The effects of increasing dietary level of glucosinolates through dietary inclusion of canola co-products on growth performance, voluntary feed intake of pigs have been evaluated in several studies. An increase in dietary level of glucosinolates from 0 to 0.56, 0.77, 1.13, 1.28, 1.74, 2.17, 2.22 or 2.60 àmol/g through dietary inclusion of Napus canola co-products did not affect BW gain and voluntary feed intake of pigs (Table 2.4). However, increasing the level of total glucosinolates from 0 to 2.78 àmol/g in diets through dietary inclusion of Napus canola co-products reduced BW gain and voluntary feed intake of pigs.
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Table 2.4 Effects of including canola co-products in diets for pigs on body weight gain and feed intake
aSECM=Solvent-extracted canola meal; EPCM= Expeller-pressed canola meal; CPCC= Cold-pressed canola cake.
bPositive values indicate that increase in the dietary level of canola coproducts resulted in increased body weight gain or feed intake of pigs.
Negative values indicate that increase in the dietary level of canola coproducts resulted in decreased body weight gain or feed intake of pigs.
cSignificant changes in body weight gain or feed intake of pigs due to an increase in the dietary level of glucosinolates due to inclusion of canola coproducts in diets.
Co-producta Species Animal
Dietary inclusion level
Change in performanceb, g/d
Canola co- products,
g/kg
Glucosinolates (in diets),
àmol/g BW gain
Feed
intake References
SECM Napus Nursery 150 0.56 -31 -24 Seneviratne et al. (2011a)
SECM Napus Nursery 200 0.77 -23 +5 Landero et al. (2011)
SECM Napus Grower-
finisher 250 1.13 +77 +35 King et al. (2001)
SECM Napus Nursery 150 1.28 +1 +13 Sanjayan et al. (2014)
SECM Juncea Nursery 150 2.27 +2 +9 Sanjayan et al. (2014)
SECM Juncea Nursery 240 2.60 -57c -84c Landero et al. (2013)
SECM Napus Nursery 300 2.60 +20 -60 Parr et al. (2015)
EPCM Napus Nursery 150 1.74 -39 -24 Seneviratne et al. (2011a)
EPCM Napus Grower-
finisher 75 1.74 -15 -44 Seneviratne et al. (2010)
EPCM Napus Nursery 200 2.17 +1 -13 Landero et al. (2012)
EPCM Napus Grower 300 2.78 -50c -163c Sands et al. (2013)
EPCM Napus Grower 300 2.78 -60c -160c Velayudhan et al. (2017)
CPCC Napus Nursery 200 2.22 +12 -12 Zhou et al. (2016)
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With regard to Juncea canola co-products, an increase in dietary level of
glucosinolates from 0 to 2.60 àmol/g through dietary inclusion of Juncea SECM reduced BW gain and voluntary feed intake of pigs. The effects of adding purified glucosinolates in diets for animals on growth performance have also been
investigated. Bille et al. (1983) reported a 22 and 23% reduction in body weight gain and feed intake of growing rats, respectively, due to the consumption of a diet with purified progoitrin at 5 mg/g for 5 d. Similarly, Bjerg et al. (1989) observed a 7 and 6% reduction in weight gain and feed intake of rats, respectively, in 10 d due to an increase in the level of total glucosinolates from 0 to 12.5 àmol/g through dietary inclusion of pure progoitrin. However, Vermorel et al. (1986) reported unaffected growth performance of growing rats during 29 d due to addition of pure
glucobrassicin to the diet at 0.5 g/kg, which is be attributed to the fact that
glucobrassicin, which is an aromatic glucosinolate, is less toxic than progoitrin, which is an aliphatic glucosinolate.
From these studies, it is apparent that glucosinolates reduce growth
performance of animals, and that an increase in the amount of glucosinolates in diets for pigs to the level above 2.60 àmol/g through dietary inclusion of Napus canola co- products negatively affects BW gain and feed intake. However, the tolerance level of glucosinolates derived from Juncea SECM is less than that derived from Napus SECM by pigs, which can be partly explained by the greater content of aliphatic glucosinolates in Juncea SECM than in Napus SECM. Thus, further research is warranted to determine the optimal level of Juncea canola-derived glucosinolates in diets for pigs without reducing growth performance.
