The effect of chopped, extruded and pelleted alfalfa silage on the egg quality of organic laying hens

The experiment was carried out to determine the effect of incorporating young alfalfa in the form of chopped, extruded or pelleted silage in the diet of laying hens on egg quality. Four hundred forty hens, divided into four groups, were used in the study. The control group (A) received a complete feed mixture (CFM), while the silage groups (B, C and D) received a supplementary feed mixture (SFM). The SFM recipe was formulated based on an assumed ingestion of 20% silage in the diet. To achieve the energy requirements of the silage groups, canola oil was incorporated in the SFM. Before ensiling, the alfalfa was chopped for group B and additionally extruded for group C. One half of the extruded silage was pelleted together with the SFM to conform the pelletized silage for group D.

The study showed a mixed effect of silage and the feed mixtures on the parameters measured. For this reason, the daily intake of lipids was calculated to clarify the results. Eggs from hens fed with silage (B, C and D) contained 2.4 times more n-3 fatty acids (FA) than the control (A). Chopped, extruded and pelleted silage showed the same effect on the quality of eggs, but thermally treated silage (C and D) produced yolks with higher concentrations of SFA. The yolks from D exhibited the highest content of odd-numbered fatty acids (15:0, 17:0, 17:1), corresponding to the highest intake of silage. Groups B and C with high canola oil intake showed the highest 18:1 n-9, 22:5 n-3 and MUFA. Furthermore, in spite of the high fat intake, their cholesterol levels were similar to A (A: 12.4; B: 12.3; C: 12.6 mg/g yolk; p > 0.05) due to the anti-cholesterolemic effect of the alfalfa silage. Hens from group D consumed the lowest amount of fat but the highest amount of silage, which corresponding to the lowest level of cholesterol. The fat consumed in the diet was essential in the absorption of carotenoids from the consumed silage. Thus, yolks from the silage groups showed decreasing values for the intensity of red (B: 7.5; C: 6.9; D: 5.2) and yellow (B: 38.6; C: 36.8; D: 32.9) colour as the intake in terms of the amount of fat/silage decreased (B: 6.8; C: 5.0; D: 2.8 fat/10 g silage).