Within-farm variability in age structure of breeding-female pigs and reproductive performance on commercial swine breeding farms

Repeat offenders: PRRSV-2 clinical re-breaks from a whole genome perspective

Clinical re-breaks of PRRSV on sow farms are a frustrating reality for producers and practitioners. The underlying mechanisms allowing for a single viral variant to persist and cause repeated clinical outbreaks within a herd that should have strong immunity, through recent exposure to a highly similar genetic variant (≥%97 homology), are poorly understood. This study systematically identified clinical re-breaks on sow farms and performed whole genome sequencing on viral isolates available from each outbreak event to evaluate the hypothesis that such re-breaks may be associated with evolution on glycoprotein ectodomains. Pairwise comparisons between re-break isolates revealed multiple amino acid sites in structural proteins that frequently differed between re-break pairs. For sites identified on GP5, several sites were found to be changed in a higher proportion of re-breaks than expected from background variability. Intriguingly, 4 of 13 re-break events had no changes on GP5 but numerous changes in other structural protein ectodomains; GP2, E, GP3, and GP4 all contained several sites that were substituted in a high proportion of rebreak pairs, highlighting the multigenic nature of immune evasion. Across all structural proteins, most sites were located on ectodomains (15/22; 68 %). Several GP5 sites (6/8; 75 %) have been associated with escape from antibody neutralization in in vivo and in vitro experiments. To conclude, identification of suspected immune escape events from production and surveillance data resulted in detection of crucial amino acid positions on structural proteins that potentially underly antigenic diversity. Such micro-evolutionary change could result in escape from antibody neutralization, complicating interventions such as herd closures and leading to persistence of clinical outbreaks on sow farms.

The impact of herd age structure on the performance of commercial sow-breeding farms

BACKGROUND

The herd age structure, i.e., distribution of sows within a farm based on their parity number, and its management are essential to optimizing farm reproductive efficiency. The objective of this study is to define different types of herd age structure using data from 623 Spanish commercial sow farms. Additionally, this study aims to determine which type of herd age structure can enhance reproductive efficiency at the farm level.

RESULTS

Farms are classified into three groups according to the quadratic function fitted to the percentage of sows by parities. This classification unveils three types of herd structures: type 1 (HS1) exhibits a concave-downward trend, with a higher percentage of sows in intermediate parities (mean of 45.5% sows between the 3rd to 5th parity); type 2 (HS2) presents a trend curve that is close to a straight line, with a gradual decrease in the percentage of sows per parity (approximately 2% loss of sows census per parity); and type 3 (HS3) shows an upward concave trend curve, with an increase in the percentage of sows in later parities (19.0% of sows between 7th and ≥ 8th parity). Parametric tests assess productivity differences between the three types of herd structures (p < 0.01). HS1 farms have the best productive outcomes over a year, with 31.2 piglets weaned per sow and year (PWSY) and a farrowing rate of 87%, surpassing HS2 and HS3 farms (30.1 and 28.7 PWSY; 85.3% and 83.4% farrowing rates, respectively). HS1 also have the lowest percentage of sows returning to oestrus (11.8%) and the highest number of weaned piglets per litter (12.8), compared to HS2 (13.2% and 12.4 piglets weaned) and HS3 (15.1%, 11.9 piglets weaned). These differences show a medium effect size (η2 between 0.06 to < 0.14).

CONCLUSIONS

This study shows the importance of herd age structure on sow-breeding farms as a factor of reproductive efficiency. The results endorse the proposed classification based on the curvature of the trend parabola obtained with the quadratic function to categorize herd structures into three groups. Additionally, these findings highlight the importance of considering the herd age structure in farm decision-making.

Factors for improving reproductive performance of sows and herd productivity in commercial breeding herds

We review critical factors associated with reproductive performance of female breeding pigs, their lifetime performance and herd productivity in commercial herds. The factors include both sow-level and herd-level factors. High risk sow-level groups for decreasing reproductive performance of female pigs are low or high parity, increased outdoor temperature, decreased lactation feed intake, single inseminations, increased lactation length, prolonged weaning-to-first-mating interval, low birth weight or low preweaning growth rate, a few pigs born alive at parity 1, an increased number of stillborn piglets, foster-in or nurse sow practices and low or high age at first-mating. Also, returned female pigs are at risk having a recurrence of returning to estrus, and female pigs around farrowing are more at risk of dying. Herd-level risk groups include female pigs being fed in low efficiency breeding herds, late insemination timing, high within-herd variability in pig flow, limited numbers of farrowing spaces and fluctuating age structure. To maximize the reproductive potential of female pigs, producers are recommended to closely monitor females in these high-risk groups and improve herd management. Additionally, herd management and performance measurements in high-performing herds should be targeted.

