Lifetime reproductive and financial performance of female swine.

OBJECTIVE: To evaluate reproductive and financial performance for commercial swine herds grouped on the basis of pattern of removal of female swine. DESIGN: Cohort study. SAMPLE POPULATION: 25 swine herds. PROCEDURES: Lifetime reproductive productivity was summarized as number of pigs weaned per herd day per mated female and as number of herd days per pig weaned per mated female. Factors associated with these 2 measures were determined by use of linear regression. Financial data from a commercial database were used to estimate maximum number of parities at removal associated with profitability. Sensitivity analysis was used to simulate how variations in daily maintenance cost and value per weaned pig would influence profitability. RESULTS: Mean number of pigs weaned per herd day per mated female was 0.054; mean number of herd days per pig weaned per mated female was 20.2. Both these measures were associated with proportion of nonproductive days during herd life, preweaning mortality rate per litter weaned, mean lifetime number of pigs born alive per litter weaned, and mean lifetime lactation duration. Maximum parity at time of removal associated with profitability ranged from 5 to 8. Daily maintenance costs per female had a greater impact on lifetime profitability than did value per weaned pig. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that lifetime reproductive and financial performance is optimized among swine herds that have higher proportions of high-parity females.

Estimation of lifetime productivity of female swine.

OBJECTIVE: To develop estimates of lifetime productivity for breeding female swine calculated longitudinally during time in the breeding herd, and to compare estimates of lifetime productivity for female swine removed from the herd at different parities. DESIGN: Retrospective cohort study. ANIMALS: 9,416 breeding female swine from 29 herds. PROCEDURE: A frequency distribution for parity at the time of removal was generated. Estimates of lifetime productivity (lifetime nonproductive days [NPD], lifetime NPD as a proportion of herd life, total number of pigs born per litter weaned, number of pigs born alive per litter weaned, number of pigs weaned per litter weaned, number of NPD per year in the herd, number of litters weaned per year in the herd, and number of pigs weaned per year in the herd) were calculated for females with parity > or = 1 at the time of removal. RESULTS: For 58% of all females, parity at the time of removal was < or = 3. On average, 20.7% of herd life was spent in nonproductive activities, but the proportion of herd life that was nonproductive decreased significantly as parity at the time of removal increased. Number of NPD per year in the herd decreased and number of litters weaned per year in the herd and number of pigs weaned per year in the herd increased significantly as parity at the time of removal increased. CLINICAL IMPLICATIONS: Higher parity at the time of removal from the herd is associated with improved lifetime productivity for female swine. Parity at time of removal is commonly used as an approximation for lifetime productivity, but it does not take into account the impact of NPD, especially NPD during early reproductive cycles.

Prevalence of lesions and body condition scores among female swine at slaughter.

OBJECTIVE: To determine prevalence of foot lesions, dermatitis, shoulder lesions, mammary gland abnormalities, and visceral lesions, and body condition scores among culled female swine at slaughter. DESIGN: Observational study. ANIMALS: Culled gilts and sows killed during a 1-week period at a Midwest slaughterhouse. PROCEDURE: Carcasses were examined, and lesions were recorded. Body condition was scored on the basis of standard criteria. RESULTS: 58.9% (1,029/1,747) of the carcasses had foot lesions, 67.3% (1,178/1,751) had dermatitis, and 4.6% (80/1,751) had shoulder lesions. Body condition score was significantly associated with detection of dermatitis and shoulder lesions. Mean +/- SE number of teats (n = 1,432 carcasses) was 13.86 +/- 0.02. Mean numbers of normal-appearing teats in the left and right mammary chains were 6.57 +/- 0.02 and 6.58 +/- 0.02, respectively. Feet from 48% (688/1,433) of the carcasses were condemned. Visceral lesions were found in 48.8% (624/1,278) of the carcasses; of the carcasses with lesions, 412 (66%) had liver spots, and 268 (42.9%) had pneumonia. CLINICAL IMPLICATIONS: Lesions that potentially could have adversely affected production were found in a large percentage of culled gilts and sows at slaughter. Knowledge of lesions commonly found at slaughter may help direct changes in herd health programs.

