Inorganic vs Organic Selenium. Dietary
selenium (Se) supplemented in the form of organic Se from Se yeast, also called
selenized yeast, has higher bioavailability than Se from sodium selenite. Many
metabolic functions may be enhanced throughout the body simply by delivery
of more selenium to the bloodstream. Se yeast also provides modified
amino acids seleno-cysteine and seleno-methionine which may have specific beneficial
effects on metabolism as well. Plasma glutathione peroxidase contains an integral
and stoichiometric quantity of Se, and serves a natural antioxidant function
(Rotruck et al., 1973), along with vitamin E and ascorbic acid (vitamin C). Without
this protection, Se-deficient pigs may go into a proxidant shock after iron
injections and die. Se improves immune status because several indicators
of immunocompetence and immune respons-iveness are depressed in Se deficiency
(Latshaw, 1991). Some widely used veterinary pharmaceuticals may cause
increased demands for metabolic functions which involve Se (Combs, 1980).
Se is also necessary for deiodinase activity to
convert thyroxine (T4) into triiodothy-ronine (T3) which regulates basal metabolic
rate of cells throughout the body (Jianhua et al., 2000). Awadeh et al.
(1998) reported that sodium selenite or Se yeast providing 60 ppm Se to free-choice
salt increased plasma T3 by 14% in beef cows compared to 20 ppm Se from sodium
selenite. Se yeast contributing 60 ppm Se to salt increased plasma T3
in calves at birth by 56% and 77% compared to the 20 and 60 ppm Se from sodium
selenite treatments, respectively (5.3 vs 3.4 and 3.0 ng/mL).
The Se content of pork tissue may vary between states
or regions due to the indigenous Se concentrations of grains (for example,
lower Se in Corn Belt east of Mississippi River and along the East Coast) even
when sodium selenite is fed (Mahan et al., 2005). In a recent review
of selenium in sow and pig nutrition, Surai (2006) details
several selenium deficiency symptoms such as impaired reproduction, prolonged
farrowing, lactation failure, poor immune responses, nutritional muscular dystrophy,
mulberry heart disease, and reduced pig performance. Mahan et al. (1999)
found that tissue Se contents increased linearly as the dietary Se level increased,
but the increase was markedly higher when organic Se was fed to growing-finishing
pigs. Additionally, there was a trend for higher drip loss (P =
0.11) and a linear increase in loin paleness when the inorganic Se (sodium
selenite) level increased (P < 0.01), apparently due to sodium
selenite's proxidant activities. Kim and Mahan (2001a) showed that Se
at > or = 10 ppm from sodium selenite was toxic to growing-finishing pigs,
causing hair loss (alopecia) and separation of the hoof at the coronary band
site, whereas > or = 15 ppm from organic Se was required for similar responses. However,
plasma and blood cell Se contents were higher when the organic Se was used
compared to sodium selenite at similar dietary Se levels (P < 0.05). Therefore,
at equal dietary Se inclusion rates, organic Se contributes higher levels of
Se to the circulation than sodium selenite and yet is less toxic when overdosed.
In the Alltech, Inc. 30 June 2005 dossier for registration
of Sel-Plex® selenized yeast in the European Union, the following significant
effects on sows for reproduction and on sows for benefits in piglets were demonstrated:
1) increased Se transfer in milk and colostrum, 2) increased total Se in edible
tissue (loin, kidney, etc.), 3) decreased back fat, and 4) decreased Se in
feces and urine. No adverse effects of Se yeast have been found in piglets
given 10 times the maximum dose.
Sow Trials with Selenium Yeast.
Dietary organic selenium
in the form of Se yeast
(Sel-Plex®) for gestating and lactating sows has been evaluated in a number
of trials. Mahan and Kim (1996) fed diets with 0.1 or 0.3 ppm Se from sodium
selenite or Se yeast beginning about 60 days before breeding to gilts to end
of lactation (weaning of piglets). Milk Se increased, loin Se of neonatal
and stillborn piglets increased, and serum and loin Se of weanling piglets increased
as dietary Se level increased or when Se yeast was fed. Mahan (2000) added
0, 0.15, or 0.30 ppm Se from either sodium selenite or Se yeast to sow diets
for 6 days prepartum through 14 days of lactation. Short-term feeding of
yeast, but not sodium selenite, increased Se content of colostrum. Milk
Se at 7 and 14
days postpartum was 2.5 to 3 times higher when Se yeast was fed compared to inorganic
Se so organic Se was more effectively incorporated into milk.
