Effects of varying proportions of concentrates on ruminal-reducing power and bacterial community structure in dry dairy cows fed hay-based diets

Abstract

The objectives of this study were to evaluate the influence of diet composition on ruminal parameters, more particularly redox potential (E h ). Four Holstein dry dairy cows, fitted with ruminal cannulas, were allocated in a 4 3 4 Latin square design. They were given four experimental hay-based diets D0, D25, D42 and D56 consisting of 0%, 25%, 42% and 56% of ground wheat and barley concentrate mixture, respectively. They were fed at a daily feeding rate of 8.0 kg DM per cow during a 24-day experimental period (a 21-day diet adaptation, three consecutive days of measurement and sampling). The physicochemical parameters, such as pH and E h , were measured and Clark's exponent (rH) was calculated from 1 h before feeding to 8 h after feeding at 1-h interval. Samples of ruminal fluid were taken at 0, 1, 2, 4, 6 and 8 h after feeding for the determination of volatile fatty acid (VFA) and ammonia N (NH 3 -N) concentrations. Ruminal bacterial populations were also studied by means of capillary electrophoresis singlestrand conformation polymorphism (CE-SSCP) technique to focus on the structure of the ruminal microbiota and the diversity index was calculated. Mean ruminal E h and rH were not modified by the concentrate-to-forage ratio and averaged -210 mV and 6.30, respectively, across diets. The pH decreased slightly by 0.10 pH unit between treatments D0 and D56 with an average of 6.58. Nevertheless, the time during which physicochemical parameters remained at nadir value after feeding varied with diets: 2 and 7 h for D0 and 6 and 5 h for D56, respectively for pH and E h . Moreover, fermentative parameters were altered by treatments: total VFA and NH 3 -N were greater in D56 (72.2 mM and 17.5 mg/100 ml) compared with D0 (65.2 mM and 14.2 mg/100 ml). However, neither the structure of bacterial populations of the rumen nor the diversity index (Shannon) was altered by treatments.

Interaction between Live Yeast and Dietary Rumen Degradable Protein Level: Effects on Diet Utilization in Early-Lactating Dairy Cows

“…These physico-chemical observations were to be compared with the microbiological data obtained for both diets: the molecular fingerprint of bacterial communities differed significantly by 29% between cows receiving LL and AL. Thus, present results put forward that the ruminal reducing status varies with the diet of animals as already observed by Monteils et al [42] and suggested by Julien et al [16] in dairy cows fed a fiber-or a starch-based diet.…”

“…Measurements of pH and redox potential (E h ) were realized over 3 consecutive days (d 15 to d 17 and d 27 to d 29) using the ex vivo method described by Julien et al [16]. For each cow, ruminal pH and E h were recorded hourly over a 9-h period from 1 h before to 8 h after the morning meal (T −1 to T +8 ).…”

Effect of concentrate supplementation on performance, ovarian response, and some biochemical profile of Malpura ewes

“…Ingredient composition of the concentrate mixture in the present study contained 97% barley. Barley is more fermentable in the rumen in comparison to other diets like corn (Granzin 2004;Lanzas et al 2007;Mohammed et al 2010) and therefore increased ruminal TVFA concentration (Khorasani et al 2001;Au et al 2010;Julien et al 2010) was observed. Higher concentration of TVFA production in group 2 is due to concentrate feeding, and this led to a decrease in ruminal pH both at 0 and 4 h of feeding concentrate.…”

Methodology Article: Can Ruminal Reducing Power Assessed in Batch Cultures be Comparable to <i>in Vivo</i> Measurements?

“…The pH and E h measurements were realized in vivo on the donor cows each hour from the morning meal (T0) to 8 h after (T8) by means of the method described by Julien et al [8], during the day immediately following each day of in vitro cultures. Ruminal fluid was sampled with 10% of HgCl 2 (2% wt/vol) at T0 and T8 for subsequent volatile fatty acids (VFA) determination.…”

“…In the rumen, some authors were interested in measuring E h to get a better insight in its factors of variation. So, ruminal E h tended to be 45 to 100 mV lower in ruminants fed a hay diet (70% to 100% of forage) than in those fed a concentrated diet (40% to 80% of concentrate) [6]- [8]. In cows, Julien et al [9] observed a relation between level of dry matter intake (DMI) and ruminal E h which could vary from −210 to −165 mV, for a low (8 kg of DMI) and high (21 kg) level of DMI respectively.…”