Epidemiologic analysis of factors influencing exertional rhabdomyolysis in Thoroughbreds.

OBJECTIVE: To determine incidence, effect on performance, and management practices associated with exertional rhabdomyolysis (ER) in Thoroughbreds. SAMPLE POPULATION: Medical records for 984 Thoroughbreds and a survey of trainers of horses with and without ER. PROCEDURES: Medical records for 984 Thoroughbreds stabled at a midwestern racetrack were examined to determine the incidence of ER during the 1995 racing season. A retrospective questionnaire was administered to trainers to determine management practices associated with ER in 59 Thoroughbreds with ER and 47 control Thoroughbreds in training. Multiple logistic regression was used to determine management factors associated with ER. RESULTS: ER affected 48 of 984 (4.9%) Thoroughbreds. Two-year-old females were most frequently affected, and 36 of 96 (37.5%) trainers had > or = 1 horse with ER. Horses with ER were more likely not to race during the racing season, compared with control horses. For horses that raced, differences were not found with respect to racing performance between ER and control horses. Exertional rhabdomyolysis developed frequently in susceptible horses that had > or = 1 day of rest prior to exercise and that galloped during exercise. Horses with ER were commonly fed > 4.5 kg of grain daily. Nervous and extremely nervous horses were 5.4 times more likely, and horses with some form of lameness were 4.2 times more likely, to have ER. CONCLUSIONS AND CLINICAL RELEVANCE: Exertional rhabdomyolysis is common in Thoroughbreds, and ER can be affected by temperament, sex, age, diet, exercise routines, and lameness. Management that minimizes excitability, particularly when tailored to each horse, may be most effective for controlling ER.

Risk factors for twinning in dairy cows.

Records for 52,362 lactations over a 10-yr period from 260 dairy farms in North America that used a common commercial software for record keeping were evaluated for potential risk factors for twinning. Records were evaluated for the associations of reproductive disease, parity, production, drug therapy, and the occurrence of subsequent twins. The rate of twinning on these farms steadily increased over the observation period from 1.4% in 1983 to 2.4% in 1993. The rate of twinning also increased as parity of the cow increased, from 1.0% for cows in their first lactation to > 4.1% for cows in their fifth or higher lactation. No association between twinning and season of year was detected. A multivariate logistical regression analysis found that the rate of twinning increased with increases in milk production, incidence of cystic ovarian disease, and the use of common pharmaceuticals, including GnRH, PGF2 alpha, and antibiotics. Results of the regression model also indicated that the single most important reason for the recent increase in the rate of twinning was a concurrent increase in milk production.

Evaluation of the effects of nursery depopulation of the profitability of 34 pig farms.

The financial impact of nursery depopulation was assessed on 34 pig farms by constructing a partial budget model to measure the profitability of the nursery production. The model measured margin over variable cost and used production data generated from a previous study; it assumed that fixed costs remained constant throughout the study and that feed cost, weaned pig cost and market price per nursery pig also remained fixed. The mean margin over variable cost per sow on the 34 farm after nursery depopulation was Pounds 116. Thirty-two of the farms showed reductions in this cost, ranging from Pounds 20 to Pounds 408 per sow, in the 12 months after nursery depopulation compared with the previous 12 months. Of the two farms which did not show an increase in profitability, one showed no change and the other showed a net loss of Pounds 8 per sow. The sows' serostatus for porcine reproductive and respiratory syndrome virus infection was monitored but there was no significant difference between the margin over variable cost per sow of the seropositive (Pounds 130) and seronegative (Pounds 170) herds.

Association between lactation length and sow reproductive performance and longevity.

