Effect of oral administration of Agave americana or Quillaja saponaria extracts on digestion and growth of Barbarine female lamb

Agave aloe (Agave americana) leaves are high in saponins (ca. 80 g Eq. diosgenin/kg dry matter). We hypothesised that saponins in Agave extract could improve feed efficiency, thus increasing lamb growth. A 60-day feeding trial followed by a digestibility trial was conducted on five equal groups (n=6) of 5-6-month-old Barbarine female lambs (initial BW 23.1±4.3 kg). All animals received oaten hay ad libitum and 400 g concentrate and each group was randomly assigned to one of the following five treatments. A control group was not drenched with extracts but groups AE120, AE240 and AE360 were drenched with Agave extract (AE) containing 120, 240 and 360 mg saponins/kg DM intake, respectively. The fifth group was drenched with Quillaja saponaria (QS) solution containing 120 mg saponins/kg DM intake (QS120). Administration of AE and QS had no effect (P>0.05) on diet intake and nutrient digestibility and nitrogen balance. However, these extracts decreased protozoa number in the rumen fluid (P=0.004) and blood cholesterol (P=0.02) and glucose (P<0.01). The growth rates of lambs calculated for the whole feeding trial (60 days) averaged 59.6, 77.8, 77.2, 79.0 and 76.6 g/d with control, AE120, AE240, AE360 and QS120 diets, respectively. Contrast analyses showed that the mean effect of extracts (AE and QS) on daily gain reached significance (P=0.036). The defaunation effect induced by the administration of QS or AE might have impacted positively on the growth rate of female lamb. It is concluded that AE and QS may have potential as natural defaunating agent. Numerical increase of average daily gain suggests that AE and QS could have better effect with quality diets.