Expert Answers - Aug. 19, 2011

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The following answer was provided by Al Kertz, Dairy Field Technical Service with Milk Specialties Global Animal Nutrition.


Q: With very high corn prices, what lactating cow feeding program strategies and alternatives might be attainable? 

A: The first strategy is always related to forage quality and quantity. Forage cost and availability are baselines that must be initially established. If forage quality is high, and NDF digestibility is the best single indicator of that quality, then forage quantity and concentration in the total mixed ration (TMR) can be maximized. While 60 percent forage in the TMR on a dry matter basis has generally been considered on the high side, some dairies with very high quality forages have been able to push that to 70 to 75 percent. When forage NDF digestibility is high, rate of rumen digestibility, lesser rumen fill, and lower rumen residence time allow for higher dry matter intake (DMI) than might normally be expected with lower-quality forages. 

Increasing energy density and energy intake can be more challenging with higher-forage diets. An early lactation trial beginning at 12 days in milk and lasting 15 weeks looked at two levels of forage (40 and 60 percent), and with and without a fat supplement (Weiss, W. P. and J. M. Pinos-Rodriguez.  2009,  Journal of Dairy Science. 92:6144-6155.) There were 13 Holstein cows and five first-calf heifers per treatment, and treatments were either 40 or 60 percent forage (2/3 corn silage 1/3 alfalfa silage blend) and with or without 2.25 percent of the fat supplement. Note first that there was no decrease in DMI when the fat supplement was included in either forage level treatment. This is critical because if the inclusion of a fat supplement decreases DMI, then the value of that inclusion is considerably diminished. At the higher 60 percent forage level, cows put the increased NEL intake into their body condition (P <0.05) in support of the hypothesis that at lower body condition cows may replenish that energy reservoir first to a certain set-point before they put additional energy into milk. Note that both DMI and accompanying NEL intake were lower with 60 vs. 40 percent forage treatments. Cows in the 40 percent forage diet with fat supplement put most of their additional energy intake into milk (P<0.05) once their body condition reached an average of 2.9.

Another strategy is to partially substitute starch energy from corn with sugar energy sources. Extensive studies were done with various whey byproducts in the 1970s and 1980s at South Dakota State. They showed that these byproducts, with their lactose and mineral content, helped maintain both milk yield and fat composition, and even increased milk fat percent in some studies. Lactose fermentation in the rumen seems to favor butyric acid producers, and the mineral content enhances rumen turnover. These two factors enhance milk fat concentration. More recent studies at the Wisconsin USDA Dairy Forage Lab and Ohio State also showed the feasibility of partially replacing starch with sugar sources.

In summary, always try to grow or use the best forages, maintain DMI, and then look for opportunities to increase energy intake via fat supplementation or to maintain energy intake with sugar sources when seeking alternatives to reducing corn inclusion levels in TMRs.



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