Nutritive value and anthelmintic effect of sainfoin pellets fed to experimentally infected growing rabbits

Summary

Alternative strategies to synthetic chemical drugs are needed in livestock and are a key issue in organic farming today. This study aimed at examining the potentialities of sainfoin, a legume rich in condensed tannins, as a nutraceutical that combines nutritive and antiparasitic effects in rabbits. To test the effect of infection with a helminth (I: infected groups; NI: not infected groups) and the effect of substituting 40% of the alfalfa in a control diet (C) with sainfoin (diet 5), four groups of 16 weaned rabbits were arranged according to a 2 x2 bifactorial design. The sainfoin diet differed from the control by its tannin concentration (1.8% v. 1.0% tannic acid equivalent) and its ADL concentration (84 v. 43 g/kg). For each diet, 16 rabbits were infected with 2125 third stage larvae of Trichostrongyl us colubrifornnis. Growth, feed intake, feed conversion ratio and nematode faecal egg counts (FECs) were controlled for 6 weeks. A digestibility trial was performed. After necropsy, adult worms and eggs in utero per female were counted and egg-hatching rate calculated. Growth tended to be lower for 5 groups than for C groups (381 v. 39.5 g/day; P = 0.06). Feed intake was higher for 5 groups compared with C groups (+5.2g dry matter/day; P <0.01), as was the feed conversion ratio (12 v. 2.9; P < 0.001), probably in relation to the dietary ADL level. Protein digestibility was reduced in 5 groups compared with C groups (-6.0 points; P < 0.001), probably associated with the effect of the tannin concentration. Digestibility of hemicelluloses was reduced in infected rabbits compared with non-infected ones (-5 points; P = 0.01). Using the substitution method, the digestible energy of dehydrated sainfoin pellets used as raw material was calculated at 11.12 MJ/kg and digestible proteins at 110g/kg. The infection did not produce any clinical signs of digestive disorders. No differences were observed according to the diet, neither in the number of adult worms (972; P = 0.50), the number of eggs in utero per female (14; P = 0.95), nor FEC (400 eggs/g; P = 0.57). In contrast, the rate of faecal egg hatching in the 5 group tended to be lower than in the control (58.3% v. 85.2%; P = 0.08). In conclusion, sainfoin seems to fit nutritive requirements for rabbits, supplies a large quantity of fibre and particularly lignins, and limits the development of nematode eggs in faeces.