The utilization of teff (Eragrostis tef) straw by sheep fed supplementary forage legumes with or without either crushed maize grain or wheat bran
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Small Ruminant Research;29(3): 303-315
Permanent link to this item: http://hdl.handle.net/10568/29619
This study examined the interaction of high energy substrates (ES: crushed maize grain (MG) and wheat bran (WB) with forage legumes (FLs), such as Lablab purpureus hay, sun dried leaves of Sesbania sesban and tagasaste (Chamaecytisus palmensis), on ruminal microbial activity (indexed by the degradability and digestibility of teff (Eragrotis tef) straw (TS), urinary excretion of purine derivatives (PD)) and on nitrogen retention. The diets comprised TS fed alone ad libitum (TSA) or TSA supplemented with either of the above FLs (175 g/day) with or without 47 g/day of either MG or WB. The 10 diets were fed to 20 ruminally cannulated sheep in two periods during which each of the degradabilities of TS and of the FL corresponding to that which the sheep were consuming were determined in sacco. The particulate rate of passage was also determined using chromium mordanted TS. Forty castrated male Ethiopian Menz sheep were used in a randomised complete block design to determine the effects of the above diets on intake, digestibility, urinary PD, microbial N synthesis and N retention. Both the potential and the effective degradabilities indicated that sesbania was the most degradable, and lablab the least. Supplementation with Fs alone increased the rate of degradation of TS by 50 to 142 percent, the rate of passage of particles (kp), the intake of TS, dry matter (DM), organic matter (OM), nitrogen (N) and neutral detergent fibre (NDF); had no effect on the digestibility of DM, OM, teff and NDF; increased faecal N. urinary N, N retention, urinary allantoin, total and microbial PD, microbial N and the efficiency of microbial N synthesis. Forages were similar in the degradation rate of TS but differed in the intake of TS, DM and OM in the order: sesbania > tagasaste > lablab. Lablab diets sustained higher kp than either the sesbania or tagasaste diets. Sesbania diets, compared to lablab or tagasaste diets, depressed the digestibilities of DM, OM, NDF, ADV and TS; increased faecal, urinary and retained N, urinary allantoin, total and microbial PD, microbial N and efficiency of microbial N synthesis. Further supplementation with high ES depressed kp, tended to depress (P>0.05) the degradation rate of TS by 14-45 percent, and that of FLs by 21-47 percent; increased faecal N, retained N, urinary allantoin, total and microbial PD, microbial N and the efficiency of microbial N synthesis; had no effect of digestibility and urinary N. Maize depressed the digestibility of ADF and urinary N. but increased urine allantoin relative to wheat bran while both energy substrates elicited similar N retention and microbial N synthesis. Supplementing straw diets with FLs is beneficial in terms of intake, microbial N synthesis and yield. These benefits correlate positively with the degradability of FLs and are further improved by a complementary high energy substrate.