Document Type

Thesis - Open Access

Award Date

2020

Degree Name

Master of Science (MS)

Department

Animal Science

First Advisor

Jeffrey Clapper

Keywords

IGF, LH Ovugel, Pituitary, Swine, Triptorelin

Abstract

Triptorelin is a gonadotropin releasing hormone agonist that has been shown to be effective in weaned sow single fixed time artificial insemination protocols. Administration of triptorelin 96 h after weaning has been shown to be effective in synchronizing sows to be inseminated one time 24 h later without reducing pregnancy rate or the number of pigs born. In the current experiment, 23 crossbred gilts (249 d, 123 kg) were administered an intramuscular injection of PG600. Nine days after PG600 administration, gilts were fed 15 mg of altrenogest once daily for 16 d. Twelve gilts (OVU) were administered 200 μg triptorelin 96 h after the last altrenogest feeding. A single artificial insemination was then performed regardless the expression of estrus 126 h after the last altrenogest feeding. Eleven gilts (CON) were inseminated upon the expression of standing estrus and received a second insemination 24 h later. Blood was collected on d 0 (day of triptorelin administration), 1, and 2 after the administration of triptorelin for the measurement of serum concentrations of estrogen and progesterone by RIA. Estrus detection was performed daily beginning 3 d following the last altrenogest administration and ended 7 d after the last altrenogest administration. Gilts were slaughtered on d 33 when reproductive tracts were collected. Reproductive tracts were evaluated for the number of fetuses in the uterus and the number of CL on the ovary. No differences (P >0.05) were found in pregnancy rate, number of fetuses, number of CL, and the ratio of fetuses to CL in all animals. When non-pregnant gilts were removed from the analysis there was a trend (P=0.08) for the CON group to have a greater ratio of fetuses to CL. Expression of standing estrus was also greater (P< 0.05) in the CON group than OVU group. No differences (P >0.05) were found in serum concentrations of estrogen between OVU and CON gilts. The CON group’s expression of estrus occurred around the time when progesterone was at the lowest in the group. The OVU had its lowest serum concentration of progesterone earlier than CON group. This may indicate that the OVU group could have ovulated earlier than the CON group. Data from the first experiment has demonstrated that even though conception rates of fixed timed AI protocols involving GnRH agonists are similar to standard AI, the conception rate versus ovulation rate may show differences in the two protocols. When comparing the ovulation rate with conception rate, our experiment has shown that GnRH agonists, accompanied by a single fixed timed AI, may not be effective in maximizing the number of conceptuses in gilts. Many of the gilts in this experiment failed to become pregnant even though standing estrus was exhibited in the CON group. Anterior pituitary and blood samples from these gilts were collected to determine serum concentrations of insulin like growth factor (IGF) and luteinizing hormone. Anterior pituitaries were also used to determine the expression of IGF receptor, gonadotropin releasing hormone (GnRH) receptor, luteinizing hormone beta (LH-β), IGF binding protein -2, 3, and 5. Anterior pituitaries and serum samples were collected from 15 pregnant and 8 non-pregnant gilts on d 33 after AI. Serum concentrations of estradiol and progesterone and AP concentrations of LH and IGF-1 were determined by RIA. Relative expression of GnRHR, LH-β, IGF-1, IGFBP-2, IGFBP-3, and IGFBP-5 were determined using real time reverse transcriptase PCR. Fold changes in relative expression were determined using the Relative Expression Software Tool. Non-pregnant gilts were assumed to be undergoing the luteal phase of their reproductive cycle. Our data supported this because no differences (P >0.05) were determined in serum concentrations of progesterone or estradiol between non-pregnant and pregnant gilts. Mean AP concentrations of LH were greater (P<0.05) in the pregnant gilts than non-pregnant gilts. Mean AP concentrations of IGF-1 were not different (P >0.05) between pregnant and nonpregnant gilts. Mean relative expression of LH-β was .8 fold lower (P< 0.05) and IGFBP- 2 tended to be 0.8 fold lower (P=0.095) in pregnant gilts compared to non-pregnant gilts. No differences were found (P >0.05) between pregnant and non-pregnant gilts in relative expression of AP GnRHR, IGF-1, IGFBP-3, and IGFBP-5. Data from the second experiment have shown that changes in multiple endocrine factors, such as LH and the IGF system, may play a crucial part in maintaining early pregnancy but further investigation is needed.

Format

application/pdf

Number of Pages

100

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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