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NUTRITION – for Jun. 13, 2011

For many of you, haying season is fast approaching. Stored forage in one form or another is the basis upon which Canadian cow-calf producers plan their winter feeding program. In most cases, hay is the method of choice, although for some silage, swath grazing annuals, corn grazing, stockpiled forages and bale grazing are becoming attractive alternatives.

As haying season approaches, it is appropriate to review how your forage program contributes to the health and productivity of your cow herd. We can summarize this contribution in two words — “quantity and quality.” A 1,300-pound cow will typically eat 1.8 to 2.2 per cent of her body weight depending on forage quality. This means that she will consume on average 26 pounds of dry matter. At 16 per cent moisture, she is eating about 31 pounds of hay a day. If you feed your cows for 150 days, then for every 100 cows you require 232 tons of hay. If we include wastage, then from a “quantity” perspective, we are looking at an average of 2.7 tons of hay per cow to get through the winter.

The actual quantity consumed will be a reflection of the nutrient requirements of the cow as well as forage quality. As I have written previously in this column, your cow’s nutrient requirements change with stage of pregnancy. The two most important periods are the last six to eight weeks prior to calving and the period from calving to pasture turnout. During this period, the cow’s requirements for energy and protein, as well as essential minerals and vitamins are at their highest. We know that meeting nutrient requirements during this period will influence the ability and time required for the cow to rebreed. For many producers, particularly those calving in the spring, the majority of the winter feeding period coincides with mid-gestation, a time period where the cow’s requirements are associated primarily with maintaining herself.

Planning a successful winter feeding program involves matching your forage supply to the changing nutrient needs of your cows. From a nutritional perspective, forage “quality” can be defined in terms of its energy and protein content. The two most important factors influencing the quality of your hay are percentage of grass versus legume in the mix and the state of maturity at cutting. A good-quality grass hay can reach 55 per cent TDN and 12 per cent crude protein. Such a hay can meet both the energy and protein needs of your cows throughout the winter. As the percentage of legume increases in your mix, hay quality increases with a good-quality alfalfa/grass hay averaging 59 per cent TDN and 15 per cent crude protein or better. However, these values mean little if we do not take into account stage of maturity at harvest. It is well established that both grasses and legumes decrease in feed value as they mature.

Research by Dr. Peiqiang Yu and co-workers at the University of Saskatchewan illustrates this principle. Alfalfa cut at the early-bud stage averaged 20.5 per cent crude protein while that from hay cut two weeks later at the early-bloom stage averaged 17.7 per cent crude protein. Neutral detergent fibre levels in contrast increased from 49.8 to 54.3 per cent. With Timothy hay, crude protein content declined from 12.8 per cent at the joint stage of growth to 9.7 per cent at the heading stage, again only in a matter of two weeks. Neutral and acid detergent fibre levels were 67 and 36.6 per cent at the early-cutting stage and 70.5 and 39 per cent at heading. Higher acid and neutral detergent fibre levels indicate hay with reduced digestibility and lower intake potential, respectively and as a result, poorer-quality forage. The Alberta Forage Manual states that in order to maximize the yield of total digestible nutrients per hectare, grasses should be harvested at or shortly after heading while legumes should be cut at budding to 10 per cent bloom.

Other factors that you can control to ensure high-quality hay include taking steps to minimize post-harvest losses from nutrient leaching (excessive exposure to rain) and leaf loss (hay is too dry) as well as concentrating on minimizing storage losses. The latter can result from hay that is baled with excessive moisture (greater than 20 to 25 per cent) which results in heating and mould growth or from exposed bales left out in the field.

Many producers experienced the frustration of putting up hay under less-than-ideal conditions in 2010. Rain and delayed harvest in some areas translated into one of the worst hay crops in many years. This resulted in higher feed costs and in some cases negative effects on the herd including lost condition on cows, abortions and weak calves not to mention the potential for delayed rebreeding this spring. Hopefully, this year the sun will shine and our biggest concern will be finding enough hours in the day to get the job done.

[email protected]

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JohnMcKinnon isabeefcattle nutritionistat theUniversityof Saskatchewan

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John McKinnon

John McKinnon is a Professor Emeritus at the University of Saskatchewan and a consulting nutritionist who can be reached at [email protected].

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