Reproductive productivity measurements in Japanese swine breeding herds

Ovarian Follicle Growth during Lactation Determines the Reproductive Performance of Weaned Sows

Simple Summary

In this field study, the ovaries of weaned (n = 191, experiment 1) and lactating (n = 40, experiment 2) sows were transrectally scanned to measure the diameter of the follicles. Both the weaned and lactating sows showed great variability in the diameter of the ovarian follicles, indicating that the variability at weaning already existed during early lactation and was carried over to weaning. Sows with small follicles at weaning showed low reproductive performance and were more frequent among those with fewer farrowings and those weaned in summer–autumn.

Abstract

Factors causing variability in ovarian follicle size among weaned sows are not well known. This field study aimed to disclose influencing factors and evaluate if the differences at weaning were established during lactation. Ovaries were scanned using transrectal ultrasound. The first experiment was conducted over a year with 191 randomly chosen sows that were hierarchically grouped (p < 0.001) according to ovarian follicle diameter reached at weaning: Small (0.20–0.30 cm; n = 37), medium (0.31–0.39 cm; n = 75), and large (0.40-1.00 cm; n = 69). Sows with small follicles showed a higher incidence of post-weaning anestrus (p < 0.01), longer wean-to-estrus/ovulation intervals (p < 0.01) and farrowing smaller litters (p < 0.05). Ovaries with small follicles were more common among sows weaned in summer–autumn than in winter–spring (p < 0.01) and among sows of lower parity (1–3) (p < 0.05). In the second experiment, with 40 sows randomly chosen at farrowing, the ovaries were scanned at 7, 14, and 21 d post-partum. Sows showed great variability in ovarian follicular size during lactation with a consistent relationship between the three measurement times (r = 0.84, p < 0.01). Follicle size was smaller in sows nursing in summer–autumn than in winter–spring (p < 0.05). In conclusion, early lactation dictates the great variability in ovarian follicular diameter at weaning shown by sows. Sows with smaller follicles at weaning had longer intervals for estrus and ovulation and smaller litters at farrowing and they were in greater numbers among sows weaned during the summer and fall and among those with fewer previous farrowing.

Genetic Association between Swine Leukocyte Antigen Class II Haplotypes and Reproduction Traits in Microminipigs

The effects of swine leukocyte antigen (SLA) molecules on numerous production and reproduction performance traits have been mainly reported as associations with specific SLA haplotypes that were assigned using serological typing methods. In this study, we intended to clarify the association between SLA class II genes and reproductive traits in a highly inbred population of 187 Microminipigs (MMP), that have eight different types of SLA class II haplotypes. In doing so, we compared the reproductive performances, such as fertility index, gestation period, litter size, and number of stillbirth among SLA class II low resolution haplotypes (Lrs) that were assigned by a polymerase chain reaction-sequence specific primers (PCR-SSP) typing method. Only low resolution haplotypes were used in this study because the eight SLA class II high-resolution haplotypes had been assigned to the 14 parents or the progenitors of the highly inbred MMP herd in a previous publication. The fertility index of dams with Lr-0.13 was significantly lower than that of dams with Lr-0.16, Lr-0.17, Lr-0.18, or Lr-0.37. Dams with Lr-0.23 had significantly smaller litter size at birth than those with Lr-0.17, Lr-0.18, or Lr-0.37. Furthermore, litter size at weaning of dams with Lr-0.23 was also significantly smaller than those dams with Lr-0.16, Lr-0.17, Lr-0.18, or Lr-0.37. The small litter size of dams with Lr-0.23 correlated with the smaller body sizes of these MMPs. These results suggest that SLA class II haplotypes are useful differential genetic markers for further haplotypic and epistatic studies of reproductive traits, selective breeding programs, and improvements in the production and reproduction performances of MMPs.