OBJECTIVE: To determine whether lactation length was associated with reproductive performance or longevity of sows. DESIGN: Cohort study. SAMPLE POPULATION: Data collected between 1986 and 1992 for sows in 15 breeding herds in Minnesota and Iowa. PROCEDURE: Sows were grouped into 4 genetic line categories according to their sources and 6 parity categories (1, 2, 3, 4, 5 or 6, and > or = 7). Multivariate regression analysis of reproductive performance was conducted, using the general linear model procedure Logistic regression was conducted with a dichotomous response variable for sow longevity (ie, removal from or retention in the herds). Odds ratios were obtained from estimated coefficients of the regression. RESULTS: Herd, genetic line, parity, year, month, and lactation length were significant in statistical models for litter (eg, number of live pigs/litter) and interval (eg, weaning-to-mating interval) traits. Interactions between lactation length and year, lactation length and genetic line, lactation length and parity, and lactation length and genetic line and parity were also significant. Sows removed from herds had a significantly shorter lactation length than did sows of the same parity that were retained in the herds. Sows that had shorter lactation lengths were at higher risk of being removed from the herds than were those that had longer lactation lengths. CLINICAL IMPLICATIONS: Lactation length is associated with reproductive performance and longevity, but genetic line and parity play a role as well. Thus, attention should be paid to genetic lines and parity of sows in the herd when implementing an early weaning production practice.

Relationship of production to reproductive performance in Ontario dairy cows: herd level and individual animal descriptive statistics.

Data were collected on reproductive, health and production events in 45 dairy herds distributed throughout southwestern and eastern Ontario. The data were collected between July 1990 and July 1993. The herds were serviced by 11 different veterinary practices. Herd size ranged from 19 to 231 lactating cows, but 90% of the herds consisted of fewer than 125 milking cows. Mean and median actual milk yields per cow per day were 46.0 and 52.3 lbs, respectively, with a minimum of 21.3 and maximum of 67.8 lbs. Mean and medium adjusted corrected milk yields were 56.0 and 62.3 lbs, reflecting mean and median average days in milk of 199.0 and 198.5 d, respectively. Mean and median days in milk at the first estrus were 85.1 and 83.9 d, respectively, at first service 94.0 and 88.9 d, and at conception 126.3 and 115.5 d. Mean and median percentages of days open > 120 were 27.7 and 23.1%, respectively. The mean estrus detection rate was 48.3%, with a minimum of 28.4% and a maximum of 64.2%. The mean first service conception rate was 48.2%, with a minimum of 27.0% and maximum of 72.1%. The mean overall conception rate was 46.7%, with a minimum of 29.8% and a maximum of 70.7%. Mean and median lactation lengths were 341.1 and 338.5 d and the mean and median average dry days were 62.0 and 67.0, respectively. The mean lactational removal rate was 20.6%, with a range of 4.3 to 40.5%. Reasons for culling were available for 1381 cows. Low production accounted for 23.7 % of the cullings; reproductive reasons, 20.6 %; dairy sales, 13.4%; mammary problems, 12.8%; and lameness, 9.9%. Lactational incidence rates for diseases were lower than previously reported for Ontario dairy herds. The most commonly used therapeutic agents were GnRH (10.5%) and PGF (11.7%).

Agreement among veterinarians evaluating gross lesions of lungs, livers, and nasal turbinates of pigs.

OBJECTIVE: To evaluate agreement between trained veterinarians and a reference inspector when recording gross lesions of lungs, livers, and nasal turbinates of pigs. DESIGN: Prospective study. SAMPLE POPULATION: 10 veterinarians in workshop 1 and 11 veterinarians in workshop 2. PROCEDURE: Analysis of data obtained from 2 workshops in which veterinarians evaluated fresh tissues (30 lungs and 30 livers) and 100 slides of nasal turbinates previously evaluated by the reference inspector. Veterinarians independently recorded observations of gross lesions. Agreement was evaluated by percentage agreement, kappa or weighted kappa, and sensitivity and specificity, where relevant. RESULTS: Agreement between veterinarians and the reference inspector was excellent for detecting consolidation of lung lobes typical of enzootic pneumonia (kappa = 0.81 and 0.87 for workshops 1 and 2, respectively) and white spots on livers (kappa = 0.76 and 0.78). Estimates of the extent of consolidation as a proportion of lung volume also agreed closely with reference values. Agreement was closer for veterinarians who had undergone repeated training and evaluation. Agreement was good for detecting nasal turbinate atrophy (weighted kappa = 0.63 and 0.68) and was poorest for detecting lesions of pleuritis (kappa = 0.39 and 0.44). CLINICAL IMPLICATIONS: For most of the lesions evaluated, acceptable levels of agreement with reference scores were achieved after training of veterinarians to use standardized methods to record gross lesions. Standardization of veterinarians' recordings of gross lesions should improve the reliability and usefulness of data collected by inspection of slaughtered pigs.

