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Performance of Limit-fed Pregnant Beef Cows Fed Ammoniated Wheat Straw Based Diets

26 August 2014

Uni Kansas State

Feeding anhydrous ammoniated wheat straw can yield faster growing cattle, although producers should be wary of high prices, a Kansas State University researcher has concluded.

A study comparing bodyweight, average daily gain and body condition score in spring-calved beef cows evaluated the effects of feeding 1.5 per cent or 3 per cent anhydrous ammonia.

The findings could be useful in adapting to widespread drought conditions across the state, according to Kansas State beef specialist, Justin Waggoner. 

He writes that the prevalence of drought conditions across much of Kansas and the Great Plains in recent years has renewed interest in the use of anhydrous ammonia to improve the feeding value of low quality forages such as wheat straw.

An application of 3.0 per cent anhydrous ammonia (60 lbs/ton) on a dry matter basis has traditionally been recommended. However, a demonstration project conducted by the K-State Beef Extension team at 6 locations across the state in 2012, indicated that an anhydrous ammonia application rate of 1.5 per cent (30 lbs/ton; dry weight basis) resulted in a proportionally greater improvement in forage quality than the recommended 3.0 per cent application rate.

A cow feeding study, based on the results of that case study, was recently conducted at the Agricultural Research Center in Hays during the Fall of 2013. The objective of this study was to evaluate the inclusion of wheat straw treated with 1.5 per cent or 3.0 per cent anhydrous ammonia (dry basis) in diets containing wet distillers grain limit fed (1.9 per cent of bodyweight, dry matter basis) to spring-calving beef cows for 84 days on cow bodyweight, average daily gain and body condition score. Three treatment diets were fed: 1) 64.1 per cent wheat straw (CON); 2) 64.1 per cent wheat straw treated with 1.5 per cent (weight/weight) anhydrous ammonia (1.5A); 3) 64.1 per cent wheat straw treated with 3.0 per cent (weight/weight) anhydrous ammonia (3.0A). See Table 1 for nutrient composition.

The results of this study are summarized in Table 2. Cows fed diets containing wheat straw treated with anhydrous ammonia resulted in greater bodyweight gain, average daily gain and tended to result in better body condition scores at the conclusion of the feeding period.

Collectively, the results of this study indicate that the performance of pregnant beef cows may be improved by applying anhydrous ammonia to low quality forages, such as wheat straw, at a rate as low as 1.5 per cent (dry weight). Additionally, these improvements in cow performance were observed in diets containing wet distiller’s grain.

Treating wheat straw with 3.0 per cent anhydrous ammonia resulted in the greatest bodyweight gain and average daily gain. However, the observed improvement in these variables in response to the 1.5 per cent application rate suggests that application of 1.5 per cent anhydrous ammonia (dry weight) may be more economical when anhydrous ammonia prices are relatively high.

More information on this study and many others may be found in the 2014 Agriculture Research Center-Hays Roundup, Centennial Report of Progress which may be viewed online at

August 2014

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