Fifteen potential precursors of propionate were tested for their ability to decrease CH 4 production by ruminal fluid in vitro. Sodium acrylate and sodium fumarate produced the most consistent effects in batch cultures, with 50 % of the added precursors being fermented to propionate and CH 4 production decreasing by between 8 and 17 %, respectively. Additives were more effective when added as free acids, but this also decreased the pH and may have inhibited fibre digestion. Changing the dietary substrate from predominantly grass hay to predominantly concentrate had no influence on the effectiveness of acrylate and fumarate. In an in vitro fermentor (the rumen simulating technique, Rusitec) with a grass hay-concentrate (50:50, w/w) diet as substrate, both compounds were again fermented to propionate (33 and 44 % conversion to propionate, respectively). However, fumarate appeared more effective as a H 2 sink compound. It was calculated to capture 44 % of the H 2 previously used for CH 4 formation compared with a 22 % capture of H 2 with acrylate. Fumarate also caused a stimulation in fibre digestion. Thus, sodium fumarate was the preferred propionate precursor for use as a feed ingredient to decrease CH 4 emissions from ruminants.

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In vitro studies were conducted on five sorghum genotypes developed for the dry tropical highland climate of Kenya and which can be fed to ruminants fresh or as silage. The five sorghum genotypes consisted of two normal white mid-rib (WMR) genotypes, coded E1291 and E6518l, and three brown-midrib (BMR) genotypes, coded Lan-5, Lan-6 and Lan-12. Whole mature plants (herbage plus grain) and silage made from E1291 were used in the study. An in vitro manual gas production technique was used to compare the nutritive characteristics of these genotypes for ruminants. These sorghums differed significantly in true organic matter degraded (OMDeg), which ranged from 520 to 678 g/kg after 24 h incubation and 706 to 805 g/kg after 72 h incubation. All the BMR sorghums had a higher degradability than the WMR genotype, E6518, and the silage, with Lan-5 having the highest degradability. Methane produced per g OMDeg ranged from 40.6 to 46.4 mL/g after 24 h incubation and from 53.1 to 62.6 mL/g after 72 h incubation. It was similar for all genotypes after 24 h incubation but Lan-12 had the highest methane production after 72 h incubation. After 24 h and 72 h incubation all the genotypes produced a similar total amount of gas per OMDeg (293 to 309 and 357 to 385 mL/g, respectively) with similar total short chain fatty acid concentrations in the liquid digesta (7.8 to 10.4 and 9.5 to 10.3 mmol, respectively) and acetate to propionate ratios of 2.16 to 2.49 and 2.35 to 2.87, respectively. The sorghums showed great potential as ruminant feed sources in the region.

Ouda, J.O. and Nsahlai, I.V. 2007. Nutritive value of maize stover harvested at two stages of maturity and mixed with different types and levels of protein supplements. J. Appl. h i m . Res., 32: 89-95. (20, 40, 60, 80%) Key words: Maize stover, maturity stage, protein supplements, gas production, ruminants. Studies were conducted on maize stover harvested at grain milk (MM) or dry (MD) stages and mixed with graded ratios of protein supplements (PS) including lucerne hay (LH), lespedeza hay (LPZ) and sunflower seed cake (SC). Automated in vitro gas production technique (IVGPT) was In trod uc t ionMaize is the third most produced grain after wheat and rice and leads in crop fodder production in Africa. It is widely recognised that low crude protein (CP) content is the major constraint to maize stover utilization (Hindrichsen et al., 2004). The potential protein supplements include browse legumes and agro-industrial by-products such a s oilseed cakes. Lucerne (Medicago satiua L) #Corresponding author: Tel. +27332605474; Fax +27332605067; E-mail: nsahlaii8ukzn.ac.za is a popular fodder legume for ruminants. However, high agronomic input requirement of lucerne curtails its cultivation by the numerous resource-poor farmers. A forage legume such as Sericea lespedeza [Lespedeza cuneata (Dun-Cours) G. Don] may be a suitable alternative. Sericea lespedeza is a tall growing, drought tolerant, coarsestemmed perennial that is productive on a wide range of soils including those with poor fertility (McGraw and Hoveland, 1995).The present study used the automated in uitro gas production technique (IVGPT) whose merits include: a relatively low cost, et al., 2005). The study objective was to evaluate the influence of different types and levels of protein supplements on nutritive value of maize stover-based rations. Materials and MethodsStover from white maize hybrid PAN6479 grown in Kwa-Zulu Natal Province, South Africa, were harvested either at grain milk (MM) or grain dry (MD) stage. The protein supplement (PS) feeds included sunflower (Helianthus onus) seed cake (SC), lucerne hay (LH) and lespedeza hay (LPZ). Sixty whole maize plants were randomly selected from the field, cut at the first node above ground and divided into two groups. One group had morphological components (leaf, husk and stem) individually separated while the other was left whole. The stover or morphological components were chopped, placed in labelled containers and dried in a fanned oven at 50C until they were fit for milling through a 1-mm screen. The samples were analysed for ether extract (crude fat) and CP content according t o AOAC (1990). Methods described by Van Soest et al. (1991) were used to determine the neutral detergent fibre (NDF) and acid detergent fibre (ADF). Methods described by Harris (1970) were used t o determine soluble carbohydrates (CHOso,) as follows: CHOS0, (g/kg) = 1000 -(NDF + Crude fat + Crude protein + soluble ash) gkg.I n uitro incubation was performed using automated gas production technique (IVGPT) as described b...