Embracing whole plant optimization of rice and wheat to meet the growing demand for food and feed

Abstract

Feed scarcity results in large yield gaps in livestock production in low- and middle-income countries (LMC). In India, for example, the feed deficit in terms of digestible crude protein and total digestible nutrients is estimated to be 50 and 60%, respectively. Feed supply scenarios in India suggest that on a dry matter basis, crop residues (i.e., straws, stover, and haulms, the byproducts from grain production) contribute about 70% to feed resources. Crop residues are therefore the single most important feed resource in India, a scenario that likely holds good for many LMCs. Crop residues and crop byproduct-based feeding systems have the advantage of low direct and indirect food competing feed resourcing, since no or few grains (i.e. food) are fed to livestock and no land or water had to be exclusively allocated to feed production. Considering the importance of crop residues as feed resources, it comes as no surprise that many attempts to upgrade crop residues post-harvest by physical, chemical and biological treatments have been made. However, comparatively little uptake of these technologies has been observed. The lack of adoption of post-harvest approaches to improvement of crop residues gave way to a new research paradigm of targeted improvement of crop residues by plant breeding and selection at source. It was in the mid-nineties that the International Livestock Research Institute (ILRI) and the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) started to explore concomitant improvement of grain and crop residue traits as a major cross-CGIAR collaborative project. Initially more attention was given to typical rain-fed crops such as sorghum, pearl millet, groundnut and cowpea than to crops such as rice and wheat which are usually grown in irrigated areas such as the Indo-Gangetic Plains, Eastern Gangetic Plains and Southern India. In 2016 rice and wheat straw production potentially available as fodder was about 113 and 78 million tons respectively in India, contributing about 67% of all cereal straws and about 37% of the total feed metabolizable energy from straws. Using three scenarios, a 10% increase in rice and wheat straw yield (scenario 1), a 10% increase in rice and wheat straw metabolizable energy content (scenario 2) and a combination of the two (scenario 3) the paper estimates that at all India level an increase in yield (scenario 1) would add around 23 million tons while increase in the quality of the straw (scenario 2) would add additional 138 × 109 MJ ME and a combination of yield and quality increase (scenario 3) would add around 23 million tons and additional 291 × 109 MJ ME. Translated in terms of milk and meat production excluding the maintenance requirements the additional energy in scenario 1 or 2 would be equal to 27.6 million tons of milk or 9.2 million tons of mutton and the corresponding figures in scenario three would be 58.2 and 19.4 million tons, respectively. Hence, the opportunity lies with whole plant optimization which needs to be worked out by the plant and animal scientist together for mitigating the shortage of feed resources in LMCs.