Improved Paddy Straw as Ruminant Feed: A Review

Paddy straw is a major agro-residue fed to ruminants in India. Feeding only rice straw does not provide enough nutrients to the ruminants even for maintenance due to the low nutritive value of this highly lignified material containing high concentration of anti-nutrition factors like lignin, silicates and oxalates. Despite the improvements of crop residues through various processing methods such as physical and chemical, the efficient utilization to desirable extent is still awaited. So utilization of paddy straw in association with concept of complete feed along with biological agents is need of the hour to maximize advantage from given feeds in animal production systems. Table 1: Rice production and byproducts of top 10 rice producing countries in the world in 2013 Calculated data (Adapted from NARC newsletter, 2013). Country Rice Production (Million t) Rice Husk (Million t) Rice Straw (Million t) China 166 38.18 74.7India 133.51 30.71 60.08Indonesia 51.85 11.93 23.33Bangladesh 38.06 8.75 17.13Vietnam 34.61 7.96 15.57Thailand 27 6.21 12.15Myanmar 21.9 5.04 9.86Philippines 13.17 3.03 5.93Brazil 10.22 2.35 4.6Japan 9.86 2.27 4.44 How to cite this article: Sheikh GG, Ganai AM, Reshi PA, Sheikh Bilal, Shabir Mir. Improved Paddy Straw as Ruminant Feed: A Review. JOJ scin. 2018; 1(1): 555555. DOI: 10.19080/JOJS.2018.01.555555 0011 Chemical composition of paddy straw and constraints in feeding to ruminants The chemical composition of paddy straw varies between varieties and growing seasons, with higher nitrogen and cellulose contents in early season rice compared to others [5]. Paddy straw contains 25-45% cellulose, 25-30% hemicellulose and 10-15% lignin with low nitrogen, vitamins, minerals and high quantities of silica which hinder the nutrient availability to rumen microbes and eventually limits the necessary nutrient uptake for a satisfactory performance of the animals [6,7]. Presence of anti-nutritional factors like silicates and oxalates in rice straw with low nutritive value, poor palatability and limited ruminal degradation render paddy straw as non-maintenance type of fodder, so cannot support nutrient requirement of the animals when fed alone [6,8].Table 2: Chemical composition of rice straw. Particular (%) Range Chemical composition DM 88.00-96.87OM 83.00-90.00CP 2.00-6.50CF 30.00-40.00ADF 49.00-73.01NDF 39.83-85.00NFE 40.00-46.00Hemi-cellulose 13.00-32.24Cellulose 31.96-60.00Ash 11.00-16.00AIA 3.00-5.00ADL 4.63-13.00Si 4.25-13.00Major minerals Ca 0.52-2.24P 0.13-0.39K 0.95-2.21Mg 0.91-2.35Na 0.06-0.09Minor minerals Fe 0.04-0.45Mn 0.07-Cu 0.005Zn 0.02Compiled from Prasad et al. [39], Singh & Oosting [52], Shen et al. [49], Van Soest [59], Wanapat et al. [62], Ganai & Teli [19], Akinfemi & Ogunwole [4], Hossain et al. [22], Gomma et al. [21], Hussein et al. [23], Sheikh et al. [48]. 0012 How to cite this article: Sheikh GG, Ganai AM, Reshi PA, Sheikh Bilal, Shabir Mir. Improved Paddy Straw as Ruminant Feed: A Review. JOJ scin. 2018; 1(1): 555555. DOI: 10.19080/JOJS.2018.01.555555 The chemical and mineral compositions of rice straw, cited by different workers, are illustrated in Table 2. Rice straw consists predominantly of cell walls, comprised of cellulose, hemi cellulose, and lignin. To break down these components cellulase, hemi cellulase and ligninase are required [9]. In ruminants cellulase and hemicellulase are produced by rumen microorganisms however, lignin cannot be broken down in the rumen due to the lack of ligninase. Lignin, however, has important effects on livestock production through effects on degradability and feed intake. Theoretically, lignin located between the cellulose micro fibrils is regarded as the most abundant natural aromatic organic polymer that plays a role in resisting compressing forces, providing protection against consumption by insects and mammals, and also inhibiting the rate and degree of microbial degradation [10]. Silica, one element of the rice cell walls, can be present in high concentrations ranging from 5% to 15%, depending on the rice variety [11] and the availability of this mineral in the soil [12]. Silica reduces palatability and the degradability of rice straw in the rumen due to its direct action in preventing colonization by ruminal microorganisms [12,13]. The role of silica on the quality of rice straw was also reviewed by Van Soest [8], in an attempt to put into perspective the problems of silicon metabolism. Besides cell wall polymers, rumen organisms need other nutrients for growth and metabolism.Since rice straw does not contain enough sugars, amino acids and minerals for efficient microbial growth, feeding ruminants with only rice straw, without any supplementation of other required nutrient sources, will result in poor performance of the animals [14]. The combination of low intake, low degradability, low nitrogen content and an unbalanced mineral composition means that rice straw alone may not even meet the animal’s maintenance needs. Poor degradability is caused by a series of factors [9]. The fiber is very difficult to degrade, which is partly an intrinsic characteristic of the straw fiber (higher lignin and silca content). The degradation of the straw fiber is also complicated by the poor functioning of the rumen due to the unbalanced availability of nutrients, the low protein content, the lack of easily available energy and the low content of essential minerals such as phosphorus and sulphur. Hence, due to the low degradability and the poor rate of degradation, animals will tend to consume less. The generally accepted theory of feed intake regulation for poor quality roughages is that the capacity of the rumen to process the feed is the major factor determining voluntary feed intake [15,16]. The rumen processing capacity is characterized by rumen fill, the rate of degradation of potentially degradable matter and the rate of passage out of the rumen. Devendra [2] summarized that the main determinants of intake and degradability of rice straw depend on their morphological characteristics, such as the proportion of the different plant parts (leaves and stems), their chemical composition and the distribution of the different chemical components in the tissues, their relative amounts of cell contents and cell walls and the physical and chemical nature of the cell walls. These factors influence the chewing behavior of animals and the extent of fragmentation in the reticulo-rumen. As per Theander & Aman [17], rice straw contains a relatively high proportion of leaf (60%), compared to other cereal straws such as barley (35%), oats (43%) and wheat (20-41%). Vadiveloo [18] reported that leaves of rice straw contain less NDF than the stems, but more ash and acid-insoluble ash, resulting in a lower in vitro dry matter digestibility (IVDMD) of the leaves (50-51%) compared to the stems (61%). In goats, Phang & Vadiveloo [19] observed an in vivo dry matter digestibility of 56.2% for rice leaf and 68.5% for the stem. However, treatment with a 4% urea solution for 21d increased the IVDMD of the leaf fraction more than that of the stem fraction [18]. Since rice straw consists of approximately 60% leaves [20], which are less degradable than stems, improving the feed value of rice straw should focus on improving the degradability of the leaves.Possible strategies to improve rice straw utilization in ruminants Feeding only rice straw does not provide enough nutrients to the ruminants even for maintenance due to the low nutritive value of this highly lignified material. Basically, the key to improving the use of crop residues for ruminants is to overcome their inherent barriers to rumen microbial fermentation. In the case of rice straw, the important factors that restrict