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Reproductive performance of purebred Hampshire sows in
Sweden
a,c ,
*
b,c a,c a,cP. Tummaruk
, N. Lundeheim
, S. Einarsson
, A.-M. Dalin
a
Department of Obstetrics and Gynaecology, Faculty of Veterinary Medicine, Landscape Planning and Horticulture, Swedish University of Agricultural Sciences(SLU), Box 7039, SE-75007 Uppsala, Sweden
b
Department of Animal Breeding and Genetics, Faculty of Agriculture, Landscape Planning and Horticulture, Swedish University of Agricultural Sciences(SLU), Box 7039, SE-75007 Uppsala, Sweden
c
Centre for Reproductive Biology in Uppsala(CRU), Uppsala, Sweden
Received 26 November 1999; received in revised form 3 April 2000; accepted 22 May 2000
Abstract
The objective of this study was to retrospectively investigate causes of variation in the reproductive performance of purebred Hampshire sows in Sweden. Data analysed comprised farrowings between 1992 and 1998 from five Swedish nucleus herds and included 6347 litters from 2210 sows. The main traits analysed were litter size, weaning-to-first service interval (WSI), farrowing rate, remating rate and age at first farrowing. Analysis of variance was used for the statistical analysis of continuous data. Logistic regression was applied for categorical data using the GLIMMIX macro of the SAS programme. Factors included in the analyses were parity number, herd, year within herd, lactation length and month of the year (season). On average, Swedish Hampshire sows had 9.8 total piglets born / litter, 9.0 piglets born alive / litter, a WSI of 5.0 days, a 22% remating rate, a 68% farrowing rate and were 386 days of age at first farrowing. Parity influenced litter size at birth (P,0.001) and WSI (P,0.01). Season influenced (P,0.001) WSI, farrowing rate and age at first farrowing, but not litter size. However, the interaction between season and parity for litter size was significant. A longer lactation length resulted in a shorter WSI but the interaction between lactation length and season for WSI was significant (P,0.001). WSI influenced subsequent number of total piglets born / litter (P,0.01), farrowing rate (P,0.001) and remating rate (P,0.001). 2001 Elsevier Science B.V. All rights reserved.
Keywords: Pig; Hampshire; Reproduction; Season; Parity; WSI
1. Introduction
In Sweden, the Hampshire breed is mainly used as a sire line in commercial herds (Simonsson and *Corresponding author. Department of Obstetrics and Rydhmer, 1996). The Hampshire boars are produced Gynaecology, Faculty of Veterinary Medicine, Swedish University
by Swedish nucleus herds, which are at the top of the of Agricultural Sciences, Box 7039, SE-75007 Uppsala, Sweden.
Swedish pig breeding structure. To our knowledge, Tel.: 146-18-672-904; fax: 146-18-673-545.
E-mail address: padet.tummaruk@og.slu.se (P. Tummaruk). only a few studies on the reproductive performance
of the Hampshire breed have been reported (Rico, east. The variation within year in outdoor tempera-1988) and no such study has been made in Sweden. ture as well as in photoperiod is relatively high for It is well established that productivity of an this region. The outdoor temperature (24-h averages) individual sow depends on a number of reproductive in this area recorded during a period of 1994 to 1997 parameters, such as litter size at birth, weaning-to- ranged from a minimum of 214.48C in winter to a first service interval (WSI) and conception rate maximum of 26.68C in summer. Day length varied (Britt, 1986; Stein et al., 1990). The variation in from about 18.6 h in June to 5.9 h in December. these parameters is influenced by both genetic back- However, Swedish swine producers usually try to ground of the sow (reviewed by Rothschild and control the variation in photoperiod by supplying Bidanel, 1998) and environmental factors, such as artificial light to give approximately 14–16 h light / management and season (Clark and Leman, 1986; day in the sow units throughout the year. To obtain Dewey et al., 1995). Significant interaction between information concerning herd management, directed genotype of the sow and environmental factors has questionnaires were distributed to the herds included been observed (reviewed by Christenson, 1986). in the data analysed. For all herds, gilts were mated Recent studies have demonstrated that reproductive in their second observed oestrus or later at about 7 to characteristics of Swedish Landrace and Swedish 9 months of age. In most herds, dry sows were Yorkshire sows are differently influenced by factors grouped in loose-housing systems with deep straw such as season, parity and mating type (Tummaruk et bedding and individual feeding, whereas lactating al., 2000a,b). Although the Hampshire breed is used sows were kept separately in farrowing pens. Preg-mainly as a sire line in crossbreeding, information nancy detection was performed about 4 weeks after about their reproductive performance as purebreds is mating. Batch-wise production was performed in all still of great interest. A number of studies has shown herds, i.e., a group of sows entered