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High-performing farms exploit reproductive potential of high and low prolific sows better than low-performing farms

Porcine Health Management20184:15

https://doi.org/10.1186/s40813-018-0091-8

  • Received: 12 December 2017
  • Accepted: 14 June 2018
  • Published:

Abstract

Background

Our objective was to examine the impact of farm effects and sow potential on various aspects of sow performance. We examined the interaction between sow prolificacy groups categorized at parity 1 and farm productivity groups for reproductive performance across parities, and lifetime performance. Data included 419,290 service records of 85,096 sows, on 98 Spanish farms, from first-service as gilts to removal, that were served between 2008 and 2013. Farms were categorized into three productivity groups based on the upper and lower 25th percentiles of the farm means of annualized lifetime piglets weaned per sow over the 6 years: high-performing (HP), intermediate-performing (IP), and low-performing (LP) farms. Also, parity 1 sows were categorized into three groups based on the upper and lower 10th percentiles of piglets born alive (PBA) as follows: 15 piglets or more (H-prolific), 8 to 14 piglets, and 7 piglets or fewer (L-prolific). The farm groups represent farm effects, whereas the sow groups represent sow potential. Linear mixed effects models were performed with factorial arrangements and repeated measures.

Results

Mean parity at removal (4.8 ± 0.01) was not associated with three farm productivity groups (P = 0.43). However, HP farms had 7.7% higher farrowing rates than LP farms (P <  0.05). As a result, H-prolific and L-prolific sows on HP farms had 29.7 and 30.7 fewer non-productive days during lifetime than the respective sows on LP farms (P <  0.05). Furthermore, the H-prolific and L-prolific sows on HP farms had 4.9 and 6.2 more annualized piglets weaned than respective H-prolific and L-prolific sows on LP farms (P <  0.05), which was achieved by giving birth to 0.8–1.0 and 1.4–1.7 more PBA per litter, respectively, than on HP farms during parities 2–6 (P <  0.05). During the first parity, HP farms had 18.8% H-prolific sows compared to 6.2% on LP farms.

Conclusion

Farm effects substantially affected lifetime performance of sows. Higher lifetime productivity of sows on HP farms was achieved by higher farrowing rate, fewer non-productive days, more PBA and more piglets weaned per sow, regardless of prolific category of the sows.

Keywords

  • Farm effect
  • High-performing farms
  • High prolific sows
  • Lifetime performance
  • Sow potential

Background

Prolificacy performance, such as the number of piglets born alive (PBA), appears to differ between individual sows due to the extent of genetic improvement and farm management [1]. Studies in Japan, Europe, and the U.S.A. have shown that the most prolific sows, categorized by PBA at parity 1, produce 0.5–1.8 more PBA from parities 2 to 6 and 1.4–26.0 more lifetime PBA than other sows [24]. However, reproductive performance varies between individual sows on a farm, and it is important to maximize the lifetime reproductive performance of all sows in order to decrease production costs and economic wastefulness on the farms [5]. Also, a study of high-performing (HP) farms in the U.S.A., categorized by herd reproductive productivity, showed that they had 9.0% higher farrowing rates, and 0.6 more PBA than ordinary farms [6]. The high productivity of HP farms is attributable to better replacement gilt development [7], better breeding management [8], more advanced technologies [9, 10] and better piglet care during lactation [11, 12]. These studies have shown that HP farms appear to exploit sows’ reproductive potential better than ordinary farms. Therefore, we have hypothesized that high prolific (H-prolific) and low prolific (L-prolific) sows on HP farms perform differently from equivalent sows on intermediate-performing (IP) or low-performing (LP) farms. It is useful for veterinarians and producers to know a quantified association between sows’ potential and farm effects for reproductive performance across parities and lifetime performance of sows. Therefore, the objective of the present study was to examine the interaction between sow prolificacy groups and farm productivity groups for reproductive performance in consecutive parities, and lifetime performance of H-prolific and L-prolific sows. The farm groups represent farm effects, whereas the sow groups represent sow potential.

Methods

Studied farms and data selection

A consultancy firm (PigCHAMP pro Europa S.L. Segovia, Spain) has annually requested all client producers to mail their data files since 1998. In 2013, 98 Spanish farms allowed their farm data to be used for research purposes. Our study database included approximately 0.5% of all Spanish pig breeding farms and approximately 4% of all gilts and sows. Spain is one of the major pig producing countries in Europe, with 19,630 breeding farms and 2,568,450 breeding pigs, in December of 2013, accounting for 20% of breeding pigs in the 28 EU countries [13].

