جستجوی مقالات مرتبط با کلیدواژه "اضافه وزن" در نشریات گروه "علوم دام"

In the past studies, the beneficial effect of insoluble fiber in broiler feed has been well demonstrated. Studies have shown that moderate amounts of fiber in poultry diets lead to significant improvements in nutrient utilization efficiency. Depending on the type of dietary fiber (soluble or insoluble), the particle size plays a role in the growth and development of gizzard and improves the mixture of digestive substances with digestive secretions. On the other hand, nutritionists are trying to respond to the rapid growth needs of birds by increasing the energy concentration of diets. Fats are considered for this purpose, as their energy value is at least twice that of carbohydrates and proteins. At a young age, the secretion of bile acids and the activity of pancreatic lipase are low, and therefore, the ability to digest fat in young broilers is compromised. Some studies have shown that cellulose and oat hull as a source of insoluble fiber (3%) in the diet of broiler chickens have increased the apparent digestibility of crude fat in the ileum and increased the availability of energy for the bird. Therefore, the purpose of this research is to investigate the effects of sunflower hull with different particle sizes in diets containing different sources of fat on growth performance, digestibility of nutrients and the microbial population of the caecum of broiler chickens.

This experiment was conducted using 360 one-day-old Ross 308 broiler chickens in a completely randomized design with a 2×3 factorial arrangement for 42 days. Experimental treatments included: sunflower hulls (SFH) (without hulls, 3% with 1 mm particle size and 3% with 5 mm particle size) and different fat sources (3% tallow, 3% canola oil). Feed intake (FI) and body weight gain (BWG) of birds were recorded and feed conversion ratio (FCR) was calculated. To determine the ileal digestibility of nutrients, 3 g/kg of chromium oxide was fed to chickens on days 37-42 of the rearing period. On the 42nd day of rearing, the ileum contents of 2 birds were collected and stored in a freezer at -20◦C. To investigate the morphology of the small intestine, 5 cm of the duodenum, jejunum and ileum were taken. Cecal microbial population also determined at 42 days of age. The data obtained from the experiment were analyzed using SAS statistical software and GLM procedure. To compare means, Duncan's (1955) multi-range test was used at a significant level of 5%.

The results showed that, using of the coarse and fine SFH in the diet of broiler chickens increased FI and improved the FCR in the whole period of experiment (P<0.05). Canola oil improved FI and BWG compared to tallow (P<0.05). Apparent digestibility of crude protein and crude fat also increased by using of coarse SFH in the diet (P<0.05). The use of coarse SFH increased the villus height of duodenum and the villus height and thickness of ileum (P<0.05). Canola oil increased the villus height of ileum, but decreased the villus thickness compared to tallow treatment (P<0.05). The use of coarse SFH in the diet reduced the population of Escherichia coli bacteria in the cecum, and coarse SFH with different sources of fat increased the population of Lactobacillus (P<0.05).

In general, the results of the present study showed that the addition of coarse sunflower hull to the diet could improve the growth performance of broilers by increasing the digestibility of crude protein, crude fat, Lactobacillus population, and reducing the cecal population of E. coli. Although its interaction with canola oil also had positive effects on the population of beneficial gut bacteria.

This experiment was conducted to evaluate the effect of Thyme essential oil on performance and some physiological parameters of broiler chickens fed diets containing wheat in a completely randomized design with a 2×3 factorial arrangement using 264 broilers (Ross 308) in ground floor. Treatments consisted of 2 levels of wheat (0 and 50% of the diet) and 3 levels of essential oil of Thyme (0, 200 and 400 ppm). Performance parameters were recorded weekly. Determination of micro-flora, carcass characteristics, and blood parameters were done on day 42. The results showed that adding the Thyme essential oil to the diet containing 50% wheat increased feed intake at the all period of experiment. Body weight gain was increased significantly in the birds that consumed 50% wheat with 400 ppm essence compared to the birds consumed the diet without wheat or without essence at the starter period. The birds consumed the diet without wheat with essence had lower blood concentration of LDL. Although, adding essence at the level of 400 ppm to the diet without wheat increased significantly blood concentration of HDL. The diet contained 50% wheat without essence had higher abdominal fat compared to the diet with 200 and 400 ppm of essence without wheat and also the diet contained 50% wheat with 400 ppm essence. Overall, the use of Thyme essence at the level of 400 ppm in wheat-based diet is recommended for increasing feed intake and improving some physiological parameters of broiler chickens.

In order to investigate the effect of organic zinc (Zn) supplement in broiler chicken nutrition that reared at high stock density, this experiment was done by using 2 levels of density (10 and 16 birds/m2) and 4 levels of Zn (40, 80, 120 and 160 ppm) in a completely randomized design with 4×2 factorial arrangement. The results showed that birds with higher stocking density had lower feed intake (FI) and feed conversion ratio (FCR) compared to those in normal density from d 1-21 and birds with normal stocking density had lowest FI and FCR from d 22-42 (P<0.05). Cecal population of Coliform decreased in normal and high stock density by increasing Zn level in the diet (P<0.05). Apparent ileal digestibility of crude protein significantly increased by increasing the levels of Zn in the diet in normal and high stock density (P<0.05). These data suggest that dietary supplementation of Zn significantly increased ileal digestibility of crude protein and organic matter and also, decreased cecal population of Coliform and E. coli in high and normal stocking density without affecting the performance of broilers.