The mammalian body is in a constant state of turnover with cell
replacement occurring as a natural renewal mechanism. Old,
dying cells are broken down and reabsorbed into the body but have a
tendency to undergo a process called oxidation - the same process
that makes butter go rancid - with the production of toxic
peroxides or free radicals. These chemicals are highly
damaging to other tissues and in the healthy body are avoided by
the presence of anti-oxidants usually provided in the diet.
There is a wide range of these chemicals involved in metabolism
with each animal species having its own priorities. In the
pig, the three main groups providing anti-oxidant protection
- Vitamin C
- Vitamin E and selenium
When deficiency occurs, metabolic pathways are disturbed and
damage results. In the pig, Vitamin E and Selenium - working
in conjunction - are the primary limiting anti-oxidants and as such
it is deficiency of one or both of these which is associated with
typical disease problems. In this paper, the effects of deficiency
in young growing pigs will be discussed; the role of Vitamin E in
sow breeding efficiency is outside the scope.
Fig 1: Typical Mulberry Heart Disease showing
oedema and streaking of the heart.
Fig 2: Acute Porcine Stress Syndrome can be
mitigated by raising anti-oxidant provision; note here the 'just
cooked' appearance of affected muscle.
The most obvious effect of Vitamin E/Selenium deficiency in the
pig is sudden death, typically in young fast growing weaners,
although it can be seen in piglets still on the sow beyond the
3rd week of life.
Two principle presentations can be seen at post mortem
1. Mulberry Heart Disease (MHD). Here the
toxic peroxides target heart muscle leading to myocardial
failure. The heart will generally be enlarged with white?
streaks throughout the muscle. There is usually an
accumulation of 'jelly' around the outside of the heart within the
pericardium - which must be distinguished from pericarditis.
Additionally, the lungs will show signs of right sided heart
failure with fluid accumulation and interlobular oedema. (Fig
1.) Affected pigs will often be the best pigs in the group -
the fastest growing pigs having the highest requirement for Vitamin
E/selenium. It is suggested that MHD is more a manifestation
of Vitamin E deficiency than selenium shortage.
2. Hepatosis dietetia. Here the damage is done
to the liver. Whilst standard text book descriptions suggest
an enlarged mottled appearance to the liver, most commonly in
practice, the liver is enlarged and engorged with blood and has
split, resulting in haemorrhage into the abdomen. (Such
damage must be
differentiated - particularly in the sucking pig - from trauma
as a result of crushing.)
It is quite possible to see both manifestations in the same pig
along with some degree of skeletal muscle damage - which is the
predominant manifestation of Vitamin E/Selenium deficiency in
ruminants. Selenium deficiency may be implicated as the
predominant issue where liver damage is the primary presenting
Suspected deficiency of either Vitamin E or selenium can be
verified by laboratory testing involving analysis of tissue levels
(especially in the liver) and histopathology of affected organs.
Furthermore, where a population is suspected of ongoing deficiency,
cross-sectional blood sampling for levels of Vitamin E and
glutathione peroxidise - the enzyme which contains Selenium - can
reveal falling levels over the post-weaning period.
Notwithstanding the classic presentations of MHD and Hepatosis
dietetia, the role of Vitamin E in the functioning of the immune
system should not be underestimated. Challenge to the pig by
any disease process triggers an immune reaction, which is highly
expensive in terms of nutrients and micronutrients. Adequate
levels of Vitamin E and Selenium are necessary for such a reaction,
but conversely are consumed in the process. Thus, a challenge to
the immune system can have a Vitamin E/Selenium depleting effect-
which can be demonstrated by blood sampling - exposing the pig
either to acute deficiency or a compromised immune system.
