SUMMARY
Effect of injections of high levels of vitamin A on reproductive
performance of sows.
Darroch, C. S., L. I. Chiba, M. D. Lindemann, A. F. Harper,
and E. T. Kornegay, S-145 Committee on Nutritional Systems
for Swine to Increase Reproductive Efficiency.
A cooperative regional study involving 417 litters was conducted
at four experiment stations (Alabama, Kentucky, Tennessee and
Virginia) to determine the effect of an intramuscular injection
of 250,000 IU or 500,000 IU of vitamin A, or a placebo at weaning
and breeding on reproductive performance of sows. Gilts and
sows were allotted to one of three treatments and data was
collected over three reproductive cycles. Sows were fed 1.82
kg/day (2.27 kg/day during December, January, and February)
during the breeding period and before farrowing. Feed was consumed
on an ad libitum basis during lactation. Corn-soybean meal
based diets were formulated to contain 0.60% and 0.90% lysine
for breeding-gestation and lactation, respectively. Data for
response criteria were analyzed using GLM procedures of SAS.
The model included parity, treatment, station and treatment
x station interaction. Parity was used as a covariant.
There were 10.7, 10.8, and 10.4 ± 0.41 pigs born alive
per litter (P = 0.78) for sows given 250,000 IU vitamin A,
500,000 IU vitamin A and the placebo, respectively. The effect
of vitamin A injections on litter size was more apparent for
the number of pigs weaned per litter, when compared to the
placebo group (9.3 vs 8.6 ± .21; P = 0.09). Vitamin
A did not affect the days to return to estrus (5 ± 0.15;
P = 0.15) after weaning at 25.6 ± 0.38 days of lactation.
Average piglet weights were affected (P < 0.001) by station
and correlated to station differences (P < 0.001) in lactational
sow feed intake. There were significant main effects of treatment
and station on sow body weights at breeding, farrowing and
weaning; but there was no clear relationship to the apparent
increase in litter size following the injection of vitamin
A. Although treatment x station interactions were not significant
for any reproductive variable tested in this trial, differences
in initial body weights of sows allotted to treatments, and
differences in performance of sows at each station may have
contributed to variation in body weights.
The results indicate that the injection of high doses of vitamin
A in sows at weaning and breeding improves reproductive performance
by increasing the number of pigs weaned per litter.
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