Effect of plant tannin-containing diet on fatty acid profile in meat goats

Phytochemical plant tannins are phenolic compounds that interfere with biohydrogenation (BH) of monounsaturated-(MUFA) and poly-unsaturated fatty acids (PUFA). The objective of the present animal study was to investigate the effects of three different levels of phytochemical tannin-containing ground pine bark diet on fatty acid profiles of goat meat, with particular reference to MUFA and PUFA. The saturated fatty acids (SFA), PUFA, and PUFA/SFA ratios in subcutaneous adipose tissue as well as MUFA and PUFA composition of mesenteric kidney fat were increased with increasing phytochemical tannin-containing ground pine bark supplementation. The study showed that phytochemical plant tannins could be a means to moderate the accumulation of unsaturated fatty acids with the aim of improving percentage of these PUFA/SFA ratios in goat meat. The effects would be useful to improve carcass fatty acids composition and human health.


Introduction
The effect of phytochemical condensed tannins (CT) on the nutritive value, animal performance, carcass evaluation of forages and on the health of grazing ruminant animals have been investigated Solaiman et al., 2010;Min et al., 2012). Goats fed a diet containing CT up to 30% DM ground pine bark (PB) have also been shown to increase dry matter intake (DMI), average daily gain (ADG), improve meat tenderness, and overall consumer acceptability of goats loin (Min et al., 2012, Leick et al., 2012), but CT containing-PB supplementation in relation to fatty acid profile and lipid oxidation state has not been conducted in goats.
Recently, Min et al. (2012) have described improved animal performance and ADG in goats fed phytochemical CT-containing ground PB (0, 15, and 30% PB/kg of DMI), while linearly decreased rumen ammonia-N, acetate, and acetate to propionate ratio. Acetic acid is utilized as the major source of acetyl-CoA for synthesis of lipids in ruminants (Hanson and Ballard, 1967). Hanson and Ballard (1967) reported that considerable amounts of [ 14 C] acetate are incorporated into fatty acids synthesis and are associated with acetyl-CoA synthetase enzyme in ruminant liver. Min et al. (2014) reported that tannins containing ground PB diet had a detrimental effect on survival of certain rumen microorganisms. Rumen bacteria are responsible for biohydrogenation of dietary polyunsaturated fatty acids (PUFA), the products of which include conjugated linoleic acid (CLA) and saturated fatty acids (SFA; Priolo and Vasta, 2007). It has been shown that feeding tannins to ruminants can favorably alter ruminal biohydrogenation of dietary linoleic acid, enhancing accumulation of trans-11 18:1 (vaccenic acid) in the rumen and thereby the content of some human health promoting fatty acids, such as vaccenic acid and rumenic acid (Toral et al., 2011). If hydrogenation is reduced, the potential for oxidation of PUFA in the tissue may be increased as a result of feeding dietary tannins. Conversely, derivatives of tannins extracts directly added to ground beef have been shown to have antioxidant effects and reduce lipid oxidation of cooked patties (Ahn et al., 2006). Subsequent work has been shown that thiobarbituric acid reactive substances (TBARS) for 30% PB diet were less than that of 0% PB diet. (Leick et al., 2012). However, reports on impacts of these phenolic compounds on meat fatty acids profile are very limited and inconsistent. The objective of this experiment was to assess the effects of a partial replacement of ground wheat straw (WS) with CT-containing PB on a potential utilization of PB as feed replacement on fatty acids composition and lipid oxidation state in goats associated with different level of PB powder diets.

Materials and Methods
The animals used in this study were cared for according to the

Journal of Animal Research and Nutrition ISSN 2572-5459
Live Animal Use in Research Guidelines of the Institutional Animal  Care and Use Committee of the Tuskegee University (Tuskegee,  AL). Animals were fed once a day at 0800 h and had free access to water and a trace mineral salt block. Grain mixes and hay were offered separately, and refusals were recorded daily. Feed intake and refused feed were treated as daily repeated measures for 83 days for growth performance and body weight gain efficiency determination.

Statistical analysis
Data were analyzed by the Mixed Model procedure of the SAS (SAS, Inst., Inc., Cary, NC) for completely randomized design with the factors examined being three levels of PB supplementation in the diets. Linear and quadratic effects were determined utilizing poly-nominal orthogonal contrasts for equally spaced treatments (Min et al., 2012). Animals were the experimental unit and were treated as a random effect. The variables included were diet-composition, feed intake, and fatty acids profile. Data are presented as LS mean values together with the standard error of the mean (SEM).

