Teat Injuries Research Articles

Cross-sectional study of Streptococcus species in quarter milk samples of dairy cows in the canton of Bern, Switzerland

A total of 2538 quarter milk samples from 638 lactating dairy cows from 47 farms in the canton of Bern, Switzerland, were investigated for streptococci. A novel, simple and inexpensive...

Housing system and herd size interactions in Norwegian dairy herds; associations with performance and disease incidence

BackgroundAccording to the Norwegian animal welfare regulations, it has been forbidden to build new tie-stall barns since the end of 2004. Previous studies have shown that cow performance and health differ between housing systems. The interaction between housing system and herd size with respect to performance and disease incidence has not been evaluated.MethodsCow performance and health in 620 herds housed in free-stall barns were compared with in 192 herds housed in tie-stall barns based on a mail survey and data from the Norwegian Dairy Herd Recording and Cattle Health Systems. The housing systems herds were comparable with respect to herd size (15-55 cows). Associations between performance/disease incidence and housing system, herd size and year of building the cow barn were tested in general linear models, and values for fixed herd size of 20 and 50 cows were calculated. On the individual cow level mixed models were run to test the effect of among others housing system and herd size on test-day milk yield, and to evaluate lactation curves in different parities. All cows were of the Norwegian Red Breed.ResultsAverage milk production per cow-year was 134 kg lower in free-stall herd than in tie-stall herds, but in the range 27-45 cows there was no significant difference in yields between the herd categories. In herds with less than 27 cows there were increasingly lower yields in free-stalls, particularly in first parity, whereas the yields were increasingly higher in free-stalls with more than 45 cows.In free-stalls fertility was better, calving interval shorter, and the incidence rate of teat injuries, ketosis, indigestions, anoestrus and cystic ovaries was lower than in tie-stalls. All of these factors were more favourable in estimated 50-cow herds as compared to 20-cow herds. In the larger herd category, bulk milk somatic cell counts were higher, and the incidence rate of mastitis (all cases) and all diseases was lower.ConclusionThis study has shown that there is an interaction between housing system and herd size, and that performance and health is not universally better in small free-stalls than in tie-stalls.

Associations between teat injuries and fistula formation in lactating dairy cows treated with surgery

To determine associations between rate of fistula formation and parity, lactation period, wound age, wound location, and shape of teat injuries in surgically treated teats in dairy cows. Prospective clinical study. 106 lactating dairy cows with teat lacerations. Lacerations were classified via shape, location, and age. Associations between potential risk factors and fistula formation were analyzed. Seasonal distribution, type of injured teat, parity, and days in lactation were determined. Cows with teat injury in their first and second parity had 4.1 times the odds of fistula formation, compared with cows with parity >or= 3. Teats sutured within 48 to 72 hours of injury had 8.3 times the odds of fistula formation, compared with teats sutured within the first 24 hours. Cows in early lactation stage (first 60 days of lactation) were more susceptible to teat injuries. Occurrence of teat injury was greater at the third, fourth, and fifth parity. Season, parity, and lactation period were associated with prevalence of teat injury in lactating dairy cows in a range system. Neither the type of suture material used nor the suturing technique was associated with effects on healing of the operated full-thickness teat wounds. Factors such as parity and age of the wound can be associated with delay in the healing process, which may result in fistula formation.

Results and Evaluation of Thirty Years of Health Recordings in the Norwegian Dairy Cattle Population

