Analysis of longevity and exterior traits on Large White sows in Switzerland

Records of length of productive life, from first farrowing to culling, of 16,464 Large White purebred sows from SUISAG were studied using survival analysis. The major aims of the study were to model the risk of culling within parity and to assess the influence of exterior traits, such as the number of teats or feet and leg scores, on culling. Culling was concentrated at the first day after each farrowing or at the first day after weaning. Weaning itself was mostly between 21 and 49 d after farrowing, with an average weaning age of 35 d. Because of the definition of culling date used, there was practically no risk of culling from these periods. The culling rates at different periods suggested a modeling of the baseline hazard function within parity instead of over the entire productive life of the animals. A piecewise Weibull function and a simple graphical method to validate its adequacy were proposed for sow longevity analysis. The risk of culling increased with older parities (P < 0.001) and with decreasing litter size at weaning (P < 0.001). The exterior traits analyzed (number of teats, and feet and leg scores, on a scale from 1 to 7) had a moderate effect on the risk of culling compared with other factors but were still influential on survival, productive life expectancy, and annual replacement rate. Sows with less than 13 good teats had 1.35 times greater risk of being culled than sows with more good teats (P < 0.05). Sows with an X-O rear leg score of 2 had 1.4 times greater risk of being culled than sows with an intermediate score of 4 (P < 0.05). Sows at the optimum score of 4 for the size of inner claws of the rear leg had 0.83 times less risk of being culled (P < 0.01) than sows with scores of 2 and 3. Furthermore, when a phenotypic index for feet and legs was used to group these variables, the effect was highly significant (P < 0.001). Therefore, a means to improve longevity is through phenotypic selection of replacement gilts based on exterior traits: gilts with 13 or less good teats or with extreme feet and leg scores should be culled. From a genetic point of view, sows with the best value in the current index for exterior traits had a lower risk of culling (P < 0.01), and therefore, it is possible to obtain a response for sow longevity via indirect selection for exterior traits. From 1999 to 2003, the trend has been to eliminate extreme animals on exterior traits. This may partly explain the improvement of sow length of productive life longevity from 560 d in 2000 to nearly 710 d in 2003 observed in the data set.     

Sow removal in Swedish commercial herds

The objective of this study was to describe the sow removal pattern in Swedish commercial piglet producing herds, with group-housing of non-lactating sows. The data collection, based on a PC herd monitoring program used in 21 piglet producing herds in the south-central part of Sweden, was prospective, started in 2002 and continued for 3 years. During this period, information on 14 234 removed sows was recorded. For all parameters studied a large variation between herds was found. The average annual removal rate was 49.5% (range 33.6–66.3%). Among the removed sows, 85.2% were sent to slaughter, 10.5% were euthanised and 4.3% were found dead. The most common removal reasons were ‘reproductive disorders’ (26.9%), ‘old age’ (18.7%) and ‘udder problems’ (18.1%), followed by ‘low productivity’ (9.5%), ‘lameness and/or foot lesions’ (8.6%) and ‘traumatic injuries’ (7.1%). The proportion of sows sent to slaughter was higher than the proportion euthanised for all categories of removal except ‘traumatic injuries’ (in which 81.6% of the sows were euthanised). The average parity number at removal for all sows was 4.4. Lowest average parity numbers were found for sows removed due to ‘traumatic injuries’ (2.6). Among removed sows, the proportion removed per parity decreased up to parity 6. Sows removed due to ‘old age’ had the highest piglet production, while sows removed due to reproductive disorders had the highest number of non-productive days (NPD) per parity and the longest interval from last farrowing to removal. With increasing removal parity number, the number of piglets produced increased and NPD decreased. In lower parities (1–3) most sows were removed due to ‘reproductive disorders’, but this proportion fell as parity number rose. Removals due to ‘udder problems’ were most frequent in medium parity numbers (4–6). Most sows removed after parity 7 were removed due to old age. The proportion of the sows found dead was highest just after farrowing; otherwise only a low percentage of sows were removed during the lactation period. The proportion of euthanised sows was high in the week after farrowing and during the 4-week period following weaning. The proportion of sows sent to slaughter increased considerably 4 weeks after farrowing (i.e. after weaning) and stayed high during the subsequent 3 weeks. The study revealed a considerable amount of unplanned removal of young sows. Not only the sows sent to slaughter, but also those euthanised and found dead, must be included in studies on sow removal.     