the farrowing that the Hampshire breed has a smaller litter size unit on the same day, and all sows in that batch were than the European white breeds, such as the Land- weaned on the same day. After weaning, the sows race or Yorkshire (Schneider et al., 1982; Bass et al., were immediately transferred to the mating / gestation 1992; See et al., 1993). Number of piglets born alive units. During lactation the animals were either fed per litter for Hampshire sows has been reported to according to a Swedish standard level, e.g., 8 kg / day vary from about 7.4 (Rico, 1988) to 9.4 piglets (Bass (12 MJ / kg) for a sow with 10 piglets (Simonsson, et al., 1992). To our knowledge, no study on fertility 1994), or fed ad libitum. During gestation the sows traits such as WSI, remating rate, farrowing rate and were fed 2 to 2.5 kg feed / day. The reasons for age at first farrowing for Hampshire sows has been culling the sows were in most cases due to low
published. breeding value or poor conformation. In all herds, a
The objective of the present study was to re- number of crossbred litters (about 10%) were also trospectively analyse the variation in reproductive produced by crossing Hampshire sows with York-performance of purebred Hampshire sows with re- shire or Landrace boars. The crossbred litters were spect to parity influence and seasonal variation. The excluded from the statistical analyses, but results effects of lactation length and WSI on subsequent from crossbred matings were included when analys-fertility were also analysed. ing farrowing rate and remating rate.
2.2. Data analyses
2. Materials and methods
Data were collected from the Quality Genetics 2.1. Location and general management of the data bank (Quality Genetics, 1998). These data
herds included farrowing records obtained from five
consisted of herd and sow identities, sow birth date, days thereafter. If the first mating occurred within 20 boar breed, parity number, farrowing date, number of days and a repeated breeding took place within 18 to total piglets born per litter (NTB), number of piglets 100 days thereafter, Remating5‘1’.
born alive per litter (NBA), weaning date, mating
date and mating type (natural mating [NM] or 2.4. Statistical analyses artificial insemination [AI]). Variables like lactation
length (LL), farrowing interval, WSI, farrowing rate Statistical analyses were performed using SAS (FR), remating rate (RR) and age at first farrowing procedures (SAS Institute Inc., 1989). Descriptive (AFF) were calculated from the primary information. statistics were made using the MEANS and FREQ The day of weaning was defined as day 0 when procedures of SAS for continuous and categorical calculating WSI. The sows included in the analyses data, respectively. Analysis of variance was applied had to be born and farrowing within the same herd. to continuous data using the General Linear Model Records of parities that did not have complete (GLM) or MIXED procedures. Logistic regression information on the litter size at birth were excluded. was applied to categorical data (i.e., FR and RR) Errors in reported farrowing date records were using the GLIMMIX macro of the SAS programme. checked by constructing the frequency distribution of Variables describing the reproductive performance the farrowing interval and only observations with of sows, including litter size at birth (NTB, NBA) farrowing intervals between 140 days and 300 days and other fertility variables (WSI, FR, RR and AFF) were included in the analyses; otherwise both the were regarded as dependent variables. Factors re-previous and the succeeding farrowing data were garded to have an influence on reproductive per-regarded as missing values. LL in the analysed data formance were classified and included in the statisti-set was limited to 25–59 days (minimum 4 weeks cal models as independent variables. In two statisti-according to the Swedish animal welfare legislation). cal models (see below), WSI was also regarded as a WSI of sows with LL that did not fall within this factor influencing subsequent sow reproductive per-range (3.3% of all observations) as well as WSI formance. The main factors as well as their interac-longer than 20 days (6.9% of all observations) were tions were tested for significance. Only interactions considered to be missing values. Records from parity with a significance level of P,0.10 remained in the numbers above 8 were excluded (0.6% of all ob- final models. Least-squares means were obtained for servations). Sows that had a first-farrowing age of each class of effects and combination of effects and more than 470 days were excluded from all analyses were compared using t-tests. To account for the (6% of sows). The edited data contained observa- effect of herd management and yearly variation in tions on 6347 litters from 2210 sows. When analys- sow reproductive performance, the effect of herds ing litter size, crossbred litters were excluded and and effect of years nested within herd were taken 5592 purebred litters from 2171 sows were included into account for all statistical models (Table 2).
