Effect of cottonseed oil and tea (Camellia sinensis) by-product on digestibility, growth performance and methane production of growing cattle

Chu Manh Thang, Tran Hiep¹ and Le Dinh Phung²

National Institute of Animal Science, Hanoi, Vietnam
thangslu@gmail.com
¹ Faculty of Animal Science, Vietnam National University of Agriculture, Vietnam
² Faculty of Animal Sciences, Hue University of Agriculture and Forestry, Hue University, Vietnam

Abstract

Combined levels of cottonseed oil and tannin from tea by-products ( Camellia sinensis) were added to diets fed to thirty growing crossbred cattle (Brahman x Laisind) in a completely randomized block design (RCB) experiment with six replications per treatment. The animals were offered one of 5 diets: a basal diet (control), and the basal diet supplemented with 1.5 or 3% cottonseed oil in each case with a “tea” by-product estimated to provide tannin at 0.3 and 0.5% of the diet.

The cottonseed oil and tannin-rich tea by-product improved the live weight gain and feed conversion and reduced production of enteric methane. It is hypothesized that the improved animal productivity was due to the additives modifying the rumen fermentation leading to: (i) an increase in glucogenic precursors as reduced methanogenesis would lead to increased rumen propionate; and (ii) a reduced rate of rumen fermentation leading to increased rumen escape of nutrients for more efficient enzyme digestion of protein and starch in the intestine and of fiber in the cecum-colon.

Key words: glucogenic precursors, protozoa, tannin

Introduction

There are numerous dietary methods to reduce enteric CH₄ emission from ruminants. Tannin may inhibit methanogenesis directly and also via inhibition of protozoal growth (Patra and Saxena 2010). In Vietnam, including foliage containing tannin in the diet reduced methane production in beef cattle (Chu Manh Thang et al 2016) and in dairy cattle (Tran Hiep et al 2016b). Tannin exerts an anti-microbial action on microbial growth including cellulolytic bacteria and fungi (Patra and Saxena 2009), which may adversely affect fiber utilization. Macheboeuf et al (2008) studied the dose–response effects of different essential oils on methane inhibition and VFA production. Kirisci and Kamalak (2019) reported that garlic oil inhibited the overall fermentation by the rumen microbiota. Cottonseed oil supplement in diets for lactating cows increased milk yield by 5.4-12.2% and reduced methane emission intensity calculated as L/kg FCM by 18.8- 37.9% (Tran Hiep et al 2016a). In an in vitro experiment, Suharti et al (2019) concluded that the combination of Sapindus rarak extract containing tannin and canola oils in the concentrate decreased protozoa population, increased Anaerovibrio lipolytica growth, NH₃ concentration, dry matter and organic matter digestibility. Khang et al (2019) concluded that feeding a combination of cassava foliage and coconut cake gave a better growth and feed conversion ratio, and with less methane production in Holstein Friesian cattle.

Therefore, this study was aimed at determining effects of supplements of cottonseed oil and tea byproduct, as source of tannin, on feed intake, digestibility, growth performance and methane:carbon dioxide in eructed gas of crossbred (Brahman x Laisind) cattle.

Materials and methods

Location

The experiment was conducted at a cattle farm in Dong Chi village, Le Chi commune, Gia Lam district, Hanoi, Northern part of Vietnam.

Animals and experimental design

Thirty growing crossbred cattle (Brahman x Laisind) were used in the experiment. The animals were around 13 months of age with an average live weight of 251 ± 32.3kg. They were kept in individual pens with roofing and concrete floor. Before the adaptation period, all the animals were treated against intestinal parasites using DeptinB ™ (4ml/100 kg LW) and were vaccinated against pasteurellosis and 15 days later for Foot and Mouth Disease. The animals were weighed after the adaptation period when the feed intake was stable.

The experiment was arranged as a completely randomized block design (RCB) with 5 treatments and six replicates per treatment. Block was the initial body weight. The animals were offered one of the 5 diets: a basal diet (control), and the basal diet supplemented with 1.5 or 3% cottonseed oil in each case with “tea” by-product estimated to provide 0.3 and 0.5% tannin in the diet (Table 1).

Feeds and feeding

Elephant grass (Pennisetum purpureum) of 40-45 days age was harvested daily and chopped into 3-5 cm length before feeding. Ground maize stover was ensiled with 0.5% salt for 60 days before feeding. The tea ( Camellia sinensis) by-product was collected from a tea processing factory in Thai Nguyen province. The oil and tea by-product were mixed with the concentrate before feeding.

Feeds were offered twice per day, in the morning (07.30) and afternoon (16.30). At each feeding, the mixture of concentrate, maize meal, cassava pulp, cottonseed oil and tea by-produc was offered first, followed by the elephant grass and maize stover silage. The cattle had free access to drinking water and a mineral block. The experiment was for 90 days after a 15-day adaptation.

Measurements

Feed intake:

The daily feed offered was recorded and refusals were collected for individual animals in the morning of the next day.

Live weight:

At the beginning (after the adaptation period) and at the end of the experiment, the animals were weighed at 06.00 h before feeding on two consecutive days using an electronic scale (RudWeight, Australia).

Digestibility:

On days 29^th - 30^th each month, total feces of each cattle were collected and a 10% sample stored at -18⁰C. At the end of the experiment, all fecal samples of each animal were mixed and 10% retained for chemical analyses. Apparent digestibility was calculated based on DM eaten and feces voided.

Chemical analyses

The feeds offered and feed refusals were sampled daily and pooled each fifteen days for analyses of DM, CP, ether extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF) and ash, according to the standard methods of AOAC (2000). NDF and ADF were determined according to the procedure of Van Soest et al (1991).

