The olive oil industry has a leading position in the Mediterranean countries, resulting in the production of considerable quantities of the respective by-products (OB) that constitute an important environmental issue. OB contain valuable nutrients and bioactive components that can be re-used under the bioeconomy strategy, and several chemical, physical, and biological processes have been evaluated with the intention to improve their nutritional value. One feasible application of OB is their incorporation in the diets of livestock and especially ruminants due to their high fiber content. As indicated by numerous studies, OB dietary supplementation increases the levels of monounsaturated fatty acids (MUFAs) and decreases that of saturated fatty acids (SFAs) in the milk and meat of ruminants with beneficial effects for consumers’ health. At the same time, environmental impact and feeding costs are reduced without detrimental effects on ruminal fermentation, nutrients utilization, growth performance, carcass traits, milk yield and composition.

This study aimed to evaluate the effect of dietary inclusion of ensiled olive cake, a by-product of olive oil production, on milk yield and composition and on fatty acid (FA) profile of milk and Halloumi cheese from cows. Furthermore, the effect of olive cake on the expression of selected genes involved in mammary and adipose lipid metabolism was assessed in a subset of animals. A total of 24 dairy cows in mid lactation were allocated into 2 isonitrogenous and isoenergetic feeding treatments, named the control (CON) diet and the olive cake (OC) diet, in which part of the forages (alfalfa, barley hay, and barley straw) were replaced with ensiled OC as 10% of dry matter according to a 2 × 2 crossover design with two 28-d experimental periods. At the end of the second experimental period, mammary and perirenal adipose tissue samples were collected from 3 animals per group for gene expression analysis by quantitative reverse-transcription PCR. The expression of 11 genes, involved in FA synthesis (ACACA, FASN, G6PDH), FA uptake or translocation (VLDLR, LPL, SLC2A1, CD36, FABP3), FA saturation (SCD1), and transcriptional regulation (SREBF1, PPARG), was evaluated. No significant differences were observed between groups concerning milk yield, fat percentage, protein percentage, and protein yield (kg/d), whereas milk fat yield (kg/d) increased in the OC group. Dietary supplementation with ensiled OC modified the FA profile of milk and Halloumi cheese produced. There was a significant decrease in the concentration of de novo synthesized FA, saturated FA, and the atherogenic index, whereas long-chain and monounsaturated FA concentration was increased in both milk and cheese. Among individual saturated FA, only stearic acid was elevated, whereas among individual monounsaturated FA, increments of oleic acid (C18:1 cis-9) and the sum of C18:1 trans-10 and trans-11 acids were demonstrated in milk and Halloumi cheese produced. Although no diet effect was reported on total polyunsaturated FA, the concentration of CLA cis-9,trans-11 was increased in both milk and Halloumi cheese fat of the OC group. The expression of the genes tested was unaffected apart from an observed upregulation of SREBF1 mRNA expression in perirenal fat from cows fed the OC diet. Milk FA differences observed were not associated with alterations in mammary expression of genes involved in FA synthesis, uptake, translocation, and regulation of lipogenesis. Overall, the inclusion of ensiled OC in cow diets for a 4-wk period improved, beneficially for human health, the lipid profile of bovine milk and Halloumi cheese produced without adversely affecting milk yield and composition or the expression of genes involved in lipid metabolism of mammary and adipose tissues in cows.

The present work aimed to evaluate the effect of farming practices and season on the fat and protein content and fatty acid (FA) profile of milk and Halloumi cheese produced in Cyprus. Over a year, raw bulk-tank milk samples from cow, goat, and sheep farms were collected seasonally from all organic (11) and representative conventional (44) dairy farms, whereas Fresh Halloumi cheese samples were collected monthly from retail outlets (48 organic and 48 conventional samples in total). The different farming practices did not affect the milk fat content of ruminants, while protein levels were decreased in organic bovine and caprine milk. Under organic farming practices, milk and cheese contained increased values of total mono-unsaturated FA (MUFA) and poly-unsaturated FA (PUFA), and specific FA, such as oleic, conjugated linoleic, linoleic, and α-linolenic acids. Total saturated FA (SFA) levels were particularly decreased in organic samples and, consequently, the atherogenic indices of milk and cheese were decreased. Season influenced milk and Halloumi cheese FA profile; spring samples had lower SFA and higher PUFA and MUFA concentrations. Overall, the organic farm practices improved the lipid profile of milk and Halloumi cheese, which is more likely attributed to the different feeding strategies applied in organic dairy farms.