Kim and Mahan (2001b) studied effects of high levels of 0.3, 3, 7, or 10 ppm
Se from sodium selenite or Se yeast in diets of gilts from 25 kg body weight
through one reproductive cycle. Colostrum and milk Se concentrations increased
as dietary Se levels
increased particularly when organic Se was fed (P < 0.01). Neonatal
and weanling pig
tissue Se and seum Se concentrations increased as dietary Se level increased
or when Se
was fed. Mahan and Peters (2004) started gilts at 27.6 kg body weight
on diets with 0,
0.15, or 0.30 ppm Se from sodium selenite or Se yeast and continued treatments
a reproductive cycle. Tissue and total body Se contents of newborn pigs
from 4-parity sows increased with increasing dietary Se level or with organic
Se (P < 0.01). Colostrum
and milk Se concentrations were subtantially greater in Se yeast fed treatments
(P < 0.01). Sow tissue Se levels were higher when fed Se yeast
rather than sodium selenite
(P < 0.01).
Lampe et al. (2005a, 2005b) reported results of feeding 0.3 ppm Se from sodium
selenite or Se yeast to sows from 80 days of gestation through lactation. Litter
data was analyzed from about 380 sows per treatment, and results are presented
in Table 1 (Trial 1). All litters were equalized to same number of piglets
on day of birth. Mid-lactation milk Se was greater in the Se yeast group. Sows
receiving Se yeast weaned significantly more pigs (P = 0.001) by 0.35
pigs/litter and had higher litter weaning weights (P = 0.01) by 4.6
lb at 0.6 days younger than those receiving sodium selenite. Piglets deaths/sow
(equalized litters basis) was reduced by Se yeast supplementation (P =
0.06). During the nursery phase of Trial 1, pigs from each sow treatment
were fed 0.3 ppm Se from either sodium selenite or Se yeast (2 x 2 factorial). An
influence of sow Se source was observed for total pig mortality plus culls in
the nursery phase, 96.8% from sows fed Se yeast and 94.6% from sows fed sodium
selenite (P = 0.10; main effect).
Unpublished results of sow Trial 2 by these researchers
are presented in Table 1. A
level of 0.3 ppm Se from sodium selenite was added to diets of 378 sows, or from
Se yeast to diets of 516 sows, beginning at 72 to 79 days of gestation. There
were trends for
a greater number of pigs born alive (P > 0.08) and for a reduction
in piglet deaths/sow with equalized litters (P < 0.14) when sows
received Se yeast in their diets. No pig body weights were taken at birth
or weaning in Trial 2. There were no significant differences due to treatments;
however, pigs weaned was slightly numerically higher (9.55 vs 9.42) and preweaning
mortality % was lower (12.6 vs 15.5) for pigs from sows receiving Se yeast compared
to sodium selenite.
Combined results for Trials 1 and 2, given in Table 1, included data from 761
sows fed sodium selenite in their diets and from 893 sows fed diets containing
Se yeast. When Se
yeast was supplemented to sow diets, there was a significant decrease in piglet
deaths/sow by 0.15 pigs (P < 0.02) and in weaning age (P < 0.01)
by 0.27 days, and an increase in the number of pigs weaned/litter (P < 0.01)
by 0.22 pigs.
Economic Implications of Fewer Piglet Deaths/Litter. The
economic benefit of weaning an average additional 0.15 pig/litter (or that many
fewer deaths/equalized litter) can be calculated under today’s conditions. Assuming
2.25 litters, 2.25 x 0.15 pigs/litter gives 0.34 more pigs/sow/year. If
the weaned pig is worth about $30, then 0.34 pigs x $30 gives $10.20/sow extra
revenue. At current costs, feeding Se yeast continually for a year shows
an average return on investment of about 7:1 and a reduction in sow feed cost/piglet
Two sow feeding trials were conducted at
a commercial facility with
diets containing 0.3 ppm added Se from either sodium selenite or Se yeast, fed
at 72 to 80 days of gestation through lactation. In one trial pig birth
and weaning weights were also recorded. In Trial 1 and Combined Trials
dietary Se yeast significantly increased the overall number of pigs weaned per
litter (+0.22 pigs for Combined Trials). Piglet deaths/sow in equalized
litters were significantly reduced by 0.15 pigs for Combined Trials, and this
advantage alone provides an estimated 7:1 benefit to cost ratio or return on
investment. Litter weaning weight, measured in Trial 1, was significantly improved
by +4.6 lb using sow diets with Se yeast compared to diets with sodium selenite. Litter
weaning weight reflected improvements in weaned pig numbers and body weights. Sows
fed Se yeast containing diets produced piglets with 2.2% lower preweaning mortality. Therefore,
Se yeast is recommended as a replacement supplement for sodium selenite in sow
gestation and lactation feeds from at least 72-80 days of gestation, and preferably
over the entire reproductive cycle, to improve pig numbers, body weight, and
Table 1. Effects of dietary Se source (sodium selenite
or Se yeast) providing 0.3 ppm
1No body weights were taken at birth or weaning in Trial 2
2Calculated as ([1-(total pigs weaned/total pigs born alive)] x
100). Mortalities included pigs laid on, those with low viability, etc.
3Includes days for gilts that were skipped first service,
following weaning, and bred on second heat.
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