Date of Graduation

8-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Animal Science (PhD)

Degree Level

Graduate

Department

Animal Science

Advisor/Mentor

Rorie, Rick W.

Committee Member

Burke, Joan M.

Second Committee Member

Donoghue, Daniel J.

Third Committee Member

Coffey, Kenneth P.

Keywords

Artificial Insemination; Ewe; Ram; Semen Extender

Abstract

Three studies were conducted to improve simple artificial insemination in sheep using chilled extended semen and evaluate methods to predict fertility in ewes. The first study evaluated the effect of semen extenders and storage temperature on motility parameters of ram semen stored for up to 72 h. Single semen collected from each ram was divided into four parts and extended using four extenders: milk, TRIS, TEST, and CJ-2, diluted to 600 million sperm/ml and loaded into 0.25 ml straws for storage at 4 and 15° C. Most of the CASA motility parameters were higher after extension and storage at 4 compared with 15° C (P < 0.05). Ram semen stored using milk or TRIS based extenders at 4° C maintained similar sperm motility parameters but both were higher compared with TEST or CJ-2 extenders after storage for up to 3 d (P < 0.05). The second study evaluated the effects of different combinations of extenders, ethylene glycol (EG), egg yolk and penicillamine, hypotaurine and epinephrine (PHE) on ram sperm motility parameters during storage. Semen electroejaculated from each ram was distributed across treatment combinations consisting of either TRIS or milk extenders supplemented with 5 or 20% (v/v) egg yolk, ± EG, and ± PHE. Milk extender supplemented with 1% EG, PHE and either 5 or 20% egg yolk can protect sperm cells better than other extender and supplement combination after storage at 4° C for up to 72 h. The third study was conducted to correlate serum AMH and lambs born with estimated breeding values determined through National Sheep Improvement Program for reproductive performance (NLB or number of lambs born; NLW or number of lambs weaned; MWWT or maternal weaning weight; and the Katahdin index) and WWT or weaning weight. Additionally, correlation between AMH quartiles and lambs born after fall versus summer breeding was determined. There was no correlation between serum AMH and EBVs for NLB, NLW, MWWT, WWT and the Katahdin index in Katahdin ewes (P > 0.05). Ewes in the lowest quartile (Q1) had lower number of offsprings born from summer breeding compared with ewes in other AMH quartiles.

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