Chemical and biological evaluation of feed stuff

Pashu Sandesh, 01 June 2021

• Vishal Singh ^{*, 1}    • Monika Karnani ¹    • Danveer Singh ¹    • Jitendra Kumar Sharma¹    

¹Department of Animal Nutrition, PGIVER, Jaipur, Rajasthan, INDIA 302031

*Vishalgurjar6157@gmail.com

Introduction:

Feed evaluation involves all the process in which the quality of feed increase by different methods like soaking chopping and chemical and biological treatment.  Feed evaluation is aimed at giving information on the capacity of inpi-dual feeds to meet the nutritional requirement of the animal.  Monogastric animals have less complex feed compositions which do not require extensive feed evaluations as it is in ruminants. Feed evaluation is necessary because it increases the feed digestibility, palatability and breaks the lignocellulose bond of feedstuff. It plays an important role during scarcity to increase the digestibility of poor quality feedstuff.

Types of methods:

1. Physical methods

2. Chemical methods

3. Physiochemical methods 

4. Biological methods

Chemical method of feed evaluation:

The chemical treatment of feed increases the lignin solubility and decrease the bond between the lignin and cell wall constituents. Thereby making cellulose and hemicellulose more susceptible to microbial attack. There are different type of chemical which are used in chemical treatment like KOH, NaOH, and sodium carbonate. There are some following methods that are used in feed evaluation.

1. Use of sodium hydroxide: In this method, low-quality roughage or straw is treated with NaOH under high pressure and temperature. A product is known as fodder cellulose. This process is very expensive and only used in emergency situations.

It has two major types: A. Wet method B. Dry method

A. Wet method or Beckman’s method: it consists of treating chopped straw in 8-10 times its weight of 1.2 to 1.5 %( W/V) solution of NaOH for at least 4 hours. The treated straw was drained and washed with a large quantity of water until free from alkali. It should be neutral to litmus paper. As NaOH is caustic and rapidly attack tissue, it should be washed properly. 

B. Modified Beckmann method: The most immediate problem with the Beckmann method was that of river pollution. If wash water could not be discharged, it would have to be recycled. Torgrimsby (1971) suggested a closed system in which the amount of water added to the system is equal to the amount removed in the treated straw. It uses less NaOH and less water. In this method, dry method loss is reduced. There is no pollution problem because it is a closed system. 

C. Dry method: The development of dry chemical methods of straw treatment was also approached from point of view of improving upon the Beckmann method. The improvement was that the treated straw is not washed. Consequently only as much NaOH can be used as will not unduly disturb the animal system. This level of NaOH has been found to be about 5 kg/100 kg straw. In another word 4-6 kg of NaOH dissolve in 200lit. of water is adequate to wet 100kg straw. The treated straw is moist and has a pleasant odour. Intake of straw is increased by 30-40%. Thus, while, the problems of dry-matter loss and river pollution are solved by the dry method, the benefit from the use of a high alkali: straw ratio (i.e., a large increase in digestibility) had to be foregone. By applying heat and pressure some of this loss in the degree of improvement in digestibility can be recovered, moreover, sodium pollution is not eliminated but only occurs in a more diffuse form when the straw is treated by the dry method. On the other hand, a very great advantage of the dry method is that it can be industrialized. The subject of the health of livestock fed on dry-treated straw has been discussed by Jackson (1977). In general, animals suffer no stress if the diet contains less than 4% of NaOH on a dry matter basis. This corresponds to 2.5% sodium in the diet.

2. Treatment with calcium hydroxide: Nutrient analysis of  Calcium Hydroxide treatment of feedstuff will show a reduced neutral detergent fibre (NDF) levels, increased calcium, increased crude protein and a slightly improved in vitro digestibility of these feedstuffs due to the strong base degrading the plant fibre. Ensiling calcium hydroxide treated straw 4 kg calcium hydroxide per 100kg straw with enough water to give 50% moisture in freshly treated straw for 90 to 150 days has resulted in higher fermentability of treated straw. Treatment with 4% NaOH produced significantly greater gains than 4% calcium hydroxide. Treatment of straw with calcium hydroxide will be effective when treated straw doesn’t have more than 70% of the diet because the calcium content increases more than the normal requirement (1.5 to 2.0%). Treatment with a combination of calcium and sodium hydroxide produces a better result than a single treatment. 

3. Treatment with anhydrous ammonia:  stack method is used in this treatment. Stacks of straw were wrapped with polyethene cover and injected with 3% of anhydrous ammonia. This method has become popular under Indian condition. When the material with a high sugar content (5% as hay) is treated with anhydrous ammonia at high temperature (70°C) a poisonous compound ‘4-methyl imidazole’ can be formed which may cause hyperexcitability (crazy cow or angry cow) in farm animals. When straw treated at environmental temperature the risk of this disturbance should be negligible.

