EFFECT OF DIET WITH DIFFERENT ROUGHAGE:CONCENTRATE RATIOS ON THE MILK FATTY ACID PROFILE OF HOLSTEIN COWS: A META-ANALYSIS

Abstract

There is much to debate about the quality of the fatty acid profile (PAG) of milk from pasture-fed and feedlot-fed cows. It is clear that there are metabolic changes in the synthesis of fatty acids in milk, which may be related to bioactive functions and human health. Therefore, it is necessary to clarify the PAG modulation through diets with different roughage:concentrate ratios. For this, we propose in this project to evaluate the effect of the roughage:concentrate ratio on the fatty acid profile of milk. A database will be built through systematic research by articles reviewed in databases, between the period 2000 to 2023, containing data from Holstein cows in lactation, milk composition, fatty acid profile and nutritional aspects of the diet. The animals will be grouped into three feeding systems, based on the roughage:concentrate ratio of the diet: 1: High proportion of concentrate (above 40%); 2: High proportion of roughage (up to 20% of concentrate); 3: Diets with the inclusion of concentrates between 21 and 39%. Milk PAG will be submitted to correlation analysis and PROC MIXED will be used to fit generalized least squares regression models, in which studies and eligible variables will be considered random effects. Nutrient intake, milk production and composition will be evaluated and, when significant (P<0.10), inserted into the model. The MEANS procedure will be used to calculate the mean variance, and this will be used to calculate the R2, and the semi-partial R2, which will be used as an adjustment factor to identify the weight of each model variable on the PAG and on fatty acids specific.