Individual differences in responsiveness to diet-induced milk fat depression in dairy sheepand goats (by Della Badia et al.) Sheep and goats display very different individual degrees of milk fat depression (MFD), which may explain apparent contradictions in the literature. This study represents the first direct comparison in caprine and ovine under diet-induced MFD, and suggests that individual responsiveness would not be predetermined by performance traits or milk fatty acid profile. However, certain candidate milk fat inhibitors seem associated with MFD severity (e.g., trans-10 18:1 and cis-9 16:1). Furthermore, changes in the molar yield of de novo and preformed fatty acids suggest relevant differences in the mechanisms underlying MFD susceptibility, with inter-species effects being only observed in more tolerant animals.

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Milk odd-and branched-chain fatty acids (OBCFA) are largely derived from bacteria leaving the rumen, which has encouraged research on their use as biomarkers of rumen function. Targeted research has examined relationships between these fatty acids (FA) and dietary components, but interactions between the effects of lipids and other nutrients on milk OBCFA are not well characterized yet. Furthermore, factors controlling milk OBCFA in sheep are largely unknown. Thus, the present meta-analysis examined relationships between diet composition and milk OBCFA using a database compiled with lot observations from 14 trials in dairy ewes fed lipid supplements. A total of 47 lots received lipid supplements, whereas their respective controls (27 lots) were fed the same basal diets without lipid supplementation. Relationships between milk OBCFA and dietary components were first assessed through a principal component analysis (PCA) and a correlation analysis. Then, responses of milk OBCFA to variations in specific dietary components (selected on the basis of the PCA) were examined in more detail by regression analysis. According to the loading plot, dietary unsaturated C18 FA loaded opposite to major milk OBCFA (e.g., 15:0, 15:0 anteiso, and 17:0) and were strongly correlated with principal component 1, which described 46% of variability. Overall, regression equations supported this negative, and generally linear, relationship between unsaturated C18 FA levels and milk OBCFA. However, the influence of C20-22 n-3 polyunsaturated FA and saturated FA was more limited. The PCA also suggested that dietary crude protein is not a determinant of milk OBCFA profile in dairy ewes, but significant relationships were observed between some OBCFA and dietary fiber or starch, consistent with a potential role of these FA as biomarkers of rumen cellulolytic and amylolytic bacteria. In this regard, regression equations indicated that iso FA would show opposite responses to increasing levels of acid detergent fiber (positive linear coefficients) and starch (negative linear coefficients). Lipid supplementation would not largely affect these associations, supporting the potential of OBCFA as noninvasive markers of rumen function under different feeding conditions (i.e., with or without lipid supplementation). Because consumption of these FA may have nutritional benefits for humans, the use of high-fiber/low-starch rations might be recommended to maintain the highest possible content of milk OBCFA in dairy sheep.

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Lipids of different unsaturation degree were added to dairy ewe diet to test the hypothesis that unsaturated oils would modulate milk fatty acid (FA) profile without impairing or even improving feed efficiency. To this aim, we examined milk FA profile and efficiency metrics (feed conversion ratio (FCR), energy conversion ratio (ECR), residual feed intake (RFI), and residual energy intake (REI)) in 40 lactating ewes fed a diet with no lipid supplementation (Control) or supplemented with 3 fats rich in saturated, monounsaturated and polyunsaturated FA (i.e., purified palmitic acid (PA), olive oil (OO), and soybean oil (SBO)). Compared with PA, addition of OO decreased milk medium-chain saturated FA and improved the concentration of potentially health-promoting FA, such as cis-9 18:1, trans-11 18:1, cis-9 trans-11 CLA, and 4:0, with no impact on feed efficiency metrics. Nevertheless, FA analysis and decreases in FCR and ECR suggested that SBO supplementation would be a better nutritional strategy to further improve milk FA profile and feed efficiency in dairy ewes. The paradox of differences observed depending on the metric used to estimate feed efficiency (i.e., the lack of variation in RFI and REI vs. changes in FCR and ECR) does not allow solid conclusions to be drawn in this regard.

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Our investigation was to study the effect of protein levels 25% and 30% within each level protein that four levels of Digestarom ® P.E.P. (0.00, 0.01, 0.02 and 0.03%) on growth performance, feed utilization and economical evaluation of red tilapia fingerlings. Red tilapia fingerlings were fed on eight experimental diets composed of two protein levels a 25 % and 30% crude protein within each protein levels supplemented with Digestarom ® P.E.P. at four levels (0.00, 0.01, 0.02 and 0.03%).The results indicated that protein levels 30% and Digestarom ® at 0.02% had positive effect on the final weight, weight gain, specific growth rate, feed conversion ratio and feed efficiency ratio. The interactions of Digestarom® and protein levels have a significantly higher in growth performance, feed utilization, survival rate and economical evaluation.It could be concluded that the best Digestrom ® levels was 0.02% Digestrom ® in each protein levels 25 and 30 % in terms of growth performance, feed utilization, survival rate and economic evaluation.