A comparison of ruminal or reticular digesta sampling as an alternative to sampling from the omasum of lactating dairy cows

Abstract

The objective of this study was to develop and compare techniques for determining nutrient flow based on digesta samples collected from the reticulum or rumen of lactating dairy cows with estimates generated by the omasal sampling technique. Pre-experimental method development suggested, after comparing with the particle size distribution of feces, application of primary sieving of ruminal and reticular digesta from lactating cows through an 11.6-mm sieve, implying that digesta particles smaller than this were eligible to flow out of the rumen. For flow measurements at the different sampling sites 4 multiparous, lactating Nordic Red cows fitted with ruminal cannulas were used in a Latin square design with 4 dietary treatments, in which crimped barley was replaced with 3 incremental levels of protein supplementation of canola meal. Digesta was collected from the rumen, reticulum, and omasum to represent a 24-h feeding cycle. Nutrient flow was calculated using the reconstitution system based on Cr, Yb, and indigestible neutral detergent fiber and using (15)N as microbial marker. Large and small particles and the fluid phase were recovered from digesta collected at all sampling sites. Bacterial samples were isolated from the digesta collected from the omasum. Several differences existed for digesta composition, nutrient flows, and estimates of ruminal digestibility among the 3 different sampling sites. Sampling site × diet interactions were not significant. The estimated flows of DM, potentially digestible neutral detergent fiber, nonammonia N, and microbial N were significantly different between all sampling sites. However, the difference between DM flow based on sampling from the reticulum and the omasum was small (0.13kg/d greater in the omasum). The equality between the reticulum and the omasum as sampling sites was supported by the following regression: omasal DM flow=0.37 (±0.649) + 0.94 (±0.054) reticular DM flow (R(2)=0.96 and root mean square error=0.438kg/d). More deviating nutrient-flow estimates when sampling digesta from the rumen than the reticulum compared with the omasum suggested that sampling from the reticulum is the most promising alternative to the omasal sampling technique. To definitively promote sampling from the reticulum as an alternative to the omasal sampling technique, more research is needed to determine selection criteria of reticular digesta for accurate and precise flow estimates across a range of diets.

Invited review: Nitrogen in ruminant nutrition: A review of measurement techniques

“…Ruminal digestibility of CP was higher based on reticular sampling compared with the other 2 sites, which did not differ. Fatehi et al (2015) also compared reticular and omasal sampling and, additionally, rumen sampling (collected in the same manner as the reticular samples) and reported significantly higher flows of NAN and microbial NAN for rumen compared with reticular sampling, which, in turn, were higher than omasal sampling; no difference was found between methods for NANMN flow, and ruminal digestibility of NAN. Discrepancies across studies may be partly attributed to the method of digesta processing whereby it was sieved through a 1-mm screen to discard large particles in some studies, but not others (Fatehi et al, 2015).…”

“…Fatehi et al (2015) also compared reticular and omasal sampling and, additionally, rumen sampling (collected in the same manner as the reticular samples) and reported significantly higher flows of NAN and microbial NAN for rumen compared with reticular sampling, which, in turn, were higher than omasal sampling; no difference was found between methods for NANMN flow, and ruminal digestibility of NAN. Discrepancies across studies may be partly attributed to the method of digesta processing whereby it was sieved through a 1-mm screen to discard large particles in some studies, but not others (Fatehi et al, 2015). As with omasal sampling, reticular sampling avoids the necessity for overly invasive cannulation and interference from abomasal degradation and endogenous N secretions, but it has less interference with the animal's DMI and does not need elaboration of sampling equipment or the insertion of a sampling device through the reticulo-omasal orifice (Krizsan et al, 2010b).…”

Ruminal microorganism consideration and protein used in the metabolism of the ruminants: A review

“…Maximizing the microbial protein synthesis and pass their flow for duodenum (Argyle and Baldwin, 1989;Fatehi et al, 2015).…”

Probiotic Supplement Improves the Health Status and Lactation Performance in Dairy Animals

“…The rumen is a complex biological system which is like a fermentative vat where nutrients are consumed by different organisms. Energy from forages are acquired by ruminants through fermentation process which is done by microorganisms by different enzymatic activities [24]. Different factors including pH, temperature, osmotic pressure, buffering capacity, and redox potential affect the activity and growth of rumen microorganisms [25].…”