ABSTRACT The aim of this study was to investigate the effects of different dietary levels of L-arginine on the growth performance, blood parameters, and lipogenic gene expression of Arian broiler chickens. For this purpose, 168 Arian broiler chicks (40.33±1.7 g) were assigned to four treatments with three replicates of14 birds each, according to completely randomized design. The experimental treatments consisted of 100, 124, 139, and 154% dietary arginine levels relative to the published requirements of Arian broilers. On 42 d of the experiment, blood samples were collected from two birds (six birds per treatment) for blood metabolite measurements. These birds were then euthanized for carcass evaluation and collection of tissue samples. Increasing dietary arginine levels reduced (p<0.05) the gene expression of fatty acid synthase, acetyl-coenzyme A carboxylase, and malic enzyme in the liver and lipoprotein lipase in the abdominal fat tissue, as well as abdominal fat relative weight. Increasing dietary arginine levels significantly increased (p<0.05) body weight, feed efficiency, carcass yield, breast and thigh relative weights, and glucose and HDL (high-density lipoprotein) blood levels, and reduced cholesterol, triglyceride, and LDL (low-density lipoprotein) blood levels. Since almost similar performance and carcass trait results were obtained both with 124 and 139% arginine levels, supplying Arian broiler diets with 124% arginine is suggested.

Two experiments were conducted to investigate the effects of fortification of the pre-starter diet with glutamine in post-hatch broiler chicks. In the first experiment, male chicks were used to study the impact of glutamine supplementation at three levels (0%, 1% and 2%) on performance, apparent faecal digestibility (AFD) and ileal digestibility (AID) of amino acids (AAs), as well as intestinal morphometric parameters from 0 to 14 days old. The best performance was obtained at 1% supplementation. Average daily feed intake and feed conversion ratio (FCR) were affected by treatments. Supplementing diets with glutamine resulted in increase of digestibility values for arginine (Arg), lysine (Lys), isoleucine (Ile) and valine (Val). Glutamine-supplemented diets led to higher villus height (VH) and shallower crypt depth (CD) in the jejunum and ileum. A second experiment was performed to investigate whether the form of glutamine could affect performance and morphometric parameters in newly hatched chickens. A control diet was prepared, based on casein as the sole source of protein-bound AAs. Three diets based on synthetic AAs were used to obtain nutrient values of the control diet, which were supplemented with a synthetic form of glutamine, glutamic acid and a 50 : 50 ratio of glutamine : glutamic acid. Chickens fed the control diet presented higher average daily weight gain and better FCR. None of the AID coefficients of amino acids were influenced by the dietary treatments, except glutamic acid and aspartic acid, which were decreased in chicks fed synthetic AAs. In conclusion, 1% glutamine supplementation improved performance, morphometric parameters and AID and AFD values of cationic AAs. The form in which dietary glutamine was provided could affect performance.

ABSTRACT The effect of egg powder inclusion in the pre-starter diet (1-7 days of age) on the performance, and intestinal morphology and microbiology of male broiler chickens was evaluated in a completely randomized design. Starter diets with equal metabolizable energy and crude protein levels were formulated to contain 0, 20, 40, or 60 g egg powder/kg diet. Results showed that body weight, feed intake, feed conversion ratio, and European efficiency index were positively affected (p≤0.05) by egg powder inclusion in the starter diet. Inclusion of 40 g egg powder/kg diet in the starter diet promoted the best performance results. Jejunal villus height and villus to crypt ratio increased (p≤0.05) and intestinal length decreased (p≤0.05) as a result of egg powder inclusion in the starter diet. Egg powder inclusion in the starter diet reduced (p≤0.05E. coli counts, but increased (p≤0.05) lactic acid bacteria counts in the small intestine. The results obtained in the present study indicate that the inclusion of 40 60 g egg powder/kg of starter diet g improved the performance and intestinal health of broilers.

