Performance, hepatic function and efficiency of nutrient utilisation of grazing dairy cows supplemented with alkaline-treated Jatropha curcas L. meal

Abstract

Jatropha meal is an emergent source of protein for ruminant feed, but the presence mainly of phorbol esters limits its use. We hypothesised that alkaline treatment of Jatropha curcas L. meal will reduce phorbol esters and allow its use as a concentrate supplement for dairy cows. We evaluated the effects of four levels of Jatropha meal treated with 70 g of sodium hydroxide/kg [JMT; 0.145 mg phorbol ester g/kg dry matter (DM)] in a concentrate supplement (0, 100, 200 and 300 g/kg DM; 4 kg cow/day as fed) on performance and efficiency of nutrient utilisation in grazing dairy cows. The alkaline treatment reduced the phorbol esters content of the toxic Jatropha meal by 67.7%. The JMT level linearly reduced the supplement intake (P < 0.01), but it did not affect pasture intake (P = 0.73) or blood hepatic transaminase (P > 0.10). As a result, the JMT level linearly reduced apparent total-tract nutrient digestibility (P ≤ 0.05), ruminal microbial protein synthesis (P = 0.05) and milk yield (P < 0.01). However, it did not affect milk composition (P > 0.05) and nitrogen balance (P = 0.29). Alkaline treatment substantially reduces the phorbol ester in Jatropha meal by 67.7%, but its inclusion in supplements reduces diet digestibility and performance of dairy cows.