| چکیده انگلیسی مقاله |
Introduction and Objective: Heat stress is one of the most important challenges in the country's livestock breeding industry, especially in sheep farming, excessive increase in body temperature under such conditions is associated with a decrease in feed consumption and energy retention, resulting in reduced livestock production, prolonged fattening period and the feed consumed for weight gain being used to deal with heat stress, and as a result significant economic losses are imposed. Therefore, the selection of efficient management and nutritional solutions has particular importance. Research has shown that altering the dietary cation- anion difference (DCAD) levels under heat stress conditions can compensate for high excretion of minerals, reduce feed consumption and the negative effects of heat stress by increasing dietary electrolytes and changing blood acid-base balance. On the other hand, as the price of animal feed increases day by day, the addition of nutrients that are low in price and smooth the challenges caused by heat stress, can be a good option to achieve the yield from the usual feed consumption under normal conditions. Consequently, investigating the effects of changing the levels of cation- anion difference in the dietary on livestock, while providing a suitable view for breeders, provides appropriate solutions for experts in the field of dietary design.. In this regard, this study aimed to elucidate the effects of varying dietary cation-anion difference levels on the parameters of organic matter digestibility, blood parameters, and rumen fermentation in male Zandi lambs under heat stress.
Materials and Methods: In order to investigate the objective of the present study, forty male Zandi lambs, averaging 39 kg in body weight, were randomly assigned to five treatment groups, each with 8 replicates. The diets were formulated to contain different concentrations of DCAD (150, 300, 450, 600, and 750 mEq/kg dry matter). The experimental period lasted 100 days following a 21-day adaptation phase. For the chemical composition of the diets, daily samples of the diet were collected and analyzed according to the guidelines of AOAC. Sodium, potassium, and chlorine levels were measured using an atomic absorption spectrometer, and daily dry matter intake was measured and calculated taking into account the remainder. Blood parameters were measured according to AOAC methods. Ruminal fluid osmolality was measured using an osmometer and volatile acids were analyzed according to the guidelines. N-ammonia levels were also determined using salicylate hypochlorite analysis. The temperature-humidity index was evaluated to investigate heat stress. Analysis and statistics were also performed using SAS 9.4 software with GLM method and for Post Hoc comparisons of means the least significant difference (LSD) test method was used.
Results: The findings of this study showed that the temperature- humidity index was continuously above 75 during the test period, emphasising the presence of heat stress. The rectal temperature of the control group was not significantly different from the other groups. There was a statistically significant difference between the treatments containing different levels of DCAD in terms of dry matter intake, nutrient intake and apparent digestibility (P<0.05), so that dry matter intake, crude protein digestibility and dry matter digestibility in the control group were significantly lower than in the other treatments (P<0.05). In addition, in the control group ruminal pH was notably lower than the other treatments (P<0.05). However, rumen fermentation parameters such as butyric acid, buffering capacity, acetic acid, propionic acid, the combined total of acetic acid and propionic acid, and the acetic acid to propionic acid ratio were unaffected by varying dietary cation- anion difference concentrations (P>0.05). Blood glucose parameters revealed significant differences between treatments (P<0.05), so the control group demonstrating the most significant impact on blood glucose levels. Conversely, no significant differences (P>0.05) were observed for other blood markers including potassium, magnesium, chlorine, nitrogen balance and phosphate. The highest levels of calcium and sodium were observed in the control group, and the highest level of cholesterol was associated with the fifth group with the highest level of DCAD (P<0.05).
Conclusion: Overall, the findings showed that manipulating the cation- anion difference level of the diet had a significant effect on rumen pH, but did not have statistically significant impact on the concentration of volatile fatty acids and, as a result, on rumen fermentation. However, numerically, the control group had the highest levels of ammonia and total volatile fatty acids. The observed decrease in ammonia concentration with increasing DCAD levels increases rumen acidity, which creates a favorable environment for the synthesis of more volatile fatty acids; therefore, these levels are lower in the control group. The direct relationship between dry matter intake, crude protein digestibility, and dry matter digestibility and increased DCAD levels indicates that lambs under heat stress conditions can maintain their apparent digestibility and performance by increasing the level of dietary cation-anion difference. In general, since most of the studied parameters and biochemical metabolites of the sheep's blood had no significant change and were in the normal range, it could be the reason for the relative adaptation of native sheep to heat stress conditions. On the other hand, increasing the cation-anion level of the diet has partially solved the problems caused by heat stress.
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| نویسندگان مقاله |
محمد خانی | mohammad khani
Ph.D.student, Department of Animal Science, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran
دانشجوی دکتری ، گروه علوم دامی، واحد شهر قدس، دانشگاه آزاد اسلامی، تهران، ایران
امیر فتاح | amir Fattah
Assistant Professor,*2 Department of Animal Science, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran
استادیار، گروه علوم دامی، واحد شهر قدس، دانشگاه آزاد اسلامی، تهران،
سید روح اله ابراهیمی محمود آباد | Seyyed Roohollah Ebrahimi-Mahmoudabad
Associate Professor,3 Department of Animal Science, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran.
دانشیار،گروه علوم دامی، واحد شهر قدس، دانشگاه آزاد اسلامی، تهران، ایران
ساحره جوزی شکالگورابی | Sahereh Joezy-Shekalgorabi
Associate Professor ,4 Department of Animal Science, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran
دانشیار، گروه علوم دامی، واحد شهر قدس، دانشگاه آزاد اسلامی، تهران، ایران
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