A comparison of different drying techniques for energy and amino acid analyses of poultry excreta

1. Broilers were fed on wheat‐casein or wheat‐soyabean meal diets and the excreta collected after 12 and 24 h. Samples of excreta were freeze dried or dried in a force draught oven at 60 or 80 °C.

2. Drying procedure and collection time significantly influenced the determined energy and nitrogen concentrations of the excreta.

3. Drying excreta in an oven at 60 °G proved at least as effective as freeze drying for the majority of amino acids.     

Influence of temperature during growth on responses of hens to high or low temperatures during lay

1. Commercial pullets were grown at cool (10°‐20°C) or hot (25°‐35°C) temperatures to similar bodyweights at 18 weeks of age. Between 18 and 50 weeks the birds were either kept at the same temperatures as during growth or transferred to the alternate temperature.

2. Birds kept at the cool temperatures throughout life ate most food and gave the best production during lay. Minimum food intake and poorest performance were obtained with birds kept at the hot temperatures throughout life.

3. Performance in the hot environment during lay was improved by rearing birds in the cool environment, the response being related to an increased food intake. Food intake in the cool environment during lay was reduced, with only minor effects on performance, in birds which had been reared in the hot environment.

4. The results of the present study show that production responses during lay are affected by the temperatures experienced by hens during both growth and lay.     

The choline and sulphur amino acid requirements of broiler chickens fed on semi‐purified diets

1. Growth and food conversion efficiency of broilers were reduced at low dietary choline concentrations. These effects were accentuated by low dietary total sulphur amino acids (TSAA).

2. Increased mortality, perosis and other pathological changes involving a number of tissues were observed in birds fed on a low‐choline diet.

3. Methionine replaced part of the dietary requirement for choline at low dietary choline concentrations.

4. High dietary concentrations of choline (> 1 750 mg/kg) increased the requirement for dietary TSAA.

5. Increasing the dietary choline while maintaining the TSAA at an inadequate level may decrease performance.     

Effect of dietary amino acids and metabolisable energy on the performance of broilers kept at high temperatures

Increasing dietary metabolisable energy (ME) at particular amino acid: ME ratios significantly improved growth and food utilisation of broilers kept at moderate (18 to 26 degrees C) and high (25 to 35 degrees C) ambient temperatures during the finishing period from 22 d of age. The optimum amino acid: ME ratio varied with dietary ME concentration in the hot, but not in the moderate environment. Relatively greater increases in food intake and growth rate occurred in the hot environment when dietary ME was increased and the amino acid: ME ratio was reduced. The minimum rate of food intake did not coincide with the period of maximum temperature. Increasing the dietary protein at particular ME concentrations had little or no effect on the food intake and growth rate of birds kept at high temperatures. Supplementation with dietary fat had no beneficial effect on performance at high temperatures. The rectal temperatures of birds in the hot environment increased with age and, towards the end of the finishing period, when higher energy diets were fed.     

Free-choice feeding of broilers at high temperatures

Broilers fed complete diets to 21 but not 44 d of age grew faster with a better efficiency of food utilisation than broilers given a free-choice selection of the cereal and protein components. When finisher diets, varying in metabolisable energy (ME) and amino acid:ME ratios, were fed at high ambient temperatures (25 to 35 degrees C) broilers on the free-choice system selected similar amino acid:ME intake ratios, which were lower than the ratios contained in the complete diets. Differences in broiler performance between 22 and 44 d of age reflected variations in ME rather than amino acid intake.     

Responses of sexually-maturing pullets to self-selection feeding under different temperature and lighting regimens

1. Pullets allowed to self-select nutrients from a protein concentrate and either a separate complete diet or cereal-based, energy-rich mixture showed preferences for protein and energy which varied in relation to the time of their onset of lay. 2. The selected protein:metabolisable energy (ME) intake ratio increased from 14 g protein per MJ of ME 2 to 3 weeks before sexual maturity to approximately 19 g protein per MJ of ME at and after sexual maturity. 3. This response to self-selection feeding was consistent with different temperatures, lighting patterns and dietary manipulations. 4. Egg mass output was improved by self-selection feeding at hot (25 degrees to 35 degrees C) temperatures in experiments 1 and 2 and at ambient temperatures in experiment 3. No beneficial response in egg mass from self-selection feeding was observed at cold (6 degrees to 16 degrees C) temperatures in experiment 1. 5. Providing 2 h of additional light during the dark (cool) part of the day, with or without 2 h of darkness in the middle of the extended light (hot) period, had no effect on the egg mass output of pullets at hot (25 degrees to 35 degrees C) temperatures.     

Influence of dietary energy, nutrient density and environmental temperature on pullet performance in early lay

1. Alterations in dietary metabolisable energy (ME) concentration had a limited influence on food and nutrient intakes and egg mass output of hens in early lay kept at the prevailing air (10 degrees to 24 degrees C), cold (6 degrees to 16 degrees C) or hot (25 degrees to 35 degrees C) temperatures. 2. Energy intakes were not improved by increasing the dietary concentrations of nutrients other than energy. 3. At prevailing air and cold temperatures all dietary ME-nutrient density combinations allowed hens to meet the recommended daily protein intake but only hens fed the most concentrated diets were able to meet this recommendation at hot temperatures. 4. Even the highest intakes of ME and protein achieved at hot temperatures failed to increase egg mass output to the values attained on any diet at cold temperatures.     

The necessity of supplementing laying hen diets with linoleic acid

Results from four experiments with laying hens have been re‐examined using the means of individual 28‐d periods during egg production to investigate the influence of the developing ovary and linoleate storage during growth on the linoleic acid requirement of the laying hen.

Apart from a possible beneficial effect during the first few weeks of production, little increase in egg weight occurs when birds are fed on conventional rearing diets and then fed on laying diets containing linoleic acid in excess of requirement.

After depletion of linoleate reserves, dietary supplementation with linoleic acid significantly increases egg weight at any age.

The necessity of supplementing diets for laying hens with linoleic acid is discussed.     

Interactions between wheat and other dietary cereals with respect to metabolisable energy and digestible amino acids

Small, varying improvements in apparent ileal amino acid digestibilities were obtained when wheat was combined with certain other cereals in broiler diets. Synergistic interactions, sometimes resulting in large improvements in the apparent metabolisable energy (AME) contents of the diets, were also observed with certain cereal combinations. Combining wheat with maize or oats enhanced the utilisation of dietary energy and amino acids.