Document Type

Thesis - Open Access

Award Date

2021

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Julie Walker

Second Advisor

George Perry

Abstract

The management of heifers can have lifetime effects on their reproductive success and efficiency. Nutrition is one of the management factors that can influence steroid hormone production, oocyte development, embryo development, and uterine histotroph, thus affecting heifers’ reproductive efficiency. Therefore, the objectives of the following studies were to evaluate the impact of nutritional changes prior to and after Artificial Insemination (AI) on plasma cholesterol concentrations, and uterine mineral concentrations (Chapter 2) and the impact of nutritional change after AI on uterine mineral concentrations, steroid hormone production, and circulating metabolites (Chapter 3). In experiment 1 (Chapter 2), beef heifers (n = 79) were randomly assigned to two treatment groups of High (162% of NEm) and Low (90% of NEm) diets for 30 days prior to AI. Heifers were then randomly re-assigned at time of AI to new treatments of High (148% of NEm) and Low (81% of NEm) diets, therefore creating four Pre- by Post-AI treatments: High-High (H-H; n = 20), High-Low (H-L; n = 20), Low-Low (L-L; n = 20), and Low-High (L-H; n = 19). Post-AI diet continued for 7 or 8 days until uteri were flushed for embryo recovery. Blood samples were collected on d -3, -2, -1, 0 (day of AI), 1, 3, 5, 7, and 8 for analysis of circulating cholesterol concentrations using a colorimetric assay. Minerals (Mg, Al, P, S, K, Ca, Cu, Zn, Se, and Fe) were analyzed in uterine flushes collected on day of embryo recovery (d 7 or 8) using ICP-MS. Plasma cholesterol concentrations were analyzed using repeated measures using MIXED procedures in SAS. Uterine mineral concentrations were analyzed using MIXED procedures in SAS. Cholesterol concentrations were influenced by time (P < 0.0001) with concentrations increasing after estrus until d 5, concentrations than decreased to d 7 and 8. Pre-AI by Post-AI diet interaction tended to impact cholesterol concentrations (P = 0.10). There was an effect of embryo recovery on Mg (P < 0.04), Al (P < 0.01), S (P < 0.01), K (P < 0.01), and Ca (P < 0.01), with decreased mineral concentrations when an embryo was recovered. Pre-AI diet did not influence uterine mineral concentrations (P > 0.10); however, Post-AI diet influenced S (P < 0.02) and Ca (P = 0.03). High heifers had elevated S and Ca concentrations in comparison to Low heifers. Pre-AI diet by embryo recovery interaction impacted S concentrations. Post-AI diet by embryo interaction influenced P (P < 0.03), Zn (P = 0.02), and Se (P = 0.02). Pre-AI by Post-AI diet by embryo interaction influenced uterine Mg concentrations (P < 0.05). There was an overall tendency for a Pre-AI by Post-AI diet by embryo recovery interaction on S (P = 0.09), Cu (P = 0.07), and Fe (P = 0.09). In experiment 2 (Chapter 3), heifers (n = 50) were assigned randomly to two treatments groups of High (161.5% of NEm) or Low (77.5% of NEm) diets following AI until uteri were flushed for embryo recovery 14 days after AI. Blood samples were collected on d -3, 0 (AI), 3, 6, 9, 12, and 14. Heifer weights and uterine mineral concentrations were analyzed using MIXED procedure in SAS. Circulating concentrations of progesterone (P4), non-esterified Fatty Acids (NEFA), glucose, protein, and cholesterol were analyzed as repeated measures using the MIXED procedure of SAS. Dietary treatment impacted NEFA concentrations (P < 0.01), with Low heifers having elevated NEFA concentrations in comparison to High heifers. Diet treatment by time interaction influenced NEFA concentrations (P < 0.01) with concentrations increasing in Low heifers but remaining relatively constant in High heifers. Embryo by time interaction impacted glucose concentrations (P < 0.02): heifers with an embryo recovered had elevated glucose concentrations beginning on d 3 in comparison to heifers with no embryo recovered. Protein concentrations tended to be influenced by diet treatment by time interaction (P = 0.07). Cholesterol concentrations were affected by diet by time interaction (P < 0.01), with Low heifers having elevated cholesterol concentrations beginning on d 3 in comparison to High heifers. Diet treatment by embryo recovery by time tended to influence P4 concentrations (P < 0.06), with High heifers with no embryo having the greatest P4 concentration on d 12. Uterine Mg (P = 0.02), S (P = 0.01), and Ca (P = 0.08) concentrations decreased when an embryo was recovered. Uterine Mn (P = 0.06) concentrations increased when an embryo was recovered. Dietary treatment tended to effect Fe concentrations (P = 0.09), with High heifers having elevated Fe concentrations compared to Low heifers. In conclusion, changing the nutrient status prior to and after AI did not impact plasma cholesterol concentrations; however, nutritional changes after AI influenced circulating NEFA, cholesterol, glucose, and protein concentrations. Additionally, when an embryo was recovered uterine mineral concentrations were affected.

Library of Congress Subject Headings

Heifers -- Nutrition.
Heifers -- Artificial insemination.
Heifers -- Reproduction.
Beef cattle.
Metabolites.
Steroid hormones.

Number of Pages

149

Publisher

South Dakota State University

Download

Included in

Beef Science Commons

Share

COinS
 

Rights Statement

In Copyright