WEST VIRGINIA SHEPHERD’S SHORT COURSE Camp Pioneer, December 2010 INDUCTION OF ESTRUS AS A REPRODUCTIVE MANAGEMENT TOOL IN ANESTROUS EWES Keith Inskeep Division of Animal and Nutritional Sciences West Virginia University Morgantown, West Virginia, USA

Seasonality of Reproduction in Sheep Ewes bred Spring Lambing Fall

Proposed Shift from Spring Lambing to Fall Lambing Breeding Lambing Market

Goals for Changing Lambing Season Improved Prices Fewer Losses to Predators Lower Feed Costs Improved Profits

Length of Breeding Season Short: Southdown Cheviot and Border Leicester Long: Dorset, Rambouillet, Merino and Finn-sheep Intermediate: Hampshire and Suffolk Year- round: Katahdin, Barbados Blackbelly, Virgin Island White and West African Hair Sheep

Heritability of Length of Breeding Season Estimated as h 2 = 0.26 or 26% Greater than for most reproductive traits D.R. Notter at Virginia Tech – Selection for May breeding - increased success from 33% to over 80% in non-lactating ewes in nine years Used no treatment except ram introduction

Figure 2. Diagram of the regulation of seasonal breeding in the ewe by photoperiodic cues translated by the pineal gland, hypothalamus, anterior pituitary and ovary.

Figure 1. Patterns of concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol-17  (E 2 ), progesterone (P 4 ), and prostaglandin F 2  in peripheral blood of the ewe during the estrous cycle. LH E2E2 P4P4 FSH PGF 2 

Approaches to induce fertile estrus during seasonal anestrus  “The ram effect”: Abrupt introduction of novel rams  Interrupts seasonal anestrus (Underwood, 1944) –Typically causes ovulation (Schinckel, 1954) without estrus and short luteal phase, then ovulation without estrus and a normal luteal phase, then ovulation accompanied by estrus (18 to 23 days after rams are introduced

Effect of breed on the response to RI (Adapted from Nugent et al., 1988)

Treatment of rams with melatonin increased the percentage of ewes ovulating (Rosa et al., 2000)

Sources of variation in the ram effect response Nutritional/body condition status of ewes (Knights et. al., unpublished)

Effectiveness of Intravaginal Progesterone Inserts (CIDRs) and Follicle Stimulating Hormone (FSH) to Induce Synchronized Estrus and Increase Lambing Rates in Anestrous Ewes in Combination with Ram Effect

Materials and Methods CIDR removal and ram introduction CIDR insertion CIDR insertion FSH Estrus observed every 12 h ultrasound pregnancy diagnosis Blood sampled every 2 d for progesterone Ram removal Group 1 = CIDR 12 days + (n=73) Group 2 = CIDR 12 days + FSH (n=71) Group 3= CIDR 5 days + FSH (n=77) Control = no CIDR + no FSH (n=73)

Distribution of Estrous Response

Conception Rate to First Service a b b b

Percentage of Ewes Lambing to Two Services

Overall Prolificacy

Cumulative Lambing Distribution

Effect of lactation status on fertility of ewes during anestrus. Knights et al., 2002

Treatment with Estradiol Benzoate to Enhance Effect of Rams and Progesterone in Weaned or Lactating Ewes Pregnancy Rates (%) N First Service Second Service Lambed Lambing Rate Experiment 1. Half received 30 µg of estradiol benzoate 24 h after insert removal and ram introduction. Weaned Lactating Lambing rate was greater in ewes treated with estrogen, (1.1) than in ewes receiving corn oil (0.8). Experiment 2, Received either 0, 15 or 30 µg of estradiol benzoate 24 h after insert removal and ram introduction. Weaned Lactating Treatment with estrogen increased pregnancy rate to first service and ewes lambing in weaned, but not in lactating ewes.

Ewe:Ram Ratio Synchronized estrus requires ewe:ram ratios not to exceed 18:1 Fertility did not differ at ratios of 6, 9, or 12 ewes per ram. Ram lambs and yearling rams performed equally in 3 ram lots and could handle 18 ewes per ram. In single ram lots, ram lambs were less able to service 18 ewes than yearling rams, and even yearling rams had less success with 18 than with 12 ewes.

Pregnancy data for a flock of purebred Dorset ewes synchronized out-of-season with a 5-day CIDR-G followed by ram introduction – May and June 2010 VariableValue Total number of ewes98 Percent ewes lambing, % First service period54 Second service 19 Third 4 Total 77

Pregnancy data for a flock of purebred Dorset ewes synchronized out-of-season with a 5-day CIDR-G followed by ram introduction – May and June 2010 VariableValue Prolificacy First service period 1.73 Second service period 1.82 Third service period 1.30 Overall 1.67 Open at ultrasound, %11 Total potential lambs lost, %19.5

Pregnancy data for a flock of grade Katahdin ewes synchronized out-of-season with a 5-day CIDR-G + PGF followed by ram introduction – May and June 2010 VariableValue Total number of ewes77 Ewes lambing, % First service period47 Second service 31 Third 13 Did Not Lamb(%) 9

Pregnancy data for a flock of grade Katahdin ewes synchronized out-of-season with a 5-day CIDR-G + PGF followed by ram introduction – May and June 2010 VariableValue Prolificacy First service period 1.61 Second service period 1.38 Third service period 1.20 Overall 1.47

Differences Exist for Operations with Fall- Lambing Versus Spring-Lambing Production VariableFall Lambing Spring Lambing Pregnancy Rate (ewes lambing/ewes exposed) 75%89% Lamb Crop (lambs born/ewe lambing)159%170% Mortality Rate6%10% Average Market Price$0.93$0.75 Average Cost/lb of Lamb Produced$0.58$0.51 Profit/lb of Lamb Produced$0.33$0.28

Take Home Messages Ram/Buck introduction is most valuable tool. Progestogen pretreatment (CIDR) is second tool. Assess body condition score before breeding Early re-breeding means early weaning – lactating ewes do not respond well to techniques that work in dry ewes – Exception Dr. Notter’s composites selected for May breeding; some of them cycle during spring lactation Ewe lambs do not breed well out-of-season

QUESTIONS?