2002 Volume 2002 Issue 39 Pages 1-8
To study a potential aversive effect of Euphorbia supina and Euphorbia maculata on preference of feed by sheep, 4 ewes were used in 2 trials for determination of dry-matter intake and selection behavior for a mixed feed composed of wheat bran and one of two potential weeds with diverse proportions. Ewes were offered oats hay ad libitum as a basal diet for 176 days. For trial 1, Euphorbia supina was mixed with wheat bran at rates of 0, 5, 7, 10, 25, 50 and 100%. For trial 2, Euphorbia maculata was mixed at rates of 0, 10, 15, 20, 25, 50, 60, 75 and 100%. With these mixed feed, feeding behavior of ewes were observed at the interval of 3 days. A 20 g of each mixed feed was offered to ewes immediately before morning feeding for 20 min., and the behavior was recorded by video-recorder. Dry-matter intake was determined by the difference of weight at the before and after feeding by using a digital balance (weighing precision ; 0.1 g). The figures less than 1g were considered to be 0g intake. In addition, the behavior of ewes on basal diet was also recorded for 24 h.
Proximate composition of oats hay, E. supina and E. maculata were as follows : crude protein, 7.3, 11.8 and 5.6% DM ; neutral detergent fiber, 55.9, 28.3 and 40.6% DM ; acid detergent lignin, 4.1, 5.9 and 10.8% DM, respectively. At the end of each trial, ewes increased their weight. Mean environmental temperature ranged 15 to 27°C. Mean dry-matter intake of hay was 1.8±0.1 kg for trial 1 and 1.4-1-0.1 kg for trial 2 and tended to decrease as the environmental temperature increased. Ewes on a basal diet in the present study, therefore, were considered to be in normal feeding condition.
Ewes refused to eat the mixed feed with 10% of E. supina or over. Three ewes out of 4 ingested the mixed feed with 5% and only one ewe ate 7% feed. The exploratory behavior for feed tended to be longer in feed with 10% of E. supina or over. As for the mixed feed with E. maculata, feed aversion was found for 75 and 100% feeds. Three ewes ingested a small amount of feed of 60%. The exploratory behavior for feed was only found in the case for 75 and 100% feeds.
From the results of the present study, it was concluded that E. supina produced feed aversion at the levels between 7 and 10%, while E. maculata caused feed aversion at the levels between 60 and 75%. These differences in feed aversion may be responsible for the difference in levels and/or kinds of terpenoid contained in both weeds. Further works need to clarify its cause and effect.
