Abstract Previous studies have shown that use of altrenogest resulted in a high rate of fertility and increased litter size compared with controls under conditions of practical pig production. The present study was designed to evaluate whether ovulation rate and/or foetal survival were increased by altrenogest using crossbred gilts derived from one herd (n = 227) and introduced in the same piggery over 12 months. Each gilt was allocated to a treated group (n = 103) receiving an individual daily dose of 20 mg of altrenogest for 18 days in its feed or a control group (n = 124) after puberty had been diagnosed, (197 ± 1 day; mean ± SEM). They were inseminated (double AI) at the second induced or natural oestrus. Pregnancy was diagnosed by ultrasonography at Days 22 and 42 post-insemination in the absence of return to oestrus. Pregnant gilts were slaughtered at 48 ± 3 days of pregnancy following the second examination. The number of living and dead foetuses were recorded before uterine contents (foetuses and placentae) were weighed and the number of corpora lutea (CL) per ovary counted. Precise synchronization of oestrus was observed after the end of the progestogen administration, with 93% of the gilts in oestrus by Days 5 to 7. For the controls, the interval from first to second oestrus ranged from 17 to 25 days in 93% of the control gilts. The pregnancy rate was 89.3% for treated gilts and 77.4% for controls (P 0.14). The percent of foetal survival was similar in both groups (64.9%; P > 0.27). The foetal and placental weights differed only between dams and increased with stage of gestation. The increase in litter size through feeding altrenogest was associated with an increased ovulation rate.
[1]
A. Moreau,et al.
Control of oestrus in gilts II. Synchronization of oestrus with a progestagen, altrenogest (Regumate): Effect on fertility and litter size
,
1990
.
[2]
J. Signoret,et al.
Control of oestrus in gilts I. Management-induced puberty
,
1990
.
[3]
J. Chambers,et al.
The New S Language
,
1989
.
[4]
M. Terqui,et al.
Control of pig reproduction in a breeding programme.
,
1985,
Journal of reproduction and fertility. Supplement.
[5]
B. N. Day,et al.
10 – THE CONTROL OF OVULATION
,
2020
.
[6]
B. N. Day,et al.
Control of estrus in gilts with a progestogen.
,
1979,
Journal of animal science.
[7]
G. A. Lodge,et al.
Growth and development of mammals.
,
1968
.
[8]
Allan R. Wilks,et al.
The new S language: a programming environment for data analysis and graphics
,
1988
.
[9]
B. N. Day,et al.
Estrus and ovulation in gilts fed a synthetic progestogen.
,
1981,
Theriogenology.
[10]
G. Foxcroft,et al.
Control of Pig Reproduction
,
1982
.
[11]
Richard A. Becker,et al.
The New S Language
,
1989
.