0 (LK0), 15 (LK15), 30 (LK30), 45 (LK45), 60 (LK60), 120 (LK120), 240 (LK240), and 480 (LK480) min after insemination. At LK0 (during AI) BE allowed less leakage (18 vs 32 [+ or -] 3 mL) and less sperm loss (0.8 vs 1.4 [+ or -] 0.15 x[10.sup.9] sperm) compared to NB (P0.1) between BE and NB. Volume and sperm lost from LK60 to LK480 did not differ. By 8 h, total leakage (65 vs 64 mL) and total sperm lost (1.7x[10.sup.9] vs 1.9x[10.sup.9]) was not influenced by BE (P>0.1). The percentages of pregnant gilts (97%), embryos (11.8), and accessory sperm per egg (7) were not influenced by BE (P>0.1). However, ease of insemination of gilts from BE was noted. There was no effect of treatment on any measured parameter between first or second AI. It was concluded that the sperm concentration used masked the effects of NB and that total leakage was proportional to the volume lost at time of AI, which did not effect fertility. Key Words: Artificial insemination, Gilt, Boar

The reliability of using different in vitro-derived measures of sperm quality to predict boar fertility was examined. On three occasions during a 20-wk period of breeding, special collections of the first sperm-rich fraction of the ejaculate from six boars were carried out. After in vitro capacitation procedures, three dilutions (5 x [10.sup.5], 1.25 x [10.sup.5], and 3.125 x [10.sup.4] sperm/mL) of these semen samples were used in a standardized in vitro fertilization (IVF) test with oocytes recovered from prepubertal slaughterhouse ovaries and matured in vitro. Routine assessments of sperm motility, concentration, and morphology were also carried out for all collections used for AI during the 20-wk period. Semen from the same ejaculate, processed according to normal commercial practice using the AndroHEP extender, was used to inseminate equal numbers of recently weaned sows with either 3 x [10.sup.9] or 2 x [10.sup.9] total sperm, three times during the estrous period. Data from a total of 444 sows were used to determine boar fertility; between 12 and 54 sows were bred with each semen dose across the six boars. All measures of sperm fertilizing ability in vitro were different among boars (all P < .05) and use of different semen dilutions for IVF allowed further discrimination of apparent sperm quality among boars. The laboratory evaluation of semen collected during the period of breeding indicated effects of boar on ejaculate volume, total number of sperm per ejaculate, motility, and the percentage of sperm with normal morphology (all P < .01). Sperm dose used in AI had no effect on farrowing rate (80.7 vs 81.5%), but the lower AI dose resulted in a reduction (P < .05) in total numbers born (10.8 vs 10.0). For all three semen dilutions, estimated potential embryo production rate accounted for up to 70% of the variation in litter size obtained with 3 x [10.sup.9] sperm per AI dose, and the number of sperm attached per oocyte was a major factor accounting for variation in litter size obtained with 2 x [10.sup.9] sperm per AI dose. These IVF variables may, therefore, be effective indicators of boar sperm quality for use in AI. With 2 x [10.sup.9] sperm per AI dose, the percentage of sperm with normal morphology also explained a large part of the variance in litter size born ([R.sup.2] = .59), indicating that morphological characteristics are a useful measure of semen quality. Key Words: In Vitro Fertilization, Semen, Boars, Fertility