Broiler growth response from practical low-protein diets supplemented with urea and diammonium hydrogen phosphate.

In an experiment with 480 Hybro chickens initially 1 day old, 6 starter diets were given to appetite for the first 4 weeks: (A) 23.5% crude protein, rich in essential amino acids; (B) 20.6% crude protein, containing essential amino acids to meet requirements; (C) B + 1% urea; (D) B + 0.5% urea; (E) B + 2.2% diammonium hydrogen phosphate (DAP); (F) B + 1% DAP. The finisher diets were: (A) 20% crude protein; (B) 18% crude protein with essential amino acids to meet requirements; (C) B + 0.7% urea; (D) B + 0.35% urea; (E) B + 1.5% DAP; (F) B + 0.75% DAP. Adding 1% urea or 2.2% DAP to the starter diets decreased growth and feed conversion significantly, whereas 0.5% urea or 1.1% DAP had no significant effect on growth and feed conversion, compared with control A. Adding 0.7 or 0.35% urea to the finisher diets decreased growth and feed conversion compared with diet A. Whereas the diet containing 0.75% DAP gave better results than that containing 1.5% DAP, there was no significant effect on growth, compared with group A. At 7 weeks of age, low concentrations of urea or DAP did not produce results that differed significantly from control diet B as far as feed conversion was concerned, but they were not comparable to control diet A. (Abstract retrieved from CAB Abstracts by CABI’s permission

Effect of dietary levels of calcium on performance of pullets and layers, physical characteristics of the egg, and calcium and phosphorus in plasma and bone.

From 16 weeks old 432 chickens of a medium-heavy strain were given diets based on maize, soya bean oilmeal and barley with 1.5, 3.7 or 5.0% calcium and about 0.8% phosphorus. Diets supplied metabolizable energy 12.12, 11.35 or 10.96 MJ/kg. After a laying phase at 23 weeks old when they reached 50% production, chickens given 5.0% Ca weighed significantly less and tended to eat more than those given 1.5 or 3.7% Ca. Ca in plasma did not differ among groups but inorganic P was greater in those given 1.5% Ca than in others. During the laying period of 22 weeks egg production was greatest with 3.7% Ca. Feed intake, egg shell thickness, relative density of egg shell and proportion of shell increased with increasing Ca in the diet. Egg weight, albumen index and yolk index did not differ among groups. Tibial ash and breaking strength of tibia increased with increasing Ca in the diet. (Abstract retrieved from CAB Abstracts by CABI’s permission

Egg shell quality and microstructure as affected by vitamin C, other feed additives and high environmental temperatures

The effects of climatic stress on egg formation (weight, shape, formation period, clutch size and blood calcium) and shell quality were estimated in White Leghorn and White Plymouth Rock hens. Constant environments were used with 85°F 75- 80% r.h., 75-77°F 50-60% r.h. and 55°F 50-60% r.h. as well as a fluctuating environment with 10 h (day) 85°F 75-80% r.h. and 14 h (night) 65-70°F 50-60% r.h. The effects of dietary vitamin C (50 or 100 mg/kg feed), NaHCO 3 2.1 % and antibiotics were also tested.The author concluded the following. Fluctuating temperature had no effect. In heat-stressed hens vitamin C improved the diminished shell quality and raised blood calcium.At 75°F vitamin C and NaHCO 3 increased egg weight and shell quality. Combinations of antibiotics improved egg and shell weight. Microscopy of ground sections of the shell showed that heat diminished shell thickness and impaired the crystal structure of the calcified shell; vitamin C addition improved shell thickness