The mean (± SEM) size of the studied farms was 699 ± 64.3 sows with a range between 81 and 3222 sows. The study herds increased in size by 14.2% over the 6 years when data were collected. These 98 farms use mechanical or natural ventilation systems in their farrowing, breeding and gestation barns. The lactation and gestation diets were formulated using cereals (barley, wheat and corn) and soybean meal. Also, all the farms use artificial insemination, with double or triple inseminations of sows during an estrous period. Replacement gilts on the 98 farms are either purchased from breeding companies or are home-produced through their internal multiplication programs. These farms’ data were also used for another study to examine risk factors associated with severe repeat-breeder sows [14].

Study design, data collection and exclusion criteria

The present study was designed as a retrospective cohort study coordinating by-parity service records and subsequent reproductive data in sows, from first-service of gilts to their removal. The data included 554,755 service records of sows served on the 98 farms from January 2008 to June 2013. Data from the PigCHAMP recording system were collected for 99,533 sows entered into the farms between 2008 and 2010. When the data were collected, 4842 (4.8%) of the sows had not yet been removed from the farms, so these records were excluded. Also, lifetime records were excluded if they met any of the following criteria (99th percentile): lifetime non-productive days of 290 days or more (949 sows); lifetime PBA of 130 piglets or more (857 sows), 104 or more lifetime piglets weaned (914 sows), and gilt records of removal at parity 0 (6875 gilts). Additional exclusions were made for no records of gilt age at first-mating (3477 gilts) or records with either less than 160 days (1435 gilts) or more than 400 days (1300 gilts; [15]) when age at first service was analyzed. Parity records of sows in parity 7 or higher were omitted for by-parity reproductive performance analyses (18,264 records), but were included in analysis of lifetime performance. Thus, the studied data for datasets 1 and 2 contained 419,290 first-served records of 85,096 sows on the 98 farms.

Datasets 1 and 2 were created for analyses of by-parity reproductive performance and lifetime performance, respectively. In Dataset 1, service records were regarded as missing records if they met any of the following criteria; more than 26 PBA (1 record), more than 26 piglets weaned (50 records), more than 35 days of weaning-to-first-mating interval (3420 records), and re-service interval of either less than 11 days or more than 150 days (401 records).

Categories and definitions

Farms were categorized into three groups based on the upper and lower 25th percentiles of the farm means of annualized lifetime piglets weaned per sow: HP farms (> 24.7 piglets), IP farms (24.7 to 21.2 piglets), and LP farms (< 21.2 piglets). Also, sows were categorized into three groups based on the upper and lower 10th percentiles of PBA at parity 1: H-prolific (15 piglets or more), I-prolific (8 to 14 piglets), and L-prolific (7 piglets or fewer) sows.

Lifetime PBA was defined as the sum of the number of PBA in a sow’s lifetime. Annualized lifetime piglets weaned per sow was defined as the lifetime number of weaned piglets divided by the sum of the reproductive herd life days × 365. Reproductive herd life days was defined as the number of days from the date that gilts were first-mated to their removal [16]. Lifetime non-productive days of a sow were defined as the number of days when the sow was neither gestating nor lactating during her reproductive herd life.

Statistical analysis

All statistical analyses were conducted using SAS version 9.3 (SAS Institute Inc., Cary, NC, U.S.A.). A chi-square test was conducted using SAS software to compare the relative frequencies (%) of sow groups in the different farm productivity groups. Two statistical models were created: Model 1 was applied to Dataset 1 with a 3 × 3 × 6 factorial arrangement design with repeated measures. The analysis was conducted using the three sow groups, three farm groups, six parity groups, and entry years as fixed effects for reproductive performance. Model 1 also examined possible 2- or 3-way interactions. Also, Model 2 was applied to Dataset 2 with a 3 × 3 factorial arrangement, with fixed effects being the three sow groups, three farm groups and entry years. Model 2 also examined possible 2-way interactions.