Attitudes of veterinarians to a standardized slaughter-monitoring program for pigs.

OBJECTIVE: To determine attitudes of participating veterinarians toward a standardized slaughter-monitoring program for swine. DESIGN: Survey by mail questionnaire. SAMPLE POPULATION: 30 of 35 veterinarians in Minnesota who had participated in the program in 1993. PROCEDURE: Survey was conducted regarding a slaughter-monitoring program. Respondents answered questions related to professional experience, use of slaughter inspections, methods, advantages and disadvantages of the program, effects on clients and business, labor requirements, referral of inspections, confidence in identifying lesions, and usefulness of reports for on-farm decision making. RESULTS: 27 respondents expressed overall satisfaction with the program. Perceived advantages of the program included use of standardized methods, quality of reports, inspection of more types of lesions, and accumulation of data. Disadvantages predominantly related to increased time commitments for veterinarians. Data considered most useful for on-farm decision making were white spots on livers, nasal turbinate atrophy, and lesions indicative of papular dermatitis and enzootic pneumonia. Respondents perceived positive effects of participating in this program in the areas of recruitment of clients, frequency of visits to clients, recommendations made to the clients, satisfaction of client needs, and generation of revenue. CLINICAL IMPLICATIONS: A standardized slaughter-monitoring program designed to provide improved information from slaughter inspections may be beneficial to the businesses of participating veterinarians.

Characterization of feed intake patterns during lactation in commercial swine herds.

This study created and used a data-base containing 25,719 farrowing and 19,393 subsequent litter records abstracted from the PigCHAMP records of 30 commercial farms and daily feed intake records of 25,040 of these lactating sows. Each lactation feed record was categorized into one of six patterns: RAPID, rapid increase in feed intake following farrowing; MAJOR, major drop in feed intake during lactation; MINOR, minor drop; LLL, low feed intake throughout lactation; LHH, low feed intake during the first week then increasing for the remainder of lactation; and GRADUAL, gradual increase in feed intake throughout lactation. At the herd level, patterns RAPID, MAJOR, MINOR, LLL, LHH, and GRADUAL were observed in 22.8%, 32.9%, 27.8%, 1.0%, 8%, and 14.7% of sows, respectively. On a sow basis, across all feed intake records of all farms, patterns RAPID, MAJOR, MINOR, LLL, LHH, and GRADUAL were observed at frequencies of 17.8%, 38.3%, 25.8%, 1.2%, 1.5%, and 15.4%, respectively. Using logistic regression, the risk factors affecting the occurrence of MAJOR and MINOR patterns were lower parity, thicker backfat, higher room temperature, and greater feed intake during early lactation. Average daily feed intake and the day of peak intake were 5.2 (1.4 SD) kg/sow and 12.6 (4.6 SD) d after farrowing. Regression coefficients of factors affecting ADFI derived from multiple regression analyses were 247 g for parity, 9 g for weaning litter weight (kg), -13 g for room temperature (degree C), 62 g for lactation length (d), and -.4 g for energy density (kcal/kg). This study demonstrated substantial individual sow and farm variation in overall feed intake and pattern of feed intake during lactation. It also identified key risk factors (i.e., parity, lactation length, room temperature, weaning litter weights, energy density) for ADFI and pattern of feed intake on commercial farms.