Gilt development and mating in commercial swine herds with varying reproductive performance

The primary objectives were to improve standard operating procedures for gilt development and mating, based on a comparison of practices among commercial Japanese herds with varying reproductive performance. Questionnaires were sent to 115 herds; the 96 herds (83.5%) responding were classified, on the basis of the upper and lower 25th percentiles of pigs weaned per mated female per year, into high-, intermediate- or low-performing herds. During gilt development, high-performing herds switched to a gilt developer diet at an earlier age than low-performing herds (P < 0.05). More high-performing herds performed first insemination "immediately," with second insemination "6 to 12 h" after first estrus detection than low-performing herds (P < 0.05). However, there were no differences (P > 0.05) among productivity groups with regard to the use of nutritional flushing or percentage of AI used. In multilevel analyses (17,582 service records), gilts in herds using direct boar contact were 13.73 d younger at first mating than those in the herds using indirect boar contact (P < 0.05), but age was not related to feeding practices or the number of days of boar contact per week (P > 0.05). First-serviced gilts in the herds that performed first insemination "immediately" after first estrus detection had an 8.3 to 8.4% higher farrowing rate (FR) than those in herds that performed first insemination at "6 to 12 h" and "24 h" (P < 0.01). Reserviced gilts in the herds with first insemination "immediately" after first estrus detection had 7.5% higher FR than those in herds with first insemination at "6 to 12 h" (P < 0.05). Meanwhile, first-serviced and reserviced gilts in herds that restricted feed after insemination had 0.23 and 0.17 more pigs born alive (PBA) than gilts in the herds that did not restrict feed (P < 0.05). However, PBA was not related to time of insemination (P > 0.05). In conclusion, to improve gilt reproductive performance, we recommend stimulating gilt estrus by using direct boar contact, performing first insemination "immediately" after first estrus detection, and restricting feed intake after insemination.

Double and triple matings associated with reproductive performance in first-serviced and reserviced female pigs in commercial herds

The objective of this study was to investigate associations of the number of matings and services with reproductive performance in high-performing and ordinary herds. The data included 113,265 service and 92,248 farrowing records in 117 herds. A service included single or more matings of a female pig (female) during a 10-day estrus period. Two herd groups were built on the basis of the upper 25th percentile of pigs weaned per mated female per year: high-performing (> or = 22.8 pigs) and ordinary herds. Mixed-effects models were used to analyze reproductive performance. Relative frequencies (%) of single, double and triple or more matings were 3.4, 27.4, and 69.2% in high-performing herds, respectively, and were 4.6, 59.3 and 36.1% in ordinary herds, respectively. Percentages of reserviced females in high-performing and ordinary herds were 7.3 and 13.0%, respectively. Triple or more-mated (TM) gilts had 3.5% higher farrowing rates than double-mated (DM) gilts (P<0.01), but similar pigs born alive (PBA) to DM gilts in the first service group in both the herd groups. In the first service group, TM sows had 0.8% higher farrowing rates and 0.2 more PBA than DM sows in high-performing herds (P<0.01). In the reservice group, TM gilts and TM sows had farrowing rate similar to DM gilts and DM sows in high-performing herds. In conclusion, performing triple matings was a better practice for first-serviced females than performing double matings. Double matings may be sufficient for reserviced females.

By-parity nonproductive days and mating and culling measurements of female pigs in commercial breeding herds

The objectives of this study were to determine by-parity nonproductive female days (NPD or NPDs) and mating and culling measurements, to determine correlations between by-parity NPDs, mating and culling measurements and herd productivity measurements, and to compare by-parity NPDs between three herd groups (105 herds) with differing reproductive productivities. NPD was defined as the number of days when mated females were neither gestating nor lactating. Correlation analysis and mixed-effects models were performed. On the basis of the 25th and 75th percentiles of pigs weaned per mated female per year, three herd groups were formed: high-, intermediate-, and low-performing herds. The mean NPD of 105 breeding herds (mean +/- SEM) was 52.7 +/- 1.6 days. The NPDs in parities 1, 6 and > or = 7 were higher than those in parities 0, 2, 3 and 4 (P<0.05). High-performing herds had a higher farrowing percentage and lower percentage of reserviced females than low-performing herds (P<0.05). Lower by-parity NPDs were correlated with lower percentages of reserviced females, higher farrowing percentages and lower culling rates from parities 1 to 5 (P<0.05). High-performing herds had NPDs that were > 25 days lower in parities 0 to 3 than low-performing herds (P<0.05). High-performing herds had lower culling rates in parities 2 to 5 and higher culling rates in parities 6 and > or = 7 than low-performing herds (P<0.05). The present study indicates that monitoring the by-parity NPD and mating and culling measurements is a good tool for improvement of herd productivity.