In order to estimate the crude protein (CP) equivalence value of Natuzyme-p (NP) enzyme by using regression response equations, two experiments were carried out using Ross (308) broiler chicks. Graded levels of dietary CP (while amino acids levels were kept constant) and NP enzyme were used to derive the regression equation in the first experiment. Four levels of dietary CP and NP enzyme were fed to 160 feather-sexed male broiler chicks during the starter (0-28 d of age) and grower (28-42 d of age) period. Each diet was offered to four replicates of five chicks in a completely randomized design. Results obtained in experiment one failed to fit a regression equation between BW, dietary CP levels and NP enzyme. In experiment two, graded levels of CP changed along with the levels of lysine (Lys), Met+Cys and threonine (Thr). Regression equations between BW and dietary CP and NP enzyme were derived. Nonlinear and linear equations were generated for enzyme and CP. Based on an assessment of r² and P value, nonlinear equations were used to determine enzyme equivalence. The derived regression equations of body weight for CP were set to be equal with those obtained for NP and were solved; enzyme equivalence value for CP was calculated by subtracting the obtained value from CP content of basal diet. Crude protein equivalence value of NP at 28 and 42 d of age was estimated to be 0.96 and 0.38 %, respectively.

The present study was carried out to examine the effect of vitamin premix reduction or withdrawal in finisher diet (29 to 42 days of age) on the performance and meat quality of chicks fed a wheat/barley based diet and reared on floor pens. A total of 504 male broiler chicks (Ross® 308) were allocated to seven treatment groups, with four replicates per treatment and 18 birds per replicate. All data were analyzed according to a completely randomized design. Results showed that the reduction or withdrawal of the vitamin premix from diets in different weeks of finisher period did not affect chicken performance (p>0.05). There were no significant differences in TBARS values of thigh samples of birds slaughtered at 35 days of age. However, the TBARS value of the treatment without vitamin premix was significantly higher than in the other treatments (p < 0.05) when birds were slaughtered at 42 days of age. Finally, the results of this study demonstrated that it is not possible withdrawal all premix vitamin of the diet. However, it may be possible to reduce vitamin supplements in finisher broiler diets without any negative effects on performance or meat quality during freezing.

This study was conducted to compare the withdrawal or reduction of the vitamin premix (VP) from broiler diets at between days 29 and 42 of age on the characteristics of leg bones of the broilers in a battery cage (Trial 1) and a floor (Trial 2) rearing system. Seven experimental diets were formulated, based on wheat and barley, and consisted of four replicates per treatment. The metatarsus bone was used for measuring biomechanical bone characteristics, and alkaline phosphatase (ALP) activity and calcium concentrations blood serum to assess vitamin D3 status. The results of the first trial showed that there were no significant differences in body weight, strength of metatarsus bone and contents of ash, Ca and P in the toe with reduction or withdrawal of the vitamin premix from the diets during days 29 - 35. However, after 36 - 42 days there were significant differences for these parameters between the treatment without the vitamin premix (T1) and the other treatments. At 29 - 35 days and 36 - 42 days there were significant differences for ALP activity between T1 and the other treatments. The results of Trial 2 showed that the reduction in the vitamin premix and withdrawal at d 29 did not impair body weight, bone parameters and blood concentrations during the final growth period of the broilers. Finally, the results of the present study indicate that in the battery cage system it is possible to reduce the level of the dietary vitamin premix during the finisher period, but withdrawal can negatively affect body weight and bone parameters of broiler chickens, while in the floor system it is possible to withdrawal VP from broilers' finisher diets.

