Abstract
Tannins have been used to trigger positive effects on ruminal metabolism and increase ruminant production efficiency, since they increase the supply of dietary protein in the small intestine. Increasing levels of tannic acid in a sorghum-based diet on the feeding behavior of five Holstein/Zebu crossbred lactating dairy cows was evaluated. They were subjected to a 5 × 5 Latin square experimental design, with fivelevels of tannin as dry matter (DM) in the diet (0.46, 1.30, 2.60, 3.90, and 5.20%). The levels of the tannic acid added were established based on the quantity of condensed tannin in high-tannin sorghum. Thus, diets 2, 3, 4 and 5 were supplemented with 1.5 g (13% DM), 79.5 g (2.6% DM), 157.5 g (3.9% DM), and 235.5 g (5.2% DM) of tannic acid, totaling 0.078, 0.156, 0.234, and 0.321 kg of tannin/day, respectively. Feeding behavior variables included the following states and events: feeding, drinking, rumination, and inactivity; the frequency of visiting the feed and water troughs; and the occurrence of urination and defecation. Water was provided ad libitum, and its intake was measured during periods of behavioral data collection. The use of two tannin sources (hydrolysable and condensed) corresponding to the total level of 5.20% (on a DM basis) in the diet of lactating dairy cattle does not affect the animals’ health. Tannic acid can be included in the diet of lactating dairy cattle at a level of 3.93% (on a DM basis) without inducing variation in the total time spent daily on feed intake. Dairy cows dilute the effects of dietary tannin (5.20%) through greater fragmentation of food consumption in the hours following its supply (180 min). The astringent effects caused by tannin intake in lactating dairy cows are mitigated by increasing the daily water intake as the amount of tannin in the diet increases, starting at a level of 3.90% tannin (on a DM basis).
Highlights
The use of tannin in ruminant nutrition is increasing, mainly due to its diverse positive effects in several aspects concerning physiology, metabolism, and animal performance.research results are quite controversial regarding the concentrations and sources used, which reinforces the need for further studies to elucidate these still evident gaps.According to Haslam and Lilley [1], tannins represent secondary compounds of plants and are present in many species that are commonly consumed by ruminants
The results of the present study showed that no variation existed in the total daily feed intake of dairy cows based on the tannin levels measured in their diets
To deal with the intake of tannins, ruminant animals establish different behavioral strategies that are associated with different tannin levels and sources in the diet
Summary
According to Haslam and Lilley [1], tannins represent secondary compounds of plants and are present in many species that are commonly consumed by ruminants. They are generally defined as water-soluble polymeric phenolics that precipitate proteins, and are classified into hydrolysable and condensed tannins. The effects of tannin can start even before its action at deeper levels in the organisms; that is, once present in the animal’s mouth it can cause changes in its feeding behavior; the astringency caused by the consumption of these phenolic compounds exerts short-term effects in an animal’s mouth that can be felt immediately upon ingestion [2,3]. The selection of the food to compose an animal’s diet depends significantly on its acceptability and its post-ingestion effects
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