74 P
. Tummaruk et al. Livestock Production Science 68 2001 67 –77
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, It is well established that the Landrace and
such as ovulation rate, fertilisation rate, embryonic Yorkshire breeds have been selected to improve the
survival and ability of sows to maintain pregnancy genetic potential for both production i.e., leanness
until term, contribute to reproductive performance and growth rate and reproduction traits for many
litter size, FR, RR. Johnson and Omtvedt 1973 years, whereas the Hampshire breed is currently
reported that ovulation rate and embryonic survival selected only for production traits reviewed by
were lower for the Hampshire than the Yorkshire Rothschild and Bidanel, 1998. Recently, genetic
breed. Thus, either low ovulation rate and or low
P . Tummaruk et al. Livestock Production Science 68 2001 67 –77
75
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 study were similar to reports in other pig breeds
Regardless of sow breed, studies have shown a Koketsu and Dial, 1997; Tummaruk et al., 2000a.
negative effect of a short LL, especially less than 2 The largest litter size at birth, obtained in parity 5, is
weeks, on subsequent reproductive performance, i.e., in accordance with an earlier study on Hampshire
WSI Xue et al., 1994; Mabry et al., 1996, em- sows Rico, 1988. The Hampshire breed seems to
bryonic survival Svajgr et al., 1974; Marsteller et be similar to the white breeds concerning the parity
al., 1997, conception rate Marsteller et al., 1997 effect on reproductive performance. The present
and FR Mabry et al., 1996. In the present study, study showed that primiparous sows had the lowest
where the average LL was about 6 weeks, no effect litter size and a poorer post-weaning reproductive
of LL was observed on subsequent litter size, FR or
76 P
. Tummaruk et al. Livestock Production Science 68 2001 67 –77
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
al., 1993. Body condition of the sows during
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5. Conclusions
