Abstract :

T

his experiment was carried out in the New valley Governorate during May tell September 2016 in privet farm. Twelve crossbreed beef bulls average 252.98 to 255.66 kg body weight (BW) were used in this study. Animals were divided randomly into three groups (4 animal/group). The first group (G1) served as control. The second and the third groups (G2 and G3) were supplemented with commercial probiotics at a rate of 0.5 to 1.00 gm/ kg of concentrate mixture, respectively. The animals were fed individually on concentrate fed mixture, berseem hay and wheat straw to cover the requirement of DM and TDN for average body weight and daily gain of beef. Experimental period lasted 150 days. Digestibility coefficients of different nutrients and nutritive values (TDN and DCP %) of the experimental rations were calculated. Blood samples were collected from each animal at day 0, 75 and 150 of experiment period. Serum samples of all animals were assayed for determenation of triiodothyronine (T3), thyroxine (T4), total protein, albumin, glucose, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations. Body weight (BW) of animals was recorded at the beginning of experimental period and monthly thereafter. Total gain, daily gain and daily average feed intake were calculated. Thus, value of feed efficiency was calculated. Monthly average of ambient temperature, relative humidity and temperature humidity index were calculated during the experimental period. Monthly of THI values in the present study during experimental period from May to September recorded more than 74. Thus, animal suffered from heat stress. Also, the present results indicated that supplementation of probiotics in the diet of beef bulls led to positive effect on rectal temperature and respiration rate in G3 and G2 compared to control group G1. Values of rectal temperature and respiration rate during experimental period were decreased in G2 and G3 as a result of supplementation of probiotics in comparison with G1, but the differences were not significant. The present results indicated beneficial effect of feeding beef bulls on diets supplemented with probiotics to eliminate heat stress. Digestibility coefficients of different nutrients improved in treatments. The best values of digestibility coefficients of nutrients were recorded in G3 followed by G2 and the lowest values were recorded in control group (G1). Also, supplementation of probiotics led to significant (P<0.05) effect on total digestible nutrients (TDN) and digestible crude protein (DCP) in G3 in comparison with G2 and G1. Final BW of beef bulls and daily gains recorded the higher value in G3 followed by G2 and the lower value of was recorded in G1. At the same time, feed intake and feed efficiencies in G3 recorded higher values in comparison with G2 and G1. The results indicated that the mean concentrations of total protein, albumin, glucose, AST, ALT, T3 and T4 were increased in G2 and G3 in comparison with G1. The present results illustrated that improvement of net profit as a result of supplementation probiotics in G2 and G3. From the present results it can be concluded that supplementation of probiotics in the diet of beef bulls improved growth performance, nutrient digestibility and physiological response under heat stress conditions. Such improvement is due to a positive effect on blood metabolites parameters as physiological responses

Keywords: probiotics, growth, digestibility and physiological responses, heat stress, beef bulls

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