Effects of Adding Compound Essential Oil to Diet On Growth Performance and Economic Benefits of Weaned Lambs

Dong Airong¹, Chen Qian¹, Yu Miao², Huang Mingya², Chen Juhong³,

Zhang Zhengfan¹, Guo Chunhua^2*, Lyu Jirong^2*

1 College of Life Science and Technology, Southwest Minzu University, Chengdu 610041

2 DadHank (Chengdu) Biotech Corp., Chengdu 611130

3 Lezhi Nature Farming Co., Ltd，Ziyang 641500

Abstract: The purpose of this test was to study the effects of compound essential oil on growth performance and economic benefits of weaned lambs. Select 60 weaned Chuanzhong black goats (LeZhi type) aged of 2 months, with an average weight of 19.54 ± 2.23 kg and equal number of males and females. The factorial test design (1+2×2) was used to randomly divide into 5 groups, with 4 replicates in each group and 3 goats in each replicate. The control group (CT) was fed a total mixed pellet feed with a 60:40 concentrate-to-forage ratio, without adding compound essential oils. The 4 test groups L-EO1, L-EO2, H-EO1 and H-EO2 were fed low-level concentrated（low concentrate） feed (50:50) + essential oil 1 (100 g/t), low-level concentrated （low concentrate）feed (50:50) + essential oil 2 (100 g/t), high-level concentrated feed (70:30) + essential oil 1 (100 g/t), high-level concentrated （high concentrate） feed (70:30) + essential oil 2 (100 g/t) total mixed pellet feed, respectively. The pre-feeding period was 10 days and the trial period was 30 days. The results showed that: 1) Compared to control group, the addition of compound essential oils to diet significantly increased feed intake (P=0.002), but had no significant effect on average daily gain and feed-gain ratio (P＞0.05). The effect of concentrate-to-forage ratio on feed intake and average daily gain was not significant (P＞0.05), but high-level concentrated（high concentrate） feed significantly reduced feed-gain ratio (P=0.035). The effects of the two compound essential oils on average daily gain, feed intake and feed-gain ratio were not significant (P＞0.05). The interaction effect of dietary concentrate-to-forage ratio and compound essential oil was not significant (P＞0.05). 2) Compared to control group, the economic benefits of L-EO1, H-EO1 and H-EO2 have increased by 13.70%, 16.71% and 13.90%, respectively, while the benefits of L-EO2 are 9.57% lower than that of control group. The economic benefits of the high-level concentrated （high concentrate） feed group increased by 12.97% on average compared to low-level concentrated feed group, and the economic benefits of the essential oil 1 increased by 12.76% on average than that of essential oil 2. In summary, under the conditions of this test, adding compound essential oils to diet can increase the feed intake of fattening lambs, and high-level concentrated feed reduced feed intake and feed-gain ratio. In terms of economic benefits, the benefits of high-level concentrated feed are better than those of low-level concentrated feed, and the benefits of essential oil 1 are better than those of essential oil 2.

INTRODUCTION

Antibiotics are mainly secondary metabolites produced by bacteria, molds or other microorganisms or artificially synthesized substances that have a specific ability to kill microorganisms. The antibiotics applied in livestock and poultry production can be divided into two types: one is feed antibiotics, which are（is） added to feed through certain technical means to play a role in disease prevention and growth promotion in production; The other is therapeutic antibiotics, which are（is） administered by stockmen（ feeding managers） to treat livestock and poultry through mixing in feed, injection and perfusion ^[1]. Due to the widespread use and even abuse of feed antibiotics for growth promotion, a series of problems such as drug residues, the emergence of drug-resistant strains, and environmental pollution have emerged, posing potential threats to human health. In March 2019, the Ministry of Agriculture and Rural affair proposed the “Withdrawal Plan for Pharmaceutical Feed Additives”, requiring that the production of commercial feeds containing antibiotic additives be banned from July 1, 2020. Therefore, safe, efficient, and pollution-free alternatives to feed antibiotics have been widely used in feeding production in recent years. Currently, the commonly used substitutes for feed antibiotics include Chinese herbal medicine, enzyme preparations, microecological preparations, antimicrobial peptides, plant essential oils, acidifiers, oligosaccharides, etc. ^[2-3]. Plant essential oils are usually substances extracted from plant tissues that contain multiple active ingredients, which have antibacterial, antioxidant, enhancing animal immunity and promoting animal growth ^[4]. However, due to their natural origin, the composition of plant essential oils is greatly affected by plant origin, extraction technology and extraction process, and the cost is high. Fortunately, with the continuous innovation of analytical and chemical technologies, many active substances with bactericidal functions in plant essential oils have been artificially synthesized and widely used in production. Adding plant essential oil to diet of ruminants can inhibit the growth of harmful bacteria in rumen to varying degrees, such as methanogens, promote the growth of dominant bacteria, such as Ruminococcus flavefaciens, Ruminococcus albus, and Fibrobacter succinogenes, improve the rumen environment, increase protein metabolism in rumen and improve feed utilization efficiency ^[5-7].

