Abstract
Subacute ruminal acidosis (SARA) represents one of the most important nutritional disorders in high-producing dairy farms. The determination of ruminal pH is a key factor for the diagnosis of SARA. However, measuring ruminal pH in the field is not practicable. Therefore, indicators that reflect the ruminal pH are in demand. The main objective of this study was to examine the relationship between the milk fat-to-protein ratio (FPR) and ruminal pH parameters (daily mean pH, daily time with pH < 5.8, and pH range) on a meta-analytical level including 47 studies with 189 treatment means. Besides the FPR, it was examined how a stepwise extension of further indicators (milk yield, rumination time, and dietary starch and structure effectiveness) can improve the prediction of ruminal pH parameters. Significant associations between milk FPR and ruminal pH parameters were found. The inclusion of further on-farm indicators improved the prediction of daily mean ruminal pH up to Rm2 = 0.46 and time with pH < 5.8 up to Rm2=0.58. Still, a considerable part of variability was explained by the random factor study. Additional information (dietary PUFA content) may improve the models in further investigations.
Highlights
Subacute ruminal acidosis (SARA) represents a relevant problem in dairy cattle husbandry and nutrition
The inclusion of further on-farm indicators improved the prediction of daily mean ruminal pH up to R2m = 0.46 and time with pH < 5.8 up to R2m = 0.58
Friesian cows with a milk yield of kg under trial conditions of fat-to-protein ratio (FPR) as a good SARA indicator
Summary
Subacute ruminal acidosis (SARA) represents a relevant problem in dairy cattle husbandry and nutrition. Reports on its frequency described its prevalence to be between 8% and 29% [1] and recent field studies classified 42% to 44% of tested dairy farms in Poland and Germany as SARA positive [2,3]. Described that both a daily mean ruminal pH lower than 6.16 and a period of more than 5.24 h per day with a ruminal pH lower than 5.8 should be avoided to exclude the risk of SARA These limits have been adopted as official feeding recommendations in Germany [9]. Besides a lower absolute pH, increased diurnal ranges from 0.9 to 1.1 pH units where observed when the offered daily amount of grain was raised from 50% to 70% [11]
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