Gastrointestinal parasite infections are natural occurring components of pastoral grazing systems and many internal parasite species have developed resistance to anthelmintic drugs [1] . Gastrointestinal parasites infection cause major production losses in grazing cattle with the greatest reduction occurring in young growing cattle, which normally have limited immunity to nematode parasites [2] - [4] . Choosing yearling stocker cattle as an internal parasites infestation model allows the extension of our model to broad range of stocker cattle production systems in Southern US. Alternative anthelmintic chemistries are needed even in conventional systems because of increasing parasite resistance to contemporary synthetic anthelmintics [1] [5] .

Natural plant tannins have been documented to control intestinal parasites in ruminants [6] [7] . Molan et al. [8] [9] have shown that tannin extracted from forages had the ability to inhibit the larval motility and eggs hatching rate in vitro. Previous scientific reviews have shown that a threshold of at least 2% to 4% tannins per kg dry matter in diet has to be reached to observe anti-parasitic activity [6] [10] . It has been shown that condensed tannins (quebracho tannins; 40 g/kg body weight) was ineffective in sheep against the Trichinella spiralis nematode, whereas worm burdens of Nippostrongylus brasiliensis were significantly reduced [11] . However, the excess consumption of plant tannins extracts can be negatively affected host animals. Studies need to be carried out worldwide, to identify tannin compounds and the associated mechanisms of their mode of actions understood, in order to determine for their use in internal parasites control.

The benefits of tannins in the diets to affect digestion of tannins-free diets have facilitated research involving other dietary tannins compounds such as commercially available mimosa and chestnut tannins. We hypothesize commercially available plant tannin extracts would be effective in controlling internal parasites infestation and increasing average daily gain (ADG) in growing stocker cattle. The objectives of this study were to examine the animal performance, internal parasites, and blood metabolites effects of hydrolysable tannin-rich chestnut and condensed tannin-rich mimosa extracts applied as a feed additive to stocker cattle.

The most significant findings in this study were that heifers grazing winter wheat forage supplemented with plant tannins rather than control (non-tannins group) 8% to 19% increased ADG for mimosa and chestnut tannins groups, respectively with no discernable detrimental effects on blood chemistry or the esophagus. The increase in ADG may be due to decreases in both Cooperia and O. ostertagi fecal parasites infections. The significant reduction of FEC in both Cooperia and O. ostertagi after day 35 or 41 suggests that length of feeding time is required to give maximum response in internal parasites infestation.

Steers were grazed winter wheat forage during the 70 days with tannins supplementation. Animals were continues grazed on wheat forage after the cessation of tannins administration, and the last blood samples were taken 20 days thereafter. Alkaline phosphatase (ALP), liver, bone, parathyroid and intestinal disease; alanine aminotransferase (ALT), liver diseases including viral hepatitis, cirrhosis, and heart diseases; gamma glutamyl transferase (GGT), liver disease, primary and secondary liver tumors; bile acids (BA), hepatobiliary disease, portosystemic anomaly, and extraheptic; total bilirubin (TBIL), hepatic disorders; albumin, liver and kidney disease; blood urea nitrogen (BUN), liver and kidney disease; total cholesterol (CHOL). ^a,b,cNumbers in a row with superscript letters are significantly different (P < 0.05).

In the present study, both mimosa and chestnut tannins did not have inhibiting effect on H. contortus fecal egg output, but Cooperia and Ostertagia fecal egg output were reduced in heifers supplemented with both tannin extracts. When established adult nematodes were exposed to condensed tannins in sheep, a reduction in worm fecundity and worm numbers was observed for the intestinal species (Nematodirus battus and Trichostrongylus colubriformis), whereas no changes were recorded for the species that resides in the stomach and abomasums (Teladorsagia circumcincta and H. contortus; [14] ). It has been shown that dietary quebracho tannins (40 g/kg LW) was ineffective in sheep against the mucosal dewelling nematode, Trichinella spiralis, whereas worm burdens of Nippostrongylus brasiliensis, a lumen dweller, were significantly reduced [11] . It is possible that the effectiveness of plant tannin extracts against H. contortus may due to the short time period that the larvae were exposed to gut contents before embedding in the small intestinal mucosa, known to be <30 min [11] , indicating that direct contact between the tannins and the nematodes may be necessary in order to reduce worm burden or larval establishment in host animals. Conversely, Min et al. [7] reported that condensed tannins-containing Sericea lespedeza (15.2% condensed tannins) diet in goats reduced 89% of H. contortus population in the abomasums than those grazing non-tannins containing forage, indicating that possibility of direct or indirect mechanisms, increase protein supply and immune response against worms, contributing to the anthelmintic properties of different types of tannins cannot be discards.