For continuous outcomes, linear mixed effects models were used to account for the clustering of sows within a farm (MIXED, random statement) or the correlation between repeated measures in the same sow within a farm (MIXED, repeated statement). For binary outcomes, a generalized mixed effects logistic regression model was used with a logit link function in individual parity records (for whether or not a sow farrowed, 1 or 0: farrowing rate). This model was used to account for the clustering of sows within a farm (GLIMMIX, random statement), and the correlation between repeated measures in the same female pig within a farm (GLIMMIX, random_residual_statement). Additionally, if the 3-way interactions between the sow, farm and parity groups were found significant, then we also separately examined 2-way interactions between the farm groups and parity groups for either H-prolific or L-prolific sows. Pairwise multiple comparisons were performed by using the Tukey-Kramer test. All significance levels were set at P <  0.05. Also, a random farm effect was included in all the models.

Intraclass correlation coefficients

The intraclass correlation coefficient (ICC) was calculated by the following equations to assess the variance in the reproductive performance that could be explained by the farms, and also the variance in reproductive performance across parities that could be explained by the sow effect [17],
$$ \mathrm{ICC}\ \left(\mathrm{individual}\ \mathrm{records}\ \mathrm{within}\ \mathrm{the}\ \mathrm{same}\ \mathrm{farm}\ \mathrm{but}\ \mathrm{different}\ \mathrm{sows}\right)\ \mathrm{for}\ \mathrm{continuous}\ \mathrm{outcomes}={\sigma}_v^2/\left({\sigma}_v^2+{\sigma}_{\varepsilon}^2\right), $$
$$ \mathrm{ICC}\ \left(\mathrm{individual}\ \mathrm{parity}\ \mathrm{records}\ \mathrm{within}\ \mathrm{the}\ \mathrm{same}\ \mathrm{sow}\right)\ \mathrm{for}\ \mathrm{continuous}\ \mathrm{outcomes}=\left({\sigma}_v^2+{\sigma}_u^2\right)/\left({\sigma}_v^2+{\sigma}_u^2+{\sigma}_{\varepsilon}^2\right), $$
$$ \mathrm{ICC}\ \left(\mathrm{individual}\ \mathrm{records}\ \mathrm{within}\ \mathrm{the}\ \mathrm{same}\ \mathrm{farm}\ \mathrm{but}\ \mathrm{different}\ \mathrm{sows}\right)\ \mathrm{for}\ \mathrm{binary}\ \mathrm{outcomes}={\sigma}_v^2/\left({\sigma}_v^2+{\pi}^2/3\right), $$
$$ \mathrm{ICC}\ \left(\mathrm{individual}\ \mathrm{parity}\ \mathrm{records}\ \mathrm{within}\ \mathrm{the}\ \mathrm{same}\ \mathrm{sow}\right)\ \mathrm{for}\ \mathrm{binary}\ \mathrm{outcomes}=\left({\sigma}_v^2+{\sigma}_u^2\right)/\left({\sigma}_v^2+{\sigma}_u^2+{\pi}^2/3\right), $$
in which \( {\sigma}_v^2 \) is the between-farm variance, \( {\sigma}_u^2 \) is the between-sow variance, and \( {\sigma}_{\varepsilon}^2\kern0.5em \)or π2/3 is the assumed variance at the individual record level.

Results

Descriptive statistics of lifetime performance and by-parity reproductive performance of sows are shown in Table 1. The proportions of H-, I- and L-prolific sows at parities 1 and 6 differed between the three farm groups (P <  0.05; Table 2). In parity 1, HP farms had 18.8% H-prolific sows and 9.5% L-prolific sows, whereas LP farms had 6.2% H-prolific sows and 17.6% L-prolific sows. Also, in parity 6 there were 20.9% H-prolific sows and 6.5% L-prolific sows on HP farms, compared with 5.9 and 15.4%, respectively on LP farms.
Table 1

Reproductive data for sows on 98 farms

  

