Automated Body Condition Scoring (BCS)
New imaging technology hooked up to a computer will take the guesswork out of body condition scoring
You will soon be able to add an automated body condition scoring (BCS) system to your precision management tool box. This valuable tool will let you predict a dairy cow's energy status, as well as potential health and reproductive problems.
BCS, around since the early 1980s, monitors dairy cow body fat reserves. In North America, we use a five-point scoring scale. A score of 1 is considered very thin and a score of 5 is considered obese. Differing scales in other countries use the same principle.
If you were to monitor a cow's BCS regularly, from onset to end of lactation, and then draw a graph, it would be a mirror image of the lactation curve. You would expect to see a low point in the BCS at the same time the cow's lactation peaks. As milk production decreases, the cow slowly builds her reserves back up, until the end of her lactation.
Decreased BCS in early lactation is perfectly normal, and cannot be totally eliminated through improved feeding. Some cows tend to lose more than others under similar conditions. The genetic makeup of these animals could well be a factor.
In recent studies, BCS variation of early-lactation cows was monitored when environmental factors, including feeding, were kept constant.
Contrary to what you would expect, BCS variation was unrelated to potential inadequate feeding, suggesting BCS variation was under genetic control.
One study found up to 60 per cent of BCS variability within a group of similarly managed animals can be attributed to their genetic makeup. Another recent review of BCS showed a negative relationship between dry matter intake and body condition score.
Evaluating body condition score is somewhat subjective and has limitations. Very thin cows will have little subcutaneous fat - fat just under the skin. Assessing remaining body reserves with precision can be difficult.
At the other end of the BCS scale, a fat cow with substantial sub-cutaneous fat may have greater reserves than expected since abdominal fat reserves cannot be accounted for.
When more than one person is assessing BCS in a herd, variations may occur. Variations can increase depending on whether the score is based solely on a visual appraisal or the cow has been palpated as well.
Studies indicate visual appraisal tends to lead to greater variation between assessors. Training and consultation between them can overcome this problem to a certain extent.
The vast majority of studies have demonstrated the optimum body condition score at calving should be between 3.0 and 3.5 for Holstein cows. As the calving BCS increases, a reduction in milk yield and protein is observed but milk fat percentage tends to increase.
The amount of bodyweight lost between calving and conception as well as the rate of this loss seems to influence the offspring's sex. Data analysis seems to associate less bodyweight loss or greater bodyweight gain between calving and conception with a greater likelihood of a male calf. Similar findings have been made recently in horses as well as humans.
A 2006 analysis of more than 76,000 BCS records from about 3,000 lactations generated by 1,100 cows concluded a bull calf was 1.85 times more likely to be born when the mother lost no BCS from calving to conception compared to a cow that lost 1 BCS unit. This increase in odds is equivalent to a 66 per cent probability of a male calf birth.
Simpler method welcome
While BCS is a valuable tool, it is a time-consuming process, especially if you want to assess your whole herd every month. Finding simple ways to monitor body fat reserve would be welcome.
Simply monitoring bodyweight variation by weighing cows on a scale has a major pitfall as a way to keep an eye on BCS. Research has shown bodyweight variation alone is a poor indicator of body fat reserves. For example, a few weeks after calving, a cow consumes more feed every day. This can mask decreased body reserve. Similarly, she will have a net weight gain as gestation progresses, but the growing calf can mask the mother's decreased body fat.
In the last few years, however, other ways to efficiently assess BCS have been studied. Digital, laser reflection, thermal and ultrasonic imaging all have the potential to automate BCS assessment. Enhancing the effectiveness of an automated BCS system will be associating the imaging technology with a computer model. This model would include other parameters such as a cow's parity, days in milk and bodyweight, as well as previous BCS data to accurately predict body condition score and body condition score variation.
Such a system is just around the corner. To learn more about it, plan to attend the Precision Management Conference in Toronto from March 2 to 5 to hear a presentation by Dr. Jeffrey Bewley from the University of Kentucky, one of the many experts at the conference. His recent work includes economic assessment of Precision Dairy Farming technologies, body condition scoring and temperature monitoring.
J.M. Bewley et al. Potential for estimation of body condition scores in dairy cattle from digital images. Journal of Dairy Science Vol. 91 No. 9, 2008; J. r. Roche et al. Invited review:
Body condition score and its association with dairy cow productivity, health and welfare. Journal of Dairy Science Vol. 92 No. 12, 2009; I. Halachmi et al. Cow Body Shape and Automation of Condition Scoring; Journal of Dairy Science Vol. 91 No. 11,2008.
This article first appeared in the February 2010 Ruminations column of the Ontario Milk Producer magazine.
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