**1. Introduction**

Wheat is not used traditionally as a feed grain because its milling properties make it desirable for use in breads, pastas and noodles; the milling of wheat produces flour for human use and appreciable quantities of by-products for animal feeds. However, recently, there have been significantly increased supplies of feed wheat used as livestock feed, in particularly in ruminant feeding. The livestock industry is interested in increasing wheat portion in animal

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

rations because of competitively priced wheat compared with other feed grains. Wheat is high in starch and protein, and low in fiber [1]. Similar to other cereal grains, feed wheat is primarily used a source of energy in the form of carbohydrates. Available energy expressed as either digestible energy or metabolizable energy per unit of dry matter is similar to corn, but higher than other major grains [2]. The majority of wheat has traditionally been used as feed for poultry and swine because the use of large quantities of feed wheat in ruminant rations has a number of concerns and problems. The primary problem appears that wheat starch is highly fermentable and its rate of digestion in the rumen is greater than that of corn and barley grains that increase the risk of rumen acidosis in animals fed high-grain diet [1, 3]. Furthermore, the physical characteristics and nutrient content of wheat can vary considerably due to different types of wheat: soft, hard and durum, and the growing conditions [4]. Therefore, nutrient contents of wheat, variety and growing conditions need to be considered when quality of feed wheat is assessed. In addition, kernel processing is another key factor affecting wheat quality. Whole wheat kernels are poorly digested due to the resistance of the seed coat to attack by rumen microbial or host enzymes. Therefore, wheat grains require processing to break seed coat. The digestibility of wheat can be increased from about 60% if fed whole to over 90% if properly processed. However, attention to processing is crucial for best results when feeding wheat since over processing can result in digestive upset and several factors (kernel hardness and uniformity, and processing methods) can significantly affect the processing results. Finally, level of deoxynivalenol in wheat grain may affect feed value. The deoxynivalenol, commonly referred to as vomitoxin, is a mycotoxin that may be produced in wheat and barley grain infected by Fusarium head blight or scab [5]. Ruminants are generally considered to have more tolerance to Fusarium toxins such as deoxynivalenol than poultry and swine because of the detoxifying potential of rumen microbes. However, little information is available on the effects of deoxynivalenol level in wheat on performance and health of ruminant animals. The levels of deoxynivalenol vary with type of wheat and the tolerance to deoxynivalenol also differs depending on type of animals (dairy versus beef cattle) or production levels [5]. The present review will be focusing on assessing physical and chemical characteristics of wheat, kernel processing and levels of deoxynivalenol related to feeding value for ruminant animals based on the published results.

the summer. Soft wheat varieties have starchy kernels and less gluten which mill easier than the hard wheats, whereas hard wheats have higher protein and gluten levels than the

Quality Assessment of Feed Wheat in Ruminant Diets http://dx.doi.org/10.5772/intechopen.75588 117

Test weight, also referred to as volume weight or bulk density, is one of the criteria used to assess the quality and grade of cereal grains. Test weight is a measure of density and it is measured volume of grain expressed as kilograms per hectoliter (kg/hL; **Table 1**). The test weight is easily measured and commonly used by feed mills to assess the quality (energy value) of grain as animal feed. Heavy kernel typically has larger plumper kernels with greater starch and lower fiber concentrations than light weight grain, but there is no consistent relationship between test weight of grain and animal growth performance [6]. The test weight is influenced by genetics, agronomic management and environment conditions. Each kernel is composed of the bran (seed coat), the germ, and the endosperm. The endosperm is primarily comprised of carbohydrates (starch) with protein woven among the starch granules. Starch weighs more than protein, thus the tighter the starch molecules are woven within a kernel, the greater the test weight. The test weight in itself is not a good indicator of feeding value to ruminants. Generally, cattle fed wheat with test weights greater than 70 kg/hL will have similar feed efficiency. However, usually only wheat with low test weight (<70 kg/hL) will be used as feed, and its energy values will be lower and feed efficiency is poorer. Wheat with low test weight may be more difficult to properly process compared to wheat with higher test weight. In general, kernel size is more variable with low test weight grains, making processing more difficult. When the roller is set properly for larger kernels, many small kernels will pass through the rollers unprocessed.

When set properly for smaller kernels, many larger kernels will be processed too finely.

**Item Mean STD Min Max** 1000 Kernel weight, g 36.4 2.9 32.7 39.1 Test weight, kg/hL 81.6 2.4 78.1 84.3 Kernel hardness 18.4 12.3 0 35.5

**Table 1.** Variation with variety of physical characteristics of wheat; kernel hardness was estimated by particle size index,

Kernel hardness, defined as the resistance of the kernel to fracture, is a critical factor affecting grain processing and product quality for feed wheat. The wheat industry has applied this trait for decades to differentiate grain quality and market classes. Hard wheat kernels require more force to fracture than do soft wheat grains, which is caused by differences in the endosperm starch-protein matrix [7]. Kernel hardness can be measured as a hardness index using a Single Kernel Characterization System [8], milling energy using a Comparamill [9] or by particle size analysis [10]. The particle size analysis is the measurement of particle size after feed processing, and is a commonly used method to evaluate end-use quality [11]. Soft wheat fractures easily with small particle size and limited starch damage, while hard wheat produces larger particles with increased starch damage. Kernel hardness is closely related to

soft wheat with the hardest wheat is durum.

**2.1. Physical characteristics**

lower number indicates harder kernel.
