Lactation performance and milk fatty acid composition of lactating dairy cows fed Camelina sativa seeds or expeller

Abstract The objective of the current study was to compare the effects of feeding corn dried distillers’ grains with solubles (DDGS), camelina expeller (CE), whole camelina seeds (WCS), or whole flax seeds (WFS) on milk yield and composition of lactating dairy cows. Four Holstein cows were used in a 4 × 4 Latin square design with 21-d periods, including 14 d of adaptation followed by 7 d of sampling. Four isoproteic and isolipidic dietary treatments were formulated as follows: 1) 18% DDGS; 2) 9.5% CE; 3) 4.2% WCS; and 4) 4.7% WFS (dry matter basis). Pre-planned contrasts were established to compare: 1) the two by-products (DDGS rich in cis-9, cis-12 18:2 vs. CE rich in cis-9, cis-12, cis-15 18:3); 2) the two forms of camelina (CE vs. WCS); and 3) the two whole seeds (WCS vs. WFS). Differences were declared at P ≤ 0.05. Contrasts did not reveal any significant differences in dry matter intake ( x ¯ =24.6 kg/d). Actual milk yield was greater for cows fed WCS (36.5 kg/d) compared with WFS (35.6 kg/d). Moreover, yield of fat-corrected milk was lower with CE (29.8 kg/d) than with DDGS (35.3 kg/d) or WCS (33.5 kg/d). These effects are in line with lower milk fat concentration when cows received CE (27.1 g/kg) as compared with DDGS (36.3 g/kg) or WCS (34.8 g/kg). Lower milk fat observed with CE could be explained by a shift from the trans-11 to the trans-10 pathway of biohydrogenation, leading to the production of more intermediates known to inhibit milk fat synthesis, i.e., milk fat concentration of trans-10, cis-12 18:2 was greater with CE (0.078 mg/g) than with DDGS (0.045 mg/g) or WCS (0.041 mg/g). The transfer efficiency, from the diet to milk fat (g secreted/g consumed), of total n3 fatty acids was lower with CE (0.082 g/g) compared with DDGS (0.109 g/g) or WCS (0.106 g/g), but was not different between WCS and WFS (0.110 g/g). Finally, the transfer efficiency of cis-13 22:1 was twice greater with CE than with WCS (0.198 vs. 0.105 g/g). In conclusion, feeding CE had a negative impact on lactation performance, and more specifically on milk fat yield; an effect that could be explained by the great accessibility of the residual oil contained in this by-product and its consequent interference with lipid metabolism in the rumen. Comparison of WCS with WFS reveals that both oilseeds support similar production efficiency and gross milk composition.