The objective was to reduce saturated fatty acids (SFA) and increase conjugated linoleic acid (CLA, cis-9, trans-11 C 18:2 ), α-linolenic (cis-9, cis-12, cis-15

Compared to pasture based sistems, milk produced in confined dairy systems is characterized by a high saturated fat (SF) content with a lower concentration of healthy fatty acids (FA) such as vaccenic (VA, trans-11C 18:1 ), conjugated linoleic cid (cis-9, trans-11 C 18:2 , CLA), α-linolenic (cis-9, cis-12, cis-15C 18: 3 ), eicosapentaenoic (EPA, C 20:5 ) and docosahexaenoic (DHA, C 22:6 ) whose presence in milk and dairy products can be increased by feeding polyunsaturated FA (PUFA). The aim of the study was to determine the differences in milk composition and FA profile between a regular (Reg) milk (Reg-Milk), a Reg-Dambo type cheese (Reg-DCh) and a Reg yogurt (Reg-Yog) with that obtained after including a blend (7:

ResumenEl objetivo del trabajo fue reducir la presencia de los ácidos grasos (AG) saturados potencialmente aterogénicos (C12:0, C14:0 y C16:0) de la leche y aumentar la presencia del ácido linoleico conjugado (CLA) en vacas lecheras estabuladas alimentadas con ración completamente mezclada (RCM) a través del aporte suplementario de ácidos grasos poliinsaturados (AGPI). Se utilizaron dos lotes de 70 vacas multíparas en el primer tercio de lactancia. Luego de seis semanas experimentales y durante cinco días consecutivos se obtuvieron cinco muestras de leche estándar (LE) provenientes del tanque colector del lote vacas sin AGPI suplementarios, y cinco muestras de leche CLA (LCLA) provenientes del tanque de las vacas suplementadas con los AGPI. El tenor graso (g/100g) de la LE (3,84) resultó superior (p<0,001) al de LCLA (2,84) por reducción (17,21%) de los AG potencialmente aterogéni-cos. El índice aterogénico fue mayor (p<0,001) en la LE (4,07) comparado al de la LCLA (2,58). La concentración del CLA aumentó (p<0,001) un 122% en LCLA (0,77 g/100 g) respecto al valor registrado en LE (0,34 g/100 g). El ácido oleico (g/100 g) resultó superior (p<0,001) en la LCLA (23,37) comparado con la LE (18,78). El aporte suplementario de AGPI permitió incrementar el valor saludable de la leche producida en un sistema de alimentación estabulado manteniendo una adecuada relación (6,59) omega-6/omega-3 en la leche y confirmando la plasticidad en la composición de los AG constitutivos de la grasa láctea. Palabras clave: Vaca lechera, alimentación estabulada, perfil de la grasa láctea. AbstractThe aim of the work was to reduce the presence of the potentially atherogenic fatty acids (FA) of milk (C12: 0, C14: 0 and C16: 0) and increase the presence of conjugated linoleic acid (CLA) in confined dairy cows fed a total mixed ration (TMR) supplemented with polyunsaturated fatty acids (PUFA). Two batches of 70 multiparous cows in the first third of lactation were used. After six experimental weeks and for five consecutive days, milk samples (5) were obtained from the collector tank of non-supplemented cows (LE) and of CLA milk (LCLA) from the tank of PUFA supplemented cows. Fat content (g/100g) in LE (3,84) was higher (p<0,001) than LCLA (2,84) explained by a significant reduction (17,21%) in the concentration of the potentially atherogenic FA of milk. The milk atherogenic index was higher (p<0,001) in LE (4,07) compared to LCLA (2,58). Milk CLA content increased (p<0,001) by 122% in LCLA (0,77 g/100 g FA) compared to LE (0,34 g/100 g FA). Oleic acid concentration (g/100 g FA) resulted higher (p<0,001) in LCLA (23,37) compared to LE (18,78). Supplementation with PUFA in confined dairy cows increased the healthy value of the milk produced maintaining an adequate omega-6/omega-3 ratio (6,59) and confirmed the plasticity in milk fatty acid composition.