Evaluation of poultry by-product meal replacement with soybean meal on growth, microbial population, rumen parameters, blood and microbial protein synthesis of fattening lambs

Background: By-products can have an important role in supplying livestock feed. Using these resources as a substitute for conventional resources decrease their demand for animal feed. One of the most common sources of demand is soybean meal. Optimal use of poultry by-products meal as a source of protein is one of the suggested solutions to decreases demand for soybean meal. Poultry by-products meal is said to be parts of poultry carcasses that have been milled if dry or wet, such as heads, feet, Intestines and viscera and except for feathers. Note that even in a good slaughterhouse there is a small amount of feather. The fat by more than 16% accelerates the Spoilage of this product, Therefore; it is recommended that the fat of these products should not be more than 10 to 12% (Gheshlagh Oliai et al. 2010; Watson 2006). Its chemical composition depends on the source of raw material, storage time of raw materials before processing, processing method, pressure and temperature during preparation and the amount of ash in the raw material (Jan Mohammadi et al., 1388). In order to use this by-product, the analysis of chemical composition and its effect on animal performance must be studied. The present study aimed to investigate the possibility of replacing protein sources conventional (soybean meal) with poultry by-products meal in the diet of fattening lambs and changes in growth, rumen and blood parameters, microbial population and microbial protein yield. Material and methods: In order to investigate the effect of replacing the waste powder of poultry slaughterhouses with soybean meal, 16 male Dalagh mixed lambs with an average weight of 29 ± 0.5 kg were tested at the research site of the Animal Science Department of Golestan Agricultural Research and Training Center. The experiment was performed in a completely randomized design with 4 replacement levels and 4 replications. The diets of the lambs were adjusted according to the sheep nutritional requirements table (National Research Association 2007), with the same energy and protein levels. The lambs were fed a total mixed ration at two times on day with free access to water. Treatments (diets) included: control (soybean meal), 33% replacement, 67% replacement and 100% replacement of poultry by-product meal with soybean meal. Rumen fluid sampling was performed to measure ruminal parameters including volatile fatty acids, ruminal pH and ammonia nitrogen concentration through the stomach tube 3 hours after feeding. Determination of ammonia nitrogen concentration was measured by phenol hypochlorite (Broderick and Kang, 1980) and volatile fatty acids using gas chromatography. The culture medium PAC was used to count the microbial load (AOAC, 2005) and Protozoa count was performed by Dehoerti (1984) method. Protozoa were counted under a 40% magnification microscope with a neobar slide. Blood samples were taken from Neck veins at the same time as ruminal fluid sampling for the concentration of total protein, urea nitrogen and sugar of blood. measurement of microbial protein yield in the rumen was performed by estimating excreted purine derivatives by Chen and Gomez (1995) method in the end period.Urine was collected for 4 consecutive days. The sample collection containers contained 100 sulfuric acid to keep the pH below 3 and were frozen until the sample was tested. Result and Discussion: At the end of the fattening period, no significant difference was observed in the gain characters: dry matter intake, weight gain of the period, average daily weight gain and feed conversion ratio. Changing the protein source to 10% of dry matter did not affect the palatability of the diet. Its efficacy for fattening indices has also been similar to that of soybean meal. There was a significant difference in blood urea nitrogen (P <0.05) and no significant difference was observed for other blood parameters (glucose and total protein). The comparison of the means between the treatments shows that treatment of 33% has a significant difference with the treatments of 66 and 100%. However, there was no significant difference between the control diet and 100% replacement. Also, blood urea nitrogen concentration was in the normal range. The correlation between NH3H and BUN and the lack of significant differences in blood glucose and protein concentrations indicate that the replacement of soybean meal with poultry by‌product meal in isocaloric and nitrogenic diets in 10% of dry matter has a similar effect on metabolism and physiology. Diet without poultry by-product meal has a higher bacterial population (P <0.01) and comparison of the mean effect of dietary protein source replacement levels on the protozoa population of ruminal fluid was not significantly different. The treatment of replacement 33% showed the highest level of ruminal NH3N (P <0.05). Acetate concentration was not significantly different between treatments and the concentration of propionate for treatment was 33% and 67% higher than other levels (P <0.01). Also, the ratio of acetate to propionate was significantly different (P <0.05). The pH of ruminal fluid for replacement levels was 33% and 67% lower than the control treatment (P <0.05). Replacement of the protein source in the diet with a constant content of nitrogen and carbohydrate concentrations did not alter the ruminal ecosystem. The effect of replacement levels on the mean of microbial protein production was not significantly different. Therefore, by replacing a similar nutrient in the diet and on the other hand, the internal conditions of the body and the tendency for homeostasis can be interfering in the synthesis of microbial proteins. Conclusion: This study showed that the replacement of soybean meal with poultry by-product meal in lambs fattening diets up to 10% of dry matter did not have a negative response on fattening performance, blood and ruminal parameters. Also, it can reduce the demand for soybean meal in the rations.