scholarly journals Dairy Cow Culling - Reasons And Risk Factors

2020 ◽  
Author(s):  
Triin Rilanto ◽  
Kaari Reimus ◽  
Toomas Orro ◽  
Ulf Emanuelson ◽  
Arvo Viltrop ◽  
...  
Keyword(s):  
Risk Factors ◽  
Dairy Cows ◽  
Milk Yield ◽  
Metabolic Diseases ◽  
Good Health ◽  
Breeding Value ◽  
Proportional Hazard ◽  
Protein Ratio ◽  
Holstein Breed ◽  
Weibull Proportional Hazard

Abstract Background Culling is a major cost for dairy farms but also an essential part in managing herd productivity. The study aimed to identify the culling rates of Estonian dairy cows, identify the farmers´ stated reasons and risk factors for culling. This observational study used registry data of all cows from herds with ≥20 cow-years in 2013-2015. Cow lactation-level analyses included data of 86,373 primiparous cows from 409 herds and 177,561 lactations of 109,295 multiparous cows from 410 herds. Weibull proportional hazard regression models were used to identify risk factors for culling due to slaughter or death.Results The overall culling rate of Estonian dairy cows was 26.24 (95% CI 26.02; 26.46) per 100 cow-years. The most common farmers´ stated reasons for culling were feet/claw disorders (26.4%), udder disorders (22.6%), metabolic and digestive disorders (18.1%) and fertility problems (12.5%). Animal-level risk factors for culling were Holstein breed, older parity, lower milk yield breeding value, older age at first calving, longer previous calving interval, having assisted calving, stillbirth and birth of twins/triplets. Lower milk yield, somatic cell count over 200,000 cells/ml and fat/protein ratio over 1.5 at first test-milking after calving were associated with greater culling hazard during the lactation. Cows from larger herds, herds with decreasing size and higher milk yields had higher culling probability.Conclusions This study emphasises the need for improved management of hoof health and prevention of mastitis and metabolic diseases. It is essential to ensure easy calving and good health of cows around calving in order to lower the culling hazard.

scholarly journals Dairy Cow Culling - Reasons And Risk Factors

2020 ◽  
Author(s):  
Triin Rilanto ◽  
Kaari Reimus ◽  
Toomas Orro ◽  
Ulf Emanuelson ◽  
Arvo Viltrop ◽  
...  
Keyword(s):  
Risk Factors ◽  
Dairy Cows ◽  
Milk Yield ◽  
Metabolic Diseases ◽  
Good Health ◽  
Breeding Value ◽  
Proportional Hazard ◽  
Protein Ratio ◽  
Holstein Breed ◽  
Weibull Proportional Hazard

Abstract Background Culling is a major cost for dairy farms but also an essential part in managing herd productivity. The study aimed to identify the culling rates of Estonian dairy cows, identify the farmers´ stated reasons and risk factors for culling. This observational study used registry data of all cows from herds with ≥20 cow-years in 2013-2015. Cow lactation-level analyses included data of 86,373 primiparous cows and 177,561 lactations of 109,295 multiparous cows. Weibull proportional hazard regression models were used to identify risk factors for culling due to slaughter or death. Results The overall culling rate of Estonian dairy cows was 26.24 (95% CI 26.02; 26.46) per 100 cow-years. The most common farmers´ stated reasons for culling were feet/claw disorders (26.4%), udder disorders (22.6%), metabolic and digestive disorders (18.1%) and fertility problems (12.5%). Animal-level risk factors for culling were Holstein breed, older parity, lower milk yield breeding value, older age at first calving, longer previous calving interval, having assisted calving, stillbirth and birth of twins/triplets. Lower milk yield, somatic cell count over 200,000 cells/ml and fat/protein ratio over 1.5 at first test-milking after calving were associated with greater culling hazard during the lactation. Cows from larger herds, herds with decreasing size and higher milk yields had higher culling probability. Conclusions This study emphasises the need for improved management of hoof health and prevention of mastitis and metabolic diseases. It is essential to ensure easy calving and good health of cows around calving in order to lower the culling hazard.

scholarly journals Dairy Cow Culling - Reasons and Risk Factors

2020 ◽  
Author(s):  
Triin Rilanto ◽  
Kaari Reimus ◽  
Toomas Orro ◽  
Ulf Emanuelson ◽  
Arvo Viltrop ◽  
...  
Keyword(s):  
Risk Factors ◽  
Dairy Cows ◽  
Milk Yield ◽  
Metabolic Diseases ◽  
Good Health ◽  
Breeding Value ◽  
Proportional Hazard ◽  
Protein Ratio ◽  
Holstein Breed ◽  
Weibull Proportional Hazard

