Effects of selection for shear strength on the voluntary intake and digestion of perennial ryegrass fed to sheep

T. Inoue, I.M. Brookes, T.N. Barry and A. John

Department of Animal Science, Massey University, Palmerston North and Biotechnology Division, DSIR, Palmerston North

Proceedings of the New Zealand Society of Animal Production. 1989, 49: 221-224

Two perennial ryegrass cultivars, selected on the basis of leaf shear strength (LS and HS) were fed to Romney wethers in May and October 1988 indoors for 2 weeks to measure voluntary intakes. Higher daily intakes of LS than HS (102 gDM/kg0.75 v 86 gDM/kg0.75) were recorded in October, but no significant differences were observed in May, apparently as a result of high amounts of dead matter in the herbage.

Eight rumen fistulated wethers were fed either LS or HS cultivars in May. Cr-EDTA-Ru-phenanthroline marker solution was infused for 6 days to measure rumen outflow and total faecal collection was made for digestibility determination in May. Total faecal collection was also made in October following the measurement of voluntary intake. In both experimental periods eating behaviour was also recorded.

Low digestibilities were observed in May with no significant differences between LS and HS (65% v 67%), but in October high digestibility of HS than LS was observed (76% v 73%), and also longer rumination times for sheep fed HS than LS were recorded in October (542 min/kg/DM/day v 426 min/kgDM/day). The rate of DM disappearance of herbages containing low amount of dead matter (8%) when suspended in the rumen of cows, was significantly greater for LS than HS. Further investigations with good quality pasture with low dead matter are suggested.

Keywords: NZSAPAB; Shear strength; intake; digestibility; retention time; ryegrass; sheep