Short term consumption of Havardia albicans tannin rich fodder by sheep: Effects on feed intake, diet digestibility and excretion of Haemonchus contortus eggs

This experiment determined the short term effect of feeding Havardia albicans (HA) tannin rich fodder on voluntary feed intake (VFI), dry matter digestibility (DMD), digestible DM intake (DDMI) and fecal excretion of Haemonchus contortus eggs by hair sheep. Polyethylene glycol (PEG) was used to identify possible roles of tannins on the results. Hair sheep lambs (12.6 ± 3.33 kg body weight (BW)) without browsing experience and raised free of gastrointestinal nematode infections were maintained in metabolic cages. There were 5 experimental groups with 3 of them infected with H. contortus (350 L3/kg BW): Group IC: infected and fed a tannin free diet (n = 8), Group IHA: infected and fed fresh HA fodder alone (n = 5) and Group IHA + PEG: similar to IHA plus PEG (n = 5). Two groups remained free of infection and were fed fresh HA fodder either alone (NIHA) (n = 5) or with PEG (NIHA + PEG) (n = 5). Sheep were assigned to the experimental groups when the H. contortus infection was patent (i.e., day 25 post-infection). The HA fodder was fed daily at 14 g DM/kg BW) for 7 d as part of the diet after a 5 d of adaptation. A concentrate feed containing 150 g/kg crude protein (CP) and 10.1 MJ/kg DM of metabolizable energy, and sugar cane molasses, were used to meet requirements for a BW gain of 100 g/d. Infected sheep (IHA) had higher HA consumption than non-infected (NIHA) (P<0.05). Such differences in HA fodder consumption due to infection did not occur between PEG supplemented groups. As a result, VFI of the NIHA group was lower than the other groups (P<0.05). Sheep fed HA had a lower DMD and DDMI compared to controls and use of PEG did not have an impact. Short term consumption of HA fodder reduced fecal egg excretion by 58.8% in the IHA versus the IC group (P<0.01). Such a reduction in egg excretion did not occur in the IHA + PEG group. Results show that sheep infected with H. contortus may increase consumption of tannin rich foliage in spite of negative effects on digestibility of the foliage. Such an increase in foliage consumption reduced fecal excretion of nematode eggs and these effects were blocked by PEG.