Mineral supplements scrutinised
A research study into the use of mineral supplements with dairy heifers grazing low-quality wheat has found that the quality of feed may negate the impact of the minerals on weight gain.
Mineral supplementation for sheep grazing a wheat crop is a common industry practice to improve weight gain.
The trial, run at the Dookie campus of the University of Melbourne, found the mineral supplements afforded no significant weight gain, compared to the control group.
The low-quality wheat during draught period was fed to both groups of heifers.
Two minerals, magnesium oxide and coarse salt, mixed at 1:1 ratio were offered to grazing heifers ad libitum.
The two treatments for the trial comprised one group grazing wheat only, which served as a control group, and grazing wheat with mineral supplementation in the other group.
University lecturer in livestock nutrition and grazing management, Dr Paul Cheng, conducted the trial in spring/summer, 2017.
‘‘The lack of weight gain to mineral supplementation in this study may be due to inadequate crude protein supply to the animal,’’ Dr Cheng said.
The other hypothesis being tested in the trial, was the effect of mineral supplements on the level of nitrogen contained in the animals’ urine.
This could have an impact on environmental pollution.
‘‘The study indicates that protein deficiency may override the mineral deficiency when heifers grazed mature wheat, and this may have led to no mineral supplementation effect on heifer performance,’’ he said.
‘‘The level of protein in grazing wheat needs to be considered in feeding minerals to heifers in draught season.’’
Dr Saranika Talukder, a co-investigator of this study, said mature wheat crude protein content was substantially below the growing heifers’ requirements, which may be the cause of having insignificant differences in weight gain and urinary nitrogen content between the two groups tested in this study.
‘‘A future indoor study is needed to confirm the result by establishing the interrelationships between feed intake, water intake, urine volume and nutrient output in the urine,’’ Dr Talukder