Department of Animal Science Florida Agricultural
Mimeograph Series No. 63-2 Experiment Station
July, 1962 Gainesville, Florida
SOW PRODUCTIVITY AS INFLUENCED BY SEASON
(A summary of two years data)
H. D. Wallace and G. E. Combs 1/
A new farrowing facility was constructed at the Florida Agricultural
Experiment Station Swine Farm in June of 1960. The facility was designed
for multiple year around farrowing. Sixteen permanent farrowing stalls
and 10 farrowing and holding pens are included. An open wing attached to
the main unit provides space for sow washing, weighing and individual
feeding stalls. The main unit is constructed of concrete block with a
galvanized aluminum roof. No structural insulation is included. Three
exhaust fans move air through the barn but no other cooling devices are
used. The barn is located on a shaded site where natural air circulation
The sow herd consists of 2 breed groups--purebred Durocs and Duroc
X Landrace F crossbreds. Approximately 12 purebred Durocs and 50 cross-
breds are maintained in the herd.
The Duroc sows are bred either to Duroc boars to furnish replacements
for the Duroc herd or to Landrace boars to furnish replacements for the
crossbred herd. The crossbred sows are bred to Hampshire boars. Pigs
from this 3-way cross constitute the main source of pigs for feeding
Definite breeding groups have not been formed and held constant but
rather are formed at each breeding period depending on the animals avail-
able. The objective has been to expose about 25 sows at each breeding
period. The breeding season covers a 21 day period and is spaced every
two months so as to provide a total of six farrowings per year.
Hand mating is practiced exclusively. Sows are mated either once
or twice during the heat period. Data on the comparison of one vs. two
matings is the subject of a subsequent report.
I/ Wallace and Combs, Animal Nutritionist and Associate Animal
Nutritionist respectively, Animal Science Department. The assistance
of W. E. Collins and L. S. Taylor, swine herdsmen, and the several
graduate students who helped with this project is gratefully
Feeding and Management of Sows During Gestation
All sows are maintained on forage during gestation. In the late fall,
winter and spring months this forage consists of oats and wheat and/or a
legume mixture of alfalfa, crimson clover and Kenland red clover. During
the summer months forage consists largely of native grasses which are
encouraged by fertilization and mowing. In the months of November,
December and January forage is not usually abundant. However, an abundance
of forage is available during the remainder of the year.
Sows are hand fed once per day in groups of 8-12 animals. The level
of concentrates fed depends on forage conditions, condition of the sows and
stage of gestation.
A flushing procedure is followed in which the concentrate level is
increased 50 percent 10 days prior to breeding and throughout the breeding
period. After the sows are settled the feeding level is reduced to 3-5
Ib. per head per day. Thirty days prior to farrowing the level is raised
to 5-6 lb. per head per day. Also, commencing 30 days prior to farrowing,
hygromycin is added to the gestation ration to help eliminate worm infesta-
tion to the young pigs. This treatment is continued during the lactation
The gestation ration is described in Table I.
Feeding and Management of the Sows at Farrowing and During Lactation
The pregnant sows are moved to the farrowing barn on the 110th day
of gestation where each is thoroughly cleaned with soap and water and
sprayed with benzene hexachloride to remove lice.
All sows are fed twice per day while in the farrowing barn, being
driven from the farrowing stalls or pens to the individual feeding stalls
located in the adjoining wing. Prior to farrowing each sow is fed 3 lb.
of concentrates each morning and evening. On the day of farrow feed is
offered only if the sow appears hungry. The next day 3-4 lb. of feed is
offered. This amount is increased each day so that by the end of the
first week of lactation most sows are consuming 8-9 Ib. feed per day.
This feed level is maintained during the second week at the end of which
the pigs are weaned.
The lactation ration is also described in Table I.
Care and Management of Litters
On the day of birth pigs are weighed and ear notched for identification.
Navel cords are tied off if necessary and the navel treated with a tincture
of iodine. Needle teeth are carefully clipped.
Injectable iron is administered to all pigs between 3 and 5 days of
age and male pigs are castrated at one week of age.
Heat lamps are used as needed to provide warmth for the baby pigs.
