Pashu Sandesh, 03 November 2020
Dr A.K. Patil and Dr Naresh Kurechiya
Protein, an important constituent in the ration of cattle and buffalo, when fed to ruminants is degraded by rumen microbes into ammonia, amino acid and peptides. Subsequently, these degradable products are utilised by the microbes for microbial protein synthesis, but that process may not be always efficient. Moreover, the excess ammonia produced from the degradation of highly degradable cakes, after absorption from the rumen wall is transported to the liver, converted to urea and excreted out through urine. It is a mere waste of dietary proteins, plus taxing the animal’s energy which is spent on urea synthesis. Although microbial protein is a good quality protein, it may not be sufficient to meet the requirement of high milk yielding animals. So ruminants may also be given proteins which are capable of escaping ruminal degradation, called undegraded dietary protein (UDP) or bypass protein, which is degraded in the intestines and absorbed as amino acids. Thus, to meet the nutritional requirements of high yielding animals, feed technologies like rumen-protected proteins can be adopted as it has consistently shown not only increased milk yield but also improved growth and reproduction. Protected nutrient technology is one such approach, involving feed management through passive rumen manipulation, by which the dietary nutrients (fat and protein) are protected from hydrolysis, allowing these nutrients to bypass the rumen and get digested and then absorbed from the lower tract.
The protection of protein can be achieved by various methods. Few of them are the following:
1. Naturally Protected Proteins: The protein degradability data (in the rumen) obtained by several groups of workers on a large number of feedstuffs in India and other countries has revealed that only a few feeds are good sources of naturally occurring protected protein (having lower protein degradability), viz., maize gluten meal, cottonseed cake, fish meal, coconut cake and maize grain. Feeds like linseed cake, deoiled rice bran, soybean meal and Leucocaenea leaf meal are of medium protein degradability; while Mustard Cake (MC) and Groundnut Cake (GNC) are highly degradable cakes. Negi et al. (1989) found that 50 to 70% of total N in tree forages may be present as protected protein. However, these forages contain 16-53% of total N in the form of acid detergent insoluble nitrogen. This is because of the presence of tannins, particularly the condensed tannins which bind the proteins irreversibly and if fed to animals, are capable of corroding the epithelial lining of the gastrointestinal tract. So, tree forages could be used as a source of protected protein only after devising a method for their tannin detoxification, using either some chemical, biological or biotechnological approach. While the proteins of lower protein degradability do not need any protection, highly degradable cakes like MC, GNC and sunflower seed cake need protection against the attack of ruminal proteolytic enzymes, for improving their utilization by ruminants.
2. Heat Treatment:
Heat treatment to feedstuffs has been found to increase protein protection (Senger and Mudgal, 1982). It works on the principle that heat treatment causes denaturation of proteins which provides effective protection against microbial attack. Heat treatment at higher temperatures reduces the availability of some amino acids like cysteine, arginine so to reduce such losses, steam treatment has been found fruitful. Steam treatment increases both bypassability and digestibility of proteins. Heat treatment at 125- 1500C for 2-4 hours could protect proteins very efficiently. High-pressure steam treatment with extrusion has shown promising results.
3. Formaldehyde Treatment: Proteins are chemically protected by treating with substances like tannins, formaldehyde, glutaraldehyde, glyoxal and hexamethylenetetramine. But formaldehyde treatment is most commonly used. Formaldehyde treatment has been found effective in improving the bypass protein (Walli et al., 1980) in oilseed meals, hay and silage. 0.5-1.5, 1-3 and 3-5% formaldehyde is used for protein protection in concentrates, hay and silage respectively. Formaldehyde treatment not only increases the rumen undegradable protein in feedstuffs but also increases its acceptability by animals.
4. Encapsulation of Proteins: Encapsulation of Proteins is usually done for good Biological value proteins and for inpidual amino acids. Methionine and lysine are limiting amino acids in microbial proteins on feed intake, plasma amino acids and milk production. So they can be given the form of the capsule with a combination of fats or fatty acids sometimes by addition of carbonate, kaolin, lecithin, glucose etc.
5. Amino Acids Analogs: Structural manipulation of amino acids to create resistance to ruminal degradation is another potential method for rumen bypass of amino acids. In addition to being absorbable from the small intestine, the analogue must have biological potency in metabolism by tissue. Analogues such as Methionine hydroxy, N-acetyl-DL-Methionine, DLHomocysteine thiolactone-Hcl, DL-Homocysteine, etc. have given satisfactory results. Reacting amino acids to produce imides, produced materials which survival ruminal conditions, yielded free amino acids at abomasal pH, and increased amino acids concentration in the ruminants.
6. Feed Processing
The normal procedure in the manufacture of feed ingredients can influence the magnitude of protein degradation in the rumen. Certain grain processing can either increase or decrease rumen degradation of Proteins. Increased ruminal degradation may be the result of disruption of the protein matrix, whereas heat applied or generated during grain processing can decrease ruminal degradation of proteins.
7. Metal Amino Acid Complex
Metal complexes commonly available such as Zinc Methionine, Zinc Lysine, Copper Lysine, Manganese Methionine, Iron Methionine etc. their usefulness lies in the fact to assume that they must be stable in the rumen environment and abomasum and be delivered to the small intestine intact, secondly, there is some evidence that mineral chelates are considerably better absorbed than inorganic forms.
Beneficial Effects of Bypass Proteins
Dr A.K. Patil and Dr Naresh Kurechiya
Department of Animal nutrition
College of Veterinary Science and A.H., Mhow
Nanaji Deshmukh Veterinary Science University, Jabalpur (MP)