Biomaterial Database

Reproductive performance of ewe lambs from ewes from different selection practices with or without induced estrus. 2001

J N Stellflug, and P G Hatfield, and M C Wulster-Radcliffe, and J W Walker

USDA-ARS US Sheep Experiment Station, Dubois, ID 83423, USA. tellflug@pwa.ars.usda.gov

Three groups of ewe lambs born in May (experiment 1; n=211) or April (experiment 2; n=174) were used to evaluate the effects of selection line and induction of estrus on pregnancy rate. Experiment 1 was a single factor experiment with induction of estrus as the main effect. In early December, May-born Targhee (n=82) and Rambouillet x Targhee (n=129) ewes were randomly assigned within body weight to one of two treatment groups: control or induction of estrus. Experiment 2 was designed in a 2x2 factorial array with the main effects of induction of estrus or selection line. In early November, April-born Targhee lambs (n=174) from two distinct selection lines were either treated as controls or received an estrus induction treatment. The two lines included an unselected control line of randomly bred ewes and a line that had been selected since 1976, based on the weight of lamb weaned. Ewes from each line were randomly assigned within body weight to one of the treatment groups. In experiments 1 and 2, estrus was induced using MAP pessaries. Pessaries were inserted for 12 days. At the time of pessary removal, ewe lambs received 400 IU eCG i.m. All ewe lambs were bred in multi-sire pens. Pregnancy rate and fetal numbers were determined either by lambing data or real-time ultrasound. Body weight, lambing date and fetal numbers were analyzed by GLM, and remaining variables were analyzed by CATMOD. For experiment 1, estrus induction increased (P<0.01) pregnancy rates (61 versus 31%) and number of fetuses estimated by real-time ultrasound (79 versus 35%) compared to control ewe lambs. Pregnancy rate and fetal number were increased (P<0.01) for the 1st year compared to the 2nd year. For experiment 2, estrus induction tended to increase (P<0.07) pregnancy rate, and pregnancy rate differed (P<0.01) between selection lines. Estrus induction increased (P<0.05) fetal numbers (0.96) compared to controls (0.77). Fetal numbers were greater (P<0.01) for the selected line (1.06) compared to random bred controls (0.67). Average date of lambing was earlier in both experiments for the estrus-induced ewe lambs compared to controls. These results indicate that induction of estrus can be recommended if increased reproduction is desired for ewe lambs.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D010570	Pessaries	Devices worn in the vagina to provide support to displaced uterus or rectum. Pessaries are used in conditions such as UTERINE PROLAPSE; CYSTOCELE; or RECTOCELE.	Pessary
D011247	Pregnancy	The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.	Gestation,Pregnancies
D012098	Reproduction	The total process by which organisms produce offspring. (Stedman, 25th ed)	Human Reproductive Index,Human Reproductive Indexes,Reproductive Period,Human Reproductive Indices,Index, Human Reproductive,Indexes, Human Reproductive,Indices, Human Reproductive,Period, Reproductive,Periods, Reproductive,Reproductive Index, Human,Reproductive Indices, Human,Reproductive Periods
D001835	Body Weight	The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.	Body Weights,Weight, Body,Weights, Body
D001947	Breeding	The production of offspring by selective mating or HYBRIDIZATION, GENETIC in animals or plants.	Breedings
D004971	Estrus	The period in the ESTROUS CYCLE associated with maximum sexual receptivity and fertility in non-primate female mammals.
D005260	Female		Females
D006063	Chorionic Gonadotropin	A gonadotropic glycoprotein hormone produced primarily by the PLACENTA. Similar to the pituitary LUTEINIZING HORMONE in structure and function, chorionic gonadotropin is involved in maintaining the CORPUS LUTEUM during pregnancy. CG consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is virtually identical to the alpha subunits of the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity (CHORIONIC GONADOTROPIN, BETA SUBUNIT, HUMAN).	Chorionic Gonadotropin, Human,HCG (Human Chorionic Gonadotropin),Biogonadil,Choriogonadotropin,Choriogonin,Chorulon,Gonabion,Human Chorionic Gonadotropin,Pregnyl,Gonadotropin, Chorionic,Gonadotropin, Human Chorionic
D000282	Administration, Intravaginal	The insertion of drugs into the vagina to treat local infections, neoplasms, or to induce labor. The dosage forms may include medicated pessaries, irrigation fluids, and suppositories.	Administration, Vaginal,Drug Administration, Vaginal,Instillation, Vaginal,Intravaginal Administration,Vaginal Drug Administration,Vaginal Administration,Administration, Vaginal Drug,Administrations, Intravaginal,Administrations, Vaginal,Administrations, Vaginal Drug,Drug Administrations, Vaginal,Instillations, Vaginal,Intravaginal Administrations,Vaginal Administrations,Vaginal Drug Administrations,Vaginal Instillation,Vaginal Instillations