Effect of stillbirths on dam survival and reproduction performance in Holstein dairy cows

The objectives of this study were to evaluate the effect of stillbirth on survival and reproductive performance of lactating dairy cows. Data were collected from 2 different regions of the US calving-ease scores (CES) were recorded by farm personnel on a scale of 1 (no problem) to 5 (extreme difficulty). Stillbirths were recorded by farm personnel. The final analysis included 13,608 calvings of which 93.4% were live calves and 6.6% stillbirths. An increasing or decreasing trend in the incidence of stillbirth by parity and by CES was analyzed by Cochran-Armitage trend tests. A significant decreasing trend in the incidence of stillbirth by parity group was detected. The incidence of stillbirth increased as the CES increased. The incidence of stillbirths was 3.6, 11.2, 25.9, and 60.1% for CES score 1, 2, 3, and 4, respectively. Dam survival in the herd and reproductive performance were analyzed by the Cox proportional hazards model. Variables that decreased dam survival time were stillbirths, primiparity, and CES of 3 and 4. The variables that reduced reproductive performance were stillbirths, multiparity, male calves, and CES of 3 and 4. Cows that had stillbirths had significantly increased risk of culling/death throughout the lactation and increased median days open by 88 d compared with cows that had live calves. In conclusion, losses from stillbirths are far greater than just the value of the calf.     

Association between milk yield and serial locomotion score assessments in UK dairy cows

This study investigated the effect of lameness, measured by serial locomotion scoring over a 12-mo period, on the milk yield of UK dairy cows. The data set consisted of 11,735 records of test-day yield and locomotion scores collected monthly from 1,400 cows kept on 7 farms. The data were analyzed in a multilevel linear regression model to account for the correlation of repeated measures of milk yield within cow. Factors affecting milk yield included farm of origin, stage of lactation, parity, season, and whether cows were ever lame or ever severely lame during the study period. Cows that had been severely lame 4, 6, and 8 mo previously gave 0.51 kg/d, 0.66 kg/d, and 1.55 kg/d less milk, respectively. A severe case of lameness in the first month of lactation reduced 305-d milk yield by 350 kg; this loss may be avoidable by prompt, effective treatment. Larger reductions can be expected when cases persist or recur. Evidence-based control plans are needed to reduce the incidence and prevalence of lameness in high yielding cows to improve welfare and productivity.     

Lame cows on Australian dairy farms: A comparison of farmer-identified lameness and formal lameness scoring,and the position of lame cows within the milking order

On Australian pasture-based farms, where cows may often walk several kilometers and stand for several hours per day in a crowded concrete yard while they wait to be milked, the potential for lameness to negatively affect animal welfare is of ongoing concern. Several studies have shown that farmers tend to underestimate the incidence of lameness. Further, improving farmer diagnosis/identification of lameness is likely to result in more prompt treatment, which in turn will improve clinical and animal welfare outcomes. We scored 19,154 cows over 50 farms for lameness, in herd groups ranging from approximately 100 to 1,000 cows, as they left the milking parlor. We compared these results with farmer-diagnosed lameness records on the same day. We used a scoring system of 0, walks normally; 1, walks unevenly; 2, lame; and 3, very lame. All very lame cows had been detected by the farmer, but overall, farmers detected only 24% of cows identified by lameness scoring. An analysis of the position of lame cows within the milking order showed that lameness scoring of the entire herd was necessary to detect all the lame cows as only 60% of lame cows appeared in the last 30% of cows to be milked. However, lameness scoring only the last 200 cows to be milked could be used as a screening test to identify herds with a lameness prevalence below a given threshold.     

The impact of clinical lameness on the milk yield of dairy cows

This paper investigates the impact of lameness on milk yield. The dataset includes approximately 8000 test-day milk yields from 900 cows on five farms in Gloucester, UK, collected over 18 mo from 1997 to 1999. The data were structured to account for repeated measures of test-day yield (1 to 10 per cow) and analyzed to account for this autocorrelation. Factors affecting milk yield included: farm of origin, stage of lactation, parity, and whether a cow ever became lame. In clinically lame cows, milk yield was reduced from up to 4 mo before a case of lameness was diagnosed and treated and for the 5 mo after treatment. The total mean estimated reduction in milk yield per 305-d lactation was approximately 360 kg. We conclude that clinical lameness has a significant impact on milk production. This is important information for assessing the economic impact of clinical lameness and its impact on cow health. It adds weight to the importance of early identification of clinical lameness and the urgency of techniques to improve the definition of this highly subjective diagnosis.     

