Monitoring Body Condition Score of Dairy CowsBody condition score (BCS) assessment is a recognized management tool used to estimate the body fat reserves of an animal. The scale used in North America is the five point scale where 1 is a very thin cow and 5 is an over conditioned animal. In early lactation, when dairy cows cannot get enough energy through their daily ration to support high milk production, the animals will utilize body fat reserves to compensate for the energy deficit. This phase can last from 50 to 100 days post calving. During the first 30 days post calving, management and feeding will have little effect on BCS loss. This is mostly due to hormonal adjustments. After that four week period, management and diet can play an important role at reducing the length of time during which the cow will use her body reserves. Eventually, when the conditions allow it, the animal will replenish what was lost. In organic dairy herds, the organic standards state that the amount of concentrates fed to cows cannot exceed 40% of the total daily dry matter. This limitation may impact on the degree of body fat mobilized by cows in early to mid lactation, especially those cows producing significant amounts of milk. A cow loosing too much body fat in early lactation may encounter some problems later on so, close monitoring is crucial. The BCS profile is very similar to an inverted lactation curve. The lowest point of the BCS curve usually shows up around the time of peak lactation. Cows with superior genetics for milk production will have a higher lactation curve and will tend to have a depressed BSC profile. The genetic make up of a particular cow will tend to dictate the target level of BCS a cow will strive to achieve at a certain point in lactation. Usually, dry matter intake will increase when the BCS deviates from cow specific BCS targets. This dry matter intake increase will persist until body reserves are replenished. Even though dry matter intake will be greater for animals in the process of replenishing their reserves, when formulating the ration for an organic dairy herd, it is important to account not just for milk production but also for the increased energy requirements in order to allow the animals to replenish their body reserves before drying off. This is why monitoring BCS in mid to late lactation is so critical since it is during this period that the intended calving BCS can be more efficiently managed to achieve the optimal objective. It is less efficient to adjust the BCS in the dry period. Bear in mind that this fluctuation of BCS score is perfectly normal and cannot be completely eliminated by improved feeding in the first few months of lactation. Traditionally, nutritionists used to come up with early lactation rations that would provide all the energy required by the cow to prevent as much as possible any body reserve losses. We know now that it may not be economical, practical or even achievable under organic standards. BCS change is a genetically regulated process that is in fact, beneficial as long as it is not drastic (less than a point of BCS). For first calf heifers, their inability to achieve a rapid gain of BCS after the lowest BCS point highlights the necessity for specific management practices for these animals in order for them to attain optimal BCS at their second calving. This includes factors such as the use of a separate milking heifer group, ensuring adequate bunk space and minimizing situations that permit competitive behaviours from boss-cows towards subordinate animals. We need to keep in mind that optimal BCS at calving is an important factor influencing the fertility outcome later in lactation. The effect of energy status (BCS at a specific point in time) and energy balance (BCS gain or loss and rate) on reproductive performances is well documented. In fact, energy balance is probably the most important non-management factor to influence reproductive performance. The most recent studies tend to demonstrate that successful pregnancy can be achieved earlier when the BCS low point and reserve replenishment happens early in lactation. Furthermore, it seems that the optimal BCS at the onset of the breeding period should lie between 3.0 and 3.5. When BCS is above or below the 3.0 to 3.5 range, the proportion of cows detected in heat decreases rapidly. We know that cows with high BCS at calving were more at risk of coming down with metabolic problems post-calving. Recent research demonstrates that the extent of over-conditioning does not need to be significant to substantially affect the odds of metabolic problems showing up. For example, a 2006 study reported a 30% increase risk of milk fever if a cow BCS was greater that 3.5 at calving. Similarly, another study reported a doubling of the risk of ketosis in dairy cows when calving BCS was greater than 3.5 compared to cows calving at 3.5. In general, it appears that over-conditioning (BCS greater than 3.5), not low BCS predisposes cows to an increased risk of metabolic disorder around calving time. BCS has also been linked to lameness. In light of recent findings, it seems that previous BCS recommendations need to be thinned down a bit. Optimal BCS at calving should be between 3.0 and 3.25 and the loss of BCS after calving should be no more than 1 point of BCS to a lowest score of 2.25. Optimal BCS at calving should be between 3.0 and 3.25. Management PracticeOptimal BCS at calving - 3.00 to 3.25
BCS variation of 1 point and lower point greater than 2.5
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