An analysis of survey data by size of the breeding herd for the reproductive management practices of North American sow farms.

A survey was performed to assess whether reproductive management differed among small-sized (Sm, <500 sows), medium-sized (M, 501 to 2,000 sows), and large-sized (Lg, 2,001 to 8,000 sows) farms (n=113). Farms with 501 to 4000 sows/barn were most frequent with sows kept in stalls on 90% of farms. More Lg farms (P<0.05) functioned as breed to wean and more Sm and M as farrow to finish. More Sm and Lg farms weaned at >21 d, whereas M farms were more likely to wean at 18 to 21 d (P<0.05). More Lg farms had farrowing rates above 89% than Sm and M farms (P<0.05), and culling rates above 40% were more frequent on M and Lg farms than on S. On M and Lg farms, sows were bred in larger batches, using lower person to sow ratios, and with more people required than on Sm farms (P<0.05). More (P<0.05) M and Lg farms spent time moving sows and on records, but hours devoted to estrous detection, breeding, and other tasks did not differ among farms (P>0.10). More M and Lg farms used more boars for estrus detection, rotated boars, and controlled boar movement than Sm farms (P<0.05). Farm size also influenced semen sourcing, number of doses received, and frequency of semen delivery (P<0.05). More M and Lg farms performed AI in the presence of a boar, left the AI rod in after AI, checked for returns, and diagnosed pregnancy than Sm farms (P<0.05). Start of boar exposure after weaning began on 69% of farms within 2 d, occurring most often in the AM, but with exposure times varying from 1 to 5 min/sow. Semen was thermally protected for 50% of farms receiving shipments, and semen storage was consistent among farms. For AI, service occurred within minutes to hours after detection of estrus on 61% of farms. During AI, procedures such as back-pressure were required, whereas techniques such as hands-free AI were prohibited on most farms. Sow movement was allowed only once at 4 wk after breeding on 50% of farms, and pregnancy diagnosis occurred at 3 to 5 wk on 78% of farms. Most sows were allowed ≥1 chance for breeding after conception failure before culling. Incidence of fail to farrow was <5% and litter size was 10 to 13 pigs on >82% of farms. Summer infertility was observed on 69% of farms with estrus and pregnancy failures the leading causes. Over 70% of farms reported a technician effect on fertility. These results suggest that reproductive management of farms in key areas related to weaning, breeding, gestation, and labor use could be a source of variation in reproductive performance.

Fertility of semen used in commercial production and the impact of sperm numbers and bacterial counts.

The objective was to monitor sperm counts and bacterial presence on randomly pooled semen doses over 3y and to determine effects on the farrowing rate and total born in two large farm systems, each serviced by their own boar stud. Sperm counts were divided into increments of 0.5x10(9) for data analysis. There was no effect of sperm count or the presence of bacteria on farrowing rate (n=9502 observations). Furthermore, based on 7311 observations, there was no effect of the mere presence of bacteria on total born, but sperm count had a significant effect on total born; in particular, total born decreased with pooled semen doses <2.5x10(9) sperm.

An evaluation of three methods for assessing sexual behavior in boars.

This study used three separate methods to evaluate sexual behavior in boars previously classified as having high (H), intermediate (INT), or low (L) levels of sexual behavior. Boars were initially evaluated for sexual behavior at 9.6 to 10.6 mo of age with a tethered female for 5 min. Boars were subsequently evaluated with a tethered female for 10 min (TF), a group of females for 10 min (FG), or continuously in a cohabitation environment for 113 h (C). When boars were evaluated with the TF procedure they mounted the female in less time (P < .01) and copulated sooner (P < .01) than when evaluated with the FG procedure. Regardless of whether the TF or FG procedure was used, L boars cumulated less time (P < .01) nosing the sides of females and took longer (P < .01) to first mount than H or INT boars. Proportion of successful matings was not different between the TF and FG procedure; however, the proportion of successful matings by H (91.7%), INT (79.2%), and L (45.8%) boars did differ (P < .001). With the C procedure, sexual behavior classification affected (P < .01) average number of successful matings (H, 4.7; INT, 2.3; and L, .33). This study indicates that sexual behavior traits expressed by a boar are similar when evaluated with a tethered female, a group of females, or a cohabitation environment.

