Effect of extruded whole soybean dietary concentrate on conjugated linoleic acid concentration in milk in Jersey cows under pasture conditions

Abstract

Contradictory results has been found on the effects of soybean supplementation and conjugated linoleic acid (CLA) content in milk on feeding systems based on fresh forage The objective of the study was to evaluate the effect of a dietary supplement with different quantities of extruded whole soybean on the production and composition of milk, and CLA concentration or their isomers in Jersey cows under pasture conditions. Twenty-one Jersey cows were randomly assigned into 3 groups of 7 animals each. The cows were supplemented with a dietary concentrate (5 kg d -1 ), and each group received one of the three next treatments: control without soybean (0-SB), with extruded whole soybean at 0.5 kg d -1 (0.5-SB) or at 1 kg d -1 (1-SB). The basic diet was a pasture composed of Lolium perenne (70%), Trifolium repens (25%) and other species. The duration of the study was 75 d. Milk production (p = 0.706) and protein production (p = 0.926) were not affected by treatments. Fat (p = 0.015) and protein (p = 0.045) content as well as fat production (p = 0.010) were lower in the 1-SB group. There was no effect of the inclusion of extruded soybean on total CLA content (p = 0.290) or the content of cis-9, trans-11 (p = 0.582), trans-10, cis-12 (p = 0.136) and cis-10, cis-12 (p = 0.288) isomers. However, concentrations of all isomers were affected by the nutritional quality of the pasture, with low values observed at greater maturity stages of pasture.Additional key words: CLA; dairy cows; grazing; milk quality. ResumenEfecto de la suplementación con concentrado de soja entera extrusionada en vacas Jersey en pastoreo sobre el contenido de ácido linoléico conjugado en la leche El efecto de la suplementación con soja en sistemas de pastoreo sobre el contenido de ácido linoléico conjugado (CLA) en leche es contradictorio. El objetivo de este estudio fue evaluar en vacas Jersey en pastoreo, el efecto de la suplementación de un concentrado con diferentes cantidades de soja entera extrusionada sobre la producción de leche y su composición, especialmente sobre el contenido en CLA y sus isómeros. 21 vacas Jersey fueron divididas al azar en 3 grupos de 7 animales cada uno. Los animales fueron suplementados con un concentrado (5 kg d -1 ) y a cada grupo se le asignó uno de los tres siguientes tratamientos: control sin soja (0-SB), con 0.5 kg d -1 de soja (0.5-SB) y con 1 kg d -1 de soja (1-SB). La base de la alimentación fue el pasto, compuesto mayoritariamente por Lolium perenne (70%) y Trifolium repens (25%). La duración del estudio fue de 75 días. La producción de leche (p = 0.706) y la producción de proteína (p = 0.926) no se vieron afectados. Los porcentajes de grasa (p = 0.015) y proteína (p = 0.045) y la producción de grasa (p = 0.010) fueron más bajos en el grupo 1-SB. Las cantidades de soja no modificaron los contenidos de CLA total (p = 0.290) y de los isómeros cis-9, trans-11 (p = 0.582), trans-10, cis-12 (p = 0.136) y cis-10, cis-12 (p = 0.288), pero si fueron afectados por la calidad nutritiva del pasto, observándose meno...

Conjugated linoleic acid content in milk of Chilean Black Friesian cows under pasture conditions and supplemented with canola seed (Brassica napus) concentrate

“…In the present study, in agreement with the results found in a previous work by Avilez et al (2012), the trans-10, cis-12 and cis-10, cis-12 isomers presented higher values than normally reported in the literature. The regulation of isomer balance is largely unknown.…”

“…All the samples (pasture and concentrates) were ground to pass a 1-mm screen in a Willey mill before analysis. Dry matter (method 934.01), ash (method 942.05), ether extract (method Avilez et al (2012). The analyses of neutral detergent fibre (NDF) and acid detergent fibre (ADF) were carried out according to Van Soest et al (1991), and both NDF and ADF were expressed as exclusive of residual ash.…”

“…At each control, a milk sample of 30 mL was collected (to which was added 0.03 g of potassium dichromate at 0.1% as a preservative). The contents of fat, protein, and urea were determined automatically as previously described by Avilez et al (2012). Somatic cells counts were measured by flow cytometry, using a Fossomatic Electronic Cell Counter (Fossomatic 5000, Hillerod, Denmark).…”

“…Total lipids were extracted by the method of Folch et al (1957), using a mixture of chloroform and methanol (2:1, v:v). The fatty acids (FA) contents were analyzed after transesterification of FA to FA methyl esters (Morrison & Smith, 1964), as previously described by Avilez et al (2012). Briefly, FA methyl esters were analyzed by gas chromatography (HP 6890, Hewlett Packard, Surrey, UK), Flame Ionization Detector (FID), a capillary column SP-2560 (100 m, 0.25 mm i.d.…”

“…The samples were then centrifuged for 3 min at 3,000 rpm and the plasma was aliquoted and frozen (-18°C) in microtubes of 1.5 mL. For each sample, the metabolic prof ile was determined as previously described by Avilez et al (2012).…”