Technical note: Assessing lameness in tie-stalls using live stall lameness scoring

Video stall lameness scoring (SLS) has been shown to be comparable to video locomotion scoring for evaluating lameness in dairy cows housed in tie-stalls and may be a more practical and easier method to measure lameness in a herd. We compared live SLS to video SLS and to live locomotion scoring. A total of 685 lactating cows subsampled from 27 commercial dairy herds were examined for lameness through live and video SLS. Cows scored with the live or video SLS system were scored for 4 behavioral indicators while still in their stall: weight shifting (shift), standing on the edge of the stall (edge), uneven weight bearing while standing (rest), and uneven weight bearing while moving from side to side (uneven). Two observers live scored and video scored for SLS. Lameness prevalence from video SLS and live SLS were similar (31 vs. 30%, respectively). Prevalence of the behavioral indicators varied from 0.59 to 58.2%. Sensitivity and specificity of live SLS was calculated using video SLS as the gold standard for lameness detection in tie-stalls. Sensitivity of live SLS was 0.83 and specificity was 0.94. False positives and false negatives for lameness were 14.4 and 16.8%, respectively. When comparing the prevalence of lameness measured through video or live SLS at the herd level, live SLS for lameness was correlated to video SLS (r = 0.91) with a Cohen's kappa coefficient of 0.79 (95% confidence limit = 0.73–0.84). Average exact agreement in the behavior indicators observed ranged from 80 to 100%. A subsample of 250 cows from 5 herds were scored for live SLS and live locomotion by a third observer. Intra- and interobserver reliability for live SLS and live locomotion scoring were found to have a kappa coefficient of 0.53 (95% confidence limit = 0.43–0.64) when determining a cow as lame through SLS or locomotion scoring. Live SLS was correlated with live locomotion scoring (r = 0.92). However, lameness prevalence was lower when using live SLS (28.4%) compared with locomotion scoring (38%). In summary, live SLS may be an acceptable method to replace video SLS to identify lame cows and rank tie-stall herds in terms of lameness prevalence without having to remove the cows from their stalls or view videos to score; however, it may underestimate lameness prevalence compared with locomotion scoring methods.     

Association between a visual and an automated locomotion score in lactating Holstein cows

Two studies were conducted to evaluate visual locomotion scoring (VLS) and Stepmetrix locomotion scoring (SLS) in detecting painful digit lesions. In study 1, one veterinarian performed VLS. Cows with VLS ≥3 were hoof trimmed and the presence or absence of a painful lesion (PL), defined as a reaction to digital pressure, was recorded. A strongly increasing pattern in the proportion of cows with PL was detected as VLS increased. The proportions of cows with painful lesions were 5.6% (n = 53), 20.1% (n = 78), 55.5% (n = 164), 79.9% (n = 159), and 100% (n = 5) for VLS 1 to 5, respectively. Study 2 was conducted on a different farm. The entire farm was visually locomotion scored by 3 veterinarians on the same day, and the cows were Stepmetrix locomotion scored by walking through the Stepmetrix system. Every cow was trimmed during the following 2 d by 1 of 8 professional hoof trimmers. The 3 veterinarians identified, scored, and recorded any PL. Interobserver agreement for the 3 veterinarians had a kappa coefficient of between 0.45 and 0.48 ± 0.05. In total, 518 cows were used in the analysis, from which 11.2% were identified with a PL. Of the cows diagnosed with a PL, 32.8% were detected with a sole ulcer, 25.9% with white line disease, 13.8% with white line abscess, and 27.5% with other diseases. A receiver operating characteristic analysis was performed; the area under the curve was larger for VLS (0.80; 95% confidence interval, 0.76 to 0.83) than SLS (0.62; 95% confidence interval, 0.57 to 0.66). When performed by trained veterinarians, VLS performed better than SLS in detecting PL.     

