Gary D. Dial

Lifetime reproductive performance in female pigs having distinct reasons for removal

This study describes the reasons for removal of female pigs distributed across parity categories, and evaluates how parameters of lifetime productivity differ for females having distinct removal reasons. The study analyzed lifetime records ® from 7973 females. Those records were obtained from 28 herds from the PigCHAMP research database having high-quality data during a five-year period. Female life expectancy corresponded to 3.3 parities at removal or 1.6 years spent in the breeding herd. The most common removal reason was culling attributed to reproductive disorders (33.6%), followed by culling for sub-optimal litter performance (20.6%). Sows culled for old age (8.7% of the removals) spent proportionally fewer days in non-productive periods, and produced more weaned pigs annually and over a lifetime than females removed for other reasons (P , 0.05). In contrast, females culled for reproductive failure accumulated the largest proportion of non-productive days (NPD) during the time spent in the breeding herd, and produced the fewest weaned pigs per lifetime and per year (P , 0.05). These findings indicate that culling for reproductive reasons is more common among low-parity females, which suggests that minimisation of NPD at early reproductive cycles is crucial to optimise female lifetime reproductive efficiency.

An indirect fluorescent antibody test for the detection of antibody to swine infertility and respiratory syndrome virus in swine sera

An indirect fluorescent antibody (IFA) test was developed and standardized to detect and quantitate antibody for swine infertility and respiratory syndrome (SIRS) virus in swine sera. Test results were evaluated using sera of pigs infected both experimentally and naturally with SIRS virus. The IFA test used swine alveolar macrophage (SAM) monolayers prepared in 96-well microplates and infected with SIRS virus. The monolayers were incubated with test sera, washed, and stained with fluorescein isothiocyanate-labeled rabbit anti-swine IgG. After another wash step, the monolayers were examined under a fluorescent microscope. A noninfected SAM control well was included for each sample. The antibody titers for each serum sample were recorded as the highest serum dilutions with specific cytoplasmic fluorescence but no fluorescence in the control wells. To evaluate the test, sera of 4 6-week-old pigs that had been infected with SIRS virus, 2 contact pigs, and 13 experimentally infected sows were used. In the experimentally infected pigs, antibody was first detected at 7 days postexposure (PE) and peaked (1:256–1,024) between 11 and 21 days PE. All 13 sow sera were negative at time of infection but were positive (1:64-> 1: 1,024) at 14–26 days PE. Seven hundred twenty sera collected from 25 different swine farms with or without a history of SIRS were also tested. Of 344 sera from 15 swine farms with a clinical history of SIRS, 257 (74.7%) sera had IFA titers ≥ 1:4, whereas 371 (98.7%) of 376 sera from herds with no history of SIRS were negative. The present results indicate that the IFA is a useful test for the detection and quantitation of SIRS virus antibody in swine sera.

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.

Influence of lactation length on sow productivity

Abstract Associations between sow lactation length, the productivity of individual sows at their subsequent farrowings, and annual breeding productivity were analyzed using a data base including 14925 farrowing records from 39 swine herds. Longer lactation lengths were associated with higher subsequent litter sizes (both total-born and born-alive), shorter weaning-to-service intervals, longer farrowingto-service intervals, and longer farrowing-to-farrowing intervals ( P P > 0.2). The observation that reducing lactation length from 30 to 17 days does not significantly affect pigs per sow per year is attributed to the compensatory effects of shorter lactation on pigs born per litter and litters per sow per year. This range of lactation length is commonly employed by American swine producers and appears to incorporate the optimal range for breeding herd productivity as measured in terms of pigs weaned/sow/year. Nevertheless, the optimal lactation length for an individual herd likely will be influenced by its particular management, environmental and financial characteristics.

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.

Validation of producer-recorded causes of preweaning mortality in swine

Abstract This study examined the accuracy of producer-recorded causes of preweaning mortality on 13 commercial swine farms using a computerized recording system. All stillborn piglets and those born alive but dying between birth and weaning were collected over 6–8-week period and stored frozen until necropsy. Reason for death, piglet age, date of death and antemortem history, when known, were recorded by producers for 1063 dead piglets. There were 916 piglets born alive but dying before weaning, 146 stillborn piglets and one mummified piglet. Gross observations at postmordem examination were used to classify piglets into the following major categories of mortality: low viability, trauma, scours, deformed, infection, stillborn, and other. The relationship between producer-recorded causes of death and causes established at necropsy was expressed in terms of sensitivity and specificity. Sensitivity was the proportion of piglets correctly classified within a category, using necropsy results as the gold standard. Specificity was the proportion of piglets correctly excluded from a category. The sensitivity and specificity of producer assessment of the death causes varied with the mortality category. Within each category, variations in sensitivity and specificity also were noted among age groups. The results demonstrated that without validation of data-recording accuracy, retrospective and prospective studies using producer diagnosis of causes of death in suckling piglets are likely to be invalid.

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.

Artificial insemination in swine.

This article analyses the advantages and disadvantages of artificial insemination with semen purchased from a center as well as from the herd boars on the farm. Intensive swine production could benefit greatly by adapting artificial insemination with herd boars, particularly from savings in labor and boar numbers. The techniques for semen collection, extension, and insemination are described, and sources for equipment given. Expected results of artificial insemination are quoted from experiments and international field experience.