An evaluation of casein hydrolyzate in combination with antibiotic for bacterial cure and subsequent increase in milk yield in dairy cows

Bacterial cure associated with the combined treatment was 73.8% in cows, significantly higher than the 51.7% cure recorded when cows were treated only with antibiotic. During the study, the annual milk yield of non-casein hydrolyzate treated and treated control cows increased at ~2% per year, which is consistent with the national annual increase attributed to genetic selection. In cows treated with casein hydrolyzate the increase was 9% (above the 2% expected) in the first lactation after the treatment, and 6.3% (above the 4% expected for 2 years) in the second lactation after treatment. These increases were significantly higher than those in the controls and those expected through genetic improvement.Treatment with casein hydrolyzate at dry-off was shown to be a viable mean to eliminate existing environmental bacterial infection, and to improve milk yield in the next lactation.Active involution of the mammary gland is induced by milk stasis, which in turn triggers a negative feedback regulatory mechanism that leads to precipitous dry off of milk secretion and shrinkage of the secretory tissue (parenchyma) of the mammary gland [1,2]. Involution in cows [3-6] and mice [7,8] is associated with an inflammatory response that is characterized by activation of the glandular immune system, accelerated apoptosis of epithelial cells, and tissue remodeling [1,2,9]. The process of active involution that follows milk stasis in goats [10] and cows [11] can be triggered by the induction of intensive plasmin activity in milk; this, in turn liberates casein-derived active peptides [12]. Infusion of casein hydrolyzate (CNH), which contains active casein-derived peptides, dramatically accelerated the involution, which was completed within 3 days in goats and cows, compared with 3-4 weeks without such treatment, and resulted in a marked reduction in milk yield (MY) even after the first day of treatment [10,11,13]. These responses were manifested in the mammary secretion within 8 h aft