Highlighted Research Results

The Effect of Dam Age on Heifer Progeny Perfomance and Longevity

Selection and development of heifers can have long-term impacts on production and profitability. Developing females to replace cull cows is costly and one of the most expensive management decisions for cow-calf producers. Several studies have examined methods to reduce heifer development costs without impairing reproductive function. Cow and calf performance data were collected from 2005 through 2017 at the University of Nebraska, Gudmundsen Sandhills Laboratory (GSL) near Whitman, NE. Cow and calf performance data were obtained from both March and May calving herds at GSL to determine the impact of dam age on subsequent heifer progeny performance and longevity. Cows (n = 1,059) utilized in this study were a Red Angus/Simmental composite and ranged from 2 to 11 yr of age. To determine the effect of dam age on subsequent heifer progeny’s growth development and reproductive efficiency, cows were also classified by age groups as young (2 to 3 yr old), moderate (4 to 6 yr old), and old (> 7 yr old).

Heifer calves born to young cows had lighter (P < 0.01, Table 1) birth BW and 205-d than heifer calves born to moderate and old cows. Although pre-weaning BW differences occurred, heifer pre-breeding BW and at time of pregnancy determination were not different (P > 0.17) among dam age groups. Female progeny born to moderate and old cows had a greater (P < 0.01) percentage reach puberty prior to breeding compared with heifers born to young cows. However, dam age did not influence (P = 0.15) heifer progeny pregnancy rates. This could be attributed to post-weaning growth, as no BW differences were observed among the groups suggesting heifer post-weaning intake and plane of nutrition impacted reproduction success. In the subsequent calving season, there were no differences (P = 0.28) among age groups for percentage of heifers who calved within first 21 d of calving. However, average number of calf crops from progeny within dam age was different among all groups (P < 0.01), with heifer progeny from young dams having more calves (3.1 ± 0.7) than moderate (2.8 ± 0.7) and old (2.2 ± 0.8).

Results from this study suggest dam age will impact heifer progeny growth and reproductive performance. Heifer progeny from moderate and older dams tended to have increased performance up to first calving. However, heifer progeny from young dams had increased calf crops and productivity compared with their older counterparts. Depending on production goals, dam age may need to be considered for selecting replacement females with the goal of increased productivity and long-term profitability.

Dam Age1
Young Moderate Old SE P-Value
Heifer BW, lb
Birth 70.4a 74.8b 72.6b 0.9 <0.01
205 d 436a 453b 451b 7 0.01
Prebreeding 609 622 618 9 0.21
Pregnancy diagnosis 816 816 805 9 0.17
Puberty, % 51.55a 69.64b 74.06b 9.7 <0.01
Pregnancy, % 80.44 84.08 85.89 2.5 0.15
Calved in first 21 d, % 73.34 77.88 78.94 3.0 0.28
Calf Crop2, n 3.1 2.8 2.2 0.7 <0.01

a,bMeans with different superscripts differ P ≤ 0.05.
1Dam age at calving: Young (2 to 3 yr of age), Moderate (4 to 6 yr), Old (≤ 7 yr)
2Number of calf crops produced with dam age groups.