Effects of supplementation of MultiAct-L® on production performance, egg quality, Newcastle disease antibody titer, antioxidant capacity and gut morphology of laying hens subjected to heat stress in late laying cycle

During the last two decades, the use of antibiotics in poultry diets as animal growth promotors and growth inhibitors of harmful microorganisms has been stopped in different parts of the world (Roth et al., 2019), which led to a decrease in poultry performance and an increase in the prevalence of diseases (Jha et al 2019; Adhikari et al 2020). Researchers have proposed various ways to improve production efficiency, including the use of probiotics, prebiotics, symbiotic, plant extracts, enzymes and organic acids (Gadde et al 2017; Yadav et al 2019). As the age of laying hens increases, the quality of the egg shell decreases, which is due to the increases in weight and size of eggs, the direct effect of age on the structure of the shell, decreased bone calcium uptake and etc (Curtis et al 2005; Curtis 2008). Heat stress has negative effects on the human health and animal performance and product quality. High ambient temperatures cause reduced egg production, egg weight, egg quality (especially egg shell thickness and strength), impaired immunity and poor poultry welfare (Elnagar et al 2010, Ebied et al 2012). The impaired performances of poultry subjected to heat stress (HS) have been associated with a number of factors, including poor appetite and reduced feed intake (due to activation of the hypothalamic-pituitary-adrenal axis), impaired digestion and metabolism, altered endocrine status (increased corticosterone concentration and reduced thyroid hormones concentrations), metabolic shifts at the systemic and cellular levels and changes in body composition (Elnagar et al 2010, Azad et al 2010, Ebied et al 2012, Safdari-Rostamabad et al 2017). Therefore, it is important to design the strategies or ways of minimizing the negative effect of heat stress as part of methods to maintaining egg production, egg quality and poultry welfare. There are several strategies to reduce the effects of heat stress in the laying hens, including use of feed additive, vitamins, organic minerals and antioxidants. In this study, researchers evaluated the effects of MultiAct-L® (Contains probiotics, prebiotics, organic acids, enzymes, organic form of Zn, Mn, Cu, Fe, Co, Cr and antioxidants) on production performance, egg quality, Newcastle disease antibody titer, antioxidant capacity and gut morphology of laying hens subjected to HS in late laying cycle.

Two hundred and sixteen LSL-Lite laying hens (90 weeks of age) were randomly assigned to three dietary treatments with six replicates and twelve birds in each replicate. Dietary treatments were: 1) basal diet based on a corn-soybean meal 2) basal diet with 0.3 % MultiAct-L® and 3) basal diet with 0.5% MultiAct-L®. The birds were exposed to 36±1°C for 6 hours per day. Egg production, egg weight, feed intake, egg mass and feed conversion ratio were recorded weekly and mortality was recorded daily. Egg mass was calculated by multiplying the total number of eggs laid per hens by the average egg weight. At the end of experimental period, one bird from each replicate (close to cage average weight) was slaughtered, and blood samples were taken for analysis. Blood samples were collected from the jugular vein and then serum samples were separated at 3000 ×g for 10 min. Total antioxidant capacity, malondialdehyde, glutathione peroxidase, superoxide dismutase, glucose, cholesterol, triglycerides, uric acid, albumin, calcium and phosphorus were measured using analytical kits. Serum titer to Newcastle disease virus was determined by hemagglutination inhibition test. Villus height, villus width, crypt depth, villus surface area and villus height/crypt depth were measured in the jejunum section of the small intestine. The data were analyzed using the general linear model procedure of the SAS (2003). The Duncan multiple range test was used to determine the significant differences between treatment means.

MultiAct-L® did not affect the body weight gain of laying hens (P>0.05). The results also showed that feeding MultiAct-L® enhanced the feed intake, egg production, egg weight and egg mass (P<0.05). Feed conversion ratio was improved and mortality was lower in the treatments receiving 0.3 or 0.5% MultiAct-L® than the control group (P<0.05). In agreement with our findings, Deng et al. (2012) and Zhang et al. (2017) reported the significant increase of egg production, feed intake and egg weight by dietary supplementation of probiotic in laying hens subjected to HS. Supplementation of 0.3% MultiAct-L® to diet decreased the abnormal eggs (P>0.05). Shape index, Haugh unit, yolk weight, albumen weight, shell weight, shell thickness and egg specific gravity were not affected by dietary treatments (P>0.05). Similarly, Bozkurt et al. (2012) showed that egg quality parameters weren’t affected by dietary supplementation of essential oil or mannan oligosaccharide in laying hens subjected to heat stress. MultiAct-L® supplement did not significantly affect the titer of antibody against Newcastle disease virus at days 10 and 30 post-vaccination (P>0.05). There was no significant difference in the total antioxidant capacity and glutathione peroxidase among experimental treatments (P>0.05); however, dietary MultiAct-L® supplementation had increased the superoxide dismutase levels and decreased malondialdehyde levels in serum (P<0.05). Blood glucose, cholesterol, triglycerides, uric acid, albumin, calcium and phosphorus in experimental treatments were not significantly different between the control group and the MultiAct-L®-treated groups (P>0.05). No significant changes in villus height, villus width, villus surface area, crypt depth and villus height to crypt depth ratio were observed between three groups at the end of the 8 weeks experimental period (P>0.05). Similarly, Deng et al. (2012) showed that villus height, villus width, crypt depth in the ileum weren’t affected by dietary supplementation of probiotic in laying hens subjected to HS.

As for the results of this study, Multiact-L® could improve laying performance and antioxidant status in laying hens subjected to heat stress during the late laying period.