R drop heifers preg testing

Mineral Supplementation Trial #3

In this 3rd phase of our on-farm mineral supplementation trial, we explored whether there is a benefit to using a combination trace mineral supplement (e.g. Multimin) when we’ve identified that we have only a single mineral deficiency, in our case Selenium (Se).

Let’s start by recapping the journey to this point:

Trial #1 Trial #2 Trial #3
Title Growth Response to Supplementation Fertility Response to Supplementation Fertility Response to Supplemtentation
Comparison Multimin vs Cobalife Se Multimin vs Control Multimin vs Cobalife Se
Hypothesis A combination mineral supplement (Mn,Zn,Se,Cu) will result in better growth rates than just VB12+Se. Supplementing maiden heifers with trace minerals prior to joining will result in better fertillity outcomes. Supplementing for only the known deficiencies (Se) will produce an equivelent outcome to supplementing with a combination of trace minerals (Mn,Zn,Se,Cu).
Result No difference in growth rates between groups. Treated group had a higher PTIC rate (+5.5%) and earlier pregnancies than the control. Se only group had a higher pregnacy rate (+10.5%) and earlier pregnancies than the Multimin group.

At the end of the second trial, we were impressed by the higher the pregnancy rate in the treated group. The results indicated that mineral supplementation improves fertility outcomes in our environment – Spring Calving in a Winter/Spring dominant high rainfall zone. The next question we pondered was regarding product selection.  Our blood tests indicate that we are only below critical thresholds for Selenium.  Does a product like Multimin with a combination of minerals give better results than a product with just Selenium?   

Product options for supplementing Selenium

Cost 500ml
(ex GST)
Se mg/ml Rec Dose*
Se/dose (mg) $/ dose
Cobalife VB12+Se $59.50 4 4 16 $0.48
Multimin $318.00 5 5 25 $3.18
Selovin LA $216.73 50 7 350 $3.03
Flukazole /Flukare 0.001 35 0.035
Tasvax 5 in 1 Vaccine 0.5 4 2

*Does Rate for a 350kg yearling.

Firstly thing to notice is the Se in the drenches and vaccines is negligible so we can disregard those options.

Secondly, Se in Selovin LA is in a different form to the other products – Barium Selenate as opposed to Sodium Selonate so the mg/ml is not comparable.

Selovin LA (Barium Selenate) vs Sodium Selonate

Selovin LA is an excellent product for supplementing Se.  According to the label, the long acting nature of the treatment gives cattle coverage for up to 12 months – I’m told that field trials by others suggest it might be even longer.

Cost-wise it compares quite favourably when amortised over 12m, compared to the Sodium Selenate products which last only 3m.

The only drawback is administration is a bit tricky – animals have to restrained and carefully dosed behind the ear to avoid carcase damage – whereas Multimin and Cobalife Se can be injected under any loose skin e.g. to a race full of calves at vaccine booster time, or to yearlings as they’re being weighed.

We are still considering whether supplementing our breeders at preg testing with Selovin La is a logical treatment.  While blood tests indicate those animals are Se deficient, our pregnancy rates are typically in the mid 90’s (percentage PTIC).

Trial #3

We joined 100% of our 2021 born heifer drop.  The heifers were on a rising plane of nutrition and achieved the following average daily gain (ADG):

  • 1.4kgs/day mid-Aug to mid-Sep
  • 1.7kgs/day mid-Sep to mid-Oct
  • 1.1kgs/day mid-Oct to mid-Dec (joining)

We’ve excluded 2 extremely light outliers from the analysis and one freemartin.  The weights of the heifers included in the analysis ranged between 324 to 448kgs at joining.  At 324, the lightest heifer was at 56% of our standard reference weight for mature cows (575kgs PTE BCS 3 at weaning). 

The heifers were randomly divided into two groups (odd and even tag numbers).  The groups contained 36 and 38 head with similar average weights and ADG.  Importantly, both had a similar number of light heifers (< 374kgs).

The heifers were treated one month prior to joining as follows: 

  • Odd tags: 5ml Cobalife VB12 with Se
  • Even tags: 5ml Multimin + 5ml Cobalife VB12 (no Se)

The even tag group also got the shot of Cobalife (without Se) to ensure both groups had the same VB12 treatment.  Both groups had received Cobalife Se 3 months earlier.

The heifers were joined in one mob with 3 yearling bulls.  The (virgin) bulls were vaccinated for Vibrovax and Pestigard and screened for BVDV PIs.  All heifers were screened for BVDV PIs.

Usually we join for 6 weeks but with the market so strong for PTIC heifers we left a bull in for a further 4 weeks (which made the joining 10 weeks) and sold the late calvers. 

We’ve analysed the resulting conception pattern by looking at the foetal aging data at preg-testing.

The first graph (above) looks at the results for the first 6 weeks of joining with pregnancies from weeks 1,2 & 3 combined in Cycle 1, and 4,5 & 6 combined in Cycle 2. Each bar on the graph represents the percentage of the treatment group in each cycle. The big difference in overall pregnancy rate is surprising. I checked the weights of the heifers who did not conceive in the first 6 weeks – the lightest in the Multimin group was 409kg – so that doesn’t explain the difference. 

The second graph offers a detailed week by week breakdown of the extended joining season with the late pregnancies combined for simplicity.  Interestingly, the significant number of heifers who didn’t conceive in the first 6 weeks in the Multimin group did get pregnant in the end.  The total PTE rate of both groups end up being similar at 6-8%.

With the small sample sizes, this on-farm trial does not achieve statistical significance.  That means the data is inadequate to draw a statistical conclusion as it may be pure chance.

At the very least, I’m willing to draw the conclusion that supplementation strategy on Se alone is probably equal to (if not superior) to supplementing with a combination product.

Our Supplementation Strategy

So here’s our response to everything we’ve learned from these trials.  At this stage we are only supplementing young growing cattle and the only product we are using is Cobalife Se.

While we don’t need to supplement B12, Cobalife Se provides a useful dose of sodium selenate and is the closest thing on the market to a Se-only treatment.  It is the most cost-effective option with the four treatments our young heifers receive costing $2.40/head.

We are hopeful that Se supplementation in the summer/autumn period aids immune response to challenges such as pink-eye. However, we have no evidence to support that.

4 months – Mid December
Treat calves when they get their 7 in 1 booster.

7 months – Mid March
Treat weaners along with a worm drench.

10 months – Mid June
Treat yearlings and first calvers along with a winter worm and fluke drench.

13 months – Mid Sep
Treat yearling heifers with alongside another worm drench and pestigard booster.

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