Comparison of six forage systems as a source of late summer/autumn feed for dairy heifers

Abstract

A grazing study over 6 consecutive years assessed the value of 6 alternative forage systems for growing dairy heifers during late summer and autumn in a subtropical environment. The forages were Pinto peanut (Arachis pintoi cv. Amarillo), rhizomatous peanut (Arachis glabrata cv. Prine), nitrogenfertilised pangola grass (Digitaria eriantha ssp. pentzii), lucerne (Medicago sativa), naturalized pasture and leucaena (Leucaena leucocephala). Heifers with an average weight of 210 kg were grazed on the pastures at 3.8 animals/ha in late summer and autumn of 1996 to 2001, and were supplemented with 2 kg of grain plus minerals/animal/day. Naturalised pasture was stocked at 1 animal/ha.

Feed on offer was not significantly related to rainfall. There was an average of less than 400 kg DM/ha of legume in the feed on offer in the Arachis paddocks. The target liveweight gain (700 g/animal/day) was achieved by all systems in 4 of the 6 years. Liveweight gain was linearly related to rainfall for each system, accounting for over 65% of the variation. Adding the following factors (feed on offer, sown component feed on offer, the amount of hay fed to compensate for the shortfall in feed as a result of drought and irrigation) did not improve the relationship. Animals on the lucerne system gained more liveweight in 3 of the 6 years than those on the Amarillo, Prine or nitrogen-fertilised pangola grass systems although animals grazing lucerne required a greater amount of hay each year. The naturalised pasture system performed as well as other systems, but at a much lower stocking rate and with more supplement. The leucaena system was superior to the other systems in 2001. This can partly be related to the management, which required leucaena to remain ungrazed from early spring while the other forages were used in the farm rotation until December each year.