An evaluation of the impact of increased lactation length on the reproductive efficiency of sows in commercial herds

The objective of this study was to evaluate the impact of increased lactation length (LL) on the reproductive efficiency of sows in herds that were performing differently. The present study used 69,314 parity records for 38,532 sows in 114 herds. Two herd groups, high-performing herds and other herds, were formed on the basis of the upper 25th percentile of pigs weaned per mated female per year. Reproductive efficiency was measured as the estimated number of pigs born alive per farrowed sow per year (PBASY) and was calculated as actual subsequent pigs born alive (PBA) multiplied by estimated litters per farrowed sow per year (LSY) for each farrowed sow. The estimated LSY was calculated as 365 days divided by the actual farrowing interval. Multilevel linear mixed-effects models were used. In our evaluation, an interaction between LL and the herd groups was found for the estimated PBASY (P<0.05). The estimated PBASY of high-performing herds did not decrease as LL increased (P>0.10), although the estimated PBASY of the other herds decreased by 0.04 pigs as LL increased by 1 day (P<0.05). As LL increased from 14 to 28 days, the estimated LSY decreased by 0.19 in the two herd groups (P<0.05). Furthermore, as LL increased by 1 day, subsequent PBA increased by 0.08 pigs in high-performing herds and increased by 0.04 pigs in the other herds (P<0.05). Increased LL may not decrease the performance of sows in high-performing herds, but it may decrease the performance in other herds.

A repeatability assessment of sows mated 4–6 days after weaning in breeding herds

The objectives of this study were to investigate the associations of weaning-to-first-mating interval (WMI) groups with reproductive performance, to determine the repeatability and the correlation coefficients in WMI groups between consecutive parities, and to investigate factors associated with the proportion of sows having WMI 4-6 days. This study was conducted using 55,690 parity records of 11,991 sows born during 1999 in 94 herds. Five groups of WMI were formed: 0-3, 4-6, 7-20, 21-27, and > or =28 days. The correlation and the repeatability of the WMI groups were determined using correlation analysis and variance component analysis. Mixed-effects models were used to analyze the associations of WMI groups with reproductive performance, and the associations of parity, lactation length (LL), and nursing piglets with the proportion of sows having WMI 4-6 days. The overall proportion of the WMI 4-6 days was 82.3%. Sows with WMI 4-6 days had the highest farrowing rate, and had more pigs born alive than those with WMI 7-20 days (P<0.01). At each farrowed parity, sows with WMI 4-6 days had higher parity at removal than those with WMI 7-20 days (P<0.01). The repeatability of the WMI groups was low (0.08), and the correlation coefficients of WMI groups between consecutive parities were also low (0.10< or = r< or =0.18; P<0.01). More than 85.9% of sows with WMI 4-6 days were mated on 4-6 days postweaning at subsequent parity. Meanwhile, 65.8-83.9% of sows with WMI 0-3 or > or =7 days were also mated on 4-6 days postweaning at subsequent parity. Additionally, sows with parity > or =2, LL 24-28 days, and 9-10 nursing piglets were more likely to have WMI 4-6 days (P<0.01). In conclusion, sows having any WMI were more likely to be mated on 4-6 days postweaning at subsequent parity, and sows mated on 4-6 days had higher reproductive performance and higher longevity. Increased LL may increase the proportion of sows having WMI 4-6 days.

