Responsive changes of rumen microbiome and metabolome in dairy cows with different susceptibility to subacute ruminal acidosis

The present study was aimed at comparing the milk urea nitrogen (MUN) and milk fatty acid (MFA) compositions in Holstein cows with subacute ruminal acidosis (SARA) to those values of Holstein cows that did not have SARA. Also, the correlations among rumen pH value and the compositions of MUN and MFA in milk were determined. Dairy cows (n = 16) with subacute ruminal acidosis (SARA) (pH value 5.60 ± 0.02) and control dairy cows (n = 16) (control) (pH value 6.20 ± 0.04) were studied. The MUN concentrations (578 µg/l) of the dairy cows with SARA was lower than those (1 315 µg/l) of the control dairy cows (P < 0.001). In the milk of the dairy cows with SARA, the unsaturated fatty acids (UFA), thrombogenic index (TI), and hypocholesterolemic fatty acid index (hcFA) decreased; but the saturated fatty acids (SFA), atherogenic (AI) and hypercholesterolemic fatty acid (HcFA) indexes (P < 0.01) increased. The rumen pH value and the concentration of the MUN were positively correlated with the proportions of the monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), omega-3 fatty acids (n-3), omega-6 fatty acids (n-6), omega-9 fatty acids (n-9), long-chain fatty acids (LCFA) and very-long-chain fatty acids (VLCFA) and the n-3/n-6 ratio of the milk samples (P < 0.05). Consequently, the dairy cow with SARA that are in early-lactation can affect the carbohydrate fermentation, fatty acid hydrogenation and protein degradation. The MUN concentration in the dairy cows with SARA seriously decreased. The SARA changes the milk fatty acid composition and decreases the MUFA, PUFA, n-3, oleic acid and hypocholesterolemic fatty acids and the hypocholesterolemic/hypercholesterolemic ratio (h/H) values of milk. Therefore, the nutritional and functional quality for human nutrition decreases in the milk of dairy cows with SARA.

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Subacute ruminal acidosis in dairy cows - physiological background, risk factors and diagnostic methods

Veterinarska stanica ◽

10.46419/vs.51.1.1 ◽

2020 ◽

Vol 51 (1) ◽

pp. 5-17

Author(s):

Levente Kovács ◽

Otto Szenci ◽

Walter Baumgartner ◽

Mátyás Hejel ◽

László Rózsa

Keyword(s):

Risk Factors ◽

Dairy Cows ◽

Continuous Measurement ◽

Clinical Signs ◽

The United States ◽

Diagnostic Methods ◽

Subacute Ruminal Acidosis ◽

Field Techniques ◽

Ruminal Ph ◽

Ruminal Acidosis

According to the latest studies, the prevalence of subacute ruminal acidosis (SARA) is around 20% in early and mid- lactation dairy cows, generating annual losses in the United States of approximately USD 500 million to 1 billion. The diagnosis of SARA is still difficult due to lack of pathognomonic clues and the delayed appearance of certain clinical signs. Therefore, SARA remains neglected or even unrecognized in many dairy herds. SARA is characterized by daily episodes of low ruminal pH, when the pH remains in the range of 5.2 to 6 for a prolonged period due to the accumulation of short-chain fatty acids and insufficient rumen buffering. The causes of SARA are related to high-grain diets, such as feeding excessive amounts of non-structural carbohydrates and highly fermentable forages, and insufficient dietary coarse fibre. SARA is associated with the inflammation of several organs and tissues in dairy cows, and its main long-term health and economic consequences are the fluctuation of feed intake, reduced fibre digestion, depression of milk yield and milk fat content, gastrointestinal damage, diarrhoea, laminitis, liver abscesses, and lameness. The aim of this review is to summarize the information available on the physiological aspects, risk factors, prevalence and possible indicators of SARA in dairy cattle. Basedon the existing literature, rumenocentesis and the use of an oral stomach tube are reliable field techniques to detect SARA. Nowadays, improved field techniques allowing the continuous measurement of reticuloruminal pH are also available for better diagnosis of SARA. Wireless indwelling pH probes may become important tools for the continuous measurement of ruminal pH in the coming years.

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