نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم دامی دانشکده کشاورزی دانشگاه خرم آباد، خرم آباد ایران
2 گروه علوم دامی دانشکده کشاورزی دانشگاه لرستان، خرم آباد ایران
3 گروه علوم دامی، دانشگاه لرستان، خرم آباد، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction
Sheep husbandry in Iran, while long-established, is predominantly traditional and characterized by low productivity. Given the growing population, rising demand for red meat, and the high cost of feed, there is a critical need to adopt rations that ensure balanced nutrition, minimize waste, and maximize profitability. Consequently, effective nutritional management is essential for enhancing productivity in this sector. A key strategy in this endeavor is the physical processing of feed, a major factor influencing both feed intake and apparent digestibility. Processing methods—such as pelleting, grinding, and specific treatments applied to cereal grains—have been demonstrated to significantly improve nutrient utilization efficiency and overall animal performance in ruminant nutrition.
Materials and Methods
This study evaluated the effects of dietary physical form and feeding method on the growth performance, apparent digestibility, and selected ruminal and blood parameters of fattening lambs. Twenty-eight Lori-Bakhtiari male lambs (approximately 3 months old; initial body weight 35.8 ± 4.4 kg) were used in a 75-day experiment at the Small Ruminant Research Farm, Lorestan University. The trial consisted of a 15-day adaptation period followed by a 60-day fattening period. Lambs were housed individually in pens (150 × 100 × 100 cm) equipped with feed and water buckets, allowing for ad libitum access to feed and water.
The experiment employed a 2 × 2 factorial arrangement with four dietary treatments. The factors were concentrate physical form (pelleted vs. mash) and feeding method (Total Mixed Ration [TMR] vs. separate feeding). The treatments were as follows: 1) TMR with mash concentrate, 2) Separate feeding of mash concentrate and forage, 3) TMR with pelleted concentrate, and 4) Separate feeding of pelleted concentrate and forage.
Diets for both growing and finishing periods were formulated to meet or exceed the nutrient requirements of lambs according to NRC (2007) guidelines. The concentrate portion of all diets was ground through a 3 mm screen, with pelleted concentrates subsequently processed using a 5 mm die.
Diets were offered twice daily at 08:00 and 16:00 h. Feed intake and Feed refusal were recorded daily. Lambs were weighed on day 1 and every 20 days thereafter before the morning feeding following a 16-hour fast. Average daily gain (ADG) was calculated as the difference between the final and initial body weight divided by the number of fattening days.
Apparent nutrient digestibility was determined using acid-insoluble ash as an internal marker. Ruminal fluid samples were collected three hours after the morning feeding on day 28 (growing phase) and day 58 (finishing phase) using a stomach tube. The first 10–20 mL of each sample was discarded to minimize saliva contamination.
Data were analyzed as a completely randomized design with a 2 × 2 factorial arrangement using the GLM procedure of SAS (version 9.4). The model included the main effects of concentrate physical form, feeding method, and their interaction.
Results and Discussion
The physical form of the concentrate and the feeding method significantly influenced digestibility and metabolic parameters, though not growth performance. During the growing period, lambs fed pelleted concentrate exhibited higher digestibility coefficients of acid detergent fiber (ADF) and neutral detergent fiber (NDF). In the finishing period, pelleting further improved the digestibility of dry matter, organic matter, and ADF (P < 0.05). Conversely, feeding mash concentrate during the finishing period resulted in higher blood urea nitrogen (BUN), increased alanine aminotransferase (ALT) activity, and longer eating and chewing times, while reducing resting time (P < 0.05).
The method of feeding also had distinct effects. Separate feeding of forage and concentrate increased feed intake and improved crude fat digestibility in both periods. In the finishing phase, it also led to a higher ruminal pH and increased alkaline phosphatase (ALP) activity. In contrast, the Total Mixed Ration (TMR) method enhanced NDF digestibility and ALP activity during the growing phase, and improved ADF digestibility in the finishing phase (P < 0.05).
A significant interaction between concentrate processing and feeding method was observed for several parameters. In the growing period, the interaction affected crude fat digestibility, BUN, and eating activity. During the finishing phase, it influenced the digestibility of crude protein and crude fat (P < 0.05). Despite these effects on digestion and metabolism, neither the main factors nor their interaction had a significant impact on overall growth performance traits, such as average daily gain (P > 0.05). This indicates that while nutrient utilization and metabolic pathways were altered, the lambs' compensatory mechanisms maintained similar growth rates across treatments.
Conclusion
In conclusion, this study demonstrates that dietary physical form and feeding method are important management tools that primarily affect digestive efficiency and metabolic health in fattening lambs, rather than final growth performance. While separate feeding promoted higher dry matter intake, the combination of a TMR with pelleted concentrate proved more effective in enhancing apparent nutrient digestibility and favorable metabolic parameters. The improved feed efficiency suggested in the TMR-pellet treatment presents a potentially more beneficial strategy for lamb fattening operations.
Key findings warranting further investigation include the significant influence of feeding method on ruminal pH during the finishing period and on blood alkaline phosphatase activity, as well as the effect of concentrate physical form on nitrogen metabolism (as indicated by BUN) and liver enzyme (ALT) activity in the finishing period. These results provide valuable insights for optimizing feeding strategies to improve efficiency and animal health.
کلیدواژهها [English]
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