Culling patterns in selected Minnesota swine breeding herds.

This investigation was conducted to study culling patterns in swine breeding herds. Data were obtained from 89 Minnesota swine breeding herds and included 5918 sows and 1324 gilts for a total of 7242 culled femaled. Each producer was involved for 12 consecutive months. They were asked to record every female that was removed from the herd, the reason for its culling and its parity. The annual culling rate for the sample averaged 50%, but varied considerably between herds ranging from 15% to 85%. Culled females had produced an average of 3.77 litters. Half of the females culled did not produce more than three litters. Reproductive failure accounted for 32% of all removals. The average parity of the females culled in that category was only 2.37: almost 33% were gilts. Failure to conceive represented 75% of all females culled for reproductive failure. Proportionally, culling as a result of anestrus was higher in gilts. It accounted for 33% of all gilts culled for reproductive failure which was twice as much as for sows. Inadequate performance accounted for 17% of all removals. These sows had produced an average of 5.11 litters. These results indicated that few animals were culled on the basis of first litter performance. Old age comprised 14% of all removals and the average parity at culling for this category was 7.11. Death accounted for 12% and the average parity for these females was 3.40. Locomotor problems and peripartum problems were the cause of 28% and 23% of all deaths, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Four-year study of lameness in piglets at a research station

Lameness in piglets up to nine weeks old was studied in a research station herd for four years; 9411 piglets were born alive, of which 9.8 per cent were treated for lameness. In litters born to gilts, 9.9 per cent of the piglets were treated for lameness, in litters born to sows of parity 3, 11.4 per cent of the piglets were treated, but in litters born to sows of parity 4 to 7 the proportion of piglets treated for lameness decreased to about 8 per cent. Around 75 per cent of all cases were observed in piglets less than three weeks old; the incidence risk of lameness decreased from 2.7 per cent during the first week of life to 0.3 per cent after weaning. The average weight of affected piglets was reduced by approximately 8 per cent at nine weeks of age. There was no overall association between lameness and sex or birth weight within sex. The mortality among lame gilts was higher at all ages than among healthy gilts, but among barrows a higher mortality was observed only during the late suckling period. Litters with 12 or more piglets had a higher incidence of lameness. Clinical signs of disease in the sow and whether the piglets were given an intramuscular injection of 200 mg of iron on their second, third or fourth day of life had no effect on the incidence of lameness.     

National Pork Producers Council Maternal Line National Genetic Evaluation Program: a comparison of sow longevity and trait associations with sow longevity

Data from the National Pork Producers Council Maternal Line National Genetic Evaluation Program were used to compare longevity of sows from 6 commercial genetic lines and to estimate the phenotypic associations of sow longevity with gilt backfat thickness, ADG, age at first farrowing, litter size at first farrowing, litter weight at first farrowing, average feed intake during lactation, and average backfat loss during lactation. The lines evaluated were American Diamond Genetics, Danbred North America, Dekalb-Monsanto DK44, Dekalb-Monsanto GPK347, Newsham Hybrids, and National Swine Registry. The data set contained information from 3,251 gilts, of which 17% had censored longevity records (sows lived longer than 6 parities). The line comparison was carried out by analyzing all lines simultaneously. Because the survival distribution functions differed among genetic lines, later analyses were carried out separately for each genetic line. All analyses were based on the non-parametric proportional hazard (Cox model). Dekalb-Monsanto GPK347 sows had a lower risk of being culled than sows from the other lines. Moreover, the shape of the survival distribution function of the Delkab-Monsanto GPK347 line was different from the other 5 lines. The Dekalb-Monsanto 347 line had lower culling rates because they had lower gilt reproductive failure before the first parity than gilts from the other lines. Within line, sows with lower feed intake and greater backfat loss during lactation had a shorter productive lifetime. Thus, producers should implement management practices having positive effects on sow lactation feed intake. Additionally, the swine genetics industry is challenged to simultaneously improve efficiency of gain of their terminal market pigs and to obtain high feed intake during lactation of their maternal lines for future improvement of sow longevity. Recording sow feed intake and backfat loss during lactation in nucleus and multiplication breeding herds should be considered. Between-line differences in this study indicate that it is possible to select for sow longevity, but more research is needed to determine the most efficient selection methods to improve sow longevity.     

