Nutrient supply for lamb growth from Grasslands Puna chicory (Cichorium intybus) and Wana cocksfoot (Dactylis glomerata)

Two groups of 10 intact Border Leicester ram lambs (10 weeks old; 22.7ti.59 kgLW) were grazed on either Grasslands Puna chicory (Puna) or Wana cocksfoot (Wana) over a six week period in late spring, to relate liveweight gain (LWG) to nutrient intake and supply at the duodenum from the 2 forages. Both pastures were in a vegetative state and offered at a high allowance (12.5 to 15 kgDM/ lamb/d). Chemical composition (%DM) of oesophageal extrusa sample was 8 1.5 and 89.4 OM, 34.9 and 48.1 neutral detergent fibre (NDF)and2.6and3.6NandtheinvitroOMdigestibilitywas72.6and74.2%forPunaandWanarespectively. Liveweight wasrecorded weekly and intake estimated in week 3 by reference to dilution of two faecal markers, Cr,O, and Yb acetate. Digestion characteristics in the rumen and nutrient supply at the duodenum was measured in companion lambs (n=6) fitted with rumen and duodenal cannulae using Cr-EDTA and Yb acetate as the solute and particulate phase digesta markers, respectively. LWG (g/d) was 268k20.9 on Puna and 205k19.1 on Wana. Digestible OM intake (DOMI) and nitrogen intake (NI) was lower on Puna (16.10 and 0.7 1 g/kgLW/d) than Wana (26.69 and 1.39 g/kgLW/d), and non-ammonia N (NAN) tlow at the duodenum was similar(O.70~0.85g/kgLW/d) mainlydue tovariableNlossasammoniaacross therumen. Itappears that thedisparity inLWGoflambs grazing Puna and Wana may be related to differences in the balance of nutrients rather than the quantitative intake or supply of any one nutrient. This is shown in the ratio ofduodenal NAN:DOMI which for Puna (43.5) was similar to legumes but the ratio for Wana (31.9) was lower than for othergrasses. It is concluded tentatively that the nutritive value of Puna and Wana for lamb growth is bestdescribed by the NAN:DOMI ratio.

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