Methane and carbon dioxide in eructed gases

After 90 days, the cattle were confined individually in a gas-proof chamber (a bamboo frame covered with polyethylene and with a fan to mix eructed gas and air) for sampling of eructed gases and residual air in the chamber. After 10 minutes to equilibrate eructed gas and air, samples were taken into airtight bags for analyses of CH₄ and CO_2, using a Gasmet infra-red meter (GASMET 4030; Gasmet Technologies Oy, Pulttitie 8A, FI-00880 Helsinki, Finland), following the procedure described by Madsen et al (2010).

Statistical analyses

Data were analyzed by the General Linear Model (GLM) application in the ANOVA program of the Minitab software (version 16.0). Sources of variation included treatment, block and error. The statistical model used was:

Y_ijk = m + a_i + β_j + e_ijk

Where: where Y_ijk is the dependent variable, m is the overall mean, a_i is effect of the treatment i, β_j is effect of the block (initial animal weight) and e_ijk is a random error.

Results

Feed intake, digestibility and growth performance

The only consistent finding in the data for feed intake, live weight gain and feed conversion (Table 3) was that animal response was improved by the additives, at low or high levels of each, as compared with the un-supplemented control (Figures 1 and 2). However, there were opposing effects due to level of each additive. At low levels of cottonseed oil the higher level of tea by-product improved weight gain and feed conversion; but at the higher level of cottonseed oil, increasing the tea by-product had a negative on weight gain and feed conversion. There are no obvious explanations for these opposing effects.

Figure 1. Effect of cottonseed oil and tea- byproduct on live weight gain	Figure 2. Effect of cottonseed oil and tea- byproduct on feed conversion

The results for apparent digestibility coefficients were equally confusing with highest values being recorded on the control diet, which did not include additives (Table 4)

Methane /carbon dioxide ratio in eructed gases

The ratio of methane to carbon dioxide in the eructed gas collected from the cattle (Table 5) revealed close relationships with the rates of live weight gain and feed conversion, both of which were improved as the proportion of methane relative to carbon dioxide decreased (Figures 3 and 4)

Figure 3. Relationship between methane:carbon dioxide ratio in eructed breath of cattle and their rate of live weight gain	Figure 4. Relationship between methane:carbon dioxide ratio in eructed breath of cattle and their rate of feed conversion

Discussion

The improvement in live weight gain and feed conversion has to be considered in relation to: (i) the effects of the additives in reducing rumen methane production; and (ii) the effect of the reduced methane production (and other related changes in the rumen fermentation) on the supply of nutrients to the sites of metabolism.

Tannin may inhibit methanogenesis directly and also via inhibition of protozoal growth; cottonseed oil may also reduce protozoa populations leading to less methane production. Seng et al (2001) and Nhan et al (2007) suggested that a single drench of readily available vegetable oil delivered short term suppression of rumen protozoa populations leading to productivity advantages. A reduction in methane will release hydrogen for incorporation into propionic acid a major precursor of glucose. Williams and Coleman (1992) reported that rumen protozoa are significant hydrogen (H ₂) producers and synthesize mainly acetate and butyrate rather than propionate. Therefore, defaunation is expected to induce a greater proportion of propionate in the ruminal volatile fatty acids (VFA) (Eugène et al 2004). In other aspects, rumen protozoa account for as much as half the total microbial biomass in the rumen and up to 50% of total fermentation products (Newbold et al 2015). Removing protozoa from the rumen may result in modifying ruminal digestion of plant cell walls and starch which are considered to be the two main sources of energy supply for ruminants (Jouany 1997). The proportion of methane relative to carbon dioxide decreased in group fed treatment comparing to Control was found in our study. Son et al (2018) reported that the daily CH₄ production in grazing sheep tended towards a lower CH₄ yield in sheep that had been defaunated. Supplementation of tannin from tea by-products in growing cattle (Chu Manh Thang et al 2016) or of cottonseed oil for dairy cattle (Tran Hiep et al 2016b) resulted in a reduction in the proportion of methane relative to carbon dioxide.

Both tannins and cottonseed oil could depress overall rate of rumen fermentation, leading to greater escape (bypass) of starch and protein for more efficient utilization by enzymes in the intestine (Phonethep et al 2016), and of fiber to the cecum-colon where acetogenesis predominates over methanogenesis (Demeyer e al 1991). The CP content of tea by-products is 22.9% DM found in this study (Table 2). Min et al (2003) suggested that tannins bind and protect protein, fiber, and carbohydrates from degradation in the rumen. These compounds form complexes with protein in the rumen, and then are dissociated under the acidic conditions of the abomasum, allowing the protein to be digested and absorbed in the small intestine (Barry et al 2001). In a recent review, Son et al (2020) demonstrated a consistent effect of defaunation to increase microbial protein outflow which increased protein supply to the host for live weight gain and wool production. Patra and Yu (2015) suggested that binary combination of anti-methanogenic inhibitors with complementary mechanisms of actions on methanogenesis may alter the archaeal communities and may decrease methane production additively without negatively impacting upon rumen fermentation and degradability.

Conclusion

Addition of cottonseed oil and tannin-rich tea byproducts to a nutrient-rich diet fed to crossbred Brahman cattle improved their live weight and feed conversion and reduced production of enteric methane. It is hypothesized that the improved animal productivity was due to the additives modifying the rumen fermentation leading to: (i) an increase in glucogenic precursors as reduced methanogenesis would lead to increased rumen propionate; and (ii) a reduced rate of rumen fermentation leading to increased rumen escape of nutrients for more efficient enzyme digestion of protein and starch in the intestine and of fiber in the cecum-colon.

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Received 26 March 2020; Accepted 15 April 2020; Published 1 May 2020

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