Yuzo Koketsu

Factors influencing the postweaning reproductive performance of sows on commercial farms

The objective of this study was to investigate the effects of various factors, including lactational feed intake, on the reproductive performance of sows in commercial herds. The 4 measures of reproductive performance were weaning-to-first-service interval, weaning-to-conception interval, litter weight at weaning, and subsequent litter size. Parity, farrowing season, lactation length, farrowing-to-conception interval, litter size, and lactation feed intake were investigated as risk factors common to the 4 measures of post-weaning reproductive performance. Using 4 basic multiple regression models for each measure, the least-square means for sets of factors were compared using the GLM procedure of SAS. Parity 1 sows had the longest weaning-to-first-service interval and weaning-to-conception interval, and the lighter litter weight at weaning (P < 0.05) than mid-parity sows. Sows in Parities 2 to 5 had larger subsequent litter size (P < 0.05) than those in Parities 1 and >/= 7. Sows farrowing in summer and spring had the longest and second longest weaning-to-conception interval (P < 0.05), respectively, while sows farrowing in summer had longer weaning-to-first-service interval than those that farrowed in spring (P < 0.05). Sows farrowing in summer produced the lightest litter weight at weaning (P < 0.05). No differences in subsequent litter sizes were found due to farrowing season (P > 0.10). As lactation length increased, weaning-to-first-service interval and weaning-to-conception interval decreased, and litter weaning weight increased. Longer lactation length and farrowing-to-conception interval were associated with larger subsequent litter size (P < 0.05). Litter size did not affect weaning-to-first-service interval or weaning-to-conception interval. Larger litter sizes were associated with heavier litter weight at weaning. Greater lactation feed intake improved the 4 measures of reproductive performance.

Management factors associated with swine breeding-herd productivity in the United States.

A database containing 24 key production measurements was created by abstracting data files of 673 U.S. farms which participated in the PigCHAMP data-share program in 1995. Summary statistics for breeding-herd performance data were presented for the Cornbelt and the South or Eastern regions. Eight models were built to assess the association between production system, operation management factors and productivity outcomes. Lactation length, percentage of multiple matings, parity of culled sows, percent gilts in the breeding-female inventory, and female culling rate were the management factors identified as having important associations with productivity outcomes. For example, shorter lactation length, higher percentage of multiple matings, and lower culling rate were associated with more pigs weaned per mated female per year. In addition, a lower percentage of gilts in the breeding-female inventory and a higher percentage of multiple matings were associated with fewer average non-productive female days. We recommend that producers change their management systems to decrease lactation length, the percentage of gilts in the breeding-female inventory, and female culling rate, and increase percentage of multiple matings in order to improve breeding-herd productivity on swine farms.

Returns to service after mating and removal of sows for reproductive reasons from commercial swine farms

We studied the records of 30 herds with an average inventory of 11,705 sows, 25,719 farrowings and 25,040 daily feed intake logs. Production events were recorded by producers using the PigCHAMP production information system. Of 21,505 matings, 7.2% of sows subsequently returned to estrus after service. The proportionate rates of intervals from service to the subsequent post service event were 0 to 17 d, 2.1%; 18 to 25 d, 27.9%; 26 to 37 d, 13.8%; 38 to 46 d, 15.8%; 47 to 108 d, 30.4%; and >108 d, 10.0%. Sows returned to service after mating were categorized into groups that either regularly or irregularly returned to service after mating. Of a total inventory of 19,076 sows, 10.0% were removed following weaning for reproductive reasons. The reasons for removal included those of anestrus (25.2%), failure to conceive (37.0%), failure to farrow (15.0%), not pregnant (1.4%), negative pregnancy check (14.0%), and abortion (7.4%). The last 5 types of post weaning reproductive failure were grouped into the category of did not farrow. Categorical additive models and comparisons using contrasts were used to analyze the influence of risk factors on reproductive failure. Parity 1 sows had a higher proportion (P < 0.01) of returns to service and a greater proportion of sows remaining anestrous post weaning relative to Parity 3 sows. The proportion of sows that did not farrow was higher (P < 0.01) in Parities 9 and 10 than in Parity 3. More sows were removed for anestrus during the spring (P < 0.01) and summer (P = 0.06) than during the winter. All categories of lactation length had similar rates of reproductive failure except for the lactation length 1 to 7 d, which had a higher (P < 0.05) proportion of reproductive failure. Lower lactational feed intake was associated with an increased risk of occurrence of each reproductive failure category. The odds ratios of lactation feed intake in logistic regression analyses were 0.84, 0.89, 0.82 and 0.88 for regularly and irregularly returned to service, anestrus, and did not farrow groups, respectively. This means, for example, that a sow was 0.88 times less likely to have an occurrence of not farrowing for each 1 kg increase in average daily feed intake during lactation. Our results indicate that lower and higher parities, spring and summer seasons, a lactation length of less than 8 d and lower feed intake during lactation affect the occurrence of return to service after mating and of herd removal for reproductive reasons.

