Agriculture Reference
In-Depth Information
estimated amino acid to energy ratios. However, the preferred option to establish dietary
concentration of amino acids is to consider a factorial (modelling) approach whereby
observed daily energy intakes, sow performance, and environmental conditions are all
considered (e.g. NRC, 2012).
6.4.4
Protein sources and quality
The nutritional quality of a protein source for humans or animals may be described as the
capacity for this protein to meet requirements for amino acids and nitrogen (Schaafsma,
2005). Protein quality differs widely amongst feed ingredients and is defined by its amino
acid composition and bioavailability. The proteins of cereal grains are deficient in key
essential amino acids, therefore, high-protein ingredients are used in combination with
cereal grains to correct for these amino acid deficiencies. Nonetheless, the most common
cereal grains found in sow diets, such as corn, barley, wheat and sorghum, provide up to
60% of the total amino acid requirements (NRC, 2012). Common plant-based protein
sources for sow diets include soybean meal, field peas, canola meal, sunflower meal, and
grain co-products such as DDGS, corn gluten feed, and corn gluten meal.
Soybean meal is the by-product of oil extraction from soybeans. During dehulling and
subsequent oil extraction, soy protein is heated, thereby reducing the heat sensitive anti-
nutritional factors, most notably trypsin-inhibitors which are present in raw soybeans.
There are two categories of soybean meal: high protein, dehulled solvent extracted
soybean meal which contains 49 to 50% crude protein (CP), and low protein soybean
meal which contains 44 to 46% CP and a greater fiber content. Properly processed
soybean meal is a consistent product and is often the most economical source of amino
acids for sows. Furthermore, soybean meal is the only commonly used plant protein that
provides an amino acid quality similar to that of animal proteins. Because of its favorable
amino acid digestibility and high lysine content, soybean meal can be included as the
sole protein ingredient in diets for both gestating and lactating sows while minimizing
nitrogen excretion in urine and feces (Pettigrew
et al.
, 2008). However, when diets are
properly formulated and prepared, a variety of other protein sources can be included in
sow diets without compromising sow performance. Therefore, the use of various protein
sources should be driven primarily by their nutrient value and cost, and assessed using
least-cost feed formulation systems (Patience
et al.
, 1995).
Where growing conditions are conducive to field peas (
Pisum sativum L.
), this ingredient
is an excellent partial substitute for soybean meal or corn in sow diets. Contrary to
soybean, field peas contain very low concentrations of anti-nutritional factors and as
such can be fed raw (Thaler and Stein, 2003). Thermal treatment however does increase
ileal digestibility of amino acids as well as that of starch and energy (Stein and Bohlke,
2007). Depending on the variety, field peas are a good source of protein (23.4%) and
lysine (1.7%), but are marginally deficient in methionine and tryptophan, with lower
standardized ileal digestibility for tryptophan and the sulfur amino acids when compared
with soybean meal (Stein
et al.
, 2004). The recommended inclusion levels are 16 and 24%
for gestation and lactation, respectively.
