LAILA C. BERNAL1, TASSILO TIEMANN2, CARLOS LASCANO1, MICHAEL KREUZER2, HANS-DIETER HESS3
1Centro Internacional de Agricultura Tropical (CIAT), Colombia
2Swiss Federal Institute of Technology (ETH), Institute of Animal Science, Switzerland
3Agroscope Liebefeld-Posieux Research Station (ALP), Switzerland
Low availability and poor quality of forages for livestock are major constraints faced by tropical smallholders. This is particularly relevant in regions with low-fertility soils and extended dry seasons. Shrub legumes have been suggested as promising feeds in the dry season, and CIAT has selected some accessions of species with good agronomic performance on low"=fertility soils and under drought. Many of these species are characterised by high contents of condensed tannins (CT). Particularly one accession of Calliandra calothyrsus showed auspicious potential regarding ruminal fermentation dynamics in vitro and was therefore tested for its suitability as supplement to grazing cattle. In a duplicated 4 x 4 Latin Square design, 8 dual purpose cows (Holstein x Zebu) kept on a Paspalum notatum pasture, were supplemented with Vigna unguiculata, a more difficult to grow high quality herbaceous legume, and C. calothyrsus (CIAT 22310) alone or in mixtures at proportions 1:2 and 2:1. Allowance for supplementation was set to 1kg of dry matter per 100kg of body weight. Cows were allowed to adapt for 7 days, followed by 7 days of measurement. Milk yield and composition were measured daily. Consumption of the legumes was 87% of the amount offered with Vigna and only 29% with Calliandra. The mixture with low Calliandra proportion did not differ in consumption from the Vigna"=only supplement, while that with the high Calliandra proportion was intermediate with 59% of the amount offered (P<0.05). Milk yield linearly decreased with increasing proportion of Calliandra in the supplement. Accordingly, milk yield was highest (P<0.001) with Vigna"=only (5.3kgd-1), and declined to 4.7, 4.4 and 3.6kgd-1 with increasing Calliandra level. There were no treatment effects on contents of fat, solids"=non-fat and total solids. Milk urea N declined (P<0.05) with increasing Calliandra proportion from 6.3 to 3.7mgdl-1 as expected from the protein"=binding properties of the Calliandra CT. In conclusion, C. calothyrsus had a low suitability as sole protein supplement, but it may be added at low proportions if availability of Vigna is limited. When supplemented, a major limitation seems to be the low palatability apart from the high CT content.
Keywords: Calliandra, legumes, milk production, supplementation, tannins