Influence of lactation length and feed intake on reproductive performance and blood concentrations of glucose, insulin and luteinizing hormone in primiparous sows.

Twenty-four pregnant gilts were assigned to four experimental treatments in a 2 x 2 factorial arrangement. The first factor was lactation length (12 vs. 21 days) (LL); the second factor was a provided amount of diet (FF, full feeding vs. low, 2 kg/day). The same diet (1% lysine and 3.27 Mcal ME/kg) was used from farrowing to 1 day after weaning. Sow body weight, backfat thickness (BF), litter weights, and blood samples were measured prior to and 1 day after weaning. Sows were monitored for estrous once daily in the presence of a boar until 35 days after weaning or until estrous was detected. Average feed intake during lactation (ADFI) was 1.9 (low) and 4.0 (FF) kg/day. ADFI among individual sows varied from 1.8 to 4.9 kg/day. Positive effects of both LL and feed intake treatments were found (P < 0.05) on sow body weight loss, backfat loss, glucose concentrations, mean luteinizing hormone (LH) concentrations, and LH pulse frequency prior to weaning, and farrowing-to-estrous interval. Greater concentrations of insulin prior to weaning were associated only with feed intake treatment (P < 0.05). No interactions between LL and feed intake treatments were found in any measures except for sow body weight loss. Using regression analysis, greater lactation feed intake was associated with greater concentrations of insulin and glucose, greater LH pulse frequency prior to weaning and shorter farrowing-to-estrous interval in both LL treatments. We suggest that greater feed intake during lactation improves farrowing-to-estrous interval through LH release regardless of LL treatment.

Influence of feed intake during individual weeks of lactation on reproductive performance of sows on commercial farms

Abstract The influence of average daily feed intake (ADFI) during different weeks of lactation on the reproductive performance of sows was investigated. Data contained 18243 farrowing and 15671 ADFI records for sows with lactation length between 7 and 22 days from 30 commercial farms. The regression coefficients of ADFI during individual 3 weeks of lactation on the three measures of reproductive performance were compared. The coefficients of ADFI on natural log-transformed weaning-to-service interval were larger for week 2 (−0.0529 for parity 1; −0.0579 for parity 2 or greater) than for weeks 1 (−0.0340 for parity 1; −0.0277 for parity 2 or greater) and 3 (−0.0295 for parity 1; −0.0188 for parity 2 or greater). The coefficients of ADFI for weeks 2 (0.6667) and 3 (0.6301) in parity 1 sows on litter weight at weaning were larger than that of week 1 (0.3051). In parity 2 or greater, the coefficient of ADFI for week 3 (1.2787) was intermediate between those for weeks 1 (1.0533) and 2 (1.6956). No differences were found between the coefficients of ADFI during individual weeks on subsequent litter size. It is suggested that increased feed intake during early and mid-lactation reduces weaning-to-service interval more than it does during late lactation, and increased feed intake during mid- to late lactation increases litter-weaning weights more than it does during early lactation.