Pens are cleaned each morning. A special effort is made to provide a dry
environment for the pigs at all times. Wood shavings serve as bedding.
Automatic drinking cups provide fresh water for the sows and litters.
Table I. COMPOSITION OF RATIONS FED SOWS
DURING GESTATION AND LACTATION
Gestation 2/ Lactation ./
Ground yellow corn 61.19 65.09
Ground whole oats 20.00 10.00
Soybean meal (50% protein) 14.30 20.30
Steamed bonemeal 1.00 1.00
Ground limestone 0.75 0.75
Iodized salt 0.50 0.50
Trace mineral supplement 1/ 0.06 0.06
B-vitamin supplement 2/ 0.10 0.20
Vitamin B12 supplement 3/ 0.10 0.10
Vitamin A and D supplement l/ 2.00 2.00
I/ Calcium Carbonate Co. swine mix. Adds the following to the ration (p.p.m.):
Manganese (35.5), iron (43.8), copper (3.0), cobalt (1.0), zinc (50.4)
and potassium (4.7).
2/ Contains 2,000 mg. riboflavin, 4,000 mg. pantothenic acid, 9,000 mg.
niacin and 10,000 mg. choline chloride per pound of supplement.
3/ Contains a minimum of 9 mb. B12 per pound of supplement.
4/ Contains 14 gm. vitamin A supplement (10,000 I.U./gm.), 4 gm. vitamin D
supplement (9,000 I.U./gm.) and 890 gm. yellow corn.
5/ The gestation ration contains approximately 16 percent crude protein
and the gestation contains approximately 18 percent crude protein.
At two weeks of age the litters are individually weaned and moved to
the baby pig barn for use in.nutritional experiments. The sows are turned
back to pasture and grouped for rebreeding.
Results and Discussion
A summary of sow performance as influenced by season is presented in
Table 2. A graphic portrayal of the seasonal influences are presented in
Figures 1 and 2. The average number of live pigs per litter as shown in
Figure I has gradually increased from about nine in August of 1960 to over
ten in June of 1962. This reflects two things--an increase in the number
of crossbred sows relative to purebred Duroc sows, and an increase in the
average age of the sows in the herd. Crossbred sows have farrowed larger
litters than purebred Durocs and litter size has tended to increase with
The number of pigs weaned per litter has followed a clear seasonal
pattern. This is shown by the white portion of the bars in Figure I.
During the months of December, January, February and March sows have
generally weaned significantly larger litters than during the months of
Table 2. SEASONAL FARROWING PERFORMANCE OF SOW HERD
AUGUST 1960 JUNE 1962
Date Number Live Av. Birth Av. Number Av. Weaning Percent
of Litters Pigs Weight Pigs Weight Survival
Farrow Farrowed Per Per Pig Weaned (2 weeks) Birth to
Litter Ib. Per Litter lb. Weaning
AUGUST 1960 18 9.06 2.94 7.94 -87.6
OCTOBER 1960 21 9.09 2.98 8.00 --- 88.0
JANUARY 1961 15 9.93 2.97 8.87 8.35 89.3
MARCH 1961 28 9.39 2.92 .9.07 8.23 96.8
JUNE 1961 20 9.45 2.98 7.70 7.60 81.5
AUGUST 1961 24 9.21 3.04 7.33 7.49 79.6
OCTOBER 1961. 12 10.25 .2.62 8.42 6.85 82.1
DECEMBER 1961 16 10.60 2.83 9.56 7.96 90.2
FEBRUARY 1962 21 11.00 3.07 9.90 8.16 90.0
APRIL 1962 24 10.54 2.93. 9.09 7.61 86.2
JUNE 1962 25 10.32 3.03 9.36 7.16 90.7
224 9.87 2.95 8.67 7.73 87.8
FIG. I INFLUENCE OF SEASON ON PRODUCTIVITY
(University of Florida Sow Herd)
11.0 Losses from Birth to Weaning
i Number Pigs Weaned Per Litter -'/
i 0.0i >- --, -* -
Aug. Oct. Jan. Mar. June Aug. Oct. Dec. Feb. April June
1960 1960 1961 1961 1961 1961 1961 1961 1962 1962 1962
Season of Farrow
FIG. 2 INFLUENCE OF SEASON ON PRODUCTIVITY
(Univorsity of Florida Sow Hord)
I I I
1960 1960 1961
Season of Farrow
June, July, August and October. The differences in sizes of litters
weaned are largely a reflection of survivability and not much related
to original litter size.
