The nutritive value of laboratory ensiled lablab ( Lablab purpureus ) and pearl millet ( Pennisetum americanum )

A laboratory study was conducted with fieldgrown pearl millet ( Pennisetum americanum ) and lablab ( Lablab purpureus ) to examine the effects of addition of lablab in varying amounts on the quality of millet silage. Combinations compared were: 0:100, 15:85, 30:70 and 50:50 mixtures of lablab and millet, respectively. All silage treatments contained similar concentrations of dry matter, organic matter and ether extract. Incorporation of lablab led to a small increase in crude protein, crude fibre and nitrogen–free extract. All silages showed low crude protein concentrations and would barely supply N requirements for maintenance of cattle. The lactic acid content of the silage increased as the proportion of lablab in the mixture increased. The silage pH values, which ranged from 4.1–4.5, showed that all lablab — millet mixtures were adequately fermented with favourable aroma and colour. The Ca and P concentrations increased with higher incorporation of lablab, while the converse was the case with Mg, Na, K and S. Mineral supplements, in particular S and Na, would need to be fed if these silages constituted a high proportion of the diet of cattle, especially lactating cows. Field studies are required to determine if these results can be duplicated on a practical scale, while feeding studies with ruminants will determine the acceptability of the silages and animal performance. Introduction In the northern part of Nigeria, where the grazing season is limited and pasture production fluctuates widely, silage making offers a means of improving the utilisation of pastures. As reported by Cowan et al. (1993), forage growth on tropical and subtropical perennial pastures often exceeds the feed requirements of dairy herds during summer and early autumn. These authors estimated that the level of utilisation of the available pasture was 30–50%, leading to considerable wastage. There has been considerable debate on whether the surplus forage in summer can be conserved and used to partly fill the winterspring feed gap (Kaiser et al . 1993). Ensiling has been suggested as the preferred conservation option as climatic conditions during the period when the surplus exists are considered unsuitable for haymaking. Given the generally poor preservation of tropical pasture as silage, various compounds such as formaldehyde and acids have been used as additives in making silages from grasses (Morrison 1979; Thompson et al . 1981). These compounds have been a primary mechanism for improving the feeding value of silage. Pearl millet ( Pennisetum americanum ) and lablab ( Lablab purpureus ) are promising forage crops with high potential for integration into Nigerian livestock production systems. The crops are highly adapted to a range of agronomic conditions with fodder yields of 2.7–7.7t/ha in locations varying from the semi-arid to the subhumid zone, where rainfall varies between 600–1100mm (Agishi 1985). Both crops have the characteristics of easy establishment under local conditions, rapid growth and high yields. Umoh et al . (1981) showed incremental benefits in milk, beef and small ruminant production from using maize ( Zea mays ), millet, sorghum straws, gamba ( Andropogon gayanus ) and elephant grass ( Pennisetum purpureum ) Correspondence: J.T. Amodu, National Animal Production Research Institute, Ahmadu Bello University, Shika-Zaria, Nigeria. E-mail: tunjiadeyinka@yahoo.com 06/05_07_Amodu et al.fm Page 117 Tuesday, May 17, 2005 8:55 AM