Effect of milking frequency and alpha-tocopherol plus selenium supplementation on sheep milk lipid composition and oxidative stability

Authors: PULIDO, E - University Of Leon; FERNANDEZ, M - University Of Leon; PRIETO, N - University Of Alberta; Baldwin, Ransom - Randy; ANDRES, S - University Of Leon; LOPEZ, S - University Of Leon; GIRALDEZ, F - University Of Leon

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2018
Publication Date: 2/14/2019
Citation: Pulido, E., Fernandez, M., Prieto, N., Baldwin, R.L., Andres, S., Lopez, S., Giraldez, F.J. 2019. Effect of milking frequency and alpha-tocopherol plus selenium supplementation on sheep milk lipid composition and oxidative stability. Journal of Dairy Science. 102(4):3097-3109. https://doi.org/10.3168/jds.2018-15456.
DOI: https://doi.org/10.3168/jds.2018-15456

Interpretive Summary: The aim of this research was to study the effect of milking frequency and vitamin E plus Selenium (an important mineral in stress responses) supplementation on fatty acids in sheep milk. Sixteen milk sheep (Assaf Spanish breed) ewes were used, eight did not receive any vitamin-mineral supplement (Control), and the other eight received an oral dose of 1,000 IU of vitamin E and 0.4 mg of selenium daily. An additional experiment sought to test if milking only 1 time daily compared to two times daily would affect milk fatty acid content. The circulating concentration of Vit E. in blood plasma and milk were increased in ewes given the supplement, indicating a greater ability to respond to an immunological stressor, such as infection. In comparison with twice a day minking, Once a day milking increased the proportions of linoleic acid and several forms of fatty acids in milk with 18 carbons and reduced amount of a-linoleic acid and some polyunsaturated fatty acids with 20 and 22 carbons. Both milking frequency and the combined supplementation of vitamin E and Se modified milk FA profile which is important to the quality of liquid milk for the dairy industry. Milking frequency did not affect milk oxidative stability but antioxidant supplementation improved the oxidant status of dairy ewes and milk antioxidant capacity.

Technical Abstract: The aim of this research was to study the effect of milking frequency (one (ODM) vs two (TDM) milkings daily) and vitamin E plus Se supplementation on fatty acid profile and oxidative stability in sheep milk. Sixteen Assaf ewes were used, eight did not receive any vitamin-mineral supplement (Control), and the other eight received an oral dose of 1,000 IU of vitamin E and 0.4 mg of selenium daily. The experiment consisted of two consecutive periods, the first was three weeks and consisted of TDM of both mammary glands. The second period was eight weeks and consisted of ODM of one mammary gland and TDM of the other gland. All ewes were fed ad libitum the same total mixed ration from lambing and throughout the experiment. There were not differences (P>0.05) in plasma or milk Se concentrations between control and supplemented ewes. However, plasma and milk vitamin E concentrations and antioxidant capacity were increased (P<0.01) in ewes receiving the antioxidant supplement. Milk fatty acid profile was practically unaffected after 21 days of antioxidant supplementation. However, after 77 days antioxidant supplementation increased (P<0.05) the relative percentage of C16:0 and cis-9 C18:1 and reduced the proportions of some saturated FA with less than 16 C and of cis-9 C12:1. Antioxidant supplementation had no effect on the proportions of conjugated linoleic acid or of total polyunsaturated FA, but decreased (P<0.05) the proportion of trans_7 cis_9 C18:2, and increased that of n-6 C20:3. Milking frequency did not affect (P>0.05) vitamin E or Se concentrations, resistance to oxidation or total proportion of saturated FA in milk. Total monounsaturated FA, cis-9 C16:1 and several cis- and trans-isomers of C18:1 were increased in milk from ODM glands. The total proportion of polyunsaturated FA was not significantly (P>0.05) affected by milking frequency. In comparison with TDM, ODM increased (P<0.05) the proportions of linoleic acid and several isomers of C18:2 and reduced those of a-linoleic acid and some polyunsaturated FA acids of 20 and 22 C. Both milking frequency and the combined supplementation of vitamin E and Se modified milk FA profile. Milking frequency did not affect milk oxidative stability but antioxidant supplementation improved the oxidant status of dairy ewes and milk antioxidant capacity.