a number of 5558 lambing records of 2245 mehraban ewes, collected during years 1995 to 2010 were utilized to estimate the variance components and heritability for the number of lambs per lambing,  making use of b-spline random regression models. the fixed factors affecting the studied trait were identified using general linear model analysis as well as sas software, where flock-year-season and ...

Procedures have been developed to produce consistent increases in ovulation rate in Merino ewes by immunization against the steroids, androstenedione, testosterone and oestrone. The procedures were based on experiments in the field over the period 1978-1981 using groups of 50 ewes for each treatment. The method uses selected steroid-human serum albumin conjugates, together with DEAEdextran adju...

Merino and crossbred ewes were used to evaluate whether previously ram exposure in late winter could improve the response to further progestagen oestrus synchronization treatment in terms of luteal function and fertilization rate. We used 56 adult Merino and crossbred ewes randomly allocated in two groups, control (C; n= 27) and Male Effect (ME; n= 29), which had been isolated from rams for at ...

One hundred and fifty ewes with lifetime records of ovulation rate and lambing were divided into two groups on the basis of age, live weight and reproduction index (calculated from reproductive performance data). Both groups were synchronised in oestrus with progestagen sponges inserted for 14 days. At sponge removal one group received no PMSG while the other group received 400 i.u. PMSG. Eight...

The effects on fertility of single or double treatments with the prostaglandin analogue ICI 80996 were studied in a flock of Merino ewes in an artificial insemination programme. The number of ewes lambing in the double treatment group and the untreated group was significantly higher (P<0.001) than the number of ewes lambing in the single treatment group. However there were large day to day vari...

the number of lambs sold per ewe mated in the breeding flock has a considerable impact on sheep operation profitability. this depends primarily on fertility, prolificacy (# of lambs), and lamb survival, mothering ability, milk production of the ewe and lamb growth rate. optimal reproduction does vary by environment and management system – some sheep operations don’t want a lambing rate over 200...

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 weigh...

The genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population were estimated by applying the Average Information Restricted Maximum Likelihood method to an animal model. Data from a flock supported by the Programa de Melhoramento Genético de Caprinos e Ovinos de Corte (GENECOC) were used. The traits studied included birth weight (BW), weaning weight (...