| چکیده انگلیسی مقاله |
Extended Abstract
Introduction: The production of lignocellulosic materials from agricultural and industrial activities is substantial worldwide, representing the most abundant renewable energy source on Earth. A significant portion of these materials is utilized as animal feed, particularly in developing countries with extensive livestock populations. In India, for instance, the ruminant feeding system heavily relies on agricultural by-products rather than grazing or hand-feeding due to the vast size of the livestock sector. Ruminants possess the unique ability to convert relatively unusable fibrous by-products, such as straws, fruit waste, and bagasse, which have low digestibility and are primarily composed of cell walls, into human-consumable products. This conversion process is facilitated by the microbial fermentation occurring in the rumen, enabling ruminants to extract energy from otherwise inaccessible carbohydrate sources for non-ruminant species. The current study aimed to investigate the effect of replacing wheat straw, a commonly used roughage source, with different levels of sugarcane bagasse on growth performance, nutrient digestibility, and blood parameters of Zel fattening lambs.
Materials and Methods: The experiment was conducted in two distinct parts. In the first part, the chemical composition, gas production characteristics, and estimated energy values of the wheat straw and sugarcane bagasse samples to be used in the feeding trial were determined. Three replicates of each sample were analyzed for dry matter, crude protein, ether extract, ash, and neutral detergent fiber and acid detergent fiber contents using standard procedures. Additionally, the gas production potential of the samples was measured by recording the cumulative gas volume produced at 2, 4, 6, 8, 12, 16, 24, 48, 72, and 96 hours of incubation. The gas production data were fitted to the exponential equation to estimate the potential gas production (b), rate of gas production (c), and other fermentation kinetic parameters. Based on the gas production values, metabolizable energy (ME), net energy for lactation (NEL), organic matter digestibility (OMD), and short-chain fatty acid concentrations (SCFA) were calculated using empirical equations. In the second part, the effect of replacing wheat straw with sugarcane bagasse on growth performance, blood parameters, and nutrient digestibility of Zel fattening lambs was evaluated. The experiment was conducted at the research farm of the University of Tehran, located in Pakdasht, Tehran Province, Iran. Fifteen Zandi male lambs with an initial weight of 31 ± 1.5 kg were used in a completely randomized design with 3 treatments and 5 replications. The lambs were housed individually in individual cages and fed the experimental diets for 90 days after a 10-day adaptation period. The experimental diets were formulated as total mixed rations based on the NRC (2007) nutrient requirements for sheep and included: 1) Control diet containing 15% wheat straw, 2) Diet with 7.5% wheat straw and 7.5% sugarcane bagasse, 3) Diet with 15% sugarcane bagasse. At the beginning of the trial, the lambs were weighed after a 16-hour fasting period, and this weight was considered the initial body weight. Body weight was recorded every two weeks, and feed intake was measured daily. At the end of the experiment, nutrient digestibility was determined using a 3-day collection of feces using AIA method. Blood samples were collected from the jugular vein at the end of the trial, and serum was separated and analyzed for glucose, blood urea nitrogen (BUN), triglycerides, cholesterol, high-density lipoprotein (HDL), total proteins, albumin, and globulins.
Results: The chemical analysis revealed that sugarcane bagasse had a lower crude protein content (2.67%) compared to wheat straw (4.46%), indicating its inferior protein quality. Conversely, sugarcane bagasse exhibited higher fiber fractions, including neutral detergent fiber (88.5%) and acid detergent fiber (70.59%), than wheat straw (NDF: 73.1 and ADF: 51.91). The gas production results corroborated the chemical composition findings, showing that wheat straw had higher potential gas production (b), metabolizable energy (ME), net energy for lactation (NEL), and organic matter digestibility (OMD) compared to sugarcane bagasse. Regarding lamb performance, there were no significant differences in feed conversion ratio among the dietary treatments. However, dry matter intake and BWG decreased (P<0.01) with increasing bagasse levels in the diet, which may be due to the higher fiber content and lower digestibility of bagasse compared to wheat straw. The nutrient digestibility results revealed that diets containing sugarcane bagasse had lower digestibility coefficients for crude protein compared to the control diet containing only wheat straw. This finding is consistent with the chemical composition and gas production data, indicating that the higher fiber and lignin content of bagasse hinders nutrient utilization by the lambs. Blood parameters, including glucose, blood urea nitrogen (BUN), triglycerides and total protein were not significantly affected by the dietary treatments. However, lambs fed diets containing bagasse had lower serum concentrations of albumin, and cholesterol compared to the control group fed the wheat straw diet.
Conclusion: The results of this study demonstrate that sugarcane bagasse can be included up to 7.5% in Zel fattening lamb diets without negatively affecting feed conversion ratio. Higher inclusion levels of bagasse may decrease dry matter intake, potentially due to its higher fiber and lignin content compared to wheat straw. The lower nutrient digestibility observed with bagasse-containing diets, particularly for protein, can be attributed to the higher recalcitrance of bagasse fibers to microbial degradation and fermentation. Overall, the findings suggest that sugarcane bagasse can be considered a potential alternative fiber source for fattening lambs, particularly in regions where it is abundantly available. However, the inclusion level of bagasse should be optimized to maintain adequate nutrient utilization, dry matter intake, and performance. |