Effect of altrenogest treatment before weaning on reproductive performance and production efficiency in primiparous and multiparous sows

Abstract

Background: Most sows will experience negative energy balance during lactation resulting in impaired follicular development. This study aimed to treat 28-day lactating sows with altrenogest (ALT) to suppress follicle enlargement during lactation, and to assess the estrus and reproductive performance post-weaning.

Methods: In this study, we conducted two trials. In trial 1, we monitored the follicular development of lactating sows including 10 primiparous sows and 10 multiparous sows during the whole lactation to confirm the ALT administration time. In trial 2, a total of 42 primiparous and 111 multiparous sows were allocated to three treatments: Ctrl (control group, n = 51): no treatment; TAI (timed artificial insemination group, n = 51): sows were injected with equine chorionic gonadotropin (eCG) after weaning 24 h and gonadotropin-releasing hormone (GnRH) when they expressed estrus; and AT-TAI (ALT treatment-timed artificial insemination group, n = 51): base on the process of TAI group, the sows were fed with 20 mg ALT per day before weaning 10 days. All sows were artificially inseminated twice at 12 h and 36 h after estrus. The follicle size changes and serum hormone levels were explored in this process.

Results: Although the follicle size of multiparous sows was larger than primiparous sows during the whole lactation (P < 0.05), similar change trends of follicle size were observed in primiparous and multiparous sows. Meanwhile, the FSH, LH and E₂ levels of multiparous sows were higher than primiparous sows. The ALT treatment significantly inhibits the increase in follicle size (P < 0.05) and reduces the serum levels of FSH, LH and E₂ (P > 0.05). Additionally, ALT treatment increases estrus concentration and the preovulatory follicle size (P < 0.05), meanwhile, it delays the weaning-to-estrus interval (WEI, P < 0.001). However, the estrus rate, pregnancy rate, total pigs born and born alive did not differ between treatments (P > 0.05).

Conclusions: There were significant differences in the size of follicles in the lactation between primiparous and multiparous sows. ALT treatment during the last ten days of lactation concentrated estrus expression leading to higher work efficiency of breeder in batch production, however, with no improvement in reproductive performance.

Keywords: Altrenogest; Estrus concentration; Follicle development; Lactation; Weaning sows.

Fig. 1

Schematic of experimental design with weaning sows in trial 2

Fig. 2

Follicular development and hormone levels of sows during lactation. Representative images of lactation ovary B-ultrasonography of primiparous sows (n = 10) (A) and multiparous sows (n = 10) (B). The yellow triangles point to the follicles. The upper left corners of each image represent the time and the upper right corners represent the average follicle diameter on that day. (C) The changing curve of sows follicle size during lactation. Only the daily size of primiparous and multiparous sows was compared. The changing curves of sows serum hormone FSH (D), LH (E) and E₂ (F) during lactation (n = 6). * P < 0.05, ** P < 0.01, *** P < 0.001

Fig. 3

Follicular development and hormone levels of sows during ALT treatment. Representative images of lactation ovary B-ultrasonography of primiparous sows (A) and changing curves (B) during ALT treatment (n = 5). Representative images of lactation ovary B-ultrasonography of multiparous sows (C) and changing curves (D) during ALT treatment (n = 5). The yellow triangles point to the follicles. The upper left corners of each image represent the time and the upper right corners represent the average follicle diameter on that day. The changing curve of sows serum hormone FSH (E), LH (F) and E₂ (G) during ALT treatment (n = 6), * P< 0.05, ** P< 0.01 (AT-TAI versus Ctrl); ^#P < 0.05, ^##P< 0.01 (AT-TAI versus TAI); NS: no significant

Fig. 4

The estrus distribution in three groups after weaning (weaning day was considered D0)