The results are based on the Norwegian Cattle Health Recording System, which has been in place for the entire country since 1975. The dairy breeds in Norway consist of 94% Norwegian Red and 4% crossbreeds with Norwegian Red. No other breed consists of more than 0.5% of the total population. During the past 30 yr, there have been 11,563,692 dairy cows within the recording system, corresponding to 8,633,532 cow-years and 8,632,516 calvings. This population consisted of 3,038,675 first-calving cows. Altogether, 8,435,704 different diagnoses were recorded from 4,444,485 different cows each year. The general trend for all recordings was an increase in the incidence rate of all cases from 0.74 per 365 d at risk (cow-year) in 1976 to 1.36 in 1990, and then a decrease to 0.62 in 2002. The corresponding figures for cows treated per cow-year were 0.44 up to a maximum of 0.82, and then a decrease to 0.46 per cow-year in 2002. The most common diseases were acute (severe to moderate) clinical mastitis, chronic (mild) clinical mastitis, ketosis, milk fever, teat injuries, retained placenta, silent heat or anestrous, indigestion, cystic ovaries, and metritis. Clinical mastitis increased from 0.15 cows treated per cow-year in 1975 to 0.44 in 1994, and then decreased to 0.23 in 2002. Ketosis began at 0.10 in 1975, increased to 0.24 in 1985, and then decreased to 0.05 in 2005. For several of the most common diseases, there was a reduction of more than 50% from the 1990s to the years after 2000. Validation processes confirmed that this fluctuation reflected the general trend in the population. The disease recording system also reflected the known outbreaks of bovine respiratory syncytial virus during 1976, 1989 to 1990, and 1995. A marked increase in malformation diagnoses could be seen in 1986 and in 1989 and 1990. These could be related to the Chernobyl nuclear power plant accident in April 1986. The diagnosis that showed the most stability throughout these 30 yr was retained placenta. The 3 main reasons for the large fluctuation for many of the diseases could be the following: a breeding effect, an effect of preventive work, and an effect of changing the therapeutic attitude. Many of the actions taken to bring about improvements would not have been possible without a functioning and practical recording system. Our experience is that an organ-related diagnosis system with up to 60 or 70 different diagnoses will meet the needs of the dairy industry.

Growth rate, health and welfare in a dairy herd with natural suckling until 6–8 weeks of age: a case report

Over a period of two years, growth rate and health were measured for dairy calves allowed to suckle their mothers up to 6–8 weeks of age. Thirty-one calves were weighted weekly, and the mean daily growth rate was 1.2 ± 0.03 kg from birth up to 13 weeks of age. Illness in calves and young stock was not observed. In the cows, the mean incidences of ketosis, displaced abomasum, puerperal paresis, mastitis, teat injury and retained placenta were 0, 0, 8, 22, 1 and 1%, respectively, during a 6-year period. The mean daily gain of 56 growing bulls was 1.4 kg when slaughtered at 15 months of age, which is higher than the mean daily gain of 0.95 kg in the population. Probiotics, hormones and vaccines were not used, and antibiotics were only used for treating illness. The present study indicates many advantages and few problems when dairy calves are penned together with the cows and allowed natural feeding up to 6–8 weeks of age. This production system was easy to manage, preferred by the farmer, and may satisfy the public concern regarding the practice of immediate separation of cow and calf in commercial milk production.

Risk factors associated with the incidence of veterinary-treated clinical mastitis in Swedish dairy herds with a high milk yield and a low prevalence of subclinical mastitis

We conducted a case–control study to investigate factors associated with the incidence rate of veterinary-treated clinical cases of mastitis (IRVTCM) in Swedish dairy herds with the overall objective to reduce the incidence of clinical mastitis (CM) and excessive use of antibiotics. Herds with documented high milk yield, low prevalence of subclinical mastitis and high (27.3–67.5 cases/100-cow years = case) or low (0.0–10.8 cases/100-cow years = control) IRVTCM were selected for this study. One hundred and fifty-eight herds participated. Logistic–regression models were used to assess statistically significant risk factors associated with a high or low IRVTCM. HI-herd farmers more often contacted a veterinarian for treatment of a cow with CM as soon as the milk appearance was altered, compared to LO-herd farmers that more often waited until the general condition of a cow was altered. HI-herd farmers also treated more cows due to high somatic-cell counts during lactation and/or at drying off. There were more high-yielding cows with dirty lower hind-legs, a higher percentage of first-parity cows and a higher incidence of veterinary-treated teat injuries in HI-herds. HI-herd farmers had their cows claw-trimmed more than once per year, compared to LO-herd farmers that had their cows claw-trimmed only once per year, and the condition of silage storage at HI-farms more often had one or more remarks. LO-herds consisted more often of cows of the Swedish Red and White breed, and their roughage diet was more often complemented with only commercial concentrates compared to HI-herds that more often fed grain in combination with commercial concentrates. The herds participating in this study were all well managed herds, and the attitude towards treatment and production seemed to influence the IRVTCM more than environmental factors.

