Feed Choices Influence Conception Rates

Poor conception rates are one of the greatest areas of waste in dairy farming in New Zealand. Empty rates between 12-30% are not uncommon.

Investments in better feeding practices are essential to minimise the economic loss incurred through excess empty rates. When farming beyond the weather, good conception rates are within farm management control and are achievable through good feed choices.

Increase blood glucose levels to improve conception rates

Increasing sugar levels in the dairy diets post-calving to levels of 10-16% will increase blood glucose levels. Based on field brix sugar testing, total sugar in the pasture post-calving is often only 2-5%. Creating diets to increase sugar levels will improve both blood glucose and conception rates.1

Agri-feeds molasses – a good feed choice

The best feeds to raise blood glucose levels are molasses and starch. Early spring pasture, while low in sugar, has virtually no starch to support higher blood glucose levels. On a 100% sugar equivalency basis, feedgrade molasses costs about $550 per tonne. As such, molasses is the cheapest source of sugar energy to ‘wind the cow up’ and increase blood glucose levels.

Excess diet protein affects conception rates

High protein spring pastures are usually low in both dry matter (DM) (12%) and sugars (2-3%). The cow protein diet requirement is about 18% on a DM basis. Pasture at 35% protein will cost the cow an extra 27MJ of energy to process and excrete the surplus protein. If this energy comes from cow weight loss and not from feed, this is equivalent to losing 0.3kgMS or 0.57kg of weight loss per day.2

When blood urea nitrogen (BUN) levels rise above 200mg/L, conception rates are likely to be affected.3 Addictive use by farmers of excess urea is a key cause of high BUN levels. Excess BUN and ammonia levels in the cow are terminal to embryos. These same blood toxins may also exacerbate lameness, a key cause of increased empty rates.1

Feeding advice

Feeding 1-2kg of molasses per cow per day post-calving will raise blood sugar levels and also dilute and reduce total diet protein by 2-4%. Tapioca fed at 2kg and maize silage at 3kg per day will also help reduce protein by 2% and 4% respectively.

New Zealand molasses and fertility research

The Stratford Demonstration Farm Trial 2006 showed a 17% improvement in fertility in molasses fed cows. With replacement cows now costing up to $2000 in today’s market, this trial showed a conception rate return on investment of 120%. In addition, the trial indicated a milk response of 23.5kg or a margin over feed cost of $32 per cow or 21% return.

Feeding molasses shows great proof of performance and an excellent economic return on a molasses investment in any language! Enquire at your local rural supply store about the comprehensive range of molasses from Agri-feeds.

¹Plym Forshell, 1994. ²Quadratic model of 82 Studies, ³NRC 2001. Ferguson et al 1988.

better feeding choices can turn your empty rate around