Changes of fat-to-protein ratio from start to the midlactation and the impact on milk yield

Abstract

The aim of the study was to evaluate the changes of fat-to-protein ratio (F/P ratio) from early to mid-lactation and the impact on milk yield. 208 Holstein cows from 3 dairy farms in west Slovakia calved between years 2012 and 2015 were observed. Into the study 908 test-day records of milk yield were included. Cows were from 5 to 150 days in milk (DIM). Statistical analysis and analysis of influence of F/P ratio on milk yield were performed by SAS. The sample of observed cows produced 35.25 ± 11.55 kg*day-1 of milk. The average day in milk was 77.40 ± 41.17 and the average F/P ratio was 1.19 ± 0.25. In acidosis risk were 19.71% of all observation and 8.92% were in ketosis risk. The occurrence of acidosis risk increased and the occurrence of ketosis risk decreased from early to mid-lactation. The model described the variation of milk yield by 44.20%. All of the selected effects except the year of calving had high statistical significant (P<0.01) influence to variation of milk yield. The effect of F/P ratio decreased the milk yield by 4.97 kg*day-1. The highest impact of F/P ratio was observed between 5 and 30 DIM and decreased the milk yield by 6.31 kg*day-1. The average F/P ratio of observations between 5 and 30 DIM was 1.32 ± 0.30. The smallest impact of F/P ratio was found between 61 and 90 DIM and decreased the milk yield by 3.74 kg*day-1. The average F/P ratio of observation between 61 and 90 DIM was 1.16 ± 0.22. It is possible to use F/P ratio as non-invasive indicator of metabolic status to decrease the negative impact to milk yield.