Potential Feeding Challenges That May Arise from Dry Weather Conditions
Managing your feed supply can be a challenge any year, but can prove especially problematic during a dry season, such as the one experienced in many parts of Canada and the U.S. Midwest. Ontario's 2012 growing season has negatively impacted forage and corn crops, which are particularly important to dairy farmers.
First-cut haylage yields were reduced because of winterkill, weakened stands, frost damage, low rainfall in April and May, and damage from armyworm and alfalfa weevil. While some areas had yields close to normal, others had significantly reduced first cuts.
Second-cut regrowth was significantly reduced by June and July's dry weather (see map). There was also significant damage from potato leafhoppers to new alfalfa seedingsand regrowth. A high-degree of variability existed for second-cut yields as well, with some areas closer to normal but many areas with very little second-cut regrowth. Depending on rainfall, a third-cut yield may be closer to normal. However, harvesting during the critical fall period will likely increase winterkill risk on already stressed fields.
Here are some considerations you should take into account before harvesting your crops this fall:
Harvesting extra late-season forage
Many farmers seeded oats or other annual forages into wheat stubble during the summer to harvest as haylage or baylage. Harvesting additional corn silage is also a useful late-season option to increase forage supplies when inventory is low. The corn crop also has been affected by the dry weather, with some areas expected to have significantly reduced yields and losses. Some grain corn crops severely damaged by dry weather will be salvaged as much-needed silage.
Minimize harvest, storage and feeding losses
Your first priority to address a forage inventory shortfall should be to minimize harvest losses, dry matter losses during silage fermentation, and spoilage and feeding losses. Pay close attention to avoid common errors that contribute to feed waste, including not adjusting for moisture changes, mixing errors and over-mixing, which reduces particle size and diminishes physically-effective fibre size. Monitor feed sorting behaviour. Also, check for adequate particle size when ration fibre content is minimized.
Efficient silage fermentation reduces dry matter losses and preserves nutrients. Use silage inoculant for haylage, since there may be fewer naturally occurring bacteria present and sugar levels may be less than optimal for efficient and rapid fermentation to occur. Do not add urea because it can prolong fermentation. With the high value per tonne placed on silage this year, ensure adequate packing and proper covering and sealing using materials, such as using oxygen barrier films. As well, using inoculant and maintaining a smooth, tight bunk face during feeding will help minimize losses.
If you're facing a forage deficit, you should discuss the situation and available options with your nutritionist. Depending on the situation, you could address a minor shortfall by tweaking your animals' rations to ensure higher value ingredients are available for the milking herd, or changing feeding practices, such as minimizing feed refusals.
Large inventory shortages will need more aggressive action, such as lower forage diets, including more high-fibre byproducts, purchasing forage or feeding straw to stretch supplies. You may need to consider a minimum forage diet if your homegrown forage inventory levels are low. However, this is riskier than using normally formulated rations.
Forage analysis and ration formulation
Forage and corn silage laboratory testing will be very important this year because of crop variability and the need for accurate information to implement revised ration strategies, ingredients and re-formulations. Use wet chemistry for corn silage analysis and include analyses for neutral detergent fiber(NDF) digestibility and starch content.
Ration fibre requirements are typically formulated at minimum levels rather than at an absolute amount. Fibre recommendations are designed to support normal butterfat test, proper rumen fermentation and pH to avoid acidosis and other digestive problems. Fibre recommendations are adjusted depending on the situation, including assessing other diet ingredients and the total ration content of non-fibre carbohydrate and starch level and source, like high-moisture corn versus dry corn grain.
Using corn damaged by dry weather for silage
Dry-weather-stressed corn that gets rain before harvest may contain elevated nitrate levels. High nitrates can be toxic to ruminants. A nitrate analysis should be done before feeding. The ensiling process reduces nitrates by 25 to 40 per cent. Silage fermentation should be complete before nitrate testing is done. Dry-weather-stressed corn silage can contain 60 to 80 per cent of typical corn silage nutrient value, but this varies and depends on the timing and severity of stress the plant experiences. Corn silage energy content estimates using ADF-NDF regressions will not be very accurate, so use estimates that include fibre digestibility and starch. Also, use wet chemistry methods instead of near-infrared spectroscopy.
Test for mycotoxins
It is also a good idea to test for mycotoxins this fall. While we often associate mycotoxins from moulds with wet weather, a plant's natural ability to resist mould growth is reduced when the plant is stressed. Conditions normally not conducive to mould growth may also be a factor this year.
Stretch forage supplies
The second priority after minimizing forage losses should be to identify ingredients you can use to stretch your ration's forage and fibre levels. Straw, for example, can be extremely effective in replacing fibre from hay or haylage, but in practical situations should be limited to one to two kilograms per cow per day. This will help avoid the corresponding reduction in the diet's energy content due to straw's relatively low nutrient levels.
In Ontario, several low-starch, high-fibre byproduct feed ingredients are available, such as brewers grains, soybean hulls, beet pulp, gluten feed and distillers grains. These byproducts are excellent NDF sources but only partially replace a physically-effective fibre source such as forage or straw. The nutrient profiles of these byproduct feed ingredients can complement or replace other ration components, and help you stretch your feed inventories in a cost-effective manner.
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