Expert Answers - March 20, 2009

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Answer provided by Alvaro Garcia, associate professor in the dairy science department at South Dakota State University.  


Q: With current less-than-favorable milk-feed price ratios, maximizing feed efficiency has become a priority. Will this have any impact on body condition scores?

A: Early in lactation, feed efficiency for milk production is artificially high and results from a low initial feed intake paired with body fat mobilization. As a result, once feed intake starts to increase in the first two months of lactation, the feed efficiency for milk production sharply decreases (hand-in-hand with increased feed intake), and feed efficiency continues to decrease through the remainder of the lactation. After the eighth week of lactation, the energy supplied by the feed tends to match that required for milk production. At this time, the cow starts to gain condition, whereas feed efficiency for milk production continues to drop steadily.

Improving feed efficiency without taking a close look at body condition can thus negatively impact fertility, productivity, and overall animal health. In addition, feeding for body condition is very important to reduce the incidence of health problems. A 1-percent increase in the variation of dry matter intake increases the likelihood of post-calving incidents by 4 percent.

Cows should end their lactation in the body condition that would be desirable at calving (e.g., 3.5) to avoid the need to add weight during the dry-off period. Body condition in excess of 3.5 to 3.75 during the dry period can lead to increased incidences of fat-cow syndrome and fatty livers at calving, compared with condition gained during lactation. On the other hand, underfeeding dry cows — either to make them lose excessive weight and/or as a result of feeding low-quality forages or feed restriction — can lead to body fat mobilization and increased incidence of ketosis.

During the close-up period (three to four weeks pre calving), it is very important to feed a diet with adequate protein/energy to minimize mobilization of fat stores. Try to increase protein and energy concentration in the diet to account for reductions in feed intake that occur during the last week before calving. The objectives are to adapt microbes and stimulate development of rumen papillae, maintain effective fiber, and maintain a reasonable feed intake. With cows having a condition score greater than 3.5, decrease energy intake but maintain weight. When body condition is less than 3.25 in far-off dry cows, start feeding the close-up diet to improve condition.

Bring first-lactation cows to the close-up group four to five weeks before calving, and three to four weeks for second-lactation and older cows. Make sure fresh cows receive a diet rich in protein and energy and with adequate effective fiber. Transition second-lactation and older cows to a lactation diet in two weeks; allow a couple of additional weeks for first-lactation cows. Cows with problems must regain feed intake before returning them to the high-production diet.



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