Cost benefit analysis of automatic lameness detection systems in dairy herds: A dynamic programming approach.

Epidemiological data establish that lameness is second only to mastitis as the dairy industry's most prevalent and costly animal welfare issue. Using an automatic lameness detection (ALD) system in which continuous, accurate detection is coupled with proper treatment, is key for reducing economic losses due to lameness. It is reasonable to assume that the cost of lameness would vary with its severity. Therefore, our first objective was to estimate the cost of different lameness severity levels as a function of milk production, lameness risk, conception probability, and treatment cost using a dynamic programming (DP) model. Our second objective was to conduct a cost benefit analysis for ALD systems which can reduce production losses through early detection and treatment of lameness, when compared to visual-detection (VD; i.e., performed by humans) systems. The default production loss parameters for the VD system used as inputs to the DP model were either sourced from the literature or were estimated based on data from a field trial. The production loss parameters for the ALD system used as inputs to the DP model were based on extrapolations of parameter values used for the VD system. The profit per present cow per year under assumed expenses and revenues decreased from $426.05 (when lameness incidence was assumed to be 0%) to $389.69 when lameness incidence was 19.5 %. Out of the 19.5 % lameness incidence in our default scenario, 9.8 % were moderate cases and 9.7 % were severe cases. Average cost of lameness was $36.36 at 19.5 % incidence. Average cost of lameness increased with increased incidence and was respectively $82.05, $195.05, and $286.87 at the low, medium, and high incidence scenarios. We used an operational framework which compared the lameness costs between the VD and ALD systems with 25 %, 50 % and 75 % net avoided costs (NAC) for the 10 year lifespan of the ALD system, at default, low, medium and high lameness incidence scenarios. The net return per cow per year from using an ALD system over a VD system was $13, at low incidence and 25 % NAC. The net return per cow per year for the ALD system was as high as $99 at high incidence and 75 % NAC. Out of 351 (3 system prices, 3 system efficiencies, 3 levels of lameness incidence and 13 different herd sizes) scenarios tested, 295 resulted in a net profit within the system lifespan of 10 years, thus justifying the investment in ALD systems.

Early life indicators predict mortality, illness, reduced welfare and carcass characteristics in finisher pigs.

The objective of this study was to investigate associations between early life indicators, lactation management factors and subsequent mortality, health, welfare and carcass traits of offspring. A total of 1016 pigs from a batch born during one week were used. During lactation, number of liveborn piglets, stillborn and mummies, sow parity, number of times cross-fostered, weaning age, birth and weaning body weight (BW) were collected. Mortality was recorded throughout the offspring production cycle. Prior to slaughter, pigs were scored for lameness (1=non-lame to 3=severely lame). At slaughter, tail lesions were scored (0=no lesion to 4=severe lesion) and cold carcass weight (CCW), lean meat%, presence of pericarditis and heart condemnations were recorded. Additionally, lungs were scored for pleurisy (0=no lesions to 4=severely extended lesions) and enzootic pneumonia (EP) like lesions. There was an increased risk of lameness prior to slaughter for pigs born to first parity sows (P<0.05) compared with pigs born to older sows. Sow parity was a source of variation for cold carcass weight (P<0.05) and lean meat% (P<0.05). Pigs born in litters with more liveborn pigs were at greater risk of death and to be lame prior to slaughter (P<0.05). Pigs that were cross-fostered once were 11.69 times, and those that were cross-fostered ≥2 times were 7.28, times more likely to die compared with pigs that were not cross-fostered (P<0.05). Further, pigs that were cross-fostered once were at greater risk of pericarditis and heart condemnations compared with pigs that were not cross-fostered (P<0.05). Pigs with a birth BW of <0.95kg were at higher mortality risk throughout the production cycle. There was an increased risk of lameness, pleurisy, pericarditis and heart condemnations (P<0.05) for pigs with lower weaning weights. Additionally, heavier pigs at weaning also had higher carcass weights (P<0.05). There was an increased risk of lameness for pigs weaned at a younger age (P<0.05). Males were 2.27 times less likely to receive a score of zero for tail biting compared with female pigs. Results from this study highlight the complex relationship between management, performance and disease in pigs. They confirm that special attention should be given to lighter weight pigs and pigs born to first parity sows and that cross-fostering should be minimised.