Female lifetime productivity in a swine integration system using segregated gilt development units

This study evaluated female lifetime productivity in a swine integration system of Brazil that combines segregated gilt development units called fourth sites (4S) and sow farms (SF). Records of 5,013 culled females from 3 4S and 10 SF were evaluated. The most frequent culling reasons were locomotor problems, in 4S, and litter performance, in SF. Days in herd at culling were 71.8 ± 0.8 in 4S. In SF, parity at culling was 4.4 ± 0.1; the lowest number of pigs born during lifetime (33.5 ± 1.1) was for females culled due to reproductive failures and the lowest number of pigs born per year of lifetime (22.8 ± 0.3) was for sows culled due to litter performance (P < 0.05).

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.

Animal-related factors associated with piglet mortality in a bedded, group-farrowing system

Li, Y. Z., Anderson, J. E. and Johnston, L. J. 2012. Animal-related factors associated with piglet mortality in a bedded, group-farrowing system. Can. J. Anim. Sci. 92: 11–20. To understand pre-weaning mortality of piglets in a bedded, group-farrowing system, associations with sow parity, mortality of piglets during the first 24 h after birth, farrowing behavior, cross-fostering, birth weight and gender of piglets were investigated. Sows (n=169, parity 1 to 10) from eight contemporary groups were evaluated. Litter size at birth, dead piglets from birth to weaning, and individual weight of piglets at birth and weaning (27±2.6 d) were recorded. Behavior of 46 focal sows during farrowing was video-recorded. Piglet mortality within litter increased (P<0.001) with increasing parity. Piglets that died before weaning were lighter (P<0.001) at birth than weaned piglets. Mortality of pigs during the first 24 h postpartum was correlated positively with pre-weaning mortality within litter (R2=0.34; P<0.001). Farrowing behaviors were not associated with piglet mortality, and were not different among sows of different parities, or between sows with and without 24 h piglet mortality. Gender of piglets and cross-fostering did not affect piglet mortality. Results indicate that parity, 24 h mortality, and birth weight of piglets were the major animal-related factors associated with piglet mortality in the loose farrowing system studied.

Associations between age of gilts at first mating and lifetime performance or culling risk in commercial herds

Age of gilts at first mating (AFM) is a factor associated with reproductive performance of female pigs. The objectives of the present study were to compare AFM and reproductive performance across parity between three herd groups based on a productivity measurement and to determine lifetime performance by AFM and the herd groups. The female data included 38,212 mated gilts entered between 2001 and 2003, and the herd data included mean measurements from 2001 to 2006 in 101 herds. The average female inventory of the 101 herds was 370.2 females. Females were categorized into five groups: AFM 188-208, 209-229, 230-250, 251-271 or 272-365 days. Three herd groups were formed on the basis of the upper and lower 25th percentiles of pigs weaned per mated female over six years: high-, intermediate- and low-performing herds. Multilevel mixed-effects models were performed to analyze comparisons. The AFMs (± SEM) in the high-, intermediate- and low-performing herds were 239.5 ± 0.22, 247.4 ± 0.21 and 256.7 ± 0.35 days, respectively. As the AFM increased from 209-229 to 272-365 days, annualized lifetime pigs born alive (PBA) decreased from 18.2 to 15.3 pigs, and the number of parities at removal decreased from 4.8 to 4.1 (P<0.05). In parity 1, females with an AFM of 209-229 days had fewer PBA, but had a lower culling risk and shorter weaning-to-first mating interval than those with an AFM of 251-271 days (P<0.05). In conclusion, we recommend management practices such as boar exposure to hasten puberty in gilts and decrease AFM.

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.