Long-term effects of postpartum clinical disease on milk production,reproduction, and culling of dairy cows

Two retrospective studies examining data of 7,500 lactating cows from a single herd were performed with the objective of evaluating the long-term effects of clinical disease during the early postpartum period on milk production, reproduction, and culling of dairy cows through 305 days in milk (DIM). In the first study, data regarding health, milk production, reproduction, and culling of 5,085 cows were summarized. Cows were classified according to incidence of clinical problem (metritis, mastitis, lameness, digestive problem, or respiratory problem) during the first 21 DIM (ClinD21). During 305 d of lactation, cows that had ClinD21 produced, on average, 410 kg less milk, 17 kg less fat, and 12 kg less protein compared with cows that did not have ClinD21 (NoClinD21). Although the interval to first breeding was not different between groups of interest, pregnancy rate through 305 DIM was lower in cows that had ClinD21 [adjusted hazard ratio (AHR) = 0.81]. When individual breedings were analyzed, cows that had ClinD21 presented lower rates of pregnancy per breeding for breedings performed before 150 DIM, reduced numbers of calving per breeding for breedings performed before 200 DIM, and greater number of pregnancy losses for all breedings performed through 305 DIM. The rate of culling from calving through 305 DIM was higher in cows that had a single ClinD21 (AHR = 1.79) and in cows that had multiple ClinD21 (AHR = 3.06), which resulted in a greater proportion of cows leaving the herd by 305 DIM (NoClinD21 = 22.6%; single ClinD21 = 35.7%; multiple ClinD21 = 53.8%). In the second study, data regarding postpartum health and 305-d yields of milk, fat, and protein were collected from 2,415 primiparous cows that had genomic testing information. Genomic estimated breeding values (EBV) were used to predict 305-d yields of milk, fat, and protein. Genomic EBV and predicted yields of milk, fat, and protein did not differ between cows that had ClinD21 and those that did not have ClinD21. In contrast, the observed 305-d yields of milk, fat, and protein were reduced by 345, 10, and 10 kg, respectively, in cows that had ClinD21 compared with cows that did not have ClinD21. We conclude that clinical disease diagnosed and treated during the first 21 DIM has long-term effects on lactation performance, reproduction, and culling of dairy cows, which contribute to detrimental consequences of health problems on sustainability of dairy herds. Replication of our studies in multiple herds will be important to confirm our findings in a larger population.     

Risk factors for reduced locomotion in dairy cattle on nineteen farms in The Netherlands

A 3-point locomotion scoring system was used that incorporated the position of the back of cows while standing and when walking to investigate risk factors for elevated locomotion scores of 1,450 dairy cows on 19 farms in The Netherlands. Each of the farms was visited twice in an 18-mo period from February 2003 to July 2004. At each visit, all milking and dry cows were scored for locomotion by a single observer. Two multivariable regression models were constructed to identify factors associated with elevated mean locomotion score (increased abnormality) and the percentage of cows with the highest score (score 3). Risk factors for increased locomotion score were having a hoof-trimming stall with foot-lifting apparatus compared with not having such apparatus (increase in locomotion score = 0.15), presence of a footbath at the parlor exit or other site compared with not having a footbath on the farm (increase in locomotion score = 0.17 and 0.19, respectively), not providing supplemental vitamins and minerals to lactating cows compared with supplementing animals (increase in locomotion score = 0.17) and feeding corn silage to heifers compared with not doing so (increase in locomotion score = 0.10). The results provide a framework for hypotheses for future investigations of risk factors for high locomotion scores.     

Effects of postpartum uterine diseases on milk production and culling in dairy cows

The objective was to quantify the effect of postpartum uterine diseases on milk production and culling. Data from 2,178 Holstein cows in 6 herds enrolled in a randomized clinical trial were used. Milk production data from the first 4 Dairy Herd Improvement Association (DHIA) test-days and culling data from farm records were collected. Retained placenta (RP; ≥24 h after parturition) and metritis [≤20 d in milk (DIM)] were diagnosed by farm managers using standardized definitions. Farms were visited weekly and cows were examined at 35 and 56 (±3) DIM using endometrial cytology (cytobrush device), vaginal discharge scoring (Metricheck device), and measurement of cervical diameter by transrectal palpation. Diagnostic criteria for cytological endometritis (CYTO) and purulent vaginal discharge (PVD) were established based on a detrimental effect on subsequent reproduction. Statistical analyses were performed using linear mixed models, logistic regression models, and Cox proportional hazard models, accounting for the effects of experimental treatments and herd clustering. Milk production and culling were the outcomes. Primiparous and multiparous cows were modeled separately for milk production. Milk production of primiparous cows was unaffected by uterine diseases. The effect of metritis on milk production was variable over time in multiparous cows: it decreased production per cow by 3.7 kg at the first DHIA test, but was not different at later tests. Retained placenta decreased milk production by 2.6 kg/d in multiparous cows through the first 4 DHIA tests. The projected effects of metritis and RP in multiparous cows were reductions of 259 kg and 753 kg over 305 DIM, respectively; these effects were additive. Neither CYTO nor PVD affected milk production. Culling risks at 30 and 63 DIM were unaffected by RP and metritis. Culling hazard up to 300 DIM was unaffected by RP, metritis, CYTO, or PVD, whether or not pregnancy status, milk production, and displaced abomasum were accounted for. Uterine disease decreased pregnancy rate, which was a substantial risk factor for culling; however, if affected cows became pregnant they were not at greater risk of culling.     

