Presentation on theme: "Evaluation of the digital cushion and weight-bearing surface of the bovine foot in response to modifications in housing and rearing practices of calves."— Presentation transcript:
Evaluation of the digital cushion and weight-bearing surface of the bovine foot in response to modifications in housing and rearing practices of calves Mentor: Julie Gard BS, DVM, PhD, DACT and Dr. Ray Wilhite Merial Summer Scholar: Amy Sanders
Lameness One of the two most costly diseases of the dairy industry ( 1). Prevalence in dairy herds is 20-50% of animals depending on age. Establishment of husbandry systems to rear replacement heifers that are adept to withstand the rigors of the industry are badly needed. What kind of changes can be made that can be utilized by today’s dairy farmers that will reduce the prevalence of lameness ?
Focus Investigate a simple modification to the “industry standard” for replacement heifer husbandry that may help: Decrease cull rates of dairy cows Increase the size of the digital cushion Prevent lameness Increase reproduction and milk production
Hypothesis Heifer claws will remodel in response to environmental conditions/stressors Specifically, the digital cushions will become larger in response to the stimulation of increased exercise and housing on variable terrain Life-long impact on animal health, welfare & productivity by decreasing the likelihood of lameness that is frequently seen during adulthood.
Preliminary Data – Study I Performed with eight bull calves Control group reared in accordance with industry standard practices Treated group were allowed free access to a half mile long lane where they walked for a total of at least two miles a day on rocky terrain for 4 months time. CT with 3-D analysis of P2 and P3 of the right rear foot from each calve was performed with Mimics® medical image processing software. Statistical analysis by ANOVA showed that the surface areas of the bones of the digit were significantly (P 0.05) larger in the treated calves vs. the control calves. This data indicates that bovine feet undergo structural adaptation in response to mechanical usage.
Preliminary Data – Study II Performed with 20 bull calves Control group (n=10) reared in accordance with industry standard practices Treated group (n=10) were allowed free access to a half mile long lane where they walked for a total of at least two miles a day on variable terrain (grass, rocks, & dirt) for 4 months time. MRI & 3-D analysis of the digital cushion of the right front and rear feet from each calve was performed with Mimics® medical image processing software. It was found that the treated group had a positive percent difference in the volume and the surface area of the digital cushion, 37.10% and 18.25%, respectively, in comparison to the control group, when corrected for weight. This data also indicates that bovine feet undergo structural adaptation in response to mechanical usage.
Significance/Literature Support Lameness has been described as one of the two most costly diseases in the dairy industry due to the significant negative effects on the well-being and economic productivity of beef and dairy cattle  “...lameness is the most significant challenge for the dairy industry to overcome given obvious disruption of animal welfare and severe economic losses” [2,3,4] Problems with lameness have the potential to lead to other production problems such as decreased milk production, reproduction, & mastitis Cows detected with clinical lameness in the first 70 days in milk were 25% less likely to become pregnant compared to non-lame cows .
Significance Lameness can result in earlier culling (removal from the herd by selling) of animals as well as lower carcass weight, conformation class, and fat cover class and hence a lower carcass economic value. Each episode of lameness is reported to cost between $302 and $446 with cost increasing with the severity of the lameness [5,6]
Protection from the Digital Cushion Housing has been shown to make a significant impact on the strength/laxity, laminar morphology, connective tissue, and biochemistry of the sole . The digital cushion functions as a shock absorber and is protective to the structures underneath [2, 7]. Decreases in the thickness of the digital cushion in cattle are related to contusions with the claw horn capsule and such contusions are a consequence of the lesser capacity of the digital cushion to dampen the pressure exerted by the third phalanx on the soft tissue beneath [2, 8].
Importance of the Digital Cushion In a study by Bicalho, the prevalence of sole ulcers and white line disease was significantly associated with the thickness of the digital cushion; with cows in the upper quartile of digital cushion thickness had an adjusted prevalence of lameness 15 percentage points lower than the lower quartile . Digital Cushion: - 3 parts – middle, abaxial & axial Raber et al., 2004 http://www.sciencedirect.com/science/ar ticle/pii/S1090023303000534
Measurement of the Digital Cushion The use of ultrasonography to measure the digital cushion was based off of Bicalho’s study in which the thickness of the digital cushion was measured ultrasonographically from the junction of the heel and sole where a typical sole ulcer is located.  Also in previous studies, the measurement of the digital cushion was based upon age and lactation status while finding a correlation with the fatty acid content. . Our proposal is basing the measurements of the deep digital flexor compared to the digital cushion off of the environment that the heifer is raised in after weaning.
Method Control Group 6 months: 299 lbs 6 months: 339 lbs 5 months: 374 lbs 8 months: 452 lbs 8 months: 558 lbs 9 months: 604 lbs 8 months: 608 lbs Treated Group 7 months: 344 lbs 6 months: 348 lbs 6 months: 354 lbs 8 months: 421 lbs 8 months: 458 lbs 9 months: 458 lbs 9 months: 518 lbs 14 Holstein heifers with random assignment of seven in each group
Experimental Design All calves were reared in accordance with the current accepted practices of the dairy industry. At the randomized ages from 6-9 months Control group was raised according to industry standards of the dairy husbandry at E.V. Smith Extension Unit Treated group was maintained on a half mile long lane containing variable terrain at the North Auburn Beef Experiment Station. Pedometers were placed on each group for the length of one week to determine steps/miles walked.
Treated Group Encouraged to walk at least two miles per day by placement of food and water on opposite ends of the lane. Goal study period is 13-18 months depending on the age of the heifers on day zero of study.
Method Calipers were used to measure the width and length of the medial and lateral claws of the left fore, & left rear legs of both groups The digital cushions and deep digital flexor tendons of both groups were measured by ultrasound examination using a 6 MHz transducer at monthly intervals. The Calf Number, Age, Body Condition Score, and Weight were all recorded as well along with the data.
Placement of ultrasound probe was the heal bulb at the level of the coronary band. The heel bulb was cleaned with alcohol prior to ultrasound examination
Ultrasound Utilization The 6 MHz transducer probe was placed on the bulb of the heel of each claw at the level of the coronary band (Figure 1) Measurements were recorded of the deep digital flexor and the digital cushion. (Figure 2) All calves were examined by ultrasound at day 0 & at monthly intervals.
DAY ZERO: Control Group
Day Zero: Treatment Group
DAY 30: Control Group
DAY 30: Treatment Group
Results Control Treatment
Results Currently, there is only a small difference between control and treated groups which may be attributed to normal variation among animals and from growth Additional time is necessary to allow enough time for remodeling of tissues so recheck at monthly intervals. The ultrasound method employed seems to be a viable tool for monitoring of the digital cushion of cattle There was difference, however, in the health of the feet of the calves. The control group had cases of epiphysitis, and dermatitis due to wet pasture We believe the rocky terrain pasture didn’t have problems because it was drier and the movement of the calves helped keep them from standing in wet areas.
Results of Pedometers Pedometers clipped onto cow leg straps were placed on four heifers from each group over a period of one week. Only one pedometer from each group had results. Control group= 5.1 miles total= 0.73 miles a day Treatment group= 13.1 miles total = 1.9 miles per day
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Special Thanks Dr. Julie Gard Dr. Debra Taylor Dr. Merilee Holland Leah Guidry Megan Schnuelle Will Justus 4 th Year Ambulatory and Therio Students