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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #90678
Title: CAN BALANCING BIRTH WEIGHT AND GROWTH IMPROVE CALVING EASE?

Author
item Macneil, Michael
item SNELLING, W - BEEFBOOSTER MANAGE. LTD.
item URICK, J - RETIRED USDA-ARS

Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Other
Publication Acceptance Date: 8/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mass selection by independent culling levels (YB subline) for below average birth weight (BWT) and high yearling weight (YWT) was compared with single-trait mass selection (YW subline) for high YWT in the inbred population of Line 1 Hereford cattle at Miles City, Montana. There was 4.2 generations of selection in both YB and YW. Heritability estimates for the base population derived from multiple-trait REML were .28 and .31 for direct effects and .16 and .06 for maternal effects on BWT and YWT, respectively. Mid-parent cumulative selection differentials for BWT of YB and YW diverged (-2.9 vs 8.2 kg, respectively), as did the associated genetic trends for direct effects (-.014 kg/yr vs .105 kg/yr, respectively). Mid-parent cumulative selection differential for YWT of YB (102.1 kg) was 64% of that attained in YW (160.7 kg). Likewise, response in YWT of YB (.91 kg/yr) was 61% of response attained in YW (1.5 kg/yr). For both BWT and YWT, maternal genetic trends were similar across selection lines. The genetic potential of YB led to consistently less frequent assistance at parturition than in YW.

Technical Abstract: Mass selection by independent culling levels (YB subline) for below average birth weight (BWT) and high yearling weight (YWT) was compared with single-trait mass selection (YW subline) for high YWT in the inbred population of Line 1 Hereford cattle at Miles City, Montana. There was 4.2 generations of selection in both YB and YW. Heritability estimates for the base population derived from multiple-trait REML were .28 and .31 for direct effects and .16 and .06 for maternal effects on BWT and YWT, respectively. Mid-parent cumulative selection differentials for BWT of YB and YW diverged (-2.9 vs 8.2 kg, respectively), as did the associated genetic trends for direct effects (-.014 kg/yr vs .105 kg/yr, respectively). Mid-parent cumulative selection differential for YWT of YB (102.1 kg) was 64% of that attained in YW (160.7 kg). Likewise, response in YWT of YB (.91 kg/yr) was 61% of response attained in YW (1.5 kg/yr). For both BWT and YWT, maternal genetic trends were similar across selection lines. The genetic potential of YB led to consistently less frequent assistance at parturition than in YW.