Efectos de la suplementación con sales cálcicas de ácidos grasos insaturados sobre la digestión ruminal en vacas lecheras en pastoreo

The objective of this study was to evaluate the effects of calcium salts of unsaturated fatty acids (Ca-FA) supplementation on rumen digestion by dairy cows grazing high-quality pastures. Three cows with cannulas in the rumen were allocated to three dietary treatments in a 3×3 Latin square design. The cows grazed an alfalfa pasture with a herbage allowance of 30 kg dry matter (DM)/cow. Mean pasture quality was: 23% DM, 71% DM in vitro digestibility, 25% crude protein (CP), and 26% neutral detergent fiber (NDF). The treatments consisted in the supplementation with: T0 (5 kg of ground corn plus 0.4 kg of fishmeal), T1 (similar to T0 plus de addition of 0.8 kg de Ca-FA), and T2 (3.2 kg of ground corn, 0.4 kg of fishmeal, and 0.8 kg of Ca-FA replacing a similar part of the corn on an energy basis). The Ca-FA contained 65% of unsaturated and 31% of saturated FA. Total volatile fatty acids (105 mmoles/L), acetato to propionate ratio (3.0), and ruminal pH (5.8) were not affected by Ca-FA supplementation. Isobutyrate concentration in the rumen was increased in T0 (P<0.01). Parameters of in situ ruminal degradation of DM, NDF, and CP of the pasture were similar among treatments. Neither milk production nor milk composition was affected by the treatments. Overall, the results indicated that unsaturated FA supplementation in the form of Ca-FA avoided negative effects on ruminal pasture digestion, even when ruminal pH was relative low.El objetivo del estudio fue evaluar los efectos de la suplementación sales cálcicas de ácidos grasos insaturados (AG-Ca) sobre la degradación in situ del forraje en vacas en pastoreo. Tres vacas multíparas con fístula ruminal fueron asignadas a tres tratamientos en un cuadrado latino (3×3). Los animales pastorearon pasturas de alfalfa con una asignación diaria de 30 kg materia seca (MS)/vaca y una calidad promedio de 23% MS, 71% digestibilidad in vitro de la MS (DIVMS), 25% proteína bruta (PB) y 26% fibra en detergente neutro (FDN). Los tratamientos fueron: T0 (5 kg de maíz molido y 0.4 kg de harina de pescado), T1 (idem T0 más 0.8 kg de AG-Ca) y T2 (3.2 kg de maíz molido, 0.4 kg de harina de pescado y 0.8 kg de AG-Ca en sustitución isoenergética del maíz). Las AG-Ca utilizadas contenían 65% de AG insaturados y un 31% de AG saturados. Las concentraciones totales de ácidos grasos volátiles (105 mmoles/L), la relación acético/propiónico (3.0) y el pH ruminal (5.8) no fueron afectados por la suplementación con AG-Ca. La concentración de isobutirato fue mayor en T0 (P<0.01). La degradación ruminal de la MS, FDN y PB del forraje no difirió entre tratamientos. Tampoco se detectaron diferencias en la producción y composición de la leche. Los resultados sugieren que la suplementación con lípidos bajo la forma de sales cálcicas de AG insaturados parece haber sido adecuada al no producir efectos negativos sobre la digestión ruminal, aun cuando el pH ruminal fue relativamente bajo

Utilizacion de lipidos protegidos en la nutricion de vacas lecheras. I. Efectos sobre la produccion y la composicion de la leche, y sobre la ingestion de materia seca y energia

International audienc

Milk fatty acid profile from grazing buffaloes fed a blend of soybean and linseed oils

The aim of the study was to examine the changes in milk fatty acid (FA) profile of grazing buffaloes fed either low (L, 276g/d) or high (H, 572g/d) doses of a blend (70:30, wt/wt) of soybean and linseed oils. Fourteen multiparous Mediterranean buffaloes grazing on a native pasture were fed 4 kg/day of a commercial concentrate containing no supplemental oil over a pre-experimental period of ten days. The baseline milk production and composition and milk FA profile were measured over the last three days. After this pre-experimental period the animals received the same concentrate added with either the L or H oil doses for 26 additional days. Milk yield (g/animal/day) did not differ at the start (1776 ± 522 and 1662 ± 291 for L and H, respectively, P<0.622) or at the end of the trial (4590 ± 991 and 4847 ± 447 in L and H, respectively, P<0.543). Baseline milk fat content (g/kg) averaged 77.1 (±20.5) in L and 74.3 (±9.9) in H (P<0.10) and was reduced (P<0.031) to 60.7 (±23.6) and 49.4 (±11.2) (P<0.0031) respectively after L and H with no differences between treatments (P<0.277). Baseline milk protein content (L=43.2 ± 3.4 and H= 44.3 ± 6.9g/kg) increased after oil supplementation (P<0.0001) in both L (73.2 ± 6.0g/kg) and H (68.4 ± 4.9g/kg) without differences between oil doses (P<0.123). Milk fat content of 14:0 decreased after oil supplementation only in the H treatment (5.29 to 4.03, P<0.007) whereas that of 16:0 was reduced (P<0.001) at both L (24.49 to 19.75g/100g FA) and H (25.92 to 19.17g/100g FA) doses. The reduction of total content of 12:0 to 16:0 was higher (P<0.052) in H (32.02 to 23.93g/100g FA) than L (30.17 to 25.45g/100g FA). Vaccenic acid content increased (P<0.001) from 5.70 to 13.24g/100g FA in L and from 5.25 to 16.77 in H, with higher results in the in H treatment (P<0.001). Baseline rumenic acid was sharply increased (P<0.001) in L (1.80 to 4.09g/100g FA, +127%) and H (1.60 to 4.61g/100g FA, +187%) with no differences between L and H (P<0.19). Overall, these results indicate a pronounced improvement in the nutritional value of milk fat from grazing buffaloes fed little amounts (0.276g/day) of a blend of soybean and linseed oils