Estabilidade do leite: características físico-químicas e parâmetros de desempenho de rebanhos especializados das raças holandesa e jersey

Abstract

The stability of milk during thermal processing is an important issue for dairy industries, especially in the manufacture of products that undergo heating at high temperatures. The objective of research was to evaluate the stability of milk to ethanol and its relationship with the physicochemical characteristics of the milk and with the performance parameters of specialized herds of Holstein and Jersey breeds, in farms with a high degree of technification. Were used 63 animals of the Holstein breed and 71 animals of the Jersey breed. Samples were collected every two weeks, without the addition of preservatives. In the laboratory, the samples were stored under refrigeration at 4°C for 11 hours. The samples were subjected to analysis of titratable acidity, ethanol testing, ionic calcium concentration, cryoscopy and chemical analysis of milk (protein, fat, lactose, total solids and somatic cell count). Were also performed analysis of body condition score and somatic cell score. Data were classified by breed and statistical analyzes were performed separately. Descriptive analysis, correlations and linear association were performed using the SAS® statistical program. To determine the association of variables, a multivariate analysis was performed, more specifically the analysis of main factors. Logistic regressions were calculated to determine which original characteristics and which main factors increased the risk of occurrence of LINA, using the SAS® statistical program. The stability of milk from specialized Holstein and Jersey breed animals was considered high, with a large proportion of milk samples stable in ethanol above 80% v/v. Only 20% of samples from both breed were considered LINA. The composition of the milk of the herds was not affected by the stability level, however, the greater number of deliveries and days in advanced milk had a greater impact on the occurrence of milk instability in the Holstein breed and the higher total solids content had a greater impact on the Jersey breed. In the Holstein breed, advanced SLI and CCS negatively interfered with lactose content and milk stability. ECC was not significantly correlated with stability in the two breeds. Acidity was associated with instability in the Holstein breed. However, in the Jersey breed this association was not observed due to the presence of higher natural acidity in the milk. The Holstein breed had a higher percentage of high stability milk samples compared to the Jersey breed, indicating that acidity was not a factor causing the lowest percentage of stable samples. Holstein and Jersey breeds showed a strong association of Ca2+ with stability. Ca2+ was considered the main factor associated with milk instability in both breeds, demonstrating that this is an important parameter in the assessment of stability.