What's New in Old Horses? Postmortem Diagnoses in Mature and Aged Equids.

Postmortem findings in 241 equids admitted to a teaching hospital that were at least 15 years old at autopsy were reviewed (1) to determine disease prevalence, (2) to compare the cause of death (or euthanasia) in equids 15 to 19 years of age (n = 116) with that in equids ≥20 years of age (n = 125), and (3) to catalog coexisting lesions in equids with pituitary pars intermedia dysfunction (PPID). Breed and sex were evenly distributed between the age groups. Death or euthanasia was attributed to disease of the digestive system (41.5%), pituitary gland (12.9%), locomotor system (10.0%), nervous system (7.9%), cardiovascular system (4.6%), urinary system (4.6%), reproductive system (4.2%), respiratory system (4.2%), integumentary system (4.2%), lymphoid system (2.5%), liver (2.5%), or systemic neoplasia (1.2%). Nervous system disease was more common in the 15- to 19-year group; urinary tract disease was more common in the ≥20-year group. Neoplastic disease, regardless of systemic location, was the basis for death or euthanasia in 18.7% of all equids. Squamous cell carcinoma, lymphoma, and melanoma were the most common malignant neoplasms. PPID was the most common specific diagnosis, based on the postmortem presence of hyperplasia or adenoma, and was the reason for euthanasia in 47.7% of 65 equids with PPID. The most common nonpituitary causes for death or euthanasia in equids with PPID were colic, lameness, cancer, and spinal cord disease. Coexisting conditions in equids with PPID that were not considered the basis for euthanasia included neoplasms, infections, lameness, and recurrent airway obstruction.

Severity and outcome of equine pasture-associated laminitis managed in first opinion practice in the UK.

Data from 107 cases of pasture-associated laminitis were obtained from first opinion practices to study factors associated with severity, survival and return to ridden exercise. There were 43 mares and 64 geldings, with a median age of 11 years. Of the 107 animals, 33 were small ponies, 45 were large ponies/cobs, 17 were small horses and 12 were large horses. Ninety-seven animals were categorised as having laminitis as defined by Cripps and Eustace (1999): 76 had mild (Obel grade 1 or 2) laminitis and 31 had severe (Obel grade 3 or 4) laminitis. Forty-three animals had previously had laminitis, and were significantly less likely (P=0.02) to have severe laminitis than those that had not. Eighty-nine animals were overweight, and there was a trend (P=0.09) towards severe laminitis cases having a higher body mass index. Eight weeks after disease onset, 102 animals were alive. Lower bodyweight, optimal body condition, mild laminitis and category of acute/chronic founder as defined by Cripps and Eustace (1999) were significantly associated with survival. There was a trend (P=0.06) towards treatment with acepromazine being associated with survival. Of the 81 animals that were used for riding, 48 were being ridden again; this was 2.6 times more likely in animals without previous laminitis. The clinical outcome was judged by a panel of three veterinarians as 'good' in 77 of 107 of cases. Clinical outcome was significantly associated (P=0.03) with horse type: the outcome was 'bad' in none of the small horses, compared with 15 of 45 large ponies/cobs, 11 of 33 small ponies and three of 12 large horses.

Prognostic indicators of poor outcome in horses with laminitis at a tertiary care hospital.