Abstract Background Culling is a major cost for dairy farms but also an essential part in managing herd productivity. This study aimed to identify the culling rates of Estonian dairy cows, identify the farmers’ stated reasons and risk factors for culling. This observational study used registry data of all cows from herds with ≥20 cow-years in 2013-2015. Cow lactation-level analyses included data of 86,373 primiparous cows from 409 herds and 177,561 lactations of 109,295 multiparous cows from 410 herds. Weibull proportional hazard regression models were used to identify risk factors for culling due to slaughter or death. Results The overall culling rate of Estonian dairy cows was 26.24 (95% CI 26.02; 26.46) per 100 cow-years. The most common reasons farmers stated for culling were feet/claw disorders (26.4%), udder disorders (22.6%), metabolic and digestive disorders (18.1%) and fertility problems (12.5%). Animal-level risk factors for culling were Holstein breed, older parity, lower milk yield breeding value, older age at first calving, longer previous calving interval, having assisted calving, stillbirth and birth of twins/triplets. Lower milk yield, somatic cell count over 200,000 cells/ml and fat/protein ratio over 1.5 at first test-milking after calving were associated with greater culling hazard during the lactation. Cows from larger herds, herds with decreasing size and higher milk yields had a higher culling probability. Conclusions This study emphasises the need for improved management of hoof health and prevention of mastitis and metabolic diseases. It is essential to ensure easy calving and good health of cows around calving in order to lower the culling hazard.

scholarly journals DEPENDENCE OF DAIRY PRODUCTIVITY COWS OF UKRAINIAN RED-AND-WHITE DAIRY BREED ON GENOTYPIC AND PARATYPIC FACTORS

2021 ◽  
pp. 23-28
Author(s):  
Leontiі Khmelnychyi ◽  
Valeriia Pryimachok ◽  
Maksym Prokopovych ◽  
Serhii Kholod ◽  
Serhii Hryshyn
Keyword(s):  
Dairy Cows ◽  
Milk Yield ◽  
Selection Process ◽  
Breeding Value ◽  
Milk Productivity ◽  
Maternal Line ◽  
Holstein Breed ◽  
Reliable Effect ◽  
Calving Season ◽  
Dairy Breed

Researches to study the milk productivity dependence of Ukrainian Red-and-White dairy cows on genotypic and paratypic factors were conducted in the breeding farm PAE "Piskivske" Bakhmach district of Chernihiv region. The most representative five genotypic groups of animals divided by the conditional share of heredity of Holstein breed were studied: I - livestock with a share of blood 50.01-56.25; II - 56.26-62.50; III - 62.51-75.00 and IV - 75.01-87.50; V - 87.51% and <. By comparing different genotype groups of cows installed dependence of yield amount on conditional share of inheritance Holstein breed. With the growth conditional proportion of Holstein blood, milk yield increased during the evaluated first three and higher lactations. The high and reliable effect was found on the yield amount of cows firstborn by factors of birth (  = 0.329) and calving (   = 0.336). The share of birth and calving season influence on milk yield although insignificant but reliable and amounted to 3.7 and 5.3%, respectively. The value of milk yield of cows firstborn in the controlled herd greatly depended on the sire genotype (  = 0.315), cow's conditional blood by Holstein breed (  = 0.264), father breeding value (   = 0.335) and mother cow's father (  = 0.340), paternal (   = 0.163) and maternal line (   = 0.089). According to research results was substantiated expediency of monitoring selection information, identification and use of animal-specific patterns of leading traits development of milk productivity depending on the geno-  and paratypic factors influence in the selection process of pedigree herd formation.

scholarly journals THE ESTIMATION OF THE ECONOMIC USE AND LIFETIME PRODUCTIVITY OF COWS OF UKRAINIAN BLACK-AND-WHITE DAIRY BREED DEPENDING ON THE REASONS OF THEIR DISPOSAL

2018 ◽  
Vol 56 ◽  
pp. 84-93 ◽  
Author(s):  
A. L. Shulyar
Keyword(s):  
Dairy Cows ◽  
Total Duration ◽  
Correlation Coefficients ◽  
Breeding Value ◽  
Lactation Period ◽  
Black And White ◽  
Holstein Breed ◽  
Reproductive Capability ◽  
Economic Use ◽  
Dairy Breed

