Effect of dietary concentration of crude protein and Synovex-C on skeletalgrowth of dairy heifers

Eighteen prepubertal Israeli-Holstein heifers were used in an experiment to study the effects of protein supplementation and implantation of Synovex-C on body weight gain (BWG), skeletal size and age at puberty. Heifers were allocated to three treatment groups as follows: 1. heifers received a diet that was formulated according to NRC (1989; Control) recommendations. 2. he ifers received the same diet fed to heifers on treatment 1 except that the diet was supplemented with 3.3% maize gluten meal (MGM) during the first 6 months and with 2.5% MGM during the next 3 months 3. heifers received the s ame diet fed to heifers on treatment 2 and were implanted with Synovex-C. S upplementation of MGM to the diet enhanced BWG during the first 183 d of th e experiment. The implantation of Synovex-C enhanced BWG only during the fi rst 92 d of the experiment. From d 93 to 281, BWG of heifers on treatment 3 was reduced, and, by the end of the experiment, the BW of these heifers te nded to be lower than of heifers on treatment 2. Supplementation of MGM to the diet enhanced growth rates of the wither and hip during the first 281 o f the experiment However, implantation of Synovex-C eliminated the effect o f supplemented MGM, and, towards:the end of the experiment, withers and hip heights of heifers on treatment 3 were lower than those of heifers on trea tment 1. Implantation of Synovex-C was associated with increased serum IGF- 1 during the first 150 d of the experiment and with reduced age and wither height at puberty.