Association of bulk tank milk urea nitrogen concentration with elevated individual cow values and investigation of sampl
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Association of bulk tank milk urea nitrogen concentration with elevated individual cow values and investigation of sampling frequency for accurate assessment Nektarios Siachos 1
&
Nikolaos Panousis 2 & Georgios E. Valergakis 1
Received: 30 November 2018 / Accepted: 29 May 2019 # Springer Nature B.V. 2019
Abstract Individual milk urea nitrogen (MUN) levels ≥ 19.63 mg/dL have been recently reported to significantly affect fertility. The objectives of the present study were to (a) predict the percentage of cows with elevated MUN within a herd using bulk tank (BTMUN) levels, in the absence of individual MUN records, and (b) establish a sampling frequency protocol for the assessment of actual BTMUN levels. A database of 17,687 monthly individual MUN and concurrent 229 monthly BTMUN records from 24 dairy herds was used. A ROC analysis was performed to determine the BTMUN threshold over which cows in the herd have elevated MUN concentrations that, based on literature, affect fertility. Moreover, a regression was run to predict the percentage of cows with elevated MUN within a herd from BTMUN values. A second database of 10,687 daily BTMUN records from 29 herds was used to identify an appropriate sampling frequency to assess the actual BTMUN levels. Eleven different sampling frequencies ranging from once to 8 times per month were assessed. A BTMUN value of 15.76 mg/dL was the optimum threshold over which cows with elevated MUN concentrations are included in a herd. The percentage of cows with elevated MUN values can be accurately predicted using BTMUN values (R2 = 0.872; P < 0.001). A bulk tank sampling frequency of once per week seems appropriate for most herds in order to assess the actual BTMUN levels, in case daily BTMUN values are not available from milk processors. Keywords Bulk tank . Cattle (dairy) . Milk urea nitrogen . Sampling frequency
Introduction In lactating dairy cows, milk urea nitrogen (MUN) concentration is considered a valuable tool in evaluating nutritional imbalances and predicting urinary nitrogen excretion to the environment (Jonker et al. 1998). It is affected by breed and parity of the cow, milk production and components’ content, stage of lactation, and individual cow variation; however, MUN concentration is mainly affected by nutritional factors such as dietary crude protein (CP) content, ratio of rumen * Nektarios Siachos [email protected] 1
Laboratory of Animal Husbandry, Faculty of Veterinary Medicine, School of Health Sciences, Aristotle University of Thessaloniki, P.O. Box: 393, 541 24 Thessaloniki, Greece
2
Clinic of Farm Animals, Faculty of Veterinary Medicine, School of Health Sciences, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
degradable protein (RDP) to rumen undegradable protein (RUP) fractions, ruminally available energy to protein ratio, and total amino acids reaching the small intestine (Patton et al. 2014). A herd-level MUN concentration target of 8–12 mg/ dL, resulting from individual cow values, was proposed by Kohn et al. (2
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