Range

N

Mean ± SEM

Minimum

Maximum

Lifetime performance measurements

 Number of parity at removal

85,096

4.8 ± 0.01

1

11

 Gilt age at first-mating, days olda

78,884

251.3 ± 0.15

160

400

 Lifetime number of piglets born alive

85,096

57.3 ± 0.11

0

129

 Lifetime number of piglets weaned

85,096

49.9 ± 0.09

0

103

 Annualized lifetime piglets weaned per sow

85,096

23.9 ± 0.02

0

74c

 Lifetime non-productive days

85,096

84.8 ± 0.17

0

289

Parity performance measurements

 Parity

419,290

2.4 ± 0.01

0

6

 Number of piglets born aliveb

352,457

12.0 ± 0.01

0

26

 Number of piglets weanedb

352,408

10.5 ± 0.01

0

26

 Lactation length, daysb

348,032

23.5 ± 0.01

14

41

 Weaning-to-first-mating interval, daysb

349,038

5.9 ± 0.01

0

35

 Re-service interval, days

37,617

37.5 ± 0.14

11

150

aThe remaining records (85,096-N) were regarded as missing records

bThe remaining records (419,290-N) were regarded as missing records

cThis is a value based on the maximum number of piglets weaned by a sow in parity 1, adjusted to an annualized equivalent (some sows were culled at parity 1, meaning that there are no subsequent data for parity 2 or higher)

Table 2

By-parity relative frequencies (%) of farm groups in three sow groups categorized by piglets born alive in parity 1a

 

Sow groupsb

Chi-square test

High prolific

Intermediate prolific

Low prolific

Farm groupsc

Nd

sows, %

sows, %

sows, %

  

Parity 1

 

High-performing farms

35,274

18.8

71.7

9.5

 

Intermediate-performing farms

37,263

10.1

77.6

12.3

 

Low-performing farms

12,559

6.2

76.2

17.6

<  0.01

  

Parity 6

 

High-performing farms

11,411

20.9

72.6

6.5

 

Intermediate-performing farms

12,917

10.2

79.9

9.9

 

Low-performing farms

4372

5.9

78.7

15.4

<  0.01

aFrequencies within a row add up to 100%

bGroups based on the upper and lower 10th percentiles of piglets born alive in parity 1: High (15 piglets or more); Intermediate (8 to 14 piglets) and Low (7 piglets or fewer) prolific sows

cCategorized by farm means of the upper and lower 25th percentiles of annualized lifetime piglets weaned per sow over 6 years: High- (> 24.7 pigs); Intermediate- (24.7 to 21.2 piglets) and Low- (< 21.2 piglets) performing farms

dN means the number of sows

There were three significant main effects, namely sow groups, farm groups and parity groups with 2-way and 3-way interactions between the groups for both PBA and the number of piglets weaned (P <  0.01). Also, there were 2-way interactions between the farm groups and parity groups for PBA and the number of piglets weaned for both H-prolific and L-prolific sows in both dataset models (P <  0.01; Appendixes A and B).

Table 3 shows comparisons between the three farm groups for PBA and the number of piglets weaned at subsequent parities by H-prolific and L-prolific sows. The H-prolific sows in all farm groups had more PBA in parity 1 than in parities 2–6 (P <  0.05). In contrast, L-prolific sows had more PBA in parities 2–6 than in parity 1 (P <  0.05). At parities 2–6, H-prolific and L-prolific sows on HP farms had 0.8–1.1 and 1.4–1.7 more PBA (6–8% and 12–15% more) than the respective sow groups on LP farms (P <  0.05). Additionally, the H-prolific and L-prolific sows in all parity groups on HP farms had 1.0–1.6 and 1.4–2.3 more piglets weaned (11–17% and 13–17% more) than the respective sow groups on LP farms (P <  0.05).
Table 3

Comparisons of reproductive performance of sows during the first parity compared with the subsequent five parities in high, intermediate and low-performing farms of either high prolific or low prolific sows 1, 2

  

Subsequent parity

Farm groups3

N4

1

2

3

4

5

6

High prolific sows5

  

Piglets born alive

High-performing farms

6232

15.8 (0.10)w

13.1 (0.10)az

13.7 (0.10)ax

13.8 (0.10)ax

13.6 (0.10)ax

13.3 (0.11)ay

Intermediate-performing farms

3541

15.8 (0.08)w

12.7 (0.08)abz

13.1 (0.09)bx

13.0 (0.09)bxy

12.8 (0.09)byz

12.7 (0.10)byz

Low-performing farms

732

15.6 (0.14)w

12.3 (0.14)bx

12.7 (0.15)bx

12.8 (0.16)bx

12.5 (0.17)bx

12.3 (0.19)bx

  

Piglets weaned

High-performing farms

6232

11.2 (0.09)aw

11.3 (0.09)aw

11.2 (0.09)aw

11.1 (0.09)ax

10.9 (0.09)ax

10.9 (0.10)ax

Intermediate-performing farms

3541

10.8 (0.07)bw

10.7 (0.07)bwx

10.5 (0.07)bxy

10.4 (0.08)byz

10.4 (0.08)byz

10.2 (0.08)bz

Low-performing farms

732

10.2 (0.12)cw

9.9 (0.12)cw

9.9 (0.12)cw

9.8 (0.13)cw

9.8 (0.13)cwx

9.3 (0.15)cx

Low prolific sows5

  