Mastitis and related management factors in certified organic dairy herds in Sweden

BackgroundMastitis is one of the major threats to animal health, in organic farming as well as conventional. Preliminary studies of organic dairy herds have indicated better udder health in such herds, as compared to conventional herds. The aim of this paper was to further study mastitis and management related factors in certified organic dairy herds.MethodsAn observational study of 26 certified organic dairy herds in mid-eastern Sweden was conducted during one year. A large-animal practitioner visited the herds three times and clinically examined and sampled cows, and collected information about general health and management routines. Data on milk production and disorders treated by a veterinarian in the 26 herds, as well as in 1102 conventional herds, were retrieved from official records. Multivariable logistic regression was used to assess associations between herd type (organic vs. conventional) and incidence of disorders.ResultsThe organic herds that took part in the study ranged in size from 12 to 64 cows, in milk production from 3772 to 10334 kg per cow and year, and in bulk milk somatic cell counts from 83000 to 280000 cells/ml. The organic herds were found to have a lower incidence of clinical mastitis, teat injuries, and a lower proportion of cows with a high somatic cell count (as indicated by the UDS, Udder Disease Score) compared to conventional herds. The spectrum of udder pathogenic bacteria was similar to that found in other Swedish studies. Treatment of mastitis was found to be similar to what is practised in conventional herds. Homeopathic remedies were not widely used in the treatment of clinical mastitis.The calves in most of these organic herds suckled their dams for only a few days, which were not considered to substantially affect the udder health. The main management factor that was different from conventional herds was the feeding strategy, where organic herds used a larger share of forage.ConclusionUdder health in Swedish organic herds appears to be better than in conventional herds of comparable size and production. The major difference in management between the two types of farms is the proportion of concentrates fed. The mechanisms explaining the association between intensity of feeding and udder health in dairy cows require further research.

Bovine Claw and Limb Disorders Related to Reproductive Performance and Production Diseases

As part of a cross-sectional study of Norwegian Red Cattle, associations of lameness, lesions at the tarsus, claw shapes, and claw lesions with reproductive performance and production diseases were examined. Fifty-five tiestall herds and 57 freestall herds were sampled by computerized systematic selection and 2,665 cows were trimmed and limb and claw disorders recorded by 13 specifically trained claw trimmers during the late winter and spring of 2002. After exclusions, 2,583 cows were included in this study. Most claw lesions were mild (score 1). Prevalence of moderate and severe lesions (score 2 + 3) did not exceed 5% for any of the lesions. Hazard ratios for independent variables were identified using Cox regression analyses incorporating herd as a random effect in a positive stable frailty model. Wounds and swellings at the tarsus were associated with more clinical mastitis [hazard ratio (HR) = 4.0] and teat injuries (HR = 2.5). Moderate and severe heel-horn erosions in first-lactation cows were associated with increased calving interval (HR = 0.60). Moderate and severe hemorrhages of the sole in first-lactation cows were associated with decreased interval from calving to first service (HR = 1.6) and moderate and severe hemorrhages of the sole were associated with more milk fever (HR = 8.6). All hemorrhages of the sole (scores = 1, 2, and 3) were associated with more reproductive hormonal treatments (HR = 2.3). All sole ulcers in first-lactation cows were associated with longer interval from calving to last service (HR = 0.59) and longer calving interval (HR = 0.61), whereas sole ulcers in older cows were associated with longer calving interval (HR = 0.62). All sole ulcers also were associated with more milk fever (HR = 4.8) in all cows. Moderate and severe sole ulcers in older cows were associated with increased interval from calving to first (HR = 0.35) and last (HR = 0.37) service. Moderate and severe white-line fissures in older cows were associated with increased return rate from previous insemination (HR = 2.4). Our study shows that claw disorders are associated with poorer reproductive performance and some production diseases.

