تاثير اندازه ذرات سيلاژ علوفه كامل جو و سطح كنسانتره بر مصرف و هضم جيره‌ها، ابقاء نيتروژن، توليد پروتئين ميكروبي و رفتار مصرف در گوسفند كرماني

The effect of barley silage particle size and concentrate levels on physical characteristics, dietary intake and digestibility of diets, nitrogen retention, microbial protein synthesis and eating behaviors in Kermani sheep

زمينه مطالعاتي: در ايران سيلاژ علوفه كامل جو بسيار كم­تر از ديگر سيلاژها مورد توجه بوده است. هدف: اين آزمايش به منظور تعيين تاثير دو سطح اندازه ذرات سيلاژ علوفه كامل جو و دو سطح كنسانتره بر مصرف، قابليت هضم، توليد پروتئين ميكروبي و رفتار مصرف خوراك در گوسفند كرماني انجام گرفت. روش كار: حدود 1200 كيلو­گرم علوفه جو در زمان سبز` بودن ساقه و خميري بودن دانه، با چاپر در دو اندازه 24 و 12ميلي­متر خرد شدند و در كيسه ­هاي نايلوني سيلو شدند. پس از 45 روز سيلوها باز شدند و ويژگي­هاي فيزيكي و ارزيابي ظاهري نمونه­ هاي جو سيلويي انجام گرفت. جيره­ هاي آزمايشي عبارت بودنداز: 1) 40 درصد سيلاژ علوفه كامل جو درشت و 60 درصد كنسانتره، 2) 60 درصد سيلاژ علوفه كامل جو درشت و 40 درصد كنسانتره، 3) 40 درصد سيلاژ علوفه كامل جو ريز و 60 درصد كنسانتره، 4) 60 درصد سيلاژ علوفه كامل جو ريز و 40 درصد كنسانتره. نتايج: سيلوها در ارزيابي ظاهري اختلاف معني­ داري نداشتند، ولي pH در سيلاژ علوفه كامل جو ريز، به صورت معني­ داري كم­تر بود ( ۰/۰۰۳ = p ). عامل موثر فيزيكي و الياف موثر فيزيك در جيره­ هاي داراي سيلاژ علوفه كامل جو درشت بيشتر بود. مصرف ماده خشك در جيره­ هاي داراي 60 درصد كنسانتره بيشتر بود، ولي مصرف الياف نامحلول در شوينده­ ي خنثي و قابليت هضم ماده خشك تحت تاثير سطح كنسانتره و اندازه ذرات جو سيلويي قررار گرفت. ابقاء نيتروژن در جيره­ هاي سيلاژ ريز بيشتر بود (۰/۰۲۲­­=­p). زمان­ هاي مصرف، نشخوار و جويدن و در جيره­ هاي داراي سيلاژ درشت بيشتر بودند. نتيجه­ گيري نهايي: بيشترين قابليت هضم ماده خشك و آلي در جيره داراي 40 درصد كنسانتره و سيلاژ علوفه كامل جو ريز بود، زيرا با كاهش اندازه ذرات سيلاژ به سطح تماس ميكروبي در شكمبه افزوده شد.