A presentation of birth weights and weaning weights is found in
Figure 2. Birth weights were fairly constant throughout the year,
averaging about 3 lb. per pig. During the months of October and December
of 1961 there was a slightly lower average birth weight for which no
definite explanation can be offered. Litter size increased over previous
months at this time which may have had an effect on birth weights.
However, in subsequent farrowings litter size remained at a high level
and birth weights averaged about the usual 3 Ibs.
Weaning weights also followed a clear seasonal trend similar to
the number of pigs weaned per litter. During the cooler months weaning
weights averaged about eight pounds or better while during the hot summer
months these weights were reduced over 1/2 lb. per pig on the average.
It is believed that the seasonal differences in sow productivity as shown
by size of litter weaned and weaning weights were due almost entirely to
temperature influences. Management and nutritional factors were maintained
as constant as possible. No known disease problems were encountered during
the course of this study to influence the data. It was generally observed
that sows showed restlessness and discomfort in the farrowing barn whenever
the temperature surpassed about 750F. Midday barn temperatures often
reached 850 during the months of April, May, June, July, August, September
and October. Under these conditions sows tended to be more careless, thus
killing and injuring more pigs. Obviously milk flow was also reduced as
reflected in the lighter weaning weights. A summary of pertinent temperature
data is presented in Table 3.
Another phase of sow productivity studied in this project was that
of conception rate. Seasonal influences on conception rate are summarized
in Table 4. In general the summer breeding periods resulted in poor
conception-(55.6 80.8%), whereas during the cool months conception rate
averaged about 90% or better.
Eleven farrowings, commencing in August 1960 through June 1962 involving
224 litters and 2211 pigs were summarized to determine seasonal influences
on sow productivity. Sow performance has been considerably better during
the cool months when measured in terms of number of pigs weaned per litter,
weaning weights and conception rate. The data suggest a need for temperature
control in the farrowing barn during the summer months and a need for cooling
devices for sows and boars during the breeding season.
Table 3. TEMPERATURE DATA PERTINENT TO SOW PERFORMANCE
Date Av. Air Temperature I/ Av. Barn Temperature ./
August 1960 91.5 71.2
October 1960 85.0 62.2
January 1961 63.8 40.1 52.5
March 1961 81.1 54.0 65.5
June 1961 89.9 67.0 74.5
August 1961 90.8 71.3 77.7
October 1961 81.9 57.6 68.1
December 1961 72.6 46.6 54.6
February 1962 78.1 50.7 61.7
April 1962 81.7 52.6 70.1
June 1962 90.0 68.4 80.3
I/ From "Climatological Data" reports of Agronomy Dept. and
Florida (Observation time 4:30 P.M.)
2/ Average of 8 A.M. temperature readings from time Ist sow
sow weaned pigs at two weeks of age. Normally covered a
U.S. Weather Bureau, Gainesville,
entered farrowing barn until last
period of approximately 5 weeks for each
Table 4. CONCEPTION RATE AS INFLUENCED BY SEASON
Breeding Farrowing Number Number Percent
Date Date Bred Conceived Conception
Apr. 1960 Aug. 1960 27 18 66.7
June 1960 Oct. 1960 26 21 80.8
Sept. 1960 Jan. 1961 27 15 55.6
Nov. 1960 Mar. 1961 31 28 90.3
Feb. 1961 June 1961 21 20 95.2
Apr. 1961 Aug. 1961 26 24 92.3
June 1961 Oct. 1961 17 12 70.6
Aug. 1961 Dec. 1961 25 16 64.0
Oct. 1961 Feb. 1962 25 21 84.0
Dec. 1961 Apr. 1962 27 26 96.3
Feb. 1962 June 1962 28 25 89.3
Totals 280 226 80.7