in the analyses. Normal distribution of residuals from the
statisti-cal models was checked using the UNIVARIATE
2.3. Definitions procedure option PLOT. The normality, skewness
and kurtosis were measured. Since WSI had a ‘‘Farrowing’’ is a binomial trait defined as ‘0’ positively skewed distribution, a natural log trans-when the first mating occurred within 20 days after formation was applied to the WSI data to obtain a weaning and no farrowing took place between 106 more symmetrical distribution. After the analyses, and 122 days after the first mating. If the first mating the results were back-transformed to obtain geomet-occurred within 20 days after weaning and farrowing ric means of WSI (in days).
took place within 106 to 122 days after the first
mating, Farrowing5‘1’. 2.5. Statistical models
‘‘Remating’’ is a binomial trait defined as ‘0’
with a complete set of all variables) and the sets of and LL were included in Models 4 and 5 along with explanatory variables with significant levels based on the effects included in Models 1 and 3, respectively. an F-test, are presented in Table 2. Parity numbers 6 Litters obtained from repeat breeding were excluded to 8 were pooled in all statistical analyses owing to from the analyses in Model 4. Model 6 was per-the low number of observations for each of per-these formed to study variation in age at first farrowing, higher parities. Seasonal effect was regarded as the based on primiparous sows farrowing during the effect of the month of the year when farrowing, period from January 1992 to December 1998. weaning or mating took place. The effect of sow
within herd was included in most statistical models,
except model 6, as a random effect to account for 3. Results
repeated observations for many of the sows. Model 1
was used to analyse the variation in litter size at birth 3.1. Descriptive statistics for reproductive obtained from purebred matings, based on farrow- performance
ings from January 1992 until December 1998. Using
Model 2, variation in WSI was analysed based on Descriptive statistics (based on edited data) for the weaning records obtained from July 1992 until June reproductive performance of Hampshire sows, in-1998. Weaning years were classified into six groups, cluding the number of non-missing values, arithmetic each representing a 12-month period (Jul / 92–Jun / means, standard deviations and ranges of the data, 93, Jul / 93–Jun / 94 and so on). LL was classified into are presented in Table 1. The percentage ratio of three groups based on the number of observations in litters obtained through NM vs. litters obtained each group (25–38, 39–45 and 46–59 days). Model through AI (NM: AI) was 85:15 for primiparous 3 focused on factors influencing FR and RR for sows sows (gilt matings) and 36:64 for multiparous sows. mated during the period from July 1992 until June However, NM was used less frequently than AI for 1998. LL and mating years were classified in the the sows being mated for the first time after weaning same way as in Model 2. In Models 4 and 5, effects (13:87). The proportion of AI used at first mating of WSI and LL on subsequent reproductive per- after weaning varied among the herds, ranging from formance were studied. WSI was classified into six 79% to 94%. Furthermore, the proportion of sows groups according to the number of observations and being mated by NM or AI depended upon WSI. For the general means of litter size in each group (0–3, WSI#7 days, a lower proportion of sows were 4, 5, 6, 7–9, 10–12 and 13–20 days). Effects of WSI mated by NM than by AI (5% vs. 95%), whereas for
Table 1
Descriptive statistics for some reproductive traits of Hampshire sows from five nucleus herds in Sweden during the period from 1992 to 1998
Parameter N Mean S.D. Range
Parity (all litters) 6347 2.8 1.8 1–8
Parity (purebred litters) 5592 2.6 1.7 1–8
Age at first farrowing (days) 1873 385.9 34.2 293–470
Total born / litter 5592 9.8 2.9 1–21
Live born / litter 5592 9.0 2.7 0–19
a
Lactation length (days) 5191 41.0 6.2 25–59
a,d
WSI (days) 3923 5.0 2.4 0–20
Farrowing interval (days) 3738 173.4 23.0 145–298
b,d c
Farrowing rate (%) 3922 68.3 – 53.3–83.1
b,d c
Remating rate (%) 3922 22.0 – 11.5–34.2
a
Based on sows weaned between July 1992 and June 1998 (6-year period).
b
Based on sows mated between July 1992 and June 1998 (6-year period).
c
Variation among herds.
