The aim of this work was to evaluate the interactive effects of different rates of nitrogen and potassium fertilisation on the phenolic composition of grape berries during ripening. To achieve this objective, in 2000 a trial was carried out in a Tempranillo vineyard located in the 'Ribera de Duero' Apellation d'Origine area (Spain). The plants were treated with three nitrogen (0, 50 and 200 g N per vine) and three potassium (0, 60 and 120 g K 2 O per vine) doses, applied as ammonium nitrate and potassium sulphate respectively, in a randomised complete block design with four replications. The rate of fertilisation did not significantly affect either the vigour or productive capacity of the vines or the size of the berries. However, high nitrogen doses caused a substantial delay in the accumulation of sugars during ripening compared with other treatments. High potassium supplies caused decreases in the total acidity of the berries but did not affect the chromatic parameters of the must at harvest. Three different stages could be distinguished in the development of total polyphenol contents in grape skins during ripening: a slow initial increase, a sharp accumulation during the fifth and sixth weeks after veraison and a final period of reduction until harvest. The vines with no added nitrogen showed more accumulation of polyphenols in the skin than those with other treatments, especially during the last few weeks of sampling. These differences between nitrogen treatments became less as the potassium fertilisation dose was increased. The nitrogen dose of 50 g N per vine increased the levels of anthocyanins in the skin (600 mg l −1 standard extract) compared with the untreated control vines (532 mg l −1 ), and this significantly increased the colour density of the must. The degree of polymerisation of condensed tannins decreased when the ratio N:K was balanced and the amounts of both nutrients applied were high.
ARTICLE INFO ABSTRACT
Keywords:Vegetable fats Milk performance Milk CLA Dairy eweTwo experiments were carried out to study the effects of supplementing the ration of lactating ewes with vegetable fats (sunflower oil, SO or hydrogenated palm oil, HPO; HIDROPALM®) on diet digestibility, milk yield and milk composition, and on the concentration of the conjugated linoleic acid (CLA) C18:2 cis-9 trans-11 and C18:l trans-11 (vaccenic acid, VA) and other main fatty acids in milk fat. Treatments involved a control diet, without added oil, and 2 diets supplemented with either 12g/kg SO or 12g/kg HPO on a dry matter (DM) basis. In the first experiment, 6 non-pregnant, non-lactating Lacaune ewes were used following a 3 x 3 replicated Latin Square design. Addition of vegetable fat supplement to the diet increased digestibility of DM, organic matter (OM) and crude protein (CP), but did not affect that of the ether extract (EE), neutral detergent fibre (NDF) or acid detergent fibre (ADF). In the second experiment, 60 Lacaune dairy ewes mid-way through lactation (120 ±12 days in milk, 0.98 ± 0.03 kg/day average milk yield) were divided into three equalsized groups each of which was assigned to one of the three experimental diets for4 weeks. Compared with the control treatment, supplementation with HPO increased milk yield and energy-corrected milk. But neither vegetable fat supplement modified percentages of fat and protein in milk. Supplementation with HPO increased C14:l, C16:l and C16:0 content and reduced C18:0 and C18:l cis-9 content in milk fat. Supplementation with SO increased the VA content in milk fat by 36% and that of cis-9 trans-11 CLA by 29% in comparison with the control diet. Supplementation with HPO led to milk fat with 15% more cis-9 trans-11 CLA than control milk. In conclusion, adding a moderate dose of HPO or SO to the diets increased CLA concentration in milk fat. Nevertheless, supplementation with SO was more effective than HPO in increasing CLA concentration in milk fat and reducing the atherogenicity index, improving milk quality from the human health standpoint.
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