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Phenotypic correlation of residual feed intake in mid and early lactation in Holstein cows.

M. M. Nehme

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06-23-2020

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Abstract:

T109
Phenotypic correlation of residual feed intake in mid and early lactation in Holstein cows.
M. M. Nehme*, F. Pe�agaricano, J. E. P. Santos. University of Florida Gainesville, FL.

Objectives were to establish phenotypic correlation between residual DMI (RFI) in mid lactation (ML, wk 9 to 13 postpartum) with RFI in early lactation (EL, wk 1 to 5 postpartum) in Holstein cows and determine associations between RFI in ML and performance in EL. Data from 155 primiparous and 245 multiparous enrolled in 4 experiments were collected. Cows were fed diets as TMR and amounts of DM offered and refused were measured daily from 1 to 91 DIM. Milk yield and BW were measured daily and milk sampled from 2 consecutive milkings twice a week was analyzed for fat, protein and lactose. Energy-corrected milk (ECM) and net energy secreted (NES) in milk were calculated from yields of milk and milk components. Body condition was evaluated weekly. Metabolic BW (MBW) was calculated from BW0.75. Body energy change (BEC) was calculated from daily change in BW and the BCS using NRC (2001) equation: BEC = [2.88 + (1.036 x BCS)] � BW change. Net energy balance (NEB) was calculated from energy intake and needs for maintenance and NES. Data were analyzed with the MIXED and CORR procedures of SAS. Intake of DM was regressed as a function of NES, MBW, BEC, parity, season of calving, and treatment within experiment. The error term in the model defined RFI. Cows were ranked by RFI in ML and categorized into quartiles as Q1 (most efficient) to Q4 (least efficient) (Table 1) Performance in EL was evaluated as a function of RFI quartile in ML. The phenotypic correlation between RFI in ML and EL was 0.43 (CI = 0.34—0.50). The correlation between BEC and NEB was 0.46 (CI = 0.38—0.53). Increasing efficiency in ML resulted in a linear decrease in DMI and NEB in EL; however, ECM yield and BEC were not affected by quartile of RFI. Re-ranking in phenotypic RFI exists between mid and early lactation, but selecting for RFI in ML does not seem to negatively affect cows in EL.Table 1. Quartile of RFI in mid lactation and performance in early lactation

ItemQ1Q2Q3Q4SE
RFI, kg/d*−1.0−0.20.30.90.2
DMI, kg/d*16.016.617.518.30.3
ECM, kg/d37.337.939.038.70.8
BEC, Mcal/d−8.8−9.0−7.4−7.80.7
NEB, Mcal/d*−9.2−8.2−7.4−6.10.5
*Linear (P < 0.05).

Keywords: residual feed intake, efficiency, phenotype.

Biography: Mariana M. Nehme graduated in veterinary medicine at Federal University of Uberlandia, Brazil in 2019 and currently is a master of science student in the Department of Animal Sciences at the University of Florida, Gainesville.