*
a longer WSI (8–20 days), a higher proportion of Primiparous sows had a longer (P,0.01) WSI than sows were mated by NM than by AI (67% vs. 33%). sows in parities 3, 4, 5 and 6–8.
Additionally, NM was used mostly for the repeat Fertility of the sows, as indicated by FR and RR, breedings (79.5%). Due to these extreme imbalances, was influenced (P,0.001) by parity number (Table mating type was excluded from the statistical 2). Primiparous sows had the highest RR
(25.4%-models. units) and the lowest FR (63.7%-units). A decrease
Frequency analysis revealed that the proportion of in RR as well as an increase in FR was observed as sows remated within the period 18 to 100 days after parity number increased (Table 3).
first service was 22% (Table 1). Of those remating,
the proportions of repeat breedings within 18–24, 3.3. Effect of season 25–37, 38–45 and 46–100 days after first service
were 47%, 14%, 17% and 22%, respectively. Across parity, no seasonal variation in litter size at In Table 2, the structure of the analysed data and birth was found (Table 2). However, the interaction the levels of significance for all factors included in between parity and season was significant for both the statistical models are presented. NTB (P,0.001) and NBA (P,0.05; Table 2). Primiparous sows were less influenced by season 3.2. Effect of parity than multiparous ones; for instance, litter sizes (NTB and NBA) decreased when farrowing occurred in Parity number influenced litter size at birth (P, November for sows in parities 2 to 4 and in October 0.001) and WSI (P,0.01). Both NTB and NBA for sows in parities 5 to 8 but these events were not increased as parity number increased from 1 to 5, observed for parity 1 sows.
where the maximum litter size was observed (Table Season influenced (P,0.001) WSI (Table 2). The 3). The WSI was longest in primiparous sows and longest WSI was observed for sows weaned in decreased as parity number increased (Table 3). January, August and September (Table 4).
Further-Table 2
Structure of the analysed data and levels of significance for factors included in the models (significance levels for each factor are indicated using a P-value based on the F-test)
Data analyses Model 1 Model 2, Model 3 Model 4 Model 5 Model 6,
NTB NBA WSI FR RR SNTB SNBA SFR SRR AFF
Period of analysis (yr) 7 7 6 6 6 6 6 6 6 7
No. of observations 5592 5592 3923 3922 3922 2199 2199 3922 3922 1873
No. of sows 2171 2171 1544 1542 1542 1158 1158 1542 1542 1873
Statistical methods used MIXED MIXED GLIMMIX MIXED GLIMMIX GLM
Explanatory variables
Parity 0.001 0.001 0.002 0.001 0.001 0.001 0.001 0.001 0.001 –
Herd 0.001 0.001 0.001 0.001 0.001 0.039 0.121 0.001 0.001 0.001
Year (herd) 0.101 0.011 0.001 0.001 0.001 0.073 0.014 0.001 0.001 0.001
Season 0.426 0.159 0.001 0.001 0.057 0.341 0.068 0.001 0.086 0.001
Lactation length – – 0.001 0.098 0.353 0.622 0.291 0.094 0.379 –
WSI – – – – – 0.059 0.195 0.001 0.001 –
Parity3Season 0.001 0.050 NS NS NS NS NS NS NS –
Parity3Lactation length – – 0.072 NS NS NS NS NS NS –
Lactation length3Season – – 0.001 0.012 0.001 NS NS 0.011 0.001 – NTB5Number of total piglets born per litter; NBA5number of piglets born alive per litter; WSI5weaning-to-first-service interval; FR5farrowing rate; RR5remating rate; SNTB5subsequent number of total piglets born per litter; SNBA5subsequent number of piglets born alive per litter; SFR5subsequent farrowing rate; SRR5subsequent remating rate; AFF5age at first farrowing.