 Discussion

3.1 Effect of adding compound essential oils to diets on production performance of weaned lambs

The concentrate-to-forage ratio increases the level of concentrated feed by regulating the structure and nutritional level of diet. An appropriate ratio can regulate the microflora in rumen and the activity of digestive enzymes in GIT, thereby improving the production performance and feed utilization of ruminants. Hao Huaizhi et al. studied the effects of different concentrate-to-forage ratios (40:60, 50:50 and 60:40) in corn-stalk-based total mixed rations on the production performance of meat sheep, and the results showed that the average daily gain and average daily feed intake in the 60:40 group were higher than those in the 40:60 and 50:50 groups, while the feed-gain ratio was the lowest ^[8]. Gao Linqing et al. found that the average daily gain in the 70:30 group was significantly higher than that in the 50:50 and 40:60 groups ^[9]. Xu Xiangting et al. found that with the increase of proportion of concentrated feed in diet, the average daily gain showed an increasing trend, while the average daily feed intake and feed-gain ratio gradually decreased ^[10]. Yin Fuquan et al. also obtained similar results ^[11]. In this test, the concentrate-to-forage ratio in control group was 60:40, the concentrate-to-forage ratio in the low-level concentrated feed group was 50:50, and the concentrate-to-forage ratio in the high-level concentrated feed group was 70:30. The average daily gain and feed intake in the high-level concentrated feed group and low-level concentrated feed group were higher than those of control group, which was inconsistent with previous research results. This may be related to the addition of compound essential oils to both treatment groups. Adding plant essential oils to diet can inhibit mold growth and maintain the freshness of feed. In addition, essential oils have a special volatile aroma, inducing animals to increase their intake. Numerous studies have shown that adding plant essential oils to ruminant diets can regulate nitrogen metabolism in rumen, improve rumen fermentation patterns, and thereby improve feed utilization efficiency ^{[7, 12, 13]}. Yao Xixi et al. found that adding oregano essential oil to the diet of Holstein cows can effectively reduce the temperature of diet, improve palatability, increase dry matter intake and increase milk production ^[14]. Jiang Hui et al. also found that compared to control group, adding oregano oil significantly increased the average daily gain of Hexi cashmere goats. The main reason may be that oregano oil had a special volatile aroma and has a feeding attractant effect, which increased the feed intake of Hexi cashmere goats. In addition, oregano essential oil can improve the growth of microorganisms in rumen, enhance enzyme activity, facilitate feed digestion, and promote animal growth ^[15]. In this test, the addition of compound essential oils significantly increased the average daily feed intake and weight gain of goat, with the effect in essential oil 1 groups being better than essential oil 2 groups. This may be related to the main active substances of the two compound essential oils and further research is needed.

3.2 Effect of adding compound essential oils to diets on economic benefits of weaned lambs

The main factors that determine the level of economic benefits in feed production include average daily gain, market price and feed cost. The nutrients in diet are digested, absorbed, which are converted into body deposits. Therefore, the average weight gain reflects the comprehensive nutritional value of diet and the changing pattern between the feed intake and feed conversion rate ^[16]. From the economic benefit table, it can be seen that after adding compound essential oils, the feed intake in the high and low-level concentrated feed groups was higher than that in control group, while the feed intake in the high-level concentrated feed groups was lower than that in the low-level concentrated feed groups. The total feed cost in the high-level concentrated feed groups was higher than that in the low-level concentrated feed groups, but the weight gain was higher than that of the low-level concentrated feed groups. Therefore, the profit of the high-level concentrated feed groups was higher than that of the low-level concentrated feed groups. Xu Xiangting et al. ^[10] and Wang Xiaoguang et al. ^[17] both believed that the level of concentrated feed and daily gain were one of the key factors affecting economic benefits, which was consistent with the results of this study. In this study, L-EO1 and L-EO2 are both low-level concentrated feed groups, while H-EO1 and H-EO2 are both high-level concentrated feed groups. The economic benefits of L-EO1 are 25.73% higher than those of L-EO2, while the economic benefits of H-EO1 are 2.47% higher than those of H-EO2, indicating that the economic benefits of essential oil 1 are better than those of essential oil 2.

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Fund Project: National Key Research and Development Program—"Research and Development of Comprehensive Technology for Prevention and Control of Major Animal Diseases and Efficient and Safe Feeding" (2018YFD0502002); 2019 Chengdu Innovative Research and Development Project—"Research and Development of New Drug and Food Homologous Attractant" (2019-YF-05-01028-SN)

Author Profile: Dong Airong (1994-), female, Tujia people, form Youyang, Chongqing, is studying for a master's degree in animal nutrition and feed science. Email: 1427255635@qq.com

^* Corresponding author: Guo Chunhua (1957-), from Neijiang of Sichuan, is a professor with research interests in animal nutrition and feed science. E-mail: 531893818@qq.com.

                    Lyu Jirong (1976-), born in Ya’an of Sichuan, is has a doctoral degree in animal nutrition and food engineering. Email: lvjirogn468@126.com.