The effect of breeding facility and sexual stimulation on plasma cortisol in 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.

Mating management.

The mating management of pigs is conducted under a wide spectrum of management techniques because females are variously hand-mated, pen-mated, or artificially inseminated. Factors that may affect the onset of estrus when hand-mating are boar exposure, method of housing females after weaning, season, type of facilities, and parity. The expression of sexual behavior in both male and female pigs can be influenced by a variety of physiologic, psychological, and environmental factors. To optimize the efficiency of estrous detection, females should not receive boar stimuli just prior to estrous detection when either hand-mated or artificially inseminated. When females are pen-mated, management procedures need to be employed to prevent an excessive number of estrous females from accumulating, which leads to a decrease in boar fertility.

The influence of androgenic and estrogenic hormones on sexual behavior in castrated adult male pigs.

The objectives of these studies were to evaluate the influence of testosterone propionate (TP), estradiol cypionate (EC), dihydrotestosterone propionate (DHTP), EC + TP, EC + DHTP, and TP + DHTP on traits of masculine sexual behavior in castrated adult male pigs of different breeds. Masculine sexual behavior was restored and maintained by TP, whereas EC initially activated sexual behavior, including copulation and ejaculation, but was unable to sustain copulatory behavior for the 8- to 18-week periods that were evaluated. Treatment with DHTP was ineffective for stimulation of sexual behavior; thus, it is suggested that testosterone promotes some aspects of masculine sexual behavior in male pigs via aromatization to estrogen, but both androgen and estrogen are required for maintenance of the full complement of masculine sexual behavior traits.

Characterization of summer infertility of sows in large confinement units.

Data were from 3119 farrowings in three large swine confinement units in eastern North Carolina. Litters were weaned during April through October. Interval to first estrus after weaning was greater during June through September than during other months. The two-way interactions among farm unit, parity and month weaned all affected weaning-to-estrus interval. Conception rate at first estrus was lower for primiparous than for multiparous sows and declined from April through July. Conception rate at first estrus was affected by farm by parity interaction. Weaning-to-conception interval was longer for primiparous than multiparous sows and was longer during June through October. Weaning-to-conception interval was affected by interactions of unit with parity and unit with month weaned. Total pigs farrowed at the subsequent farrowing was affected by unit, parity, length of the previous lactation and the unit x parity interaction. Overall, reproductive performance varied among farm units, was lower in primiparous than in multiparous sows and was reduced during June through October.

Effect of altering suckling intervals of early-weaned pigs on rebreeding performance of sows.

Sows on two commerical farms were assigned to have their pigs weaned after a 3-week lactation (control, n=160) or after a 3-week lactation that included a 48-hr period of interrupted nursing before weaning (altered-suckling, n=122). Sows in the altered-suckling groups were paired, and each member of a pair was separated from both litters during the alternate 12-hr periods. Thus during the final 48 hr before weaning, each sow in the altered-suckling group had two 12-hr periods when no litters were present and two 12-hr periods when two litters were present. On farm 1, interval from weaning to estrus was 12.8 +/- 0.8 days for control sows compared to 8.4 +/- 1.0 days for sows in the altered-suckling group (P<.01). On farm 2, interval from weaning to estrus did not differ between sows in the control group and those in the altered-suckling group (6.2 vs 6.1 days, P>.05). Thus altered-suckling was effective in reducing the interval from weaning to estrus only when the normal rebreeding interval was prolonged (farm 1). Conception rates at first breeding and subsequent litter sizes did not differ between treatments. Altered-suckling may improve reproductive performance of sows in situations where prolonged postweaning anestrus is a problem.