Traditionally, heifer growth has been compared to breed standards to determine 'normal' progress. However, this type of comparison is not useful if the group of heifers you want to monitor happen to be genetically programmed to be larger or smaller than breed average or if there is considerable variation in the genetics within a group of heifers. Crossbred heifers can be a bit of a challenge to benchmark as well, because they fall between the standards for the breeds of their sires and dams. We also know that certain physiological changes (such as the start of puberty) happen not because a heifer reaches a particular weight, but because she has matured to a certain proportion of her final mature size and body composition.
For these reasons, recommendations for heifer growth benchmarks based on the mature size of the animal were adopted in the 2001 Nutrient Requirements of Dairy Cattle. If we know the mature size of a heifer and her current size, it is a relatively simple matter to figure out what growth rate we need to achieve to move from the current size to the mature size, or to benchmark times in between, such as breeding. We have developed a new growth tracking spreadsheet that automates these calculations and can generate a customized growth curve for an individual herd based on that herd's goal for age at first calving and the mature size of animals in the herd. Using this tool, you will be able to tell at every step of the way whether heifers are on track to calve at the right size and age, eliminating the delay that comes with not measuring heifer performance until first calving.
The spreadsheet assumes a target body weight of 55% of mature weight at first conception and 85% of mature weight after first calving, as cited in the 2001 Dairy NRC. Height targets are assumed to be 55% of mature height at birth and 96% of mature height at first calving; 50% of height growth from birth to calving is assumed to occur between birth and 6 months with an additional 25% between 6 and 12 months and the final 25% between 12 months and calving. These targets were derived from a comparison of heifer growth data from all breeds to mature heights calculated by assuming mature body weight and using the relationship between withers height and body weight determined by Heinrichs et al., 1992 (Journal of Dairy Science 75:3576-3581) and from Kertz et al., 1998 (Journal of Dairy Science 81:1479-1482). Withers and hip height are assumed to change at the same rate throughout the growing period, meaning either one can be used to monitor growth as long as the same measurement is used for heifers and mature cows. Mature size of cows can be entered as a herd average or individually for each heifer's dam.
Modified February 20, 2015 to give users greater flexibility for the pre-weaning average daily gain (ADG) calculation. Goals for heifer height were updated August 27, 2013. First published in 2013.
Customized Growth Chart Spreadsheets