PSVIII-25 Effect of rate of weight gain and expected progeny difference (EPD) of the sire on puberty of crossbreed heifers (Angus x Nellore) weaned early

Abstract

Abstract This study evaluated whether the rate of weight gain (RWG) on pre-puberty and the Expected Progeny Difference (EPD) of the sire increases puberty rate in crossed beef heifers. Sixty Angus x Nellore heifers weaned early (102±4.3 d of age; 103±4.7 kg of BW) were used in a 2x2 factorial treatment design. Factor 1 was the RWG in period 1 (3rd to 7th month of age): High ADG (0.95 kg), with DMI ad libitum (HG) or Medium ADG (0.70 kg), with DMI of 1.5% of BW (MG); the diet was the same in different amount (CP 19%; NDF 21%; TDN 79%). In period 2 (7th month of age to puberty), all heifers were fed ad libitum (CP 16%; NDF 27%; TDN 78%). Factor 2 was the sire’s EPD for sexual precocity: Positive EPD (PE) or Negative EPD (NE). Puberty was considered when corpus luteum was identified by the weekly ultrasonography examination. Statistical analysis was performed using MIXED and GLIMMIX procedures of SAS 9.3. There was no interaction between factors. Considering the RWG (HG vs MG), there was no effect on puberty rate (77.5 vs 69.0 %; P = 0.36), BW (318.00±9.87 vs 318.84±10.49 kg; P = 0.93), age (332.04±11.99 vs 343.66±12.74 d; P = 0.36) and BCS at puberty (7.48±0.22 vs 7.28±0.24; P = 0.38). Considering the EPD (PE vs NE), there was effect on puberty rate (87.0 vs 59.5 %; P = 0.03) and BW at puberty (337.85±9.22 vs 299.00±11.14 kg; P = 0.0005). The EPD did not affect age (346.73±11.20 vs 328.98±13.52 d; P = 0.16) and BCS at puberty (7.38±0.21 vs 7.38±0.25; P = 0.97). In conclusion, the RWG from 3rd to 7th month of age did not influence puberty rate; however, the PE increased the puberty rate of Angus x Nellore heifers at 15th month of age.