Nutritionist e-Network - October 2012

The power of meta-analysis
In the January 1998 issue of Dairy Herd Management, an initial effort was made to show the positive benefit of yeast culture on milk production. The article referenced eight studies that had been completed to date, with most of the studies showing a benefit from yeast supplementation. To read that story and see the studies, click here. Now, things have become a lot more sophisticated. A meta-analysis has been completed on the effects of feeding yeast culture, drawing upon an extensive review of literature. Thirty-six separate studies are included. In this month’s edition of the Journal of Dairy Science, the authors point to the power of the meta-analysis approach. Meta analysis provides the complete breadth of information relating to a specific treatment (and specific product) that can reduce the uncertainty often seen in small individual studies, the authors said. And, by the way, the meta-analysis did affirm the value of a commercially available yeast culture. Read the abstract.

Yeast-derived protein as a substitute for soybean meal
Everyone knows about the high cost of soybean meal. Prices have exceeded $500 per ton in many parts of the U.S. And, this has prompted people to look for alternatives. One alternative may be yeast-derived microbial protein. In this month’s edition of the Journal of Dairy Science, researchers from South Dakota State University and Alltech Inc. report that substituting a portion of soybean meal with yeast-derived microbial protein increased the percentage of total solids in milk and tended to improve energy-corrected and fat-corrected milk production in high-producing dairy cows consuming high-forage diets. The authors did acknowledge that further investigation is needed, and theirs was a nutritional comparison rather than an economic comparison. Read the abstract.

What causes heifer weights to be so variable?
Canadian researchers took a look at just how variable heifer growth rates are between farms. To do this, they measured the heart girth circumference of 12- to 17-month-old heifers from 33 different farms in British Columbia. They converted the values to estimate bodyweight. They also analyzed the effect of several factors, such as weaning method, time between weaning and moving to a new pen, size of the heifer group, frequency of regrouping heifers and times per day heifers were given fresh feed, on bodyweight. Only one variable was able to account for among-farm variation in heifer bodyweight, and that was average weight gain during the pre-weaning phase (i.e., 0 to 2 months of age). “These results show considerable among farm variation in heifer weight gains, indicating that some farms are doing well, while others could improve performance,” say the researchers. “Farms able to rear faster-growing heifers were also rearing faster-growing calves, suggesting that management of milk-fed calves is especially important.” The results were reported in July at the American Dairy Science Association’s annual meeting in Phoenix.