بررسي اثر جايگزيني گياه سوبابل (Leucaena leucocephala) به جاي يونجه بر عملكرد بزهاي شيرده نجدي

The Substitution Effect of Subabul (Leucaena leucocephala) with Alfalfa on Digestibility, Ruminal Fermentability, Chewing Behavior and Blood Metabolites of Najdi Goat

اين آزمايش به منظور بررسي جايگزيني گياه سوبابل به جاي يونجه بر هضم و تخمير شكمبه اي، فعاليت نشخوار و فراسنجه هاي خوني 8 راس بز نجدي ماده با ميانگين وزن زنده 2± 35 كيلوگرم و سن 2±24 ماه انجام شد. دام ها با جيره شاهد و جيره حاوي سوبابل (جايگزيني با 50 درصد يونجه) براي مدت 40 روز تغذيه شدند. نتايج نشان داد كه ماده خشك مصرفي در تيمار شاهد بالاتر از تيمار حاوي سوبابل بود (P<0.05).

Introduction: Subabul (leucaena leucocephala) is a multipurpose leguminous tree in the tropics and high-quality feed resource for ruminants especially during the dry season in most tropical and subtropical areas. Its leaf has high content of N (16 - 23 % crude protein) and Ca، a low content of tannins and phenolic compounds. The researchers reported dietary supplementation with leucaena silage could enhance feed intake، digestibility، and rumen fermentation in dairy steers. Therefore، this experiment was conducted to investigate the effect of subabul as a replacement for alfalfa on rumen fermentation and digestion، rumination and blood metabolites of Najdi goat. Materials and Methods: The eight Najdi goats with average body weight average of 35 kg that were fed with the control diet and diet containing subabul (50 percent of alfalfa) for 40 days. Animals were randomly treated with four replications. Forage to concentrate ratio was 50 to 50. The leave of subabul were collected from Mollasani and milled. Diets fed twice per day for 40 days. Daily feed intake، nutrient digestibility، rumen and blood parameters and rumination activity was recorded. Rumen fluid was collected from animals before the morning feeding. About 200 mg sample (1.0 mm screen) incubated with 35 ml buffered rumen fluid under continuous CO2 reflux in 100 ml vials for 2، 4، 6، 8، 10، 12، 16، 24، 48، 72 and 96 h، in a water bath maintained at 39°C. Cumulative gas production data were fitted to the exponential equation Y=B (1−e−Ct). Partitioning factor، microbial biomass، actually degradable organic matter was calculated by Makkar. Digestibility of dry matter and NDF of the samples were determined. Data were subjected to analysis as a completely randomized design using the General Linear Model (GLM) procedure of SAS. Results and Discussion The results showed that the dry matter intake in goats fed with control treatment was more than treatment containing subabul (P<0.05). There is not any difference in digestibility of dry matter، NDF and crude protein، rumen ammonia nitrogen and pH between treatments. Time to eating، ruminating and chewing and each of them per DM and NDF were not different. However time of eating، ruminating and chewing for crude protein of diet containing subabul was more than control diet (P<0.05). There was no difference between treatments for blood glucose، urea nitrogen، cholesterol and triglyceride. Potential of gas production and microbial biomass production of wheat straw in control and subabul diets were not different but partitioning factor and microbial biomass efficiency was significant (P<0.05). Potential of gas production، partitioning factor، production and microbial biomass efficiency of soybean meal and DM and NDF digestibility of wheat straw were not different between treatments but DM and NDF digestibility of soybean meal were significantly different between treatments (P<0.05). Legumes because of high quantity of protein and carbohydrate and lower fiber can be used as a suitable substrate for rumen microbial growth. But some studies reported that the presence of tannin، caused to reduce gas production. Because tannins tend to make a complex with nutrients، therefore it keeps nutrients away from microorganisms and prevents their fermentation. Tannins also make a complex with proteins and this complex in undigested residual cause lower estimate of truly digested organic matter and error in PF quantity. Also، saponin and oxalate reduce fibrolytic enzyme activity and fiber degradability in rumen. Conclusion: Therefore، subabul as a substitute for 50 % of alfalfa had no negative effect on dry matter digestibility and fermentable parameters، so it can be used as a forage replacement in Najdi goat diet.