Document Type

Thesis - University Access Only

Award Date

2011

Degree Name

Master of Science (MS)

Department / School

Animal Science

Abstract

During the bovine estrous cycle, uterine pH is decreased at estrus, but remains neutral during the luteal phase. These changes in uterine pH are important for sperm transport and early embryonic survival. Uterine pH may be regulated through activity of Na+/H+ exchangers. Additionally, excess protein and sulfur intake prevented the normal increase in uterine pH during the luteal phase. Therefore, two experiments were conducted to determine the expression of Na+/H+ exchanger isoforms (NHE) NHEl, NHE2, NHE3 and NHE4 in bovine endometrium around estrus and a third experiment was conducted to determine the effects of excess nitrogen and sulfur intake on uterine pH throughout the luteal phase. In exp. 1 and 2, cows (n = 40 and n = 28, respectively) were synchronized with the PG 6-day CIDR protocol: PGF2a on d -9, GnRH and insertion of a CIDR on d -6 and PGF2a and CIDR removal on d 0. Cows were blocked by follicle size at time of CIDR removal, and uterine biopsies were collected at 0, 12, 24, 36, 48 or 60 h after CIDR removal in exp. 1 and at 60, 72, 84 or 96 h after CIDR removal in exp. 2. RNA was extracted and relative mRNA levels were determined by real-time RT-PCR. In exp. 1, among cows that exhibited estrus, expression of NHEl was decreased at 48 h compared to h O(P = 0.05), NHE2 expression was decreased at 12, 24, 36, 48 and 60 h compared to h O (P < 0.01 ), and NHE4 expression was decreased at 36, 48 and 60 h compared to h O (P < 0.02). Among cows that did not exhibit estrus, expression of NHEl, NHE2 and NHE4 did not change (P > 0.09, P > 0.38 and P > 0.07, respectively). There was no estrus by time interaction on expression ofNHE3 (P > 0.29). In exp. 2, there was no effect of estrus, time or an estrus by time interaction on expression of NHEl (P = 0.85, P > 0.39 and P > 0.25, respectively) or NHE4 (P = 0.10, P > 0.13 and P > 0.33, respectively). There was an estrus by time interaction (P < 0.01) on expression of NHE2. Among cows that exhibited estrus, expression ofNHE2 was increased at h 72 compared to h 60, 84 or 96 (P < 0.01). Among cows that did not exhibit estrus, expression' did not change (P > 0.61). There was an estrus by time interaction (P = 0.02) on expression ofNHE3, with expression being increased at h 84 among cows that did not exhibit estrus. Among cows that did exhibit estrus, expression ofNHE3 did not change (P > 0.86). In the third experiment, Holstein (n = 15) and Angus-cross (n = 5) heifers (337.5 ± 8.4 kg ofBW) were randomly assigned to 1 of 4 diets: control (CON; 13.4% CP and 0.17% HS); high nitrogen (HN; CON plus urea supplement to achieve 18.5% CP);high sulfur (HS; CON plus calcium sulfate to achieve 0.43% HS); or both high nitrogen and sulfur (HNS). Diets were individually fed at 2.6% of BW on a dry matter basis using Calan gates and estrus was synchronized to occur on d 13. Blood samples were collected on d -2 and daily (d 1 to 28) at 1400 h to determine concentrations of plasma urea nitrogen (PUN), sulfate (d 1, 4, 8, 12, 16, 20, 24 and 28), and progesterone. Uterine pH was measured on d 16, 20, 24, and 28 (d 3, 7, 11, and 15 of the estrous cycle). There was a treatment by time interaction (P < 0.01) on concentrations of PUN. Starting on d 3, concentrations of PUN were increased in HN and HNS compared to CON and HS (P < 0.01). Concentrations were not different between HN and HNS (P > 0.05) or between CON and HNS (P > 0.05). There was an effect of treatment (P < 0.01) on concentrations of sulfate, with concentrations being increased in HS compared with CON, HN, and HNS (P < 0.01), with HNS increased compared to CON (P < 0.01) and HN (P < 0.01). In addition, concentrations of sulfate were increased on d 4 compared to d 8 (P = 0.04) and 16 (P < 0.01) and were decreased on d 8 and 16 compared to d 24 (P = 0.01 and P < 0.01, respectively) and 27 (P < 0.05 and P < 0.01, respectively), but there was no treatment by time interaction (P = 0.81 ). Uterine pH was increased in HN and HNS compared to CON (P < 0.02), while HS was intermediate (P > 0.11). There was no effect of time (P = 0.26) or a treatment by time interaction (P = 0.71) on uterine pH. In summary, expression ofNHEl, NHE2 and NHE4 decreased after CIDR removal among cows that exhibited estrus, but did not change among cows that did not exhibit estrus. Expression of NHE2 increased at h 72 after CIDR removal compared to h 60 among cows that exhibited estrus, but did not change among cows that did not exhibit estrus. Furthermore, expression of NHE3 was increased at h 84 after CIDR removal compared to h 60 among cows that did not exhibit estrus, but did not change among cows that did exhibit estrus. During the luteal phase, excess intake of nitrogen resulted in an increase in uterine pH compared to controls and excess intake of sulfur was intermediate.

Keywords: uterine pH, Na+llr exchanger, nitrogen, sulfur, bovine

Library of Congress Subject Headings

Cattle -- Reproduction

Estrus

Format

application/pdf

Number of Pages

157

Publisher

South Dakota State University

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