Impact of blood plasma calcium on lifetime performance

First published in International Dairy Topics Volume 18.4.

The plasma calcium level around parturition has been shown to have a major effect on fertility. The economic impact of improving the calcium level at calving – obtained by supplementing the pre-partum animals with the product X-Zelit, as reported by Kerwin et al. (2018, 2019) – was simulated using the Simherd model.

Reproduction and yield

Supplementing X-Zelit (Vilofoss) in the late part of the dry period is known to increase fertility (Fig. 1) and milk yield (Fig. 2). Fig. 1 shows the proportion of cows not pregnant. Median time to pregnancy was 19 days earlier for cows fed X-Zelit.
This highly improved reproduction result corresponds to a study in New Zealand in which pasture-fed multiparous cows were supplemented with X-Zelit. The cows which were given X-Zelit became pregnant 7.5 days earlier in lactation compared to the control group. In this study, pregnancy was also assessed in relation to when seasonal insemination begins, and it was found that cows in the X-Zelit group became pregnant 13.8 days earlier in the season compared to the control group.
Also, in a trial conducted by Martinez et al. (2012), the normocalcaemic group had 15 fewer empty days compared to the hypocalcaemic group. In the same trial, the probability of a positive pregnancy in normocalcaemic cows was estimated to be 1.61 times higher than the probability in hypocalcaemic cows.

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I was initially reluctant to use X-Zelit because of the cost. However, this has been far outweighed by the health benefits, increased production and a reduction in treatment and labour costs. It has significantly reduced milk fevers and metabolic issues, negating the need to manage cows with calcium. It’s central to our herd management system and it’s simple to implement.