Achieving the optimal balance of protein to carbohydrates in the rumen will make the rumen more efficient in growing microbes and produce the most power.
Recent years have not been kind to dairy farmers as milk prices have once again sunk to unmanageable lows and the cost of purchased feeds shows little sign of dropping. Feeding cows during this economic downturn remain challenging for most dairy farms. There’s just no easy way to keep throwing money at the herd when the feed bill continuously consumes a larger portion of a dwindling milk check.
The national Milk-Feed Price Ratio, monitored by the University of Wisconsin, has dropped below 2.0 for April and May of 2016, verifying that there isn’t a lot of money left after paying the feed bill on the average dairy farm. This metric measures the average monthly milk price received around the nation and compares it to the cost of a theoretical 16 percent crude protein diet fed to milk cows. The ratio aids in evaluating if a dairy farmer can “afford to produce milk” depending on what the milk price may be relative to the feed cost. The conventional thought has been that when the ratio is 3 to 1 or greater, dairy farming tends to be profitable.
During the past 10 years, this ratio, calculated monthly, has made it to 3 to 1 only a few times, with most ratios remaining in the lower 2 to 1 range. The ratio dropped to its lowest point of 1.3 to 1 during mid-2012 when feed prices were exceptionally high. During 2014, despite record high milk prices, the ratio made it only as high as 2.96. As low milk prices continue during 2016, challenges to feeding dairy herds remain.
Every dairy farmer must decide how to feed cows and what level of milk to support when times are trying. To cut costs, diets are often reformulated with less expensive, less nutritious feedstuffs. This is one option. However, the single driver when altering diets to compensate for feed costs should be to ensure the rumen remains healthy. When rumen activity, fermentation and microbial growth are compromised, cows will quickly diminish in productivity – often resulting in even greater loss of net revenue.
The rumen can be likened to a large container that houses a continuous fermentation process. Microbes – mostly bacteria – in the rumen do the fermenting. However, these microbes also need nutrients to live and multiply. Their life cycle occurs while they digest forages and other carbohydrates. In recent years ruminant nutritional research has focused heavily on digestion and passage rates of various carbohydrates and matching them with a protein that provides adequate levels of nitrogen at the most opportune time. This is done to keep a large, healthy microbial population in the rumen.
Think of an efficient rumen as a smoothly running automobile engine: For it to run efficiently and develop the greatest amount of horsepower, the gasoline and air mixture must be correct. If there is too much gasoline for the amount of air available, the engine will run too rich and may flood out. If there is too much air for the amount of fuel available, the engine will be starved for gasoline, run too lean and not be able to deliver the desired power. Achieving the optimal balance of protein to carbohydrates in the rumen will make the rumen more efficient in growing microbes and will produce the most power.
In a cow’s diet, carbohydrates are the primary source of energy and proteins are primarily a nitrogen source for rumen microbes. When microbes ferment carbohydrates in the rumen they produce volatile fatty acids (VFA). VFA provide up to 80 percent of a cow’s energy needs. Slowing down fermentation reduces VFA production and energy available to the cow. At the same time, microbes must use nitrogen coming from peptides and other nitrogen sources from the dietary protein in the feedstuffs. The larger and more robust the microbial population in the rumen is, the more metabolizable protein available for digestion in the small intestine.
The challenge in trying to achieve this optimum protein and carbohydrate balance is that often there is either too much rapidly degradable carbohydrates relative to the available rumen degradable protein or too much rumen degradable protein for the microbes to utilize.
Carbohydrates and proteins are degraded at different rates in the rumen. The challenge in attaining an efficiently operating rumen that will optimize microbial growth is to match up the faster digesting carbohydrates with more rumen soluble proteins and, at the same time, keep enough nitrogen available to ferment the more complex, slower digesting carbohydrates such as hay. Excessive protein in the ration may lead to an over-production of ammonia, which is a potentially toxic situation. Excessive levels of highly fermentable carbohydrates in the ration can result in an acidotic rumen. Both situations represent lost opportunity to the dairy farmer.