Influence of imposed feed intake patterns during lactation on reproductive performance and on circulating levels of glucose, insulin, and luteinizing hormone in primiparous sows.

Thirty-six primiparous sows were assigned to one of five treatments designed to mimic the lactation feed intake patterns observed in a previous study of commercial farms: high energy intake (HHH) or low energy intake during each week of a 3-wk lactation (LLL), or reduced intake during wk 1 (LHH), wk 2 (HLH) or wk 3 of lactation (HHL). The metabolizable energy intake of sows was either 16.5 (H) or 6.5 (L) Mcal/d. Diets were equal in lysine, providing 45 g/d. The HHH sows had a shorter (P < .05) weaning-to-estrus interval (9 +/- 3.2 d) than the sows in the LLL (23 +/- 3.5 d), HLH (22 +/- 3.5 d), and HHL (18 +/- 3.2 d) groups. The LH pulse frequencies of HHH (d 14: 1.5 pulses/8 h; d 21: 2.1 pulses/8 h) were greater (P < .05) than those of LLL (.2 pulses/8 h) and HLH (.5 pulses/8 h) on d 14 and those of LLL (0 pulses/8 h) and HHL (.9 pulses/8 h) on d 21 of lactation. No differences (P > .1) in mean serum concentrations of LH were observed among treatment groups either on d 21 of lactation or on d 1 postweaning. When fed a low-energy diet, sows had lower (P < .05) concentrations of serum insulin and plasma glucose than did sows fed a high-energy diet. Our results indicate that energy intake during lactation influences circulating insulin and glucose levels and LH pulse frequency and amplitude during midlactation and during the postweaning period.

Evaluation of the monitoring of papular dermatitis lesions in slaughtered swine to assess sarcoptic mite infestation.

We investigated the association between the presence of papular dermatitis and sarcoptic mite infestation in pigs slaughtered in southern Minnesota. Following dehairing, a sample of 30 pigs from each of 50 herds was inspected for papular dermatitis lesions. Herds were selected after being categorized into one of five categories according to the prevalence and severity of dermatitis lesions. Herd infestation with sarcoptic mange was determined by recovery of mites from ear scrapings of slaughtered pigs and also by survey of producer opinion. Mite infestation was detected in 28 herds (56%) and 215 of 1500 pigs (14%). Considerable variability in prevalence of positive scrapings, ranging from one pig (3%) to 19 pigs (63%), was found among infested herds. Prevalence of mite infestation was positively associated with severity of papular dermatitis lesions in groups. For individual pigs, estimates of the specificity of localized lesions ranged from 0.70 to 0.90. Generalized lesions appear highly specific (> 0.98) for sarcoptic mite hypersensitivity. Generalized lesions occurred in 36.7% of pigs from herds confirmed to be infested, compared with 0.4% of pigs in herds confirmed free from mange. Our date indicate that monitoring of dermatitis lesions in slaughtered pigs might be a useful test for sarcoptic mange in the Midwest, USA.

Epizootiologic evaluation of urolithiasis in cats: 3,498 cases (1982-1992).

OBJECTIVE: to test the hypothesis that breed, sex and age of cats, and anatomic location of uroliths are risk factors for calcium oxalate and magnesium ammonium phosphate urolithiasis. DESIGN: Retrospective case-control study. SAMPLE POPULATION: Records of 3,498 feline urolith accessions submitted between September 1982 and September 1992. PROCEDURE: Mineral composition of feline uroliths was quantitatively analyzed. Odds ratios and 95% confidence intervals were calculated for breed, sex, age, and urolith location as risk factors for calcium oxalate and magnesium ammonium phosphate urolith formation. The population at risk was defined as all cats for which that type of urolith had been submitted. The control population was all cats for which uroliths had been submitted, excluding cats with the type of urolith being evaluated. RESULTS: Burmese, Persian, and Himalayan breeds were at higher risk for developing calcium oxalate uroliths, but at reduced risk for developing magnesium ammonium phosphate uroliths. Compared with females, neutered male cats had a higher risk for developing calcium oxalate uroliths, but a reduced risk for developing magnesium ammonium phosphate uroliths. The risk for calcium oxalate urolith formation increased with age. One- to 2-year-old female cats had the highest risk for magnesium ammonium phosphate uroliths. Uroliths removed from the kidneys were more likely to be composed of calcium oxalate than of magnesium ammonium phosphate. CLINICAL IMPLICATIONS: Breed, sex, and age of cats, and anatomic location of uroliths should be considered when evaluating risk of calcium oxalate and magnesium ammonium phosphate urolithiasis in urolith-forming cats.

