Abstract #301

# 301
The effects of different feeding practices on heifer growth and reproduction at five California dairies using single-time-point measurements.
David D. Myers*1, Heidi A. Rossow1, 1University of California, Davis, Davis, CA.

Feeding for increased growth improves heifer reproductive efficiency and shortens the unproductive period from birth to calving, allowing producers to quickly regain costs associated with raising heifers. The objective of this study was to compare nutrients supplied to growing heifers, heifer weights, and age at first breeding on 5 commercial dairies and form a ranking system for evaluating and improving heifer-raising programs. A rank of 1 indicated the dairy fed DM greater than 10 kg/heifer/d, CP greater than 1.2 kg/heifer/d, and NEg greater than 0.9 Mcal/kg DM, had heifer weights greater than 600 kg at 20–24 mo, and early breeding, i.e., less than 410 d. Each subsequent rank indicated reduced performance from the first in at least one area with the lowest rank being 5. To determine the impact of nutrient supply on heifer growth and reproduction, TMR samples for each heifer diet were collected weekly for 4 wk at each dairy. Heifer weights were estimated using a weigh tape on 10% of the heifers (n = 1747). Reproduction records for the previous year (n = 4809) were collected from DairyComp305 (Valley Ag. Software, Tulare, CA). Least squares means for DM, CP, NEg, weight, and age at first breeding were compared among dairies using the PROC GLM procedure of SAS (v. 9.4, 2014). Dairy E ranked 1 overall due to a NEg of 0.96 Mcal/kg DM (P ≤ 0.05), weight at 20–24 mo of 602 kg (P ≤ 0.05), and low SD in age at first breeding (411 ± 16.7 d; P ≤ 0.05). The other dairies were ranked as follows: dairy D (1.1 Mcal/kg DM, 599 kg, 418 ± 16.9 d, respectively) was ranked second, dairy C (0.84 Mcal/kg DM, 649 kg, 420 ± 27.5 d, respectively) was ranked third, dairy B (0.87 Mcal/kg DM, 589 kg 399 ± 48.3 d, respectively) was ranked fourth, and dairy A (0.82 Mcal/kg DM, 579 kg, 412 ± 17.0 d, respectively) was ranked fifth. Dairies that fed more NEg in the 7 to 12 mo age range had greater heifer weights at parturition and earlier calving compared with the other dairies in this study. These results show that single-time point measurements can be used to create a benchmarking system to evaluate and improve heifer-raising programs in nutrients supplied, growth, and reproduction.

Key Words: heifer, benchmarking, nutrition