Milk flow and udder health in cows after treatment of covered teat injuries via theloresectoscopy: 52 cases (2000–2002)

To determine milk flow, somatic cell counts (SCCs), and the incidence of clinical mastitis in cows that had undergone theloresectoscopy for treatment of teat stenosis caused by mucosal detachment in the region of the streak canal or Fürstenberg's rosette. Retrospective study. 52 cows with teat stenosis that were treated via theloresectoscopy. Medical records of eligible cows were reviewed. Additional data regarding milking ease, SCC, development of clinical mastitis of the affected gland, and whether the cow remained in the herd were collected via owner-completed questionnaires. 49 of 52 questionnaires were completed. At referral, teat sinusitis was diagnosed in 29 of 52 cows. Milk flow was normal in 38 of 41 treated teats at discharge and in 24 of 40 during the next lactation. Thirteen of 49 cows were culled during the next lactation because of abnormal udder health. High SCC and teat sinusitis at referral and development of clinical mastitis during the 10-day period after surgery resulted in high SCCs in the remainder of the current lactation. The incidence of clinical mastitis during the remainder of the current and during the next lactation was higher in cows that had teat sinusitis at the time of surgery, compared with those that did not. Teat stenoses resulting from mucosal lesions in the region of the streak canal or Fürstenberg's rosette may be successfully treated via theloresectoscopy. Inflammation of the teat sinus and gland at the time of surgery may adversely affect udder health.

Procedures and surgeries of the teat

Injuries to the end of the teat are frequent and frustrating to treat. Treatment of these injuries evolved from being aggressive using teat knives to a more conservative approach employing rest nonreactive teat inserts. The process of milking seems simple, but it involves fine-tuned mechanics. Teat fibrosis, even when small, has a disastrous effect on the production life of an animal. There is no place for error; any surgical intervention should be precise and aim for perfection. Medical imaging techniques and minimally invasive surgery help the surgeon to make the best decision. Finally, more investigation is needed to treat varicose veins to understand the origin and develop better treatment. Teat injuries have drawn more attention more recently. Surgical interventions are better planned, and blind treatment with unsuitable teat knives is avoided. Treatment of superficial of full-thickness teat lacerations does not require a high level of anatomic or surgical knowledge, although basic surgical principles should be applied. Hemostasis, delicate débridgement and tissue handling, and appropriate suture materials and patterns are key to success. Appropriate sedation, anesthesia, and analgesia are essential to achieve this goal and should never be neglected.

Teat endoscopy (theloscopy) for diagnosis and therapy of milk flow disorders in dairy cows

Teat endoscopy (theloscopy) is a useful technique for diagnosis and therapy of covered teat injuries. Minimal invasive theloscopic surgery may help to restore milk flow, milk yield, and SCC of the affected quarter. Infection with pathogens may not change significantly, however. Cows treated as described may yield as much milk as their herdmates at a slightly increased udder SCC and stay as long in the herd as their herdmates. Theloscopy also may be used for diagnosis and therapy of various other teat disorders.