Piglets born alive

High-performing farms

2924

5.0 (0.10)z

11.8 (0.10)ay

12.5 (0.10)ax

12.8 (0.11)aw

12.9 (0.11)aw

12.7 (0.13)awx

Intermediate-performing farms

4058

5.3 (0.07)y

11.0 (0.07)bx

11.6 (0.08)bw

11.8 (0.08)bw

11.7 (0.08)bw

11.8 (0.09)bw

Low-performing farms

1903

5.1 (0.10)y

10.3 (0.10)cx

11.1 (0.11)cw

11.1 (0.11)cw

11.2 (0.12)bw

11.3 (0.13)bw

  

Piglets weaned

High-performing farms

2924

10.4 (0.11)ax

11.1 (0.11)aw

11.1 (0.11)aw

11.2 (0.11)aw

11.1 (0.12)aw

11.0 (0.13)aw

Intermediate-performing farms

4058

9.4 (0.08)bx

10.3 (0.08)bw

10.3 (0.08)bw

10.2 (0.08)bw

10.2 (0.09)bw

10.2 (0.09)bw

Low-performing farms

1903

8.1 (0.11)cx

9.7 (0.11)cw

9.7 (0.11)cw

9.8 (0.12)bw

9.7 (0.12)bw

9.5 (0.13)cw

a-cDifferent superscripts within a column represent significant differences in means (P ≤ 0.03)

w-zDifferent superscripts within a row represent significant differences in means (P ≤ 0.03)

1Means and SE were estimated by mixed models

2There were no differences between the farm groups in any parity for weaning-to-first-mating interval and farrowing rate (P ≥ 0.05)

3Categorized by farm means of the upper and lower 25th percentiles of annualized lifetime piglets weaned per sow over 6 years: high- (> 24.7 piglets); intermediate- (24.7 to 21.2 piglets) and low- (< 21.2 piglets) performing farms

4N represents the initial number of sows

5Groups based on the upper and lower 10th percentiles of piglets born alive in parity 1: High (15 piglets or more) and Low (7 piglets or fewer) prolific sows

There were three significant main effects for farrowing rate, namely sow groups, farm groups and parity groups, namely sow groups, farm groups and parity groups, as well as a 2-way interaction between sow groups and parity groups (P <  0.01; Appendix C). For weaning-to-first-mating interval, there was an association with parity (P <  0.05), but not with either sow groups or farm groups (P ≥ 0.45). Additionally, there were no 2- or 3-way interactions between these three factors for weaning-to-first-mating interval (P ≥ 0.05). Appendix D shows the mean values of reproductive performance in consecutive parities of the H-prolific and L-prolific sows in the three farm productivity groups. With regard to the ICC, the random herd and sow effects explained 1.9–6.0% of the total variance for reproductive performance.

Table 4 shows comparisons between the three factors for farrowing rates and weaning-to-first-mating interval. There were no differences between any of the sow groups or between any of the farm groups for weaning-to-first-mating interval. Regarding farrowing rate, HP farms had 7.7% higher farrowing rates than LP farms, whereas H-prolific sows had 0.7% higher farrowing rates than L-prolific sows (P <  0.05). Additionally, Table 5 shows comparisons of farrowing rates between the parity groups for different sow groups. In parities 1 and 2, farrowing rates were 2.7–3.5% higher in H-prolific sows than in L-prolific sows in all the farm groups, but there were no differences between the sow groups for farrowing rates in parities 3 and 6 (P ≥ 0.05).
Table 4

Comparisons between factors for farrowing rates and for weaning-to-first-mating intervalsf

 

Farrowing rate, %

Weaning-to-first-mating interval, days

Measurements

Ng

Mean (± SE)

N

Mean (± SE)

Farm groupsh

 High-performing farms

181,358

89.3 (0.54)a

145,196

5.9 (0.16)

 Intermediate-performing farms

191,554

85.5 (0.50)b

152,492

6.1 (0.11)

 Low-performing farms

64,642

81.6 (0.83)c

51,350

6.2 (0.16)