An important selection peculiarity of dairy cows is their productive longevity. Besides, the indicators of cow productivity along with genetic potential are the most important criteria of the economic efficiency of their use. Low or not sufficient level of lifetime productivity indicators and of the period of the economic use of cows determine the necessity of monitoring of the selection information according to these indicators in the breed herds as well as the of using corresponding selection methods for their improvement. The goal of our research was the estimation of an economic use of lifetime cow productivity of Ukrainian Black-and-White dairy breed depending on the reasons of their disposal from the herd and genotype. The research was conducted at a private agrarian firm (PAF) «Yerchyky» Zhytomyr oblast according to the data of breeding and productive use of 497 cows which were disposed from the herd on different reasons. The reasons for the cow disposal were determined according to the veterinary disposal acts. The indicators of cow economic use and lifetime productivity were determined on the ground of the term of rearing, life duration, term of economic use, amount of lactations, the total duration of lactation period, milk yields, milk yield per one lactation day, per life, and per economic use. Statistical processing was performed by means of Microsoft Excel software kit using the methods of variation statistics. As follows from the results of the research, in the process of holsteinization the dynamics of the parameters of the economic use of cows is characterized by curvilineal type: as follows from the heterotic effect they increased in animals with an conditional share of genetic heredity of Holstein breed from 50 and 62.5 to 75%, and then when the genetic heredity share of the improved breed increased by more than 75% they got worse due to the contradiction “genotype-environment”. At the same time within the determined genotypes (1st group-up to 50%, 5th group-87.6–100%) the indicators of lifetime productivity increase in case of 66% of reliable results. Besides, the interconnection level of the indices of lifetime use of the dairy cows of different genotypes has been studied. The criteria of the significance of the correlation coefficients according to Student has been used. The closer the linkage, the higher the correlation coefficients and the higher the criteria of their reliability. Generalized criteria of reliability on the grounds of all indicators of lifetime use was the lowest in cows of the 1st and 2nd groups, and the highest in cows of the 3rd group with further decrease in high half-bred cows and pure-breed cows of the 4th and 5th groups. It testifies to the fact that there is a close interconnection between given parameters and real milk yields in 3rd group cows (62.6–75.0% of the improved Holstein breed). At present, the reason of the shortening of the period of economic use is an early disposal of cows from the herd. A greater part of milking cows is disposed in the most productive period or even before it. At the given enterprise, a vast majority of holsteinized cows (77.5%) was disposed from the herd on four main reasons: unsatisfactory reproductive capability (32.2%), limbs diseases (22.3%), postpartal complications (13.9%) and low productivity (9.1%). The other reasons for cow disposal were within 1.6–7.0% (totaled up 22.5%) as to the total number of cow population that were disposed of the herd. It should be mentioned that the disposal caused by low productivity was only in the first calvers of the 1st and 2nd groups, in which the conditional share of genetic heredity of a Holstein breed did not exceed 62.5%. The parameters of the economic use and of lifetime productivity of Ukrainian Black-and-White dairy cows of different genotypes which were disposed of the herd because of their unsatisfactory reproductive capability, limbs diseases, postpartal complications and low milking productivity have been also analyzed. It has been determined that the indicated reasons for the disposal had different effects on the parameters of an economic use and on cow productivity. Because of any of four indicated reasons for cow disposal of the herd under condition of in-barn keeping and optimal feeding the preference on lifetime productivity belongs to the cows of the 4th and 5th groups (with a conditional share of Holstein heredity of more than 75%) with simultaneous worsening of the indicators of economic use. As a third part of cows at this enterprise was disposed of the herd ahead of time on the reason of unsatisfactory reproductive capability, that results in breeding value and in the results of the economic use of cows, the updating of the technology of artificial animal insemination and renewal will promote to solving the problem.

scholarly journals FEATURES OF BREEDING VALUE INHERITANCE SIRES OF HOLSTEIN BREED

2021 ◽  
Vol 61 ◽  
pp. 64-72
Author(s):  
А. P. Кrugliak ◽  
Т. О. Кrugliak
Keyword(s):  
Milk Yield ◽  
Population Level ◽  
Point Of View ◽  
Breeding Value ◽  
Phenotypic Correlation ◽  
Intermediate Form ◽  
Theoretical Point ◽  
Genetic Progress ◽  
Holstein Breed ◽  
Additive Form