Health and welfare of dairy cows in different husbandry systems in Switzerland

Our objective was to compare health and welfare of dairy cows kept in three types of husbandry systems: (1) tie stalls with regular exercise in summer but minimal outdoor access during winter (the reference level for analyses); (2) tie stalls with regular exercise in an exercise yard or pasture throughout the year; (3) loose-housing with regular access to an outdoor exercise yard or pasture. A total of 134 farms were visited (two to) three times in two years. Cows were examined for lameness, skin alterations at the hock joints, scars or injuries at the teats, and skin injuries at other locations. Lying and standing-up behavior were also evaluated. Farmers were requested to record the incidence of medical treatments for the whole observation period. A multivariable logistic-regression analysis was performed for each indicator of health and welfare with husbandry type, aspects of the housing system, farm characteristics, and management routines as the predictor variables. For welfare indicators recorded on individual animals, regression was performed correcting for clustering of observations within herds by Generalized Estimation Equation. Risk factors for the incidence of medical treatments were analyzed in a negative-binomial regression model. The odds for lameness were reduced for tie stalls with regular exercise throughout the year (OR = 0.7). The prevalence of alterations at the hock joints was lower in loose-housing with regular outdoor exercise (OR = 0.4). Teat injuries were less frequent in loose-housing with regular outdoor exercise (OR = 0.1) and tie stalls with regular exercise (OR = 0.4). Farms with loose-housing and regular outdoor exercise had a lower incidence of medical treatments (IR = 0.6) than reference level farms.

乳頭損傷と乳房炎を合併した乳牛に乳頭管栓塞と搾乳休止による治療が奏効した1例

A six-year-old Holstein cow with anorexia and fever was diagnosed with teat-canal injury complicated by acute mastitis caused by Streptococcus uberis. The cow was treated by parenteral and intramammary administration of antibiotics and a wax-teat bougie (NIT) inserted into the teat canal of the affected quarter to halt milking. To rest the teat, the quarter was not milked for 25 days. Intramammary antibiotics infusions and bougie inser-tion were performed at five-day intervals. On day 26, a negative CMT and culture showed that the teat injury and the mastitis had been fully cured. On day 31, milk yield had recovered to pretreatment level.

Effects of health disorders on feed intake and milk production in dairy cows

The purpose of this study was to quantify feed intake decreases and associated milk production losses related to health disorders in dairy cows. Daily individual records of feed intake, milk production and health disorders were available in an experimental farm (107 328 daily records on 1050 lactations from 551 Holstein cows less than 140 DIM). Milk production losses and feed intake decreases were estimated for each health disorder, from 5 days before to a maximum of 140 days after its diagnosis, in comparison to a cow without the disorder, using two separate mixed linear models. On the day of diagnosis, diarrhoea, systemic mastitis, ketosis and milk fever were associated with high reduction in milk production (4.1–25.7 kg) and feed intake (6.7–14.7 kg DM). High cumulated decreases occurred in milk production (109–160 kg) after systemic mastitis, teat injuries and twin calving and in feed intake (46–72 kg DM) after ketosis, systemic mastitis and hock lesions. The average estimated effect of health disorders is a 1.94-kg milk yield loss per kg DM feed intake decrease. This suggests that economical evaluation of health control actions should include associated feed intake decreases.

Lameness and Udder Health in Swedish Dairy Herds, as Influenced by Housing Changes

