Effect of Protected Saturated or Polyunsaturated Fat Fed to Pregnant and Lactating Ewes on Milk Composition, Lamb Plasma Fatty Acids and Growth

Seventy-two pregnant ewes were allotted to three ration treatment groups: 1) Control: corn silage and alfalfa pellets; 2) Tallow: corn silage, alfalfa pellets and protected tallow; 3) Polyunsaturated (P/S): corn silage and protected soybean and sunflower seeds. Diet influenced plasma glucose and linoleic acid content of esterified, but not of non-esterified, fatty acids in ewe plasma. Proportions (weight %) of short chain (6:0 to 14:0) fatty acids in milk fat were reduced by both tallow and P/S diets; P/S increased milk fat linoleic acid fivefold, and milk fat percent by 50%. At birth, body weights and linoleic acid in plasma phospholipids of lambs in all treatment groups were identical. Plasma phospholipid triene/tetraene ratio of all groups indicated essential fatty acid deficiency at birth and this was reversed by 1 day of age. At 10 days of age, lambs nursing P/S ewes had plasma phospholipid linoleic acid contents 90% greater than the tallow group. At 28 days of age, weight gain of P/S lambs was 89% of the tallow group, and 66% of controls. We suggest that polyunsaturated milk without supplemental tocopherol may be toxic to young ruminants.