This retrospective study investigated the factors associated with a poor outcome (death by euthanasia or from other causes) in horses treated for laminitis at a tertiary care hospital. Cases (n = 247) were defined as patients with laminitis that were euthanized or that died of other causes during hospitalization. Controls (n = 344) were patients with laminitis that survived to be discharged from the hospital. In the final multivariate analysis, the factors significantly associated with an increased risk for death and their respective odds ratios (OR) were as follows: Thoroughbred (OR = 1.57); racehorse (OR = 1.76); treatment with flunixin meglumine (OR = 1.76); vascular pathology (OR = 2.12); distal displacement of the third phalanx (OR = 2.68); pneumonia (OR = 2.87); and lameness of Obel grade II (OR = 2.99), grade III (OR = 9.63), or grade IV (OR = 20.48). The use of glue-on shoes significantly reduced the risk for death (OR = 0.36).

Effect of lameness on sow longevity.

OBJECTIVE: To analyze the association of lameness and performance variables on sow longevity by use of time-to-event analysis. DESIGN: Cohort study. ANIMALS: 674 sows from a commercial breeding herd. PROCEDURES: A lameness assessment was performed on each sow. Data on farrowing performance and longevity were collected for the sows during 3 or fewer parities from the database of the herd during 2005 and 2006. The association of risk factors with sow longevity within 350 days after lameness assessment was analyzed via Cox regression analysis. Pigs per day, total production days, and survival at 350 days after lameness evaluation were compared between lame and nonlame sows. RESULTS: Numbers of preweaning baby pig deaths, stillborn pigs, and mummified pigs were negatively associated with sow longevity within 350 days after lameness assessment. A higher number of pigs born alive and younger parity of sows were protective. Lame sows had a higher risk (1.710 times as high) of removal from the herd within 350 days after lameness assessment. The number of pigs born alive per day, survival of sows at 350 days, and total number of days in the herd were lower in lame sows. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study indicated significant differences in the survivability of lame and nonlame sows in a commercial herd. Parity and farrowing performance variables were factors influencing sow longevity in this herd. Producers need to minimize sow lameness and remove lame sows from a herd early (when treatment is not an option) to minimize economic loss.

Clinical and morphological investigations on the prevalence of lameness associated with femoral head necrosis in broilers.

1. The aim was to determine the prevalence of femoral head necrosis (FHN) as a cause of lameness in broilers, and to increase knowledge of its morphological features and aetiology. The studies were carried out in two farms (A and B) in Bulgaria, on 650,000 chickens from 38 flocks. 2. Lameness in broilers varied from 3-4% up to 15% for both farms. In affected flocks, mortality due to lameness ranged between 5-6% and 10%. 3. We documented lesions in 520 broilers with signs of lameness. Samples for histopathological examination were obtained from the femur--135 from farm A and 120 from farm B. The samples originated from different batches of broilers, during different seasons of the year, and from chickens originating from parent flocks of different ages. 4. E. coli was isolated in more than 90% of the bacteriologically tested samples with FHN associated with osteomyelitis. Our large-scale field tests showed that FHN was the commonest cause of lameness in broilers.

Analysis of morbidity and mortality data in riding school horses, with special regard to locomotor problems.

The incidence of disease, mortality and survival of horses, focusing on locomotor problems, at riding schools were studied, using data from an animal insurance database during 1997-2002. In total 5140 horses from 136 riding schools were included in the analysis. The overall yearly incidence rate (IR) was 1584 events of veterinary care per 10,000 horse-years at risk (HYAR). The total and diagnostic mortalities were 790 and 763 deaths per 10,000 HYAR. Rates varied substantially among riding schools. For locomotor problems the rates were 1116 events of veterinary care and 524 deaths per 10,000 HYAR. Multivariable Cox proportional-hazards analysis was performed on horses enrolled in insurance during the study period, including riding schools as frailty effects. For the outcome veterinary care for locomotor problems, the hazard ratios (HR) increased with increasing life-insurance value and Swedish warmbloods and other horses had increased HR compared to ponies. In the model with outcome life claim because of locomotor problems the breed groups Swedish warmblood and other horses also had higher HR than ponies. Age at entry > or = 8 years was associated with decreased HR for settled life-insurance cases due to locomotor problems and the two highest categories for insurance value had increased HR compared to the two lower categories. In the model with the outcome life claim because of previously claimed locomotor problems Swedish warmbloods had a higher HR than other horses and ponies. The HR increased by 33% for each year of age at entry. In south-urban areas of Sweden the HR was decreased compared to in all other areas, including baseline. Overall riding schools utilised the insurance more compared to all horses in the insurance database ( approximately 22% for the veterinary-care insurance and approximately 79% for the settled life insurance).

