Neil Broadwater, Regional Extension Educator-Dairy

June 17, 2006

"Heifers should be charted at least 5 times before they reach two years of age. This can be done at times of deworming, vaccinations, breeding, or pregnancy checks, so it is not an additional chore" says Tom Bailey and Julia Murphy, Extension Specialists at the Virginia-Maryland Regional College of Veterinary Medicine at Virginia Tech. The cost of raising replacement heifers is the second highest input cost on the dairy, next to feed. Efficiencies in the replacement heifer area have significant impact on overall farm profitability. One of the primary influences in the cost of raising replacements is the average age at first calving. Researchers Heinrichs and Lammers of Penn State indicate that "raising dairy heifers to an adequate size and with an age at first freshening between 22 to 24 months can optimize profitable milk production."

Dairy producers are very good about monitoring milk production levels on their farm. They have records for the number of inseminations and days open. Many producers use a monthly bulk tank sample for somatic cell count monitoring and to determine the types of pathogens present. When feeding calves, the calf raiser is checking for signs of problems including coughing, scouring, and not eating or drinking as they should.

Yes, there is a lot of monitoring taking place on the dairy farm. Monitoring animals and management activities everyday is important to head off what could be costly situations. But, how often is the growth and development of the dairy replacements monitored? Whole groups of animals that are undersized, underweight or overweight indicate improper feeding or management. Monitoring heifer growth and development affords the heifer raiser the opportunity to identify potential problems and make changes in management based on information derived from actual measurements. Heifers should be first weighed or girth taped at 2.5 to 3 months, perhaps when calves are removed from the hutches. The second measurement could be done as the calves are vaccinated for calf-hood diseases at about 5 to 6 months of age. The next measurement can be at 9 to 12 months of age to evaluate the critical period up to puberty, when calf development is so important for udder growth. A fourth and fifth measurement can be taken during her second year of life during pregnancy check and at calving to ensure heifer growth is adequate and to create a data base for future reference to help with management decisions.

Dairy heifers at the Southern Research and Outreach Center (SROC) at Waseca come from three commercial dairy operations with Holstein cattle and are on research trials from 1 day of age up to approximately 220 days of age. Data being collected include serum protein levels, hip height, weight, and average daily gains. The data show variation among individual animals, some greater than others. For example, data collected on 316 calves born from April 10, 2004 thru October 24, 2005 had an average daily gain ranging from 1.34 to 2.38 pounds per day over the approximately 200 days at SROC. Hip heights at approximately 200 days ranged from 41 to 48.75 inches and body weights from 343 to 598 pounds. Some animals where pre-fresh data has been gathered reached a hip height of 56" with weight ranges from 1208 to 1452 pounds at anywhere between 21 to 24 months of age. The results show there can be considerable variation in growth and performance among animals. This variation can be partially related to calf birth weight, genetics and pre-weaning health status.

On many dairy farms, heifer management still remains a day-to-day low priority, since heifers are in a non-productive state and are thought of as an additional chore to maintain. Producers and dairy advisors can see seriously underconditioned or overconditioned heifers. But, 'eye-balling' them from time to time is not monitoring the dairy replacement's growth and development.

Generally, most people use breed based heifer growth, breeding weight and calving weight guidelines to have some base targets to obtain and assess growth of dairy heifers, such as in Table 1.

Pat Hoffman of Wisconsin indicates a concern with using breed based growth charts because an individual heifer's growth or body weight may vary from breed standards because the individual heifer is simply genetically large or small. He states that, "genetic variance for size within a breed can be as great as between breeds." There is thought among some dairy researchers that heifer growth or body weight should be expressed as a function of mature body weight. As a result, Table 2 was developed and fits all breeds reasonable well:

Body condition scoring is also a useful tool in determining how heifers are growing and to ensure adequate skeletal development (height) and body tissue mass. They should have a body condition score of 3.25 to a 3.5 (5-point scale) at 24 months of age.

In summary, the goal of monitoring calves and heifers is to understand and then reduce variance among heifer groups. It provides the opportunity to identify potential problems and make changes in management based on information derived from actual measurements. This management practice is one of the keys in a successful dairy heifer management program.

Further information on dairy raising calves and heifers is available on the Extension Dairy Team website at www.extension.umn.edu/dairy/management/calves.htm.