Reproductive performance in primiparous sows after postweaning treatment with a progestagen

Desempeño reproductivo en hembras primerizas después del tratamiento post destete con un progestágeno

La performance reproductrice dans les truies primipares après le traitement post-sevrage avec un progestagen

Lina Fernández, DVM, PhD; Carmen Díez, DVM, PhD; José María Ordóñez, DVM; Maite Carbajo, DVM, PhD

LF, MC: Reproducción y Obstetricia, Dpto Patología Animal (Sanidad Animal), Facultad de Veterinaria, Campus de Vegazana s/n, 24071 León, Spain; CD: Serida-Censyra, Camino de los Claveles 604, Somió, 33203 Gijón, Spain; JMO: Cooperativa Progatecsa, Valladolid, Spainl Corresponding author: Dr Lina Fernández, Reproducción y Obstetricia, Dpto Patología Animal (Sanidad Animal), Facultad de Veterinaria, Campus de Vegazana s/n, 24071 León, Spain; Tel: 34 987 291319; Fax: 34 987 291304; E-mail: dsaafc@unileon.es.

Cite as: Fernández L, Díez C, Ordóñez JM, et al. Reproductive performance in primiparous sows after postweaning treatment with a progestagen. J Swine Health Prod. 2005;13(1):28-30.
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Keywords: swine, altrenogest, primiparous, reproductive performance
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Received: October 8, 2003
Accepted: June 22, 2004

Progesterone and synthetic progestagens have been used to control estrus and ovulation in domestic animals. Altrenogest (Regumate; Roussel-Uclaf, París, France) is a progestagen that suppresses estrus and results in a synchronized return to estrus following its withdrawal, without a reduction in fertility or litter size.¹ Regumate is licensed for use in swine in Europe and in the United States. However, few studies have been conducted using this progestagen in primiparous sows, in which litter size is smaller and weaning-to-estrus interval (WEI) is longer than in multiparous sows.² Administration of altrenogest to pri-miparous sows, starting the day of weaning or the day after weaning, prevents estrus, allowing the sows to recuperate from lactation. In a study by Koutsotheodoros et al,³ both the percentage of sows showing estrus after withdrawal of the product and subsequent fertility rates were higher than in the control sows. Therefore, an increase in conception rate and litter size in the farrowing following administration of altrenogest may be observed, depending on dosage and timing of progestagen administration.⁴ The purpose of this study was to test the hypothesis that administration of altrenogest to primiparous sows for 5 consecutive days, starting the day after weaning, would improve the reproductive efficiency of the herd, measured in terms of estrus synchronization rate, the interval between weaning and first estrus after weaning (WEI), the interval between weaning and first fertile estrus after weaning (WFEI), proportion of sows repeating estrus, and conception rate at first estrus.

Materials and methods

First-parity sows (Landrace x Large White) from a commercial herd were used in this study. The sows were examined for standing estrus twice daily at 9:00 am and 2:30 pm using a mature boar. Duration of estrus was not measured. Boars used for mating were randomly chosen from a group of 20 boars. Pigs were weaned at 21.8 +/- 0.01 days of age. Each sow was mated naturally at least twice, at the first postweaning or post-treatment estrus and 12 to 24 hours later. Sows showing standing estrus 12 hours after the second mating were mated once more. Pregnancy diagnosis was made by ultrasonography 23 to 24 days postmating.

Bred sows were penned in individual crates throughout the gestation period. Sows received 2.0 to 2.2 kg of a commercial ration once daily until 30 days before parturition. The ration was then increased to 3.0 kg per sow per day, and was reduced to 2.5 kg per sow per day for the last 5 days of gestation. On the day of parturition, sows were offered 3.0 kg of a lactation diet containing 13.8 MJ per kg of digestible energy and 180 g per kg of crude protein. During lactation and from weaning to mating, the ration was gradually increased and sows were allowed to eat and drink ad libitum.

A total of 90 sows and their litters were used concurrently in this experiment. Litter sizes were standardized (eight or nine piglets) within 48 hours of parturition, and sows and piglets were penned in individual crates throughout lactation. Sows were randomly assigned to one of two groups. The Altrenogest Group (n = 29) received orally a daily dose of 20 mg of altrenogest for 5 consecutive days, starting the day after weaning (Day 1). The Control Group (n = 61) were not treated with altrenogest.

Reproductive parameters analyzed were estrus synchronization rate (ESR), WEI, WFEI, proportion of sows repeating estrus (RE), conception rate at first estrus (CR), litter size at farrowing, number of live born piglets, number of stillborn piglets, preweaning mortality, and weaned litter size. The ESR was calculated as the percentage of sows showing estrus 4 to 7 days after weaning (Control sows) or after treatment ended (Altrenogest Group).