Table 3
Effect of parity number on reproductive performance (least-squares means)
Parity Model 1 Model 2 Model 3
N NTB NBA N WSI N FR RR
Means with a common superscript are not different (P.0.05). NTB5Number of total piglets born per litter; NBA5number of piglets born alive per litter; WSI5weaning-to-first service interval; FR5farrowing rate; RR5remating rate.
more, the interaction (P,0.001) between LL and LL of 4–5 and 6 weeks. However, for sows with a season for WSI revealed that the seasonal effect on LL of 7–8 weeks, the lowest FR was observed in WSI was more pronounced in sows with a LL of 4–5 sows mated in March.
or 7–8 weeks compared with an intermediate LL (6 A seasonal variation in age at first farrowing was
weeks; Fig. 1). also found (Table 2). Sows farrowing in August and
Seasonal influence was also found for both FR and September were younger (P,0.05) than those far-RR (Table 2). The lowest FR and the highest far-RR rowing during the period from October until January were found for sows mated in August and September (Table 4). A difference in AFF of more than 7 days (Table 4). The interaction between LL and season was significant.
was also significant for both FR (P,0.05) and RR
(P,0.001). Fig. 1 shows the seasonal variation in 3.4. Effect of lactation length FR. The pattern varied depending on the length of
lactation. A decrease in FR was observed in sows The effects of LL on subsequent litter size as well mated during August and September for sows with a as on subsequent FR and RR were not significant (P.0.05; Table 2). However, LL influenced (P, 0.001) WSI (Table 2). Across parity, weaning at Table 4
4–5, 6 and 7–8 weeks resulted in an average WSI of Seasonal variation in some reproductive traits (least-squares
means) 5.0, 4.7 and 4.6 days, respectively. Differences
e between least-square means $0.3 day were
signifi-Month WSI FR RR AFF
cant (P,0.001). In this data, about half of the litters (days) (%-units) (%-units) (days)
a bcd b a were weaned at 6 weeks of age (46%) and the
January 5.0 71.8 14.4 392.6
bc c c ab proportions of litters weaned between 4 and 5 and 7
February 4.6 77.7 13.0 388.8
c bcd b abc
March 4.5 71.3 15.0 385.8 and 8 weeks were 32% and 23%, respectively.
bc bc c bc
April 4.7 75.5 13.2 382.9
bc c b ab
May 4.7 76.3 15.1 389.2 3.5. Effect of WSI on subsequent reproductive
bc bd abc bc
September 4.9 63.3 19.5 382.1 A WSI between 7 to 9 days was followed by a
ab ad ab a
October 4.7 65.2 18.5 389.5 lower (P,0.05) subsequent litter size (NTB and
bc ab abc a
November 4.7 68.5 17.1 391.8 NBA) compared with a WSI of 4 days or 13–20 days
bc bc bc a
December 4.7 73.0 14.1 394.4
(Fig. 2).
abcd
Means with a common superscript are not different (P. WSI also influenced (P,0.001) subsequent FR 0.05).
and RR (Table 2). Sows with a WSI of 6 days had
e
Weaning month for weaning-to-first service interval (WSI),
the lowest FR and the highest RR, which differed mating month for farrowing rate (FR) and remating rate (RR), and
Fig. 1. Seasonal variation in weaning-to-first service interval (WSI) and farrowing rate by lactation length.
abcd
abcd
Fig. 3. Effect of weaning-to-first service interval (WSI) on subsequent farrowing rate and remating rate. Means with a common letter (within line) are not different (P.0.05).
20 days. Moreover, a WSI of 5 days resulted in a studies have shown that the selection for high lower (P,0.001) FR and higher RR compared with production might result in undesirable side-effects a WSI of 4 days (Fig. 3). for reproductive traits (reviewed by Rauw et al., 1998). The selection history, as such, may be one reason for the lower reproductive performance of the
4. Discussion Hampshire compared with the Landrace or Yorkshire
breeds, although the difference in production traits In the present study, the general mean of NBA between Hampshire and Landrace or Yorkshire was 9.0 piglets, which was within the range reported breeds is small.
