Effect of purple prairie clover (Dalea purpurea Vent.) hay and its condensed tannins on growth performance, wool growth, nutrient digestibility, blood metabolites and ruminal fermentation in lambs fed total mixed rations

This study evaluated the effects of purple prairie clover (PPC, Dalea purpurea Vent.) hay and its condensed tannins (CT) on feed intake, growth performance, wool growth, nutrient digestibility, blood metabolites and rumen fermentation in lambs fed diets containing PPC and alfalfa hay. Alfalfa and PPC were harvested at similar growth stage, sun-cured to'<12% moisture, and stored in a shed for 120 d. Thirty six individually fed lambs were randomly allocated into three groups and fed total mixed ration containing 40% (dry matter (DM) basis) of a pelleted barley grain based concentrate and 60% of alfalfa hay (AH), or 60% PPC hay (PH) or PH supplemented with polyethylene glycol (PH-p) for 77 d. Lambs were fed once daily and weighed bi-weekly. Faeces samples were collected in the 5th wk for 5 d to determine nutrients digestibility using acid insoluble ash as a marker. Lambs were slaughtered at the end of experiment to evaluate the carcass characteristics. Wool yield and quality were measured using a 10 cm dye band applied on d 0 and harvested on d 75. Blood samples were collected to analyze serum metabolites and antioxidant enzymes, and rumen fluid was sampled to analyze rumen fermentation products. Lambs fed PH had lower (P < 0.01) DM intake than AH or PH-p. Growth performance, wool growth parameters and carcass characteristics did not differ among diets. Lambs fed PH-p had greater (P < 0.05–0.001) DM, organic matter (OM), crude protein (CP), neutral detergent fibre (aNDF) and acid detergent fibre (ADF) digestibility than those fed AH, and greater (P < 0.05–0.001) CP, aNDF and ADF digestibility than those fed PH diet. Lambs fed PH exhibited greater apparent total tract digestibility of DM (P < 0.05) and OM (P < 0.05) and tended (P = 0.059) to have greater CP digestibility compared to those fed AH. Lambs consuming PH diet had lower (P < 0.05) blood urea nitrogen and creatinine than AH and lower (P < 0.05) blood glucose and urea than PH-p, but greater (P < 0.01) total antioxidant capacity and catalase activity than AH diet. Lambs fed PPC CT had lower (P < 0.05) concentrations of ammonia, total VFA, propionate, iso-butyrate, iso-valerate and protozoa. It was concluded that PPC hay had greater nutritive value to alfalfa hay owing to its greater DM, OM and protein digestibility, but did not improve lamb growth.