Amino acid composition of bacteria harvested from the rumen of dairy cows fed three diets differing in protein content and rumen protein degradability at two levels of intake

Abstract

Norway). Amino acid composition of bacteria harvested from the rumen of dairy cows fed three diets differing in protein content and rumen protein degradability at two levels of intake.Six dairy cows fitted with rumen and duodenal cannulae were assigned to two replicated 3×3 Latin squares in order to examine amino acid (AA) composition of rumen liquid-associated bacteria (LAB) and solid-adherent bacteria (SAB). Treatments comprised three concentrate mixtures differing in the amount of rumen degradable intake protein (DIP): 13.4, 11.4 and 10.1% of DM, respectively. Measurements were taken in early lactation, at high feeding level (19.7 kg DM day -1 ), and repeated at late lactation (10 kg DM day -1 ) with the same animals and diets. The SAB contained more AA than LAB (P < 0.05), and differences in AA profiles between LAB and SAB were observed for 9 out of 17 AA studied. Feeding level affected only four AA. Increased levels of DIP in the concentrate mixtures increased the content of AA in the bacteria (P < 0.05). Addition of formaldehyde to the ruminai samples prior to bacterial isolation reduced the total AA content by 11%, on average.

Amino Acid Content and Profile of Protozoal and Bacterial Fractions Isolated from Ruminal Contents of Lactating Dairy Cows Fed Diets Differing in Nitrogen Supplementation

“…In general, rather good agreements were shown between the results observed in these studies and those observed in the present investigation. Thus, for arginine, leucine, cystine (not reported in the study of Chiquette & Benchaar, 1998), phenylalanine, tyrosine, threonine, glycine and alanine, the results of the present study were fully in agreement with those of Martin et al (1996), Chiquette & Benchaar (1998), Volden & Harstad (1998), whereas for histidine, isoleucine, glutamate and serine they differed from those of the cited studies. The higher lysine proportion in the LAB than in the SAB observed in the present study is in contrast to that reported by Chiquette & Benchaar (1998), Volden & Harstad (1998).…”

“…Thus, for arginine, leucine, cystine (not reported in the study of Chiquette & Benchaar, 1998), phenylalanine, tyrosine, threonine, glycine and alanine, the results of the present study were fully in agreement with those of Martin et al (1996), Chiquette & Benchaar (1998), Volden & Harstad (1998), whereas for histidine, isoleucine, glutamate and serine they differed from those of the cited studies. The higher lysine proportion in the LAB than in the SAB observed in the present study is in contrast to that reported by Chiquette & Benchaar (1998), Volden & Harstad (1998). Nevertheless, both feeding level (Volden & Harstad, 1998) and diet composition (Martin et al, 1996;Chiquette and Benchaar, 1998) have been reported to affect bacterial AA proportions and may thus explain Table 1.…”

“…In the study of Volden & Harstad (1998), the addition of formaldehyde to ruminal samples prior to bacterial isolation showed a marked effect on both AA content and profile and was therefore avoided in the present study.…”

“…The SAB had a higher (PB 0.05) proportion of arginine, isoleucine, leucine, methionine, cystine, phenylalanine and proline, whereas the proportion of histidine, lysine, threonine, aspartate, glycine, alanine, serine and DAPA was higher (PB 0.05) in the LAB. Only a few comparisons of AA profiles have been made between LAB and SAB: Martin et al (1996), Chiquette & Benchaar (1998), Volden & Harstad (1998) using dry cows, dairy heifers and lactating dairy cows, respectively. In general, rather good agreements were shown between the results observed in these studies and those observed in the present investigation.…”

“…Nevertheless, very few comparisons of the relative AA composition of LAB and SAB on the one hand, and between LAP and the bacterial fractions on the other hand, are available in the literature, especially in lactating dairy cows. Clark et al (1992) compiled results of different experiments and concluded that some of the differences in bacterial AA content and composition were related to dietary effects, and Volden & Harstad (1998) observed an increased concentration of AA in *Corresponding author bacterial organic matter (OM) when the level of degradable protein in the diet was increased.…”