JWSS - Journal of Water and Soil Science

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Effect of different sources of fat on performance of broiler chicks was studied. Three hundred and thirty six chicks were divided into 42 groups of 8 chicks per group. Seven isoenergetic and isonitrogenous diets, mainly based on corn and soybean meal were prepared and fed. These treatments were as follows: corn + soybean meal + (5% tallow, 5% cotton seed crude oil, 5% cotton seed soapstock, 2.5% tallow + 2.5% crude oil, 2.5% tallow + 2.5% soapstock, or 2.5% crude oil + 2.5% soapstock). One control diet without any source of fat was also included. Results showed that average feed intake of diets with different sources of fat up to 56 days old, was not differed from control group. Different sources of fat and their combinations increased weight gain and improved feed conversion. But soapstock had no effect on performance. Added fats increased abdominal fat of chickens. Therefore, if is concluded that on the contrary to soapstock, tallow and crude oil enhanced performance of broiler chickens.

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An experiment with 720 pullets was conducted to investigate the effect of dietary energy levels of pullet and dietary energy and fat of laying ration on subsequent performance parameters during 14-20 and 22-44 weeks of age. In the first period, white leghorn pullets were fed with two diets of low and high density energy (2600 and 3200 Kcal ME/kg). In the lating period (second period), birds, in each treatment of pullet period, were fed with six diets containing three levels of low, medium and high energy (2600, 2750 and 2900 kcal/kg) at two levels of supplemental fat (zero and 2%). All diets were formulated to meet minimum NRC (1994) requirements of amino acids and protein. This experiment was done in randomized complete block designs with 5 replicates. The levels of energy in the growing period did not affect egg production, egg weight, daily feed intake, feed conversion rate and age of pubertal maturity in laying period, but pullets fed with high energy diet had significantly higher weights as compared to low energy diet in the beginning of laying period. In the laying period, the use of supplemental fat (2%) improved egg production and egg weight, but feed intake and feed conversion rate were not affected. Means of feed conversion rate, feed intake and egg production during laying period in low energy diet were greater than those as compared to high energy diet, but egg weight was not affected by energy level of diets. Low energy intake to protein intake ratio in low energy diet versus high energy diet may be a reason for greater egg production in lower energy than in higher energy diets.

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An experiment was conducted to determine growth and carcass characteristics of male broilers subjected to early feed restriction. Restricted birds were fed equivalent to 1/5*BW^0.67 Kcal/day/bird between days 7 and 14. On days 0 to 7 and 14 to 56, all chickens received feed ad-libitum. Diets of feed-restricted birds were supplemented with 15% higher methionin and cystine recommended by NRC (1994) during refeeding in starter and grower periods. No significant differences were observed for liver, breast, heart, carcass and liver fat between early restricted birds and ad-libitum control at 56 days of age. Body weight for restricted broilers were significantly (P<0.05) lower than that of controls in 56 days. However, restricted broilers had significantly lower total-feed to gain ratio than the unrestricted control. Restricted broilers that received diets high in total sulfur amino acids in starter and grower periods had singnificantly lower abdominal fat pad than control birds.

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Evaluation of uric acid contents of poultry excreta was examined for use in the estimation of apparent protein digestibility. Uric acid was determined either by high-performance liquid chromatography or by spectrophotometric method. A high-pressure liquid chromatographic assay was used with absorbance measured at 285 nm. The method used a reverse-phase system with a C18-bonded column (250*4.6 mm, i.d.). The mobile phase was distilled deionized water. Injection volume was 20 l with a flow rate of 1 ml/min. Correlation (r) between the two methods for uric acid content of excreta from birds fed diets with different methionine levels was 0.976. The uric acid values were then used to determine apparent protein digestibility. The apparent protein digestibility values, when corrected for uric acid nitrogen, were comparable with those calculated from amino acid analysis.

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An experiment was conducted with the male Ross broiler chicks from 1 to 42 days of age to test the effects of different dietary protein and lysine levels on performance, carcass characteristics, and N excretion. Treatment diets consisted of three levels of supplemental lysine in starter and grower period (0, 0.15, and 0.30 %) and the two levels of protein (20.84, 17.84 in starter, and 18.12, 16.12% in grower period) with 2900 Kcal ME/kg diet. The results indicated that the Reducing dietary protein decreased significantly the weight gain in starter, grower, and total period up to 6, 4.6, and 5.6%respectively (P<0.05). It also decreased the feed consumption in starter period (P<0.05). Decreasing dietary protein had no significant effect on gain to feed ratio and breast meat yield, but increased abdominal fat percentage significantly (P<0.05). Increasing dietary lysine increased the feed consumption in starter and weight gain, gain to feed ratio in grower and total period of the experiment (P<0.05). Increasing lysine in diet caused a significant increase in breast meat and tight yield, and percentage. Adding supplemental lysine reduced the N excretion in starter period significantly (P<0.059). N excretion reduced significantly by decreasing dietary protein (P <0.05). Dietary treatments had not significant effect on mortality percentage. The results of the present experiment indicated that with providing limiting amino acids and adding supplemental lysine to diet, the crude protein could be reduced up to 3 and 2 percent in starter and grower periods respectively. Reducing the crude protein had not adverse effect on the feed efficiency.

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In the current experiment seven catheterized broiler breeder hens were used at 60 weeks of age. Retention of ¹⁴CO₂ in the body of the hens following continuous infusion of NaH¹⁴CO₃ during each of tow-30-hr continuous infusion studies was determined. Oxidation rate plateau was established within two hours in each experiment. Recovery of ¹⁴CO₂ at the steady state in the first and second study were 91.09 and 87.55 percent respectively and were not significantly different. Mean breath ¹⁴CO₂ recovery was 89.32 percent and hence retention was 10.68 percent. Recovery of ¹⁴CO₂ in breath was not significantly affected by laying of egg or photoperiod. Recovery of ¹⁴CO₂ during the fed state was significantly lower than the fasted state. The results of this experiment indicated that, using of uncorrected data for the retained isotope into body, lead to 10.68 percent AA requirements underestimation in broiler breeder hens by indicator amino acid oxidation technique.