JWSS - Journal of Water and Soil Science

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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 with a 33 factorial arrangement in a completely randomized design with 450 day-old broilers was conducted to study the effect of energy level and time of change from starter to finisher diets on performance and economic aspects of broilers. Broiler chickens were fed at three levels of dietary energy (2800, 3000, and 3200 KcalME/Kg) from 1-42 days of age. Starter and finisher diets were changed at 16, 21, and 26 days of age and then finisher diets were fed up to 42 days of age. The effect of diet energy and changing time from starter to finisher diets on body weight and feed conversion at 26 days of age were significant (P<0.01). By increasing energy level and changing time from starter to finisher diets, at this age, body weight increased and feed conversion ratio decreased. Energy conversion decreased by decreasing the levels of energy content of diet and increasing time of change from starter to finisher diets (P<0.01). At 42 days of age, the effects of diet energy and changing time from starter to finisher diets did not show any significant effects on feed and energy conversion in contrast, body weight at this age increased significantly as a result of increasing time of change from starter to finisher diets (P<0.05). From 1-42 days of age, the interaction between diet energy and changing time from starter to finisher diets on feed and energy conversion was significant (P<0.05). The results from this study suggest that increasing diet energy and changing time from starter to finisher diets for producing broilers with less than 2 kg will improve their general performance.

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Digestible lysine and sulfur amino acid (SAA) requirements of Ross male broilers were determined during the starter period in two experiments. Broilers were fed a control corn-soy diet (3200 kcal MEn/kg and 23% CP) for 6 days and then randomly assigned to dietary treatments until 16 days of age. The basal diet containing 19% CP was prepared in order to be deficient in lysine for experiment 1 and SAA for experiment 2. Seven graded increment levels of L-lysine HCl or Dl-methionine were added in absences of starch in experiment 1 and 2, respectively. All diets contained 3200 kcal MEn/kg and all essential amino acids, except for the test amino acid, were 10% higher than the NRC (1991) recommendations. The digestible lysine requirements of broilers based on broken-line and exponential models were 1.04 and 1.01%, respectively. The digestible SAA requirements for the mentioned models were 0.846 and 0.841%, respectively.