Abstract :
Two 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 C18:1 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 12 g/kg SO or 12 g/kg HPO on a dry matter
(DM) basis. In the first experiment, 6 non-pregnant, non-lactating Lacaune ewes were
used following a 3×3 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 whichwas assigned to one of the three experimental diets for 4weeks.
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 C14:1, C16:1 and C16:0 content
and reduced C18:0 and C18:1 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.
