Abstract
Abstract: The objective of this work was to evaluate the milk fatty acid (FA) profile of Holstein x Gyr cows subjected to two different grazing managements (fixed and variable rest periods) of Urochloa brizantha 'Marandu' pastures. A randomized complete block design was used, with two replicates of pasture areas (blocks) per treatment and four cows per block. Milk production and composition were not affected by grazing strategies. No treatment effects were observed on the proportions (g 100 g-1 of total FA) of the main FAs (palmitic, linoleic, and α-linolenic) of the pasture, but their intakes (grams per day) were affected by differences in forage dry matter intake. The concentrations of FAs in milk plasma and fat were not affected by the treatments. Milk fat contents of rumenic, vaccenic, oleic, and α-linolenic acids varied from 0.71 to 0.93, 1.40 to 1.50, 19.40 to 19.70, and 0.39 to 0.43 g 100 g-1 total FAs, respectively. Grazing strategies of U.brizantha 'Marandu' cause no changes on the milk fatty acid profile of cows.
Highlights
Research indicates that biologically active compounds, naturally present in milk fat, have positive effects on human health, rumenic acid, with anticarcinogenic, antidiabetogenic, antiatherogenic, and immunomodulatory properties, and vaccenic acid, responsible for 64 to 97% of the total secretion of rumenic acid in bovine milk (Shingfield et al, 2008)
The objective of this work was to evaluate the milk fatty acid profile of Holstein x Gyr cows subjected to two different grazing managements on Urochloa brizantha 'Marandu' pastures
The Trt x grazing cycles (GC) interaction was observed for the plasma concentrations of nonesterified FAs (NEFA), glucose and plasma-urea nitrogen (PUN) (Table 1)
Summary
Research indicates that biologically active compounds, naturally present in milk fat, have positive effects on human health, rumenic acid (cis-9, trans-11 CLA), with anticarcinogenic, antidiabetogenic (type 2 diabetes), antiatherogenic, and immunomodulatory properties, and vaccenic acid (trans-11 C18:1), responsible for 64 to 97% of the total secretion of rumenic acid in bovine milk (Shingfield et al, 2008). The main strategy to obtain milk containing fat naturally enriched with rumenic and vaccenic acids is to provide diets with ingredients rich in linoleic (cis, cis-12 C18:2) and α-linolenic FAs. Milk production systems based on pastures with tropical grasses, which have high levels of these two polyunsaturated FAs, are promising models for the production of milk with an FA profile that is more beneficial to human health, in other words, with higher concentrations of rumenic, vaccenic, and oleic FAs, and lower levels of lauric (C12:0), myristic (C14:0) and palmitic (C16:0) saturated FAs (Lopes et al, 2015), which are considered hypercholesterolemic (Fats..., 2010). In pastures of U. brizantha 'Marandu', Madeiro (2014) and Anjos et al (2016) compared the morphological and chemical compositions of pastures managed under fixed 30-day rest periods with variable rest periods, based on the interception of 95% of the photosynthetically active radiation. We did not find studies in the literature evaluating the effect of these two pasture management strategies on the FA profile of cow’s milk
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