A comparison of Italian ryegrass (Lolium multiflorum) cultivars Exalta and Midmar with respect to their nutritive value for shee

Author: H.H. Meissner
Year: 1996
Issue: 2
Volume: 26
Page: 37 - 41

The nutritive value of Exalta was compared with Midmar in a grazing trial with lambs and in a digestion trial with mature wethers. The study was conducted between 17 August and 8 October 1993. Fifteen lambs per cultivar grazed the pastures using a two paddock per cultivar rotation procedure. Intake was measured from IVDOM of oesophageal samples and OM excreted as collected by faecal bag. Lambs were weighed regularly and wool production was measured from a 100 cm2 patch on the right mid-rib area. In the digestion trial, fermentation endproducts and nutrient disappearance in the gut were measured through multiple cannulae using Yb-acetate and Cr-EDTA as markers. Five sheep were used per cultivar; they were fed freshly cut ryegrass at four equally spaced intervals in 24 h. In both trials, DM content of the herbage exceeded 18% so high moisture content should not have limited forage intake. Cell wall content was more often lower for Exalta than for Midmar, the difference being primarily due to cellulose. In contrast, TNSC contents were more often higher. Other constituents did not differ significantly. OM intakes did not differ significantly between cultivars, being 80.2 and 84.3 g OM/ kgWO.75/d for Exalta in the grazing and digestion trial respectively, and 76.1 and 79.1 g OM/kgWO 75/d for Mid-mar. ADG in the grazing trial did not differ significantly, 239 g/d for Exalta and 224 g/d for Midmar, but clean wool yield was highly significantly lower for lambs grazing Exalta (21.0 vs 34.4 g/100 cm2). None of the rumen fermentation parameters or nutrients which disappeared in the gut differed significantly, except CP where 86% of CP intake disappeared postruminally on Exalta versus only 62% on Midmar. The higher TNSC contents of Exalta presumably enhanced microbial protein production in the rumen and thereby promoted higher protein flow to the small intestine. However, wool production results were opposite to that expected from protein supply only.

Keywords: Exalta, Midmar, Nutritive value, ryegrass, sheep
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