Effect of dietary Urtica cannabina on the growth performance, apparent digestibility, rumen fermentation and gastrointestinal morphology of growing lambs

Dietary supplementation with Urtica cannabina is a viable source of available protein and fibre for livestock nutrition. To investigate the effect of U. cannabina on gastrointestinal development of growing animals, 32 male, 120-day-old Ujumuqin × small-tailed Han lambs were randomly assigned to one of the four dietary treatment groups: (1) G50 = 500 g/kg concentrate + 500 g/kg mixed forage (control); (2) L50 = 500 g/kg concentrate + 500 g/kg Leymus chinensis; (3) U50 = 500 g/kg concentrate + 500 g/kg U. cannabina, or (4) L25-U25 = 500 g/kg concentrate + 250 g/kg L. chinensis + 250 g/kg U. cannabina. The four dietary treatments had similar energy and crude protein (CP) levels but different neutral detergent fibre level. Diets were provided in single pellet form and separately offered for the 57-day experimental period. All lambs were slaughtered after the feeding trial. The results showed the following: (i) there was no differences in dry matter intake or weight gain between groups; (ii) lambs fed the U50 and L25-U25 diets had greater apparent digestibility values of CP (P = 0.003) and neutral and acid detergent fibre (P = 0.020; P = 0.030), as compared to those fed the control diet; (iii) the molar proportion of acetate in rumen fluid increased (P = 0.039) and that of butyrate decreased (P < 0.001) in the U50 diet, as compared to the other diets; however, total volatile fatty acids was lower (P = 0.045) than the L50 and L25-U25 diets; (iv) the papillae width in the dorsal and ventral rumen walls were smaller (P = 0.039; P = 0.046) in the control group than the other three groups, and corneum thickness in both rumen sides were thinner (P = 0.027; P = 0.050) in the U50 and L25-U25 groups than in the control and L50 groups; and (v) shallower (P = 0.012) crypt and greater (P = 0.020) villus to crypt ratio in the jejunum were observed in the U50 and L25-U25 groups than in the control and L50 groups, and there was a tendency for villus height to be increased in the duodenum (P = 0.083). We conclude that substitution of mixed forage or L. chinensis with U. cannabina had the beneficial effect on diet digestibility and gastrointestinal tract traits of growing lambs. In grassland systems, U. Cannabina has been found to improve the management of degraded grassland with no detrimental effects on animal performance.