Secondary metabolites as anti-nutritional factors in locally used halophytic forage/fodder

Abstract

Rampant salinity coupled with population explosion necessitates search for suitable alternatives to conventional sources of food both for human and animal consumption. While it may be difficult to change our culinary preferences, training animals to adopt a changed diet of nonconventional salt tolerant plants is easier. Using these wild plants however, requires estimation of undesirable secondary metabolites (SMs) produced during stressful conditions, which may be harmful for health of animals. Some of these anti-nutritional components (total phenols, flavonoids, tannins, nitrates, saponins and oxalates) were determined in 22 halophytes locally used as fodder/forage. Most of the species were perennial shrubs and herbs of an area where environmental conditions like high mean annual temperature (~35°C), low rainfall (< 250mm) with soil mostly dry (average 2% moisture) and saline (average EC 13 dSm-1) supported the growth of halophytes and xerophytes. Values of SMs in the studied plants ranged from 0.13-4.05% for total phenols, 0.38-6.99% for tannins, 0.151.50% for flavonoids, 0.10-1.15% for nitrates, 0.45-8.68% for saponins and 0.36-2.34% for oxalates. Most of the species (19) contained low to moderate amount of individual as well as total SMs which were within the non-toxic ranges. However, three species distributed in coastal habitats where average soil salinity (27.67 dSm-1) was considerably higher than inland ones (7.09 dSm-1) had SMs contents above the safe limits. It is evident from these results that most of these plants contained moderate to low levels of anti-nutritional factors, which lies under the safe limits and hence, could be used as a potential feed source to raise animals, particularly in arid/semiarid areas. Additionally, these plants represents a viable choice as they can be grown without encroaching on agricultural lands and fresh water resources and could promote livestock production which may improve socio-economic conditions of poor farmers in a sustainable and eco-friendly manner.