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Abstract
AIMS: To determine the effect of dose and frequency of injection of Cu as Ca Cu EDTA on concentrations of Cu in liver, and the effect of a single 200 mg treatment on milk production and reproductive performance in New Zealand dairy cows.
METHODS: Four groups of dairy cows (n=18 per group) on three farms were injected with 100 or 200 mg Cu S/C once, or three times at 6-weekly intervals, commencing 6−8 weeks into lactation. Concentrations of Cu in liver were determined to 119 days after treatment. Cows at peak lactation on one farm were treated with 200 mg of Cu S/C, or received no treatment (n=92 per group). Milk production was determined 11 days before and 24 hours following treatment. In seven dairy herds from throughout New Zealand cows were injected S/C with 200 mg Cu 10 days prior to mating start date (MSD) or received no treatment. Oestrus detection and artificial inseminations were carried out for ≥24 days from MSD. Pregnancy diagnosis was performed at 12 weeks following MSD. The percentage of cows inseminated in the 21 days after MSD (21-day submission rate; n=2,022) and cows pregnant after 21 or 28 days (21- and 28-day pregnancy rates; n=2520) was determined.
RESULTS: Injecting with 200 mg Cu once or 6-weekly increased concentrations of Cu in liver compared with 100 mg (p<0.05). Injection of 200 mg Cu decreased total milk yield (p=0.006) and protein production (p<0.001) in the 24−36 hours after treatment. Compared with Control cows, 200 mg Cu 10 days before MSD reduced 21-day submission (78 vs. 75%; p=0.04) and 21-day pregnancy rates (47 vs. 43%; p=0.03). For 28-day pregnancy rates there was a farm by treatment interaction (p=0.02), with a negative effect observed on some, but not other, farms.
CONCLUSIONS: Injection of 200 mg Cu raised concentrations of Cu in liver for >42 days. A negative impact on milk yield and composition occurred immediately following injection. Injection 10 days prior to mating had a negative effect on submission and pregnancy rates. Further study is required to determine a safe treatment to mating interval and the mechanism by which adverse impacts occur.
CLINICAL REVELENCE: Although 200 mg of Cu as Ca Cu EDTA is an effective supplement and generally well tolerated, determining the necessity for, and giving specific thought to the timing of, parenteral Cu supplementation is imperative to avoid negative impacts on herd production and reproductive performance.
Acknowledgement
A huge debt of thanks is owed to the farmers involved in these studies; I Lyons, T Walters, S Goodwright, G and J Wright, Ranginui Farms, Tussock Creek Dairies, Andrews Farms, Caldwell Farming, Van Vleit and Hodge; to the veterinarians involved including P O'Reilly, G Wouda, S Cranefield, M Bryan, R Shepherd, K Cox-Witton; to the reviewers of the New Zealand Veterinary Journal whose constructive criticisms have improved this paper substantially from its initial form. A special thank you is made to Neville Grace whose assistance in preparing the final draft has been invaluable. The studies were funded by International Animal Health Products Ltd.