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By Marcus Kenny and Carolyne Kemp, Technical Development Managers - Nutrition, Aviagen
Broiler compound feed prices have fluctuated considerably over the last few months as the price of wheat and soya has fluctuated. When raw materials prices increase it is tempting to reduce the cost of the finished feed by decreasing nutrient levels.
Reducing protein levels
Reducing protein levels (available amino acids) in the diet of Ross 308 broilers to 85% of the current recommendation had the following effect to 41 days of age (see Fig 1).
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Fig. 1
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Ross 308 standard
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Control diet (85%)
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Liveweight
(kg)
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2.93
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2.55
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FCR
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1.91
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2.01
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While bodyweight and FCR will deteriorate significantly as protein levels are reduced the cost of the diet will be lower so the effect on the overall financial performance of the flock needs to be assessed.
Reduced protein on processing performance
Dietry protein levels also affect processing yields there being a reduction in carcass and breast meat yield when levels are reduced (fig 2).
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Fig. 2
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Ross 308 standard
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Control diet (85%)
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Carcass
yield (%)
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68.2
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67.2
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Breast
meat yield (%)
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17.8
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16.2
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As protein levels are decreased the cost per kg of carcass and breast meat increases (fig 3).
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Fig. 3
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Ross 308 standard
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Control diet (85%)
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Feed
cost/kg carcass
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0.46
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0.48
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Feed
cost/kg breast meat
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1.78
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1.98
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Financial performance
Assuming the control diet costs approximately £160/t a 15% reduction in protein level will save about £6.50/t (about 4%). The impact of a lower protein concentration in the diet on margin after feed cost calculated using both current and high feed costs (+10%) is shown in the graph (see fig 4). These data show that lower protein levels in the diet give a reduced margin when applied to either current or high feed costs.
Identifying the optimal protein level in the diet
To assess the impact of protein levels in the diet on broiler performance Aviagen nutritionists have evaluated the protein response of the Ross 308 broiler in a series of trials. This is The Balanced Protein Project which will produce a calculator which allows the integration of local raw material prices with knowledge of the Ross broiler to establish appropriate dietry amino acid levels to maximise margin to meet the objectives of a business.
The calculator can also be used as a guide to identify the margin over a range of amino acid levels. Using the same revenue bases as the previous examples the margins over a range of protein levels from 70% to 130% of Ross 308 recommendations were investigated. The amount of dietry protein needed to maximise profitability varies depending upon whether a business is set up to sell live birds, eviscerated carcass or portions.
To maximise profitability for as hatched broilers grown to 2.5kg, a protein equivalent to 100% of the Ross manual is required. Eviscerated bird margin is maximised at 106% and portioned bird margin at 120% of the Ross manual recommendation.
The key point is that the optimal amino acid density of the diet is dependent on the objective of the business. The optimal amino acid density for portions is much higher than current recommendations (120%), because the revenue figure is higher than either liveweight or eviscerated carcass revenue. However the other reason for the higher optimal amino acid levels for portion margin is the high breast meat yield response of the Ross broiler to increased amino acids.
Breast meat yield
The relative breast meat yield in male broilers increases as amino acid levels increase confirming that the Ross bird clearly responds to increased amino acids even above current recommendations.
An additional factor influencing the economic response is the high liveability experienced with Ross broilers. Increasing diet nutrient density will increase growth rate and liveweight for age. The Aviagen pedigree selection process has minimised the incidence of metabolic related diseases even at high growth rates. Hence feeding higher levels of nutirents to the Ross bird for optimal performance will not compromise liveability or the welfare of the bird.
Factors affecting optimal amino acid density
- Protein raw material price increase
Optimal amino acid density will change if the cost of balanced proteins increases. This situation is likely to arise if the price of any of the protein raw materials increases. If alternative protein sources are limited then the situation is likely to be exaggerated. Figure 5 shows the effect of increased protein prices on optimal amino acid density.
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Fig. 5 Optimal amino acid density for 2.5kg as hatched broilers
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Current
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Increased protein raw material price
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Liveweight
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100%
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90%
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Eviscerated
carcass
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106%
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94%
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Portion
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120%
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109%
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- Change in processing liveweight
Feed and protein prices are not the only influence on optimal amino acid density. A change in kill weight will impact on the optimal amino acid density. In the example (Figure 6) the optimal amino acid density for liveweight remains unchanged. As kill weight increases the potential for breast and portion growth increases hence optimal amino acid density for eviscerated carcass and portion margin increases as kill weight increases.
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Fig. 6 Optimal amino acid density for 2.5kg as hatched
broilers
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1.7
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2.5
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3.0
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Liveweight
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100%
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100%
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100%
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Eviscerated
carcass
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104%
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106%
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115%
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Portion
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113%
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120%
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122%
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As revenue price changes the optimal amino acid density remains the same for liveweight and changes for eviscerated carcass and portions. Figure 7 shows the optimal amino acid density when all revenue process are increased by 20%. Optimal amino acid density increases and decreases when revenue process increase and decrease.
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Fig. 7 Optimal amino acid density for 2.5kg as hatched
broilers
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-20%
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100%
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+20%
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Liveweight
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100%
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100%
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100%
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Eviscerated
carcass
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102%
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106%
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110%
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Portion
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117%
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120%
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123%
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