Nutrient value and <i>in vitro</i> gas production of African wild cocoyam (<i>Colocasia esculentrum</i>).

Abstract

Cost of feeding conventional feedstuffs to ruminants in Nigeria is prohibitive. African wild cocoyam (Colocasia esculentrum) is an unconventional energy feed source and non human edible food. The study determined the chemical composition and energy content, secondary metabolites and in vitro gas production characteristics of the
African wild cocoyam (AWC). There were two main treatments which comprised soaking in boiled water or cold water for 0 (raw as control) 3, 6 and 9 days. Dry matter (DM) of boiled water treated wild cocoyam (BWTAWC) and DM in cold water treated wild cocoyam (CWTAWC) decreased from 64 % to 43 % in 9 day BWTAWC and 64 % to 52 % in 9 day CWTAWC. Crude fibre, ether extract, neutral detergent fibre and gross energy contents decreased with increasing days of soaking and ranged from 11 – 21 % (BWTAWC) and 18 – 21 % (CWTAWC), 3.9 - 6.5 % (BWTAWC) and 5 - 6.5 % (CWTAWC), 32.5 - 56.1 % (BWTAWC) and 38 - 56.1 % (CWTAWC) and 3.66 - 4.29 % (BWTAWC) and 4.10 - 4.29 % (CWTAWC), respectively. Method of soaking and length of soaking marginally increased contents of crude protein (range = 4.7 - 5.8 %) and ash (range = 8 – 13 %). Secondary
metabolites present were saponin and steroids, with no tannin. Medium saponin
content was detected and it decreased by soaking method and duration of soaking.
There were significant (P < 0.05) differences in the metabolisable energy (ME)
(Range = 4.33 - 9.62 MJ/Kg DM and 4.33 - 8.59 MJ/Kg DM for CWTAWC and BWTAWC respectively), organic matter digestibility (OMD) (Range = 32.26 - 56.6 % and 32.26 - 43.55 % for CWTAWC and BWTAWC, respectively) and short chain fatty acids (Range 0.65 - 0.97 for both CWTAWC and BWTAWC) among the treatment means. Methane production increased with increasing days of soaking in water but were not significantly (P > 0.05) different. Results showed that with high energy value, medium saponin, enhanced organic matter digestibility and relatively low methane production, African wild cocoyam has potential to be used as energy feed for ruminants. Treatment by soaking in water reduced the secondary metabolites and, therefore, safe for livestock feeding.

Keywords:Cocoyam, nutrients, metabolites, gas production.

AJFAND Vol. 9 (1) 2009: pp. 594-607