Mineral and Citrate Concentrations in Milk Are Affected by Seasons, Stage of Lactation and Management Practices

Frank Dunshea,Peter Doyle,Roderick Williams,Glen Walker

doi:10.3390/agriculture9020025

Frank Dunshea, Peter Doyle + Show 2 more

Open Access

https://doi.org/10.3390/agriculture9020025

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Abstract

This study was conducted to examine associations between nutrition, time of year and season of calving on milk mineral concentrations in 24 pasture-based dairy farms. There was substantial variation in the concentrations (mean with range in parentheses) of Ca 1072 (864–1310) mg/kg; citrate 1579 (880–2080) mg/kg; P 885 (640–1040) mg/kg; Mg 98 (73–122) mg/kg; Na 347 (248–554) mg/kg; K 1534 (1250–2010) mg/kg; and S 295 (155–372) mg/kg with most of the variation associated with stage of lactation, although the influence of days in milk was different for different minerals. Feeding practices were also important in determining the concentrations of some components. Milk Ca, citrate, P, and K concentrations were greater (p < 0.05) in cows receiving mineral supplements, while Ca, P and Mg were positively correlated (p < 0.05) with the amount of concentrates fed. Milk citrate and K concentrations were positively correlated (p < 0.05) with herbage allowance. Milk Se (15 (<3–37) µg/kg) and Zn (3.4 (2.2–4.9) mg/kg) also varied with time of year, with Se concentrations also greater (13.7 vs 11.6 µg/kg) in spring compared with autumn calving herds and positively correlated (p < 0.05) with the amount of concentrates fed and mineral supplementation. These data indicate that calving pattern and feeding practices could be used to reduce variation in the measured milk mineral concentrations.

Highlights

Twenty-four farms that calved in both spring and autumn as well as being representative of dairy farms in northern Victoria were selected for the study
The average concentrations of Ca or Mg in milk did not differ significantly between season of calving (SOC) groups when averaged for stage of lactation (SOL) and the coefficients of variation, minimum, and maximum values for Ca or Mg in milk were similar for both SOC groups (Table 3)
Our study indicated that dairy farmers can influence the concentrations of the macro-minerals and citrate as well as Se and Zn concentrations in milk through the calving system they employ

Summary

Introduction

While seasonal spring calving used to be the predominant practice in northern Victoria, industry statistics indicate that the peak to trough ratio in milk supply in Victoria is less than 2:1 [5]. Large fluctuations in the composition of milk supplied to dairy factories can increase processing costs [6,7,8] through impacts on the efficiency of processing into dairy products and the suitability of the milk for use as ingredients by the food industry (see [6,9,10,11]). Variations in milk mineral concentrations, like variation in milk protein and fat composition, affect suitability for processing.

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