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Results from previous studies on the effects of increasing amounts of glucosinolates in diets for pigs through dietary inclusion of canola co-products on organ weights and thyroid hormones are presented in Table 2.5. Increasing the level of total glucosinolates from 0 to 3.10 àmol/g in diets through dietary inclusion of Napus canola co-products did not affect liver weight relative to live BW. However, Napus canola-derived glucosinolates increased thyroid gland weight relative to live BW when dietary level of glucosinolates was increased from 0 to 2.10 àmol/g, implying that dietary level of glucosinolates that is required to increase metabolic activities of thyroid glands is less than that is required to adversely affect liver function in pigs. In addition to the enlargement of these organs, thyroid functions (synthesis of serum T3 and T4) were also negatively affected by dietary concentration of glucosinolates that is equal or greater than 2.78 àmol/g. Results from previous studies on the effects of including purified glucosinolates on organ weights have been reported. Bille et al. (1983) reported a 6, 20, and 110% increase in liver, kidneys, and thyroid gland weights of growing rats, respectively, due to the of diets with purified progoitrin at 5 mg/g for 5 d. Also, Bjerg et al. (1989) reported a 4% increase in liver weight of rats during a 10-day feeding period due to an increase in the level of total glucosinolates from 0 to 12.5 àmol/g through dietary inclusion of purified progoitrin.
Vermorel et al. (1986) similarly reported a 17, 9 and 34% increase in liver, kidneys, and thyroid gland weights of growing rats, respectively, during a 29-day feeding period due to the addition of purified progoitrin to the diet at 3 g/kg. However, in the same study, the addition of pure glucobrassicin to the diet at 0.5 g/kg did not affect organ weights of growing rats, likely because glucobrassicin is less toxic than progoitrin.
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Table 2.5 Effects of including canola co-products in diets for pigs on organ weights and thyroid hormone concentrations
aSECM = Solvent-extracted canola meal; EPCM= Expeller-pressed canola meal; CPCC= Cold-pressed canola cake.
bPositive values indicate that an increase in the dietary level of canola coproducts resulted in increased organ weights and thyroid hormone levels of pigs. Negative values indicate that an increase in the dietary level of canola coproducts resulted in decreased organ weights and thyroid hormone levels of pigs.
cSECM = Conventional solvent-extracted canola meal.
dSECM = High-protein solvent-extracted canola meal.
eSignificant changes in organ weights and thyroid hormone levels of pigs due to an increase in the dietary level of glucosinolates due to inclusion of canola coproducts in diets.
Co-producta Animal
Dietary inclusion level
Changes in organ weights and thyroid hormone levelsb
Canola co- products,
g/kg
Glucosinolates (in diets),
àmol/g
Thyroid gland
weght, g Liver,
% of BW T3,
ng/mL T4,
ng/mL References
SECM Grower-
finisher 300 1.35 -0.4 - - - King et al. (2001)
SECMc Nursery 300 2.60 +2.3e +0.01 -0.17 -2.0 Parr et al. (2015)
SECMd Nursery 200 3.10 +1.0e +0.06 -0.31e -4.3e Parr et al. (2015)
EPCM Grower 300 2.78 +0.1e -0.9 +0.2e +11.7e Velayudhan et al. (2017)
EPCM Grower 200 2.10 +0.4e - - - Mullan et al. (2000)
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This increase in liver, kidney, and thyroid gland weights of pigs fed canola coproducts-containing diets can be explained by the adverse effects of certain glucosinolates in the canola co-products on these organs. From the pig studies, it appears that dietary level of canola-derived glucosinolates that is less than 2.10 àmol/g does not reduce liver and thyroid gland weights relative to live BW; thyroid hormone levels in serum.
An increase in visceral organ weight is positively associated with an increase in metabolic activity in the same organ (Ferrell, 1988). An increase in metabolic activities in visceral organs results in increased energy expenditure by these organs at the expense of skeletal tissue deposition (Nyachoti et al., 2000). Thus, the increase in organ weights of pigs due to dietary inclusion of Napus canola co-products indicates increased utilization of dietary energy for the maintenance of these organs.
Additionally, thyroid hormones are involved in the regulation of energy metabolism with the body, implying that the reduction in thyroid hormone synthesis negatively affects the growth and development of animals (Fisher et al., 1982; Hulbert, 2000).
Thus, the increased organ weights and reduced thyroid hormone levels due to
increasing dietary levels of canola co-products-derived glucosinolates can result in a reduction in the growth and development of pigs. The effects of glucosinolates on metabolism in liver, kidneys and thyroid glands vary depending on the composition of glucosinolate degradation products as discussed below.