Culling intervals and culling risks in four stages of the reproductive life of first service and reserviced female pigs in commercial herds

The objectives of this study were to measure culling intervals and culling risks in the four stages of the reproductive life of female pigs and to compare culling intervals between the number of services and between herd groups, based on herd productivity. We also compared survival patterns of females pigs between these herd groups. Our data set included lifetime records of 52,792 females born between 2001 and 2004 in 101 commercial herds. Two herd groups were selected on the basis of the upper 25th percentile of pigs weaned per mated female per 5 yr between 2002 and 2006, namely the high-performing herds, and ordinary herds. Culled females were also allocated into four groups based on the stages of their reproductive life when culled: unmated gilts, mated gilts, unmated sows, and mated sows. Culling intervals in unmated gilts and mated gilts were defined as the number of days from birth to culling and from first mating to culling, respectively. Culling intervals in unmated sows and mated sows were the number of days from weaning to culling. The number of services was categorized into two groups: first service and reservice groups. Multilevel linear mixed-effects models and survival analysis were performed. Culling intervals (+/-SEM) in unmated gilts, mated gilts, unmated sows, and mated sows were 302.9+/-1.16, 98.4+/-0.92, 14.3+/-0.12, and 89.6+/-0.42 d, respectively. Culling risks in the four groups were 5.6%, 7.1%, 58.0%, and 29.3%, respectively. In unmated gilts, mated gilts, and mated sows, the culling intervals in the high-performing herds were 43.0, 18.9, and 16.0 d shorter than those in ordinary herds, respectively (P<0.05), but no difference was found between the herd groups for the culling interval of unmated sows. For mated sows in the reservice group, culling intervals of high-performing herds were >or=13.7 d shorter than those of the ordinary herds (P<0.05), but for mated sows in the first service group, there was no difference in the culling interval between the herd groups. The culling hazard from 8 wk postweaning for mated sows in high-performing herds increased more rapidly than that in ordinary herds. In conclusion, to reduce culling intervals and improve herd productivity, we recommend implementing a strict culling policy for mated gilts and mated sows, especially reserviced females.

Mortality, death interval, survivals, and herd factors for death in gilts and sows in commercial breeding herds.

The objectives of this study were to measure death intervals and survival, to determine mortality rate and mortality risks, and to investigate the association of herd factors with mortality risk in individual female pigs. This study was conducted by obtaining female data with lifetime records of 65,621 females born between 1999 and 2002, and herd data with mean measurements of 5 yr from 2000 to 2004 in 105 herds. Annualized mortality rate was calculated as the number of dead females divided by the sum of life days in all gilts and sows, multiplied by 365 d. Mortality risk was calculated as the number of dead females divided by the number of surviving females at farrowing in each parity. Death interval in gilts was defined as the number of days from birth to death, and that in sows was the number of days from the last farrowing to death. A Cox proportional hazards model was used to obtain the survival probability by parity. Logistic regression analyses were used to investigate the association of herd factors with mortality risk in individual females in each parity. Of the 65,621 females, the mortality risk was 9.9%, and the annualized mortality rate was 3.9%. Of the 6,501 dead females, death intervals in gilts and sows were 294.7 and 55.0 d, respectively. In gilts, survival probability rapidly decreased at 33 and 50 wk of age, around the first mating and the first parturition. In contrast, survival probability in sows decreased at wk 1 after farrowing, and rapidly decreased at wk 20 and 21 after farrowing in all parity groups that were around a subsequent peripartum period. The percentages of death on wk 0, 1, and 2 after the last farrowing in all the dead sows were 6.5, 23.5, and 10.1%, respectively. Approximately 10% of deaths also occurred from wk 20 to 21 after the last farrowing. Death interval in parity > or =5 was the shortest among all parity groups (49.2 d; P < 0.05). Mortality risks in parities 0 and 1 were 1.44 and 1.83%, respectively. As parity increased from 2 to > or =5, mortality risk increased from 1.63 to 5.90%. Herd factors (greater herd mortality, less herd productivity, and smaller herd size) were associated with greater mortality risk in individual females in parity 0 to > or =5, parity 4 and > or =5, and parity 1 to 4, respectively (P < 0.05). In conclusion, females in peripartum periods, gilts, and high-parity sows are at a greater risk of dying. Increased care should be implemented for prefarrowing females and early-lactating sows.

