SUMMARYAn in vitro study was conducted to investigate the effects of condensed tannin (CT) structural properties, i.e. average polymer size (or mean degree of polymerization), percentage of cis flavan-3-ols and percentage of prodelphinidins in CT extracts on methane (CH4) production and fermentation characteristics. Condensed tannins were extracted from eight plants in order to obtain different CT types: blackcurrant leaves, goat willow leaves, goat willow twigs, pine bark, redcurrant leaves, sainfoin plants, weeping willow catkins and white clover flowers. They were analysed for CT content and CT composition by thiolytic degradation, followed by high performance liquid chromatography (HPLC) analysis. Grass silage was used as a control substrate. Condensed tannins were added to the substrate at a concentration of 40 g/kg, with or without polyethylene glycol (+ or −PEG 6000 treatment) to inactivate tannins, then incubated for 72 h in mixed buffered rumen fluid from three different lactating dairy cows per run. Total cumulative gas production (GP) was measured by an automated GP system. During the incubation, 12 gas samples (10 µl) were collected from each bottle headspace at 0, 2, 4, 6, 8, 12, 24, 30, 36, 48, 56 and 72 h of incubation and analysed for CH4. A modified Michaelis-Menten model was fitted to the CH4 concentration patterns and model estimates were used to calculate total cumulative CH4 production (GPCH4). Total cumulative GP and GPCH4 curves were fitted using biphasic and monophasic modified Michaelis-Menten models, respectively. Addition of PEG increased GP, GPCH4, and CH4 concentration compared with the −PEG treatment. All CT types reduced GPCH4 and CH4 concentration. All CT increased the half time of GP and GPCH4. Moreover, all CT decreased the maximum rate of fermentation for GPCH4 and rate of substrate degradation. The correlation between CT structure and GPCH4 and fermentation characteristics showed that the proportion of prodelphinidins within CT had the largest effect on fermentation characteristics, followed by average polymer size and percentage of cis flavan-3-ols.
Functional nutrients that facilitate gastrointestinal health may serve as an alternative to the use of antimicrobials in animal production systems. Gluconic acid has been used as a prebiotic health promoter in non-ruminant applications. It is poorly absorbed in the small intestine and is fermented to butyrate in the lower gastrointestinal tract. The gut health benefits of butyrate have been demonstrated in both non-ruminant and ruminant models, but effects of post-ruminal gluconic acid supplementation are not well described. The objective of this study was to determine the effects of calcium gluconate embedded in a fat matrix (CGFM; 40% CaGlu) on dry matter intake, blood metabolites, milk production and fecal short chain fatty acid (SCFA) production in early lactation dairy cows (21 ± 2 DIM) fed to 100% of energy and protein requirements. The experiment was a 3 x 3 replicated Latin square with 13 replicates (3 cows/replicate), 3 experimental periods (each 28 d) and 3 dietary treatments of control (0 g/d), 16 g/d and 25 g/d of CGFM. There was no treatment effect on DMI and milk yield. The relationship between dose of CGFM (i.e. 0, 16, 26 g/d) and milk fat and protein yield, energy corrected milk was significantly quadratic (P < 0.05) while feed efficiency tended to be quadratic (P = 0.08). The greatest response was in milk fat yield, which increased 90 g/d over control at 16 g/d of CGFM. No significant changes in blood metabolite concentrations or fecal SCFA concentrations were observed between treatments, although there was a numerical increase in non-esterified fatty acid concentration in response to the 16 g/d CGFM dose (P = 0.16). The response to supplementation of fat-embedded calcium gluconate appears to alter energy partitioning in the lactating dairy cow, as demonstrated with subtle changes in circulating lipid and increased fat yield.
This research communication reports the responses to supplementing dairy cattle with a hydrogenated fat-embedded calcium gluconate feed additive. The role of hindgut health in ruminant performance and wellbeing is an area of growing interest. Various prebiotic compounds have been used to promote lower gut health in various non-ruminant species. Calcium gluconate, a prebiotic compound, has previously been observed to increase milk fat yield when fed to ruminants in a form capable of resisting fermentation in the rumen, though the mechanism(s) behind this response remain unclear. The objective of this study was to compare the responses of lactating cattle to two different supplementation levels of a hydrogenated fat-embedded calcium gluconate (HFCG) product to evaluate a potential linear dose response. Forty-six lactating Holstein dairy cattle were used in a 3 × 3 replicated Latin square design with 28 d periods to evaluate a previously used dose of HFCG (approximately 16 g/d) with both a negative control and a dose of 25 g/d. Supplementation of multiparous animals with 16 g/d HFCG significantly (P < 0.05) increased milk fat yield and content relative to the negative control, and subsequently improved gross feed efficiency (P < 0.05); additionally, the presence of a potential non-linear dose response was observed for these parameters. Responses when supplemented with 25 g/d HFCG did not differ from the negative control. No production responses were observed in primiparous animals. The mode of action of HFCG, in addition to the potential differential response in primiparous animals remains unclear and warrants further investigation.
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