| چکیده انگلیسی مقاله |
Introduction and objective: Food and nutrition are undoubtedly the most important topic of discussion in today's world. Increasing population and efforts to meet the nutritional needs of the next generation necessarily require effort and pursuit in various fields of agriculture, animal husbandry and related sciences. Small ruminants are especially important in rapidly improving the nutrition of the world's growing population. The advantage of small ruminants is short generation distance, faster growth rate, and greater adaptability and tolerance to environmental conditions than large ruminants. One of the most important food items used in ruminants nutrition is cereal straw. Cereal straw has high levels of lignin and silica, both of which play an important role in lowering its digestibility and nutritional value. In Iran, the use of ordinary straw in animal feed is common and in fact farmers are more inclined to use straw due to lack and high cost of forages such as alfalfa or corn silage, although they are aware of its low effectiveness in the production of livestock products. One of methods to increase the digestibility of wood products is to increase the nitrogen available to the microbes that break down the fibers. The nutritional value of cereal straw can be increased by processing and using urea as a source of ammonia. Conventional processing of grain straw with urea in the country is a costly, difficult, and time-consuming method. The use of a machine is essential to facilitate or eliminate some of these operations. Lime also has been shown can improve the usability of low quality forage sources by increasing availability of nutrient for rumen micro-organisms. Based on our knowledge, there is little experiments has been done regarding the simultaneous use of lime and urea in the processing of wheat straw and its effects on the performance of fattening lambs. Therefore, this study was conducted with the aim of investigating the processing of wheat straw by different methods and their effect on the digestibility, NDF degradability, dry matter intake and performance of Qezel fattening lambs.
Materials and methods: This experiment was performed on 36 fattening Ghezel lambs with an average weight of 30 kg and 3 months of age in a completely randomized statistical design. Experimental treatments include, control (feeding with diet containing unprocessed wheat straw), feeding with diet containing 5% urea processed wheat straw, feeding with diet containing 5% lime processed wheat straw and feeding with diet containing 5% urea + 5% lime processed wheat straw. Dry matter intake, weight gain, feed conversion ratio, DM, OM and CP digestibility, fecal score and blood parameters of experimental groups were determined. Also uNDF content of raw and processed wheat straw measured with standard method.
Results: Wheat straw processing with urea or lime led to a decrease in feed consumption, but processing with a combination of urea + lime did not affect the total feed intake. At the first month of fattening period – considering a two weeks adaptation - feed consumption showed large fluctuations among the experimental groups, which was partly related to the nature of the feed and kind of processing and partly related to the disease of some experimental animals. In the second month, feed consumption had a more stable trend, and the control and lime + urea groups had more feed consumption than the other two treatments. The consumption of feed dry matter showed a significant decrease in the two-month period in the treatments of straw which processed with urea or lime compared to the other two groups. In accordance with the fluctuations of the consumed feed, the weight gain of the lambs also showed a fluctuating trend during the two months of the experiment. The total weight gain was not different among the experimental treatments, however the control and urea + lime groups had considerable - however non-significant - more weight gain than the other two groups. The feed conversion rate did not show any difference between the experimental groups. Diet containing straw processed with lime + urea had the highest digestibility of organic matter, NDF and ADF. Also, this diet along with urea group had the highest digestibility of crude protein and fat. Blood glucose significantly affected by the treatments and urea and lime groups had lower blood glucose compared to the other treatments. Blood protein was not affected by the experimental treatments, but at the end of the fattening period blood urea nitrogen was higher in the urea + lime group than in other treatments. During the first 20 day of the fattening period, the fecal score in the lambs of the control treatment was higher than the other treatments, although no difference was seen between the lambs receiving straw treated with urea, lime and the combination of urea + lime. Also, during the second and third 20 days of experiment, the fecal score was not different among the treatments. Processing straw with a urea + lime significantly reduced the amount of undigested neutral detergent fiber (uNDF).
Conclusion: wheat straw processing with urea + lime led to the highest level of feed and NDF digestibility. Despite the higher weight of the lambs and more feed consumption, the performance of fattening animals did not differ statistically. It seems that more research should be done in this field. |