The effect of digit amputation or arthrodesis surgery on culling and milk production in holstein dairy cows

The objectives of the study were to evaluate the effects of digit amputation and arthrodesis surgery performed in the field on culling and milk production during the early postsurgical period. Cows from 3 commercial dairy farms in New York State were recruited for the study. A total of 49 cows on which digit amputation (AMP) was performed were matched with 68 controls (MC-AMP), and 17 cows on which arthrodesis surgery (ARTHRO) was performed were matched with 20 controls (MC-ARTHRO) according to lactation, DIM, and lactation at the time of surgery. Performance was not directly comparable between the AMP and ARTHRO groups because cows were not randomly assigned to the 2 treatment groups. Therefore, each surgical group was evaluated relative to its respective matched control group. Cows with AMP had a significantly lower estimated median survival of 68 d (95% confidence interval; lower = 35 d, upper = 156 d) compared with 585 d (95% confidence interval; lower = 469 d, upper = 699 d) for the MC-AMP group. Total milk production for the first 60 d postsurgery was significantly lower for the AMP (1,533 ± SE = 101 kg) group compared with the MC-AMP (2,121 ± 101 kg) group and for the ARTHRO (1,883 ± 86 kg) group compared with the MC-ARTHRO (2,250 ± 88 kg) group. Septic arthritis of the distal interphalangeal joint was the most common condition treated by surgery, accounting for 70.5% of ARTHRO cases and 73.5% for AMP. Toe necrosis accounted for 14.3% of AMP cases, and retroarticular abscess made up the rest of the AMP (12.2%) cases and 29.5% of the ARTHRO cases. Results suggest that cows that had undergone ARTHRO had a lower culling rate and a faster return to production compared with those that had undergone AMP. Arthrodesis should be considered as a treatment option for deep sepsis of the bovine foot.     

Epidemiology of subclinical hypocalcemia in early-lactation Holstein dairy cows: The temporal associations of plasma calcium concentration in the first 4 days in milk with disease and milk production

The objectives of this study were to characterize the epidemiology of subclinical hypocalcemia (SCH) in Holstein dairy cows by assessing the temporal associations of plasma Ca concentrations in the first 4 d in milk (DIM) with the risk of cows being diagnosed with metritis or displaced abomasum (or both), and milk production across the first 15 wk of lactation. A prospective cohort study was conducted in 2 dairy herds in New York State, in which cows had a blood sample collected daily for the first 4 DIM. A total of 396 Holstein cows (137 primiparous and 259 multiparous) were enrolled. Multivariable Poisson regression models were built to evaluate the associations of plasma Ca concentration at each of the 4 d following parturition with the risk of primiparous cows being diagnosed with metritis and multiparous cows being diagnosed with metritis, displaced abomasum, or both. Similarly, generalized linear mixed models were built to evaluate the associations of plasma Ca concentration with milk production across the first 15 wk of lactation. Plasma Ca concentration was assessed on a continuous scale in all models; dichotomization and SCH classification only occurred in the final models if the Ca concentration variable was meaningful by creating an optimized threshold based on receiver operating characteristic curve analysis. Plasma Ca concentration assessed at 1 DIM was not associated with the risk of metritis in primiparous cows, but an association was observed at 2, 3, and 4 DIM (critical thresholds were plasma Ca concentration ≤2.15, 2.10, and 2.15 mmol/L, respectively). Plasma Ca concentration was associated with the risk of metritis or displaced abomasum diagnosis (or both) for 2nd parity animals at 2 DIM (threshold ≤1.97 mmol/L), and at 4 DIM for 3rd and greater lactations (threshold ≤2.20 mmol/L). Reduced plasma Ca concentration was associated with higher milk production when assessed at 1 DIM in primiparous and multiparous cows, and lower milk production when assessed at 4 DIM in multiparous cows only. For primiparous cows, plasma Ca concentration was not associated with lower milk production at any of the DIM assessed. In conclusion, assessments of SCH at the individual cow level must take into account the DIM of Ca concentration measurement and parity of the cow, as the epidemiology of the disorder was demonstrated to be highly dependent on these variables. This study advances the knowledge of the epidemiology of SCH and better establishes thresholds for optimizing SCH diagnosis.     

