Milk production and fatty acid profile of dairy cows grazing four grass species pastures during the rainy season in small-scale dairy systems in the highlands of Mexico

Abstract

The study evaluated small-scale dairy systems with continuous grazing of pastures based on three temperate grasses festulolium (FL), tall fescue (TF), and perennial ryegrass (RG), compared with subtropical kikuyu grass (KG). All pastures were associated with white clover (Trifolium repens L.). Twelve multiparous Holstein cows were assigned to a 4 × 4 Latin square replicated three times with 14-day experimental periods. Sampling and analyses of pastures, concentrates, and animal variables followed standard procedures. FL showed a significantly (p < 0.05) higher mean sward height, but there were no differences (p > 0.05) in net herbage accumulation. There were significant differences (p < 0.05) among pastures for CP, NDF, ADF, in vitro digestibility of OM (IVOMD), and estimated metabolizable energy (eME). There were no differences (p > 0.05) between treatments for milk yield and composition, live weight, or body condition score. There were significant differences (p < 0.05) in fatty acid values for pastures in C14:0, C16:1, and C18:3n3. There were significant differences between treatments (p < 0.05) in milk contents for C18:0, C18:1t11, and C18:2c9t11. Grazing FL, TF, RG, or KY pastures showed no differences in milk yields. Higher values for C18:0, C18:1t11, and C18:2c9t11 were detected in KY, RG, and TF. RG had significantly higher MUFA than FL and higher PUFA than TF. A value under 65% of SFA, a ratio of n-6/n-3 lower than 4, and an atherogenic index of 1.7 are indicators of milk with beneficial effects for human health.

Black oat (Avena strigosa Schreb.) grazing or silage for small-scale dairy systems in the highlands of central Mexico. Part II. Fatty acid profile of feed and milk

“…Several authors (Kay et al, 2004;Morales-Almaráz et al, 2011;Vicente et al, 2017;Vieyra-Alberto et al, 2017) have stated that grazing dairy cows have higher intakes of linoleic (C18:2) and linolenic (C18:3) acids compared to confined cows due to the larger intake of these fatty acids from fresh herbage. This increases rumenic (C18:2c9t11) and vaccenic (C18:1t11) acids in milk, such as observed in Experiment 1 in milk, where PUFA content in milk was higher when cows grazed the black oat regrowth; with higher levels than reported by Plata-Reyes et al (2018), who reported a mean of 2.9 g 100 g -1 compared to 3.7-4.0 g 100 g -1 in the work herein reported.…”

“…Milk fat was extracted and methylated by methods described by Christie (1982), modified by Chouinard et al (1999). Separation and determination of methyl esters of fatty acids of herbage, commercial concentrate and milk was by gas chromatography (Clarus 500, Perkin Elmer, Waltham, Massachusetts, USA), with a capillary column 100 m × 0.25 mm × 0.2 μm (SP-2560, Supelco, Bellefonte, Pennsylvania, USA), with nitrogen as carrier gas (Plata-Reyes et al, 2018).…”

Black oat (Avena strigosa Schreb.) grazing or silage for small-scale dairy systems in the highlands of central Mexico. Part I. Crop and dairy cow performance

“…Net herbage accumulation (NHA) and sward height (at the end of each experimental period) with a sliding plate grass meter followed procedures described by Plata-Reyes et al (2018). NHA estimation was from six 0.25 m 2 exclusion cages per treatment cutting to ground level with shears a 0.4 × 0.4 m quadrant.…”

“…Therefore, in the multiple 3×3 Latin squares repeated three times, simultaneous in space and time with cows nested into squares (groups), the number of observations per treatment was 9, leaving 14 degrees of freedom for the residual error term. The use of this design has proven useful for on-farm experiments (Celis-Alvarez et al, 2016;Burbano-Muñoz et al, 2018;Plata-Reyes et al, 2018).…”

Body Condition Score and Milk Production on Conception Rate of Cows under a Small-Scale Dairy System

“…Mexico is the 14th largest milk producer in the world and the second in Latin America [5]. Furthermore, small-scale milk production farms approximately contribute 35% to marketed national milk production, own approximately 23% of the cattle inventory, and represent 78% of dairy herds in the country [6,7]. Despite the importance of the small-scale dairy system, these farms operate sub-optimally, which compromises profitability [8,9,10].…”