The Milk Producer - February 2011 - (Page 38)

RUMINATIONS By Mario S. Mongeon When slimmer is better If you lower key body condition scores from past benchmarks slightly, your cows will have a more productive future idely recognized as a valuable dairy management tool, body condition score (BCS) assessment has been used to recommend the amount of body fat your cows should be carrying at various stages in their lactation cycle. Recent research suggests we need to slim down those recommendations at calving and peak lactation. The five-point North American scale considers 1 as a very thin cow and 5 as an over-conditioned animal. In other parts of the world, the scale may differ but the concept is the same: assess the animal’s body fat reserves. You could be tempted to measure body weight to estimate body fat reserves, but this measurement alone is a poor indicator. Factors such as age, stage of lactation, frame size, pregnancy status and breed would affect your interpretation. Moreover, in early lactation, body fat mobilization takes place as feed intake increases. Increased amounts of feed ingested when rumen-fill is Slimmer cows reap a host of benefits later during lactation. W Ruminations is prepared by Ontario Ministry of Agriculture, Food and Rural Affairs livestock technology specialists to provide information you can use on your farm. greater can sometimes mask actual tissue mobilization. In early lactation, when dairy cows cannot get enough energy through their daily ration to support high milk production, they use body fat reserves to compensate for the energy deficit. This phase can last 50 to 100 days after calving. The BCS profile is similar to an inverted lactation curve. The lowest point of the BCS curve usually shows up around peak lactation. Cows with superior milk production genetics have a higher lactation curve and tend to have a depressed BCS profile. A particular cow’s genetic makeup tends to dictate the target BCS level she strives to achieve at a certain point in lactation. Research findings demonstrate dry matter intake increases when the BCS deviates from cow-specific targets. This dry matter intake increase persists until she replenishes her body reserves. These findings explain why fatter cows tend to have depressed dry matter intake. During the first 30 days after calving, management and feeding have little effect on BCS loss. This is mostly due to hormonal adjustments. After that four-week period, research has shown, management and diet can play an important role in reducing the length of time a cow uses her body reserves. Eventually, when conditions allow it, she replenishes what she lost. This BCS fluctuation is perfectly normal, and improved feeding cannot completely eliminate it. Traditionally, nutritionists came up with early-lactation rations that would provide all the energy a cow needed to prevent as much as possible any body reserve losses. We now know BCS change is a genetically regulated process—beneficial as long as it is not drastic (less than a point of BCS). 38 | February 2011 | MilkPRODUCER

Table of Contents for the Digital Edition of The Milk Producer - February 2011

The Milk Producer - February 2011
Contents
Editor's Notes
DFO Chair's Message
Dairy Update
Industry Roundup
DFC Promotion
Issues Update
Research
Applied Science
Ruminations
Rearing Replacements
Calf Health
Markets
Markets
New 'N' Noted
Back Forty

The Milk Producer - February 2011