Influence of a supplement containing conjugated linoleic acid on dairy performance, milk fatty acid composition, and adipose tissue reactivity to lipolytic challenge in mid-lactation goats
Résumé
The objective of this work was to evaluate the effect of
the supplementation of conjugated linoleic acid (CLA;
4.5 g of cis-9,trans-11 C18:2 and 4.5 g of trans-10,cis-12
C18:2) on milk performance, milk fatty acid (FA) composition,
and adipose tissue reactivity in dairy goats fed
a high-concentrate diet based on corn silage. Twentyfour
multiparous dairy goats in early to mid lactation
were used in a 10-wk trial, with a 3-wk adaptation to
the experimental total mixed ration that contained corn
silage (35%, dry matter basis), beet pulp (20%), barley
(15%), and a commercial concentrate (30%). Goats
were randomly allocated to 2 experimental groups and
they were fed 45 g/d of a lipid supplement (either CLA
or Ca salts of palm oil added on top of the total mixed
ration). Individual milk production and composition
were recorded weekly, and milk FA composition was
analyzed in wk 2, 5, and 6. In the last week of the trial,
an isoproterenol challenge was performed for 12 goats
before morning feeding. The CLA supplementation had
no effect on dry matter intake (DMI), body weight
(BW), milk yield, milk protein content, and lactose
yield and content, but it significantly decreased milk
fat yield and content by 18 and 15%, respectively. The
decrease in milk fat yield was related to a lower secretion
of FA synthesized de novo, of the medium-chain
FA, and to a lesser extent of the long-chain FA that
are taken up from the peripheral circulation. The CLA
supplementation decreased the proportion of the sum
of C16:0 and C16:1 and the sum of total cis C18:1, and
it increased the proportions of the sum of long-chain
(C >16) and the sum of iso FA without modification
of the total trans C18:1 and the sum of FA synthesized
de novo (C <16). During the first 25 min relative to
isoproterenol injection, the maximal concentrations,
the increases above basal concentration, the changes in
area under the curve, and the total area under the curve
for glucose and nonesterified FA were not affected by
CLA treatment. In conclusion, CLA supplementation
associated with a high-concentrate diet based on corn
silage resulted in decreased milk fat yield, increased
net energy balance, and it did not affect the sensitivity
of the adipose tissue to lipolytic challenge in lactating
goats
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