Performance and Docosahexaenoic Acid (DHA) Content in Longissimis dorsi and Backfat Tissues of Grow-Finish Pigs Fed Diets Differing in Heterotrophically-Grown Algae Content

Algae sources high in DHA provided in diets fed pigs can potentially produce a more nutritionally desirable pork product for consumers. The objective of this study was evaluation of performance and DHA content of <em>Longissimus dorsi</em> (LD) and backfat of grow-finish pigs fed diets containing 0, 0.25 or 0.50% unextracted <em>Aurantiochytrium limacinum</em> CCAP 4087/2 algae (FORPLUS^TM, Alltech Inc). Diets were formulated not to exceed maximums permitted in Europe and contained no antibiotic growth promoters. The study involved 144 pigs (72 gilts and 72 barrows) of 27.9 ± 2.5 kg initial weight. The trial lasted 121 days (112 d and 9 d to slaughter of all pigs). Pigs remained on assigned test diets during the 9d between final weight measurement and slaughter. The study was divided into two growing periods (0-56 and 56-112 days, respectively) for calculation of average daily gain (ADG) and efficiency (feed:gain) on all animals. At trial end carcass characteristics from 72 animals were evaluated . Carcasses from only half the animals were evaluated owing to logistic and economic practicalities. The animals were selected based on live weight near treatment means within gender. DHA content of LD and backfat were sampled from each right side carcass at the 13^th rib. Data were subjected to ANOVA with means separated using student’s t-test and Tukey test. ADG, feed:gain, feed, and water intake were unaffected by dietary treatment (P&lt;>0.05). Carcass lean content revealed a treatment x gender interaction(P&lt;<0.05): gilt backfat tended to increase with algae level with a trend toward lower LD thickness while the opposite was true for barrows. DHA content of LD differed with gender (P&lt;<0.05), though differences are only apparent in higher values for barrows given 0.5% algae. In gilts, loin DHA content increased with dietary algae (3.3X control values at 0.25% algae, and 4.5X control values at 0.5% (0.0054, 0.0178, and 0.243 g/100 g tissue, respectively, P&lt;0.0001). Corresponding values in barrows at 0, 0.25 and 0.5% dietary algae were 0.0059, 0.0178, 0.0297 g DHA/100 g tissue. Backfat DHA increased in response to algae level P&lt;<0.05. Values were 0.047, 0.187, and 0.307 g/100 g fat for pigs given 0, 0.25, and 0.5% algae, respectively. It was concluded that DHA content of LD and backfat in pigs fed throughout the grow-finish period increased with dietary algae content. DHA increases in LD of 3.3X and 4.5X allow dosage to be calculated to meet target DHA values.