Sow groupsi

 High prolific sows

58,327

85.8 (0.39)a

46,758

6.0 (0.09)

 Intermediate prolific sows

332,716

86.2 (0.35)a

266,291

6.0 (0.08)

 Low prolific sows

46,511

85.1 (0.41)b

35,989

6.1 (0.09)

Parity groups

 0

85,096

88.2 (0.34)a

 1

79,267

82.9 (0.45)e

77,447

7.2 (0.08)a

 2

70,061

86.4 (0.39)b

69,497

6.1 (0.08)b

 3

61,429

86.3 (0.40)bc

61,033

6.0 (0.08)c

 4

52,372

86.1 (0.41)bc

52,074

5.8 (0.08)d

 5

42,365

85.4 (0.44)cd

42,198

5.7 (0.09)e

 6

28,700

84.5 (0.50)d

28,586

5.6 (0.09)e

a-eDifferent superscripts within a column represent significant differences in means (P ≤ 0.01)

fMeans and SE were estimated by mixed models

gN represents the number of parity record

hCategorized by farm means of the upper and lower 25th percentiles of annualized lifetime piglets weaned per sow over 6 years: High- (> 24.7 piglets); Intermediate- (24.7 to 21.2 piglets) and Low- (< 21.2 piglets) performing farms

iGroups based on the upper and lower 10th percentiles of pigs born alive in parity 1: High (15 piglets or more); Intermediate (8 to 14 piglets) and Low (7 piglets or fewer) prolific sows

Table 5

Comparisons of farrowing rates (%) between the three sow groups in subsequent parities1

  

Subsequent parity

0

1

2

3

4

5

6

Sow groups2

N3

Mean (± SE), %

High prolific sows

11,152

87.9 (0.45)bv

84.3 (0.54)ay

87.3 (0.49)avw

86.7 (0.52)vwx

86.0 (0.57)wxy

84.8 (0.63)xy

83.3 (0.75)y

Intermediate prolific sows

63,824

89.2 (0.31)av

83.5 (0.43)az

87.0 (0.36)aw

86.6 (0.37)wx

86.2 (0.39)x

85.7 (0.41)xy

84.9 (0.45)y

Low prolific sows

10,120

87.4 (0.46)bv

80.8 (0.62)bx

84.6 (0.56)bw

85.6 (0.57)vw

86.1 (0.59)vw

85.6 (0.66)vw

85.3 (0.78)vw

a, bDifferent superscripts within a column represent significant differences in means (P <  0.01)

v-zDifferent superscripts within a row represent significant differences in means (P <  0.01)

1Means and SE were estimated by mixed models

2Groups based on the upper and lower 10th percentiles of piglets born alive in parity 1: High (15 piglets or more); Intermediate (8 to 14 piglets); Low (7 piglets or fewer) prolific sows

3N represents the initial number of sows

Table 6 shows comparisons of lifetime performance between the three sow groups and three farm groups. There were 2-way interactions between the sow groups and farm groups for lifetime PBA, lifetime piglets weaned and annualized lifetime piglets weaned (P <  0.05). Across the farm groups, H-prolific sows had 20.6–25.9 more lifetime PBA (45–58% more) than L-prolific sows, whereas across the sow groups HP farms had 6.1–6.7 more lifetime PBA (7–11% more) than LP farms (P <  0.05). In contrast, the differences between HP farms and LP farms for annualized lifetime piglets weaned was greater than the differences between H-prolific sows and L-prolific sows. In detail, across sow groups HP farms had 4.9–6.2 more annualized lifetime piglets weaned (23–34% more) than LP farms. Meanwhile, across farm groups H-prolific sows had 1.3–2.6 more annualized lifetime piglets weaned (5–14% more) than L-prolific sows. The largest difference was between L-prolific sows on HP farms and LP farms. Additionally, across the sow groups, HP farms had 29.7–30.7 fewer lifetime non-productive days (27–30% fewer) than LP farms, whereas across the farm groups H-prolific sows had 5.4–9.0 more lifetime non-productive days (6–12% more) than L-prolific sows.
Table 6

Comparisons of reproductive performance between three farm productivity groups and between three sow groups categorized by piglets born alive in parity 11

 

Sow groups2

High prolific sows

Intermediate prolific sows

Low prolific sows

Farm groups3

Mean (± SE)

Mean (± SE)

Mean (± SE)

 

