Supplementation With Phytogenic Compounds Modulates Salivation and Salivary Physico-Chemical Composition in Cattle Fed a High-Concentrate Diet

Abstract

Saliva facilitates feed ingestion, nutrient circulation, and represents an important pH buffer for ruminants, especially for cattle fed high-concentrate diets that promote rumen acidification. This experiment evaluated the short-term effects of nine phytogenic compounds on salivation, saliva physico-chemical composition as well as ingested feed boli characteristics in cattle. A total of nine ruminally cannulated Holstein cows were used. Each compound was tested in four of these cows as part of a high-concentrate meal (2.5 kg of total mixed ration in dry matter basis for 4 h) in low or high dose, and was compared to a control meal without compound. Saliva was sampled orally (unstimulated saliva) for physico-chemical composition analysis. Composition of the ingested saliva (stimulated saliva), salivation and feed boli characteristics were assessed from ingesta collected at the cardia during the first 30 min of the meal. Analysis of unstimulated saliva showed that supplementation with capsaicin and thyme oil increased buffer capacity, while supplementation with thymol, L-menthol and gentian root decreased saliva pH. In addition, supplementing angelica root decreased saliva osmolality. Regression analysis on unstimulated saliva showed negative associations between mucins and bicarbonate as well as with phosphate when garlic oil, thyme oil or angelica root was supplemented. Analysis of stimulated saliva demonstrated that supplementation with garlic oil increased phosphate concentration, thyme oil tended to increase osmolality, capsaicin and thymol increased buffer capacity, and ginger increased phosphate content. Furthermore, salivation rate increased with ginger and thymol, and tended to increase with garlic oil, capsaicin, L-menthol and mint oil. Feed ensalivation increased with capsaicin. A positive association was found between feed bolus size and salivation rate when any of the phytogenic compounds was supplemented. Overall, our results demonstrate positive short-term effects of several phytogenic compounds on unstimulated and stimulated saliva physico-chemical properties, salivation or feed boli characteristics. Thus, the phytogenic compounds enhancing salivary physico-chemical composition have the potential to contribute to maintain or improve ruminal health in cattle fed concentrate-rich rations.

Keywords: cattle; high-concentrate; phytogenic compound; saliva composition; salivation.

FIGURE 1

Schematic illustration of the sampling procedure timeline. (A) Unstimulated saliva was collected from the mouth, then the rumen was partially emptied. (B) The cows were offered the controlled meal with phytogenic compounds or control. Feed boli sampling from the cardia (collection of stimulated saliva) was performed over the first 30 min of the meal, with 2 min for collection alternated with 5 min of rest. (C) Unstimulated saliva sampling, and end of the 4-h meal.

FIGURE 2

Regression plots illustrating the associations between mucin concentration and bicarbonate (⚫), and phosphate (-○-) in the unstimulated salivary secretions of cattle, plots include average values across angelica root, garlic oil, and thyme oil.

FIGURE 3

Regression plots showing the association between stimulated salivary pH of cows and chewing index during the meal (A), plot includes the averaged values of capsaicin and thyme oil, and the association between stimulated salivary pH and feed ensalivation (B), plot includes the averaged values of capsaicin, garlic oil, gentian root, and mint oil.

FIGURE 4

The influence of feed bolus weight on the salivation rate in cattle fed concentrate-rich diets, plot includes values across all nine phytogenic compounds.