Weight distribution and gait in dairy cattle are affected by milking and late pregnancy

There is increased interest in automated methods for lameness detection, such as measures of weight distribution. Still, practical use of such methods depends on knowing the conditions that affect how cows distribute their weight. In 3 experiments, 10, 18, and 12 Holstein cows were trained to stand on a platform that measured the weight placed on each of their legs. The objectives were to evaluate how cows change their weight distribution after milking, after calving, and when standing with the front legs elevated and to evaluate the effect of the udder fill and fetus weight on the gait score. Comparisons before and after milking and before and after calving showed that the weight of milk was carried mainly on the back legs, whereas the weight of the fetus was distributed between front (52%) and back legs (48%). The percentage of weight distributed between front and back legs was not affected by elevation of the front legs. Weight shifting between contralateral legs was greater before calving than after; the weight variability over time decreased by 30% after calving. A full udder increased gait score by 0.3 ± 0.1 and particularly abduction/adduction of the back legs (increased by 83%). Gait score did not change after calving, although the back arch increased by 25%. Therefore, time since milking and state of late pregnancy need consideration when using gait score and measures of weight distribution to detect lameness.     

The hidden cost of disease: II. Impact of the first incidence of lameness on production and economic indicators of primiparous dairy cows

Lameness is a persistent and underreported health and welfare problem in the dairy industry, resulting in reduced cow performance and profitability as well as early culling. The study objectives were (1) to quantify the impact of the first instance of lameness, at different stages of lactation, on production and economic performance, and (2) to further quantify the impacts of the first instance of lameness when only cows that remain in the herd for at least 100 d in milk (DIM) and those that remain for 305 DIM are included in the analysis. A retrospective longitudinal study was conducted using pre-existing data from animal health records and Dairy Herd Improvement Association records. Data were edited based on selected inclusion criteria, yielding a data set containing records from 15,159 first-lactation Holstein cows from 120 herds with year of first calving between 2003 and 2014. Lame cows were assigned to 1 of 4 groups based on when in the lactation the first event of lameness occurred: transition (1–21 DIM), early lactation (22–100 DIM), mid-lactation (101–200 DIM), or late lactation (201+ DIM). Mid- and late-lactation lame cows were also stratified by cumulative milk yield before the lameness event. Healthy cows (i.e., no recorded lameness event) were randomly assigned for each lactation stage, with mid-lactation healthy and late-lactation healthy cows similarly stratified. Production performance (cumulative milk, fat, and protein yield) and economic performance [milk value, margin over feed cost (MOFC), and gross profit] were analyzed using a mixed model with herd as a random effect. Cumulative milk yields were 811 to 1,290 kg lower for lame cows than for healthy cows, with milk component yields undergoing similar reductions. Reductions in milk yield contributed to losses in milk value (?Can$527 to ?Can$1,083; ?US$419 to ?US$862) and MOFC (?Can$510 to ?Can$774; ?US$406 to ?US$616). Higher losses were reported using gross profit (?Can$753 to ?Can$1,052; ?US$599 to ?US$837), which includes all lameness-related costs. Production and performance losses were smaller when 100 DIM and 305 DIM thresholds were applied (i.e., exclusion of cows culled before 100 and 305 DIM, respectively), however, mid- and late-lactation lame cows maintained high levels of significant losses for all 6 variables analyzed. Lameness also led to higher levels of culling, masking losses for transition and early-lactation lame cows in the 305-DIM analysis. Increasing producer understanding of the costs associated with lameness not only serves to provide insight to producers for more informed culling decisions, but may also help producers weigh the costs of adopting new methods and technologies targeted at reducing on-farm lameness.     

