Agri Kultuur December / Desember 2018 - Page 24

Key performance indicators for dairy farmers Dr Carel Muller Research Associate, Faculty of Animal Sciences, University of Stellenbosch M ilk prices for dairy farmers are affected by supply and demand. Farmers have, for except, the volume and quality of milk being produced, generally little effect on milk prices. The profitability of a dairy herd is affected mostly by the milk yield income (+90% of farm income) and the production cost of milk. The feeding cost of all the animals in a dairy herd constitutes the largest part of the production cost. By feeding more concentrates to cows, milk yield increases although feed cost also increases. This increase in milk yield may result in a lower income because of the law of diminishing returns. The profitability of a dairy herd can also be improved by reducing the production cost of milk. This can be done in several ways. This requires applying specific management actions as suggested by key performance indicators. Some of these indicators are discussed in this paper. Number of cows in milk The number of cows in milk determines the total milk yield of a dairy herd. A dairy herd consists of first lactation cows and older cows. The milk yield of cows increases from first to fifth lactation, therefore most cows in the herd should be older cows (in second plus lactation). The genetic merit of first lactation cows affects the herd’s future genetic merit. At least 82% of all the cows in the herd should be in milk. This percentage increases when cows are longer (more days) in milk, i.e. when herd average days-in-milk (DIM) increases. The growth of a dairy herd can be observed by comparing the current number of cows AgriKultuur |AgriCulture in milk to the number the previous year(s). A trendline can be fitted using records of at least three (or more) previous years. A dairy herd should increase in numbers from year to year. When this is not the case, two major problems may be the cause, i.e. the culling rate among cows is high or the survival rate of heifers from birth to first calving is low. From a dairy herd of 100 cows, at least 85% should calve down every year when reproduction management is good. The bull: heifer ratio is usually 50:50 unless sexed semen is being used. Based on this ratio, 42 heifers are available for rearing to replace cows. If 85% of heifers survive to first calving, it means that 36 first lactation cows should enter the dairy herd. At a culling rate of 25% among cows, there are 11 surplus first lactation cows; however, when the culling rate is higher, the number of surplus cows is less. At a lower heifer survival rate to first calving, fewer heifers are available to rear to first lactation. The survival rate of heifers from birth to first calving is determined by the comparing the number of heifers born in a specific year to the number of these heifers calving down for the first time. When 100 heifers are born in a specific year and 80 heifers eventually calve down for the first time, the heifer survival rate to first calving is 80%. It is also important to know at which age heifers are lost from the herd as this affects the mortality cost of heifers. A higher age at culling increases the mortality cost of heifers, mostly due to feeding 24