Rumination behavior as a predictor for subacute ruminal acidosis (SARA)? The effect of ruminal pH on rumination behavior

Abstract

Objective – The aim of this study was to investigate the effect of ruminal pH on the cows’ rumination behavior, in order explore if rumination behavior could be used as a tool to predict subacute ruminal acidosis (SARA). Animals - 4 multiparous rumen-cannulated Holstein Friesian dairy cows Procedures – Cows were divided into two groups and the experiment was carried out as a cross-over design, containing two periods of 4 weeks. In weeks 1, 2, 5 and 6 cows were fed the control ration (CON) and in weeks 3 and 7 there was a transition from the control ration to the experimental ration. During the fourth and the last week the cows were fed the experimental ration (SPK of FOR). The SPK ration contains a rapidly fermentable carbohydrate as concentrate and in the FOR ration the total part of forage is reduced. Ruminal pH, DMI and rumination behavior were measured continuously, except for the first and the fifth week. Results – SARA was induced for more days when feeding the FOR ration compared to feeding the SPK ration. Feeding the FOR ration resulted in a higher DMI (23.0 vs 19.8 kg/day), a lower mean ruminal pH (5.86 vs 6.24) and a longer period of experiencing a ruminal pH lower than 6.0 (926 vs 301 minutes/day) and 5.8 (625 vs 169 minutes/day) compared to the SPK ration (P<0.05). However, rumination time (490 vs 503 minutes/day), rumination time per kg DMI (20.3 vs 25.7 minutes) and experiencing a ruminal pH lower than 5.5 (235 vs 77 minutes/day) did not differ significantly between the FOR and the SPK ration (P>0.05). The overall correlations between rumination time and mean ruminal pH, time ruminal pH was below 5.8 and 5.5 were low (R2=0.17, R2=0.17 and R2=0.39 respectively). However, the FOR ration had higher correlations compared to the SPK ration (R2=0.68; R2=0.74; R2=0.69 and R2=0.37; R2=0.32; R2=0.27 respectively). All correlations were significant (P<0.05).