In our studies, the phenotypic manifestation of the additive form of inheritance of breeding value by milk yield (intermediate and parental dominance) was in 334 (82.2%) bulls, and non-additive form (over-dominance and regression) – in 72 (17.8%) including: over-dominance in 55 (13.5%) and regression in 17 heads (4.2%). In the population assessment, for all forms of inheritance, there was a clear quantitative shift of the breeding value of sons of milk yield to positive (+) values, compared with the breeding value of their parents. This confirms that sons, selected after their evaluation, and recognized as milk yield improvers. The variability of the breeding value of sons by milking depending on the forms of its inheritance has been established. According to the group of bulls by intermediate type of inheritance, milk yield sign were found in 291 (71.7%) sons, whose pedigree value was 606.4 ± 11.6 kg and was higher than the half-sum of both parents (554 kg), which deviates from the action of intermediate inheritance at 52 kg (109%). After all, the recognition of the intermediate nature of inheritance involves obtaining in the offspring of animals with the same set of chromosomes as their parents, and hence with the same phenotype. Therefore, from a theoretical point of view, genetic progress in the population should be not expected from this group of animals. However, in this case, the increase in breeding value was 9%, which is statistically significant (P > 0.99). A rather high variability of the breeding value of sons from its level in their parents with an intermediate form of inheritance has been established. Thus, of the 159 bulls-breeders in which the breeding value was inherited by intermediate form, only 30 sons (7.3% of the total population) of the bull Duster 2147488 (BV +579 kg and mothers with an average BV +632 kg, half the amount of the BV of both parents was +605 kg), was +605.5 ± 30.8 kg and was equal to the half-sum of the BV of both parents, and 9 (2.2%) sons of the bull Manfred 2183007, whose breeding value was, on average, at the population level +856.3 ± 37.6 kg and was equal to the half-sum of the indicator of the parents' BV (+851 kg). The inheritance of breeding value of bulls on quantitative signs of milk productivity in highly consolidated breeds on these signs, at intra-breeding selection occurs by a combination of phenotypic display of action of additive and non-additive (super-dominance) forms of inheritance. The frequency of these forms of inheritance probably is determined by the number and quality of chromosome pairs in the karyotype of animals on the probable basis of their manifestation in the population [15]. The relative variability of breeding value by milk yield along the line "father – son" and "mother – son" depends on the form of its inheritance. The coefficient of phenotypic correlation between the breeding value of parents and sons in the intermediate form of inheritance is +0.524 – +0.560 and increases with parental dominance to +0.907 ± 0.040 and +0.985 ± 0.006, and over-dominance to +0.887 ± 0.044 and +0.905 ± 0.033, at high statistical significant. Inheritance by non-additive form (over-dominance of both parents) is more effectively associated with increasing of breeding value by milk yield their sons than by the additive form.

scholarly journals Fleckscore system of exterior evaluation as a more accurate indirect predictor of longevity in Slovak Simmental dairy cows

2021 ◽  
Author(s):  
Eva Strapáková ◽  
Peter Strapák ◽  
Juraj Candrák ◽  
Ivan Pavlík ◽  
Katarína Dočkalová
Keyword(s):  
Dairy Cows ◽  
Reference Group ◽  
Proportional Hazard ◽  
Proportional Hazard Model ◽  
Productive Life ◽  
Body Conformation ◽  
Individual Traits ◽  
Weibull Proportional Hazard ◽  
Relationship Of ◽  
The Relationship

The goal of the work was to discover the influence of conformation traits evaluated by the Fleckscore system on the length of productive life of Slovak Simmental dairy cows. Evaluation of body conformation traits according to the Fleckscore system was performed on 3 452 cows. The relationship of individual traits to longevity was analysed using the Weibull proportional hazard model. The results confirmed that smaller and longer cows, which were well muscular and with a deeper body, had a lower risk of early culling than cows in the reference group. Hock angularity, pastern and hoof height scored with low or high marks were associated with an early culling of cows. In terms of the length of productive life, a slightly more elastic pattern is required. Cows with a deeper udder and a stronger and tighter fore udder attachment, which were also average in notching and height central ligament and centrally placed teats, reached a longer productive life.  

scholarly journals PREVALENCE AND RISK FACTORS OF SUBCLINICAL MILK FEVER AND KETOSIS IN LACTATING CROSS-BRED DAIRY COWS WITH THEIR THERAPEUTIC MANAGEMENT IN BANGLADESH

