Ensiled or Oven-dried Green Tea By-product as Protein Feedstuffs: Effects of Tannin on Nutritive Value in Goats

Makoto Kondo,Hiro-Omi Yokota,Kazumi Kita

doi:10.5713/ajas.2007.880

Abstract

Ensiled or oven-dried green tea by-products (GTB) were evaluated in goats for their nutritive potential as protein feedstuffs based on in vitro and in vivo digestibility. To elucidate the effects of tea tannin on in vitro digestibility, polyethylene glycol (PEG) was used as a tannin binding agent. Both ensiled and dried GTB contained 31.9 to 32.6% of crude protein (CP) on a dry matter (DM) basis. Phenolics and tannins in soybean meal and alfalfa hay were low or not detected, but they were high in both ensiled and dried GTB (7.3-10.1% DM as total extractable tannins). In vitro protein digestibility in the rumen ranked: soybean meal>alfalfa hay cube>ensiled GTB = dried GTB. The protein digestibility post-ruminally of these feedstuffs showed a similar trend to that in the rumen, but the digestibility of ensiled GTB was significantly higher than that of dried GTB. Addition of PEG improved the in vitro protein digestibility of both kinds of GTB in the rumen and post-ruminally, indicating that tannins suppressed the potential protein digestibility of GTB. The increased protein digestibility by PEG addition was not significantly different between ensiled and dried GTB in the rumen, but the percentage increment of ensiled GTB was higher than dried GTB post-ruminally. In the in vivo digestibility trial, ensiled and dried GTB were offered to goats as partial substitutes for soybean meal and alfalfa hay cubes. Offering both GTB to goats as 5-10% on a DM basis did not affect nutrient digestibility, ruminal pH, volatile fatty acids, and ammonia concentration. However, the eating time of the GTB-incorporated diet was longer than that of the basal diet. It took 1.4 and 1.6 times longer than the control diet, to eat the diet completely when GTB silage was offered at 5 and 10% levels, respectively, of the total diet. These results show that ensiled and dried GTB are useful as partial substitutes for soybean meal and alfalfa hay cubes for goats with respect to nutritive value. Because of lessened palatability, it is recommended that GTB be incorporated into the diet at 5% on a DM basis.

Highlights

Protein-rich commercial feedstuffs such as soybean meal and alfalfa hay are often used in livestock production, but they are generally expensive
We investigated the substitution of green tea by-products (GTB) for soybean meal and alfalfa hay cubes on in vivo digestibility
Green tea by-product preparation The GTB used for this study was obtained from a local tea company

Summary

Introduction

Protein-rich commercial feedstuffs such as soybean meal and alfalfa hay are often used in livestock production, but they are generally expensive. The renewed interest in domestically produced protein-rich forage is partially a consequence of the BSE crisis and the fluctuations in soy product price resulting from global climatic aberration in the world and increasing demand from China and other factors. Green tea is a popular drink in eastern Asia, some parts of the Middle East and North Africa. Consumption of green tea in cans, packs and bottles has increased.

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