in other studies of the Hampshire breed (Rico, 1988; The phenotype of the sow is influenced by both Bass et al., 1992). Descriptive statistics for general her genes and the environment which she has been reproductive performance of Hampshire sows (Table exposed to, starting during her foetal period. Pope et 1) reveal that the breed in Sweden is inferior al. (1990) demonstrated a genetic influence on concerning litter size, FR, RR and AFF compared embryonic disparity, which might subsequently in-with Swedish Landrace and Swedish Yorkshire sows, fluence the embryonic survival rate. However, only a but has a shorter WSI (Tummaruk et al., 2000a). An few single genes (e.g., the estrogen receptor gene) interesting point is that the Hampshire breed appears with a substantial impact on reproductive perform-to have a biologically inferior reproductive perform- ance have been identified (reviewed by Ashworth, ance compared with the Landrace and Yorkshire 1998). Therefore, further studies involving molecular breeds even when the climatic conditions, housing genetics are needed to elucidate the breed differences system, feeding routine and general management are in reproductive capacity.
rather similar. Biologically, a number of reproductive parameters,
early embryonic survival in Hampshire sows might performance (WSI, FR and RR) compared with explain the relatively lower litter size at birth and multiparous sows. As would also be the case for lower FR compared with the dam line breeds re- other breeds, the reason might be related to their feed ported earlier (Tummaruk et al., 2000a). Uterine size, consumption (Neil et al., 1996) and weight loss influencing embryonic and foetal survival, is an (Sterning et al., 1990) during lactation, and that important factor for the sow’s ability to maintain primiparous sows mobilise relatively more body pregnancy, which might differ according to the breed reserves than do multiparous sows (Pluske et al., or size of the sows. However, a comparative study 1998).
concerning the uterine space of the Hampshire breed
versus some superior reproductive white breeds has, 4.2. Effect of season to our knowledge, never been made.
The present study demonstrated that the fertility of In the present study, season influenced WSI the Hampshire breed was influenced by many fac- (weaning month), FR (mating month) and AFF tors, such as parity, season and LL. (farrowing month), which is in accordance with The levels of body weight loss and backfat loss previous studies of other breeds in temperate areas during lactation have been shown to influence the (Koketsu and Dial, 1997; Peltoniemi et al., 1999; WSI (Sterning et al., 1990). Hampshire sows lose Tummaruk et al., 2000a). Moreover, the interaction less body weight and backfat thickness during lacta- between season and LL also influenced (P,0.001) tion than do Landrace and Yorkshire sows (Gunsett, WSI (see below). The seasonal effects on WSI, FR 1990). Moreover, Hampshire sows have been re- and AFF have long been shown in crossbred sows ported to produce less milk than Landrace sows and these traits are more sensitive to seasonal during the first 10 days of lactation (Bass et al., influence than is litter size (reviewed by Love et al., 1992). These factors might, at least in part, have 1993). The mechanism of the seasonal effect on the contributed to a shorter WSI for Hampshire than for reproductive physiology of sows has yet not been the dam line breeds (Tummaruk et al., 2000a). clarified. However, oestrous signs, puberty and
em-bryonic survival have been considered.
4.1. Effect of parity Season did not influence litter size at birth.
However, interaction between season and parity was, The average parity number observed for Hamp- in the present study, significant for both NTB and shire sows in the present study was rather low NBA. Seasonal variation in litter size was more compared with that of the Swedish Landrace or pronounced in multiparous sows than in primiparous Swedish Yorkshire sows reported previously (Tum- sows. The same result was obtained by Xue et al. maruk et al., 2000a). One reason for this difference (1994) studying crossbred sows. They hypothesised might be that in the Landrace and Yorkshire herds, a that primiparous sows might have a different physio-number of sows with a breeding index too low for logical response to season compared with multipar-pure breeding remained in the herd and were used to ous sows.
produce crossbred dams for the commercial herds
instead of being culled. The effects of parity on litter 4.3. Effect of lactation length size, WSI, FR and / or RR observed in the present
RR. However, a significant effect of LL still existed Acknowledgements
for WSI. This is also in agreement with an earlier
report based on Swedish Landrace and Swedish This work was supported by grants from the Yorkshire sows (Tummaruk et al., 2000b). General- Swedish Foundation for International Cooperation in ly, many factors may contribute to the effect of LL Research and Higher Education (STINT). The au-on post-weaning reproductive performance of sows, thors thank Quality Genetics (formerly Scan Avel such as genetic line (Tummaruk et al., 2000b), parity HB) and the nucleus herds involved for providing (Mabry et al., 1996; Koketsu and Dial, 1997), feed information used in this study.
intake during lactation (Neil et al., 1996) and the ´ metabolic status of each individual sow (Hulten et
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