Livestock disease threats associated with intensification of pastoral dairy farming.

This paper provides an overview of the changes in the pasture-based dairy systems of New Zealand and Australia that may influence the health of cattle. There are relatively few available data that can be used to quantify the effects of increased intensification of milk production on the health of cattle. There is evidence that increased production increases the risk of mastitis and culling for udder health. Increased risks of mastitis with treatment with somatotropin support these findings; however, the risk of mastitis may decrease with increased milking frequency. Larger herds with greater stocking density should increase the risk for infectious disease, but evidence to support this contention is sparse. Very intensive grazing patterns associated with higher grass yields achieved using better cultivars and greater use of fertilisers favour nematode parasites. There is some evidence of anthelmintic resistance in both nematodes and liver fluke. Veterinarians will need to be aware of the potential for these to reduce the productivity of cattle. There have been benefits of improved nutrition on the efficiency of energy use for dairy production. Diseases such as bloat and ketosis appear to be of lower prevalence. It also appears that mineral nutrition of pasture-fed cattle is being better addressed, with gains in the control of milk fever, hypomagnesaemia and trace-element deficiencies. However, acidosis is a condition with a high point prevalence in pasture-based dairy systems where cows are fed supplements; one study in Australia found a point prevalence of approximately 11% of cows with acidosis. There is evidence from this study that the neutral detergent fibre (NDF) in pasture-based diets may need to be higher than 30% of the diet to maintain rumen stability. Laminitis and acidosis are different conditions with a similar pathogenesis, specifically highly fermentable diets. The prevalence of lameness was 28% in herds in Australia, suggesting that this condition must be a focus for preventive medical approaches, including the design of laneways, feed pads and dairies.

Factors affecting length of productive life in Swedish commercial sows.

The objective of this study was to investigate factors that might influence the length of productive life in Swedish crossbred (Landrace x Yorkshire) sows. The data set consisted of 20,310 sows farrowing between 2001 and 2004 in 21 commercial piglet-producing herds. Productive life (PL) was defined as the number of days between first farrowing and removal or termination of data collection. In addition to the overall risk analysis of PL, another 4 longevity traits were analyzed (competing risk analyses): reproductive disorder-determined length of PL (RPL), udder problem-determined length of PL (UPL), lameness-determined length of PL (LPL), and mortality-determined length of PL (MPL). Analyses were performed by using survival analysis, applying a Weibull model with 6 time-dependent and 1 time-independent variable (age at first farrowing). The factor with the largest contribution to the likelihood function for PL was days after farrowing, followed by parity, the herd x year combination, the total number of piglets born, days between weaning and next farrowing, farrowing month, and age at first farrowing. For all 4 competing risk traits, the factors contributing most to the likelihood function were days after farrowing, the herd x year combination, and parity, with a varied order between traits. The hazard for removal was greatest 30 to 40 d after farrowing (after weaning) for PL, UPL, and LPL (P < 0.001). However, for MPL the hazard was greatest just after farrowing (0 to 10 d), and for RPL the hazard peaked at 70 to 100 d after farrowing. The hazard for removal was, compared with parity 1, less in parities 2 to 7 and greater from parity 8 for PL (P < 0.001). The hazard was greatest in parity 1 (P < 0.01) for RPL, UPL, and LPL, whereas for MPL the hazard increased with greater parity number and was markedly greater from parity 9 (P < 0.001). Sows with litters of 9 piglets or less had a greater hazard for removal than sows with litters of 12 to 13 piglets (P < 0.001). Intervals between 120 and 122 d from weaning to the next farrowing showed the lowest hazard for removal (P < 0.001). The influence of farrowing month displayed no clear pattern for PL. Sows of 14 mo or older at their first farrowing had a 20% greater hazard for removal than younger sows (P < 0.001). The hazard for removal was greater for smaller litters in all parities but was more accentuated in greater parities. Overall, days after farrowing was the main risk factor for sow removal. Removal hazard was greatest shortly after weaning, and this peak increased with greater parity number.