Number of sows

High-performing farms

6624

25,318

3332

Intermediate-performing farms

3744

28,944

4575

Low-performing farms

784

9562

2213

 

Gilt age at first-mating, days old4

High-performing farms

257.7 (6.05)x

257.3 (6.04)y

256.7 (6.06)y

Intermediate-performing farms

249.7 (4.31)x

248.1 (4.28)y

247.6 (4.30)y

Low-performing farms

259.3 (6.03)x

256.5 (5.93)y

255.8 (5.96)y

 

Parity at removal4

High-performing farms

5.1 (0.12)x

5.0 (0.11)x

4.2 (0.12)y

Intermediate-performing farms

5.1 (0.09)x

5.1 (0.08)x

4.6 (0.09)y

Low-performing farms

4.9 (0.14)x

4.9 (0.11)x

4.3 (0.12)y

 

Lifetime piglets born alive

High-performing farms

70.3 (1.40)ax

61.9 (1.36)ay

44.4 (1.45)z

Intermediate-performing farms

66.4 (1.07)abx

59.3 (0.97)aby

45.8 (1.05)z

Low-performing farms

63.6 (1.71)bx

55.8 (1.36)by

41.3 (1.48)z

 

Lifetime piglets weaned

High-performing farms

56.0 (1.15)ax

54.7 (1.11)ay

45.3 (1.19)az

Intermediate-performing farms

52.1 (0.89)ax

51.2 (0.79)axy

44.7 (0.86)ay

Low-performing farms

46.8 (1.42)bx

46.5 (1.12)bxy

38.7 (1.22)by

 

Lifetime non-productive days

High-performing farms

82.1 (2.87)cx

80.2 (2.82)cy

73.1 (2.93)cz

Intermediate-performing farms

96.2 (2.13)bx

95.5 (1.99)by

90.8 (2.10)bz

Low-performing farms

111.8 (3.25)ax

109.3 (2.80)ay

103.8 (2.94)az

 

Annualized lifetime piglets weaned per sow

High-performing farms

25.8 (0.20)ax

25.8 (0.19)ax

24.5 (0.21)ay

Intermediate-performing farms

23.4 (0.16)bx

23.1 (0.14)by

21.3 (0.15)bz

Low-performing farms

20.9 (0.26)cx

20.6 (0.19)cx

18.3 (0.21)cy

a-cDifferent superscripts within a column represent significant differences in means (P <  0.01)

x-zDifferent superscripts within a row represent significant differences in means (P <  0.01)

1Means and SE were estimated by mixed models

2Groups based on the upper and lower 10th percentiles of piglets born alive in parity 1: High (15 piglets or more); Intermediate (8 to 14 piglets) and Low (7 piglets or fewer) prolific sows

3Categorized by farm means of the upper and lower 25th percentiles of annualized lifetime piglets weaned per sow over 6 years: High- (> 24.7 piglets); Intermediate- (24.7 to 21.2 piglets) and Low- (< 21.2 piglets) performing farms

4There were no two-way interactions for ages at first-mating, parity at removal or lifetime non-productive days (P ≥ 0.05)

There were significant main effects of sow groups on age at first service and the number of parity at removal (P <  0.05), but no effect of farm groups (P = 0.35 for age at first service; P = 0.44 for parity at removal). Furthermore, there were no 2-way interactions for age at first service, the number of parity at removal or lifetime non-productive days (P ≥ 0.05). For example, there were no differences between farm groups for age at first service or number of parity at culling, but H-prolific sows had 1.0–3.5 days greater age at first service and 0.5–0.9 higher number of parity at removal than L-prolific sows across the farm groups.

Discussion

Our study showed that different farm effects could alter sows’ reproductive potential across parities and lifetime performance of sows. Also, our study indicated that farm effects were greater than sow potential on farrowing rates, non-productive sow days and annualized lifetime piglets weaned, but that sow potential had a greater effect than farm effects on lifetime PBA. Additionally, the 6–15% more PBA across sow groups after parity 1 on HP farms than on LP farms indicates that PBA was not only affected by sow potential, but also by farm effects. In particular, L-prolific sows on HP farms had 12% or more PBA and piglets weaned than L-prolific sows on LP farms, suggesting that HP farms are better than LP farms at exploiting the potential of L-prolific sows.

