Maria Villagrasa
Flax is one of the oldest crops in the world. Much of its interest lies in the type of fiber it produces and the high oil content of its seed, rich in polyunsaturated fatty acids (FA), in particular, alpha-linolenic acid (51%).
Linolenic (C18:3) and linoleic (C18:2) acids are essential for humans and must be obtained from food fats and oils because the body cannot synthesize them. Likewise, both FA play a critical role in the productive performance and immunity of ruminants. In general, omega-6 FA function as pro-inflammatory precursors whereas omega-3 FA are substrates for the synthesis of resolvins and proteins that reduce inflammation.
The objective of a recent study (Melendez et al., 2020) was to compare the effects of flaxseed and canola expellers on the average daily gain (ADG) of Holstein calves from birth to weaning. The experiment was based on the hypothesis that flax expeller would have a better effect on health and immunity of calves than canola since the flax seed is richer in n-3 FA.
Key molecules were also selected as indicators of an acute inflammatory process (haptoglobin), inflammation in response to an infection [interleukin IL-1], and restoration of cellular function after an inflammation process (resolvin-E1).
The nutrient composition (DM) of cnaola and flax expellers was, respectively: crude protein 32.2 vs 32; fat: 10.9 vs 9.8%; neutral detergent fiber 25. 5 vs. 31. 4%; acid detergent fiber: 20. 2 vs. 18. 3% and starch 8.5 vs. 8.9%. The FA concentration (% total FA) was linoleic 31. 1 vs. 14.1% and Linolenic 7. 6 vs. 55. 9%.
A total of 40 calves were randomly assigned to two groups:
- Flax: starter feed with flax expeller (25% DM basis).
- Canola: starter feed with canola expeller (25% DM basis).
In addition to these protein concentrates, other components of the feed were corn grain (46.1% DM), soybean meal (20.2% DM), wheat bran (7.0% DM) and a vitamin-mineral premix (1.5% DM). Both starter feeds were iso-nitrogenous and iso-caloric but differed in their n-3 and n-6 FA contents. The nutritional composition (DM) of canola and flax starter feed was, respectively: crude protein 24.1 vs. 24.5%; fat 4.7 vs 4.6%; neutral detergent fiber 16.9 vs. 17.3% and starch 36.0 vs. 37.6%. The concentration of FA (% total FA) was linoleic 46.6 vs. 41.6 and linolenic 4.9 vs 20.8.
Average weight gains were similar with flaxseed and canola expeller
The incorporation of flax in the starter feed did not affect DM intake (0.50 kg/day), body weight at weaning (79.3 kg) and ADG between birth and 60 days of age (ADG 0-30 days, 30-60 days, and 0-60 days were 0.54 kg/day, 0.81 kg/day, and 0.68 kg/day). In addition, the incidence of diarrhea was higher in calves fed flax (45 vs. 25%), and all cases occurred during the first 10 days of life.
Haptoglobin concentrations on day 7, interleukin-1 (IL-1) on day 21, and resolvin-E1 on days 14 and 49 were higher in the flax than in the canola group. The increase in resolvin-E1 concentrations could be explained by the highest concentrations of n-3 FA in the calves receiving flax, which also had the greatest incidence of diarrhea.
As already indicated above, n-3 FA act as anti-inflammatory precursors, so the higher concentration of resolvin-E1 in the flax group on day 49 suggests these calves had a better immune response to the inflammatory process suffered during the study.
In conclusion, flax expeller flour can replace traditional protein concentrates such as canola meal in calf diets. In addition, its high concentration in n-3 FA may improve the immune response in growing heifers.
Reference
Pedro Melendez, Romina Ramirez, María P. Marin, Mario Duchens, Pablo Pinedo. Comparison between linseed expeller and canola expeller on concentrate intake and circulating inflammatory mediators in Holstein calves. Animal Nutrition 6 (2020) 47-53.
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