Effect of increasing levels of Quillaja saponaria on digestion, growth and meat quality of Barbarine lamb

It is hypothesised that saponins from Quillaja saponaria (QS) improve the efficiency of N utilisation in ruminants, thus increasing sheep growth. Therefore, this experiment was carried out to investigate the effect of oral administration of increasing levels of QS extract (0, 30, 60 and 90 mg/kg dry matter intake (DMI) containing 6, 12 and 18 mg sapogenin) on feed digestibility, growth and meat composition of sheep. Twenty-four 5–6-month-old Barbarine lambs (initial live weight 18.6 ± 1.98 kg) were allotted to four equal groups, all of which received oaten hay ad libitum and 400 g concentrate per animal. Immediately after offering the morning meal 10 ml water solutions containing 30, 60 or 90 mg of QS/kg DMI were orally administrated. Feed intake and growth rates were measured for 57 days. Thereafter, lambs were allowed a 4-day acclimation to metabolic cages before starting a 5-day total collection period. QS had no effect on total dry matter and water intakes. Administration of 60 or 90 mg QS/kg DMI decreased NDF digestibility (P=0.011); however, it had no effect on crude protein digestibility, N retention, microbial N supply and ammonia concentration in the rumen fluid suggesting that QS did not improve, as expected, the efficiency of N utilisation although a linear reduction of protozoa count in the rumen fluid just before or 4 h after distribution of the morning feed (P=0.0027 and P=0.0011, respectively) was observed. Blood profiles indicated that QS had no effect (P>0.05) on plasma urea and cholesterol concentrations. However, lambs receiving QS exhibited lower (P<0.05) concentration of plasma glucose than control lambs (without QS). No effect on both feed intake and efficiency of N utilisation may explain the absence of response of QS extracts (30–90 mg/kg DMI) on animal growth. Saturated fatty acids (SFA) and monounsaturated fatty acids in lamb meat were not influenced by the QS supplementation (P>0.05). Polyunsaturated fatty acids (PUFA) and the ratio PUFA to SFA tended to be higher in meat from the QS-supplemented animals than from control lambs. It is concluded that the administration of 30, 60 or 90 mg QS/kg DMI had a defaunation effect but failed to improve feed digestibility, growth performance and meat quality of Barbarine lambs.