Six component intervals of nonproductive days by breeding-female pigs on commercial farms

Of 105 swine herds using a production record system for breeding female pigs, 95 farms were used to analyze nonproductive female days (NPD), the six component intervals of NPD, and related measurements. The NPD was defined as the days when mated gilts and sows were neither gestating nor lactating, and it was calculated by summing the six component intervals in the average mated female inventory. The mean NPD was 57.9 d (SD = 20.5), and the proportions of six component intervals of gilt first-mating-to-pregnancy interval, gilt first-mating-to-culling interval, unmated weaning-to-culling interval, weaning-to-first-mating interval, sow first-mating-to-pregnancy interval, and sow first-mating-to-culling interval were 9.24, 7.82, 6.85, 27.9, 18.9, and 29.3%, respectively. Farms in the upper 25th percentile of the ranking for number of pigs weaned.mated female(-1).yr(-1) were designated as 25 high-performing farms. The remaining farms were designated as an ordinary farm group for comparisons. High-performing farms had 21.1 d fewer NPD, and five of the six component intervals were lower compared with the ordinary farms (P < 0.05). Regression analyses indicated that the number of litters.mated female(-1).yr(-1) increased by 0.07 in both farm groups as NPD decreased every 10 d. Fewer NPD were correlated with a higher percentage of multiple matings during estrus (P < 0.05) but were not correlated with removal risk and replacement risk in both farm groups. The average parity of culled females was negatively correlated with NPD in the ordinary farm group, and the average farrowed parity was positively correlated with NPD in the high-performing farm group (P < 0.01). Decreasing each component interval of the NPD six components is critical to increasing herd productivity. A high percentage of multiple matings during estrus and appropriate culling management may be key factors to decrease NPD.

Longevity and efficiency associated with age structures of female pigs and herd management in commercial breeding herds

Annual performance measurements, age structures of female pig inventories, and by-parity culling rates were abstracted from data files of 110 herds that participated in a data-share program in Japan. Parity at culling was used as a prime measurement of longevity, whereas pigs weaned x mated female(-1) x year(-1) (PWMFY) was a prime measurement of reproductive efficiency. High or low longevity herds were based on the greatest 50% of the herds or the remaining herds ranked by parity at culling, whereas high or low reproductive efficiency herds were grouped according to the greatest 50% of the herds or the remaining herds ranked by PWMFY. Measurements were analyzed as a 2 x 2 factorial arrangement, using the main effects of the 2 herd groups of longevity (high or low) and reproductive efficiency (high or low). Means of parity at culling and PWMFY were 4.6 (SD = 0.82) and 21.2 (SD = 3.02), respectively. The high longevity group had 1.27 greater parities at culling than the low longevity group (P < 0.05), but no differences between the high and low longevity groups were found in PWMFY (P = 0.21). No differences between the high and low efficiency groups were found in parity at culling (P = 0.50). No interactions between the longevity and efficiency groups were found on any longevity or efficiency measurement (P > 0.20). In herd management, the percentage of reserviced females and the percentage of multiple matings were associated with the longevity group and the efficiency group (P < 0.05). The high longevity group had lower culling rates in parity 0 to 6 than the low longevity group (P < 0.05), whereas no differences between the low and high efficiency groups were found in culling rates in parity 0 to 2 (P > 0.20). This study suggests that measures to achieve longevity and high reproductive efficiency in breeding herds do not conflict and that high reproductive efficiency and high longevity can be achieved.

Preweaning Mortality Risks and Recorded Causes of Death Associated with Production Factors in Swine Breeding Herds in Japan

Preweaning mortality risks, recorded death reasons and related factors for preweaning mortality were studied in 105 breeding herds. Preweaning mortality risk at the herd level was calculated as the difference between the number of pigs born alive in farrowed litters and the number of weaned pigs divided by the number of pigs born alive in litters that farrowed and weaned. The mean of annual preweaning mortality risk was 10.7%. In regression analysis, higher mortality risks were associated with higher parity at farrowing, greater numbers of pigs born alive, and longer lactation length. The period from July to September had a higher mortality risk than that from April to June. The means of cause-specific proportional mortality ratios (PMR) in trauma with low viability and scours were 80.4 and 6.2%, respectively. Sows with pig age 0-1 day during lactation had the highest daily PMR. Sows with pig age 0 to 7 days had higher PMR due to trauma and low variability than those with pig age 8 days older. Sows with pig age over 7 days had higher PMR due to scours than those with pig age 0-7 days. Careful management at farrowing and in early lactation on high parity sows with large litters should be considered to prevent piglets from death due to trauma and low viability, and appropriate herd health programs should be implemented for reducing preweaning mortality due to scours during late lactation.