Effects of Season, Floor Type, Air Temperature and Snout
Coolers on Sow and Litter Performance
Wayne F. Stansbury, John J. McGlone and Leland F. Tribble
J ANIM SCI 1987, 65:1507-1513.
The online version of this article, along with updated information and
services, is located on the World Wide Web at:
http://www.journalofanimalscience.org/content/65/6/1507
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EFFECTS OF SEASON, FLOOR TYPE, AIR TEMPERATURE AND
SNOUT COOLERS ON SOW AND LITTER PERFORMANCE 1
W a y n e F. S t a n s b u r y , J o h n J. M c G l o n e a n d L e l a n d F. T r i b b l e
T e x a s T e c h U n i v e r s i t y 2, L u b b o c k 7 9 4 0 9
ABSTRACT
An evaluation of 341 sow and litter records over a 2-yr period was made to determine the
effects of floor type and season on sow and litter productivity. Floor types were plastic-coated,
expanded metal (PL) or concrete (CO) slatted flooring. Litters raised on PL had lower (P<.001)
mortality (10.3 +- .85 vs 15.4 -+ .83%), fewer splay-legged pigs/litter (.20 -+ .06 vs .48 +- .06) and
heavier weaning weights (61.0 t .8 vs 54.2 -+ .8 kg) than litters on CO. Sows ate less feed in the
spring (P<.05) than during other times of the year. A second study was conducted with 88 litters
to determine the effects of farrowing house temperature, floor type and snout coolers (SC) on sow
and litter productivity. Farrowing house air temperature were 18, 25 or 30 C, with sows on PL or
CO floors and with SC either on (910 cm/s) or off. At 18 and 25 C, average daily sow feed intake
was higher (6.46 -+ .21, 6.13 +- .19 and 4.20 -+ .19 kg) and litter weaning weights were heavier (63 -+
2.8, 61 -+ 2.5 and 52 -+ 2.5 kg) than at 30 C. Litter mortality at 18 and 30 C was higher (P<.05)
than for litters raised at 25 C (20.4 +- 2.6, 18.8 +- 2.3 and 12.0 -+ 2.3%, respectively). Litters raised
on PL at 18 C were 15 +- 3.4 kg heavier at weaning than litters raised on CO (P<.05). Providing SC
increased sow feed intake at all air temperature (P<.05). However, SC sows held at 30 C ate less
feed (P<.05) than sows held at 18 or 25 C. Snout coolers showed little benefit for litter performance while PL flooring, especially at 18 C, was beneficial to litter performance.
(Key Words: Air Temperature, Floor Types, Sows, Pigs, Season.)
I ntroduction
S n o u t coolers (SC) a n d d i f f e r e n t f l o o r t y p e s
h a v e b e e n u t i l i z e d b y p o r k p r o d u c e r s t o imp r o v e sow a n d piglet p e r f o r m a n c e a n d c o m f o r t
in w a r m e n v i r o n m e n t s . S n o u t coolers decrease
t h e negative i m p a c t o f h e a t stress o n sows in
f a r r o w i n g crates b y increasing c o n v e c t i v e ( a n d
p e r h a p s e v a p o r a t i v e - r e s p i r a t o r y t r a c t ) h e a t loss,
w h i c h decreases surface a n d core t e m p e r a t u r e
a n d r e s p i r a t i o n rate ( T a y l o r , 1 9 5 8 ; L i p p e r a n d
M c G i n t y , 1 9 6 1 ) . C o n c r e t e (CO) f l o o r i n g m a y
increase c o n d u c t i v e h e a t loss d u r i n g h e a t stress.
P r e f e r e n c e studies b y F a r m e r a n d C h r i s t i s o n
( 1 9 8 2 ) i n d i c a t e d t h a t pigs p r e f e r p l a s t i c - c o a t e d ,
e x p a n d e d m e t a l f l o o r i n g (PL) over o t h e r
p e r f o r a t e d f l o o r i n g . W e a n i n g weights ( W a s h a m ,
1981 ; M a b r y e t at., 1 9 8 2 ) , survival r a t e s ( J e n s e n
a n d Warren, 1981 ; Washam, 1981 ; M a b r y et al.,
1 9 8 2 ) a n d k n e e a n d claw injuries ( W a s h a m ,
t The authors thank Mr. Stanley Harris and Mr.
