The Basque Neiker-Tecnalia technological centre, in collaboration with the Faculty of Pharmacy at the University of the Basque Country (UPV/EHU), has demonstrated the benefit of alperujo as a supplement to the diet of dairy sheep during periods when grazing is not available. The analyses undertaken show that sheep fed with alperujo (a sub-product of the olive obtained after milling and pressing) produce milk with healthier characteristics, with a high concentration of unsaturated fatty acids — greater than the milk produced by the same animals before being fed with this sub-product. Thus, alperujo is shown to be a beneficial feed complement for this kind of farm animal.
Sheep that feed on pastures and/or vegetable oil-based supplements show increased the concentration of certain health compounds of the resulting milk and cheese, such as unsaturated fatty acids amongst which are isomers of conjugated linoleic acid (CLA), antioxidant compounds and certain volatile aromatic compounds. Unsaturated fatty acids are essential for the correct functioning of our bodies and should be administered in sufficient quantities in the diet. Their lack in a diet is associated with coronary diseases and a high level of cholesterol.
The research carried out jointly by Neiker-Tecnalia and the Faculty of Pharmacy at the UPV/EHU reveals that stabled sheep which ingest alperujo produce milk with a CLA concentration very similar to sheep that graze. Thus, this feed complement would enable obtaining healthy milk and cheese at any period of the year.
The study was carried out with 12 sheep of the latxa breed in their fifth month of milking. Before starting the trial, milk samples were taken from all the sheep and, in order to act as reference values, zootechnical parameters (milk production = MP, live weight = LW, body condition score = BCS) were determined, as well as milk composition (crude fat content = CF and crude protein = CP) and quality (fatty acids profile). The trials lasted four weeks, in which the animals were kept indoors. The alperujo was administrated with the concentrate during milking, in an increasing amount from 50 to 200 g per sheep per day. Small amounts of vanillin and sugar were added to make ingestion more attractive.
The results regarding fatty acids showed that ingestion of alperujo provides milk with a concentration of unsaturated fatty acids greater than that produced by sheep before its administration. Likewise, it was observed that the ingestion of alperujo increases the content of vaccenic acid (unsaturated fatty acids). It was also shown that the atherogeneicity index are considerably lower in milk obtained with an alperujo diet.
Focusing on the sensorial analysis of boiled milk, no taste or smell different from milk samples prior to the trial was found. Likewise, no different taste was found in the yoghourts made from the trial milk compared to the control ones. As regards the zootechnical parameters, ewes milk production was in accord with the lactation stage at the time and increased their levels of reserves.
The results(*) show that alperujo is a food supplement of great benefit given that, on its ingestion, milk with beneficially healthy characteristics is produced: increase in content of vaccenic acid, reduction in saturated fatty acids and a lower atherogenicity index (IA). With respect to zootechnical parameters, the ingestion of alperujo enables maintaining milk production while the sheep increase their reserve levels. Given all this, it turns out to be a highly useful supplement in those periods of low or zero availability of grazing pasture, during winter months for example. The research working team aim to continue in this vein as, from a technological point of view, the processing and conservation of the alperujo has to be improved.
The project was financed by the Basque Government and the National Institute for Agricultural and Stock-Feeding Research and Technology (INIA in its Spanish initials), and was made possible thanks to the collaboration of the La Maja and Mendia olive presses in Navarre, as well as the Association of Olive Growers of the Rioja Alavesa (ADORA) and the industrial refrigeration company, FIASA.