Document Type : Research Articles
Authors
Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
Abstract
Introduction: The poultry industry is a crucial source of protein for human consumption, but nitrogen disposal, a major cause of environmental pollution, has been a significant concern in recent decades (Fasina et al., 2010). Various solutions have been proposed to mitigate environmental pollution from poultry manure, with one of the most practical being the use of diets with lower protein levels. It has been demonstrated that low-energy and protein diets can save costs and reduce nitrogen excretion (Gholami et al., 2015). Phase, intermittent, and selective feeding are among the feeding methods, each offering distinct benefits. These rations not only reduce feed costs but also decrease nitrogen excretion into the environment and minimize metabolic disorders such as ascites. They are particularly recommended for maintaining birds under heat stress conditions (Pope et al., 2004). Recent studies have shown that sequential feeding effectively reduces chick mortality. Intermittent feed restriction in young broilers modifies hormonal status and contributes to a metabolic state that can enhance immune capacity (Sauvant et al., 2002). This study aims to investigate the effect of alternating low-energy and protein diets with standard diets in broilers, focusing on growth performance, blood metabolites, and small intestine morphology.
Materials and Methods: A total of 360 one-day-old Ross 308 male broilers were divided into six treatment groups, with five replicates per group and 12 birds per replicate. The treatments were as follow: 1) Control Diet: Formulated according to Ross 308 nutrient recommendations and fed throughout the experiment. 2) 5% Reduced Crude Protein (CP) Diet: Fed from day one to the end of the experiment. 3)7.5 % Reduced CP Diet: Fed from day one to the end of the experiment. 4) 10% Reduced CP Diet: Fed from day one to the end of the experiment. 5). Alternating Diets 1 and 3: Switched every other day. 6) Alternating Diets 1 and 4: Switched every other day. Chickens had ad libitum access to water and feed. They were provided with 23 hours of light and 1 hour of darkness daily. The initial room temperature was set at 32°C and was gradually reduced by 0.5°C per day until it reached 21°C by day 21, after which it remained constant. The amount of feed consumed in periods (1-10, 11-24, 1-24 days) was measured in each replicate pen. At the age of 24 days, one bird from each pen was slaughtered and dissected to determine the length of the duodenum, jejunum, and ileum. Subsequently, an intestinal section was separated from the jejunum midpoint and histology was performed on it. At the age of 24 days, one bird from each experimental unit was randomly selected and blood was collected from the wing vein. The resulting blood was transferred to test tubes. The samples were kept at room temperature for 30 minutes, then centrifuged at 3000 rpm for 15 minutes, and the serum was separated from the blood. Serum samples were poured into microtubes and kept at -20°C until analysis by an auto analyzer (Bio Systems S.A. – Costa Brava 30,08030 Barcelona, Spain). Serum contents were measured in terms of cholesterol, triglyceride, LDL-C, HDL-C, and blood uric acid by auto analyzer. The data obtained from this experiment were analyzed using SAS statistical software and the General Linear Models (GLM) procedure, and the treatment means were compared using Duncan's new multiple range test at p < 0.05.
Results and Discussion: The results showed no significant differences between treatments in feed conversion ratio and daily feed intake (P > 0.05). Weight gain from days 1 to 24 also showed no significant differences (P > 0.05). Treatments did not significantly affect carcass traits, jejunum villi width, or crypt depth (P > 0.05). However, villus height in treatment 3 was higher than in other treatments and significantly higher than control. Muscle layer thickness in treatment 2 was significantly greater than in other treatments and the control (P < 0.05). Blood biochemical parameters were not significantly different among treatments.
Conclusion: Overall, the treatment with 5% reduced crude protein, improved small intestine morphology. Reducing crude protein by up to 10% and alternating it with the control diet did not negatively affect growth, blood metabolites, or jejunum morphology. Since growth performance was unaffected, all treatments are viable options.
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