Benny Carrillo for technical help and Mr. John Drezek
for typing the manuscript. College of Agr. Sci. paper
no. T-5-228. Research supported by state of Texas
line item for efficient production of pork.
2 Dept. Anim. Sci., Behav. Physiol. Lab.
Received February 17, 1987.
Accepted August 3, 1987.
1 9 8 1 ; M a b r y et al., 1 9 8 2 ; K o r n e g a y a n d L i n d e m a n n , 1 9 8 4 ) were i m p r o v e d w h e n litters were
raised o n PL instead o f CO o r solid flooring.
T h e o b j e c t i v e s o f t h e s e s t u d i e s were t o d e t e r m i n e t h e effects o f season, air t e m p e r a t u r e , SC,
f l o o r t y p e a n d possible i n t e r a c t i o n s o n s o w a n d
piglet p e r f o r m a n c e .
Materials and Methods
General. D u r i n g g e s t a t i o n a n d t h e w e a n i n g t o - e s t r u s interval, sows were f e d 2 kg o f a 13%
c r u d e p r o t e i n s o r g h u m - s o y b e a n m e a l r a t i o n in
m e a l f o r m each day. B e f o r e b r e e d i n g , sows a n d
gilts were v a c c i n a t e d f o r leptospirosis. F o u r
weeks b e f o r e f a r r o w i n g , b r e d sows a n d gilts
were v a c c i n a t e d f o r erysipelas, a t r o p h i c r h i n i t i s
a n d pasteurella. B e f o r e sows were d u e t o
f a r r o w , a n d u n t i l w e a n i n g , sows were f e d a 14%
c r u d e p r o t e i n s o r g h u m - s o y b e a n m e a l r a t i o n in
m e a l f o r m a n d w a t e r ad l i b i t u m . W i t h i n 1 d
a f t e r p a r t u r i t i o n , piglets' tail a n d t e e t h were
clipped, ears were n o t c h e d , b o d y w e i g h t was
r e c o r d e d a n d piglets received 1-ml ( 1 0 0 m g / m l )
intramuscular injections of iron dextran and
a n t i b i o t i c . F o u r t e e n d a y s l a t e r b o a r s were
c a s t r a t e d a n d creep f e e d was o f f e r e d . Sows in
e a c h f a r r o w i n g g r o u p were w e a n e d a t a n
average age o f 2 8 d in a n all-in/all-out m a n a g e -
1507
J. Anita. Sci. 1987. 6 5 : 1 5 0 7 - 1 5 1 3
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1508
STANSBURY ET AL.
ment scheme, with litters ranging from 21 to 35
d. Rooms were cleaned, disinfected and left
vacant for a few days before pregnant sows
entered. A four-breed rotational cross (Hampshire, Landrace, Yorkshire and Duroc) was used
with crossbred sows and purebred boars.
Farrowing and gestation facilities were totally
enclosed and environmentally controlled. The
farrowing houses were two separate rooms
which accommodated 16 sows each. Farrowing
crates measured 1.5 x 2.1 m with a 56-cm
center area for each sow. Crates in each room
had eighter CO or PL flooring. The dimensions
of the slots in the CO flooring consisted of ten
1.3- • 46-cm openings at the front of the crate
and six 1.3- x 76-cm and four 2.5 x 76-cm
openings at the back of the crate. The four
2.5-cm openings were directly behind the sow.
A steel grate was inserted between concrete slats
before and up to 48 h after farrowing to
prevent injury to baby pigs' feet. In the center
of the CO crates were 90 cm of solid concrete.
