As the breeding season approaches, Irish farmers are shifting their focus to the critical metrics that drive profitability: conception rates, calving intervals, and the future performance of the calf crop.

While improved genetics and grassland management are staples of modern farming, the role of trace mineral status in reproductive success is often underestimated.

In Ireland, where production systems rely heavily on grass and forage, addressing the "trace mineral gap" before breeding can provide the essential edge needed to maximise herd fertility.

The Irish mineral challenge

Grass and grass-based forages are the backbone of Irish agriculture, yet they are frequently deficient in essential trace minerals.

A report by Rogers and Murphy highlighted that Irish grass silages are commonly low in key nutrients, with 63% found to be low in copper, 69% very low in selenium, and 29% low in zinc.¹

Furthermore, the presence of antagonists such as iron, sulphur, and molybdenum often high in feed, forage, and water exacerbates the issue.

These antagonists bind to minerals in the rumen, significantly reducing the absorption and bioavailability of oral supplements like licks or boluses.

This creates a scenario where cattle may be sub-clinically deficient despite oral supplementation, leading to compromised immunity and enzyme function before clinical signs ever appear.

The role of injectable trace minerals (ITMs) in reproduction

Unlike oral supplements, an injection bypasses the rumen and antagonists, entering the bloodstream within eight hours and the liver within 24 hours.

This rapid delivery is crucial for fertility, as specific minerals play vital roles in reproductive physiology:

Manganese: This mineral is critical for producing cholesterol, a precursor for steroid hormones like oestrogen, progesterone, and testosterone, making it essential for reproductive performance;
Zinc: Beyond its role in immunity and skin health, zinc is a key player in the antioxidant pathway, protecting cellular health, including that of oocytes and sperm;
Selenium and copper: These are fundamental for growth, energy generation, and preventing oxidative stress, which can damage reproductive cells.

Scientifically proven fertility benefits

Strategic supplementation with ITMs prior to breeding has been shown to deliver measurable improvements in reproductive outcomes for both dams and sires.

For beef cows and heifers, studies have demonstrated that administering ITMs pre-breeding can improve conception rates,⁴ and calving distribution.⁵

In one study involving fixed-time artificial insemination (FTAI), cows treated with ITMs achieved a 9% higher conception rate compared to the control group.⁶

Furthermore, treated herds saw 12.5% more cows calving within the first 20 days of the calving block.⁷

A tighter calving pattern is economically significant; calves born earlier in the season have higher weaning weights, and heifers born early are more likely to be cycling at the start of their own breeding season.⁸

For dairy herds, the benefits extend to reducing early embryonic loss.

Roughly one-third of pregnancies in cattle are lost in the first 30 days.⁹

Trials have shown improved pregnancy rates in heifers undergoing timed embryo transfer (TET) when supplemented with ITMs.¹⁰

Additionally, by supporting immunity and reducing the incidence of transition diseases like endometritis,¹¹ metritis,¹² and mastitis,^13,14 ITMs help cows recover from calving faster, allowing them to cycle sooner.

Bulls also benefit significantly. Supplementation has been shown to increase sperm quality and progressive motility, ensuring the male side of the fertility equation is optimised.¹⁵

Strategic timing for maximum impact

Trace mineral demand fluctuates throughout the production cycle.

Topping up levels immediately prior to high-demand periods ensures the animal has the reserves needed to perform.

For the upcoming breeding season, the recommended protocol is to administer ITMs 10-30 days pre-breeding for dairy and beef cows, and 45-60 days prior to the breeding season for breeding bulls.

This timing ensures that mineral status is optimal exactly when gamete quality and hormone production are most critical.

Achieving marginal gains in fertility can have a substantial impact on a farm's bottom line.

By overcoming the limitations of oral toxicity and antagonists common in Irish forage, ITMs offer a fast, precise, and scientifically proven method to support reproductive performance.

As you prepare your herd health plan this spring, discuss with your veterinary practitioner how strategic injectable trace minerals can help secure a tighter calving block and a more productive future herd.

1. Rogers, P.A.M. and Murphy, R. (2000). Levels of Dry Matter, Major Elements (calcium, magnesium, nitrogen, phosphorus, potassium, sodium and sulphur) and Trace Elements (cobalt, copper, iodine, manganese, molybdenum, selenium and zinc) in Irish Grass, Silage and Hay. http://homepage.eircom.net/~progers/0forage.htm ↩︎
2. Adapted from Wikse S (1992). Beef cattle short course. In Texas A&M Vet Beef CattleShort Course, College station, TX, USA. ↩︎
3. Ibid. ↩︎
4. Sales J, Pereira R, Bicalho R, Baruselli P. Effect of injectable copper, selenium, zinc and manganese on the pregnancy rate of crossbred heifers (Bos indicus x Bos taurus) synchronized for timed embryo transfer. Livest Sci. 2011;142(1):59–62. ↩︎
5. L.R Mundell, J.R. Jaeger, J.W. Waggoner, J.S. Stevenson, D.M. Grieger, L.A. Pacheco, J.W.Bolte, N.A. Aubel, G.J. Eckerle, M.J Macek, S.M. Ensley, L.J. Havenga, K.C. Olsen (2012) Effects of prepartum and postpartum injections of trace minerals on performance of beef cows and calves grazing native range. The Professional Animal Scientist 28, 82-88 ↩︎
6. Ibid. ↩︎
7. Ibid. ↩︎
8. Funston RN, Musgrave J a., Meyer TL, Larson DM. Effect of calving distribution on beef cattle progeny performance. J. Anim Sci. 2012;90(13):5118–21. ↩︎
9. Ibid. ↩︎
10. Sales J, Pereira R, Bicalho R, Baruselli P. Effect of injectable copper, selenium, zinc and manganese on the pregnancy rate of crossbred heifers (Bos indicus x Bos taurus) synchronized for timed embryo transfer. Livest Sci. 2011;142(1):59–62. ↩︎
11. Machado VS, Bicalho MLS, Pereira RV, Caixeta LS, Knauer WA, Gilbert R, Bicalho R. Effect of an injectable trace mineral supplement containing selenium, copper, zinc and manganese on the health and production of lactating Holstein cows. Vet J.2013 Aug;197(2):451-6 ↩︎
12. Guadagnini M, O’Neill pF, Oxtoby T, O’Rourke D (2023) Role of strategic trace mineral supplementation on udder health and its economic implications in a UK dairy herd. Oral communication at XXV Congreso Internacional ANEMBE de medicina bovina, Leon, Spain. 24th-26th May 2023. ↩︎
13. Machado VS, Bicalho MLS, Pereira RV, Caixeta LS, Knauer WA, Gilbert R, Bicalho R. Effect of an injectable trace mineral supplement containing selenium, copper, zinc and manganese on the health and production of lactating Holstein cows. Vet J.2013 Aug;197(2):451-6 ↩︎
14. Guadagnini M, O’Neill pF, Oxtoby T, O’Rourke D (2023) Role of strategic trace mineral supplementation on udder health and its economic implications in a UK dairy herd. Oral communication at XXV Congreso Internacional ANEMBE de medicina bovina, Leon, Spain. 24th-26th May 202 ↩︎
15. Preedy GW, Olson KC, Stevenson JS, Weaber RL, Hill SL. Injectable trace mineral supplementation improves sperm motility and morphology of young beef bulls. Prof. Anim. Sci. 2018 Feb 1:34(1): 1-9 ↩︎