Effect of incomplete milking during the first 5 days in milk on udder and reproductive tract health: Results from a randomized controlled trial

The aim of this study was to investigate the effect of an incomplete milking on risk of mastitis and reproductive tract disease. Multiparous dairy cows (n = 878) from 13 commercial herds were enrolled in a randomized controlled trial. Cows were randomly assigned to either a control (milked conventionally) or a treatment group, which consisted of an incomplete milking (10–14 L of milk collected/d) from 1 to 5 d in milk (DIM). Quarter milk samples were collected at approximately 11 and 18 DIM to measure somatic cell count (SCC). Quarters were considered negative for intramammary infection if SCC was <100,000 cells/mL and positive if SCC was ≥200,000 cells/mL. To calculate intramammary infection incidence, negative quarters of the initial samples collected were tested again 1 wk later. This was done to deter incidence of positive quarters. To calculate elimination rate, positive quarters were tested again 1 wk later to detect mastitis elimination. Farmers recorded clinical mastitis events. Cows were also examined at approximately 35 DIM with a Metricheck device (Simcro, Hamilton, New Zealand) for detection of purulent vaginal discharge (PVD) and with an endometrial cytobrush for presence of leukocytes [endometrial cytology for smear (ENDO) and for leukocyte esterase test (LE)]. A threshold ≥3 was used to define a positive PVD or LE test, whereas a polymorphonuclear cell count ≥6% was used to define a positive ENDO. Five generalized mixed models with cow or herd as random intercepts were used to determine the effects of incomplete milking on odds of new intramammary infection, odds of intramammary infection elimination, and odds of a positive PVD, LE, or ENDO status. To investigate time until first clinical mastitis event, a Cox model with a herd frailty term was used. The odds of new intramammary infection and intramammary infection elimination for incompletely milked cows were 0.90 [95% confidence interval (CI): 0.49, 1.7] and 2.9 (95% CI: 1.4, 6.0) times those of conventionally milked cows, respectively. The hazard of clinical mastitis in incompletely milked cows was 0.96 (95% CI: 0.59, 1.6) times that of conventionally milked cows. The odds of PVD, LE, and ENDO for incompletely milked cows were 1.4 (95% CI: 0.89, 2.1), 1.3 (95% CI: 0.88, 1.8), and 1.2 (95% CI: 0.81, 1.7) times those of conventionally milked cows. These results suggest that incomplete milking during the first 5 DIM increases the odds of a decrease in SCC from 11 to 18 DIM but does not affect odds of increase in SCC in the same period. The incomplete milking had no effect on clinical mastitis incidence in the first 90 DIM or on reproductive tract health at 35 DIM.     

Invited review: A systematic literature review and meta-analysis of mortality and culling in dairy cattle

Dairy industries and individual farmers are concerned about mortality and culling of dairy animals. This is because the timing and fates of animals that exit dairy farms have important animal welfare and economic consequences that reflect the conditions under which they are farmed and the efficiency of their production systems. Reports from a few countries have indicated increased incidence of mortality, and occasionally culling, of dairy animals in recent decades, and these changes have been associated with intensification of production systems. Dairy industries and farmers need benchmarks for culling and mortality against which they can compare themselves, as well as improved understanding of the extent of any change and of any associated factors. We reasoned that a systematic literature review and meta-analysis of scientific articles published between 1989 and 2014 would allow us to determine whether these reports were universal, to quantify any change over time, and to investigate whether production systems or study factors were associated with culling and mortality. From 3,275 articles retrieved from databases and manual searching of cited articles, 118 articles were appraised independently by 2 assessors, and 51 articles representing 54 studies were determined to be eligible for review and meta-analysis. We estimated that both the annual incidence risk (IR) and incidence density of mortality of cows had increased significantly from 0.02 per cow and 2.32 per 100 cow-years, to 0.04 per cow and 3.75 per 100 cow-years, an increase per decade of 0.02 per cow and 1.42 per 100 cow-years, respectively. We also estimated that the annual IR of culling attributed to low production had declined significantly from 0.07 to 0.05 and that the IR of perinatal, but not neonatal, mortality had increased significantly from 0.04 to 0.06 per decade. We found no evidence of change in overall annual IR of culling of cows over time or any association between study design factors and the IR or incidence density of culling or mortality. These findings provide benchmarks for describing culling and mortality, and should encourage farmers and researchers in countries with modern dairy industries to discover and implement management strategies to reduce the animal welfare and economic costs associated with these changes.     

