Proteolytic activity in bovine dry secretions of the early lactation period - Influence of udder infections.

A total of 160 secretion samples collected from all quarters of 40 cows during their dry period were investigated. Compared to healthy udder samples, total somatic cell count of dry secretions of infected udder quarters was reduced. It was obvious that proteolytic activity was markedly increased in secretions of dry cows when compared to lactating cows. All of these animals had healthy udders. The amount of proteolytic degradation products (peptide bound and free amino acids) was also increased in secretion of dry cows. Dry cow secretions from infected udder quarters showed decreased proteolytic activity, in particular to leucine-nitroanilide, as well as a decreased concentration of peptide bound amino acids when compared to secretions from healthy udders and non infected udder quarters. The amount of free amino acids were also reduced in samples of infected udder quarters without clinical symptoms. Similar to lactating cows, samples from dry cows with clinical signs of mastitis showed a higher concentration of free amino acids. These results show that proteolytic activity is decreased in dry cows with udder infections when compared to lactating cows with udder infections.