Influence of milk production traits and genetic effects on milking frequency in an automatic milking system

Abstract

Data from 10 different farms located in the region of Northwest Germany were used to investigate the impact of milk production traits on milking frequencies in automatic milking systems. Further on, genetic parameters for the behavioural trait 'milking frequency per cow and day' were estimated applying different statistical models. The analysis was done based on a generally stratification of cows in different classes for days in milk. The development of the milking frequency over lactation is characterised by a small decrease from the first (0 - 99 days in milk) to the second (100 - 199 days in milk) days in milk class, but a substantial decrease from the second to the third (200 - 299 days in milk) interval. Additionally, cows in first lactation have a higher milking frequency than older cows mainly due to higher activity and curiosity. The correlations between milk fat, milk protein and somatic cell score were slightly negative but near zero. An increase of these components causes a decrease of the milking frequency. The combination of milk protein content and milk urea content reflects the nutritional condition of the cows. Cows characterized by a surplus of energy tend to have fewer visits in the automatic milking system compared with cows having a balanced or even negative status of energy. The genetic impact revealed moderate heritabilities for the number of milkings per day in the range from 0.26 to 0.42 for the different days in milk classes and applied models. In the second half of the lactation heritabilities were slightly higher due to fewer disturbing environmental effects like fetching the cows towards the milking box. In conclusion, heritabilities for milking frequency in automatic milking systems are sufficient to incorporate this behavioural trait in a combined breeding goal for dairy cattle.