Intake, Digestibility In vivo, N Utilization and In sacco Dry Matter Degradability of Grass Silage Harvested at Three Stages of Maturity

Marina Vranić,Goran Perčulija,Mladen Knežević,Josip Leto,Krešimir Bošnjak

doi:10.5713/ajas.2009.80118

Abstract

The objective of this experiment was to study the effects of grass maturity at harvest on the nutritive value of grass silage (GS) in relation to voluntary intake, digestibility, nitrogen (N) utilization and in sacco dry matter (DM) degradability. Silage was cut from a sward dominated by orchardgrass (Dactylis glomerata L.) at the late-vegetative (early-cut), internode elongation (medium-cut) and flowering (late-cut) stages of growth. The DM yield at harvest was the lowest for early-cut silage (5.4 t/ha) and increased to 6.5 and 7.0 t/ha for the medium and late-cut silage respectively. As the crop matured, the crude protein (CP) concentration decreased significantly (p < 0.05) and there was a marked increase in acid detergent fiber (ADF) concentration (p < 0.001). The three different silages were offered to four 18-month old Charolais wether sheep to measure the voluntary intake, in vivo digestibility and N retention over four 21-day periods in an incomplete changeover design. Silage degradability characteristics were determined using four fistulated sheep to measure DM degradability over 3, 6, 12, 24, 48 and 72 h. There was a linear decrease in the voluntary intake of silage fresh matter, DM, organic matter (OM) and neutral detergent fiber (NDF), digestibility of DM, OM, NDF, ADF and CP, and digestibility of OM in DM (D-value) (P-L < 0.01) as harvesting of grass was delayed. Nitrogen intake, N output in urine. N output in faeces and N balance also linearly decreased (P-L < 0.01) with postponed harvesting of grass for silage. DM degradability and effective degradability (ED) significantly decreased with increasing maturity of grass at harvest. The results suggest that harvesting date has a significant influence on the nutritive value of GS in terms of intake, digestibility, N balance and in sacco degradability in the rumen. It was concluded that early harvest GS ensured higher intake, digestibility, N intake and DM degradability in comparison with the medium and the late cut GS as a result of improved rumen N efficiency and utilization probably due to a better balance of available energy and protein.

Highlights

Grass silage (GS) is the primary form of conserved forage for winter-feeding of ruminants in Europe
Bags from the rumen, they were put into icy water, washed in a washing machine for 15 min using cold water and kept in a freezer
Grass was cut at late rumen, they were dried for 2 days at 60°C

Summary

INTRODUCTION

Grass silage (GS) is the primary form of conserved forage for winter-feeding of ruminants in Europe. It varies greatly in terms of chemical and biological composition due to the impact of factors such as the maturity stage at harvesting, sward botanical composition, level of fertilisation (Rahman et al, 2008), climate and ensiling techniques (Shaoa et al, 2005) upon the fermentation process in the silo and on nutritive value. The low nitrogen (N) content in mature forage plants may limit animal production (Adams et al, 2002; Kaiser et al, 2007). Silage volatile fatty acids (VFA) were measured by gas liquid chromatography and lactic acid was determined enzymatically on an Express Auto biochemical analyzer using juice expressed from the silage

MATERIALS AND METHODS

AND DISCUSSION

CONCLUSIONS