Submitted to: Small Ruminant Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/25/2008
Publication Date: 9/11/2008
Publication URL: doi:1010/j.smallrumres.2008.07.024
Citation: Lewis, G.S., Wulster-Radcliffe, M.C., Herbein, J.H. 2008. Fatty acid profiles, growth, and immune responses of neonatal lambs fed milk replacer and supplemented with fish oil or safflower oil. Small Ruminant Research. 79:167-173. Interpretive Summary: Diets that have been supplemented with long-chain, n-3 (e.g., marine fish oil) polyunsaturated fatty acids (PUFA) have improved the health and performance of neonatal and growing animals, although responses to n-3 PUFA supplementation have not always been consistent. In the western United States, where sheep are raised on rugged and remote rangelands, litters are commonly reduced to two lambs. This practice is called “orphaning.” At the U.S. Sheep Experiment Station, approximately 10% of the lambs born annually are orphaned. Orphaned lambs are typically fed milk replacer until they can be transitioned to solid feed. Morbidity and mortality of orphaned lambs seems to be greater than that of lambs raised with their dams, but the true health status and survival of orphaned lambs is not known. Nevertheless, interventions that would improve the health and survival rates of orphaned lambs are needed. Even though the scientific literature contains numerous examples of the potential benefits of fish oil treatment on neonatal health and performance, the lack of consistency in results makes it difficult to determine whether fish oil supplementation is actually beneficial. Because of the reported effects of fish oil on immune functions in young animals, we conducted a study to determine whether supplementing orphaned milk replacer-fed lambs with fish oil, which is rich in long-chain n-3 PUFA, would alter plasma lipid profiles and affect immune functions and growth characteristics. Fish oil supplementation increased plasma total n-3 fatty acid concentration and increased the n-3:n-6 fatty acid ratio, but it did not seem to improve any measure of lamb growth performance or immune function. Thus, fish oil supplementation does not seem to benefit healthy milk replacer-fed lambs.
Technical Abstract: Diets supplemented with long-chain, n-3 (e.g., marine fish oil) polyunsaturated fatty acids (PUFA) have improved the health and performance of neonatal and growing animals. This study was conducted with lambs that were orphaned at approximately 1 day of age to determine whether supplementing milk replacer-fed lambs with oils rich in long-chain n-3 (i.e., fish oil) or n-6 (i.e., safflower oil) PUFA would alter plasma lipid profiles and affect immune functions and growth characteristics. From day 1 to 28 of age, lambs had ad libitum access to a commercial milk replacer, via three-nippled buckets. From day 7 to 28 of age, lambs received twice daily either 1 g of either soybean oil (control), 1 g of fish oil, or 1 g of safflower oil per os in a gelatin capsule (n = 60 pens; 20 pens/treatment; one ewe and one ram with similar initial body weights/pen). On day 7, 14, 21, and 28 of age, all lambs were weighed, and jugular blood samples were collected from ram lambs. Lymphocyte proliferation in vitro, differential white blood cell (WBC) counts, and weight gains were quantified. Plasma collected on day 7 and 28 were used for fatty acid analyses. Data were analyzed with mixed models procedures. Fish oil increased (P < 0.001) plasma total n-3 fatty acid concentration and n-3:n-6 fatty acid ratio. Pen body weight (i.e., total lamb weight per pen) increased (P < 0.001) with day (day 7, 11.9 kg; day 14, 15.1 kg; day 21, 18.2 kg; and day 28, 21.2 kg), but not with oil treatment. Neither oil treatment, day, nor the oil treatment × day interaction were significant for pen body weight gains (3.5 kg), pen average daily gains (0.5 kg), pen milk intakes (19.0 kg), or pen gain:feed ratio (0.18) measured during three intervals: day 7 to 14; day 14 to 21; and day 21 to 28). Day, but not oil treatment, affected (P < 0.001) unstimulated, Con A-stimulated, and LPS-stimulated lymphocyte proliferation: day 14, 21, and 28 proliferation > day 7 proliferation. For neutrophils per 100 WBC, the treatment × day interaction was significant (P < 0.05). Oil treatment and day affected (P < 0.01 and P < 0.05, respectively) lymphocyte numbers per 100 WBC. For monocytes, eosinophils, and basophils, neither oil treatment, day, nor the oil treatment × day interaction were significant. Fish oil altered plasma fatty acid profiles, but it did not seem to improve any measure of lamb performance or immune function.