Broiler performance to the end of the rearing period may be negatively influenced by delayed access to feed and water immediately after hatch. This study was conducted with 320 Ross 308 broiler chicks, to evaluate the influence of delayed access to feed and water during the neonatal period (0, 16, 32 and 48 h) on performance and gastrointestinal (GIT) growth. The experiment was conducted as a complete randomized design (four replicate, each with 20 chicks). The results showed that extending post-hatch deprivation of feed and water had a significant negative impact on bird performance. Broilers deprived for 48 h had lower body weights, average daily gains and feed intakes compared to the control and to a lesser extent to the other treatments. Average daily gain, daily feed intake and feed conversion ratio were mostly significantly affected by feed and water deprivation regimens during the first week of the rearing period. At marketing age, the negative impact of severe feed and water deprivation on the birds' performance was substantially decreased, though birds with a 48 h delayed access to feed and water had lower average daily gains and feed intakes compared to the control. Birds mortality rate (%) was not affected by feed and water deprivation during the neonatal period. The results also indicated that the relative weights of the jejunum, ileum and liver of birds getting access to feed and water only at 48 h after arrival were significantly lower when compared to the other groups. The broiler carcass characteristics, abdominal fat percentage at 42 days of age, and gastrointestinal measurements at 21 and 42 days of age were not influenced by the different treatments. In conclusion, the results of this experiment confirmed that immediate access to feed and water after placement will ensure the optimal performance of broiler chicks at market age, and that broiler chicks do not have enough potential to fully compensate for growth retardation caused by long-term deprivation of feed and water during the neonatal period.

To clarify the effects of high (20 and 40% more than normal) and low (20% less than normal) daily feed allowance on egg and body parameters, ovarian morphology and plasma glucose, cholesterol, triacylglycerol, leptin-like hormone, nitrite/nitrate and gene expression of inducible nitric oxide synthase (iNOS) in the granulosa layer of F1 follicle, broiler breeder hens (30-week-old) were fed for 30 days. Egg and body parameters significantly changed between treatments (p<0.05). Effect of different level of feed intake on ovarian morphology parameters was significant (p<0.05), except for white follicles. After 30 days of experiment, plasma nitrite/nitrate (as a index of plasma nitric oxide) and leptin-like hormone increased in FI+20% and FI+40% groups as compared to controls (p<0.05). Plasma level of leptin-like hormone also significantly (p<0.05) increased in FI+40% group. The relative amount of iNOS mRNA expression in the granulosa layer of F1 follicles was significantly higher in FI-20% and FI+40% groups than in control group only after 4 weeks of experiment. The amount of these elevations in the FI-20% and FI+40% groups were 32.4% and 60.9% respectively. It was concluded that iNOS gene is normally expressed in follicular granulosa cells of F1 follicle of broiler breeder hens 2-4 hours before ovulation. However, over- and underfeeding of hens increased iNOS expression in F1 follicle, which may be one of the atresia-inducing factors in hierarchical follicles as shown by the significant (p<0.05) increase of shrunken follicles in the ovary of over- and under-fed broiler breeder hens after 30 days of feeding.

Consumption of low crude protein (CP) diets causes elevation in fat accumulation in chickens, and this effect is independent of dietary essential amino acid levels. Thyroid hormones, because of their metabolic regulatory characteristics, might be an effective factor in lipogenesis. Therefore, a study was conducted to investigate the influence of low CP diets on hormonal function of the thyroid. Two hundred and sixteen male broiler chicks, 10 - 25 days of age, were fed experimental diets that contained 230, 210, 190 and 170 g CP/kg with adequate amounts of total and digestible essential amino acids at or above NRC (1994) recommendations. Two other diets were the same as the 190 and 170 g CP/kg diets but contained additional glycine and glutamic acid. Reduction in CP below 190 g/kg led to a decline in body weight and feed intake and an increase in fat deposition in body, as would be expected. Plasma T4 concentration decreased significantly in the birds on the 170 g CP/kg diet and supplementation of glycine and glutamic acid had no effect on hormonal levels of the thyroid despite the reduction in whole-body and abdominal cavity fat deposition. Plasma T3 concentration was not affected. Therefore, it is concluded that a reduction in circulatory levels of T4 that occurs in broiler chicks fed diets containing below 190 g CP/kg though with adequate essential amino acids, may be an effective method of increasing fat deposition.