References to 'private nutritionists' usually belong in gossip magazines but it's not just Hollywood celebrities who have them.

Cows need a healthy and balanced diet in order to produce milk, so dairy farmers work with nutritionists to create special diet plans for them. When designing a diet, the nutritionist takes into account the age and weight of the cows and how much milk they are likely to produce. The diet will provide a nutritious balance of energy, protein and vitamins and minerals.

Cow nutritionist Tim Davies says: "The diet has to be balanced and supply all the energy, protein, starch and sugar that the cow needs. If farmers achieve that, cow health and welfare improves and the cow may also produce more milk."

Hear more from Tim in our nutrition video.