The PL flooring encompassed the total area of
the farrowing crate and contained about 1,300
perforations/m 2 . All flooring was ground level
(that is, not raised). Localized cooling devices
(SC), connected to an evaporative cooling pad,
were located at the front of each farrowing
crate over the sow's head. Snout coolers could
be independently turned on or off. Two gas
heaters were located at opposite ends of each
farrowing room and a 250-W heat lamp was
located in the middle of the creep area in each
farrowing crate. Fluorescent lights were on for
1 to 2 h/d in all buildings during feeding and
animal care.
Exp. 1. An evaluation of 341 farrowing records, collected over a 2-yr period (1983 to
1985), was conducted to determine the effects
of flooring materials and season on sow and
piglet productivity. Flooring materials in the
farrowing barn consisted of either CO or PL
flooring. Month was determined where the
greatest a m o u n t of the lactation period occurred. The following months were combined
to give four seasons for analysis: December,
January and February = winter; March, April
and May = spring; June, July and August =
summer; September, October and November =
fall. All litters were from crossbred sows. Of the
341 litters, 262 litters were from multiparous
females and 79 litters were from primiparous
females. Cross-fostering occurred when litter
size was extremely large or when a sow died or
was injured. Records included: average piglet
and total litter weight at 1 d of age and at
weaning, number of piglets born alive and
dead, number of piglets at weaning, sire-breed
of piglets, weight of sow when entering the
farrowing house and at weaning, and sow feed
intake. Mortality (%) was calculated for each
litter as follows: [1 - (number pigs weaned/
number live pigs after transfer)] x 100. An
arcsin square root transformation was used in
the analysis of percentage data.
Analysis of variance with a factorial arrangement of treatments was applied. The model included main effects of season and floor type,
parity and the interactions among main effects.
Number of live pigs nursing each sow at 1 d of
age served as a covariate for all factors except
number of piglets born. This factor equalizes
effects of litter size and, to some degree, parity
across treatments. Means were separated by
t-tests, using error mean square as the source of
variance (predicted difference procedure within
SAS, 1982).
Exp. 2--Ternperature X SC x Floor Type.
Eighty-eight litters were utilized from January
to March 1985 to determine the effect of farrowing house temperature, SC and floor type
on sow productivity. Temperature and relative
humidity were recorded by a calibrated 24 h/d
hygrothermograph. Thermostats were set in the
farrowing house for target temperature settings
of 18, 25 or 30 C. The actual temperatures
were 18.0 -+ .5, 24.7 -+ .2 and 29.9 -+ .3 C for
the target temperatures of 18, 25 and 30 C, respectively. Relative humidity could not be recorded for the 25 C temperature setting. Relative humidity was 59.3 -+ 2.4% in the 18 C environment and 27 -+ 1.3% in the 30 C environment. Floor types were the same as described in
the sow survey section. Snout coolers were set
to direct air on the sow's head and neck at a
velocity of 910 cm/s. Air temperature exiting
snout coolers was not measured, but was always
cooler than inside air temperature. Sows and
gilts were randomly assigned to floor type or
SC (on/off) treatments within each temperature
setting. Measurements evaluated in this study
were the same as in the sow survey except sow
weight 24 h after farrowing and creep feed intake (CFI) also were recorded.
Analysis of covariance for a nested design
was applied to the data. The model was a complete randomized design with floor type and SC
nested within the main effect of air temperature. Number of live pigs on each sow after
cross-fostering on d I served as the covariate.
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FARROWING HOUSE ENVIRONMENT
1509
TABLE 1. LEAST-SQUARES MEANS FOR SOW AND PIGLET PERFORMANCE
BY PARITY AND SLOTTED FLOOR TYPE (EXP. 1)
Primiparous sows
Multiparous sows
P-values
I tern
Concrete
floors
Plastic
floors
Concrete
floors
Plastic
floors
Number of litters
Litter weaning wt, kg
Weaning number
Pig weaning wt, kg
Mortality, %
Splay-legged/litter
Sow feed intake, kg/d
Sow wt loss, kg/lactation
Weaning to estrus, d
52
50.28
8.4
5.99 b
14.39
.54
5.79
18.98
6.3
31
63.33 d
9.2
6.87 cd
6.29
.18
5.72
24.09
7.0
122
55.16 c
8.2
6.71 c
16.22
.48
6.63
17.46
5.2
136
60.78 d 1.16
8.8
.13
6.97 d .10
11.24
1.19
.22
.08
6.58
.12
22.35
1.54
4.8
.37
SE~
Floor
type
Parity
Interaction
.01
.01
.01
.01
.01
,68
.01
.76
.44
.05
.01
.03
.89
.01
.41
.01
.01
.33
.02
.30
.61
.96
.95
.31
apooled standard error of the mean, n = 85.
