Estabilidade do concentrado armazenado em silos metálicos na fazenda leiteira : uma análise sobre a inclusão de gordura poliinsaturada

Abstract

Brazil has been standing out as one of the largest manufacturers of commercial concentrates for milk farms. Due to the lack of labor, land and structure, most milk producers prefer to buy this ready-made food from the animal nutrition industry instead of producing it. There is a very shortage of scientific studies that demonstrate the behavior of these coherent formulations during their storage time on the farms. Thus, this work aimed to evaluate the stability of a concentrate with inclusion of polyunsaturated fat during its storage in metallic silos on the farm. We verified the possible variations in the chemical and microbiological profile, and consequently, the final stability of this formulation. For this experiment, a medium-sized dairy farm located in the transition area between the mountainous region and the Middle Plateau of the State of Rio Grande do Sul was chosen. Four metallic silos were used to store the concentrate during the months of April and May 2020 The silos were equipped with devices that measure and record the temperature and relative humidity of the indoor and outdoor air 24 hours a day, from the beginning to the end of the experiment. The samples were collected and analyzed on days 0, 7, 14, 21 and 28 of storage to characterize the possible variations in the concentrate. The profiles of fatty acids (FA), vitamins A (retinol) (VIT A), D3 (cholecalciferol) (VIT D3) and E (tocopherol) (VIT E), non-protein nitrogen (NPN), crude protein (CP) were evaluated ), ether extract (EE), calcium (CA), phosphorus (P) and mineral matter (MM), moisture (M), hydrolytic acid index (IAH), water activity (WA) and pH, counting of molds and yeasts (MYC), aflatoxins B1 (AFLA B1), B2 (AFLA B2), G1 (AFLA G1) and G2 (AFLA G2) and total aerobic count (TAC). The experimental design was completely randomized, with five treatments (D0, D7, D14, D21 and D28) and four replications (S1, S2, S3 and S4). The behavior of the average internal temperature (TIA), average external temperature (TEA) and relative humidity of the average internal air (HIA) and relative humidity of the average external air (HIE) of the metal silos where the concentrate was stored were studied. The TIA of the silo was higher when compared to TEA, suggesting that metallic silos heated the concentrate during storage. HEA was higher than HIA, suggesting that metal silos protect the concentrate from exposure to HEA. The chemical profile showed that linoleic FA was found in large quantities in the concentrate (38.67%), while free FA were found in a smaller quantity (0.56%). VIT A was the one with the greatest reduction in the concentration level (43.34%), followed by VIT D3 (41.09%) and VIT E (6.99%), in which the thermosensitivity of these fat-soluble vitamins was visible with the internal heating of the silo. The variables CP (p=0.05), EE (p=0.03), P (p=0.05) and MM (p=0.01) were affected by the treatment time. NPN, CA and P did not suffer this action. We observed a significant decrease in HIA (p=0.05) and Ph (p=0.05) in the concentrate, however, M and WA were not affected with the treatment. The microbiological profile showed a decrease in MYC during the storage period (p=0.007). TAC and AFLA B1, AFLA B2, AFLA G1, AFLA G2, were not affected by storage in metallic silos on farms. The concentrate with polyunsaturated fat showed stability during the storage period tested in metallic silos on the dairy farm.