Managing dairy cow body condition and avoiding lameness have common goals
There has been renewed interest in body condition scoring dairy cattle because of some new technologies that use electronic imaging to measure it, but also because of research showing a relationship between condition scoring and lameness.
Management recommendations for body condition score (BCS) at dry-off have changed over time, with most nutritionists now recommending BCSs in the range of 3.25 to 3.50. This recommendation has flowed from numerous research papers that have shown the benefits of avoiding over-conditioned cows in terms of metabolic diseases, such as ketosis.
Researchers have been investigating the association BCS has in terms of hoof and claw health. The culling rate in Canada related to feet and leg problems is about six per cent per year. Lameness is regarded as an important issue to address for producers, so understanding all the factors that may contribute to reducing lameness is even more important.
German researchers published results from a preliminary study that looked at back fat thickness and energy metabolism in transition cows and the development of sole hemorrhages in the first two months of lactation. Previous work in the United States had shown an association with thin cows (less than 2.5 BCS) at calving having a higher incidence of lameness during lactation. The shock-absorbing role of the digital cushion in the hoof was thought to be reduced in thin cows, which may have impacted claw health.
The German study was conducted at three freestall farms, each with their own management, housing and flooring conditions. All 146 cows received foot trimming twice yearly and were fed a total mixed ration. No routine foot trimming was done on the animals during the study period. Ultrasound measurements of back fat thickness were taken two to three weeks before calving, and again at one, four and eight weeks after calving. Researchers calculated the difference in back fat thickness between the first and last measurement.
A change of more than 10.3 millimetres in back fat thickness after calving has been associated with health problems related to negative energy balance or greater fat mobilization. As well, blood samples were taken and photographs of the hoof were made at one week and eight weeks after calving. All the photographs (each cow, two exams) were examined by a researcher who did not know which cow they came from so was not influenced by knowing the BCS of the animal. Photographs used to score the hooves ranged on a numerical scale from zero to six, with set criteria given for each point. Zero indicated a healthy sole with no alterations, while low scores, such as one or two, were related to very slight hemorrhages in specific locations or yellow colouring and softening of entire sole. The highest score of six indicated clear hemorrhages of the entire sole horn and sole ulcers. The sole in this study was defined as the area with ground contact. Researchers assumed sole hemorrhages would be a preliminary stage to lameness.
For each animal in the study, a total claw score was created at both one and eight weeks post-calving. As expected, there was no significant difference in back fat thickness from the time of drying off until the beginning of lactation since most producers try to manage BCS during the dry period to avoid cows gaining or losing weight. After calving, the back fat thickness declined as energy from stored fat reserves was mobilized to provide energy to the cow for milk production.
Results of the study showed claw health worsened based on the total claw scores calculated during the first two months of lactation. The average increase in the total score per animal for all four hooves was 10.92 for both cows and heifers. When looked at separately, the individual total scores for each cow's four hooves showed cows totaled 7.93, while heifers totaled 15.58, which may have indicated heifers may be at greater risk than cows.
When researchers grouped cows into categories, those with low back fat thickness (less than 18mm) or those with high back fat thickness (more than 18mm) showed cows in the low back fat thickness group had greater claw horn changes. These results support the previous findings, but also showed a fairly high degree of variation with the claw health scores. A controlled research study to add to the field results would provide more evidence of the relationship between BCS, or back fat thickness, as well as sole hemorrhages that could lead to lameness.
When thinking how to apply this to your farm, consider that observing lameness in a cow often relates to an event that began well before you notice it. Managing BCS to avoid metabolic disorders is a profitable approach, but what this research teaches is we may have overlooked the importance of body condition in trying to avoid lameness. Lameness is a classic multifactorial situation involving genetics, environment and nutrition, among other factors. However, as researchers learn more about the role digital cushion thickness plays as a shock absorber, avoiding thin cows at dry-off may also reduce their chance of developing more severe sole hemorrhages. Heifers, because they are still developing, may be more susceptible than mature cows to sole hemorrhage when they have thin body condition.
This article was originally published in the Milk Producer Magazine.
Wilhelm, K., Wilhelm, J., and Furll, M. 2016. Claw disorders in dairy cattle - an unexpected association between energy metabolism and sole haemorrhages. J. Dairy Res.
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