A herd management survey on culling guidelines and actual culling practices in three herd groups based on reproductive productivity in Japanese commercial swine herds

The objective of the present study was to investigate culling guidelines for gilts and sows in Japanese commercial herds and to compare differences between culling guidelines and actual culling practices in different herd productivity groups. A questionnaire survey was undertaken to obtain information on culling guidelines in 115 commercial swine herds that participated in the PigCHAMP data-share program. The questionnaire included questions on guideline values for culling intervals and the number of conception failure occurrences that would trigger a culling decision to be made. Ninety-two of the 115 herds (80.0%) returned appropriate data for the study and were included in the present study. In addition to questionnaire data, culling data regarding the actual culling intervals and number of reservices for gilts and sows culled during 2007 to 2008 were also obtained for the same herds from a PigCHAMP database. Culled gilts and sows were divided into 4 female groups on the basis of the stages of their reproductive life when they were culled: unmated gilts, mated gilts, unmated sows, and mated sows. Culling intervals in unmated gilts and sows were defined as the number of days from birth or weaning to culling, respectively, whereas in mated gilts and sows culling intervals were the number of days from last service to culling. Three herd productivity groups were formed on the basis of the upper and lower 25th percentiles of pigs weaned mated female(-1)·yr(-1):high-,intermediate- or low-performing herds. For unmated gilts and sows actual culling intervals were 15 d shorter than the guideline culling intervals in the surveyed data submitted by producers (P < 0.05). This shorter actual culling period for unmated gilts and sows did not vary significantly between herd productivity groups in any parity. However, for mated gilts and sows the actual culling intervals were at least 30 d longer than the guideline culling intervals (P < 0.05). Guideline and actual culling intervals for mated gilts and sows were at least 10 d shorter in high-performing herds than in low-performing herds (P < 0.05). High-performing herds had lower proportions of sows culled after the second reservice than intermediate- or low-performing herds in parity groups 0 to 5 (P < 0.05). In conclusion, culling guidelines for mated sows differed between herd productivity groups, and culling guidelines for mated gilts and sows were not strictly followed in any herd group in the commercial herds.     

Reproductive performance in gilts through their first two parities

Fertility data were collected for 766 gilts from 12 breeding and commercial herds. The age at first breeding was 244.5 days and at first farrowing 363.2 days. The litter size was 9.91 piglets born (9.16 live). The farrowing rate at the first service was 87.8%. The total farrowing rate was 95.5% of the mated gilts and 88.4% of all the gilts. 9.8% were repeat breeders. 2.6% of the once mated gilts never returned to oestrus and still did not farrow. The culling rate was 11.6%. The major reason for culling was delayed puberty/anoestrus (7.7%). Of the 565 gilts having a first litter 85.3% were mated after weaning. The age at second farrowing was 541.7 days. The litter size was 10.9 piglets born (10.3 live). The farrowing rate after first service was 83.0%. The total farrowing rate of the 482 sows was 92.9% and of the 565 weaned sows 79.3%. 12.2% were repeat breeders. 4.8% of the sows once mated never returned to oestrus and still did not farrow. The culling rate was 20.7%. Culling because of anoestrus was 4.4%. The month of birth significantly influenced the number of gilts culled because of anoestrus, the age at first breeding and at first and second farrowing. The season also influenced the interval from weaning to service, the percentage of sows served within 7 days of weaning and culled because of anoestrus. No correlation between a high ultrasonic index and lowered fertility was found. The age at first breeding was 1.12 days younger per unit higher ultra-sonic index.     