In addition, our study showed that farrowing rates were 7.7% higher on HP farms than on LP farms, but that farrowing rates were only 0.7% higher in H-prolific sows than in L-prolific sows. This result clearly shows that farm effects had at least 10 times greater impact on farrowing rates than sows’ potential. These farm effects probably include better insemination timing, more advanced technologies [9, 10], better care in the breeding phase [18] and a stricter culling policy [19] on HP farms than on LP farms.

The approximately 27–30% fewer lifetime non-productive days across sow groups on the HP farms than on the LP farms indicates that HP farms could decrease non-productive days not just by having sows with better potential, but also by farm effects. High productive farms have shorter re-service intervals than low productive farms [14] that can be achieved through better breeding and culling practices. Additionally, in parities 1 and 6 in our study HP farms had more H-prolific sows and fewer L-prolific sows than LP farms. The result suggests that the HP farms probably had better feeding, better breeding practices, better care for sows at high risk of low productivity and stricter culling guidelines [20, 21] than the LP farms.

Our study also showed a notable decrease in PBA after parity 1 in H-prolific sows, whereas PBA increased after parity 1 in L-prolific sows. There is a hypothetical cascade from follicle development and embryo survival to pregnancy maintenance in sows [22]. Therefore, while H-prolific gilts may have had more potential than L-prolific gilts, for example, more ova, higher embryo survival and higher progesterone concentrations to maintain pregnancy, their ovarian function from ovaries to pregnancy decreased. One possible reason for this decrease in H-prolific sows is that their ovaries and uterus endometrium may not have had enough time to recover from continuous ovulations and farrowing. A decreased farrowing-to-mating interval decreases the total number of piglets born [23] and PBA at subsequent parity. Meanwhile, low prolific gilts may be associated with having litter of origin problems, such as low birth weight [24]. Therefore, our study suggests that differences in farm effects can affect patterns of reproductive performance in both H-prolific and L-prolific sows. Such differences in farm effects will include differences in gilt development, such as diet and boar exposure [25], facilities and workers’ stockmanship [26].

The lack of any association between either the sow groups or farm groups and weaning-to-first-mating intervals in our present study is similar to the findings in a previous study in Japan [3]. This lack of association may be due to the fact, that weaning-to-first-mating interval is highly related to gonadotropin secretion of sows, which in turn is affected by lactation management including feed intake [15, 27]. Also, the three farm groups had similar policy for ages at first-mating of approximately 250 days, and there was no association between the farm groups and age at-first mating.

Finally, there are some limitations that should be noted when interpreting the results of this observational study using herd data. Health status, nutritional programs and genotype were not taken into account in the analyses. Also, our data contained lifetime records from herd-entry to removal, so our data were not all current. However, even with such limitations, this research provides valuable information for pig producers and veterinarians about the impact of sow potential and farm effects on lifetime reproductive performance of sows.

Conclusions

Farm effects substantially affected reproductive performance across parities and lifetime performance of sows. Using sows with similar potential at parity 1, HP farms exploited lifetime productivity of sows better than on LP farms, especially L-prolific sows. The higher lifetime productivity of sows on HP farms than on LP farms was due to 8% higher farrowing rate, 27–30% fewer non-productive days and 7–11% more PBA during lifetime. Also, in parity 6 there were 15% or more H-prolific sows on HP farm than on LP farms.

Abbreviations

HP: 

High-performing

H-prolific: 

High prolific

ICC: 

Intraclass correlation coefficient

IP: 

Intermediate-performing

I-prolific: 

Intermediate prolific

LP: 

Low-performing

L-prolific: 

Low prolific

PBA: 

Piglets born alive

Declarations

Acknowledgements

The authors gratefully thank the swine producers for their cooperation in providing their valuable data for use in this study. We also thank Dr. I. McTaggart for his critical review of this manuscript.

Funding

This work was supported by the Graduate School GP-2017 from Meiji University.

Availability of data and materials

The dataset analyzed during the current study is not publicly available because producers’ privacy could be compromised.

Authors’ contributions

ST and YK were responsible for the study design. CP was responsible for data acquisition and participated in the study design. ST carried out the statistical analysis and drafted the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

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Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Authors’ Affiliations

(1)
School of Agriculture, Meiji University, Higashi-mita 1-1-1, Tama-ku, Kawasaki Kanagawa, 214-8571, Japan
(2)
PigCHAMP pro Europa S.L., c/Santa Catalina 10, 40003 Segovia, Spain

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Copyright

© The Author(s). 2018

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