Association between costly veterinary-care events and 5-year survival of Swedish insured warmblooded riding horses.

Our objective was to estimate the 5-year survival to death in insured warmblooded riding horses (as reflected by a life-insurance claim) in horses with or without at least one costly veterinary-care event (VCE) in 1997. We also determined the impacts of gender, age, previous diagnosis of veterinary claim, geographic variables, cost for veterinary claims and life-insurance value upon the survival. The design was a retrospective cohort study using a population of warmblooded riding horses insured in a Swedish animal-insurance company (Agria Insurance, P.O. 70306, SE-107 23 Stockholm, Sweden) in 1997. All horses in this population had insurance both for veterinary-care and life ("complete" insurance reimbursing the insurance holder for most medical problems). We followed two cohorts (2,495 horses with > or = 1 VCE and 15,576 horses with no VCE in year 1997). The median VCE cost in horses with > or =1 VCE was 3,800 SEK, with 10th and 90th percentiles of 1,400 and 11,400 SEK respectively. In total 944 of the 2,495 horses (38%) in the VCE-positive cohort and 2,962 of the 15,576 horses (19%) in the VCE-negative cohort had died (had a settled life-insurance claim) after the follow-up time. An exponential-regression model showed that geldings had a higher risk of claimed death compared to mares and mares had a higher risk compared to stallions. The risk of death increased linearly with age. The risk of death increased with increasing life-insurance value. Horses with previous lameness had the lowest survival, and for high-cost claims this increased risk was not associated with age.

Dairy cow mortality. A review.

We reviewed the literature to give an overview over the mortality among dairy cows in countries with a relatively intensive dairy production. A total of 19 studies focussing on dairy cow mortality were identified. Information about objectives, measures of mortality, sample sizes, study designs, causes of death and risk factors from these studies is presented and discussed. Additionally, recommendations for future recordings of mortality that will enable better possibilities for comparison of study results, generalization of results from a study population to a larger population and meta-analysis are given.

Locomotive disorders associated with sow mortality in Danish pig herds.

Given the increase in sow mortality in Danish pig herds over the last 10 years, we have investigated the causes of spontaneous death and killing of sows, especially those due to locomotive disorders. A total of 265 culled sows (93 spontaneously dead sows and 172 killed sows) from 10 different herds were sent for complete necropsy, and grouped according to primary diagnoses. From 35 of these sows, tissue for histological evaluation and samples for bacteriological cultivation were also collected, and secondary diagnoses and body condition were recorded. The main causes for killing were related to the locomotive system (72%), arthritis (24%) and fractures (16%) being the most frequent lesions. The main causes of spontaneous death were related to the gastrointestinal system and spleen (45%) and the reproductive system (24%). Arthrosis was a secondary diagnosis in 88% of the killed sows and in 92.5% of the spontaneously dead sows. Arcanobacterium pyogenes was the main cause of arthritis. The killed sows had significantly lower body condition compared with spontaneously dead sows. The first two parities and the time around farrowing were associated with the highest mortality in both groups. Hopefully, these observations can guide breeding units attempting to monitor, control and reduce sow mortality.

Evaluation of patterns of removal and associations among culling because of lameness and sow productivity traits in swine breeding herds.

