The use of co-products of the agri-food industry in feeding dairy ruminants

From the perspective of the circular economy, it is crucial to provide alternatives to conventional sources of energy and protein, in order to decrease the level of feed vs food competition. Camelina (Camelina Sativa) cake, and Cardoon (Cynara Cardunculus) cake are by-products of the agri-food industry with high potential in ruminants feeding. These compounds are rich in proteins, essential amino acids, fiber, and contain bioactive compounds such as unsaturated fatty acids (UFA) and polyphenols. The inclusion of Camelina and Cardoon co-products in dairy ruminant diet, in different physiological moments, was evaluated. Several trials with transitioning dairy goats, late lactation dairy goats, goat kids, heifers and dairy cows were performed. Camelina and Cardoon were administered in the form of camelina cake (CAME), cardoon cake (CD) and a mixture between cardoon and camelina cakes (CACD). The direct effects on metabolism and microbiota and the effects on the composition of the milk were evaluated. Moreover, the effects of the maternal milk from goats supplemented with this co-product on goat kids, were also evaluated. Significant level was considered for P < 0.05 and tendency for 0.05< P <0.1. Camelina and Cardoon did not significantly affect intake, rumen pH levels and performance (P > 0.05) in transitioning dairy goats, late lactation dairy goats, heifers, and dairy cows. The intake of milk from goats supplemented with cardoon and camelina cakes did not show any differences in performance between the goat kids (P >0.05). The co-products did not significantly affect protein, urea, lactose, fat content and somatic cells counts (P >0.05) in goat’s milk while were able to modify unsaturated fatty acid content at 4 days in milking (CACD = 2.15 ± 0.11 VS C = 1.7 ± 0.10; CAME = 1.66 ± 0.10; CD = 1.66 ± 10 g/100g; P <0.05). Moreover, milk from goats supplemented with camelina and cardoon cakes showed higher total phenolic compounds (TPC; 22.96 ± 6.76 and 32.49 ± 2.08 mg GAE/l; P <0.05) and antioxidant capacity (AOC; 207.9 ± 4.25 and 195.4 ± 26.6 µmol TE/mL; P <0.05). The administration of camelina cake in heifers influenced rumen microbiota both at 28 and 56 days of treatment, showing significant 𝛽-diversity values between CAME and C group. Higher expression levels for genes involved in follicular developmental competence were detected in CAME group compared with C, suggesting a positive effect of treatment diet on fertility in heifers. In dairy cows, CAME had a reduced milk fat percentage (4.27±0.14 vs. 4.72±0.14%; P < 0.05) compared to C but not a reduced production of fat (1.11±0.05 vs. 1.17±0.05 kg; P >0.05). Saturated milk fatty acids were also reduced in CAME (2.8 vs. 3.14 g/100 g; P < 0.05) and linolenic acid and rumen biohydrogenation intermediates were increased in CAME. Overall, these co-products could be excellent protein sources alternatives to soy also because more environmentally sustainable.