Tropical Grasslands (1989) Volume 23, 108114
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
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.