THE AMERICAN SOCIETY OF ANIMAL PRODUCTION 145
When the hog is given the preference of choosing his body
fat he prefers to deposit the ingested fat rather than synthesize new, and yet he protects his vital organs with harder
fat than he deposits on his back. The softer the carcass the
greater the variation between the refractive index of the leaf
and back fats.
In addition to maturity of the pig and hardness of fats present in the ration, the rate of gain seems to have an influence
on the firmness of fat produced. Other things being equal,
a rapidly gaining pig seems to be in better physical condition and will synthesize a higher percentage of his fats from
the carbohydrates and protein. Record of performance work
has proved that the most rapid gaining pigs are the most
profitable and fortunately all fat analysis work shows that
the fast gainers yield the firmest fat when fed on satisfactory
rations. Thus we will usually find the most economical gain
and the firmest fat in the fastest gainers--a very fortunate
combination.
THE SEEDY CUT PROBLEM IN SWINE*
By L. J. COLE, J. S. PARK, and ALAN DEAKIN
University of Wisconsin
The packing industry has long been familiar with a condition in hogs known as "seedy belly" or "seedy cut." It consists of pigmented areas in the ventral fat of the belly and
presumably receives its name from the speckled appearance
having a likeness to small seeds. Since this so-called "seed"
must be trimmed off for the better gr,ades of bacon it results
in an economic loss, as the trimmings are useful only for rendering into lard. The occurrence of seed is so frequent and
often so extensive that this loss amounts to a very considerable annual net sum to the industry.
Two Kinds of Seed
Three colors of seed are commonly distinguished, viz., black,
red, and white, but these really represent only two categories
* P a p e r s f r o m the Depaxtraent of Genetics, Agricult~urai E x p e r i m e n t Station, University of Wisconsin, No. 106. Published with the approval of t h e director of the station.
This is a p r e l i m i n a r y r e p o r t of a n investigation conducted by the D e p a r t m e n t s of Ge~
netics and Animal Husbandry, and supported in p a r t by funds supplied by the Institute
of A m e r i c a n Meat Packers.
]0--11863
146 THE AMERICAN SOCIETY OF ANIMAL PRODUCTION
if they are classed according to their nature and origin. All
seed is found to occur only in the m a m m a r y gland and is never
more extensive than the tissues of the gland. The first class
Of seed consists of granular pigment and is usually black in
color, though red pigment has also been described. If such
actually occurs, however, it is relatively infrequent and must
not be confused with the condition commonly designated as
red seed. This type of red seed, which constitutes the second
class, is not due to a granular pigment, but depends on the
physiological .and histological condition of gland. It depends
on certain changes in the gland structure, accompanied presumably by vascular congestion. White seed is also a phase
of gland condition and is unrelated to pigment production.
Black Seed
The nature and origin of black seed have been investigated
by Mackenzie, ]~arshall, and Hammond (1912-15) in England, They rightly demonstrated that it is a dermal pigment involuted with the epidermis at the time of the development of the m a m m a r y gland in the fetus. It comes to lie
in close contiguity to the epithelial cells lining the milk ducts,
and may also occur in the connective tissue between the ducts
or even in the surrounding fat. Since it is veritably a skin
pigment black seed is not found in white breeds of swine, except possibly in some instances where these have black skin
spots. It might be expected that red swine would have red
pigment in the gland, but observation has shown it usually to
be black when it occurs.
Since the seed does not extend beyond the glandular tissue it is to be expected that it would be less extensive in barrows than in gilts. This is found to be the case. The English investigations found also that it is restricted in spayed
gilts, corresponding with the lesser development of m a m m a r y
tissue. In older sows it largely or completely disappears cont r a r y to common belief.
Red Seed
Red seed is found with equal frequency in all breeds of
swine and is associated with the stage of development and
physiological condition of the m a m m a r y g l a n d . I t is definitely related to sexual development and to functional activitY.
Hence it does not occur in barrows nor in gilts prior to pu-
THE AMERICAN SOCIETY OF ANIMAL PRODUCTION 147
berty. As gilts reach puberty the gland takes on a reddish,
inflamed appearance, particularly at heat. The extent of this
condition presumably increases with succeeding heat periods
and becomes especially extensive and pronounced in older or
pregnant sows. Under these conditions the trimming necessitated is as great and in older sows much greater than that
occasioned by black seed.
Red seed thus appears to be largely .a cyclic phenomenon,
being greatest at estrus and subsiding during the di-estrous
period. The histological picture indicates that with the onset
of estrus there is an increased production of alveoli and probably an accompanying congestion of the capillaries. Following heat the alveoli largely disappear and connective tissue
tends to take their place. It is this connective tissue which
gives the appearance called white seed. Since white seed
ordinarily comes out clear in the cured bacon it necessitates
little or no trim in younger animals.
Economic Aspects
Since black seed (and red pigment seed) is related to skin
color of the hog, it is obviously determined to that extent by
the color factors determining skin color. Clear gland may,
however, occur even when the skin from which it arose is
colored. It is quite probable that this is also determined by
hereditary factors and that it might be possible to produce
a colored breed of swine which would nevertheless be free of
black seed. To do so would, however, be a slow and complicated process.
Red seed on the other hand, depending as it does directly
on the physiological processes of growth and sexual development, is not determined by ordinary genetic factors. Black
seed can be avoided by the use of white breeds, but this would
have no effect on the red seed. The loss from both kinds of
seed is less in barrows and in younger gilts. The tendency
to market pigs at an earlier age accordingly tends to reduce
the losses. They could also be lowered by avoiding the slaught e r of gilts when they are in heat if it were practicable to
separate them out and hold them until they were in the less
active stage of their sexual cycle. Any practicable method
of suppressing heat in gilts about to be slaughtered would
also tend to reduce the amount of red seed.