OBJECTIVE: To characterize patterns of removal and evaluate the associations among culling because of lameness and sow productivity traits among culled gilts and sows. DESIGN: Cross-sectional study. SAMPLE POPULATION: Data from a convenience sample of 11 farms pertaining to the removal of 51,795 gilts and sows from January 1991 to December 2002. Mean culling and mortality (death and euthanasia) rates for all inventoried gilts and sows ranged from 23% to 50% and 4.7% to 9.5%, respectively. PROCEDURE: An analysis of categories of removal (cull, death, or euthanasia) and reasons for removal of gilts and sows was performed. Multivariate logistic regression was used to determine associations among culling because of lameness and sow productivity traits among culled gilts and sows. RESULTS: Among sows that were removed, the proportion of parity > or = 1 sows that died (both death and euthanasia) was > 3 times the proportion of parity > or = 1 sows that were culled within 20 days after farrowing. Among lame sows that were removed, the proportion of parity > or = 1 sows that died (death and euthanasia) was higher than the proportion of parity > or = 1 sows that were culled within 20 days after farrowing. Among sows that were removed, the proportion of sows that died (deaths and euthanasia) was higher during lactation than nonlactation. This was also observed among lame sows that were removed. CONCLUSIONS AND CLINICAL RELEVANCE: The proportion of death among removed sows, especially lame sows, was higher during lactation than nonlactation. Results indicated that risk of death is not the same for sows throughout their lifetime.

Effect of lameness on culling in dairy cows.

The purpose of this study was to assess the effect of lameness on dairy cow survival. Cox's proportional hazards regression models were fitted to single-lactation data from 2520 cows in 2 New York State dairy herds. Models were controlled for the time-independent effects of parity, projected milk yield, and calving season, and for the time-dependent effects of lameness and culling. Other common diseases were found to be nonconfounding and so were not included in any of the final models. Survival was measured as the time from calving until death or sale. Cows were censored if they reached the start of the next lactation or end of the study, whichever occurred first. All models were stratified by herd. For all lameness diagnoses combined, survival in the herd decreased for those cows becoming lame during the first half of lactation, with a hazard ratio of up to 2 times that of a nonlame cow. Foot rot diagnosed during the second or third months of lactation decreased survival during the same time period (hazard ratio=5.1; 95% confidence interval=1.6 to 16.2). Sole ulcers diagnosed in the first 4 mo of lactation decreased survival in several subsequent periods in which the strongest association was between diagnosis in the third and fourth months of lactation and exit from the herd during that same period (hazard ratio=2.7; 95% confidence interval=1.3 to 6.0). Foot warts were not associated with decreased survival in this analysis. Lameness was never associated with increased survival in any of the models.

Mortality (including euthanasia) among Danish dairy cows (1990-2001).

Mortality among Danish dairy cows was examined using data from the Danish Cattle Database (DCD) and a questionnaire survey. Mortality risk has increased from approximately 2% in 1990 to approximately 3.5% in 1999. The increased mortality was seen for all dairy breeds and all age groups. Mortality among older dairy cows (parity 3 and older) was approximately twice the mortality among younger cows. 30-40% of deaths were during the first 30 days of the lactation. Approximately, 58% of dead dairy cows had been euthanised. Replies from the questionnaire indicate that the proportion of euthanised cows has increased in the past 5 years. In 86% of all deaths (questionnaire survey) a primary reason could be identified; 25% were for locomotor disorders.

Culling rate of Icelandic horses due to bone spavin.

A survival analysis was used to compare the culling rate of Icelandic horses due to the presence of radiographic and clinical signs of bone spavin. A follow-up study of 508 horses from a survey five years earlier was performed. In the original survey 46% of the horses had radiographic signs of bone spavin (RS) and/or lameness after flexion test of the tarsus. The horse owners were interviewed by telephone. The owners were asked if the horses were still used for riding and if not, they were regarded as culled. The owners were then asked when and why the horses were culled. During the 5 years, 98 horses had been culled, 151 had been withdrawn (sold or selected for breeding) and 259 were still used for riding. Hind limb lameness (HLL) was the most common reason for culling (n = 42). The rate of culling was low up to the age of II years, when it rose to 0.05 for horses with RS. The risk ratio for culling was twice as high for horses with RS compared with horses without RS and 5.5 times higher for culling because of HLL. The risk of culling (prognostic value) was highest for the combination of RS with lameness after flexion test, next highest for RS and lowest for lameness after flexion test as the only finding. It was concluded that bone spavin affects the duration of use of Icelandic horses and is the most common cause of culling due to disease of riding horses in the age range of 7-17 years.

