Bovine hair as an indicator of calorie-protein status.

Hair samples from beef cattle were examined to determine their response to feeding varying levels of protein and energy. Blood urea nitrogen (BUN) and nitrogen balance tests were also performed to provide a reference for comparison. Twenty-four weanling calves each weighing approximately 200 kg were equally divided into four groups and were fed the following percentages of the N.R.C. recommendations for crude protein with energy to give the indicated predicted gain: high protein-high energy (HP-HE) group -111%, 1.0 kg/day; high protein-low energy (HP-LE) group -102%, .2 kg/day; low protein-high energy (LP-HE) group -65%, .8 kg/day; low protein-low energy (LP-LE) group -45%, .2 kg/day, respectively. After 60 days all groups received the HP-HE ration for a 30day repletion period. Hair samples were taken from the back and stomach regions on day 1 and every 15 days thereafter until the conclusion of the experiment on day 90. Several parts of the root and shaft were measured and evaluated, including percent of the hairs in the anagen (active) phase, percent of the bulbs in atrophy, shaft diameter, bulb diameter and bulb length. Of all the hair parameters evaluated in this study, percent of the bulbs in atrophy was the only one effective in diagnosing a protein or energy deficiency. Differences among groups (P<~.O1) found on day 15 remained through day 60. As energy and/or nitrogen intake decreased, percent of the bulbs in atrophy increased (P<.O01). Average daily gain, nitrogen balance and BUN results reflected the level of protein and energy intake. (