In order to demonstrate adequate management of the herd, reproductive data for the 3 years previous to the experiment was evaluated.

The ESR, RE, and CR were compared between treatment groups using chi-square analysis. Means of reproductive performance parameters were compared using Student's t test.

Results

Measures of reproductive performance for the Control Group were comparable to those obtained for the herd during the previous 3 years (data not shown). The percentage of sows showing estrus Days 4 to 7 (8 to 11 days after weaning) was higher in treated sows (P < .05); however, there were no significant differences in WEI, WFEI, RE, or CR (Tables 1 and 2). The RE of the altrenogest-treated sows tended to be lower than that of the control group (P < .10). Litter size at farrowing, number of live born piglets, number of stillborn piglets, preweaning mortality, and weaned litter size were similar between groups.

Discussion

In this study, the percentage of treated sows showing estrus Days 4 to 7 after treatment ended was greater than the percentage of control sows showing estrus Days 4 to 7 after weaning. These results are consistent with the results of previous studies in which altrenogest was administered to weaned sows for 3 to 4 days.⁵ However, the ESR for treated sows in this study was lower than the rate observed in early weaned sows treated with progestagens for 7 days⁶ or 12 days³ and in postpubertal gilts treated with altrenogest for 18 days.⁷ The longer treatment periods in those studies may have accounted for the high synchronization rates recorded.

Other reproductive parameters analyzed in this study did not differ significantly between treatment groups (P > .05), although RE tended to be lower in the altrenogest-treated sows than in the control group (P < .10). Rate of RE is a parameter indicating reproductive failure in sows and is a measure of the efficiency of mating management. In breeding herds with "normal" reproductive performance, 8 to 14% of sows return to estrus after the first service,⁸ similar to what was observed in the control group in this study and comparable to data obtained during the previous 3 years in the herd (12.1%).

In previous reports, litter size was larger and there were more live born piglets in litters of sows treated with altrenogest for 3 days starting on the day of weaning⁵ or 7 days after weaning,⁶ compared to control sows. In those studies, body condition of the altrenogest-treated sows was better than that of untreated sows during the period from weaning to conception, and better embryo survival and more live born piglets might be attributed to nutritionally mediated advanced oocyte maturation, a concept described as nutritional "imprinting" of oocytes.⁹ Nutritional imprinting produces embryos with enhanced ability to develop and survive. However, in this study, the number of live born piglets was not greater in the sows treated with altrenogest than in the control sows.

Due to the commercial status of the herd that took part in this study, the number of animals in the Altrenogest Group was small. Future trials will include larger numbers of animals. It is important to note that altrenogest carries an extreme caution for people handling the product.

Implications

• Under the conditions of this study, administration of altrenogest was beneficial in synchronizing estrus of sows after their first litter.
• Further studies are needed to verify the positive effect of altrenogest and its safety for use in commercial herds.

References

1. Estienne MJ, Harper AF, Horsley BR, Estienne CE, Knight JW. Effect of P.G. 600 on the onset of estrus and ovulation rate in gilts treated with Regumate. J Anim Sci. 2001;79:2757-2761.

2. Tummaruk P, Lundeheim N, Einarsson S, Dalin AM. Effect of birth litter size, birth parity number, growth rate, backfat thickness and age at first mating of gilts on their reproductive performance as sows. Anim Reprod Sci. 2001;66:225-237.

3. Koutsotheodoros F, Hughes PE, Parr RA, Dunshea FR, Fry RC, Tilton JE. The effects of post-weaning progestagen treatment (Regumate^") of early-weaned primiparous sows on subsequent reproductive performance. Anim Reprod Sci. 1998;52:71-79.

*4. Tilton JE, Weigl R. Regumate treatments to overcome second litter production depression. 16^th Int Pig Vet Soc Congr. Melbourne, Australia; 2000:87.

*5. Baker DJ, Peter HR, Getting YG. Effect of Altrenogest on litter size in primiparous sows. Proc Brit Soc Anim Prod. 1994:171.

6. Bosch A. Utilization of zootechnical progestagen. Anaporc. 1998;179:97-104.

7. Martinat-Botte F, Bariteau F, Forgerit Y, Macar C, Poirier P, Terqui M. Synchronization of estrus in gilts with altrenogest: effects on ovulation rate and foetal survival. Anim Reprod Sci. 1998;39:267-274.

8. Tummaruk P, Lundeheim N, Einarsson S, Dalin AM. Repeat breeding and subsequent reproductive performance in Swedish Landrace and Swedish Yorkshire sows. Anim Reprod Sci. 2001;67:267-280.

9. Cosgrove JR. Nutrition/endocrine interactions. In: Wiseman J, Varley MA, Chadwick J, eds. Progress in Pig Science. Nottingham: Nottingham University Press; 1997:35-36.

* Non-refereed references.