Calves and Heifers Up to 4 (l) of colostrum should be fed to dairy calves within 4 hr of birth.Recent field surveys have found colostrum exceeding goals of 100,000 cfu/ml total bacteria and 10,000 cfu/ml coliform.Amount of liquid fed,along with its protein/fat/solids content,is key in determining how much calves gain and how efficiently they gain.Supplemental water is required for calves and is directly related to dry matter intake in a 4∶1 ratio.Physical form of calf starter is crucial to rumen development and function.Pelleted form is not very effective,while texturized form results in best performance.The weaning transition period is 2 wk before and 2 wk after full weaning.Too many changes at this time lead to stress and health problems,especially respiratory.The first grouping of calves post-weaning should be small (6 to 12 for 2 to 4 wk) to minimize stress,and then can be progressively increased with age/size.Dry matter intake of heifers is quite variable as shown by data from 2001 Dairy NRC DMI predictive equation.Dry matter intakefor heifers decreases as ％ of body weight with increasing size.Forage quality is the major factor in dry matter intake,digestibility,and daily gain.Height establishes frame for growth with 50％ occurring in first 6 mo of age,25％ in following 6 mo,and only 25％ over last 12 mo of age before first calving at 24 mo of age.Height increase is not compensatory like weight gain can be.Body weight gain objective after weaning is 0.8 t0 0.9 kg/d for larger dairy breeds.Adipose ceUs increase first by hyperplasia and later by hypertrophy.Thus,early excess fattening should be avoided as itcan lead to later issues and transition cow problems.Most efficient nutrient conversion occurs at youngest age and smaller body weight.While feed costs per kg for calves are greater,feed cost per kg gain may be greater later due to increased maintenance needs and lower feed conversions as body weight increases.Heifer growth economics are in Wisconsin datahttp://www.uwex.edu/ces/heifermgmt/rearingcost.cfm.Subsequent milk production response has been found to be directly related to first lactation post calving body weight and to pre-weaned daily gain during the calf phase.
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