Quantifying subclinical ruminal drinking using a [13C]-[15N2]-urea based method in veal calves

Abstract

Ruminal drinking (RD) occurs in calves when ingested milk or milk replacer enters the reticulorumen instead of the abomasum, and can be caused by a failure of the reticular groove reflex or by backflow of milk replacer (MR) from the abomasum. In a clinical case, RD often results in chronic maldigestion (Stocker et al., 1999), ruminal acidosis, lack of appetite and recurrent bloat (Van Weeren-Keverling Buisman et al., 1990), and consequently a reduced growth rate. Although clinical cases of RD have been described extensively (Herrli-Gygi et al., 2006; Gentile et al., 2004; Van Weeren-Keverling Buisman et al., 1990), data on subclinical RD are scarce, partly due to methodological issues. Recent studies have shown that subclinical RD can be substantial in veal calves. Between 21 and 35% of an orally supplied dose of Co-EDTA was recovered in the rumen at slaughter (Suarez et al., 2007; Berends et al., 2012). Assuming that nutrients from MR are subject to fermentation in the rumen, subclinical RD may reduce post-absorptive availability of nutrients and result in lower growth rates in calves. Nonetheless, it is unknown if RD is constant over time (i.e. between meals or days), and measuring recovery at slaughter does not allow repetitive measurements within one animal. Among others, solid feed (SF) provision to veal calves may alter the reticular groove reflex and thus RD. In order to study subclinical RD and related factors, there is a need for a method to quantify RD that does not require calves to be sacrificed. In this study such a method was developed and applied to assess the effect of SF intake on RD.