The effects of supplementation with green tea waste on in vivo and in vitro rumen fermentation in cattle

Ensiled green tea waste (GTW) was offered to growing cattle as a protein supplement compared to lucerne hay cube. Rumen fermentation was evaluated by in vivo rumen pH, volatile fatty acids (VFA) and NH3-N as well as in vitro gas production from hay, maize, and soyabean meal. GTW contained about 340 g/kg crude protein (CP), 90 g/kg total extractable tannins and 14 g/kg condensed tannins, and was offered as protein supplement to growing cattle. GTW silage made up 56 g/kg DM and 130 g/kg CP of the diet in this performance trial. Gas production from maize incubated with rumen fl uid of cattle fed GTW was reduced compared with cattle fed lucerne hay cube during 2 months. However, VFA and NH3-N concentrations of in vivo rumen were not affected and growth performance of cattle was similar to lucerne hay cube treatment. It is concluded that GTW silage could be used as protein supplement in a low proportion (about 50 g/kg DM and 130 g/kg CP of diet) in the ration for growing cattle.


INTRODUCTION
Tea is one of the world's most popular beverages, and more than 3 million tons of tea leaf were produced in 2002.In Japan, beverage companies manufacturing various tea drinks produce about 100 thousand tons of tea leaf waste annually.Green tea waste (GTW) contained 280 g/kg DM of crude protein (CP) and 90 g/kg DM of tannins (Kondo et al., 2004).Kondo et al. (2004) found that GTW has a potential of protein supplement for low-quality forages.However, it is still necessary to evaluate GTW as a feedstuff from the point of rumen fermentation.
In this study, the activity of rumen fermentation in cattle fed GTW was assessed with parameters such as in vivo pH, NH 3 -N, volatile fatty acids (VFA) concentration and also in vitro gas production using rumen fl uid obtained from the animals fed GTW.Simultaneously, growth performance in cattle fed GTW silage substituted with lucerne hay cube was investigated to evaluate the value of GTW as a protein supplement.

Animals and dietary treatments
Ten Japanese Black beef cattle (6 female and 4 castrates) were divided into two groups (each group had 3 females and 2 castrates) and housed in two groups.At the start of the preliminary period, the mean body weight of the animals was 263.5 kg.The diets were as follows: a. Commercial concentrate plus timothy hay plus lucerne hay cube (LHC); b.Commercial concentrate plus timothy hay plus GTW silage (GTWs).
Both treatments had the same amount of commercial concentrate and timothy hay.Lucerne hay cube or GTW silage was added as a protein supplement.The diets designed to satisfy the nutrient requirements of growing cattle were offered in fi xed quantities.Rumen fl uid was collected 4 h after the morning feed at month 0, 0.5, 1 and 2 for pH, VFA and NH 3 -N analysis as well as in vitro gas production.

In vitro gas production experiment
The degradation characteristics of timothy hay, maize and soyabean meal were measured by in vitro gas production technique (Menke et al., 1979).Two hundred mg sample ground to 1 mm screen was incubated in 100 ml glass syringes with 30 ml buffered rumen fl uid from the cattle fed experimental diets.The glass syringes containing samples and rumen fl uid-buffer mixtures were incubated in a water bath at 39°C, and subsequently gas production (ml/200 mg DM) was measured before incubation (0 h) and at 2, 4, 6, 8, 10, 12, 24, 48 and 72 h and fi tted to the model described as G = a + b(1 − e -ct ) (Ørskov and McDonald, 1979).

RESULTS
The chemical composition of the feedstuffs fed to growing cattle in experiment 2 is presented in Table 1.CP content in GTW was higher than in timothy hay, formulated commercial concentrates and lucerne hay cube.In this experiment, the amount of CP from lucerne hay cube or GTW silage covered 130 g/kg CP of the whole diets given to cattle.TET and CT contents in GTW silage were higher than in the other feedstuffs (Table 1).GTW silage was added at a rate of 56 g/kg DM of total feed in GTWs treatment.TET and CT concentrations of the whole diets given to cattle were 3.2 and 8.2 g/kg DM, 0.4 and 1.2 g/kg DM in LHC and GTWs treatments, respectively.Rumen pH, VFA and NH 3 -N concentrations on months 0, 0.5, 1 and 2, were not signifi cantly different among the treatments on each month.Potential gas production (a + b) from maize incubated with rumen fl uid of GTWs treatment tended to be lower (P<0.10) on months 0.5 and 2, and signifi cantly lower on month 1 (P<0.01)(Table 2).With incubated timothy hay and soyabean meal, no treatment differences were observed in months 0.5 and 1, but in month 2 the gas production tended to be lower (P<0.10) on the GTWs treatment.The fractional rate of gas production from any substrate incubated with rumen fl uid from both treatments was not signifi cantly different.Although the experiment lasted three months, the body weight gain did not differ signifi cantly between treatments.

Table 1 .
Chemical compositions of feedstuffs

Table 2 .
In vitro gas production characteristics of timothy hay, maize and soyabean meal in beef cattle fed the diets with lucerne hay cube (LHC) or GTW silage (GTWs) on months 0, 0.5, 1 and 2