Evaluation of the benefits of the timing of pregnancy testing by transrectal palpation in dairy cattle.

OBJECTIVE: To determine the benefits that were associated with pregnancy testing by use of transrectal palpation during the period 30 to 65 days after unsuccessful insemination of dairy cows. DESIGN: Nonconcurrent, cohort study. ANIMALS: Cows in 15 dairy herds in the United States and Canada. PROCEDURE: Reproductive records of cows (n = 713) that did not calve within 294 days of first-service insemination and that had been evaluated for pregnancy 30 to 65 days after first-service insemination were examined. Records were analyzed to determine the day of parturition or date of culling and to determine if the probability of a cow being culled or the interval to parturition was related to the number of days after insemination that pregnancy testing was performed. RESULTS: For cows that calved more than 294 days after first-service insemination, the interval from first-service insemination until parturition was associated significantly with herd, season, and treatment on the day of pregnancy testing with prostaglandin F2 alpha or one of its analogues. Cows treated with prostaglandin F2 alpha on the day of pregnancy testing were less likely to be culled than nontreated cows. For cows pregnancy tested 30 to 65 days after insemination, each additional day after day 30 before pregnancy testing was performed resulted in an increase of 1.09 days in the interval until parturition. CLINICAL IMPLICATIONS: Pregnancy testing by means of transrectal palpation as soon as possible after day 30 after insemination can result in shorter calving intervals.

Comparison of methods for measurement of enzootic pneumonia lesions in pigs.

A rapid subjective method for estimating the extent of gross pneumonia lesions in slaughtered pigs was compared with dissection of lungs in 51 slaughtered pigs. After standardization for prevalence in the regional industry, regression analysis indicated that the subjective method was highly predictive of the extent of pneumonic lesions (R2 = 0.88). Part of the error with the subjective method was attributed to approximations used for the relative proportions of lung lobes, which result in overestimation of the affected tissue by approximately 20%. Retrospective analysis of data from a slaughter monitoring program revealed strong associations (R2, 0.54 to 0.91) between prevalence, mean, median, and maximal lung scores in groups of pigs. Maximal lung score was biased by sample size, but prevalence and mean or median lung scores could be used to describe pneumonia severity in groups of pigs. Our results indicate that error in measurement of the extent of pneumonic tissue in slaughtered pigs is unimportant if the time of onset, clinical severity, and duration of disease are not quantified.

Some risk factors associated with clinical lameness in dairy herds in Minnesota and Wisconsin.

An observational study of the relationships between clinical lameness and herd-level risk factors was made in 18 dairy herds in Minnesota and Wisconsin. Lameness in the lactating cows was assessed by two observers during herd visits made in the summer of 1989 and the spring of 1990, using a uniform scoring system. A questionnaire was used to obtain information about the general management, routine hoof care, nutrition, housing and flooring on the farms. Factors associated with the prevalence of clinical lameness in the summer included stall moisture, the size of the exercise area for the lactating cows and the amounts of dry concentrates and fresh forages fed to them. Factors associated with clinical lameness in the spring included the use of parlour milking facilities and the frequency with which the rations for the lactating cows were balanced.

Options in dairy data management.

