Relationship of somatic cell score with fertility measures Poster 1390 ADSA 2001, Indiannapolis - PowerPoint PPT Presentation

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Relationship of somatic cell score with fertility measures Poster 1390 ADSA 2001, Indiannapolis

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Poster 1390. ADSA 2001, Indiannapolis. R. H. Miller1, J. S. ... Poster. 1390 ... Poster. 1390. ADSA. 2001. Analysis. Model to relate SCS on test-day prior to ... – PowerPoint PPT presentation

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Title: Relationship of somatic cell score with fertility measures Poster 1390 ADSA 2001, Indiannapolis


1
Relationship of somatic cell score with fertility
measuresPoster 1390ADSA 2001, Indiannapolis
  • R. H. Miller1, J. S. Clay2,
  • and H. D. Norman1
  • 1 Animal Improvement Programs Laboratory, USDA,
    Beltsville, MD
  • 2 Dairy Records Management Systems, Raleigh, NC
  • dnorman_at_aipl.arsusda.gov

2
Abstract
  • Dairy Herd Improvement (DHI) data from 284,450
    Holstein and Jersey cows in 37 states were used
    to examine relationship of test-day somatic cell
    score (SCS), herd, calving year, parity,
    lactation stage, and calving ease score with
    fertility measures nonreturn rate (NRR) by 70 d
    after first service, days to first service (D1),
    and days open (DO). Factors other than SCS were
    examined to ensure estimated SCS effect was
    independent of other effects. NRR were highest
    during April and May and lowest during June.
    Parity had a large effect on NRR, which was 6 to
    7 higher for first parity than for sixth and
    later. Effect of lactation stage at first service
    on NRR was large NRR increased by 8 to 13 from
    early to late lactation. Effect of calving ease
    score on NRR also was large a 7 decline from
    score 1 to 5. A small linear regression was found
    for NRR on preceding test-day SCS for Holsteins,
    but this relationship was not significant for
    Jerseys. The magnitude of SCS effect on fertility
    traits does not warrant postponing first service
    when SCS is high.

3
Introduction
  • Mastitis infections thought to affect
    reproduction negatively.
  • Practical importance of mastitis in open cows
    lies in possible delay of breeding until clinical
    symptoms disappear.
  • Confirmation of a relationship between SCS and
    reproduction would justify increasing economic
    weight on mastitis resistance (SCS) because
    reproduction has no direct economic weight in
    current selection indexes.

4
Objectives
  • Determine magnitude of possible effect of
    elevated SCS prior to first service on NRR, D1,
    and DO .
  • Examine effect of herd, calving year, month,
    parity, lactation stage, and calving ease score
    on NRR, D1, and DO.

5
Data
  • Records from Dairy Records Management Systems
    (Raleigh, NC) for 2.7 million Jersey and Holstein
    lactations from 37 states and calving years
    1995-98.
  • Two data subsets for Holsteins, each with 10 of
    original data.
  • Records included SCS for first 3 test days
    service sire, cow, and parent identification DIM
    at first service and parity.
  • Calving ease scores available for 8 of original
    Holstein data.

6
Data
  • Records limited to AI first services, cows bred
    at 15-365 DIM, lt150 DIM on third test day, daily
    milk yield of 4.5-109 kg, test-day component
    percentages of 2.0-8.0, and component sampling
    for at least 2 of first 3 test days.
  • Record excluded if gt56 d between last test day
    and first service, virgin heifer or cow left herd
    within 70 d after first service, or breeding was
    second within 4 d.

7
Data
  • Records with DO of gt329 set to 329 d.
  • First breeding successful if cow not rebred
    within 70 d.
  • Herds required to have gt9 AI matings annually and
    mean NRR of ?62.5.

8
Analysis
  • Model to relate SCS on test-day prior to first
    service to NRR
  • y h p s m c t b(SCS) e
  • where y NRR, h random herd effect, p fixed
    effect of parity (1, 2, ..., ?6), s fixed
    effect of lactation stage (DIM lt50, 50-59, ...,
    130-139, gt139), m fixed effect of calendar
    month, c fixed effect of calving year, t
    fixed effect of interval from prior test day to
    first service, b regression coefficient, and e
    random residual effect.

9
Analysis
  • Difference between effect of elevated SCS just
    prior to first service and several weeks prior
    determined using 6 interval classes (lt8, 8-14,
    15-21, 22-28, 29-42, 43-56 d).
  • Similar models for D1 and DO.
  • For Holstein cows with calving ease data,
    additional analyses of NRR, D1, and DO.

10
Results
Coefficients for regression of NRR on test-day SCS prior to first service Coefficients for regression of NRR on test-day SCS prior to first service Coefficients for regression of NRR on test-day SCS prior to first service Coefficients for regression of NRR on test-day SCS prior to first service
Test day to service (d) Holstein subset 1 Holstein subset 2 Jersey
1-7 -0.00345 -0.00518 0.00054
8-14 -0.00369 -0.00473 -0.00130
15-21 -0.00505 -0.00130 -0.00016
22-28 -0.00102 0.00010 -0.00132
29-42 -0.00464 -0.00205 0.00360
43-56 0.00218 -0.00201 0.00127
F-test 4.03 3.35 0.47
P ? 0.01
  • Large effect by parity decrease of 6-7 in NRR
    from first parity to sixth and later.

11
Results
  • Seasonal effect of first service

12
Results
  • Large effect by lactation stage increase of
    8-13 in NRR from early to late lactation.
  • Significant effect by calving ease score decline
    in NRR of 7 from score 1 (easy calving) to score
    5 (difficult calving).
  • Regression of D1 on SCS significant and quadratic
    for Holsteins and Jerseys.
  • Regression of DO on SCS significant for Holsteins.

13
Conclusions
  • Significant (but very small) linear regression of
    NRR on test-day SCS prior to first service for
    Holsteins, but no relationship for Jerseys.
  • Possible causes for seasonal effect on NRR
    temperature, humidity, pasturing patterns,
    competition from crop management activities.
  • Delaying breeding solely because of high SCS on
    prior test day unwarranted.
  • Additional emphasis on mastitis control and a
    slight increase in economic weight for SCS in
    genetic selection warranted.
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