Foam stability and buffering capacity in cultivars of lucerne (alfalfa)

Abstract

When lucerne is used for making silage it is prone to developing inferior quality because of a high pH. When lucerne is directly grazed by livestock it is prone to causing bloat, which can be lethal for individual animals. This project examined whether there are cultivar differences in buffering capacity and hence silage-making quality, and in foam stability in leaf extracts and hence the likely persistence of foam in the digesta of the animal. If differences exist, it should be possible either to choose cultivars that are less prone to these problems or to genetically select for superior silage-making and low bloat potential properties using the superior cultivars. Leaf extracts from 12 lucerne cultivars were screened for foam stability, and 32 cultivars were screened for buffering capacity. There were significant differences between 3 cultivars (Sceptre, Aurora and Cimarron) for foam stability, and between 4 cultivars (PL 55, SARDI 66, Trifecta and Oro) for buffering capacity. There was sufficient variation in both characteristics to warrant testing the inclusion of these traits in a lucerne breeding program. All the cultivars tested for silage pH had an unacceptably high pH, even those with lower buffering capacities. This indicated that it would be inappropriate to promote the existing low buffering capacity cultivars as suitable for silage, and that further selection for lower buffering capacity is needed.