INTAKE AND DIGESTIBILITY OF LOW QUALITY RHODES GRASS HAY AND GROWTH OF SHEEP AS AFFECTED BY BROWSE SUPPLEMENT AND MAGADI TREATMENT

Abstract

An experiment was conducted at Bunda College, Malawi, to determine the effect of magadi (a sodium sesquicarbonate- Na2CO3, NaHCO3.2H2O) treated forages on their intake and digestibility and growth of sheep. Rhodes grass (Chloris gayana Kunth), Cedrela (Toona ciliata, M. Roem) and Sesbania [Sesbania sesban (L) Merr]. Samples were each treated with 0% (control), 5% or 10% magadi suspension. In this text Rhodes grass, sesbania and cedrela shall be abbreviated as R, S and C, respectively. Polyethylene glycol (PEG) a tannin complexing agent, was mixed with a sample of C and S to compare its effect on gas production with samples treated or not treated with magadi. Thus, the treatments were R0, R5, R10, S0, S5, S10, C0, C5, C10, SPEG and TPEG. The 11 treatments (each 500mg forage in 100ml syringes) were incubated in cattle rumen liquor at 390C for 96 hours. The 10% magadi treatment lowered gas production compared to the control. However, the C5 treatment produced more gas (93.5ml) than the TPEG (76.7ml), while the S5 treatment produced slightly less gas (104.9ml) than the SPEG (108.6ml). It was concluded that magadi suppresses the antinutritional components of forage thereby facilitating degradation of the feed, but the 10% magadi level lowers the rumen degradation. In the intake and digestibility trials, 100g of ground S0, S5, S10, C0, C5 and C10 treatments were each mixed with 100g maize bran in 1:1 ratio daily. The R0, R5 and R10 hays were basal feeds, and were fed to correspond with the magadi levels of the respective treatments (e.g., R5 fed with S5 or C5). The results indicated that dry matter and organic matter intake as well as urine production increased significantly (p< 0.05) with increased magadi level and sesbania supplementation However, the magadi treatment depressed the digestibility of crude protein. The growth trial lasted for 60 days, and the expected growth rate was 150g per day. The Rhodes grass hay was not treated with magadi. Seventy percent Maize bran and 30 % treated forage (S0, S5, S10, C0, C5 and C10) were mixed and four intact male sheep of average weight of 40.8 ± 7.2Kg were assigned to each ration. The expected growth rate was not achieved at the end of the trial. The difference between the treatments within the two browses and among the three levels of magadi treatment were not significant. However, sesbania supplementation and magadi treatment tended to increase growth rate of the sheep.


(UNISWA J Agric: 2000 9: 22-33)