4. Treatment with aqueous ammonia: aqueous ammonia (20-35%) is also used commercially for the treatment of straw. The advantage of this method is that at an ammonia concentration of about 20% the solution can be transported and handled at normal temperature and pressure. 

5. Treatment with urea: Urea treatment of straw leads to an increase in intake (20-25%), digestibility (10-15%) and energy availability to the host animal which otherwise would have been wasted. Urea treatment also enriches the straw for its protein content (up to 9-10%).

Steps of urea treatment:

1. Take 100 kg of straw or stovers and put them on the cemented floor.

2. Take the fertilizer grade urea at 4kg.

3. Dissolve the urea (4kg) in 20-30 lit. Of water and mix it till it completely dissolves. 

4. Spray the urea solution with any sprayer on the straw lot. 

5. Mix urea solution and straw thoroughly with hand fork (about 5-6 turning).

6. Stack under the plastic sheet/gunny bags covers to have the anaerobic condition and allow it to react for about 3 weeks.

7. Take the straw out from the stack. Give 2-3 turning so that excess ammonia gets evaporated in the atmosphere. 

8. The colour of the straw is changed from yellowish to dark brown during the reaction time. Treated straw is ready to use as animal feed for livestock.

Advantages of urea treatment:

• The ingredients are readily available in the market.
• It is not hazardous during the process/treatment of roughage.
• The urea gets converted into ammonia and then ammonia reacts with fibre to complete the reaction. Being a source of alkali it helps in breaking the lignocellulosic bonds and thereby increases the digestibility of the energy-producing components.
• It increases the protein content by two to three times.
• The urea treatment of straw does not cause any pollution problems.
• The urea treated straw does not create urea toxicity in the animal.

Biological treatment of feedstuff: 

The biological treatments are paralleled with decreased crude fibre and fibre fractions content with increased crude protein content. Direct-fed microbial and exogenous enzymes to the animal are other ways of biological methods for improving the nutritive value of feeds. There is some biological method of feed improvement: 

1. Enzyme treatment: how to use enzyme in feed; There are two ways of using enzymes to improve the efficiency of animal feed. First, you can use them to reformulate the feed, reducing costs. By using higher fibre by-products than is possible without enzymes, you can replace some of the wheat, corn, or barley in the animal’s diet and reduce the fat level. Secondly, one can add enzymes directly to feed and produce more meat or eggs, thus significantly saving poultry manufacturing cost. The key benefits of enzymes improve feed efficiency and reduce the cost of production of meat and eggs. Enzymes improve the consistency of feed that helps in the maintenance of gut health and the digestion process results in overcoming the growth of disease-causing bacteria.

The efficiency of additional microbial phytase in improving the utilization of phosphate from phytate is very good to enhance animal nutrition (Simons et al., 1990; Adeola et al., 2006; Augspurger et al., 2006; Garcia et al., 2005). Excretion of phosphate can be decreased by as much as 50%, which is from an environmental viewpoint. Beta Glucanase digests fibre and helps in better digestion of heavy cereal grains such as wheat, barley and rye in the diet. Because Beta glucanase hydrolyses the glucans present in these ingredients thus reducing the viscosity of digesta, and helps to revitalize natural peristalsis, enhances the digestive process, increasing the overall nutritional value of the diet. Cellulase solution is sprayed on straw at 25mg\100kg straw. Proteases are the enzymes that degrade proteins; Amylase is a group of enzymes that catalyse the breakdown of starch and sugar. Amylase breaks polysaccharides (carbohydrates) into smaller disaccharides, finally converting them into monosaccharides such as glucose, fructose, galactose etc. down the bonds at certain sites of amino acids.

2. Fermentation: chopped straw is pre-treated with 3-5% NaOH and steamed at 120°C for 15 min. then fermented with bran type media cultured with cellulolytic microorganism at 40-50°C for 2 days.

3. by use of fungi: Common fungi utilized in feeding programs include Saccharomyces cerevisiae, Aspergillus oryzae, Pleurotus spp., Antrodia cinnamomea, and Cordyceps militaris. These fungi are rich in glucans, polysaccharides, polyphenols, triterpenes, ergosterol, adenosine, and lactases.  As such, fungal feed additives could be of potential use when breeding livestock. Some of the white-rot fungi degrade lignin to the extent of 65-75% while other fungi degrade over 45% of lignin in the lignocellulosic materials. Preference is given to species that degrade only lignin but not hemicelluloses.

Conclusion:

Chemical and biological treatment of feed enhances its digestibility and nutritive value. It is very important during scarcity period .it also increase the production of animal and maintain animal health.