Five-year trends in female pig mortality on commercial breeding farms in Japan

High mortality in female pigs on breeding farms is a critical problem in the U.S. swine industry. The objectives of this study were to determine whether female pig mortality on Japanese commercial farms increased; to investigate correlations between the mortality and herd-management factors, especially herd size and lactation length; and to determine herd repeatability in female pig mortality. A five-year annual measurement data between 1999 and 2003 were abstracted from recording files of 113 farms in Japan. The year-effects on measurements were analyzed by using repeated measures data between 1999 and 2003 in mixed-effects linear models. The annual mortalities for female pigs in 1999, 2000, 2001, 2002 and 2003 were 4.93%, 5.25%, 5.40%, 5.32%, and 4.85%, respectively. The year-effect on the female pig mortality was not found for the five years. Neither herd size, lactation length nor other management factors were found to be consistently correlated with female pig mortality for the five years. The repeatability of the mortality was 36.5% on commercial farms. In conclusion, female pig mortality did not increase during these five years in Japan. Herd size and lactation length were not risk factors for female pig mortality.

Lactational performance for improving postweaning reproductive performance and lifetime performance on swine commercial farms

We studied the associations of the weaning litter weight (WLWt) and number of pigs weaned (PW) with measurements of postweaning reproductive performance and examined the repeatability of WLWt, PW and average pig weight at weaning (PIGWt) on commercial swine farms. This study spanned 6 years and was conducted using 57,611 weaning records from 11,574 sows born in 1999 on 92 farms. Variance components analysis was used to determine the repeatability of measurements of lactational performance. Mixed-effects models were used to analyze the associations of measurements of lactational performance with farrowing rate and weaning-to-first-mating interval. The values for repeatability of WLWt, PIGWt and PW were 0.31, 0.34 and 0.17, respectively. No differences in weaning-to-first-mating intervals were found among the five PW groups (< or = 6, 7 to 8, 9 to 10, 11 and 12 to 14 pigs) or among the three WLWt groups (< or = 48.0, 48.0 to 69.0 and > or = 69.0 kg). Sows with 12 to 14 PW had farrowing rates similar to those with 9 to 11 PW. Sows with a WLWt > or = 69.0 kg had the highest farrowing rate (P<0.01). However, sows with 11 PW had an approximately 100 to 200 g lighter PIGWt than those with 4 to 10 PW (P<0.01). This study suggests that increased WLWt and PW do not impair postweaning reproductive performance, but instead decrease PIGWt.

Effect of PG600 and adjusted mating times on reproductive performance in weaned sows

The administration of PG600 to sows at weaning induces >90% of sows to return to estrus within a week, but farrowing rate and litter size are often not improved. This study evaluated the effects of adjusted artificial insemination (AI) times based on weaning to estrus interval (WEI) and estrus to ovulation interval (EOI) following PG600. All sows were given PG600 at weaning and allotted to adjusted (ADJ, n=47) or non-adjusted (NA, n=46) mating times after the onset of estrus. Adjusted mating involved: (1) 2-3 days WEI, AI at 36 h and 48 h; (2) 4 days WEI, AI at 24h and 36 h; (3) 5 days WEI, AI at 12h and 24h; and (4) 6-7 days WEI, AI at 0 h and 12h. Mating for NA occurred at 0 h and 24h after onset of estrus. There was no effect of treatment on return to estrus (92.9% versus 92.5%) or ovulation (92.7% versus 92.5% for ADJ and NA, respectively). The proportion of first AI occurring within 24h prior to ovulation was increased (83.8% versus 50.0%) and closer to ovulation for ADJ compared to NA treatment (19.4h versus 27.3h, P<0.05). Treatment did not influence (P>0.10) the proportion of second AI occurring within 24h of ovulation (72.8% versus 56.6%) but did influence (P<0.05) the interval from second AI to ovulation for ADJ compared to NA (10.6h versus 3.3h). The ADJ treatment increased (P<0.05) the proportion of sows that received an AI within 24h before ovulation (98.8% versus 87.0%). However, treatment did not influence pregnancy (87.4%) or farrowing (79.5%) rates but the NA treatment tended to increase (P<0.10) total number of pigs born (11.8 versus 8.9). In conclusion, while AI times for ADJ appeared to occur within optimal periods, farrowing rates were not improved and litter size decreased, suggesting that two AI at 12h intervals and closer to the time of ovulation may be detrimental. Overall, these data suggest that for sows injected with PG600 at weaning and receiving two AI, breeding at 0 h and 24h after onset of estrus is recommended.