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Summary of full report
Amino Acid and Energy
Requirements
of Imported Brown Layer Strains
December 2000
RIRDC Publication No 00/179
RIRDC Project No: US-54A
Executive Summary
During the past decade egg producers in Australia have to a large extent discarded established layer strains in favour of new coloured overseas genotypes. These imported brown-egg strains produce considerably more egg mass and generally convert feed to egg mass more efficiently than local strains, so it might be expected that their nutritional requirements are more exacting than those of local strains.
However, no estimates of the nutritional requirements of these “imported” strains have been made in Australia using Australian diets. Previous attempts to evaluate the performance and to determine the dietary nutrient specifications of these overseas strains in the Australian environment have been impeded by a high mortality problem related to Marek’s disease and cannibalism. The recent reduction in the incidence of Marek’s disease provided an opportunity to evaluate the nutrient requirements of these imported stocks under Australian conditions.
The aim of this project was to improve the economic value of imported commercial brown layer strains by defining their protein, amino acid and energy requirements under Australian conditions. IsaBrown laying hens were used as representative of the new imported coloured strains. The aim of the energy study was to determine how variation in dietary energy concentration influenced the performance of IsaBrown laying hens housed in single-bird and two-bird cages in an open-sided, flat-deck, cage shed in southeast Queensland. The shed was provided with adjustable shutters and ridge-vent, and thermostatically controlled fans and foggers.
Three dietary ME levels were fed to IsaBrown hens housed in single-bird and two-bird cages. The nominal ME values of the diets were 10.6 (L), 11.4 (M) and 12.2 (H) MJ/kg, while the ME values obtained by metabolism studies, using cockerels, were 9.78±0.29 (L), 11.41±0.25 (M) and 12.52±0.37 (H) MJ/kg. Amino acids, total protein, calcium and phosphorus were maintained in approximate proportion to the nominal ME levels.
The results indicated that the IsaBrown bird is inefficient at adjusting feed intake to meet energy requirements. The ME intake on diet H appeared to be excessive while intake of ME and/or other nutrients on diet L may have been too low to support maximum egg mass output. Feed intake of diet L, which was a very bulky (low density) diet, was substantially lower than predicted on the basis of energy requirement of the birds and energy content of the diet, suggesting that dietary bulk was a limiting factor. Nevertheless profit was maximised with this diet under current Queensland cost/price conditions.
Thus, it appears that for imported brown egg layers, diets with a low to medium energy content and proportionately lower protein content are likely to be more economical than higher density diets in most circumstances. The results suggest that a minimum dietary AME of 11.4 MJ/kg appeared to be required for optimal biological efficiency. This ME concentration is similar to the current breeder recommendation.
The diets used to examine the protein, lysine and methionine requirements during lay contained calculated ME concentrations of 11-11.25 MJ/kg. Diets containing 160 or 180 g crude protein/kg in one experiment, lysine concentrations ranging from 7.35 to 8.95 g/kg in a second experiment and methionine concentrations ranging from 2.83 to 3.83 g/kg in a third experiment were fed to IsaBrown hens in single- and 5-bird cages. In the first study the effect of feeding a pre-layer diet containing 2 g Ca/kg from 15 to 18 weeks of age was also examined to determine whether this procedure influenced subsequent feed intake.
These three studies were conducted in a newly built, high-rise, windowless layer house built from insulated panels in which computerised control of fans and evaporative cooling pads allowed the temperature to be maintained below heat-stress levels. The results clearly showed no advantage from increasing the calcium concentration of a grower diet for the three weeks prior to sexual maturity.
Likewise, the production advantages of increasing the layer diet from 160 to 180 g/kg were limited to a small, significant increase in egg mass output due mainly to a significant increase in egg weight.
The lysine and methionine requirements for hens in single cages were lower than for hens in multiple 5-bird cages. The requirements of the latter hens are more applicable to the commercial situation and were shown to approximate 970 mg lysine/day and 430 mg methionine/day. At the calculated dietary ME concentration of 11.25 MJ/kg used in these studies these intakes were attained with dietary concentrations of 7.75 g lysine/kg and 3.33 g methionine/kg.
Important observations from the lysine study were that increasing the dietary lysine concentration to 8.15 g/kg improved albumen quality and consistent, if non-significant, increases in serum total immunoglobulin titres were observed with increases in dietary lysine. The latter response contrasted with that observed in the methionine study where increases in dietary methionine concentration reduced albumen quality and gave non-significant reductions in serum total immunoglobulin titres.
The main difference between hens in single- and multiple- bird cages was the higher mortality, mostly resulting from cannibalism, observed in the multiple cages. This had a significant effect on hen-housed egg production in the lysine and methionine studies. In both studies this difference due to cage density was ameliorated by increasing the dietary concentration of lysine and methionine, respectively.
Other effects of cage density were in the lysine study where hens in the multiple-bird cages produced eggs with significantly lower % shell but significantly improved albumen height and in the methionine study where hens in multiple-bird cages again produced eggs with significantly lower % shell. There was a tendency (P=0.081) in the methionine study for hens housed in multiple-bird cages to have increased serum total immunoglobulin titres compared to hens in single cages.
Current breeder recommendations
for the IsaBrown hen consuming a diet containing approximately 11.4 MJ
of ME/kg are 19.5 g crude protein, 880 mg lysine and 430 mg methionine/day.
Estimates based on hen-housed egg production in 5-bird multiple cages in
the present work confirm these recommendations for crude protein and methionine
but are considerably higher than the suggested requirement for lysine (970
vs 880 mg/day).
 
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