Effect of synthetic and organic insecticide on chemical composition and in-vitro gas production of cowpea haulms

Abstract

Farmers often use insecticides to manage pests on cowpea farms, raising concerns about their longterm residual effect on the chemical composition and digestibility of crop residues used as ruminant feed and on human health. This study examined the effect of synthetic and organic insecticides on the chemical composition and in vitro gas production of cowpea haulms. Field trials across two cropping seasons and laboratory analyses were used to assess the effect of insecticide application on cowpea haulms. Insecticide application significantly influenced the chemical composition of cowpea haulms (p > 0.05). Both synthetic and organic insecticide-treated haulms had significantly higher crude protein contents than the control group (p > 0.05). All treatment groups exhibited high levels of crude protein (CP) (157.2–213.4 g/kgDM), crude fat (78.8–103.7 g/kgDM), and ash (118.5–128.1 g/kgDM). The neem extract treatment had the highest CP content (213.4 g/kgDM), while the control group had the lowest (14.46%). Moderate in vitro digestible organic matter (IVDOM) (43.39 - 45.71%) and metabolizable energy (ME) values (6.09 - 6.68 MJ g/kg) were also observed. The microbial population was significantly decreased in the neem oil extract and Dursban treatment groups compared to that in the control group (p<0.05). Cowpea haulms can serve as supplementary feed to improve the utilisation of poor-quality feed resources during the dry season, thereby enhancing ruminant growth performance. However, the persistence of pesticides in plant matter post-harvest hinders microbial digestion and fermentation in the rumen when animals consume plant residue.