Nutrition & Fertility

Nutrition in general and energy nutrition in particular has a major effect on fertility. Cows in too much of a negative energy balance in early lactation tend to be difficult to get back in calf. This results both from a delay in the resumption of normal oestrus cycling and a lower conception rate. Cows that are too fat at calving encounter particular problems since their early lactation appetites tend to be poor, resulting in excessive body fat mobilisation which can result in ketosis or fatty liver syndrome. For optimum fertility, cows should calve down at Body Condition Score 2.75-3.0 and lose no more than half a Condition Score by service.

Feeding for Fertility

Increasing starch and reducing fat supply, for example, has been shown to increase bulling activity and insulin levels. Because higher insulin levels have a detrimental effect on embryo quality, however, cows subsequently need diets higher in saturated fat to stimulate progesterone production and lower in starch to minimise insulin production. This implies that feeding for fertility in this way is likely to require more complex grouping of stock than may be practicable for many. 

Excess protein is not, itself, a major cause of poor fertility, however, almost always exacerbates energy deficits as additional energy is required to get rid of it. There is some evidence that high blood ammonia reduces early embryonic growth which could lead to pregnancies being lost within the first 10 days.

If fertility problems persist despite cows being in the correct body condition and rations being correctly balanced for energy and protein, it is advisable to check the mineral and vitamin status of both animals and rations. In view of the many interactions between different minerals it is vital to analyse the mineral status of forages and seek specialist advice before undertaking additional supplementation.