Effects Of Yucca On Broiler Performance Under Heat Stress

Due to the influence of the greenhouse effect,heat stress has become an important adverse factor restricting the development of modern poultry farming.Due to the prohibition of the addition of antibiotics,the development of green anti-heat stress additives with no toxic,no side effects and no residues will became the research focus about heat stress for scholars afterwards.In addition to its strong ammonia-reducing and deodorizing function,Yucca can also effectively improve the utilization rate of nutrients,improve the health of the body,resist stress,and improve the breeding efficiency.Glutamic acid(Glu)is one of the amino acids that make up protein and is the main energy source of the intestine.It has a protective effect on the gastrointestinal tract.As a precursor of other substances,it plays many physiological functions.In this study,according to the climate characteristics of high temperature and humidity in summer,yucca and Glu were applied to broilers in the growing period under high temperature conditions to explore their effects on heat-stressed broiler performance,serum corticosterone,nutrient metabolism and feeding regulation.In this study,360 28-day-old(d)broilers(males)were selected and randomly divided into 6 groups(suitable temperature group: Ⅰ,Ⅱ,Ⅲ group,high temperature group: Ⅳ,Ⅴ,Ⅵ group),with 6 repeats in each group and 10 chickens per repeat.Among them,groups I and IV were fed basic diets,groups II and V were fed with 100 ppm Yucca basic diets,and groups III and VI were fed with 100 ppm Yucca and 0.5% Glu based diet.Suitable temperature group temperature: 24±2℃,high temperature group temperature: 8:00-19:00,controlled at 34℃±2℃,19:00-8:00(the next day)to maintain room temperature.The test period is 4 weeks.The results show that high temperature can significantly reduce the average daily gain(ADG)and average daily feed intake(ADFI)of broilers at various growth stages,while increasing feed conversion ratio(FCR)(P<0.05).Adding 100 ppm Yucca alone,100 ppm Yucca and 0.5% Glu in the diet can effectively alleviate circulating heat stress negative impacts on growth performance.Pre-heat exposure had no significant effect on serum glucose,triglyceride and uric acid level(P>0.05),significantly reduced serum triglyceride levels at 49 d,significantly increased uric acid levels at 42 d and 56 d(P<0.05),and significantly increased high temperature 35 d serum corticosterone level(P<0.05);adding 100 ppm Yucca to the diet can reduce the increase of serum corticosterone level(P<0.05).In the early stage of the experiment,high temperature can reduce the serum NPY concentration of broilers,increase the serum CCK,Ghreln,Leptin concentration,and reduce the expression of hypothalamic’s NPY m RNA(P<0.05);add 100 ppm Yucca to the diet to reduce the serum Leptin concentration caused by 35 d and 42 d high temperature(P<0.05);100 ppm Yucca and 0.5% Glu can significantly reduce the serum Leptin concentration at 35 d(P<0.05).High temperature has no significant effect on liver glycogen(P>0.05);high temperature can significantly increase ACC enzyme activity at 35 d,G6P enzyme activity at 35 d and 42 d,liver ACC m RNA expression at 56 d,and reduce liver G6 P m RNA expression at 42 d and 49 d(P<0.05);adding 100 ppm Yucca to the diet can slow down the expression of G6 P m RNA in the liver caused by high temperature for 49d(P<0.05),and adding 100 ppm Yucca and 0.5% Glu to the diet can significantly increase the temperature at 35 d,42 d,and 49 d.Liver G6 P enzyme activity(P<0.05).In summary,adding 100 ppm Yucca or 100 ppm Yucca and 0.5% Glu to the feed can alleviate the heat stress of broilers to a certain extent,increase feed intake,reduce feed-to-meat ratio,and improve production performance;this may be due to the Saponin of Yucca as Corticosterone analogues can competitively bind corticosterone to a certain extent,thereby affecting other physiological functions,thereby alleviating heat stress.The test results provide a theoretical basis and reference basis for the development and promotion of green anti-heat stress additive products.