The effect of fermentation quality on the voluntary intake of grass silage by growing cattle fed silage as sole feed

¹ Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, NO-1432 Ås, Norway

^* To whom correspondence should be addressed. E-mail: sophie.krizsan{at}umb.no.

	Abstract

This study was designed to separate the effect of fermentation quality on voluntary intake of grass silage from other feed factors affecting intake. Variations in DMI were quantified and the impact on intake modeled. Relationships between individual silage components and intake were examined. A partially balanced change-over experiment with 30 Norwegian Red steers (137 ± 16.4 kg of BW) was carried out to determine the intake of 24 silages and of hay harvested from the same parent crop within 60 h. Five forages were fed at a time in each of five 3-wk periods. Every 3-wk period was preceded by 2 wk of feeding standard silage. Silage DMI ranged from 1.79 to 2.65, with mean 2.38 kg · 100 kg BW^-1 · d^-1. Hay DMI averaged 2.43 kg · 100 kg BW^-1 · d^-1. Ranges (mean) for composition of silages were: DM, 166 to 237 (213) g/kg; water-soluble carbohydrates, 16.3 to 70.9 (33.0) g/kg of DM; acetic acid, 11.5 to 64.7 (28.6) g/kg of DM; propionic acid, 0 to 5.2 (1.0) g/kg of DM; butyric acid, 0 to 25.1 (6.0) g/kg of DM; lactic acid (LA), 2.2 to 102 (49.3) g/kg of DM, and NH₃-N (not corrected for additive-derived N), 89.3 to 255 (153) g/kg of total N. Silage DMI was closely related to (P < 0.05) DM, ADL, VFA, LA, total acids (TA), LA/TA ratio, ADIN, NH₃-N (not corrected), histamine, tryptamine, cadaverine, and the total sum of amines (explained variation in intake ranged from 14 to 53%). The 2 best models describing silage DMI included concentrations in the silage of propionic acid, butyric acid, and LA, and these models explained 75 and 84% of the variation in DMI. The strong correlation (r = 0.84, P < 0.05) between total NH₃-N and butyric acid concentrations in silages indicates that these variables described the same variation pattern. The inclusion of NH₃-N in equations describing the effect of fermentation quality on DMI of low DM grass silage was less useful than that of butyric acid. This was due to the confounded relationship between NH₃-N concentration in silages and the use of ammonium containing preservatives and to the difficulties in the practice of correcting for the added ammonium.

Key Words: cattle, fermentation quality, grass silage, prediction equation, voluntary intake

This article has been cited by other articles:

				P. Huhtanen, M. Rinne, and J. Nousiainen Effects of Silage Soluble Nitrogen Components on Metabolizable Protein Concentration: A Meta-Analysis of Dairy Cow Production Experiments J Dairy Sci, March 1, 2008; 91(3): 1150 - 1158. [Abstract] [Full Text] [PDF]