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
L. Naher ◽  
M. A. Samad ◽  
S. H. M. F. Siddiki ◽  
M. T. Islam
Keyword(s):  
Risk Factors ◽  
Dairy Cows ◽  
Milk Yield ◽  
Serum Calcium ◽  
Ketone Bodies ◽  
Therapeutic Management ◽  
Lactation Period ◽  
Potential Health ◽  
Milk Fever ◽  
High Prevalence

Background: Bovine Milk fever (MF/hypocalcaemia) and ketosis (CK/hypoglycemia and hyperketonemia) both in clinical and sub-clinical forms are the most important metabolic diseases caused by metabolic disorders of calcium and carbohydrate respectively that affect mainly high milk yielding dairy cows worldwide. Sub-clinical form may be more costly due to comparatively high prevalence and consequence of high risk of decreased productive and reproductive performances with increased reproductive and other disorders. Objectives: The objectives of this study were to determine the prevalence of sub-clinical hypocalcaemia (SCHC) and sub-clinical ketosis (SCK) and to investigate important potential risk factors for SCHC and SCK with their therapeutic management in lactating cross-bred dairy cows. Materials and Methods: A cross sectional study was conducted on 220 dairy crossbred (HF  L = 190, SH  L = 20 and JS  L = 10) cows maintained in nine dairy farms and one smallholder farm during the period from July to November 2016. The parity (1 to 8), lactation stages (1 to 13 weeks), body condition score (BCS), breed (3 crossbreds), age (3.5 to 14 years) and milk yield (liter/day) were evaluated as possible risk factors. The serum calcium, inorganic phosphorus, magnesium and glucose concentrations of the 220 dairy cows were determined by using imported commercial kits. Dairy cows with serum calcium concentrations  8.0 mg/dl and serum glucose  44.0 mg / dl with positive ketone tests but not showing any clinical signs were considered SCHC and SCK respectively. Results: The overall prevalence of SCHC was 30.0%, of which 32.11% were recorded in HF  L, 15.0% in SH  L and 20.0% in JS  L cross-bred cows. The overall prevalence of SCK was 25.0%, of which 27.37% in HF  L, 10.0% in SH  L and 10.0% in JS  L cross-bred cows. The SCHC was recorded 10 times greater than MF and SCK 6 times greater than CK in Bangladesh. The hypocalcemia and hypophosphatemia with hypermagnesemia status were recorded in SCHC affected lactating cows which were more significantly (p < 0.05) higher (46.67%) at 4th parity and lower (16.67%) at 1st parity. The significantly (p < 0.01) higher prevalence of SCK was recorded at the 4th (53.33%) in comparison to other parity especially lowest at 1st (2.78%) and 2nd (4.0%) parity. The significantly (p < 0.1) highest prevalence of SCHC and SCK were recorded at high milk yield during the 1st (94.44%; 77.78%) and 2nd (66.67%; 56.67%) weeks of lactation period than the higher lactation stages respectively. The effects of BCS on the milk yield and the prevalence of SCHC and SCK are presented and discussed. Encouraging results with increased blood calcium and glucose levels were obtained on the therapeutic response of SCHC with oral calcium and SCK with oral propylene glycol. Conclusions: The SCHC and SCK have detrimental effects on cow health, productivity and reproduction and also predisposes to other diseases and disorders. The efficient balanced ration, periodic screening blood, milk and urine for determination of concerned biochemical constituents and ketone bodies considering risk factors could help to early detection of SCHC and SCK to limit their effects in dairy cattle. The high prevalence of SCHC and SCK recorded in this study should be viewed as a potential health risk to the transition cows that requires further research. Keywords: Sub-clinical milk fever, Sub-clinical ketosis, crossbred cows, prevalence, risk factors, calcium, magnesium, phosphorus, glucose, ketone bodies, therapeutic management, Bangladesh

scholarly journals Effects of flooring and rearing system on hoof health of dairy cows in some selected areas of Bangladesh

2014 ◽  
Vol 43 (2) ◽  
pp. 132-137 ◽  
Author(s):  
MA Rahman ◽  
MA Imtiaz ◽  
M Ahaduzzaman ◽  
KK Ghosh ◽  
AA Masud ◽  
...  
Keyword(s):  
Risk Factors ◽  
Dairy Cows ◽  
Milk Yield ◽  
Concrete Floor ◽  
Conventional Risk Factors