Traditionally, tie-stalls have been the predominant housing system for dairy cattle in northern Europe. In Sweden, tie-stalls are either long-stalls (approx. 2.20 m) or short-stalls (approx. 1.70 m). In long-stalls the cows are normally closed out from the feeding table when the herdsman is not in the barn, while in short-stalls they have always access to the feeding table. Loose housing has been recommended and increases with new facilities. Presently, one fourth of the Swedish dairy cows are loose-housed. Very few observational studies of possible animal health effects of a transition from one housing system to another have been performed. The aim of the present study was to assess effects of changes in housing system on the occurrence of veterinary-treated foot and leg disorders, clinical mastitis, teat injuries and of high milk somatic cell counts (MSCCs). The objective was to improve the basis for farmers' decisions in connection with structural changes in milk production. Monthly herd disease incidence rates or prevalences in 194 Swedish commercial dairy herds from 1988 to 1995 were collected retrospectively from the official milk recording scheme and merged with county administrative and farmers' data on housing and management. The studied herds constituted approximately one third of all dairy facilities approved for rebuilding in the selected counties during the same time period. The most common changes of housing systems were going from long-stalls to short-stalls (61 herds), remaining in short-stalls (41 herds) and going from short-stalls to cubicles (33 herds). Predominant breeds were the Swedish Red and White (SRB) and the Swedish Holstein breed (SLB). Mean herd size was 34.6 cows for long-stalls, 39.2 for short-stalls, 62.7 for cubicles and 55.8 for straw yards. The records were either from 1 to 45 months before building start (mean 10.7 months) or from 0 to 59 months after building finish (mean 11.4 months). All data from the actual building period were discarded. Four Poisson regression models were applied to the data (5982 to 7026 herd-month records), using the GEE method and the GENMOD procedure in SAS. Monthly observations were treated as repeated measures within herds (autoregressive correlation structure). There were significant transitory increases in the incidence of clinical foot/leg disorders when changing from tie-stalls to cubicles (RR=3.2-4.7) and decreases in the incidences of clinical mastitis (RR=0.20-0.77) and teat injuries (RR=0.13-0.60) when changing from tie-stalls to loose housing. Effects on foot/leg health generally lasted for less than 18 months after building finish, while udder health improvements persisted beyond 18 months. Reductions in the incidence of clinical mastitis were not accompanied by any clear changes in the prevalence of high MSCCs. Later than 18 months after rebuilding, herds that shifted from long-stalls to short-stalls had less foot and leg lesions than those remaining in long-stalls. It is concluded that a change in dairy cow housing from tie-stalls to loose housing deteriorates foot/leg health temporarily and improves udder health. 236 Abstracts – Oral presentations at 11th ICPD

Foot/leg and udder health in relation to housing changes in Swedish dairy herds

Monthly herd disease incidence rate or prevalence estimates in 196 Swedish commercial dairy herds from 1988 to 1995 were collected retrospectively from the official milk-recording scheme and merged with county administrative and farmers’ data on housing and management. To study the effects of changes in housing system on the occurrence of veterinary-treated foot/leg disorders, clinical mastitis, teat injuries and high milk somatic cell counts (MSCCs), four marginal Poisson or negative-binomial regression models were applied to the data (6011–7063 herd–month records), using the generalized estimating-equations method. Monthly observations were treated as repeated measures within herds. There were significant transitory increases in the incidence of clinical foot/leg disorders when changing from tie-stalls to cubicles and decreases in the incidences of clinical mastitis and teat injuries when changing from tie-stalls to cubicle or straw-yard systems. Effects on foot/leg health generally lasted for <18 months after building finish, while udder-health improvements persisted >18 months. Reductions in the incidence of clinical mastitis were not accompanied by any clear changes in the prevalence of high MSCCs.

北海道根室管内の217乳牛群における死廃・病傷事故と乳量水準および飼養形態との関連

Effects of milk yield and feeding system on death and disease incidence and average calving numbers were examined in 217 dairy herds in the Nemuro district of Hokkaido. High-yielding herds tended to demonstrate a lower calving rate, higher culling rates, lower milk somatic-cell counts, and fewer non-pregnant days. There was little difference in death and disease incidence related to milk yield and feeding systems. Disease rateswere higher in high-yielding herds. Disease rates were higher among cattle kept tied in barn stalls than in those free in their stalls. Incidences of mastitis, displaced abomasum, gastroenteric disorder, and ketosis were higher in high-yielding herds. Incidences of mastitis, teat injury, and ovarian disorder were higher in herds tied in barn stalls, whereas occurrences of displaced abomasum and milk fever were more numerous in herds housed free in barn stalls. These results indicate a close association between disease prevalence and feedingsystem management.