Strategies to analyze milk losses caused by diseases with potential incidence throughout the lactation: a lameness example

The objective of this study was to test the hypothesis that lameness incidence in lactating dairy cows decreases milk production compared with controls and to determine the best method of the 5 combinations of 2 study designs (retrospective cohort and retrospective matched cohort) and 3 repeated measures statistical methods: ANOVA (with binary classification of lameness); ANOVA with a lameness index (LAMIX) as the variable of interest; and analysis of covariance (ANCOVA, controlling for mean milk production for the first 3 wk of lactation and with a binary classification of lameness). Data were from 1 dairy farm located near Ithaca, NY, and from cows that calved between January 1, 2004 and January 1, 2007. The LAMIX was defined as −1, −2, −3, −4, and −5 = 1, 2, 3, 4, and ≥5 mo before lameness was detected, respectively; 1, 2, 3, 4, and 5 = 1, 2, 3, 4, and 5 mo after diagnosis, respectively; and 0 = cows that were never lame. With the binary lameness classification analyzed by repeated measures ANOVA, there was no effect of lameness on milk yield. The model was biased because lame cows had higher milk yields before lameness compared with nonlame cows. When the LAMIX was used, milk production before lameness was greater than after lameness (3.1 ± 0.28 kg/d). Yet, point estimates generated for LAMIX were inaccurate because of the multicollinearity detected between LAMIX and week of lactation and because of the inability of adjusting the least squares means for the interaction of LAMIX and week of lactation. Therefore, the most appropriate models were the ANCOVA models (both for the matched and nonmatched retrospective-cohort designs). The estimated losses associated with lameness were 314 and 424 kg/cow per 305-d lactation, respectively, for the matched and nonmatched designs. Furthermore, high milk yield in the beginning of the lactation was a risk factor for lameness.     

High urea and pregnancy or conception in dairy cows: A meta-analysis to define the appropriate urea threshold

Dietary proteins play an important role in reproduction, and increased dietary crude proteins, increased degradability of dietary proteins, and elevated blood or milk urea have been associated with decreased conception and pregnancy in many studies. The aim of this work was to provide a meta-analysis on the relationship between high milk or blood urea and pregnancy or conception, with a focus on defining the appropriate urea threshold associated with this issue. The meta-analysis included 61 different models from 21 papers. The thresholds of urea tested in the various models were built by steps of 1 mM urea. This constructed variable reduced heterogeneity by 61% in the meta-regression. The meta-analysis showed 43% lower odds of pregnancy or conception (odds ratio = 0.57; 95% confidence interval = 0.45–0.73) in cases where urea was ≥7.0 mM in the blood (plasma urea nitrogen = 19.3 mg/dL) or where urea was ≥420 mg/L in the milk compared with where urea values were lower. This threshold is the most suitable with regard to pregnancy or conception success, even if a threshold of 6.5 mM cannot be excluded with certainty. The results also highlighted the possibility of a stronger association between high urea concentrations and pregnancy or conception when high nitrogen exposure occurs before artificial insemination compared with after artificial insemination, but this possibility needs to be further studied. Whether the present results also apply to extensively pasture-based countries remains to be determined.     

The effect of claw horn disruption lesions and body condition score at dry-off on survivability, reproductive performance, and milk production in the subsequent lactation

The objective of this study was to evaluate the effects of claw horn disruption lesions (CHDL; sole ulcers and white line disease) and body condition score (BCS) at dry-off on survivability, milk production, and reproductive performance during the subsequent lactation. An observational prospective cohort study was conducted on a large commercial dairy in Cayuga County, New York, from September 2008 until January 2009. A total of 573 cows enrolled at dry-off were scored for body condition and hoof trimmed; digits were visually inspected for the presence of CHDL. The BCS data were recategorized into a 3-level variable BCS group (BCSG), with cows with BCS <3 placed in BCSG 1 (n = 113), cows with BCS = 3 placed in BCSG 2 (n = 254), and cows with BCS >3 placed in BCSG 3 (n = 206). Cows in BCSG 2 were 1.35 and 1.02 times more likely to conceive than cows in BCSG 1 and 3, respectively. The cull/death hazard for BCSG 1 cows was 1.55 and 1.47 times higher than for cows in BCSG 2 and BCSG 3, respectively. Milk yield for cows in BCSG 2 (44.6 kg/d, 95% CI 43.4-45.8) was significantly greater than that for cows in BCSG 1 (41.5 kg/d, 95% CI 39.8-43.3). Cows with previous lactation days open ≤91 had 1.6 times higher odds of being classified into BCSG 1 at dry-off; cows with previous lactation mature-equivalent 305-d milk >14,054 kg had a similar 1.6 times higher odds of being classified into BCSG 1. Claw horn disruption lesions were found in 24.4% of the cows (n = 140) at dry-off. Cows without CHDL were 1.4 times more likely to conceive than cows with CHDL. Additionally, lesion cows were 1.7 times more likely to die or be culled than nonlesion cows. Absence of CHDL did not have a significant effect on milk yield. These findings highlight the importance of claw health and BCS at the end of lactation on future survival and performance.     