A survey was conducted to explore prevalence and risk factors of diverse hoof disorders on dairy cows at Chittagong and Patuakhali, Bangladesh from June 2012 to February 2013. About 2103 cows were examined from where 497 cases identified having fissure (37%), crack (19%), partially broken (19%), swollen hoof (16%) and multiple disorders (9%) in backyard dairy cows whereas 37%, 17%, 20%, 20% and 6% in commercial cows, respectively. Significantly higher prevalence (p<0.05) was recorded in cows reared under concrete floor (68.4%) compared to brick (13.27%) and concrete with rubber bedding (18.3%). Other major conventional risk factors were season, age, milk yield and washing practiced on floor though the results were not significant (p>0.05). The study has remarked frequency of hoof diseases in the survey areas along with factors causing risk to dairy cows.DOI: http://dx.doi.org/10.3329/bjas.v43i2.20714 Bang. J. Anim. Sci. 2014. 43 (2): 132-137

96 Association between metabolic diseases and fertility of high-yielding dairy cows in a transition management facility using survival analysis and machine-learning models

2019 ◽  
Vol 31 (1) ◽  
pp. 174
Author(s):  
O. B. Pascottini ◽  
M. Probo ◽  
S. LeBlanc ◽  
G. Opsomer ◽  
M. Hostens
Keyword(s):  
Dairy Cows ◽  
Metabolic Diseases ◽  
Clinical Mastitis ◽  
Proportional Hazard ◽  
Pregnancy Risk ◽  
Proportional Hazard Models ◽  
Milk Fever ◽  
Cox Proportional Hazard ◽  
Cox Proportional Hazard Models ◽  
Machine Learning Models

This study aimed to evaluate the association between individual and multiple metabolic diseases (MD and MD+) diagnosed during the transition period (±3 wk relative to calving) and the probability of pregnancy until 210 days in milk (DIM) in Holstein-Friesian dairy cows. Disease and reproductive data from a dairy herd with 1946 calvings (n=542 primiparous and n=1404 multiparous cows) were analysed using a 1-year cohort. The recorded MD were milk fever, ketosis, displaced abomasum, retained placenta, metritis, twinning, and clinical mastitis. The association between the 210-DIM pregnancy risk and the MD was evaluated as MD cows (uncomplicated cases) v. MD+ cows (complicated cases) v. healthy cows (3 groups of cows). Univariable survival models were used to analyse the association of MD and MD+ with pregnancy until 210 DIM, accounting for parity. Univariable Cox proportional hazard models were used to quantify the relative risk of pregnancy per day. A hierarchically ordered decision tree and a random forest model were built to explore the importance of MD and parity on the pregnancy risk within the first 210 DIM. Parity affected the 210-DIM pregnancy risk (P&lt;0.001); therefore, all further analyses were stratified by parity. The incidence of MD and MD+ for primiparous and multiparous cows were 29 (n=159) and 9% (n=48), and 23 (n=317) and 11% (n=160), respectively. The overall 210-DIM pregnancy risk was 77% (n=415) for primiparous cows and 62% (n=879) for multiparous cows. Among healthy cows (no MD) the 210-DIM pregnancy risk was 80% (n=269) for primiparous cows and 82% (n=537) for multiparous cows. Conversely, the 210-DIM pregnancy risk for cows with MD or MD+ were 73 (n=116) and 63% (n=30) for primiparous and 48 (n=152) and 46% (n=74) for multiparous cows, respectively. Using the healthy cows as the reference, the 210-DIM hazard ratios for conception were 0.8 for MD [95% confidence interval (CI)=0.6-1.0; P=0.05] and 0.5 for MD+ (95% CI=0.4-0.8; P=0.005) for primiparous cows and 0.5 for MD (95% CI=0.4-0.6; P&lt;0.001) and 0.4 for MD+ (95% CI=0.3-0.6; P&lt;0.001) for multiparous cows. Parity had profound effect on the 210-DIM pregnancy risk. The hazard ratio for conception was reduced when a MD was complicated with another MD (MD+) in both primiparous and multiparous cows. Both the decision tree and random forest analysis also indicated that parity was the most influential variable reducing fertility among cows, followed by (in order of magnitude of effect) milk fever, displaced abomasum, ketosis, and clinical mastitis. Including multiple disease interactions into multivariable Cox proportional hazard models are highly likely to violate the proportional hazards assumption due to complex disease interactions. Machine-learning models represent a valid alternative to accommodate large datasets in the presence of missing values and intricate dependencies among explanatory variables.

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