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Effect of supplementation of grazing dairy ewes with a cereal concentrate on animal performance and milk fatty acid profile
9 pages, 5 tables, 1 figure.-- ISI Article Identifier: 000268136400045.Previously published as proceeding at the Options Méditerranéennes A, 85: 439-444 (2009).
https://digital.csic.es/handle/10261/15655This work was conducted to investigate the effect of
supplementing grazing ewes on pasture with a cereal
concentrate on the milk fatty acid (FA) profile. Ninety
Assaf ewes in mid lactation were distributed in 9 lots
of 10 animals each and allocated to 3 feeding regimens:
1) pasture—ewes were only allowed to graze pasture
(an irrigated sward of Lolium perenne, Trifolium pratense,
and Dactylis glomerata); 2) PS—grazing ewes
were supplemented with oat grain (700 g/animal and
day); and 3) TMR—ewes were fed ad libitum a total
mixed ration (TMR; 80:20 concentrate/forage ratio).
Milk yield and composition were recorded for 5 wk.
The highest milk yield was observed in ewes receiving
the TMR and the lowest in grazing ewes supplemented
with oat grain. Productions of milk fat, protein, and
total solids showed the lowest values in treatment
PS. The atherogenicity index, which comprises C12:0,
C14:0, and C16:0, in PS milk fat was no different from
that observed in milk from animals on pasture (1.53
for pasture, 1.54 for PS, and 3.22 for TMR). Oat grain
supplementation generated higher amounts of C18:0
and cis-9 C18:1 in milk fat than the pasture-only diet,
but significantly decreased the levels of α-linolenic acid
and most of intermediates of the process of biohydrogenation
of this FA. Cis-9 trans-11 C18:2 and trans-11
C18:1, its precursor for endogenous synthesis in the
mammary gland, were lower in PS (0.58 and 1.59 g/100
g of total FA) than in TMR (0.72 and 1.92 g/100 g of
total FA) and very different from the results observed
in grazing ewes receiving no supplement (1.21 and 3.88
g/100 g of total FA). Furthermore, the lowest levels of
trans-10 C18:1 and trans-10 cis-12 C18:2 were detected
in the milk fat of ewes fed pasture. It is concluded that, when pasture quality and availability do not limit dairy
production, supplementation of grazing ewes with oat
grain compromised the milk FA profile without any
significant positive effect on milk production.This work was supported by the Ministerio de Educación
y Ciencia (AGL2005–04760). The authors from
Instituto del Frío (Consejo Superior de Investigaciones
Científicas, CSIC) thank Comunidad Autónoma de
Madrid (S-505/AGR-0153) and the Ministerio de
Educación y Ciencia (Consolider CSD2007–063) for
the financial support. The authors from Instituto de
Ganadería de Montaña (CSIC-Universidad de León)
thank CSIC (200640I212) for the financial support.Peer reviewe