Tropical Grasslands (1989) Volume 23, 108–114

THE EFFECT OF LEUCAENA LEUCOCEPHALA ON THE REPRODUCTION OF BEEF CATTLE GRAZING LEUCAENA/GRASS PASTURES

R.M. JONES1, M.W. McLENNAN2 and K.F. DOWSETT2

1CSIRO Division of Tropical Crops and Pastures, 306 Carmody Road, St. Lucia, Queensland 4067, Australia
2Department of Farm Animal Medicine and Production, University of Queensland, St. Lucia 4067, Australia

Abstract

A herd of up to 16 cows was run from 1979 to 1986 on leucaena–grass pastures at Samford in south-east Queensland. Cows remained on these pastures for 4 years. Four new heifers, which had grazed a leucaena–grass pasture for the previous year, were introduced into the mating herd each year. During the last 5 years of the experiment, leucaena comprised about 40–55% of the diet during mating and early pregnancy. The overall calving percentage was 66%, with a trend towards lower percentages in wetter years. The calving percentage of the farm or control herd which did not graze leucaena was 90%, with little fluctuation between years. The calving percentage of cows formerly grazing leucaena pastures improved from 54% to 75% when they were returned to the farm herd. Bulls used on the leucaena herd achieved high calving percentages (about 90%) when used on the farm herd in subsequent years. It was concluded that high intakes of leucaena could depress calving percentages and should be avoided in the first 3 months of pregnancy. Reasons for the depression in calving percentage, and the possible impact of DHP degrading bacteria, are discussed.

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