Introduction[1]: The fodder used in animal feed is in the form of silage, crushed and pellets. If used a a pelleted form, the animal will spend less time for eating so the activity and the maintenance requirements will be decrease. Part of the improvement in pellet diet is due to less energy consumption during feeding. In other words, the use of pellet rations reduces the energy consumed by the animal for eating and also increases the availability of vital nutrients and energy (Fluharty et al., 2017). Alfalfa is one of the forage plants that can produce more than two tons of protein per hectare per year. Pelleted alfalfa is a perfect feed for dairy cows, sheep and goats, horses, camels, rabbits and other livestock animals as it improves their performance and production (Fluharty et al., 2017).The activities of ruminal protozoa contribute significantly to the digestion of plant cell wall polymers and their absence from the rumen may have a negative effect on the extent of fiber digestion. Fiber-degrading enzymes include total cellulase activity, carboxymethylcellulase, and microcrystalline cellulase. The activity of these enzymes is in three separate parts of the rumen contents, including tiny particles (microbes attached to the rumen particle), intracellular part (cells that are freely suspended in the liquid part of the ruminal fluid) and extracellular part (enzymes in the liquid part) are measured (Agarwal et al., 2000). The aim of this study was to investigate the effect of alfalfa physical shape and barley grain processing on nitrogen retention, activity of enzyme cellulolytic, blood parameters and rumen microbial population in Dalagh breed fattening lambs.
Materials and Methods: Thirty male lambs with an approximate age of 3.5±1.2 months with an average weight of 17 ± 1.1 kg were used. The experiment was statistically analyzed in the form of a factorial experiment based on a completely randomized design with two factors. The experimental variables include: physical form of forage (chopped vs. pelleted form) and barley grain processing (whole vs. grounded vs. steam flaked). The experiment was performed in the 98 days (14 days of habituation and 84 days of the main course) with 6 treatments and 5 replications. Experimental diets were equal in protein and energy content and includes: 1- Pelleted alfalfa with whole barley grain 2- Pelleted alfalfa with ground barley grain 3- Pelleted alfalfa with flaked barley grain 4- Alfalfa with whole barley grain 5-Alfalfa with ground barley grain 6 -Alfalfa with flaked barley grain. Rumen fluid was sampled on day 84 at 3 hours after feeding and blood samples were taken from the lambs in the penultimate week of the fattening period 3 hours after morning feeding from the cervical vein.
Results and Discussion: Nitrogen consumption and fecal extracted nitrogen in lambs feces were significantly affected by the physical shape of the forage, which nitrogen consumption and fecal nitrogen excretion in lambs fed with pelleted alfalfa compared to chopped alfalfa were increased (P<0.05).  The processing of barley grain didn’t significant effect on apparent nitrogen balance parameters (P>0.05). The total number of rumen bacteria, lactic acid, coliform and rumen protozoa were not affected by the physical form of the forage (P >0.05). However, the number of total bacteria and rumen protozoa in lambs fed with flaked barley grain were higher than milled barley grain and also in milled barley grain were greater than whole barley grain (P<0.05). Activity of carboxymethyl cellulase and microcrystalline cellulase enzymes in intra cellular, extra cellular, solid and total rumen fluids of lambs fed pelleted alfalfa forage and flaked barley was higher than chopped alfalfa, however, there was no significant difference between treatments (P >0.05). The blood glucose of lambs was significantly higher in lambs fed by flaked barley than milled barley and in milled barley was higher than whole barley grain (P<0.05) The blood urea nitrogen of lambs was significantly lower in lambs fed by flaked barley than milled barley and in milled barley was lower than whole barley grain (P<0.05).
Conclusion: The results of our experiment showed that the use of pelleted alfalfa and flaked barley grain in the diet of fattening of lambs due to numerical increasing trend in digested nitrogen, statistical reducing of urea nitrogen and numerical increasing trend in total rumen bacteria and cellulase enzymes activity had the best performance of rumen, which ultimately ensures the health of livestock. For recommendation using pelleted form of forage and flaked barley grain for farmers is required more study to investigate rumen and post rumen digestion rate of nitrogen and also, the cost of processing. While the lamb performance increase compared to the cost of processing, it can be recommended to the farmer to instead of consuming alfalfa and barley grain as a traditional way, use the processed form of them to improve the efficiency of the use of nutrients and increase the performance of the animals.