Efficacy of formalin, copper sulfate, and a commercial footbath product in the control of digital dermatitis

The objective was to evaluate the relative efficacy of a novel, commercially available disinfectant agent (T-Hexx Dragonhyde HBC, Hydromer, Branchburg, NJ) compared with formalin and copper sulfate. The hypothesis was 2 sided; therefore, the hypothesis was that the new agent would be better or worse compared with the industry gold standard footbath agents, formalin and copper sulfate. The study was conducted in a large commercial dairy farm located near Ithaca, New York, from June 18, 2009 to October 26, 2009. Two identical studies were conducted, the first comparing Dragonhyde (5% solution, twice weekly) and formalin (5% solution, twice weekly) and the second comparing Dragonhyde (5% solution, twice weekly) and copper sulfate (10% solution, twice weekly). The study design was identical for both studies with 4 pens (physically identical), 2 treatments (Dragonhyde vs. formalin and Dragonhyde vs. copper sulfate), 2 periods (crossing over the treatment within pen), and 3 repeated measures (3 observations per cow: enrollment, wk 2, and wk 4). For study 1, 406 cows were enrolled (n = 201 formalin and 205 Dragonhyde). For study 2, 356 cows were enrolled (n = 189 copper sulfate and 167 Dragonhyde). The adjusted odds of digital dermatitis lesion (DDL) throughout the study period were analyzed by mixed logistic regression model. In study 1, the odds of DDL were 1.36 times higher for the formalin group compared with the Dragonhyde group. In study 2, the data were analyzed by a similar statistical model and the variable treatment did not significantly affect the overall prevalence of DDL. In conclusion, the performance of 3 hoof care products was evaluated and it was concluded that Dragonhyde performed better than formalin and that there was no difference between copper sulfate and Dragonhyde.     

Evaluation of the Dairy Comp 305 module "Cow Value" in two Ontario dairy herds

The study was conducted to evaluate how the “Cow Value” module of Dairy Comp 305 (Valley Agricultural Software, Tulare, CA) performed under commercial conditions. The “Cow Value” module, COWVAL, computes a farm-specific net present value relative to an average replacement heifer for each cow in the milking and dry herd, which allows a ranking of the cows on the farm compared with replacing her with a typical replacement heifer on that farm. The average replacement heifer is used as the baseline for comparison and has a COWVAL of $0. Retaining a cow with a negative COWVAL is projected to be less profitable than replacing that cow with a new heifer. The objectives of the study were to explore trends in COWVAL over and during multiple lactations for the same cows; to describe factors that influence changes in COWVAL from one monthly Dairy Herd Improvement test to the next; and to evaluate the behavior of COWVAL after it drops below a baseline of $0 during the lifetime of a cow. Monthly Dairy Comp 305 backup cow files from 2 On-tario dairy herds between December 1999 and Decem-ber 2005 were used to generate COWVAL and list production, reproduction, and disease data for the milking cows. In total, 1,463 cows and 20,071 tests were analyzed. Within the first 60 d in milk (DIM), COWVAL was unstable and showed large fluctuations over a range of several thousand Canadian dollars (Can$). After 60 DIM COWVAL was relatively stable. The variability from month to month became less as the lactation progressed and the risk of a change in reproductive status decreased. The reproductive status of the cow influ-enced COWVAL: fresh, open, and pregnant cows had a greater COWVAL than cows declared “do not breed.” As parity increased, there was a tendency toward lower COWVAL and smaller monthly changes in COWVAL. The COWVAL of 170 cows dropped below the baseline of $0 after 60 DIM. The COWVAL of 54% of those cows remained below $0, whereas 31.6% had a subsequent COWVAL >$500 (Can$). Farm management should not rely exclusively on COWVAL for culling decisions, particularly for cows that have not had at least 3 milk tests.