Soybean meal is the main plant protein source in broiler diets due to its high protein content, balanced amino acid profile, and digestibility. However, Australia’s heavy reliance on imports has provoked interest in local alternatives. Recent research investigated whether soybean meal could be partly or fully replaced by a combination of field peas and canola without compromising broiler growth, digestibility, or carcass traits.
This feeding trial involved 300 Ross 308 (mixed sex) broilers, allocated to 60 pens, with each dietary treatment examined in 10 replicated cages of 5 birds each. The study tested three levels of soybean meal inclusions – standard, medium, and low/nil, either with or without field pea inclusion.
Conducted over a 42-day post-hatch period, the trial encompassed four commercial phases: starter (0-10 days), grower (11-24 days), finisher (25-35 days), and withdrawal (36-42 days). The experiment incorporated increasing levels of field peas at 50, 80, 100, and 120 g/kg, replacing nearly 45%, 60%, 100%, and 100% of soybean meal, respectively. This variability in soybean meal levels necessitated adjustments in NBAA inclusion and total dietary crude protein. Researchers assessed growth performance, nitrogen retention, and nutrient digestibility during the experiment.
For producers, nutritionists, and feed manufacturers, these findings have considerable implications. The study concluded that field peas could safely be included at 5-12% of the diet, with the complete removal of soybean meal during later growth phases without compromising bird performance.
Poultry World spoke to Milan Kandel, a PhD candidate in poultry nutrition at the Poultry Research Foundation at The University of Sydney, who led these trials.
Why Field Peas and Canola?
Field peas and canola products were chosen primarily due to their availability in Australia. Notably, field peas contribute to improved soil nitrogen management, making them an important rotational crop in Australian farming systems.
Nutritionally, field peas yield approximately 232 g/kg crude protein and 488 g/kg starch. They possess a relatively high amylose-to-amylopectin ratio that may slow starch digestion, enhancing nutrient utilization and feed conversion efficiency in broilers.
Formulation Tips for Commercial Nutritionists
Commercial diet formulation should aim for field pea inclusion levels of around 5% in starter, 8% in grower, 10% in finisher, and 12% in withdrawal diets. Notably, the finisher and withdrawal diets containing field peas showed zero soybean meal, yet maintained broiler performance.
The findings indicate a phased feeding strategy, progressively increasing field pea inclusion, paired with appropriate balancing of non-bound amino acids is a practical way to reduce soybean meal use without compromising chicken performance.
Improvements in Weight Gain and Feed Conversion Rate
Remarkably, the inclusion of field peas resulted in a 2.9% increase in weight gain and a 2.04% reduction in feed conversion rate (FCR) from 0-42 days post-hatch, regardless of soybean meal inclusion. Notably, there were no significant differences in apparent starch and protein digestibilities between diets with or without peas.
Potential Tipping Points in Pea Inclusion
Within this trial, field peas were included up to 12%, with no evidence of diminishing returns or negative impacts. Therefore, within tested levels, peas appeared well tolerated.
Assessment of Meat Quality Traits
Assessment of meat quality revealed no significant effects on breast meat yield, including both pectoralis major and pectoralis minor, leg quarters, or relative fat pad weight.
Long-Term Health Implications
These alternative protein diets could have significant long-term health implications, especially concerning litter quality and welfare outcomes such as hock burns and footpad dermatitis. Previous studies indicated that litter moisture was higher in soybean meal diets compared to those rich in canola, leading to fewer welfare issues.
Increased nitrogen fixation associated with field peas may also improve environmental outcomes and support overall poultry welfare.
Estimating Environmental Impact and Feed Cost Savings
The study highlighted that substituting soybean meal with field peas and canola enhances nitrogen retention, translating into lower nitrogen losses to the environment. Although direct measurements of nitrogen excretion were not conducted, improved nitrogen retention suggests a promising environmental benefit.
From a cost standpoint, replacing soybean meal with field pea-canola blends yielded consistent savings. Even though higher inclusion of non-bound amino acids can increase diet costs, pea-based diets remain economically favorable.
Future Research Directions
The study’s authors are pursuing further investigations into other local or alternative protein sources, including faba beans and various canola products, to enhance sustainability and reduce reliance on imported soybean meal.
*This study is part of the AgriFutures Chicken Meat Consortium’s Nutrition, Gut Health, and Environment project and has been published in the journal Animal Nutrition.
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