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Nutrition in early lactation affects reproductive performance

With the pressure of calving and the start of a new season, in-calf rates and improving herd fertility are not topics that make it to the top of the list of priorities at this time of the year – but they should be, as many of the decisions made and actions taken at this time of year can have an effect on the long-term reproductive performance of your cows.

It has long been acknowledged that nutrition can and does influence reproductive performance and while difficult to quantify, the impact of nutrition on fertility during late gestation and early lactation is both complex and multifactorial.

In a recently published meta-analysis, a team of international researchers reviewed the results of 39 experiments with 118 different treatments, in an effort to explore the effects of different diets fed to cows in early lactation, on pregnancy to AI and calving to pregnancy interval.

Like other researchers, these authors found that energy balance was positively associated with an improved proportion of cows pregnant and a shorter calving to pregnancy interval. They noted that energy balance is determined by the difference between dietary nutrient intake (from feed) and nutrient expenditure (in the form of milk, as well as for maintenance, and growth in younger animals). If the amount of nutrient required for maintenance, growth and production exceeds the amount of nutrient consumed then body reserves are depleted. The greater the proportion of consumed nutrients which are used for milk production, the smaller the proportion of nutrients available for reproduction. Consequently, dry matter intake before and after calving is an important determinant of energy balance and subsequently reproductive performance, with improved reproductive performance correlated with higher feed intakes.

The reproductive response to dietary carbohydrates, including sugar, starch and fibre, can be variable depending on the type of carbohydrate. Clearly feeding high levels of fermentable carbohydrates such as sugar and starch can lead to acidosis, while high levels of fibre lead to a reduction in energy intake, which is undesirable. This review covered a wide range of different trial diets, allowing the authors to tease out the relationship between different dietary carbohydrate sources and reproductive performance. The starch levels of diets in this review ranged from 8.9 to 47.9 percent starch with an average starch content of 26.2 percent, while dietary sugar levels ranged from 2.1 to 13 percent with an average of 5.1 percent. Analysis of the diets and reproductive performance showed a positive association between starch intake (kg/d) with the proportion of cows pregnant, while there was a negative association between the intake of the more fermentable sugar (kg/d) and proportion of cows pregnant.

This comprehensive review confirms that management of early lactation cows and decisions made about feed quality and supply in the first few weeks after calving can influence reproductive success. Implementing feeding strategies that help to improve dry matter intake in early lactation, as well as careful selection of feedstuffs to ensure a better balance of energy and protein supply for the cow, provide an opportunity to positively influence reproductive outcomes.

Talk to your local Nutrition Specialist today to find out how they can help you increase dry matter intake in your early lactation cows.

Article supplied by Natalie Chrystal, Nutritionist.