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The intake of linoleic acid (LA) and alpha-linolenic acid (ALA) in relation to average daily weight gain (ADG) was studied in growing-finishing pigs kept on smallholdings in Central Vietnam. Groups of three piglets each were assigned randomly to 12 farms, where they were fed on local feedstuffs according to the farmer's choice but were given a restricted amount of dry matter according to a preset feeding regimen. On arrival at the farms, the pigs weighed 10.4 +/- 0.9 kg (mean +/- SD, n = 36) and at 130 days of age they weighed 45.4 +/- 9.6 kg. Dietary LA concentration ranged from 1.34 to 2.41 g/MJ metabolizable energy (ME) and ALA from 0.06 to 0.33 g/MJ ME. On a farm level, dietary LA and ALA concentrations were significantly correlated with their concentrations in adipose tissue, both correlation coefficients being 0.63. Dietary protein concentration and protein:energy ratio were significantly correlated with ADG, the correlation coefficients being 0.68 and 0.64. For individual piglets there were significant correlations between either LA or ALA in adipose tissue and ADG, the correlation coefficients being 0.37 and 0.45. Dietary protein concentration or protein:energy ratio was correlated with the dietary contents of LA and ALA. It is uncertain whether LA and ALA intake had a causal relationship with ADG. Since dietary LA levels were above the LA requirement, LA intake may not have limited growth. It is suggested tentatively that, through enhanced disease resistance, supplementation with ALA of the diets on the farms studied might have a positive influence on ADG.

The aim of the study was to investigate the effect on growth performance of the addition of 5% of either linseed, fish or coconut oil to the diet of growing pigs kept on small holdings in central Vietnam. The diets were fed on six different farms; there were three animals per treatment per farm. The farmers fed a base diet according to personal choice, but were instructed to use linseed, fish and coconut oil. The diets were fed to the pigs from 70 to 130 days of age. The diets with 5% linseed oil on average contained 2.4 g alpha-linolenic acid/MJ of metabolizable energy (ME) and the diets with 5% fish oil on average contained 0.06 and 0.75 g eicosapentaenoic and docosahexaenoic acid/MJ ME, respectively. The relative percentages of docosahexaenoic, eicosapentaenoic, alpha-linolenic and linoleic acid in adipose tissue were determined by the intake of the corresponding fatty acids. Dietary linseed oil vs. coconut oil significantly enhanced daily weight gain and vs. fish oil it also stimulated growth, but this effect just failed to reach statistical significance. It is concluded that extra intake of alpha-linolenic acid may stimulate growth in growing-finishing pigs, this effect being independent of the conversion of alpha-linolenic acid into eicosapentaenoic and docosahexaenoic acid., (Copyright 2004 Blackwell Verlag, Berlin)