Influence
of Cross-fostering on Piglet Growth and Survival
Introduction
Cross-fostering to equalize birth-weight within litter and accommodate
individual sow rearing capacity reduces preweaning mortality.
However, it is
important to implement cross-fostering correctly. When pigs are cross-fostered
after 3-days of age, the disruption of the newly established teat
order will likely result in reduced piglet weight gains and increase
preweaning mortality. For this reason, it is usually recommended that
cross-fostering be complete by 3-days after farrowing.
However, even this period may be too long. It has been shown that
antibody content of colostrum will decrease more than 50% within 12-hours
of farrowing. Therefore, if newborn piglets are fostered onto a sow
that had farrowed more than 12-hours previously, their passive immunity
will be compromised.
Further, survey
evidence derived from PigCHAMP indicates that preweaning mortality
is increased when greater than three piglets are fostered onto a sow.
It is apparent that further work is warranted to examine the effects
of cross-fostering on piglet performance.
Trial
We induced 120 mixed parity sows to farrow with cloprostenol. At farrowing,
the piglets were weighed and the lightest (L) 50% from two litters
were placed on one sow and the remaining heavier pigs (H) on another.
A third sow served
as a litter-intact control (I) and no pigs were cross-fostered. Cross-fostering
was completed within 12-h of birth. Pigs were weighed again at 3-d
and at weaning. Pig performance was assessed on the basis of survival
and preweaning growth rate.
Comparisons were
made between litter weight designations (H, L and I) and between H
and the heavier half of intact litters (I-heavy) and between L and
the lighter half of intact litters (I-light).
Results and Discussion
There was a significant sow effect on preweaning piglet growth and
survival (P<0.001). The effects of cross-fostering on piglet preweaning
growth and survival and a comparison between intact litters and the
heavier and lighter halves of the intact litters are shown in Table
1.
There was no
significant advantage or disadvantage for cross-fostered pigs. Weight
gain between days three and weaning was not affected by litter weight.
Post-weaning ADG was not affected by litter weight. Patterns of preweaning
survival were as expected with the heavier pigs having the least mortality
and this was unaffected by cross-fostering. We conclude from these
data that the creation of light birth-weight litters does not increase
or decrease preweaning survival.
Table 1. The Effect of Cross-fostering on Piglet Growth and Survial
Heavy Light Intact
I-heavy I-light Significance
Litter size 10.3 10.1 9.7 9.9 9.6 NS
Birth weight (kg) 1.46 1.02 1.27 1.46 1.07 NS
Weight day 3 (kg) 1.89 1.39 1.7 1.91 1.41 NS
Wean weight (kg) 7.2 6.7 7.41 7.8 6.69 NS
ADG day 3 - wean (g/d) 260 256 260 274 245 NS
Mortality to day 3 (%) 5.5a 14.8b 8.0ab 4.1a 11.8b 0.05
Mortality to wean (%) 8.7a 20b 11.4c 6.4a 19.5b 0.05
NS = no significant difference across the row; numbers within a row,
marked by different letters are significantly different
Roy Kirkwood, Louisa Zak and Laki Goonewardene
Can We Make Sows
Ovulate at the Time of Farrowing?
Short lactation lengths are associated with reduced sow fertility.
One aspect of this reduced fertility is a longer and more variable
wean-to-estrus interval. The Alberta Pork Research Centre is interested
in finding and evaluating new methods to control and synchronize post
weaning estrus.
We know that for about 30 hours after farrowing, the sow's ovary has
many large follicles and that her hormonal system is very active.
A new method of estrus synchronization that we have evaluated is causing
sows to ovulate at the time of farrowing with an injection of 1000
IU hCG (human chorionic gonadotropin). hCG is one of the components
of PG600. If we can induce ovulation at farrowing, the sow will go
through an estrous cycle and return to estrus about 21 days later,
regardless of when she is weaned.
We injected sows
with hCG at various times relative to farrowing and then determined
whether sows had ovulated based on blood progesterone concentrations.
A value greater than 5 nanograms (ng) of progesterone per mL of serum
indicates ovulation. A value between 2 and 5 ng per mL suggests a
partial effect and values less than 2 ng per mL indicates ovulation
did not occur.
We initially
treated 8 sows at 24 hours after farrowing. Based on blood progesterone
concentrations 7 days after farrowing, none had ovulated.
We then injected
a further 35 sows sooner after farrowing. This meant that if a sow
farrowed overnight, she was treated immediately the next morning.
If she farrowed during the day, she was treated last thing in the
afternoon. Of these sows, 17 (48.6%) ovulated.
In an attempt
to determine the best time to administer the hCG, we divided another
26 sows among the following treatments with the following results
(Table 1).
Table 1. The Effect of hCG Injection on Ovulation
Time of Farrowing hCG Injection Time Sows That Had Ovulated Sows That
Had Not Ovulated Sows With a
Partial Effect
Overnight next morning 1 2 3
Overnight next morning 2 4 0
During the day that afternoon 4 3 0
During the day next morning 4 3 0
These results
demonstrate that the sow's ovulatory response to hCG at farrowing
is far too unpredictable to be of commercial application.
Roy Kirkwood
and George Foxcroft
Articles
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