Abstract
Simple SummaryAnimal nutritionists are challenged to increase animal production with respect to competitiveness and efficiency yet at the same time produce products that are healthy for the consumer and friendly to the environment. Black (BTL) or green (GTL) tea leaves and their spent tea leaf residues (STL) are rich in polyphenols, and can be used to not only supplement animal diets but also reduce the environmental burden of their safe disposal. These tea products were assessed for their potential use as natural dietary additives in ruminant diets to not only optimize rumen in vitro digestibility and fermentation but also reduce methane (CH4) emission. Both types of tea leaves were effective in significantly reducing ammonia (NH3) and CH4 production without decreasing rumen degradability. Tea leaves and their STL inclusions increased the acetate to propionate (A:P) ratio significantly. The GTL-containing diets had significantly greater rumen degradability but lower rumen NH3 compared with the BTL diets. Decreased rumen NH3 production in ruminants can be a possible sign of increasing bypass protein whilst reduced rumen CH4 release can be useful for enhancing energy use efficiency and environmentally friendly ruminant production. Black (BTL) or green (GTL) tea and their spent tea (STL) leaves can be used as natural dietary additives for ruminants. Experiment 1 used a 3 × 2 × 2 factorial arrangement, with four replicates (n = 4) to test the effects of three different inclusions of tea leaves at 0 (control), 50, and 100 g/kg DM of two different tea types (BTL and GTL) in two different total mixed diets containing either ryegrass hay (RH) or rice straw (RS) on in vitro rumen organic matter degradability (IVOMD), volatile fatty acids (VFA), pH, ammonia (NH3), and methane (CH4) outputs over a 24 h incubation time. Experiment 2 followed a 3 × 2 × 2 factorial arrangement, with eight replicates (n = 8) to study the impacts of three different STL inclusions at 0, 100, and 200 g/kg DM of two different STL types (black and green) into two different total mixed diets containing either RH or RS on the same in vitro measurements. Both types of tea leaves decreased NH3 (p < 0.001) and CH4 (p < 0.01) without affecting (p > 0.05) rumen degradability, but the effect of their STL was less remarkable. Tea leaves and their STL inclusions improved (p < 0.01 and p < 0.001, respectively) the acetate to propionate (A:P) ratio. Compared with BTL, GTL containing diets had higher IVOMD (p < 0.05) and A:P ratio (p < 0.05) but lower NH3 (p < 0.001). Reduced rumen NH3 and CH4 outputs can be useful for protein and energy use efficiency while an increased A:P ratio might lead to increased milk fat synthesis and reduced low-fat milk syndrome. The surplus or wasted tea leaf products could be used as sustainable sources of nutrients to optimize rumen function and minimize environmental impacts of feeding ruminant animals.
Highlights
Black (BTL) or green (GTL) tea leaves and their spent (STL) residues contain considerable amounts of protein, minerals, and plant secondary metabolites including tannins and saponins [1]
Eight replicates in Experiment 2 consisted of 4 replicates of each STL that was processed in the laboratory at Newcastle University and 4 replicates of each STL that was collected from the company for both black and green STL
The concept of adding either black or green STL in diets was tested at a higher level of up to 20% because each STL was recognized as the residual waste after brewing the original green or black tea leaves
Summary
Black (BTL) or green (GTL) tea leaves and their spent (STL) residues contain considerable amounts of protein, minerals, and plant secondary metabolites including tannins and saponins [1]. Catechins and theaflavins [2,3] are the major polyphenols in GTL and BTL, respectively Both tea leaves contain considerable amounts of alkaloids, mainly caffeine [3]. Since NH3 is used as one of the main sources of N for rumen microbiota, its quick production may exceed the capability of microbes to use it, especially if it is not synchronized by supplying additional soluble carbohydrates in diets. A previous study [6] concluded that tea tannin inclusion in the diet of fattening lambs could increase their weight gains without affecting feed intakes and protein digestibility This is an indication that bound protein was not well digested in the rumen but was available as bypass protein that is able to be absorbed in the small intestine
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