Crossbred ewes (1/2 Dorset, 1/4 Rambouillet, and 1/4 Finnsheep) from a flock being selected for spring fertility, defined as ability to lamb following ram exposure in May and June in Virginia (37 degrees N latitude), were used to study the duration of the seasonal anestrus. In the first 3 yr of the study (1992, 1993, and 1995), mature ewes were divergently selected based on EBV for fertility, a...

In two experiments, 16 Booroola-Assaf and 35 Assaf ewe-lambs were actively immunized at 5 months of age against recombinant ovine placental lactogen (oPL). At 9 months of age, the ewe-lambs were mated for the first time and then introduced into a frequent mating-system. Anti-oPL antibody titers, reproductive performance, maternal serum levels of oPL during pregnancy, lamb birth weight and milk ...

Merino ewes (n = 300) grazing on sparse annual pasture and supplemented with hay were given a CIDR (controlled internal drug release) device to synchronise oestrus. Ewes in Groups 1 and 2 received 750 g/head of lupin grain each day for 9 days prior to the expected oestrus and ewes in Group 3 received a hay-only supplement. After joining ewes in Group 1 continued to receive the lupin supplement ...

to evaluate effects of melatonin treatment in combination with progestagen on reproductive performance of ewes during the anestrus period, 60 ewes were used and allocated randomly in two groups during the anoestrous peiod: all ewes synchronize by cidr and receive pmsg (600 iu) on the day of cidrs removal. ewes in group treatment( n=30 ) resived melatonin implants(18 mg) 35 days before inserting...

Suffolk and Targhee ewes (30 each) with single or twin lambs were used in four periods beginning in late gestation and continuing through weaning to evaluate breed differences in milk production, lamb BW, and DMI by ewes and lambs. In Periods 1 (late gestation) and 2 (early lactation), ewes (Period 1) and ewes with lambs (Period 2) were individually penned, fed .45 kg of barley x ewe(-1) x d(-1...

The peri-parturient period is crucial for controlling worms as the acquired immunity of ewes is disrupted, resulting in an increase in faecal worm egg counts. Two hypotheses were tested in this experiment - that ewes bred for worm resistance would have lower faecal worm egg counts than unselected control ewes, during late pregnancy and lactation, under similar but separate grazing areas; and al...

Genetic parameters for a subjective milk score given to ewes within 24 h of parturition were estimated to determine the usefulness of milk score as a selection trait to improve milk production, which influences total litter weight weaned. Heritability of milk score and the genetic correlation of milk score with litter weight weaned were estimated by REML separately for four sheep breeds, Rambou...

Multiparous Suffolk and Suffolk-cross ewes were randomly allotted to treatments within breed and year to measure effects of ram exposure, during transition from anestrus to breeding activity, on reproductive performance. Treatments were: 1) ewes joined with two mature vasectomized Rambouillet rams for 15 d before breeding (DC), 2) ewes maintained across a net wire fence from two vasectomized ra...

Mature ewes (12 per group) were given prostaglandin F20t (PG; 10 mg intramuscularly) on day 10 of an estrous cycle, to regress corpora lutea, or on day 16, after natural corpus luteum regression. Ewes treated on day 10 or 16 were in estrus on day 12 or 17, respectively. The PG-treated and untreated ewes were mated at estrus and necropsied 2 hr later. Sperm were counted in the oviducts, the uter...