Grass silage as a basic feed for store lambs. 2. Effect of harvesting system and chop length of grass silage on silage intake and performance of store lambs

Fitzgerald, J.J.

Grass and Forage Science 51(4): 378-388

1996


ISSN/ISBN: 0142-5242
DOI: 10.1111/j.1365-2494.1996.tb02072.x
Accession: 002854127

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Abstract
A perennial ryegrass (Lolium perenne) sward was cut at a leafy stage of growth and harvested with different harvesters to produce silages differing in chop length to evaluate the effect of silage chop length on silage intake and on the performance of store lambs when silage was fed as the sole diet. The silage was harvested in late May either as long silage (L), single-chopped (S), double-chopped (D), long precision-chopped (LP) or medium precision-chopped (MP) silage with the appropriate machinery. The silages were treated with formic acid at 2.5 litres t-1, were well preserved (pH 3.7-3.8) and were of high dry-matter digestibility (749-810 g DMD kg-1 dry-matter (DM)). The silages were fed ad libitum as the sole diet to Suffolk crossbred store lambs over a period of 11 weeks. Silage intake and lamb performance progressively increased as silage chop length declined from 32.4 cm (L) to 6.8 cm (MP). Silage intakes were 572, 661, 750, 893 and 1129 (+or-21) g DM day-1 for silages L, S, D, LP and MP respectively. The corresponding daily liveweight gains were -3, 40, 53, 85 and 151 (+or-7.6) g day-1. Similar increases in empty body weight gain and carcass weight gain were obtained as silage chop length declined. Rumen retention time (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake in the week before slaughter, was much shorter for silages LP and MP compared with silages L or S. Silage intake was negatively related to RRT (b = -24.5 +or- 6.1 g DM h-1 RRT). The results of this study showed that high intakes of grass silage and liveweight gains were achieved when grass was cut at a leafy stage of growth and harvested with a precision-chop harvester set to produce a moderate chop length (7 cm). The feeding of long or flail-chopped silages resulted in lower intakes and lower liveweight gains.

Grass silage as a basic feed for store lambs. 2. Effect of harvesting system and chop length of grass silage on silage intake and performance of store lambs