1292 Scientific Reports: Original Study JAVMA, Vol 227, No. 8, October 15, 2005 RUMINANTS T he relationship between lameness and milk yield in US dairy herds has been studied. In a study 1 con- ducted in California, lameness was more common in high-producing cows. In another study conducted in New York, 2 lame cows produced less milk than nonlame cows and the decrease in milk yield was more substan- tial in lame cows in their second or later lactations. More recently, in a study 3 conducted in Florida, lame cows with interdigital phlegmon produced less milk, compared with nonlame cows. The effect of severity of lameness on milk yield has not been investigated by means of objective research methods. Results of recent studies reveal a linear rela- tionship between increasing severity of lameness during the early postpartum period and risk of delayed resump- tion of estrous cycling 4 and conception failure 5 in Holstein cows. Because lame cows spend less time eating 6 and have more severe loss of body condition than healthy postpartum cows, we hypothesized that an increasing degree of lameness would have a greater impact on milk yield. The objectives of the study reported here were to compare milk yield among cows classified as nonlame, moderately lame, and lame and to examine the relation- ship between severity of lameness and milk yield in cows classified as lame during the first 100 days after calving. Materials and Methods Cows and herd management—Cows were from a high- producing dairy herd (rolling herd average milk production, approx 11,818 kg [26,000 lb]/y) of approximately 600 Holstein cows in Florida. Beginning 60 to 70 days after calv- ing, 500 mg of bovine somatotropin a was administered to all cows every 2 weeks. Study design—The study was designed as a longitud- inal study. Five hundred sixty-three Holstein cows that calved from June 1, 2002 through May 31, 2003 were con- sidered for inclusion; 465 cows with complete records were used in the study. Cows were classified into 1 of 3 categories of lameness during the first 100 days postpartum by use of a 6-point locomotion scoring system. 4,5 Milk yield was com- pared among cows classified as nonlame, moderately lame, and lame. In addition, milk yield was compared among cows classified as lame with low (22 to 42), medium (43 to 47), and high (48 to 63) cumulative sums of weekly locomotion scores. The interval of 100 days after calving was chosen as the interval of interest because the incidence of lameness was highest (79%) during that period (Figure 1) and because we expected that the impact of lameness on milk yield would be highest during that period. Data collection—The following data were collected from farm records for each cow: lactation number, calving date, calving season (winter months, January to April and October to December; summer months, May to September), dystocia (yes or no), retained placenta (yes or no), metritis (yes or no), mastitis (yes or no), ketosis (yes or no), days in lactation, and 305-day mature equivalent (ME) milk yield. Diagnosis of lameness—During the first 100 days post- partum, cows were examined for lameness and scored week- ly (on Tuesdays) according to a 6-point locomotion scoring Comparison of milk yield in dairy cows with different degrees of lameness Jorge A. Hernandez, DVM, MPVM, PhD; Eduardo J. Garbarino, DVM, MS; Jan K. Shearer, DVM, MS; Carlos A. Risco, DVM; William W. Thatcher, PhD Objective—To compare milk yield among cows clas- sified as nonlame, moderately lame, and lame and to examine the relationship between severity of lame- ness and milk yield in cows classified as lame during the first 100 days after parturition. Design—Longitudinal study. Animals—465 Holstein cows. Procedure—Cows were examined weekly during the first 100 days after parturition and assigned a lame- ness score by use of a 6-point locomotion scoring system (ie, 0 to 5). Milk yield was compared among cows classified as nonlame, moderately lame, and lame. Among cows classified as lame (locomotion score ≥ 4), milk yield was compared for cows with low, medium, and high cumulative locomotion scores. Cows classified as lame were further examined on a tilt table for diagnosis and treatment of lameness. Results—84 (18%), 212 (46%), and 169 (36%) cows were classified as nonlame, moderately lame, and lame, respectively. Among cows in their second or later lactations, milk yield in lame cows was signifi- cantly lower than that in moderately lame and non- lame cows. In addition, among cows classified as lame, milk yield was significantly lower in cows with high locomotion scores during the first 100 days after parturition, compared with cows with low scores. Most (58%) cows classified as lame had laminitis. Conclusions and Clinical Relevance—Results indi- cate a linear relationship between increasing degree of lameness and decreasing milk yield among cows in their second or later lactations. The locomotion scor- ing system used in this study may be a useful man- agement tool that veterinarians and dairy farmers could adopt for early detection of lameness in dairy cows. (J Am Vet Med Assoc 2005;227:1292–1296) From the Department of Large Animal Clinical Sciences, College of Veterinary Medicine (Hernandez, Garbarino, Shearer, Risco), and Department of Animal Sciences, Institute of Food and Agricultural Sciences (Thatcher), University of Florida, Gainesville, FL 32610-0136. Supported in part by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service (grant No. 2002-35204-12308); the Florida Dairy Check-Off Program; and the University of Florida College of Veterinary Medicine. The authors thank Shawn Ward, Marie-Joelle Thatcher, Megan Elliott, Manon Schuppers, Brooke Bloomberg, and Emily Piercefield for technical assistance. Address correspondence to Dr. Hernandez.