Intramuscular fat and melting point variation in sheep supplemented with Spirulina

Spirulina (Arthrospira platensis) is a highly nutritious and edible microalga, but knowledge about the productive response of sheep to Spirulina supplementation is scanty and its impact on intramuscular fat deposition in lambs largely unknown. We tested the hypothesis that Spirulina lowers intramuscular fat levels and improves meat tenderness at low levels of supplementation without detrimental effects on eating quality. Therefore, the objective of this study was to investigate the influence of varying levels of Spirulina supplementation on Longissimus dorsi intramuscular fat (IMF) content and fat melting point (FMP) in crossbred sheep. Twenty four prime lambs sired by Dorset, White Suffolk, Black Suffolk and Merino rams were weaned at six months of age and subjected to a nine-week feeding trial at 3 levels of Spirulina supplementation: Control group (0%), low (10%wt/vol) and high (20%wt/vol) levels. Each treatment group had a random allocation of 8 lambs balanced by gender (ewes and wethers), body condition score (average of 3.1¡¾0.4) and body weight (average of 37.6¡¾5.2 kg). Lambs in the low and high supplementation groups were drenched daily with Spirulina prior to being released for grazing with the control group. Lambs were slaughtered in a commercial abattoir and Longissimus dorsi muscle samples taken for laboratory determination of IMF and FMP. Intramuscular fat and melting point data were subjected to statistical analyses utilising general linear model procedures in SAS with sire breed, sex, Spirulina level of supplementation and their second-order interactions fitted as fixed effects and sire as a random variable. It was evident that the higher the level of Spirulina supplementation, the lower the fat content in which IMF significantly (p<0.05) dropped from 2.1¡¾0.3% in the control group, to 1.6¡¾0.2% and 1.4¡¾0.1% in the low and high supplementation groups, respectively. FMP values were similar between the control (44.0¡¾0.6¢ªC) and high (44.2¡¾0.2¢ªC) supplementation groups, but significantly lower (p<0.01) in the low (42.9¡¾0.7¢ªC) treatment group. These results suggest that Spirulina supplementation at a 10% inclusion level has the potential to produce leaner, healthier meats containing more monounsaturated and long-chain polyunsaturated fatty acids with low fat melting points, with relatively little impact on overall eating quality when compared to meat from lambs at either 0% or 20% supplementation levels.