Introduction:In Iran, Barley silage is considered much lower than the other silages. Barley can provide perfect fodder for ruminants in early spring, when other forage are not available.This experiment was conducted to deter mine the effects of barley silage particles size and levels of concentrate on feed intake, digestibility, nitrogen balance microbial protein Synthesis and eating, Rumination and chewing activity in Kermani sheep . Material and methods: The experiment was carried out in sheep farms of Department of Animal Science, Shahid Bahonar University of Kerman. Iranian conventional varieties of barley grain was grown in the farm of agricultural faculty in November 2011 . About 1200 kg of barley fodder were harvested in green stems and doughy seeds condition, and chopped in sizes 24 and 12 mm and was ensiled in plastic bags without any additives . Silos were opened after 45 days and evaluate the physical properties and visual appraisal of barley silage. Experimental die ts were: 1) 40 percent coarse barley silage and 60 percent concentrate 2) 60 percent coarse barley silage and 40 percent concentrate 3) 40 percent fine barley silage and 60 percent concentrate 4) 60 percent fine barley silage and 40 percent concentrate. Four mature male sheep weighing 52±4/0 were used in the experiment. Sheep were kept in metabolic cages and had free access to feed and fresh water and were assigned randomly to 2×2 factorial dietary treatments in a changeover design experiment. The experiment consisted of four periods , the experimental periods were 21 d each and included an adaptation period (d 1 to 14), a data collection period (d 15 to 20) and chewing behavior (d 21). Results and discussion : There was no significant difference in visual appraisal of silages , however pH was lower in fine barley silage (P=0.003 ). The pef, peNDF and geometric mean were higher in coarse barley silage diets.Dry matter intake was influenced by the levels of concentrate ( p=0.02) and were higher on diets with 60% concentrate, but barley silage particles size had no effect on dry matter intake. NDF intake was influenced by the silage particles size and concentrate levels and was the lowest in the diet of 60% concentrate and fine barley silage particle size (p=0.05).Dry and organic matter digestibility were influence by barley silage particles size and concentrate levels, the highest dry and organic matter digestibility were in diet of fine silage particle size and 40% concentrate level (P<0.05).Crude protein and NDF digestibility weren’t affected by silage particles size and concentrates levels. Nitrogen intake was affected by concentrate levels, and the lowest nitrogen intake was in diet of coarse barley silage and 40% concentrate (P<0.05). But nitrogen retention was higher in fine silage particles size diets (P<0.05).Microbial protein synthesis in the rumen, were affected by barley silage particles size (P=0.044) and concentrate levels (P= 0.024), microbial protein synthesis increased with the silage particles size reduction and increased levels of concentrate. Also, the synthesis of microbial protein in the rumen increases in low physically effective fiber diets, the protein degradation rate was increased and amount of non -degradable protein in the rumen was decreased with decreasing forage particles size. Also, the synthesis of microbial protein in the rumen increases in low physically effective fiber diets,Because of the decrease protozoa and reducing recycling nitrogen in the rumen (Yang and Beauchemin 2006 ).Vakil Faraji et al (2009) reported an increase in concentrate in the diet causes an increase in protein production in the rumen. This increase may be due to increased organic matter digested in the rumen as a result of increasin g levels of concentrate to forage. Eating time (minutes per day) in the diets of coarse barley silage was higher (P=0.001). Eating time increased linearly with increasing forage particle size (Kononoff et al., 2003; Yang and Beauchemin , 2006). Also eating time increases with an increase in the geometric mean particles size of forage ( Leonardiet al. 2005).Eating time per kg of dry matter and NDF intake was higher in diets of coarse barley silage (P=0.004 and p=0.001 respectively), Kononoff et a l. research results (2003) and Teimouri Yansari et al. (2004) showed that the eating time per kg of dry matter was affected by forage particle size and decreased with reducing forage particle size . The interaction was significant between the size of barley silage and two levels of concentrate on the time of eating per kilogram of dry matter intake, because in the coarse barley silage the eating time was reduced by decreasing the concentrate level while in diets of fine silage, this time increased by decreasing concentrate levels. Zebeli et al. (2006) and Yang and Beauchemin (2007) showed that eating time was reduced per kilo of NDF by reducing the size of forage particles size . The ruminating time (mi nutes per day) was higher in coarse silage diets (P=0.005), Probably the reason for the increase in Ruminating time was due to decrease in rate of passage of large particles of silage through the rumen and high rumen retention time (Firkins et al., 1998). Coarse forage fibers have a great effect on the formation of rumen mat and stimulate Ruminating and ruminal movements (Mertens 1997). Therefore, the rumen mat is very important in adjusting the retention time of small particles in the rumen by selective ru minal Persistence (vansoest 1994). The Ruminating time per k g of dry matter and NDF (minutes ) was higher in coarse silage diets (P<0.05). Forage particles larger than 1.18 mm have the highest resistance to rumen passage and are responsible for the Inducing of ruminat ing (Mertens 1997) . Chewing time (minutes per day) was higher in coarse silage diets (P= 0.001), a lso, the chewing activity time per k of dry matter and NDF was affected by the size of the silage particles size. It has been reported th at by increasing the effective physical fiber, the total chewing and Ruminating time increased linearly (Yang and Beauchemin 2006). Conclusion : The highest dry and organic matter digestibility were in 40 percent concentrate and fine barley silage diet, because contact with the rumen microorganism was increased with the silage particle size reduction.