Cooperia fecal eggs were reduced 8% to 13% by mimosa and chestnut tannins supplementation, respectively. While present study has shown that average Ostertagia fecal eggs production can be reduced by 57% on day 41 without use of anthelmintics when heifers received chestnut tannins as compared to a non-tannins containing diet. This reduction is an indication that plant tannins supplementation has an anthelmintic potential to control internal parasites in ruminants depending on sources of tannins and nematode species. Yamasaki et al. [15] reported that substantial toxic effects have been detected in the digestive and reproductive tracts of Caenorhabditis elegans worms after contact with hydrolysable ellagic tannins. Similar lesions and shrinkages of the cuticle surface of adult T. colubriformis after incubation in a chestnut extract (1.2 mg/ml) in phosphate buffer solution have been shown in in vitro [10] , indicating that plant tannins, especially hydrolysable tannins, could directly affect the cuticle surface of worms or change their physical and biological process. Plant tannins could act indirectly, by improving the response of the host to parasites. Few studies, however, have addressed this indirect hypothesis by measuring specifically local or general parameters related to host immunity, and the results remain fundamentally inconclusive.

There is strong evidence showing that an improved efficiency of protein digestion throughout tannins-con- taining forage diet, especially by-pass protein from the rumen, can result in an increased ADG and animal productivity [16] [17] . The importance of plant tannins and protein digestion was confirmed by Min et al. [7] [18] [19] , who found that 1.5% condensed tannins (quebracho) supplementation in steers grazing wheat forage increased ADG by 15%. Recently, Min et al. [18] - [20] found that cattle grazing high quality wheat forage and feeding plant tannins were associated with ADG, altered rumen metabolites and microbial populations [21] . Condensed tannins-containing forage diets in sheep have been previously shown to decrease proteolysis of high quality forage, but increased by-pass protein [16] [17] . It therefore seems possible that the increased supply of protein and reduced internal parasite infestation caused by the action of tannins could be used to increase animal production system in grazing cattle with minimum anthelmintic drug usage in grazing ruminants. Studies are required to know the optimum levels of tannins in order to have this positive response. The concentration of tannins should not be high enough so that the true digestibility of the substrate is appreciably decreased.

Ingestion of phenolic compounds such as tannins have been shown to various gastrointestinal disturbances. Hervas et al. [22] reported that condensed tannins (quebracho) extract diet was not toxic in terms of digestive tract (abomasums, small intestine, mucous and caecum) and plasma chemistry examinations in sheep supplemented less than 1.5 g/kg LW or less than 83 g/kg DM a day. However, sheep received condensed tannins up to 3 g/kg LW or 188 g/kg/DM a day, animals showed striking lesions in the digestive track, and changes in plasma biochemistry. Consumption of a small amount of mimosa tannins daily (3.5 g/kg DM) in diary cows (461 kg LW) does not cause toxic effects or does not negative affect cows performance, but depressed plasma urea concentrations [23] . It has been shown that consumption of a small amount of hydrolysable chestnut tannins daily (20.8 g/kg DM) in lambs (15 - 25 kg LW) does not cause toxic effects or does not negatively affect lamb performance [24] . Most of hydrolysable tannins toxicosis is natural poisonings documented in cattle consuming oak tree leaves [25] and the actual levels of hydrolysable tannins consumed are seldom reported. Krisper et al. [26] reported that large quantities of chestnut tannins were toxic to the liver and kidney, but no detrimental effects (liver, kidney, stomach, and small intestine tissue) observed when chestnut tannins fed to piglets and rats during 28 days. In the present study, 1.5% mimosa and chestnut tannins supplementations per kg dry matter intake in heifers does not negatively affected in cattle blood chemistry, except plasma cholesterol level. Cattle fed 1.5% chestnut tannins diet over the 70 days increased plasma cholesterol level, but mimosa tannins did not, indicating that hydrolysable tannins may be affected lipid metabolism by unknown mechanisms. It is conceivable, as previously suggested [27] , that volatile fatty acids and particularly propionate plays a hypocholestrolemic role. However, it remains that a direct effect of the physiological concentrations of VFA and plant tannins on hepatic cholesterogenesis is still uncertain in ruminants. These studies also indicate that feeding low level (<1.5% tannins/DMI) of plant tannins to ruminants may has no detrimental effects.

It was concluded that heifers grazing winter wheat forage received plant tannins increased ADG with generally no detrimental effects. The increase in ADG may be due to decrease fecal parasites infections.

B. R.Min,K.Hernandez,W. E.Pinchak,R. C.Anderson,J. E.Miller,E.Valencia, (2015) Effects of Plant Tannin Extracts Supplementation on Animal Performance and Gastrointestinal Parasites Infestation in Steers Grazing Winter Wheat. Open Journal of Animal Sciences,05,343-350. doi: 10.4236/ojas.2015.53038