Insect proteins are considered as suitable low environmental impact alternatives to fishmeal for sustainable aquafeeds. Among the different insect species, Hermetia illucens has attracted research and industrial interest due to its ability to grow well on organic side streams, its high protein content and favorable amino acid profiles. Its lipid content although high is characterized by a lack of EPA and DHA that are essential to fish nutrition and thus a defatted form of Hermetia meal might be of better use in fish diets. Hence, two feeding trials were conducted to investigate the effects of the partial fishmeal replacement by increasing levels of a full-fat (up to 276 g/kg) and a defatted (up to 174 g/kg) H. illucens meal on feed intake, growth, feed utilization and nutrient compositions of gilthead seabream (Sparus aurata). Results showed that both the fat content and the inclusion level of H. illucens meal are critical for the success of fishmeal replacement in the diets of S. aurata as they strongly affect feed consumption. A lower palatability of H. illucens meal was observed when included at high dietary levels with the defatted form being more readily accepted by fish. The defatted H. illucens meal is more suitable than the full-fat type to replace fishmeal, with a dietary level of about 81–104 g/kg supporting the highest feed consumption, the highest growth, an unaffected proximate composition and a better feed utilization by S. aurata.

This study aimed to evaluate the effect of short-term forage substitution with ensiled olive cake (OC), on yield, composition and fatty acid (FA) profile of cows' milk. Mid-lactating Holstein-Friesian cows were randomly assigned for 21 days to two isoenergetic and isoproteic feeding treatments (12 animals per treatment), containing 0 and 10% DM of ensiled OC (C and OC groups, respectively). Milk yield was recorded daily, and milk samples were collected at 14 and 21 days of the trial for analyzing the fat, protein, and FA profile of milk. No significant differences were observed in milk yield, protein, and fat nor in protein and fat percentage of milk between groups. However, dietary supplementation with ensiled OC modified the FA profile of cow milk. Feeding cows with ensiled OC resulted in a significant decline of medium-chain FA, while long-chain and monounsaturated FA were risen in milk (P < 0.05). Among individual saturated FA, palmitic was particularly reduced, while among individual mono-unsaturated FA, increments of C18:1 cis-9 were demonstrated with the OC treatment (P < 0.05). Although total poly-unsaturated FA were decreased, the concentration of CLA cis-9, trans-11 tended to be elevated with OC feeding (P = 0.06). Overall, short-term forage substitution with ensiled OC improved, beneficially for human health, the lipid profile of milk without adversely affecting milk yield or milk composition of lactating cows.

The aim of this research communication was to examine the effect of dietary supplementation with wheat-based dried distillers’ grains with solubles (DDGS), a by-product of bioethanol production, on yield, composition, and fatty acid (FA) profile of ewe milk. Forty-five purebred mid-lactating Chios ewes (average milk yield 2.23 kg/d in 96 ± 5 d in lactation) were offered three iso-nitrogenous and iso-energetic diets (15 animals per diet) for a 10 d adaptation period followed by a 5-week recording and sampling period. The diets contained 0, 6, and 12% DDGS on DM basis for the DG0, DG6, and DG12 treatment, respectively, as a replacement of concentrate mix, whilst concentrate-to-forage ratio remained at 60:40 in all treatments. Individual milk yield, milk composition, and FA profile were recorded weekly and analyzed using a complete randomized design with repeated measurements. No significant differences were observed among groups concerning dry matter intake (overall mean of 2.59 kg/d), milk yield or 6% fat-corrected milk and milk protein percentage or protein yield. Milk fat percentage was decreased in the DG12 (4.76%) compared to DG0 (5.69%) without, however, significantly affecting the daily output of milk fat. The concentration of all major saturated FA between C4:0 to C16:0 was reduced, whereas long-chain (>16 carbons), mono-unsaturated and poly-unsaturated FAs were increased in the milk of DDGS groups. Among individual FA, increments of oleic acid and C18:1 trans-monoenes like C18:1 trans-10 and C18:1 trans-11 were demonstrated in DG12 group, whereas linoleic and conjugated linoleic acid (CLA cis-9, trans-11) were elevated in both DDGS groups compared to control. Changes in FA profile resulted in a decline in the atherogenic index of milk by 20% and 35% in DG6 and DG12 treatments, respectively, compared with control. In conclusion, feeding DDGS to dairy ewes increased the levels of unsaturated FA that are potentially beneficial for human health without adversely affecting milk, protein or fat yield.

This study evaluated the effects of different dietary protein levels on growth performance and nutrient utilization of snarpsnout sea bream (Diplodus puntazzo) juveniles. Five isoenergetic diets were formulated to contain a dietary protein level at 30% (P30), 35% (P35), 40% (P40), 45% (P45) and 50% (P50). Each diet was randomly assigned to triplicate groups of fish (IBW 2.80 g) and fed to apparent satiation for 100 days. The dietary protein to energy ratio significantly affected the feed intake with the lower ratios leading to a higher feed consumption. The growth performance of D. puntazzo was gradually increased as the dietary protein level increased up to 40% and then gradually reduced as the dietary protein increased further to 45% and 50%. The feed efficiency got improved as dietary protein levels increased up to 45% but slightly decreased at 50% protein level. A second-degree polynomial regression analysis estimated that a dietary protein level at 41.4% and 43.8% delivered the maximum weight gain and the higher feed efficiency, respectively. The increased dietary carbohydrate and lipid levels in fish fed a low protein diet (P30) resulted in a significant deterioration of feed conversion and growth rates showing also reduced nutrient retentions and causing severe mortalities.