b'C'dMeans in the same row without a common superscript differ (P<.05).
R esu Its
Exp. 1--Survey, T r e a t m e n t m e a n s and standard errors f o r litter and sow weights and measures as a f f e c t e d b y f l o o r t y p e are p r e s e n t e d in
t a b l e 1. Litters raised o n PL floors were larger
( P < . 0 2 ) and heavier at w e a n i n g t h a n litters
raised o n CO f l o o r s ( P < . 0 0 1 ) . P e r c e n t m o r t a l i t y
a n d n u m b e r o f splay-legged pigs/litter were
higher in litters raised o n CO floors ( P < . 0 1 ) .
F l o o r t y p e did n o t have a significant e f f e c t o n
m o s t s o w measures. Sows lost m o r e w e i g h t o n
PL t h a n CO floors ( P < . 0 1 ) .
T w o variables were d i r e c t l y a f f e c t e d b y
season, n u m b e r o f splay-legged pigs and daily
s o w f e e d intake (table 2). Litters c o n t a i n e d
f e w e r splay-legged pigs per litter during t h e
s u m m e r ( P < . 0 5 ) t h a n during t h e fall or w i n t e r ;
s p r i n g - t i m e i n c i d e n c e was i n t e r m e d i a t e . Daily
s o w f e e d i n t a k e was l o w e r in t h e spring t h a n in
a n y o t h e r season ( P < . 0 5 ) . A t r e n d was f o u n d
f o r pigs to be heavier at w e a n i n g during t h e fall,
s u m m e r and w i n t e r w h e n raised o n PL floors
(P=.I ; figure 1).
Exp. 2--Temperature x SC x Floor Type.
T r e a t m e n t m e a n s and s t a n d a r d errors o f the
m e a n s f o r litter a n d s o w m e a s u r e s are p r e s e n t e d
TABLE 2. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR
SOW AND PIGLET PERFORMANCE BY SEASON (EXP. 1)
Season
Item
Fall
Spring
Summer
Winter
SE~
P-value
Number of litters
Litter weaning wt, kg
Weaning number
Pig weaning wt, kg
Mortality, %
Splay-legged/litter
Sow feed intake, kg/d
Sow wt loss, kg/lactationb
Weaning to estrus, d
75
56.67
8.6
6.64
13.22
.44 d
6.48 d
21.36
6.1
83
59.03
8.7
6.80
11.60
.32 cd
6.05 c
23.05
4.9
95
56.84
8.6
6.60
12.72
.17 c
6.56 d
19.98
5.6
88
58.18
8.5
6.92
13.94
.45 d
6.50 d
18.15
4.8
1.16
.13
.11
1.18
.08
.13
1.55
.44
.44
.48
.11
.83
.04
.02
.15
.13
apoo|ed standard error of the mean, n=85.
bweight change from entering farrowing barn (pre-farrowing) to end of 28-d lactation.
C'dMeans in the same row without a common superscript differ (P<.05).
Downloaded from www.journalofanimalscience.org by guest on July 19, 2013
1510
STANSBURY ET AL.
c
bc
~:~
bc
ad
i-
/ / k\x.\'q
4.
J
.......
/ / k\x.\'l
/_,,%
x,NN
/ Lx\x'~
/
//IX\\'~
//'J~,'N
//A~,.'N
I
0
FAI,I.
