Modulation of chewing behavior and reticular pH in nonlactating cows challenged with concentrate-rich diets supplemented with phytogenic compounds and autolyzed yeast.

Feeding of concentrate-rich diets impairs chewing behavior and leads to rumen acidosis in cattle. Because of their modulatory effects on ruminal fermentation, phytogenic compounds (PHY) and autolyzed yeast derivatives (AY) may alleviate the negative consequences of high-concentrate diets. Therefore, this research investigated if chewing behavior and the reticular pH dynamics are modulated by AY and PHY supplementation during repeated concentrate-rich challenges used to simulate intermittent rumen acidotic insults. Eight rumen-cannulated, dry, and nonpregnant Holstein cows were assigned to an incomplete double 4 × 3 Latin square design with 3 treatments and 4 experimental runs (n = 8/treatment). Cows were fed concentrates either not supplemented (CON) or supplemented with PHY or AY. Initially, cows were fed a pure forage diet (FD) and switched to a 65% concentrate diet on DM basis for 1 (CONC 1) and 2 (CONC 2) wk. Between CONC 1 and CONC 2, the cows were fed the FD for 1 wk. Chewing activity was measured using noseband sensors and reticular pH by wireless pH sensors. Data showed that cows spent less time ruminating in CONC 1 than in CONC 2. In agreement, reticular pH drop was more pronounced during CONC 1 than during CONC 2. Cows fed with PHY spent 4 h less with reticular pH <6.0 during CONC 1 and 3 h less with pH <6.0 h in CONC 2 as compared with CON cows. Similarly, PHY supplementation extended rumination time with 88 min/d compared with CON cows during CONC 1. The AY supplementation increased DMI by 20% resulting in a longer eating time compared with CON diet during CONC 1. Enhancement of ruminating by PHY and eating time by AY supplementation resulted in longer total chewing time for PHY (474 min/d) and AY (466 min/d) as compared with CON (356 min/d) in CONC 1. In conclusion, cows experiencing 2 intermittent concentrate-rich challenges increased their ruminating behavior during the second challenge, and this effect was associated with higher reticular pH readings. The PHY supplementation enhanced rumination as well as reticular pH during CONC 1. However, the enhanced pH of cows fed with PHY during CONC 2 was not related to greater rumination, suggesting that influencing factors beyond rumination seemed to play a role in modulating reticular pH in PHY cows during CONC 2. The AY supplementation increased DMI without depressing rumination or reticular pH. Effects of both feed additives were more pronounced during CONC 1 challenge when reticular pH was lower.

Technical note: A comparison of reticular and ruminal pH monitored continuously with 2 measurement systems at different weeks of early lactation.

Subacute ruminal acidosis is one of the most important digestive disorders in high-yielding dairy cows fed highly fermentable diets. Monitoring of forestomach pH has been suggested as a potentially valuable tool for diagnosing subacute ruminal acidosis. The objective of the present study was to compare continuously recorded measurements of an indwelling telemetric pH sensor inserted orally in the reticulum with those obtained from a measurement system placed in the ventral sac of the rumen through a cannula. The experiment was conducted with 6 ruminally cannulated Holstein cows kept in a freestall barn. Equal numbers of cows were assigned to 2 treatment groups based on their previous lactation milk yield. Cows in treatment CON- were offered a diet consisting of only fresh herbage cut once daily, and cows in treatment CON+ got fresh herbage plus a concentrate supplement according to the individual milk yield of each cow to meet their predicted nutrient requirements. The experiment lasted from 2 wk before the predicted calving date until wk 8 of lactation. During the whole experiment, a pH value was recorded every 10 min in the reticulum using a wireless telemetry bolus including a pH sensor (eBolus, eCow Ltd., Exeter, Devon, UK), which had been applied orally using a balling gun. Simultaneously, in wk 2, before the estimated calving date and in wk 2, 4, 6, and 8 of lactation, the ruminal pH was measured every 30 s for 48 h with the LRCpH measurement system (Dascor Inc., Escondido, CA) placed in the ventral sac of the rumen through the cannula. The readings of the LRCpH measurement system were summarized as an average over 10 min for statistical analysis. The recorded pH values were on average 0.24 pH units higher in the reticulum than in the rumen. The reticular pH also showed less fluctuation (overall SD 0.19 pH units) than pH profiles recorded in the rumen (overall SD 0.51 pH units). Regardless of measurement system, pH was not influenced by treatment, but varied across week of lactation and decreased with advancing lactation. The difference between ruminal and reticular pH varied across week of lactation. Due to this variation, no fixed conversion factor can be provided to make pH measurements in the reticulum comparable with those in the rumen.

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

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.

Diagnosis of subacute ruminal acidosis (SARA) by continuous reticular pH measurements in cows.

The objective of this study was to determine whether subacute ruminal acidosis (SARA) could be diagnosed by continuous measurements of the reticular pH, as compared with the ruminal pH, using healthy cows fed a control diet and SARA cows fed a rumen acidosis-inducing diet. The reticular and ruminal pH were measured simultaneously by a radio transmission pH measurement system. The mean reticular pH at 1-h intervals decreased gradually from the morning feeding to the next feeding time in both healthy and SARA cows, though the decrease in the ruminal pH was observed to be more drastic as compared with that observed in the reticular pH. The threshold of the 1-h mean pH in the reticulum for a diagnosis of SARA was considered to be 6.3, and a significant positive correlation was observed between the reticular and ruminal pH. No differences in the concentrations of lactic acid, ammonia nitrogen, and volatile fatty acids were noted between the reticular and ruminal fluids in SARA cows. These results demonstrate that the reticular pH can be used to detect SARA in cows, as opposed to using the ruminal pH.

Structural, histochemical and immunocytochemical study of the forestomach mucosa in domestic ruminants.

