Evaluation of kefir as a potential probiotic on growth performance, serum biochemistry and immune responses in broiler chicks

摘要

Abstract This experiment was conducted to evaluate the effect of milk or molasses kefir as a probiotic on growth performance, carcass traits, serum biochemistry and humoral immune responses in broiler chickens. A total of 192 one-d-old as hatched broiler chicks (Ross 308) were randomly allotted to 4 treatments, each with 4 replicate pens of 12 chicks. The following treatments were applied: 1) a basal diet (C) and normal drinking water, 2) 2% milk kefir in drinking water, 3) 2% molasses kefir in drinking water, and 4) the diet C supplemented with commercial probiotic. At d 42, eight birds per treatment were killed for determination of carcass traits. Broilers at 28 days of age were bled for measuring antibody titers against Newcastle disease virus (NDV) and avian influenza virus (AIV), at 30 days of age for antibody titers against sheep red blood cell (SRBC), and at 42 days of age for biochemical analysis. Supplementing 2% milk kefir increased body weight of broilers at 28 and 42 days of age ( P ?0.05) influenced. Broilers supplemented with molasses kefir, had a significantly lower concentration of serum total cholesterol, low density lipoprotein cholesterol and elevated high density lipoprotein cholesterol at 42 days of age ( P Keywords Antibiotic ; Milk kefir ; Molasses kefir ; Multi-strain probiotic ; Broilers prs.rt("abs_end"); 1. Introduction Antibiotic growth promoters have been successfully used in subtherapeutic dosage to promote growth and protect health of chickens in poultry industry since 1940 ( Landy et?al., 2011a , Landy et?al., 2011b , Landy et?al., 2012 , Fekri Yazdi et?al., 2014a , Fekri Yazdi et?al., 2014b , Nanekarani et?al., 2012 and Goodarzi et?al., 2014 ). Antibiotic growth promoters were supposed to promote muscle growth in the poultry as a result of improved gut health, resulting in better digestion of feed ( Visek, 1978 ). However, there is a fear that wider use of antibiotics as feed additives can lead to the development of antibiotic resistant bacteria, which poses a potential risk for humans if it is transferred ( Nasir and Grashorn, 2006 and Toghyani et?al., 2010 ). Thus, efforts have been made in different parts of the world to limit the use of antibiotics in livestock production. Because of the ban on the use of antibiotics, there is growing demand for natural alternative substances, which can sustain or promote growth performance and prevent disease. Consequently, probiotics and prebiotics, phytogenic and herbal products have received increased attention as possible antibiotic growth promoter substitutions ( Landy and Kavyani, 2014 , Gibson and Roberfroid, 1995 and Landy et?al., 2012 ). Probiotics have been defined as micro-organisms which favor intestinal microflora balance ( Fuller, 1989 ). Our previous study indicated that supplementing broiler reared under heat stress condition with a multi-strain probiotic (Primalac) could induce favorable influences on performance, immune responses and cecal microflora ( Landy and Kavyani, 2014 ). Kefir belongs to the probiotic group and it's a popular Middle Eastern drink. It's milk or molasses production fermented by the action of Lactobacillus ( Lactobacillus lactis , Lactobacillus helveticus , Lactobacillus casei ), Streptococcus ( S . cremoris , S . lactis ) and yeasts ( Otles and Cagindi, 2003 ). Kefir possesses proteins, polysaccharides, ethyl alcohol, lactic acid, fat, minerals and vitamins ( Magalh?es et?al., 2011 ). Cho et?al. (2013) showed that orally administration of milk kefir would improve growth performance and benefit meat quality in broiler chickens. Thoreux and Schmucker (2001) observed the beneficial influence of milk kefir on specific mucosal immune response against cholera holotoxin in rats. Furthermore, Cenesiz et?al. (2008) observed the positive effects of milk kefir on performance and serum biochemistry of broiler chicks. Despite these findings, most of researches in this field have focused on the growth promoting effects of milk kefir and less attention has been given on kefir effects on humoral immune responses of broiler chicks. Also, so far there has not been any comparison between milk and molasses kefir in broilers. The aim of the present study was to examine the effect of milk and molasses kefir as a probiotic on growth performance, carcass traits, serum biochemistry and humoral immune responses in broilers and to ascertain the importance of fermentations culture on these responses. 2. Materials and methods 2.1. Kefir preparation Bovine milk was purchased and heated to 80°C for 30?min in water bath, before cooling to inoculation temperature. The heat-treated milk and molasses were fermented separately by the addition of kefir grains at 20°C for 2?d. After fermentation, kefir was filtrated to remove the kefir grains. 2.2. Animals and dietary treatments Procedures performed in this trial were reviewed and approved by the Animal Care Committee of University of Isfahan. A total of 240 one-d-old Ross 308 broil