Effect of health disorders on culling in dairy cows: a review and a critical discussion

Risk of culling consequent to the main health disorders occurring in the current production systems is reviewed. Survival analysis including health disorders as time-dependent variables is considered to be the most appropriate method to assess their effects because they allow a better description of the exact follow-up of disease history. Farmers preferentially consider health events in the current lactation and/or those occurring in early stages of lactation for making culling decisions. The unfavourable direct effects on culling of dystocia and udder disorders (mastitis and teat injuries) are clearly demonstrated, whereas there are variations between studies on the association between metabolic and reproductive disorders and culling. These variations may be due to differences in study designs, populations involved and methods. Consequences, in terms of estimated effect of health disorders, of methodological choices (e.g. whether or not including in the models descrip- tors for milk yield and/or reproductive performance) are discussed. Metabolic and reproductive dis- orders may act indirectly through a subsequent decrease in milk yield and reproductive performance. The impact of health disorders on longevity is on average weak, compared to the impact of low milk yield potential and poor reproductive performance. Herd characteristics (availability of heifers, quota, farmer's attitude towards risk and uncertainty...) modify the risk for a cow to be culled for a given health disorder. Aims of further studies could be (1) to interpret the meaning and to analyse the reliability of culling reasons information, (2) to evaluate the relative effect on culling of health dis- orders and performance (milk yield and reproduction) in different parities, (3) to investigate the role of components of the herd effect on the risk of culling. dairy cow / culling / health disorders / risk factors / survival analysis

Milk Yield, Somatic Cell Counts and Risk of Removal from the Herd for Dairy Cows after Covered Teat Canal Injury

The objective of the study reported here was to evaluate milk yield, somatic cell count (SCC), and risk of removal of cows from the herd after covered teat injury. In covered teat injuries the teat skin is relatively undamaged. Eighty-one patients were used for this study. Teat injuries were diagnosed and treated using endoscopy (Medl et al. 1994). After treatment teats were rested for 3 x 3 days (Geishauser et al. 1998). Each patient was matched to three herdmates by breed, age and calving date. Data on milk yield and SCC were available from DHI records.

Culling of dairy cows. Part III. Effects of diseases, pregnancy status and milk yield on culling in Finnish Ayrshire cows

The effects of 15 diseases, pregnancy status and milk yield on culling were studied in 39 727 Finnish Ayrshire cows that calved in 1993 and were followed until culling or next calving. Survival analysis, using the Cox proportional hazards model, was performed with diseases, pregnancy status and milk yield as time-dependent covariates. Effects of parity, calving season and herd were also accounted for. Pregnancy status was the single most influential factor affecting culling decisions, followed by milk yield. Several diseases also had a significant effect on culling, the most influential ones being mastitis, lameness, teat injuries, and milk fever. The effects of all of these factors varied according to the stage of lactation. Milk yield had a significant effect on culling decisions, depending on the stage of lactation. At the beginning of lactation, milk production did not have any effect on culling decisions, but later on, the highest producers were at the lowest risk of being culled and the lowest producers had the highest risk. Adjusting for milk yield modified the effects of parity, most diseases and also pregnancy status on culling. Effects of parity increased after including milk yield in the model, indicating that milk yield and parity are interrelated in their effects on culling. The effects of pregnancy status also increased towards the end of lactation when milk yield was accounted for in the model. The effects of mastitis, teat injuries and lameness decreased after adjusting for milk production. These diseases lower milk yield and thus, part of their effect on culling was mediated through milk production. The effects of anestrus and ovarian cysts were mainly modified by pregnancy status, but not by milk yield. The effects of milk fever on culling increased at the beginning of lactation after including milk yield in the model. This suggests that even though cows with milk fever tend to be higher producers, it is the disease as such that triggers the culling decision early in the lactation. The changes in the effects of other diseases after adjusting for milk yield varied, depending on the disease and the stage of lactation.