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TDN and feeding the cow herd

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Faster horses

Well-known member
Feb 11, 2005
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NE WY at the foot of the Big Horn mountains
-from Drovers.

(While I don't believe everything I read in Drover's Journal,
I found this article interesting enough to share it here.)
We recently held a series of drought management meetings to help producers affected by this yearʼs drought find ways to keep their cowherds together through the winter. I know this meeting may have introduced more questions into our minds than answers. We must remember there is no ʻone size fits allʼ feeding program for wintering beef cows. There are so many factors to consider in designing a winter feeding program it is impossible to make blanket recommendations. My goal when designing a feeding program is to do this on a least-cost basis and do so to the extent that the program fits the producerʼs goals, meets the nutritional requirements of the cowherd, and matches up well with the producers feeding management skills, facilities and equipment.

Matching the cowʼs nutritional requirements. A 1,200-pound dry pregnant beef cow in her third trimester requires 1.9 pounds of crude protein and 12.6 pounds of total digestible nutrients (TDN, a measure of energy) or 7.8% crude protein and 52.5% TDN, based on hay intake of 26 pounds per day. Once this cow calves, she requires 2.8 pounds of crude protein and 16.4 pounds of TDN. The increase in available capacity in her body cavity and the additional metabolic stress from milk production increases her hay intake to over 32 pounds of hay a day. Even with this large increase in hay consumption, the lactating cowʼs nutrient requirement increases to 10% crude protein and 60% TDN. The lactating cow requires 25% more feed, 14% more energy, and 30% more protein than the gestating cow. This yearʼs short hay supplies and high feed costs make it very expensive to feed a lactating cow through the fall and winter. The large increase in nutrient requirements for the lactating cow is the primary reason for maintaining a calving season that fits your forage resources or at least being able to split cows into feeding groups based on expected calving date. If you feed cows that are fall calving and spring calving in the same group this winter your choice is … Do I overfeed the dry pregnant cows or underfeed the cows with calves? Either case is expensive and wasteful.

Matching the producerʼs feed management skills. When hay and forage is limited feeding management becomes more complex. With limited availability of hay, we can no longer put out multiple days worth of hay for cows to sort through and self-fed convenience products may not be something that can be used successfully. When cows are offered hay free-choice waste becomes a huge issue! If you do not have enough hay to make it through the winter and additional hay costs over $50 per bale, can you afford to lose 30 to 50% of it through poor feeding management?

Some producers are savvy enough and have the equipment available to make total mixed diets that can be limit fed to their cows. The feeding levels depend on the cowʼs stage of production and the energy content of the feeds used but range from 50 to 90% of full feed. With high hay prices, this feeding system can save a producer 30 to 40% in feed costs compared to free-choice hay feeding and a by-product based supplement.

Other producers that donʼt have the necessary equipment or time to mix feed daily may be able to feed high levels (0.6 to 1% of cow body weight, or 7 to 12 pounds of feed per day to a 1200 pound cow) of a low-cost, lowenergy supplement that can be used to reduce hay needs, yet not make cows too fat. Self-feeding liquid feeds or blocks as the sole supplement with hay is not recommended in the majority of our situations this year. These feeds are usually very effective at supplying protein and minerals to cows but many of these products are designed with very low consumption targets and the amount of energy provide by the supplement is quite small. These types of supplements mode of action is to stimulate rumen microbes, increasing intake of low quality hay and forage. When hay and other roughage are in short supply and expensive, stimulating increased intake may not be in our best interest. Some of these feeds can be very easily used as a part of total mixed diets (providing protein, minerals and dust control) or as a component in a supplementation program.

Feeding programs should be tailored to fit your operation. Programs that fit one operation will not necessarily fit yours. It is always best to consult with a trained specialist when making changes from your normal winter feeding program that always worked in the past.

Paul Beck

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