نوع مقاله : مقاله پژوهشی
نویسندگان
گروه علوم دامی، دانشکده کشاورزی، دانشگاه لرستان
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: Although sheep husbandry in Iran has a long history, it is usually practiced in a traditional manner with low productivity. The growing population, increasing demand for red meat, and high costs of feed supply necessitate the use of rations with balanced nutrients, minimal waste, and maximum profitability. Therefore, nutrition management and improving productivity in this sector are of particular importance. Physical processing of feed is one of the key management strategies in this regard and is among the most important factors affecting feed intake and apparent digestibility. Feed processing and particle size modification have been shown to influence animal performance. Pelleting, grinding feed ingredients, and various processing methods applied to cereal grains and other ration components have all been employed to improve nutrient utilization efficiency in ruminant nutrition. This study investigated the effects of physical form and feeding method of diets on growth performance, apparent digestibility, and selected ruminal and blood parameters of fattening lambs.
Materials and methods: Twenty-eight Lori-Bakhtiari male lambs, with an average age of approximately three months and an average body weight of 35.8±4.4 kg, were used at the Small Ruminant Research Farm, Faculty of Agriculture, Lorestan University, Iran. The experimental period lasted 75 days, including 15 days of adaptation and 60 days of fattening. Animals were housed individually (150×100×100 cm; length×width×height) in pens equipped with water and feed buckets, and had ad libitum access to feed and water throughout the study. Four experimental diets were designed in a 2×2 factorial arrangement, consisting of two concentrate forms (pelleted and mash) and two feeding methods (total mixed ration and separate feeding). The treatments included: (1) Total mixed ration (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. The diets for both growing and finishing periods were formulated according to NRC (2007) to meet at least the minimum nutrient requirements of the lambs. The concentrate portion of each diet was ground to 3 mm, and pelleted concentrates were processed using a 5 mm die. During the experimental period, diets were fed twice daily at 08:00 and 16:00 h. Feed intake and refusals were recorded throughout the study. Lambs were weighed on day one and subsequently every 20 days before the morning feeding after a 16-hour fasting period. Average daily gain was calculated as the difference between initial and final weights divided by the number of days. Apparent nutrient digestibility was determined using the acid-insoluble ash marker method. On day 28 of the growing phase and day 58 of the finishing phase, ruminal fluid samples were collected three hours after the morning feeding using a stomach tube. To reduce saliva contamination, the first 10–20 mL of the sample was discarded. Data were analyzed using a completely randomized design with the SAS software (version 9.4).
Results and discussion: Feeding pelleted concentrate during the growing period increased the digestibility coefficients of ADF and NDF, while in the finishing period, it improved the digestibility of nutrients, dry matter, organic matter, and ADF (P<0.05). Feeding mash concentrate during the finishing period increased blood urea nitrogen, alanine aminotransferase activity, and eating and chewing times, while reducing resting time (P<0.05). Separate feeding of forage and concentrate during both the growing and finishing periods increased feed intake, improved crude fat digestibility, and in the finishing phase, increased ruminal pH and alkaline phosphatase activity. Feeding mixed rations increased NDF digestibility and alkaline phosphatase activity during the growing phase, and improved ADF digestibility during the finishing phase (P<0.05). The interaction between concentrate processing and feeding method significantly affected crude fat digestibility, blood urea nitrogen, and eating activity in the growing period, as well as crude protein and crude fat digestibility in the finishing phase (P<0.05). However, concentrate processing, feeding method, and their interaction had no significant effect on growth performance traits (P>0.05). Overall, the results demonstrated that physical form and feeding method of the diet influenced apparent digestibility, ruminal and blood parameters, and feeding behavior, but had no effect on growth performance.
Conclusions: The results of this study indicated that although dry matter intake was higher in the separate feeding of concentrate and forage treatment, feeding a TMR with pelleted concentrate improved apparent nutrient digestibility and some metabolic parameters. These findings suggest that feed efficiency was higher in the TMR with pelleted concentrate treatment, which may be more beneficial for fattening lambs. Furthermore, feeding method significantly influenced ruminal pH during the finishing period and blood alkaline phosphatase activity during both periods, while concentrate physical form affected blood urea nitrogen and alanine aminotransferase activity in the finishing period, warranting further investigation.
کلیدواژهها [English]
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