North Carolina State University
Animal Science Departmental Report
2004-2005
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Genetic Improvement of Reproductive Traits for Duroc Sows Differing in Post Weaning Performance

M. T. See, K. J. Stalder1, T. J. Baas1and J. W. Mabry1

1Department of Animal Science, Iowa State University, Ames, IA  50011

Introduction

Reproductive traits recorded in the U.S. Duroc population include number of pigs born alive (NBA), litter weaning weight (LWT), and number of pigs weaned (NW). Genetic evaluation procedures are used in the Duroc breed to produce breeding value (BV) estimates for a variety of traits. BV estimates rank animals according to their genetic merit as parents. Selection for improved leanness and muscling has occurred to meet consumer demand for healthy pork products. Selection for these traits has likely impacted the rate of reproductive trait BV improvement.

 

Materials and Methods

Genetic trends were evaluated using data from participating breeders over a 10-year (1993-2002).  The model used to estimate NBA, NW, and LWT BVs included the fixed effect of contemporary group (CG) and the random genetic effect of animal. Permanent environment and mate within CG were included as uncorrelated random effects. Data were adjusted prior to analyses using breed-specific adjustment factors (1). Components of (co)variance used for BV estimation were specific to the Duroc breed (2).  Only females (n=12,165) having a reproductive record and a post-weaning performance record with both backfat and loin muscle area were used in the analyses. Records were divided into four categories based on population mean and standard deviation for adjusted backfat (ABF), adjusted loin muscle area (ALMA), and adjusted days to 114 kg (AD114) (Table 1).  Genetic trends were determined within each category for NBA, LWT, and NW.

 

Results and Discussion

The mean ABF, ALMA, and AD114 were 1.47cm, 45.7 cm2, and 169.9, respectively. Over this ten-year period genetic improvement of NBA (Table 2) was greatest for females intermediate in ABF.  However, the best average BV for number alive was observed for the fattest females.   Females with the least ALMA and those that were faster growing showed greater genetic improvement for NBA.

Genetic improvement in NW (Table 3) was greatest for females with the most ABF and least ALMA.

Genetic improvement in LWT (Table 4) was greatest for females intermediate in ABF and ALMA.  Faster growing females showed greater genetic improvement for LWT.

 

Conclusion

Selection for improved leanness and muscling has occurred and has impacted the rate of reproductive trait BV improvement. These results suggest that genetic improvement in litter size was greatest for females that were intermediate in backfat depth, possessed the smallest loin muscle area and were the fastest growing. Genetic improvement for number weaned was greatest for females with the most backfat and least loin muscle area. Genetic improvement in litter weaning weight was greatest for females intermediate in backfat and loin muscle area, and faster growth rate.

 

References

Culbertson, M. S. et al. (1998) J. Anim. Sci. 75:2362-2367.

Mabry, J. W.  (1998) Seedstock Edge 5:45-49 (No. 4).

Table 1.  Mean ABF, ALMA and AD114 for each of the four categories.

Trait

Cat. 1

Cat. 2

Cat. 3

Cat. 4

ABF, cm

1.04

1.31

1.61

2.01

ALMA, cm2

38.5

43.5

47.9

53.6

AD114

150.l

162.7

176.4

195.0

 

 

 

 

 

Table 2. Genetic improvement in NBA.

Trait

Cat. 1

Cat. 2

Cat. 3

Cat. 4

ABF

-0.04

0.08

0.09

0.04

ALMA

0.12

0.08

0.03

-0.08

AD114

0.22

0.18

0.02

0.07

 

Table 3. Genetic improvement in NW.

Trait

Cat. 1

Cat. 2

Cat. 3

Cat. 4

ABF

0.05

0.06

0.06

0.09

ALMA

0.11

0.06

0.04

-0.06

AD114

0.08

0.06

0.06

0.08

 

Table 4. Genetic improvement in LWT, kg.

Trait

Cat. 1

Cat. 2

Cat. 3

Cat. 4

ABF

0.93

1.71

1.46

1.13

ALMA

0.42

1.51

1.54

0.81

AD114

1.45

1.10

0.97

0.88