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Are we over-feeding roughage to weaned calves?

Mark Hill and David Jones Published on 07 October 2009
How is post-weaning growth in your calves? One challenge in raising calves is a slump in growth after weaning. There can be several causes for this.

One is the amount of roughage offered to the calf. Weaned calves have small rumens with limited ability to digest roughage. Sometimes hay or other roughage sources are over-fed or grain and other concentrates are limited too much in these recently weaned calves.

Weaned calves under 4 or 5 months of age do not gain excessive body condition score (BCS) when fed high-grain diets. Published research has shown that as little as 15 percent grass hay is excessive and slows ADG because of reductions in intake.

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Recommendations have been to use approximately 5 percent hay in diets; however, roughage type and level have not been thoroughly researched. Three recent trials at Akey Calves (8 to 16 weeks of age initially) were fed textured grower feeds based on 62 percent grain (corn and oats).

In Trial 1, test diets contained 0, 3, 6 and 9 percent chopped wheat straw (2 percent CP, 54 percent ADF, 81 percent NDF on DM basis). Calf ADG and intake declined as straw increased.

In Trial 2, test diets contained 0, 5, 10 and 15 percent chopped alfalfa hay (23 percent CP, 23 percent ADF, 33 percent NDF on DM basis). Calf ADG declined as alfalfa increased. Intake was not changed with level of alfalfa.

In Trial 3, test diets contained 0, 3, 6, and 9 percent chopped grass hay (12 percent CP, 36 percent ADF, 55 percent NDF on DM basis). Calf ADG and intake changed curvilinearly as grass hay increased. The maximum ADG and intake was with 3 percent grass hay.

See Figures 1 and 2* for details on ADG and intake relative to level of roughage ( percent of as-fed diet) in each trial.

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When ADG was plotted against percent ADF from roughage in the diet (as-fed basis), the response was curvilinear, with little to no change with the first increments of ADF added from the roughage and a near linear decline through the next level of ADF added from the roughage (Figure 3*).

This is likely a result of some marginal acidosis issues in calves fed no roughage. Calves fed no roughage had some incidence of minor bloating (high left sides from gas in the rumen, but never severe enough to warrant release with an esophageal tube), but no bloating was noted for calves fed roughage.

Also, in retrospect, less straw should have been added to diets in Trial 1. Note the first level of straw added (3 percent) was as much ADF as the second levels of alfalfa and grass hay. In these three trials, and in previous trials at Akey, calves under 4.5 months of age fed these high concentrate diets have not gained excessive BCS.

The average gain in BCS over these 56-day grower trials have been less than 0.5 BCS units starting with an average initial BCS of approximately 2.5 to 2.75 in the 8-week-old calves. No individual calf in these trials has had an ending BCS exceeding 3.5.

Additionally, hip width change has paralleled ADG. So calves gaining more bodyweight are also growing frame. Optimum levels of roughage Textured growers based on 62 percent grain (corn and oats) should be fed with approximately 1 percent ADF or approximately 1.5 percent NDF from roughage to calves between 8 and 16 weeks age.

This added amount of roughage corresponds to from approximately 1.5 percent straw (as little as 0.1 pound per head daily) to 5 percent alfalfa hay (as much as 0.5 pound per head daily).

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A word of caution is to not feed these low-roughage diets too long. Feeding a low-roughage diet to 6 or 8 months old will overcondition the heifer. PD

*References and figures omitted but are available upon request to

Mark Hill
Ruminant Nutritionist
Akey Nutrition

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