Interactions between climatic and production factors on returns of female pigs to service during summer in Japanese commercial breeding herds

The objectives of this study were to determine the associations between climatic factors and production factors for returns to service of female pigs during summer and to quantify the associations between these factors and occurrences of returns to service. The factors that were assessed were as follows: maximum temperature (HT), relative humidity, age of gilts at first mating, parity, weaning-to-first-mating interval (WMI), and lactation length. The study analyzed records of 18,307 gilts in 99 herds and 78,135 parity records of 56,322 sows in 103 herds; all the females were first-serviced between June and September, 2007 to 2009. Average daily HT and relative humidity for 15 days post-service of a female were obtained from 21 local weather stations and coordinated with the performance data of the respective local herds. The returns to service were categorized into three groups: regular returns (RRs: 18-24 days), irregular returns (IRs: 25-38 days), and late returns to service (LRs: 39 days or later). Two-level mixed-effects models were applied to the data by using a herd at level 2 and an individual record at level 1. In mated gilts, the occurrences (%) of RRs, IRs, and LRs were 4.8%, 1.8%, and 5.3%, respectively. In mated sows, the respective occurrences were 3.3%, 1.8%, and 4.2%. Mean values (ranges) of HT and relative humidity were 28.4 °C (13.6 °C-39.8 °C) and 73.4% (35.0%-98.0%), respectively. In gilts, as HT increased from 25 °C to 30 °C, the occurrence of RR increased from 3.7% to 4.4% (P < 0.05). However, there was no association between the occurrence of RR and either relative humidity (P = 0.17) or age at first mating (P = 0.23). In addition, there were no associations between the occurrences of either gilt IR or LR and HT (P ≥ 0.05), relative humidity (P ≥ 0.46), or age at first mating (P ≥ 0.32). In sows, greater occurrences of RRs, IRs, and LRs were associated with higher HT, lower parity, and a WMI of 7 days or longer (P < 0.05), but they were not associated with relative humidity (P ≥ 0.62) or lactation length (P ≥ 0.13). The occurrence of RRs in sows of all WMI groups increased 1.22 (1.04(5)) times for each 5 °C increase in HT. For sows with WMI 0 to 6 days, each 5 °C rise in HT increased the occurrence of IRs and LRs by 1.36 (1.06(5)) and 1.27 (1.05(5)) times, respectively. However, there was no association between increased HT and occurrences of IRs or LRs for sows with WMI 7 days or longer (P ≥ 0.38). Therefore, in order to prevent returns to service, it is recommended that producers apply cooling management for females during the post-service periods in summer.

Boar culling and mortality in commercial swine breeding herds

The objectives of this study were to measure culling rate and mortality rate of boars; to compare boar life day (BLD: days from birth date to removal date), boar herd life day (BHLD: days from herd entry date to removal date) and herd entry age of boars between high-performing herds and ordinary herds (herd groups); to examine herd measurements for BLD, BHLD and boar age at herd entry; and to observe removal patterns and survival curves for boars by herd groups. This study used 2474 records of individual boars born in 108 herds from 2000 to 2003. Two herd groups were formed on the basis of the upper 25th percentile of pigs weaned per mated female per year (2001-2005). Mixed-effects models and survival analysis were performed. Means of BLD and BHLD (+/-S.E.M.) were 984+/-9.5 and 781+/-8.4d, respectively. Annualized culling rate and mortality rate were 0.411 and 0.035 boars per 365 BHLD, respectively. Boars in high-performing herds had 51 higher BLD and 62 higher BHLD than those in ordinary herds (P<0.01). High-performing herds had 32 d lower entry ages than ordinary herds (P<0.01). Herd measurements such as herd mortality and herd size were not associated with both BLD and BHLD. The hazards in survival analysis were associated with herd groups (P<0.05). Measurements in the present study provide benchmarks for boar removal in commercial herds.

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.