Evaluation of the Nutritional Value of Ammoniated Wheat Straw by Anhydrous Ammonia in Fattening Calves Feeding

Processing of agricultural by-products for animal feed can upgrade the supply of animal feed without increasing the current production and only by improving productivity via enhancing energy efficiency and maintaining it in the food supply chain, and at the same time, diminish the concerns of waste management, food security, resource constraints, and environmental protection. As a result, human and livestock competition for food make less and feed prices cut.

This experiment was performed to determine the optimal method of ammoniation of wheat straw with anhydrous ammonia (ammonia gas) including the effect of increasing the amount of moisture and the amount of gas used for ammoniation and investigating the effects of replacing ammoniated straw with straw in the diet of fattening calves in two stages. In the first stage, ammoniation of the wheat straw using four levels of moisture (0, 20, 25, and 30%) and four levels of ammonia gas (0, 2, 2.5, and 3%) was performed in a factorial experiment and the chemical composition and digestibility of the samples were determined and compared. In the second stage, in order to investigate the effects of using ammoniated straw in the diet of fattening calves, 24 Simmental fattening calves with an initial weight of 356 ± 15 were divided into control and experimental groups. In the experimental group, NH3-treated straw which was processed using 3% ammonia gas whith 30% moisture in straw, replaced untreated straw in the control group. Dry matter consumption and daily weight gain, feed conversion ratio, and weight gain cost of calves were studied for five months and compared between the two groups.

Ammoniation of straw did not cause significant changes in the amount of organic matter and ash. The percentage of straw crude protein as a result of ammoniation increased up to 2.7 times and with increasing ammonia level and moisture content, the amount of crude protein showed a tendency to increase. Ammoniation caused a significant difference in the amount of NDF, ADF, hemicellulose, and ADL in straw, and the digestibility of dry matter and organic matter was also improved. Daily dry matter intake increased in the experimental group (p<0.01) and the daily weight gain and mean weight at the end of the experiment period were significantly higher in the experimental group (p<0.01). The feed conversion ratio showed a significant improvement in the experimental group (p<0.01) and the use of ammoniated straw treated with 3% ammonia gas and 30% moisture reduced the ration price and feed cost per kilogram of livestock weight gain.

Treating wheat straw with anhydrous ammonia (ammonia gas) is a simple, fast, and effective way to process straw and increase its nutritional value and digestibility for livestock, and its economic efficiency depends on the availability and price of gas and the method used.