Tropical Grasslands (1989) Volume 23, 219224
DIGESTION OF SEED FROM HARD-SEEDED SELECTIONS OF MACROTYLOMA UNIFLORUM (HORSE GRAM) BY CATTLE
B.W. NORTON1, C. WHITFORD1 and I.B. STAPLES2
1Department of Agriculture, University of Queensland, St. Lucia, Queensland, 4067.
The digestibility and survival of seed of four lines of Macrotyloma uniflorum was studied in cattle. The seed was fed with Pangola grass (60–65% digestibility) at a rate of 40% in the dry matter offered (77 g/kg 0.75 /day). The percentage of hard seed in the four lines was: CPI 47055A – 23%, Line 3–38–1 – 18%, Line 2–23–3 – 11 % and CPI 32108 – 0%. Seed size increased as the proportion of hard seed decreased. The percentages of whole seed (c. 95%) and dead seed (3%) were similar for all lines. With decreasing hard seed content, there were increases in organic matter (67–71), nitrogen (58.2–67.2), total seed (73.5–80.5) and whole seed (78.1–82.0) digestibility. Mastication resulted in 47, 27 and 74% loss of hard seeds in the whole seed of lines 47055A, 3–38–1 and 2–23–3 respectively. Although 14 to 21 % of the whole seed ingested was excreted in faeces, only a small proportion (< 5%) was germinable. Significantly more hard live seed ingested from lines 47055A and 3–38–1 was excreted in faeces (29 and 30% respectively) than for lines 2–23–3 and 32108 (8.0 and 0% respectively). It was concluded that for M. uniflorum a minimum level of 15% hard seed was required to ensure the passage of significant amounts of hard seed through the digestive tract of cattle.