PSIV-16 Association between gastrointestinal nematodes and milk fatty acid profile in Katahdin lactating ewes.

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Abstract The effects of gastrointestinal nematodes (GIN) in lactating ewes have been studied throughout the sheep dairy industry. Not much is known about the impacts of GIN in the milk of meat sheep. Gastrointestinal nematodes sequester nutrients from the GI tract of the ewe, leading to changes in milk components. Milk Fatty acids (FAs) are taken by the udder from blood circulation or are newly synthesized in the mammary tissue. Essential fatty acids (EFAs) can only be obtained from the diet and are important for lamb development. The objective of this study was to investigate the relationship between fecal egg count (FEC), as a representation of the GIN load and milk fat percentage and fatty acid profile in lactating ewes. Twenty-four primiparous Katahdin ewes were selected. Milk, feces, and blood were collected seven days post parturition. The body weight (BW) and body conditioning scores (BCS) were recorded. Blood serum was used to measure levels of β-hydroxybutyric acid. Feces were used for FEC. Milk fat percentage was measured by crematocrit analysis. Finally, a fatty acid extraction was performed using Folch extraction and the FAs were analyzed using FAME gas chromatography. The cause-effect relationship between the FEC to the fatty acid profiles and milk fat percentage was evaluated by using the Theil-Sen Siegel regression analysis. Ewes were divided between high and low GIN loads based on the FEC median (1950 eggs/g of feces) for the correlation analysis. Spearman’s correlation coefficient (ρ) was used to perform the correlation. Statistical significance was considered at p < 0.05, and coefficients ρ > 0.70 were deemed strong and biologically relevant. The regression analysis found that FEC was negatively associated (p < 0.05) with BW, caprylic (C8:0), capric (C10:0), lauric (C12:0), myristic (C14:0), palmitic (C16:0) and linoleic (C18:2) acids. In the high FEC animals, FEC was negatively correlated to capric (ρ = -0.629) and lauric acids (ρ = -0.650). In low FEC animals, FEC was negatively correlated to total fat percentage (ρ = -0.729). Linoleic acid and BW were also negatively correlated to FEC. In both groups, short and medium chain FAs (C8 – C16) were positively correlated (ρ > 0.6) and long chain FAs (>C18) were positively correlated (ρ > 0.6) between them. These results suggest that ewes with a higher GIN load have milk containing less de novo FAs, linoleic acid, and EFAs, supporting the idea that GIN infections have repercussions on the milk nutritional quality, which can lead to poor lamb development.