Figure 1. Interaction between season of the year
and floor type on 28-d pig weaning weight. Means
with different letters differ (P<.05; pooled SE=.15;
n=341).
in t a b l e 3. N e a r t h e s t a r t of this s t u d y , t h r e e
sows o n PL f l o o r s w i t h n o cooling died b e f o r e
or d u r i n g p a r t u r i t i o n . T h e r e f o r e , f a r r o w i n g
r o o m t e m p e r a t u r e was l o w e r e d to 28 C u n t i l all
sows h a d f a r r o w e d , t h e n t h e r m o s t a t s were
a d j u s t e d t o 30 C. T o t a l l i t t e r w e a n i n g w e i g h t s
were l i g h t e r in 30 C t h a n in 18 o r 25 C e n v i r o n m e n t s (P=.01). Average i n d i v i d u a l pig w e a n i n g
w e i g h t was h i g h e r in t h e 18 C e n v i r o n m e n t
( P < . 0 0 1 ) t h a n in 25 o r 30 e n v i r o n m e n t s . L i t t e r
m o r t a l i t y was 8 a n d 7% l o w e r ( P < . 0 5 ) in t h e 25
C t h a n in t h e 18 o r 30 C e n v i r o n m e n t s , respectively. Daily sow f e e d i n t a k e was similar in 18
a n d 35 C e n v i r o n m e n t s b u t was r e d u c e d in 30 C
air t e m p e r a t u r e ( P < . 0 0 1 ) . S o w w e i g h t loss was
g r e a t e r in t h e 30 C e n v i r o n m e n t ( P < . O 0 1 ) t h a n
a t o t h e r air t e m p e r a t u r e s . S o w s in t h e 18 C
e n v i r o n m e n t t o o k 2 to 3 d l o n g e r t o c o m e i n t o
estrus a f t e r w e a n i n g t h a n sows in t h e w a r m e r
environments (P<.01).
T h e m a i n e f f e c t o f SC was significant f o r
sow feed i n t a k e . Sows t h a t h a d access t o SC in
t h e 30 C e n v i r o n m e n t c o n s u m e d 1.0 kg m o r e
f e e d t h a n did sows w i t h o u t access to SC (figure
2). A l t h o u g h sow f e e d i n t a k e d u r i n g 30 C h e a t
stress was i m p r o v e d b y SC, sow f e e d i n t a k e was
still l o w e r t h a n in o t h e r air t e m p e r a t u r e treatm e n t s w i t h o u t SC. Piglet m o r t a l i t y was h i g h e r
in t h e 30 C e n v i r o n m e n t w h e n SC were o n a n d
in t h e 18 C e n v i r o n m e n t t h a n in t h e 25 C
e n v i r o n m e n t w h e n t h e SC were o f f (figure 3;
P=.05). Litters raised o n PL f l o o r s in t h e 18 C
e n v i r o n m e n t were over 15 kg h e a v i e r at w e a n i n g
t h a n litters raised e i t h e r o n CO at 18 C or t h a n
litters o n b o t h f l o o r t y p e s in t h e 30 C e n v i r o n m e n t ( P < . 0 5 ; figure 4).
Discussion
B a x t e r a n d Mitchell ( 1 9 7 7 ) s t a t e d t h a t floors
s h o u l d have c e r t a i n c h a r a c t e r i s t i c s : 1) n o t cause
injury, 2) n o t c o n t r i b u t e t o i n f e c t i o n , 3) n o t
c o n t r i b u t e t o stress, 4) b e m a i n t e n a n c e - f r e e , 5)
b e easy t o clean a n d 6) have as r e a s o n a b l e cost.
