The effect of source and level of copper in the diet on production and health of Holstein cows during transition period

In the current study, the effect of source and level of copper in the diet on production and health of dairy cows using 105 multiparous pregnant Holstein cows from -21 until +15 days relative to calving in randomized complete block design with 3 treatments and 35 replications were investigated. The experimental treatments include: 1) diet containing copper at the NRC recommended levels from copper sulfate source (NRC-S), 2) diet containing copper at twice the NRC recommended levels from copper glycinate source (2NRC-Gly) and 3) diet containing copper at twice the NRC recommended levels from copper sulfate source (2NRC-S). Milk yield and composition were not affected by experimental treatments, but treatment by time interaction showed that cows fed by 2NRC-Gly had more milk than NRC-S group (P<0.05) at 60, 90,120 DIM and cow in 2NRC-Gly produced more milk at 90 and 120 days in milk compared to NRC-S (P<0.05). The somatic cells count for 2NRC-Gly cows was lower compared to NRC-S cows (P 0.05). The incidence of subclinical mastitis at 15 DIM in 2NRC-Gly was lower compared to the other two treatments (P = 0.05). No difference in body weight and body condition score changes were observed across treatments. Blood metabolites and liver enzymes were not affected by adding different Cu sources, but serum albumin postpartum was increased in 2NRC-Gly group relative to the other two groups (P 0.05). Based on the results, adding copper especially by copper glycinate source at twice the NRC recommended levels led to an increase in the serum albumin concentration, a decrease in milk somatic cells count and lower incidence of subclinical mastitis, which could indicate an improvement in health of cows during transition period.