Molasses Supplements to Grazing Dairy Cows - On Farm Case Study
Karen Hoffman, USDA-Natural Resources Conservation Service Resource Conservationist (Animal Science)
Molasses supplementation has become an alternative to feeding a grain supplement to pastured lactating cows. This is especially for organic dairies due to high prices for purchased grains and low milk prices due to stagnant consumer demand. Alternatives have been sought that are low cost, yet have a high nutritive value, and that are certified organic. Molasses meets these criteria by having a high energy value, being less expensive than organic grain, 39¢ versus 45¢+ per pound, and a one third substitution rate to corn, thus making it even less expensive on an as fed basis.
However, there is little research to back up the one third substitution rate. Some farms have little or no success feeding molasses to increase milk production or maintain cow body condition, and the older research done in the 1950’s to 70’s was done feeding low rates of molasses to fed cows - not grazing cows, and fed along with grain.
Molasses has a drawback in that it is high in sugar but low in starch. Starch is the energy source required by rumen bacteria to utilize the pasture grass protein that is abundant in cool season grass pastures of the Northeast US and convert it into milk protein. As a result, milk urea nitrogen (MUN) levels can remain high in pastured cows supplemented with molasses. This is accompanied by poor rumen function and energy loss as energy is required to excrete excess nitrogen as uric acid that was not converted into milk protein. This results in loss of body condition, low breeding performance, low milk production, acidosis, and laminitis in cows. There are also issues with excess nitrogen being released into the environment due to the heightened nitrogen levels in the urine and feces.
An observational study was done on a central New York organic dairy farm in 2008 and 2009. This organic dairy farm is feeding molasses successfully. In 2008, 3 lbs. molasses was fed with 1 lb. corn meal/barley grain mix. In 2009, the ratio was changed and done on a seasonal basis: April – May - 2 lbs. molasses w/3 lbs. grain, June - 3 lbs. molasses w/2 lbs. grain, July – 2.5 lbs. molasses w/2 lbs. grain, and in August – October - 2 lbs. molasses w/2 lbs. grain. Molasses was poured over the corn meal/grain to slow intake. The cows were on 80 acres of orchardgrass, red and white clover, forbs, and miscellaneous other grasses pasture. The herd consisted of 56 cross-bred cows (Jersey, Brown Swiss, and Friesian 3-way cross), averaging 1000 lbs each in 2008 and 66 cows in 2009. Seasonal calving starts in March. Data was collected monthly during grazing season. Data collected was body condition score (BCS), milk production, somatic cell count (SCC), milk components, milk urea nitrogen (MUN), and pasture quality. The Cornell Net Carbohydrate and Protein System (CNCPS) model was used to analyze dairy cow diets.
Although the farm appears to be successfully feeding molasses, the dairy cows are thin long after peak lactation when they should be gaining weight back in preparation for their next calving. As the herd was dried off, the BCS was 2.34, lower than ideal for even pastured cows who generally are lean.
Changing the amount of molasses fed seasonally in 2009 produced greater milk protein, 4.3% versus 3.4% in 2008 on a set ration. Although MUN dropped in 2009, 14.5mg/dl on average versus 16.5mg/dl in 2008, it was still above the recommended range of between 8 and 12 mg/dl. The molasses supplementation strategy seemed to work to lower MUN near the 12 mg/dl upper limit of the range in May and June, but had little effect afterward. However, in both 2008 and 2009, milk production dropped off too fast after early lactation dropping 20% in a month from late May to late June versus a normal persistency rate of 3-9% per month. This was thought to be due to low pasture forage quality both years. (Ed. note: This is typical of orchardgrass pastures, if the orchardgrass is not kept vegetative. Intake suffers when cattle try to avoid seed stalks and weathered plant material and/or stems and dead leaves are ingested with the material they do select, lowering the quality of the forage eaten.)
Pasture quality samples revealed that pasture forage by itself was too low in non-fiber carbohydrates (NFC), 20-28% in 2008 and 2009 (38-44% of diet acceptable range) and in starch 1.9-3.4% in 2008 and 2009 (25% of dry matter (DM) intake). Ethanol soluble carbohydrates (ESC) ranged between 3.4-7.7% in 2008 and 2009. These are primarily simple sugars and sucrose, that dissolve in 80% ethanol solution; they are a subset of water soluble carbohydrates (WSC). They are primarily digested in the small intestine and give a true glycemic (blood sugar) response. However, some fructans can be included in this fraction. High ESC generally means a feed will generate a high glycemic response unless there is a high level of fructans in this fraction. Pasture grasses are high in fructans.
Meanwhile, protein ran mostly between 19-30% of DM in the pasture forage samples. The highest protein samples occurred most often in October, but also occurred in May, and September 2009. The pasture samples, therefore, were high in protein for dairy cows needing only 17% of it in their ration.
The CNCPS model was inconsistent in predicting milk production when compared with actual milk production. Sometimes it was quite close and at other times underestimated or overestimated milk production. Two of the underestimates were very low compared to actual milk production measured.
The CNCPS model was also inconsistent in predicting MUN levels as well, underestimating and overestimating quite widely most times. However, even the actual MUN levels were above the recommended range. Predicted nitrogen excretion ranged from 32 to 451 grams/day (0.07- 0.95 pounds/day). As nitrogen excretion goes up to a pound/day, the area of coverage from a cow is such that a urine spot can exhibit a nitrogen application rate of 1000 pounds/acre. Much of this nitrogen is lost to volatilization, leaching, and runoff making it a nutrient management issue. Application rates this high can cause burn spots in the grass. It can also contribute to greenhouse gas emissions.
The study’s conclusions were:
- Sugar from molasses may not compensate for lack of starch.
- Higher starch appears to improve BCS, milk protein, and MUN.
- ‘09 – cows reached a positive energy balance sooner
- ‘09 pasture quality higher
- Cost of organic starch sources is a concern.
- Research on-going
- Rumen dynamics - fermentor
- Animal trial w/treatment groups