In t h e p r e s e n t s t u d y , o n l y p e r f o r m a n c e m e a s u r e s
w e r e c o n s i d e r e d , b u t i n f e r e n c e s can b e d r a w n
f r o m o t h e r studies t h a t h a v e c o n s i d e r e d t h e
first t h r e e c h a r a c t e r i s t i c s o f f l o o r types. In this
s t u d y , f l o o r t y p e i n f l u e n c e d p r i m a r i l y piglet
m e a s u r e s . C o m p a r e d w i t h CO, PL r e s u l t e d in
TABLE 3. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR SOW AND PIGLET
PERFORMANCE IN DIFFERENT FARROWING HOURSE TEMPERATURES (EXP. 2)
Temperature, C
Item
18
25
30
SE~
P-value
Number of litters
Litter weaning wt, kg
Weaning number
Pig weaning wt, kg
Mortality, %
Creep feed intake, kg/lactation
Sow feed intake, kg/d
Sow wt loss, kg/lactation b
Weaning to estrus, d
29
63.23 c
8.1
7.82 c
20.35 c
3.13
6.46 c
3.14 c
7.3 c
29
61.13 c
8.9
6.g7 d
11.97 d
3.04
6.13 c
7.86 c
4.4 d
30
52.38 d
8.3
6.40 d
18.79 c
2.61
4.20 d
24.21 d
5.3 d
2.47
.27
.20
2.29
.74
.19
2.25
.62
.01
.13
.001
.04
.88
.001
.001
.01
apooled standard error of the mean, n = 29.
bweight change from farrowing to end of 28-d lactation.
c,d
.
Means m the same row with different superscripts differ (P<.O5).
Downloaded from www.journalofanimalscience.org by guest on July 19, 2013
FARROWING HOUSE ENVIRONMENT
?"
a
a
i
i
a
r / A ~ " .\x~a
.......
/ / / lx~xx.N
I
//~\\\N
o
t|
2S
I~
Figure 2. Interaction between environmental temperature and snout coolers on daily sow feed intake.
Snout coolers had an air velocity of 910 cm/s. Means
with different letters on bars differ (P<.05; pooled
SE=.26 ; n=88).
greater numbers and weights of piglets at
weaning and fewer splay-legged piglets. An
increase in weaning weights, pen cleanliness and
increase in mortality has been associated with
an increase in floor perforation (Washam, 1981 ;
Mabry et al., 1982).
Studies in which lesions on legs and feet of
swine and preference of floor type by newborns
have been observed may give some insight into
differences observed in litter performance
between the two floor types in this study.
Jensen and Warren (1981) found that litters
raised on PL floors had lower incidence of
abrasions and lesions compared with concrete, metal and wood floors. Evidence of
bleeding from knee abrasions were highest for
24
CO flooring. Farmer and Christison (1982)
observed that piglets preferred to spend time on
PL floors compared with perforated metal,
fiberglass slats and woven wire floors. Baardson
et al. (1980) reported that piglets raised on
totally slatter CO floors had a higher incidence
of nipple necrosis than piglets raised on PL
floors. Although researchers have reported little
relationship between foot and leg injury and
performance (Jensen and Warren, 1981;Kornegay and Lindemann, 1984), data from Exp. 1
show that PL floors support greater litter
weaning weights, reduced piglet mortality and
fewer splay-legged piglets. Thus, the floor type
that piglets preferred also supported greater
litter productivity.
In this study, a higher incidence of splaylegged pigs occurred on CO. Thurley et al.
(1967) and Kohler et al. (1969) indicate that
floor type and texture can influence incidence
of splay-legged pigs. We observed that CO floors
were wetter around the side and rear areas of
sow. This observation may partly explain the
higher incidence of mortality and splay-legged
incidence on CO flooring.
Because facilities were completely enclosed
and extremes in outside temperature were tempered by use of SC during warm weather, season of the year had a relatively minor effect on
sow and litter performance in Exp. 1. The
summertime delay in return to estrus reported
by Clark et al. (1986) was not found in this
study.
In Exp. 2, sows exposed to 30 C temperatures during lactation consumed less feed and
lost more weight than sows exposed to continu-
"l
a
1511
b
be
20"
z/,
//J
iI'
ab
IS.
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Figure 3. Interaction between air temperature and
snout coolers on percent mortality. Means that do not
have a common letter on bar differ (P<.05; pooled
SE=3.19; n=88).