As vaccination involves challenging the immune system,
vaccination of young pigs will only be successful if the pigs have
adequate Vitamin E/Selenium but can also act to deplete reserves,
particularly where multiple vaccination occurs. (Some vaccines now
contain Vitamin E as part of the adjuvant offsetting this
Sources of Vitamin E/Selenium
The transfer of Vitamin E across the placenta to the developing
foetus is generally poor (but better for Selenium) with the piglet
relying on Vitamin E transfer in fat particles within
colostrum. (Transfer via milk is minimal.) The 'dose'
of Vitamin E received in this way must last the piglet until such a
time as it is eating sufficient food to supplement its
resources. Serial blood testing has shown that in modern pig
keeping, there can be a dramatic drop in serum Vitamin E levels
after weaning and thus it is critical that:
a) Sow colostrum contains the highest possible levels of
Vitamin E by ensuring high levels in sow diet in the month prior to
farrowing, possibly supplemented with Vitamin E injections which
might be included in vaccines.
b) Every pig receives its full dose of Vitamin E within
the first 6 hours of life from colostrum.
c) Following weaning, diets must be adequately
supplemented with Vitamin E/Selenium and feed intake must increase
rapidly to fulfil requirements.
It should also be mentioned that certain dietary constituents
can have a Vitamin E depleting effect - particularly saturated fats
and proprionic-acid treated corn - whilst wheat offal can act to
Whilst fast growing pigs are most susceptible to MHD/Hepatosis
dietetia, a range of other factors should be considered as possible
1. Excessive disease challenge post weaning.
2. Excessive vaccinal challenge post weaning - ensure,
where multiple vaccination is needed that veterinary guidance is
followed with respect to separation of different doses.
3. Highly susceptible breed types. Landrace animals are
claimed to be more vulnerable but also Halothane gene (stress gene)
carriers are known to have a higher anti-oxidant
requirement which can be met by Vitamin E supplementation.
(This issue is of less significance now that the stress gene has
been largely bred out of the UK pig population.) (Fig 2.)
Levels of Vitamin E
This is a highly contentious area with recommended levels
frequently found to be inadequate in the field. Typical
compound diets nowadays may have the following levels of Vitamin
- Sow diets (lactator and dry sow) 100 iu/kg
- Creep diets 250 iu/kg
- Weaner diets 100-150 iu/kg
- Grower and finisher diets 40-100 iu/kg
Selenium levels are normally limited to no more than 0. 3ppm of
the diet as high levels of Selenium can be toxic.
Vitamins, in particular, decay in storage and thus, use-by dates
and correct storage provision must be observed. This is
particularly important for creep diets, which on smaller farms can
take time to use, and are frequently stored in warm rooms.
Treatment and Control
Where a problem is identified, additional antioxidants must be
provided. Whilst supplementing the diet with additional
Vitamin E is the obvious solution, it will take time to work
through the system - at least 2 weeks of supplemented feed is
needed to restore Vitamin E levels - and the escalating costs of
Vitamin E has triggered interest in alternatives. In the
acute disease situation, Vitamin C can be successfully supplemented
via water for 5-7 days. Alternatively, injectable
Vitamin E can be given around weaning. Vitamin C can be
included in creep diets in addition to Vitamin E but only where
diets are prepared as meal or are pelleted using cold water - hot
pelleting will destroy Vitamin C.
The increasing use of organic acid supplements - especially in
young pig diets - can provide additional bio-flavenoids to support
the Vitamin E antioxidant system.
Minimising disease challenge, minimising stress and review of
vaccination regimes, particularly where multiple vaccination occurs
around weaning in the young pig will all have a Vitamin E/Selenium
Whilst sporadic deaths associated with Vitamin E/Selenium
deficiency may be commercially tolerable if growth rates are high,
particularly given the escalating costs of supplemental Vit E,
there is an obligation on pig keepers to the wellbeing of their
charges and to take all reasonable measures to ensure survival. In
specific cases of severe problems, post-weaning mortality levels
can reach 4% of production associated with acute antioxidant
production. This can equate to additional cost per pig produced of
Furthermore, where anti-oxidant levels are marginal, triggering
secondary infectious disease such as Porcine Respiratory Disease
Complex, the cost per pig measured by the mixture of lost growth,
mortality and medication can more than double.