Effect of early nutrition on fattening and growth of broiler chicks at 7 weeks of age

Differential effect of age on metabolisable energy content of high protein-low energy and low protein-high energy diets in young broiler chicks

1. An experiment was carried out with 6-d old male broiler chicks in an attempt to understand better the effect of age on dietary AMEn of high protein-low energy (HPLE) and low protein-high energy (LPHE) diets which are used in the determination of the AMEn content of grains when substituted for the entire diet. The experiment was carried out in a split-plot design in which the effects of 2 diets (HPLE-reference and LPHE-test, containing maize) on food intake, faecal excretion, dietary AMEn and the utilisation of the nutrients were evaluated in 3 age periods (A = 11-13, B = 15-17 and C = 20-22 d of age). 2. Chicks fed on the HPLE diet consumed significantly less food than those fed on the LPHE diet during periods A and B, but not in C. They also produced a significantly larger amount of droppings during periods B and C. Food-to-droppings ratio, which was consistently and significantly lower in chicks fed on the HPLE diet, decreased markedly in period C only in these birds. 3. Absolute and relative retention (RR) of dry matter (DM) and starch, and RR of nitrogen (N) from birds fed on the HPLE diet, were consistently and significantly lower than from those fed on the LPHE diet, but fat retention (absolute and relative) was higher. RR of DM and of N in period C was significantly lower than in periods A and B, while RR of fat and of starch was not affected by age. The effect of age on RR of N was observed only with the HPLE diet. 4. AMEn of the HPLE diet, but not of the LPHE diet, in period C was significantly lower than in periods A and B, resulting in a significant interaction between age and diet and a general reduction with age. The calculated AMEn contents of the maize in periods A and B were essentially the same (14.91 and 14.85 MJ/kg, respectively), and lower than in period C (15.28 MJ/kg). It is concluded, therefore, that because of its effect on AMEn of the HPLE reference diet in chicks older than 17 d, bird age is of considerable importance in the determination of AMEn in grains when substituted for the entire diet.

A modified bioassay for energy utilization in newly hatched chicks. 2. Determination of feed input and procedures to estimate endogenous energy loss

Two experiments were conducted to develop a modified bioassay system to determine bioavailability of dietary energy in newly hatched chicks based on the TME assay system. Broiler chicks aged 0, 1, 3, 7, and 14 d old were force-fed or consumed feed ad libitum following 24 h of feed withdrawal to determine the optimum level for feed input. In the second experiment, 7-d-old chicks were force-fed various diets and feedstuffs at three levels following 24 h of feed deprivation. Linear regressions (P < .01) between energy input (X) and excreted energy (Y) were demonstrated irrespective of diets and feedstuffs at any age in Experiments 1 and 2. Endogenous energy loss (EEL), estimated by the regression method and approximated over a small range was lower than EEL estimated using feed-deprived chicks. The TME and TMEn values of diets and feedstuffs calculated using EEL estimated by the regression method were not modulated by the feed input level, whereas those estimated by feed-deprived chicks tended to increase with decreases in the level of feed input. Thus, a modified method for determination of energy utilization in newly hatched chicks based on TME assay is proposed, which seems to have proper physiological and chemical bases.

A modified bioassay for energy utilization in newly hatched chicks. 1. Determination of optimum durations for feed withdrawal and excreta collection

Three experiments were conducted with view of a more suitable bioassay system for determination of energy utilization in newly hatched chick based on the TME assay system. The optimum duration for feed deprivation prior to tube feeding was determined with chicks aged 0, 2, 6, and 13 d old. In order to determine an appropriate duration for excreta collection after feeding, chicks deprived of feed for 24 h were force-fed and energy excretion was monitored every 12 h for the next 72 h. Irrespective of the age, energy excretion decreased to a low level at 24 h after feeding and then reached a constant rate: the endogenous energy excretion. In 0- and 2-d-old chicks, N excretion tended to increase from 12 h after commencement of feed withdrawal. On the other hand, energy excretion in the chicks force-fed paste or pellet of basal diet attained constant rates beyond 24 h after force-feeding at all ages, and the rates of excretion were almost comparable to the endogenous energy excretion for the corresponding age. In the chicks force-fed a high-fat diet, however, 36 h was required for the excreted energy to attain a constant rate. The increase in N excretion was also observed following 24 h after feeding in 1- and 3-d-old chicks. Deutectomy at 1 d posthatch modified the patterns of energy and N excretion after the commencement of feed withdrawal but not TME and TMEn values of diets. A modified bioassay system for the determination of energy utilization in newly hatched chicks based on TME assay system is proposed.

Lack of interactive effect of nicarbazin and dietary energy-to-protein ratio on performance and abdominal fat pad weight of broiler chicks

An experiment was carried out, in a factorial arrangement, with female broiler chicks during the period from 8 to 49 days of age. Combined effects were evaluated of dietary energy-to-protein ratio (E:P; 130 vs. 170 from 8 to 28 days of age and 140 vs. 190 from 28 to 49 days of age) and nicarbazin supplementation (0 vs. 125 mg/kg) on performance and fattening. At 49 days of age, feed intake was not affected either by dietary E:P or by nicarbazin supplementation. The latter significantly depressed weight gain (P less than .01) and feed efficiency (P less than .001), but did not affect abdominal fat pad weight. The wide E:P significantly decreased feed efficiency (P less than .01) and increased abdominal fat pad weight (P less than .001). Neither of the parameters was affected by the interaction between nicarbazin and dietary E:P. It was suggested that the growth-depressing effect of nicarbazin was due to its effect on increasing the metabolic rate, an increase which did not affect fattening as measured by abdominal fat pad weight.