| چکیده انگلیسی مقاله |
Introduction: Soybean meal is one of the main sources of protein in animal nutrition; however, its high price and limited production have constrained its widespread use. As global demand for animal products continues to rise, identifying alternative protein sources that can effectively replace soybean meal is crucial for sustainable animal nutrition and production. Soybean meal undergoes extensive protein degradation in the rumen, which is often undesirable for ruminant nutrition. In recent years, cotton cultivation has expanded in Golestan province, Iran, increasing the availability of cottonseed meal as a potential alternative protein source. Utilizing agricultural by-products like cottonseed meal in livestock diets can help reduce reliance on soybean meal while promoting sustainable feed formulations. Cottonseed meal contains lower energy and protein levels than soybean meal but has a higher proportion of rumen-undegradable protein (RUP). Incorporating bypass protein in ruminant diets enhances the availability of essential amino acids, supporting growth and productivity. Since microbial protein alone cannot fully meet the protein requirements for optimal production, ruminants benefit from dietary sources of RUP to ensure sufficient nutrient supply. The commercial mixed concentrate supplement is a formulated blend containing poultry meat by-products, cotton waste, rice bran, wheat bran, corn meal, pistachio powder, and corn steep liquor. This mixture is processed under steam and high pressure in a conditioner, making it a viable protein source for animal diets. Its significance lies in providing a combination of both plant- and animal-derived proteins, which may offer superior nutritional benefits compared to solely plant-based protein sources. This study aimed to evaluate the effects of replacing soybean meal and cottonseed meal with a commercial mixed concentrate supplement on feed intake, hydrolytic enzyme activity, rumen fermentation parameters, and liver enzyme activity in lactating Dalagh ewes. Materials and methods: Twenty-one lactating Dalagh ewes in their sixth week of lactation (38±2.6 kg) were randomly assigned to three dietary treatments, with seven ewes per group. The treatments included: (1) A basal diet supplemented with soybean meal, (2) A basal diet supplemented with cottonseed meal, and (3) A basal diet supplemented with a mixed concentrate. The experiment lasted for 42 days. Ewes were weighed at the beginning and end of the experimental period. Feed refusals were weighed daily, and daily feed intake was calculated by subtracting refusals from the feed offered. Rumen fluid sampling was conducted on day 42, three hours post-feeding, using an esophageal tube. The rumen pH was immediately measured and recorded using a mobile digital pH meter (Metrohm Laboratory pH Meter-691), which was calibrated on-site before use. The ammonia nitrogen concentrations were measured in the samples using standard methods. In addition, the Dehority and Males method was used to count protozoa. The rumen fluid was filtered with a cloth in a test tube wrapped in foil, then 4 mL of rumen fluid was poured. After that, 1 mL of 18.5% formalin, 5 drops of methylene blue dye, and 3 mL of glycerol were added. Counting of protozoa was done by a microscope and a lens with 40X magnification by a Neobar slide. To determine the concentration of volatile fatty acids, 5 mL rumen fluid samples were collected, and 1 mL of 25% metaphosphoric acid was added to each sample to preserve them. The samples were then stored at -20 °C until analysis. The extraction of ruminal hydrolytic enzymes, including carboxymethyl-cellulase and microcrystalline-cellulase, was performed following the method described by Hristov. Results and discussion: The results indicated that dry matter intake (DMI) was significantly higher in the group receiving the mixed concentrate compared to the other treatments (P<0.05). Additionally, calves in the mixed concentrate group exhibited a significant increase in daily milk production compared to those receiving soybean meal or cottonseed meal (P<0.05). Addition of mixed concentrate to the diet of ewes caused a significant decrease in rumen pH and a significant increase in ammonia nitrogen and rumen protozoa population compared to other treatments (P<0.05). Also, rumen acetate concentration decreased under the influence of mixed concentrate consumption, while rumen propionate concentration increased in the rumen of ewes receiving mixed concentrate (P<0.05). But the concentration of butyrate, isobutyrate, valerate, isovalerate, and total rumen volatile fatty acids was not affected by the experimental treatments. The activity of carboxymethyl cellulose and microcrystalline cellulose enzymes in the cell section, extracellular section, solid part, and total rumen parts in the treatments receiving soybean meal and cottonseed meal was higher than in the treatment receiving mixed concentrate (P<0.05). There were no significant differences among the experimental treatments in serum concentrations of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase (P>0.05). Conclusions: The results obtained showed that soybean meal and cottonseed meal can be completely replaced in the diet of ewes without affecting feed intake or rumen health. |