Abstract
A study was carried out to gain quantitative information on the diet-dependent faecal microbial biomass of dairy cows, especially on the biomass fractions of fungi, Gram-positive (G+) and Gram-negative (G-) bacteria. Groups of high-yield, low-yield and non-lactating cows were investigated at four different farms. A mean faecal microbial biomass C (MBC) concentration of 33.5 mg g-1 DM was obtained by the chloroform fumigation extraction method. This is similar to a mean microbial C concentration of 31.8 mg g-1 DM, which is the sum of bacterial C and fungal C, estimated by cell-wall derived muramic acid (MurN) and fungal glucosamine (GlcN), respectively. However, the response of these two approaches to the feeding regime was contradictory, due to feeding effects on the conversion values. The higher neutral detergent fibre (NDF) and acid detergent fibre (ADF) concentrations in the non-lactating group led to higher (P < 0.05) concentrations of cellulose and lignin in their faeces in comparison with the lactating cows. This change in faecal chemical composition in the non-lactating group was accompanied by usually higher ratios of G+/G- phospholipid fatty acids (PLFA), ergosterol/MBC and fungal C/bacterial C. Although bacteria dominate the faecal microbial biomass, fungi contribute a considerable mean percentage of roughly 20% to the faecal microbiome, according to PLFA and amino sugar data, which requires more attention in the future. Near-infra red spectroscopic estimates of organic N and C fractions of cow faeces were able to model microbial biomarkers successfully, which might be useful in the future to predict its N2O emission potential and fertilizer value.
Highlights
Cow faeces are important for maintaining soil fertility as composted farmyard manure [1, 2] and as solid dung [3]
The higher concentrations of neutral detergent fibre (NDF) and acid detergent fibre (ADF) in the diet of non-lactating cows led to higher concentrations of cellulose and lignin in their faeces
The change in quality was accompanied by higher ratios of G+/G- bacteria, based on phospholipid fatty acids (PLFA) analysis, and higher concentrations of fungi, based on fungal GlcN and ergosterol analysis
Summary
Cow faeces are important for maintaining soil fertility as composted farmyard manure [1, 2] and as solid dung [3]. Protein and fibre concentrations in the diet modify the chemical and the microbial composition of faeces [7, 8, 9, 10] 12], which typically indicates faster organic matter decomposition in the habitat where it was produced, as compared with its decomposition at translocated places [13]. For this reason, knowledge about the characteristics of solid manure should be increased, as investigations of feeding effects have mainly focused on slurry in the past
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