Using green canola seed as an alternative feed source for pigs

Friday, December 5, 2014

Can green canola seeds, which are rejected for human consumption, be effective in pig diets? The answer seems to be a qualified 'yes'

by JANICE MURPHY

Feed costs represent upwards of 75 per cent of the cost of raising a grower-finisher pig to market. The Ontario agriculture ministry's August 2014 Swine Budget estimates feed costs at $85.75 of the $110.60 total cost, based on a corn-soybean meal diet. Fluctuations in corn and soybean prices, accompanied by the pig's unique ability to handle many types of ingredients, has always pushed the swine industry into considering alternatives to conventional energy and protein sources in feed.

According to the Canola Council of Canada, worldwide demand for food oil has led to record canola production (18 million metric tonnes for 2013) in Canada. With increased production of any crop, there is the inevitable increase in the availability of product that does not meet quality standards for human consumption. Green canola seeds, which do not properly mature prior to harvest, whether due to late seeding or early frost, are rejected at canola crushing plants because the chlorophyll stains the oil, making it unappealing to consumers. This rejected product becomes a potential feed ingredient as full-fat green canola seed (FFGC).

With more than 35 per cent oil and 20 per cent crude protein, FFGC can be a good source of energy and amino acids in partial replacement of conventional ingredients in swine diets. Unfortunately, there is a lack of information on the nutritional value of FFGC for pigs. It is common knowledge that canola seed is relatively high in fibre and glucosinolates, which may compromise nutrient utilization and feed intake. In addition, the oil in FFGC is mostly unsaturated, which may impact pork quality.

In order to make optimal use of FFGC in pig diets, it is important to establish a comprehensive nutrient profile and determine its effects on pig performance and carcass traits. Researchers at the University of Alberta recently conducted two experiments to address this lack of knowledge of FFGC, in order to calculate net energy value and determine standardized ileal digestible (SID) coefficients of amino acids in FFGC fed to pigs; and to determine the effects of including 0, 5, 10 or 15 per cent FFGC, or decreasing amounts by growth phase, in grower-finisher diets on growth performance and carcass traits.

In the first experiment, six ileal-cannulated barrows (starting at 46.5 kilograms body weight) were fed three diets – a basal diet containing wheat, a FFGC diet in which FFGC replaced 40 per cent of the wheat, and a cornstarch-based N-free diet – in a replicated three-by-three Latin square design.

In the second experiment, 1,100 pigs (starting at 32.9 kilograms body weight), housed in 50 pens of 22 barrows or gilts per pen, were fed five diets including 0, 5, 10 and 15 per cent constant or declining amounts (15, 10, 5, and 0 per cent, respectively) of FFGC over five phases. In order to maintain diet net energy value and SID amino acid content within each phase, the increasing inclusion rate of FFGS was accommodated by reducing tallow and soybean meal, exchanging wheat for barley and making a final correction using synthetic amino acids.

In experiment 1, the researchers observed that FFGC were 60 per cent distinctly green. Of note, the data analysis showed that on a dry matter basis, FFGC contained 43 per cent ether extract, 25 per cent crude protein, 9.97 µmol/g glucosinolates, and 1.35 per cent lysine, 94 per cent of which was chemically-available (see Table 1). In FFGC, the SID coefficient of lysine was 86.9 and calculated digestible and net energy values were 4.92 and 3.50 Mcal/kg of dry matter, respectively.

The ether extract level reported in this study was lower than anything previously reported for regular canola seed (reports have ranged from 44.1 to 50.4 per cent). During maturation of canola, oil is deposited later in the seeds than other nutrients, implying that mature canola seeds contain more oil than green seeds. In contrast, the amino acid profile described for FFGC is similar to previously reported values for regular canola seed. Therefore, maturation of canola seed from green to brown colour may not affect the amino acid profile of the seed as much as the oil content.

The total glucosinolate content of FFGC (9.97 µmol/g) in the present study was lower than that reported in regular, mature canola seed (13.83 µmol/g), but greater than heated canola seed (3.33 µmol/g). This corresponds to previous research establishing that glucosinolate content in canola seed increases with maturity while heating or toasting of the meal reduces glucosinolate content, thereby making canola suitable as a feed ingredient in pig rations. The diet containing 15 per cent FFGC had a calculated total glucosinolate content of 1.5 µmol/g, well below the generally accepted tolerance level of 2.0 µmol/g.

In experiment 2, increasing dietary FFGC inclusion from 0 to 15 per cent resulted in significantly decreased gain:feed ratio, carcass weight and dressing percentage and also tended to decrease average daily gain (see Table 2). Pigs fed decreasing amounts of FFGC by growth phase compared with controls (0 per cent FFGC) had a significantly lower overall gain:feed ratio. However, increasing dietary FFGC inclusion did not have a significant effect on other carcass traits, such as backfat thickness and loin depth.

In this study, the researchers took great pains to ensure that the diets were formulated to be similar in net energy and standardized digestible amino acid content. Therefore, the observed decrease in growth performance and carcass weight with increasing dietary FFGC inclusion was probably not caused by a decrease in dietary nutrient availability. It could, however, have been due to an increase in dietary fibre with increased dietary inclusion of FFGC, since both FFGC and barley have higher fibre content than the wheat, soybean meal, and fat they replaced in the control diet.

Due to its bulk, dietary fibre reduces nutrient digestibility and results in higher visceral gut weight and gut fill. Since the majority of the maintenance energy requirement of an animal is used to support its visceral organs, it is safe to assume that the bigger these organs are, the greater the energy expenditure. If this energy is used for maintenance, it is not available for growth, leading to reduced growth performance as was evidenced in this study. This higher fibre content also had an impact on gain:feed ratio, carcass weight and carcass dressing percentage.

Feeding increasing levels of dietary FFGC did not, however, have a significant effect on other carcass traits such as backfat thickness and loin depth. This suggests that FFGC can be included in diets of growing-finishing pigs without affecting these same carcass traits, regardless of whether FFGC is fed only in the grower phase or in both grower and finisher phases.

Based on the results of the experiments, the researchers concluded that FFGC is a good source of dietary amino acids and energy for pigs. However, increasing dietary FFGC inclusion by decreasing dietary inclusion of wheat, soybean meal, and tallow, and increasing dietary inclusion of barley to maintain dietary NE value did have a negative impact on gain:feed ratio, carcass weight, and dressing percent of pigs, likely due to the higher dietary fibre content.

Therefore, the ultimate level of FFGC used in swine diets should be based on targeted feed efficiency and the relative cost to other available feed ingredients. BP

Janice Murphy is a former Ontario agriculture ministry swine nutritionist who now lives and works in Prince Edward Island.

Source: T. A. Woyengo, J. Yánez, M. G. Young, G. Lanz, E. Beltranena and R. T. Zijlstra. 2014. Nutritional value of full-fat green canola seed fed to growing-finishing pigs. J ANIM SCI 92:3449-3459.