Accuracy of sow culling classifications reported by lay personnel on commercial swine farms

OBJECTIVE: To determine the accuracy of sow culling classifications reported by lay personnel on commercial swine farms. DESIGN: Retrospective cohort study. ANIMALS: A convenience sample of 923 sows from 8 conventional, farrow-to-wean farms that followed standard operating procedures. PROCEDURES: Sows were examined at slaughter, and lesions were recorded. Individual production records were reviewed to determine the farm-reported reason for culling the sows, and criteria were developed to assess the accuracy of recorded culling classifications. RESULTS: For 209 of the 923 (23%) sows, the farm-reported culling classification was judged to be inaccurate. The culling code was considered to be inaccurate for 62 of 322 (19%) sows reportedly culled because of old age, 48 of 172 (28%) sows reportedly culled because of failure to conceive, 31 of 90 (34%) sows reportedly culled because of poor body condition, and 23 of 73 (32%) sows reportedly culled because of poor farrowing productivity. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that for commercial swine farms, farm-reported culling code classifications were frequently inaccurate. This degree of inaccuracy may cause severe limitations for studies that rely on farm-reported assessments of clinical conditions.     

Lameness and fertility of sows and gilts in randomly selected loose-housed herds in Finland

The prevalence of lameness among 646 sows and gilts in 21 selected herds was determined; 8.8 per cent of the animals were lame and the most common clinical diagnoses were osteochondrosis, infected skin lesions and claw lesions. The lame animals had higher serum concentrations of haptoglobin and C-reactive protein than the sound animals. Animals housed on slatted floors had twice the odds of being lame and 3.7 times the odds of being severely lame than animals housed on solid floors. Yorkshire pigs had 2.7 times the odds of being lame than Landrace or crossbred animals. Higher parity and the use of roughage decreased the odds of the sows not becoming pregnant; however, lameness was not a risk factor for non-pregnancy.     

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.     

Phenotypic and genetic variation in longevity of Polish Landrace sows

The influence of some production traits on the longevity of Polish Landrace sows was evaluated using survival analysis. Estimates of genetic parameters were obtained from the sire and animal components in linear and survival methodologies. Comparison between survival and linear models was based on heritabilities and ranking of estimated breeding values of sires. The same data set, 13 031 sows, was used for both methodologies, even in the presence of censored observations. The effects of herd*year and year*season of the first farrowing had the largest influence on the risk of culling of sows. Sows born in spring season (March–May) had a 24% (p < 0.001) lower hazard for removal than those born in winter (December–February). The age at first farrowing had a small but significant effect on culling: the hazard regression coefficient for this trait was 0.002 per day. Sows that had more piglets born alive and fewer stillborn in the first litter had a decreased risk of being culled. Within a contemporary group, slower growing gilts had decreased removal risk. The relative risk ratios show a marginal decreased rate of culling for sows with backfat thickness between 9.5 and 11 mm compared to the leaner sows. Loin depth had no effect on sow longevity. Heritability estimates ranged from 0.09 to 0.38 depending on the model and type of analysis. In survival analysis, all heritabilities for longevity were higher when analysed with sire models (0.21 and 0.38) compared to animal models (0.09 and 0.16). The use of animal or sire models in the linear analysis gave similar heritability estimates (0.12 and 0.10). Correlations between breeding values for sires were moderate and high, with absolute values from 0.51 to 0.99, depending on the model fitted and methodology. A stronger correlations within methodologies (0.83–0.99) than within models with different methodologies (0.51–0.63) were obtained.     

Causes of culling and death in sows.

Over a 4-year period, the annual number of culled sows in 9 Danish herds averaged 54.8 per cent of the year-sows and the number of culled sows in per cent of total number of farrowings averaged 25.8 (Table I). -- The culling rate varied considerably from herd to herd within the same year and from year to year (Tables I and II); however, the average annual culling rate for all the herds only presented small variations (Table II). The average number of litters reared per sow before culling was 3.6. The culling rate was higher in pedigree herds than in commercial herds, and it was highest in the small pedigree herds (Table III). The hygiene level in the herds and the introduction of new female breeding stock did not influence the culling rate (Table IV). A proportionally lower percentage of the sows was culled in herds where the dry and pregnant sows were housed in stalls and/or were tethered, as compared to herds where these sows were housed in pens (Table V). -- The culling rate in the age groups of sows with less than 8 farrowings remained at approximately the same level (Table VI). The main reason for culling was infertility problems, which were recorded in 41.4 per cent of the culled sows, while 16.7 per cent of the sows were culled because their litters were poor and/or small (Table VII). The mortality rate among the culled sows was 11.9 (Table VII), and the main causes of death were chronic pyogenic infections, which occurred in 25.5 per cent of the fatal cases (Table VIII). Certain aspects concerning the recording and calculation of culling rates in the different herds are discussed and it is emphasized that the culling rate per se may not have any direct relationship to the productivity in the herd.     