18
2I
10
Figure 4. Interaction between environmental temperature and floor type in farrowing crates on litter
weaning weight. Means that do not have a common
letter on bars differ (P<.05; pooled SE=3.44; n=88).
Downloaded from www.journalofanimalscience.org by guest on July 19, 2013
1512
STANSBURY ET AL.
ous temperatures of 18 and 25 C during lactation. Bond et al. (1952) reported that sows lost
more weight as environmental temperature increased. Cox et al. (1964) indicated that a continuous temperature of 29 C had a greater detrimental effect on sow feed intake than fluctuating temperatures between 18 and 32 C.
Studies in which sow feed intake was restricted
during lactation (.45 kg/piglet or 2.32 kg plus
.2 kg/piglet) showed that feed restriction increased sow weight loss with no effect on litter
performance (Elsley et al., 1969; Hitchcock et
al., 1971 ; Libal and Wahlstrom, 1975). Although
sow feed intake in the 30 C environment was
quite similar to the feed intakes of restrictedfed sows in other studies, litter weaning weights
were adversely affected. Temperature may have
had an indirect effect on piglet weaning weight,
because the lower and higher critical temperatures for 5-kg piglets were thought to be 23 C
and 31 C, respectively, on CO floors (Mount,
1968). Thus, piglets probably were not heatstressed in the 30 C temperature. Therefore,
reduced piglet weaning weights at 30 C must be
attributable to reduced sow feed intake and subsequent reduced sow milk production. Sows
held at 30 C had reduced feed intake and increased weight loss during lactation. Mortality
was lowest at the intermediate temperature.
Litters raised in cooler environments (10 to 20
C) experience higher mortality due to chilling
(Taylor et al., 1952; Parker et al., 1980; McGinnis et al., 1981 ; Nienaber et al., 1985). Although
piglets are able to increase heat production by
increasing their metabolic rate at an air temperature of 20 C, the pig's lack of insulation, sparse
pelage and a large surface area-to-body weight
ratio handicaps the pig in maintaining homeostasis (Mount, 1968; McGinnis et al., 1981).
Therefore, we speculate that increased mortality
at 18 C may have been due to chilling of piglets (sow feed intake was normal), but at 30 C
increased mortality may have been due to reduced sow feed intake and reduced milk production.
In the 30 C environments, SC increased daily
sow feed intake but did not bring feed intake
up to levels of sows in cooler temperatures (figure 2). Johnson and Taylor (1958) were among
the first researchers to study the use of localized cooling devices for sows. Bond (1959)
quoted Taylor (1958) as showing that cooling
of the sow increased sow comfort and decreased
rectal and surface temperatures and respiration
rates. Also, Lipper and McGinty (1961) showed
that in the temperature range from 26 to 33 C,
cool air resulted in lower daily rectal temperatures and respiration rates for sows confined in
crates but not for sows in pens. The tendency
for litters raised at 25 and 30 C with SC on to
have higher mortality that when the SC were off
indicates that SC may increase piglet heat loss
(figure 3). Piglets may not have been further
chilled by SC at the cooler air temperature of
18C.
Piglets raised on PL floors in the 18 C environment were heavier than piglets raised on
CO floor in all three environments and on PL
floors in the 30 C environment (figure 4). High
piglet conductive and radiant heat losses on CO
flooring may be responsible for the lower litter
weaning weights on CO compared with PL floors
at 18 C. However, thermal and physical properties of the floor seem less critical as air temperature increases (figure 4) to 30 C. However, the
thermal property of the floor did apparently
cause sow death on PL during heat stress.
Overall, SC had little overall beneficial effect on litter performance. In cool and warm
environments, PL flooring had a positive benefit on litter weaning weight. Sows and litters
held at 30 C showed evidence of heat stress,
which was not observed at 25 C. Heat stress
depressed sow feed intake, piglets weaning
weights and increased piglet mortality and sow
weight loss. Piglet mortality was increased and
the weaning-to-estrus period lengthened at 18 C
compared with sows held at 25 C. The range of
air temperatures supporting optimal sow and
litter performance is apparently narrow,
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