Relationships between feeding and microbial faeces indices in dairy cows at different milk yield levels

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 N 2 O emission potential and fertilizer value.

Feed Quality and Feeding Level Effects on Faecal Composition in East African Cattle Farming Systems

“…In the present study, the higher fungal C concentration at MER60, where feed intake of NDF and ADF were higher and intake of CP was lower than in the other diets, agree with previous findings [ 3 , 14 , 15 , 17 ]. However, the generally positive correlation of CP intake with the fungal C/bacterial C ratio and the negative correlation of CP intake with MurN across all data seem to contradict these results.…”

“…Across both experiments, the average concentrations of MurN and GalN, as well as that of microbial C in the feces of Boran steers and Holstein × Boran heifers, were in the range reported for Holstein heifers and cows in Germany [ 3 , 14 , 15 , 17 ]. In contrast, the average fungal GlcN concentration was slightly higher, which might be explained by the lower CP and higher NDF concentrations of the diets in the current two experiments.…”

“…Increased feed intake of CP and CP digestibility were negatively related to fecal NDF concentrations, as previously observed [ 14 , 36 ], whereas the similar strong relationships to ADF are only congruent with the data of Zhu et al [ 36 ]. The negative effects of increased NDF and ADF intake on fecal NDF and ADF concentrations indicate complex interactions of these two fiber fractions during microbial decay in the rumen and lower gastrointestinal tract [ 17 ].…”

“…However, the generally positive correlation of CP intake with the fungal C/bacterial C ratio and the negative correlation of CP intake with MurN across all data seem to contradict these results. One possibility might be a shift in bacterial community structure towards Gram-negative bacteria at MER60 and MER40 [ 17 ], which have a 70% lower MurN concentration than Gram-positive bacteria [ 29 , 30 ]. Another possibility might be a decrease in fungal cell volume, which results in overestimates of fungal C [ 30 ].…”

“…Higher fecal neutral detergent fiber (NDF) and hemicellulose concentrations were associated with an N deficient diet compared with an N balanced CP diet, whereas the amino sugar concentrations did not differ between these two treatments [ 14 ]. However, the amino sugars muramic acid (MurN) and fungal glucosamine (GlcN) were useful indicators for determining fecal bacterial and fungal biomass in animal feces of several other experiments [ 15 , 16 , 17 ].…”