The Michigan equine monitoring system. II. Frequencies and impact of selected health problems.

A prospective study was designed to document the frequencies of equine health problems in the state of Michigan, USA. A total of 2469 horses from a random sample of 138 equine operations were monitored in the study in two 12-month periods: 1992-1993 and 1993-1994. All the major breeds of horses in the state were proportionately represented in the sample. Using weighted annual incidence densities as measures of disease frequencies, the 10 most frequently observed groups of health problems were (from most to least frequent) leg lameness, dermatological problems, respiratory problems, hoof and foot problems, reproductive problems, systemic problems, colic, whole body lameness, neurological problems and gastrointestinal problems (other than colic). This ranking of the top 10 health problems was different from the ranking provided by equine owners/operators at the beginning of the study. Overall, very low specific mortality rates were observed in the study. However, the conditions that were associated with mortality resulted in fairly high case fatalities. The five specific illnesses that most commonly resulted in fatalities were (from greatest to least case fatality risk) systemic problems, colic, gastrointestinal problems (other than colic), neurological problems, and foot and hoof problems. Impact of disease was evaluated in terms of average duration of a case and days lost for performance. Neurological problems, lameness and dermatological problems had the longest duration per case. Neurological problems, lameness, respiratory problems and gastrointestinal problems (other than colic) had the longest average days lost per case.

Culling in 50 dairy herds in England.

A survey of 50 Friesian/Holstein dairy herds (average size 178 cows) in England investigated the rate of culling and the reasons for disposal and death over three years from 1990 to 1992. The average total annual culling rate was 23.8 per cent (22.0 per cent sold and 1.8 per cent died). Of the disposals, 54 per cent were culled by the end of their fourth lactation. Poor fertility was the most important reason for culling (36.5 per cent of disposals), followed by management policy (11.5 per cent), mastitis (10.1 per cent), bovine spongiform encephalopathy (BSE) (7.4 per cent) and lameness (5.6 per cent). The most common causes of death were mastitis (8.9 per cent) and BSE (11.5 per cent), but 46 per cent died for unknown reasons.

Causes of mortality among sows in Danish pig herds.

The likely causes of sow mortality in Danish pig herds were investigated in a sample of 598 of the breeding animals delivered to a large rendering plant in the winter seasons of 1992 and 1993. In 263 cases information about the circumstances of the death or euthanasia and the herd characteristics were available, including the size of the herd, its health status, the age at weaning, the method of feeding and the use of straw for bedding. For these animals the distribution of likely causes of death or euthanasia was: leg weakness, 28.5 per cent; problems related to farrowing and late pregnancy, 20.9 per cent; disorders of the digestive system, 17.1 per cent; disorders of the urinary system, 13.1 per cent; physical injuries, 10.7 per cent; and other disorders, 9.5 per cent. For the other 335 sows the distribution of likely causes of death was: leg weakness, 16.1 per cent; problems related to farrowing and late pregnancy, 10.7 per cent; disorders of the digestive system, 21.2 per cent; disorders of the urinary system, 15.2 per cent; other disorders, 15.0 per cent; and unknown causes of death, 21.8 per cent. According to the official statistics from Danish rendering plants, more than 60,000 carcases of breeding pigs were processed during 1992, corresponding to a mortality rate of 5 to 6 per cent in the sow herds. The mortality rate appeared to increase with increasing herd size, and in herds with more than 100 sows the mortality rate was three times the mortality in herds with fewer than 50 sows. Compared with previous reports, the proportion of disorders involving the gastrointestinal system has increased during the past 20 years. Gastric dilation is particularly common, probably as a result of the intensification of pig production and the associated changes in management practises. The use of straw bedding was marginally significant (P = 0.06) and associated with a low frequency of gastrointestinal disorders.