Karen Hoffman, USDA Natural Resources Conservation Service
Adapted with permission from: Mendenhall, K. (ed.) 2009. The organic dairy handbook: a comprehensive guide for the transition and beyond. Northeast Organic Farming Association of New York, Inc., Cobleskill, NY. (Available online at: http://www.nofany.org/organic-farming/technical-assistance/organic-dairy, verified 18 July 2012).
One aspect of organic dairying some farmers struggle with is the change from a stored forage feeding program to a pasture-based feeding program and back again in the fall or early winter. Even experienced graziers can find this seasonal shift to be a challenge, due to differences in crops from year to year or the varying end date of the grazing season.
Changing from lower-quality stored feeds to high-quality pasture is much like changing silos. If changed too quickly, milk production drops until the cows and rumen microbes become accustomed to the new feed. The rumen microbes are especially sensitive to sudden changes because they need time to shift their numbers and types to those that are more adapted to higher-quality forage.
Spring Shift Management Considerations
- Start grazing when the grass is three to four inches tall. Cows should be out one to two hours--left on grass longer, they eat too much and refuse much of the barn ration.
- Over next few days, gradually increase time on pasture until they are out full-time.
- The three- to four-inch forage height quickly becomes six to eight inches, due to rapid spring growth.Therefore, it is recommended that the minimum grazing height be six to eight inches after spring flush. Grazing at three to four inches past spring flush results in over-grazing and unproductive pastures.
- Cows will gradually refuse more feed in the barn.
- First, reduce protein forages such as haylage, baleage, and dry hay.
- Next, cut back the amount of protein from grain or concentrate as cows increase intake of protein from pasture.
- If feeding a total mixed ration (TMR), mix for five to ten fewer cows (depending on herd size) each day as refusals increase.
- When TMR is less than 70% of a full ration, reduce the protein supplement by one pound every three days.
- When TMR is less than 50% of normal, check the protein and NFC levels to ensure balance, and evaluate if reformulation is needed.
- After seven to ten days, the ration should have less than 10 pounds dry matter from stored forage, pasture dry matter intake should be greater than 15 pounds.
- Grain mixes should be below 12% protein.
- Protein concentrates should be fed at less than one pound per cow if other forages are fed.
- Do not feed protein while the cows are on pasture if it is the main forage in diet.
Through the spring, grasses and clovers grow rapidly and can easily become over-mature and unpalatable to your animals. Strive to turn cows onto pasture in the vegetative stage of growth when it is highest in quality, approximately six to eight inches in height. If pasture height gets ahead of you, look for where the grass is the right height and quality and put the cows there. Harvest the over-mature pasture for hay, haylage, or baleage—there are no rules that say you have to graze all the paddocks before going back to the first one, that paddocks cannot be skipped, or that the same sequence of paddocks needs to be followed every rotation. If cows are turned out where the grass is best, cows will maintain their intake, rumen bugs will not have to adapt, and consistent milk production will occur (Hoffman et al., 2000).
In the fall, concerns about changing to new feeds are essentially the same. There are, however, a few new challenges. The stored forages are most likely from the recent growing season. Since no two growing seasons are the same, the quality of forages will be different from what was fed in the spring. It is hard to predict how the cows will respond to the new forages in terms of both intake and performance. Predicting the end of the grazing season is difficult. If the shift to stored forages comes too early, it may not be possible to maximize all remaining high quality pasture. Likewise, if the feed change begins too late, the pasture could run out before introducing the stored forages.
Predicting the end of the grazing season is different every year due to weather and management of the pastures. It is important, however, to try to predict the last day of grazing using simple planning techniques.
Technique to Predict Final Grazing Day
- Walk the paddocks at least once a week beginning in September.
- Measure the total amount of pasture dry matter (DM) available.
- Once total pasture cover is known, divide it by the total amount of pasture DM needed per day.
- The total pasture DM needed per day approximates the remaining number of grazing days if the feeding program stays the same.
- When significant differences in total available grass vary week to week, begin the shift to stored forage.
Strategies for transitioning feeding in the fall are similar to the spring transition except that the steps happen in reverse. Introduce or increase stored forages in the barn. Cows will stay in the barn at night once the temperatures begin to fall below 35°F (unless the plan is to outwinter). Eventually the amount of time cows spend on pasture gradually diminishes, especially after a frost kills the grass and there is little to no new growth. At this point, the winter ration begins because the majority of their intake will be provided in the barn.
Changing from stored forage to pasture and back again may not be the only ration changes needed. Rumen bugs cannot adapt quickly to abrupt diet changes. Thus, manage diet changes slowly if, for example, there are two silos of haylage, major differences between cuttings of hay or baleage, or if significant quantities of forage have been purchased.
With a little planning, the need to change forages can be predicted and they can be tested for quality beforehand. If there are significant quality differences, begin introducing the new forage before the old one runs out. The easiest way to do this is to substitute two pounds of new feed for old per cow every few days. If there are large differences in protein or energy between the two forages, gradually shift the supplements to account for that difference.
Hopefully, diet transitions will be minimal during the winter confinement and stored forage feeding time. Maintaining consistent high-quality forages will reduce the number of changes needed, help to keep costs down, and maintain milk production.
Many forage-type crops can extend the grazing season, both in the spring and in the fall. These include cereal grains such as winter rye or winter wheat for early spring grazing and a variety of brassicas for late fall grazing. Stockpiling some species of grasses also works well in the fall, although this strategy is better suited for animals that are not milking heavily.
From a nutritional standpoint, cereal grains planted in the fall and grazed in the spring are very high in quality. Similar to cool season pasture, they have over 20% CP and fiber digestibility over 75%, so long as the cows graze them in the vegetative growth stage before the boot stage (Cerosaletti and Fields, 2008). The ration of these grains can be the same as your spring pasture ration. These crops begin growing in late March or early April, allowing for grazing to begin two to three weeks earlier than traditional pasture and three to four times in the spring, depending on weather conditions. This may allow for more pasture acres to be harvested for hay in the spring. Furthermore, cereal grains work well as a cover crop on land being renovated for pasture or on land where annual crops are planned.
Brassicas such as turnips, rape (swedes), and kale are options for either mid-summer grazing or extending the grazing season in the fall. Nutritionally, brassicas range from 12% to 18% protein and at more than 85%, are some of the most digestible forages. They also have high water content. Cows should only graze brassicas for a short time each day, obtaining the majority of their intake from other forages. Health problems can result from too much wet and highly digestible forage, and they can cause an off-flavor in the milk, especially if grazed within a few hours of milking. If trying brassicas, transition animals to them slowly to prevent rumen upset and continue to feed the same ration, but increase the amount of fiber with additional dry hay.
Stockpiling grasses, by allowing pastures to grow without harvesting from mid-August onward, is another method to extend the grazing season. However, the nutritional quality of the grass declines over time, so it may not be appropriate for milking cows. Stockpiling may be a good option for farms that operate a seasonal dairies where the cows are in late lactation through the fall, or if grazing youngstock or dry cows on stockpiled forage.
Research from the University of Wisconsin showed that stockpiled tall fescue and orchardgrass maintained the best quality after frost, but reduced the CP levels by 2% from October to December (Hedtcke et al., 2002, and Paine and Barnett, 2007). If stockpiling is planned, take a pasture sample to determine the protein levels in case supplemental protein in the ration needs to be increased.
This article is part of a series discussing organic dairy nutrition. For more information, see the following articles.
This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.