Chemical composition of diets
Diets were isonitrogenous and isocaloric but differed in NDF, lignin, and CT concentrations; lignin and CT concentrations were greater in 15% and 30% PB rations, whereas NDF concentration was decreased compared with control diet (

Intake and growth performance
Body weight and dry matter intake (DMI) of Kiko crossbred goats are summarized in Table 2. Total DMI (linear; P = 0.001) was increased as ground PB increased in the diets. There was no difference in initial BW of goats among treatments; however, final BW tended to increase (P = 0.06) linearly as the level of ground PB increased in the diets ( Table 2). Diet containing 30% ground PB had higher total DMI when compared to other treatments.
The MUFA and PUFA composition of MKF (Table 4) were increased (linear; P < 0.01) with increasing ground PB supplementation. However, SFA and PUFA/SFA ratios in MKF were not affected by feeding PB diet. These results indicated that goats receiving PB supplementation produced carcasses with more MUFA and higher PUFA. Fatty acids percentages increased linearly (p < 0.05-0.01) for 13:1, 16:1t, 16:10, 17:00, 18:1 n-9c, 18:1 n-7c, 18:3 n-6c, and 22:6 n-3 in goats receiving PB diets compared to control diet. These changes were characterized by an increase in PUFA with 18C and a concomitant increase in most medium chain saturated fatty acids (10:0 to 17:0), which is unknown at this point and need further study. The TBARS increased from d 1 to d 5 of storage (p < 0.001), but were not affected by ground PB diet ( Table 5).

Journal of Animal Research and Nutrition
ISSN 2572-5459 protein) had higher DMI than those fed the alfalfa hay based diet. This may be attributed to the fact that goats naturally prefer browse that contains phytochemical secondary compounds including tannins and other alkaloids. In addition, animals previously exposed to plant secondary compounds eat much more secondary compounds-containing feeds than inexperienced animals (Villalba et al., 2004).
Min et al. (2003) reported that beneficial effects of CT in the diet on sheep performance may occur in the range of 2 to 4% CT of diet DM. However, the wool growth response was negative when the CT concentration was above 5% CT of diet DM. Conversely, when CT concentration decreased below 2 % of diet DM, the production response was variable. This may partially explain why the growth performance of goats in the present study was improved for those goats receiving diets containing 15  Pine bark is one of the abundant timber industry by-products in the USA and it is only $38/ton in a local timber company (Opelika, AL). If we include PB as a feed ingredient up to 30% of total diets, it is only requires $11.40 PB/ton. Therefore, it has potential for economic and nutritional benefit to modify carcass meat quality. The current study indicated that plant tannins could be a means to moderate the accumulation of USFA with the aim of improving percentage of these PUFA/SFA ratios in goat meat. The effects would be useful to improve carcass fatty acids composition and human health.
receiving the tannin-free diets. These results confirm, in vivo, that tannins-containing diets reduce ruminal biohydrogenation, as previously reported. This implies that tannin supplementation could be a useful strategy to increase the rumenic acid and PUFA content and to reduce the SFA in ruminant meats, in agreement with our results. Fatty acids percentages linearly increased for 10:00, 14:00, 16:00, 18:00, 18:1 n-7c, 18:1 n-7t, 18:2 n-6c, 18:3 n-3, and 20:2 n-6 in PB supplemented goats compared to control diet. This may suggest the ineffectiveness of the type of tannins used, the level of dosage rate, or both, at exerting major effects on rumen biohydrogenation, while most temporal changes in meat fatty acids profile were likely explained by the presence of level of CT in the diet.
Moreover, MUFA and PUFA composition of MKF were increased with increasing PB supplementation. These results indicated that goats receiving PB supplementation produced carcasses with more MUFA and higher PUFA. These changes were characterized by an increase in PUFA with 18C and a concomitant increase in most medium chain saturated fatty acids (10:0 to 17:0), which is unknown at this point and need further study.
Antioxidants are used to minimize the oxidative changes in meat and meat products. The TBARS increased from d 1 to d 5 of storage (p<0.001), but were not affected by PB diet. Tannins may serve to impede muscle oxidation during storage serving to increase shelf life of whole muscle products. It has been shown in rats consuming high-tannin sorghum, to have lowered markers of protein oxidation in rat muscle after 6 d of refrigerated storage (Larrain et al., 2007). Du et al. (2002) showed higher a* (redness) values in thigh patties after 7 d storage at 4 •C from chickens fed 10% high-tannin sorghum. This antioxidant effect of dietary tannins may assist to improve meat product acceptance by maintained redness and decreased oxidation. Evidence of this work was not found in the present study, but may have research merit as tannin supplementation in finishing beef and small ruminants may help to meet product stability expectations of the consumer as well as being a "natural" product.
Although goats can tolerate relatively high levels of phytochemical tannins, supplemental tannin-containing forages in goat's diet is accepted as an important factor affecting feed intake. Solaiman et al. (2010) reported that total DMI of growing goats increased when tannin-containing Sericea lespedeza (Lespedeza cuneata) ground hay (6.5% CT in DM) replaced alfalfa meal in the grain mixes, and Turner et al. (2005) reported that goats receiving the CT-containing Sericea lespedeza hay (23.1 mg CT/g soluble Journal of Animal Research and Nutrition ISSN 2572-5459