A great deal of progress has been made in the development of dairy herd management software in the last few years. At the same time, the speed, capacity, and portability of computer hardware have increased, while costs have decreased, thus encouraging use by veterinarians,dairy herd managers, and other industry support groups. A review of the literature indicates that an increasing number of producers, veterinarians, and other dairy industry service personnel are using computers and dairy herd management software in the delivery of their services (1-3,5,9-11,26-30,38,39). Wider adoption will occur if information generated through the use of these systems is directed towards the improvement of the profitability of dairy production. The quality of a decision is only as good as the information used to make it. In the past, the limited availability of reliable herd data has restricted our understanding of factors that influence herd performance. In essence, we must define what is normal before we can determine what is abnormal. More importantly, we must define what management practices are profitable and to what extent they increase revenue (3 1,32). Improved record keeping will benefit the dairy industry by allowing producers and dairy consultants to make profitable decisions based on more accurate and complete information. The ability to merge biological, management,and economic data may prove valuable in the evaluation of intervention at the herd and individual animal level. The impact of interventions is often as much a function of the unique combination of management factors on a dairy, as the biological effect that can be evaluated in a clinical trial. For example, the use of gonadotrophin-releasing hormone therapy at the time of service has been shown to be more successful in herds with better than average conception rates than in herds with poor conception rates. This difference in efficacy may be due to nutritional and other herd level management factors. Sophisticated dairy information management systems provide valuable herd specific management information, which allows more comprehensive understanding of the complex interaction of pharmaceutical,biological, and management factors that ultimately determine the profitability of veterinary intervention strategies. The use of electronic transfer of data will become essential in order to increase efficiency of use of information through data sharing. This will decrease transfer time and cost of information exchange between dairy herd managers and support industries.

Pregnancy attrition associated with pregnancy testing by rectal palpation.

The objective of this study was to estimate the effect on calving risk of interval from AI date until scheduled date of pregnancy examination. First AI (n = 7105) from 65 dairy herds in the United States and Canada were followed for 294 d to determine whether cows calved. Calving was modeled as a function of the number of days in the interval, herd, season, and breeding at PGF2 alpha-induced estrus by multivariate logistic regression. The main effects of herd and AI following PGF2 alpha-induced estrus were significantly associated with calving rate from first AI. The main effects of interval and season were not significantly associated with calving.

Influence of a gonadotropin-releasing hormone agonist on circulating concentrations of luteinizing hormone and testosterone and tissue concentrations of compounds associated with boar taint.

Twenty-four Yorkshire boars and six barrows approximately 8 mo of age were used to evaluate the effects of a GnRH agonist (GnRH-A) on circulating concentrations of LH and testosterone (T), concentrations of skatole in fat, and concentrations of 16-androstene steroids in fat and salivary glands. Pigs were assigned to five groups of six pigs each: L200, boars injected with 200 micrograms of GnRH-A/kg BW; L50, boars injected with 50 micrograms of GnRH-A/kg BW; Boar, boars treated with vehicle; Castrate, males castrated on the same day that Groups 1 to 3 received injections; and Barrow, males castrated as neonates. Pigs in L200, L50, and Boar were only given one injection. Blood samples were taken twice daily from d -2 to 28 for determinations of T and LH concentrations and at 15-min intervals for 6 h on d -1, 1, 7, 14, 21, and 28 for characterization of pulsatile LH release. Pigs were slaughtered on d 30, and samples of backfat and salivary glands were collected for quantification of skatole and 16-androstene steroid concentrations. The LH concentrations increased immediately following GnRH-A injection in L200 and L50 (P < .001) and then declined to pretreatment values by approximately 29 h after treatment. Serum T concentrations in L200 and L50 increased after GnRH-A treatment (P < .0001) and then decreased to less than pretreatment concentrations by d 5 in L200 (P < .001) and by d 8 in L50 (P < .01). Concentrations of 16-androstene steroids in fat were less (P < .05) in L200 and Barrow than in Boar.(ABSTRACT TRUNCATED AT 250 WORDS)