The effects of feeding increasing levels of camelina meal as a protein supplement on the performance of Holstein dairy cows.

This study aimed to assess the effects of feeding increasing levels of camelina meal (Camelina var. × Soheyl L.) as a dietary protein supplement to primiparous Holstein cows on feed intake, milk production, milk composition and fatty acid profile, nutrient digestibility, ruminal fermentation variables, microbial nitrogen synthesis, and antioxidant status. Eight Holstein cows took part in a replicated Latin square design (two 4 × 4 squares) of four 28-d periods and 4 diets containing soybean meal and 4 levels of camelina meal: (1) 0 g camelina meal/100 g DM (control), (2) 4.70 g camelina meal/100 g DM, (3) 9.50 g camelina meal/100 g DM, and (4) 14.20 g camelina meal/100 g DM. The cows were kept in individual tiestalls. The cows were given diets ad libitum, ensuring 5% orts during the experiment. We determined intakes; milk production and composition; in vivo digestibility of DM, OM, CP, and ash-free NDF; urinary purine derivatives; microbial nitrogen synthesis; rumen pH; ammonia-N; total and individual VFA; and protozoa numbers. Dietary replacement of soybean meal with camelina meal revealed no significant differences in DMI, milk production, FCM, protein and fat yields, MUN, feed efficiency, and apparent digestibility. Dietary camelina meal did not significantly affect ruminal pH; ammonia-N; VFA, acetic, propionic, and butyric acid concentrations; or total protozoa number. Milk SFA levels were significantly lower, and MUFA and PUFA were significantly higher in cows fed camelina meal compared with the control. There were no significant differences in levels of urinary allantoin, purine derivatives absorbed or excreted, or microbial nitrogen synthesis among the diets, but feeding camelina meal significantly increased total antioxidant capacity in the blood and milk. This study shows that camelina meal can be fed as a total replacement for soybean meal without adverse effects on animal performance and with a positive impact on milk's PUFA and antioxidant capacity. The substitution of camelina meal for soybean meal is a viable alternative for lactating cows in areas where water shortages preclude soybean cultivation. However, based on the statistical power analysis, especially for milk production traits and rumen fermentation variables, it is recommended that further research be conducted on this topic with a larger number of animals.