Effects of selection for shear strength on structure and rumen
digestion of perennial ryegrass
A. John, T. Inoue, I.M. Brookes, W.F. Hunt and H.S. Easton
Biotechnology Division, DSIR, Palmerston North; Department of
Animal Science, Massey University, Palmerston North and Grasslands
Division DSIR, Palmerston North
Proceedings of the New Zealand Society of Animal Production.
1989, 49: 225-228
Low voluntary intake and animal performance with perennial
ryegrass has been attributed to its high leaf strength. Perennial
ryegrass populations were selected for high or low shear strength and
individual plants of low (LS) and high (HS) selections grown in a
controlled environment. Shear strength of LS leaves (290 g) was half
that of HS leaves. LS leaves were shorter, narrower and lighter.
However, shear strength of LS remained significantly lower after
adjustment for differences in leaf width. Shear strength in both
selections declined from leaf base to leaf tip. LS leaves contained
less sclerenchyma but had similar vascular tissue content. Sclerenchyma
was significantly correlated with shear strength (r=0.82).
Chopped leaves (5 cm) from both selections, placed in polyester bags
were subjected to rumen microbial digestion. The higher shear strength
of HS selected plants was maintained for at least 24 h rumen digestion.
It is concluded that lower shear strength was a result of decreased
sclerenchyma content and that potential improvements arising from easier
breakdown would be maintained during rumen digestion in vivo.
Keywords: NZSAPAB;
Leaf sheaf length; leaf structure; ryegrass; digestion
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Last Updated 18-03-1997