Genetic analysis for sow stayability at different parities in purebred Landrace and Large White pigs

Genetic parameters for sow stayability were estimated from farrowing records of 10,295 Landrace sows and 8192 Large White sows. The record for sow stayability from parity k to parity k + 1 (k = 1, …, 6) was 0 when a sow had a farrowing record at parity k but not at parity k + 1, and 1 when a sow had both records. Heritability was estimated by using single-trait linear and threshold animal models. Genetic correlations among parities were estimated by using two-trait linear–linear and single-trait random regression linear animal models. Genetic correlations with litter traits at birth were estimated by using a two-trait linear–linear animal model. Heritability estimates by linear model analysis were low (0.065–0.119 in Landrace & 0.061–0.157 in Large White); those by threshold model analysis were higher (0.136–0.200 & 0.110–0.283). Genetic correlations among parities differed between breeds and models. Genetic correlation between sow stayability and number born alive was positive in many cases, implying that selection for number born alive does not reduce sow stayability. The results seem to be affected by decisions on culling made by farmers.     

Association between limb conformation and retention of sows through the second parity

OBJECTIVE: To determine the association between limb conformation scores in gilts and retention through the second parity. ANIMALS: 961 gilts. PROCEDURE: Gilts were monitored for 1 year. Baseline data recorded were conformation scores for the forelimbs and hind limbs and backfat thickness. Primary outcome was time to removal from a herd, and the secondary outcome was time to removal as a result of lameness. RESULTS: 662 of 961 (68.89%) females remained in herds through the second parity, whereas 299 (31.11%) were removed before the second parity. Survival time for females on the basis of conformation scores for the forelimbs and hind limbs differed significantly for total sow removals and removals as a result of lameness. Females with poor conformation scores for the hind limbs had an increased risk of being removed, compared with risk for females with better conformation scores. Risk of removal specifically as a result of lameness increased as conformation score for the hind limbs became poorer. Proportion of the total population that was removed and could be attributed to undesirable limb conformation was 16.13% for forelimbs and 12.90% for hind limbs. CONCLUSIONS AND CLINICAL RELEVANCE: Females with undesirable conformation were removed earlier than females with desirable conformation. This was particularly true for females with low conformation scores for the hind limbs. Selection of gilts on the basis of limb conformation may result in reduced attrition of females and improved performance of herds over time.     

Impact of biological and economic variables on optimal parity for replacement in swine breed-to-wean herds

Voluntary and involuntary culling practices determine the average parity when sows are replaced in a herd. Underlying these practices is the economic effect of replacing a sow at different parities. A dynamic programming model was used to find the optimal parity and net present value in breed-to-wean swine herds. The model included income and costs per parity weighted by the discount rate and sow removal rate. Three scenarios that reflect a wide range of cases were considered: low removal rates per parity with no salvage value (LRNS), high removal rates per parity with no salvage value (HRNS), and high removal rates per parity with a percentage of the sows having a salvage value (HRYS). The optimal parity of replacement for the base biological and economic conditions was 4 and 5 parities in the high and low removal scenarios, respectively. Sensitivity analyses identified the variables influencing the optimal replacement parity. Optimal parity of replacement ranged from 3 to 7 parities in the low replacement scenario, compared with 1 to 5 parities in the high replacement scenarios. Sow replacement cost and salvage value had the greatest impact on optimal parity of replacement followed by revenues per piglet weaned. The discount rate and number of parities per year generally had little influence on optimal parity. For situations with high sow costs, low salvage values, and low revenues per piglet, the optimal parity at removal was as high as 6 to 10 parities, and for situations with low sow cost, high salvage values, and high revenues per piglet, the optimal parity at removal was as low as 1 to 2 parities depending on removal rates. The modified internal rate of return suggested that, for most LRNS and HRYS scenarios considered, investment in a swine breed-to-wean enterprise was favored over other investments involving a similar risk profile. Our results indicate that in US breeding herds, sows are culled on average near the optimal parity of 4. However, the optimization process should be a dynamic one that adapts to changes in replacement rates, salvage value, replacement cost, and revenues per piglet.