Plant-based Diets for Heavy Hen Turkeys

There is an increased consumer demand for poultry to be fed diets free
of animal by-products.  Ingredients such as full-fat canola, full-fat
soybeans, and canola and soybean oils have the potential to replace
animal-based sources of protein and metabolizable energy; however these
need to be further evaluated.

There is an increased consumer demand for poultry to be fed diets free of animal by-products.  Ingredients such as full-fat canola, full-fat soybeans, and canola and soybean oils have the potential to replace animal-based sources of protein and metabolizable energy; however these need to be further evaluated. 

Turkeys have a high protein requirement, and therefore high dietary costs.  Research is required to evaluate potential least-cost feed ingredients that not only help meet increasing consumer demands for the removal of animal by-products, but that can also result in potential decreased feed costs for the turkey producer.

Research conducted by the Atlantic Poultry Research Institute (APRI) indicated that roasted full-fat soybeans can partially or totally replace soybean meal in broiler turkey diets. However, fish meal and tallow were included in the diets as concentrated sources of protein and energy. 

In addition to being a high quality protein source, oil retained within the whole bean makes soybeans an excellent source of energy.  However, raw soybeans contain trypsin inhibitors, which limits their use because this makes them less digestible.  The soybeans have to be heat treated before use to destroy the inhibitor.  One such method of processing raw soybeans is dry roasting.

There are a number of farms with this capacity as well as commercial grain roasting units which have emerged in the Atlantic region.  Extrusion offers an alternative method of processing the raw soybeans where roasting is unavailable, but this is a less common processing option.  

Full-fat canola could be used as a possible alternative to full-fat soybeans, however the use of full-fat canola seeds in poultry diets has not been extensively studied.

The Trial
Turkey poults, raised for meat, were fed either one of four dietary treatments varying in the supplemental protein and energy source: poultry by-product meal + poultry grease (control), full-fat canola + canola oil, flame-roasted full-fat soybeans + soy oil, or extruded full-fat soybeans + soybean oil. 

Locally grown and roasted (130.5C) full-fat soybeans were purchased for the trial.  Locally grown full-fat soybeans were also purchased and were extruded (120C) on the Nova Scotia Agricultural College (NSAC) farm.
All diets were formulated to contain the same amount of protein and energy. 

Results
At 56 and 69 days of age, dietary protein and energy sources affected body weights (Figure 1) of the turkeys.  At both 56 and 69 days of age, birds fed the canola-based diet as well as the roasted soybean-based diet were heavier than those fed the other two diets.  In addition, birds fed the control diet were heavier than those fed the extruded soybean-based diet.  Birds fed the extruded soybean-based diets consumed less feed then those fed the other diets during the 29-56 and 57-69 days periods (Figure 2). 
Many of the beans appeared to become blackened from the extrusion process.  This may have affected the palatability of the beans, resulting in a reduced appetite for the diets containing the extruded soybeans.

Dietary treatment did not affect feed conversion, indicating that the nutritional value of the extruded soybean-based diets did not affect the consumption rate of these diets (Table 1). However, as the birds aged, the inclusion level of the extruded soybeans in the diet increased indicating the affect on feed consumption was probably due to the extrusion process.

The on-farm extrusion of the soybeans was not easily controlled; however, commercial extrusion units are available in certain regions and can offer greater control for this process.

Industry Impact
Common supplemental sources of protein for poultry diets include soybean meal, fish meal and meat meals.  Fats and oils are commonly added to poultry diets as concentrated sources of energy. 

To provide the processor and consumer with an alternative to meat based diets the use of soybean and canola processed in different ways can be considered. Replacing meat byproducts with either full-fat canola plus canola oil or roasted soybeans plus soy oil
resulted in heavier body weights. In addition, the use of canola-based diets may prove to be more economical than meat-based diets (Table 2).

However, current market prices of ingredients will determine least-cost opportunities of plant-based diets for poultry.
Researchers: J.L. MacIsaac (APRI), D.M. Anderson, S. MacPherson, B. Ratheberger (Nova Scotia Agricultural College). For more information, E-mail: JMacIsaac@nsac.ca

References:

MacIsaac, J.L., Burgoyne, K.L., Anderson, D.M., and Ratheberger, B.R.  2005.  Roasted full-fat soybeans in starter,
grower and finisher diets for female
broiler turkeys.  J. Appl. Poult. Res. 14:116-121.