Raja Sekhar Reddy, A(MAJOR)Ravinder Reddy, VShyam Sundar, GNaga Lakshmi, DReddy, Y.NVIJAYA LAKSHMI, K2018-11-132018-11-132011-08http://krishikosh.egranth.ac.in/handle/1/5810083371THESESABSTRACT : Antibiotics are used in poultry feeds for antimicrobial effect, and also for growth promotion, but are now banned because of drug resistance and residual effects through egg and meat consumption. As feed acidifiers, organic acids (C1-C7) are associated with antimicrobial activity and growth promotion, and therefore considered as valuable replacers for antibiotics. However, the studies conducted so far on organic acids projected variable results, primarily due to pKa values and molecular weights that determine the antimicrobial and growth promoting effects. In order to examine the expression of organic acids, a series of trials in vitro and in vivo were under taken with closely (Propionic acid -PA and Butyric acid-BA) and remotely related (Lactic acid -LA and Citric acid-CA) acids to decipher information on their utility in broiler chicken. PA and BA with relatively high pKa and low molecular weight, were expected to possess higher antimicrobial effect and hence, their inclusion levels were kept low (0.1% - 0.3%) in diets, and conversely for LA and CA (1-3%). In vitro experiments exhibited growth inhibition of E.coli (serotype O: 109 at 106CFU/ml) with all levels of PA and BA (0.1, 0.2 or 0.3%) and, LA and CA (1, 2 or 3%) inclusion in diets compared to the control. The antimicrobial effect was more pronounced at pH 4 within 5 h, which continued up to 24 h, and the vice versa at pH 7.4, indicating a complimentary effect between the organic acids and low pH in reducing the E.coli count. Oral administration of E.coli culture into the crop at 21d of age reduced body weight, FCR and livability of broilers at 42 d, which was effectively corrected by organic acids. These organic acids significantly reduced the bacterial load in duodenal digesta by 3.6 -7.7% compared to antibiotic and control diets, the maximum decline was observed with PA. The in vivo trials with PA or BA inclusion in diets significantly (P<0.05) enhanced broiler body weights (8-10%), FCR, tibia weight, tibia length, breast muscle, intestinal growth, immune response, lymphoid organ weights, and reduced abdominal fat (7.5%) compared to AB and control diet. PA or BA at 0.2% level was either more effective or equivalent to 0.3% level and hence, the former can be used in broiler diets. Organic acids stimulated the growth of small intestine, increased villi length, crypt width and improved goblet cell activity (duodenum), the maximum being with BA, which enhanced nutrient absorption and growth over antibiotic and control diets. Similarly, LA or CA at 2% level improved body weight (9.6-10.9%) and FCR (7.75 - 8.9%) compared to AB and control diets. LA produced higher meat yield (3.1%), breast meat (9.7%) and small intestine weight (45%) compared to control, and decreased abdominal fat. LA or CA in diets maintained significantly low pH in the crop (4.45), proventriculus (3.15) and gizzard (2.38) than the AB diet implying better absorption of nutrients from the gut, due to acidification. The histological studies of duodenum revealed a moderate mono nuclear cell infiltration in duodenal villi and intense activity of goblet cells due to dietary acidification. Further, the feeding trials involving different levels of Ca: P (0.9:0.45%; 0.7:0.35%; 0.5:0.25%) with organic acids, antibiotic and control diets revealed a complementary effect between moderately low level of Ca: P (0.7:0.35%) and organic acids measured in terms of broiler growth, FCR and leg scores, serum Ca: P concentrations and protein deposition in breast muscle that were on par with Ca: P at 0.90:0.45%. Diets with Ca: P at 0.90:0.45% level and BA produced maximum Ca retention in tibia, while PA influenced higher P retention. The extent of decline in bone measures and mineralization due to low Ca: P (0.5:0.25%) was considerably reduced by the intervention of organic acids compared to AB and control diets. The influence of organic acids was also reflected from the sustained higher serum Ca (21%) and P (32.1%), besides that in bone (Ca>4.6% and P>10.5%) compared to antibiotic and control diets. The apparent digestibility of nutrients, particularly that of protein, Ca and P was higher with acidified diets. Interestingly, the digestibility of protein, Ca and P was inversely related to the levels of Ca: P in diet. Organic acids in combination with Ca and P at 0.9:0.45% level supported more protein accretion and less fat deposition in breast muscle and liver tissue. LA and CA in diets enhanced breast meat yield (5.6%), reduced abdominal fat (18.7%) and serum cholesterol (11%) compared to the control diet. It can be concluded that individually all organic acids (Propionic, Butyric, Lactic and Citric acids) effectively sanitized the upper GI tract from E.coli, better than antibiotics, and significantly enhanced broiler performance at 35 and 42 d of age. The ideal inclusion levels of PA or BA (0.2-0.3%) were low compared to LA and CA (2-3%), primarily due to pKa values and molecular weights. Organic acids maintained suitable environment in the intestine and stimulated its morphological and histological growth, which supported higher nutrient absorption, broiler growth, breast meat with more percentage of protein, less water and low fat content and higher Ca and P retention. The antibiotics can be effectively replaced from feed with organic acids.ennullThesis