The forestomach plays an important role in the digestion physiology of ruminants. The aim of this study is to clarify the morpho-functional role of the mucosa in each of the three compartments of the forestomach in three domestic ruminants species, viz cattle, buffalo and sheep, by means of structural, histochemical and immunocytochemical methods, including transmission electron microscopy, light microscopy and scanning electron microscopy. These methods were chosen to demonstrate the indirect evidence for the presence of nitric oxide (NO) employing NADPHd and nitric oxide synthase I (NOS I). The various cell layers of the forestomach epithelium are described and illustrated in detail. An intense NADPHd staining was observed in the granulosa, spinosa and basal layers of the epithelium, in particular in the cytoplasm over the nucleus. NOS I immunoreactivity was found in all specimens of the forestomach mucosa. The results of this study might reflect a possible role of NO in delaying the onset of cellular apoptosis in the forestomach mucosa of the domestic ruminants, by playing a role in the production of cell energy.

Morphometric and immunohistochemical study of the reticulum of red deer during prenatal development.

Iberian red deer need to be conserved for their economic role and for their genetic importance as an important component of the ecosystem. Modifications currently being made to traditional management systems require a better understanding of the structure, function and development of their alimentary system. Here we describe a histomorphometric and immunohistochemical analysis of the stomach of 25 red deer embryos and fetuses from 30 days of gestation until birth (235 days). Differentiation of the reticular compartment from the primitive gastric tube begins at 67 days, forming a three-layered structure: epithelium, pluripotential blastemal tissue and serosa. The primitive reticular cells are initiated as small epithelial evaginations (primary ribs) at 117 days. At 142 days, lateral growths appear from the primary reticular ribs, forming the corneum papillae. The secondary reticular ribs form at 142 days as growths from the primary ribs. The uneven height of primary and secondary reticular ribs leads to the formation of cells of varying size. Growth of the reticular ribs involves the lamina propria but not the submucosa, so clear separation of these layers is maintained during histodifferentiation. Formation of the tunica muscularis from the pluripotential blastemal tissue begins at 67 days of intrauterine life, as two layers of longitudinally and circularly arranged myoblasts. Differentiation of the muscularis from the mucosa occurs at approximately 205 days, as longitudinal projections of the internal bundles of the tunica muscularis form the musculature of the primary ribs. The secretion of neutral and acid mucopolysaccharides by the reticular epithelial layer begins at 67 days, establishing the gradual adaptation of the mucosa to its protective function in postnatal life. Neuroendocrine (non-neuron enolase) and glial cells (glial fibrillary acidic protein and vimentin) were detected by immunohistochemistry, in a similar localization and intensity to that reported in the rumen. The neuropeptides vasoactive intestinal peptide and neuropeptide Y showed a positive immunoreaction in the reticular epithelium from 142 days of prenatal life, again earlier than reported for the rumen. In comparison with domestic ruminants, deer were shown to be less precocious with regard to development of gastric tube, in their capacity to secrete neutral mucopolysaccharides, and in their neuroendocrine nature, as determined by the detection of positive neuroendocrine and/or glial cells.

[Comparative ontogenic analysis of the epithelium of the non-glandular stomach compartments of merino sheep]. / Estudio ontogenico comparativo de la lamina epitelial de los compartimentos gastricos no glandulares en ovinos merinos.

A total of 74 embryos and fetuses were used in a comparative analysis of the epithelium of the non-glandular stomach compartments of merino sheep during development. The mechanical protection showed by the tegumentary epithelium in the superficial layers of the rumen, reticulum and omasum is supported by a buffer system of neutral mucopolysaccharides secreted by the deeper strata. Neutral mucopolysaccharides first appeared in epithelial cells at 46 days of fetal life. Acid mucopolysaccharides, mucins, and mucoid compounds were not detected. Growth curves and formulas were constructed for the epithelial layers.

Physical characteristics of reticular content in the bovine and consequences on reticular outflow.

Reticular content was sampled in cows before and 2 and 5 hours after they were fed various forages. Dry matter, particle size distribution, pH, osmotic pressure and viscosity of the liquid phase were measured. Consistency was also evaluated using purpose-built apparatus. The contents were fractionated by vertical distribution under gravity and by intermittent flow through an orifice into fractions containing different particle concentrations, to model reticular retention of large particles in rumen outflow. Retention occurs as a result of a combination of flotation carrying large particles back into the rumen, and filtration which prevents them leaving it. These processes are particularly effective after feeding, and with poor hay, and so help prolong fermentation time. The consistency of reticular content is relatively stable; it may be autoregulated by adjustment of feeding parameters in response to sensory receptor signals.

A technique for the collection of reticular effluent of sheep.

Two sheep were equipped with rumen and omasal fistulae. A teflon tube with 1 mm outer diameter (OD) was permanently fixed between the abomasal fistula and the reticulo-omasal orifice. The effluent sampling tube was introduced through the abomasal cannula, through the omasal canal into the reticulo-omasal orifice by aid of the teflon tube. The technique allowed direct collection of reticular effluent from sheep. Intermittent flow of reticular effluent was observed. The moments of flow coincided with the end of the second phase of reticular contractions. From the flow pattern it was concluded that the motility of the reticulo-omasal orifice was not affected by the sampling procedure. From the similarities in the pH values, DM contents, and total protozoal counts in the effluent and in the reticular samples, it was concluded that representative samples of effluent could be obtained by the method. One animal was used for sampling for a period of eight months and then again 2 1/2 years later. A fraction of 97 to 98% of the DM present in the reticular effluent and in the reticular samples passed a sieve with 1 mm pore size. From the analyses of reticular content and reticular effluent it was concluded that the reticulo-omasal orifice does not have a significant discriminating function for the selective passage of particles and protozoa into the omasum.