Prediction of the performance of synthetic sheep strains utilizing Finnsheep and native sheep breeds in Egypt

This investigation was carried out to estimate individual and maternal heterotic components for ewe productivity traits to enable predicting the performance of synthetics including local (Rahmani (R) and Ossimi (O)) and Finn (F) inheritance. Reproduction performance traits studied were number of ewes conceived (ECJ), number of lambs born (LBJ), number of lambs at four months of age (L4J), kilograms born (KBJ) and kilograms at four months of age (K4J), all being per ewe joined, and number of lambs born (LBL), number of lambs at four months of age (L4L), kilograms born (KBL) and kilograms at four months of age (K4L), all being per ewe lambed. Results indicate an expected increase of 0.32, 0.19, 0.50 and 0.27 in LBJ, L4J, LBL and L4L for F.R and 0.32, 0.23, 0.59 and 0.40 in the same traits for F.O after two generations of inter se mating, respectively. For FR.R and FO.O the improvements were (0.18, 0.18), (0.13, 0.15), (0.22, 0.28) and (0.15, 0.22) in LBJ, L4J, LBL and L4L, resp. It can be concluded that introducing the F to the local subtropical sheep in Egypt would substantially improve their reproductive performance whether for implementationat the small farmer level (quarter F) or at higher intensification level (half F). Index words: Finnsheep, Rahmani, Ossimi, crossbreeding, heterosis, synthetics, fertility, prolificacy, ewe productivity


Introduction
In 1974, the Egyptian Ministry of Agriculture (MOA) started a crossbreeding program to improve the productivity of two native sheep breeds through crossing with the prolific Finnsheep (F).The program aimed at the development of improved synthetic lines of sheep with higher reproduction rate than the local sheep and suited to the prevailing sub- tropical conditions.This investigation was carried out to esti- mate individual and maternal heterotic components for ewe productivity traits to enable the estimation of performance of synthetics including different portions of local and F inheritance.

Materials and methods
Data were collected from two MOA experimental farms and consisted of 5 520 records from 1 316 ewes during 1974-1986.Flocks were raised under an accelerated lambing system of three crops every two years (each two years were considered a block).Mating seasons lasted for 35 days and were in Sep- tember, May and January, and lambs were weaned at eight weeks of age.
The plan was to mate F rams to both Rah- inani (R) and Ossimi (O) ewes to produce half- breds (FR & FO), respectively which were used to produce both reciprocal back crosses ({F.FR & FR.R) and (O.FO & RO.O), respectively, that were inter se mated.
Nine different measurements of reproduction performance were evaluated.Those relat- ed to fertility were: number of ewes conceived (ECJ), number of lambs born (LBJ), number of lambs at four months of age (L4J), kilo- grams born (KBJ) and kilograms at four months of age (K4J), all being per ewe joined.Those related to prolificacy were: number of lambs born (LBL), number of lambs at four months of age (L4L), kilograms born (KBL) and kilograms at four months of age (K4L), all being per ewe lambed.
Data were analyzed by a least-squares fixed model, including effect of flock, block, sea- son of mating, parity and interactions between flock and block, season and parity and block and season along with four covariate terms.The covariate terms accounted for: (1) differ- ence between each of R or O minus F for direct effect of individual genes (gi), (2) differ- ence between each of R or O minus F for maternal environment of genes of the individual's dam, (gm) (3) individual heterosis between R & F and O & F, (hi) and ( 4) mater- nal heterosis between R & F and O & F (hm).
Coefficients of these covariate terms for different types of matings were, according to Dickerson (4), as follows (L = local): Both breed paternal effect and paternal heterosis were assumed negligible.

Results and discussion
Dickerson (4,5) discussed methods for utilizing the genetic diversity among breeds and factors determining it such as (1) individu- al (IG), maternal (IM) and paternal (IP) performance of purebreds and recombinations (R) effects in gametes produced by crossbred parents and (2) heterosis for individual (hi), maternal (hm) and paternal performance (hp).
IG, IM and IP performances of a specific breed are non-estimable.In contrast differ- ences between breeds in individual (gi), mater- nal (gm) and paternal (gp) are estimable.Flete- rosis for individual, maternal and paternal be- tween breeds are estimable if the models and breed combinations used for the estimation are appropriate.
This study aims at estimating the differences between local (L) -F purebreds individual breed and maternal effects and both individual and maternal heterosis.
Estimates of gi, gm, hi and hm and their standard errors, from R-F and O-F analyses, are presented in table 1.These estimates were utilized in predicting potential difference be- tween native sheep and pure F and different L X F crossbreds (table 2), calculations were made according to the genetic expectations of both pure-and cross-breds, as in A-N and G (1).
The relatively large standard errors, as- sociated with the estimates in table 1, are mainly a result of the large estimates of the error mean square of the traits studied.The total coefficient of determination (R2) from fitting the proposed model in this study for ewe reproduction traits were too low, (0.09 - Table 1.Least squares estimates of gi, gm, hi and hm (multiplied by 100) from Finn-Rahmani and Finn-Ossimi crossbreds (and standard errors).Estimates are multiplied by 100.0.18) and (0.18-0.30) for fertility and ture (3).Also, the contribution of the genetic prolificacy traits, respectively.This is in agree- part to the intra-breed total variation for these ment with R 2 estimates reported in the litera-traits are low (6).This would lead to a rela- lively large contribution of the unexplained variation.

Finn-Rahmani
Egyptian native breeds, though are well adapted to the environment and the ewe is fer- tile all year round (2), greatly lack on litter size, a useful trait in any intensification sys- tem.MO A plan was to produce a ewe with low F inheritance, hence the 1/4 F 3/4 L, where the small holder can afford the inputs required.However, with some intensive lamb production systems, now in operation in Egypt with more than 15 000 ewes, there seems a room for larger degree of intensifica- tion utilizing ewes of higher inheritance of prolific breeds i.e. 1/2 F 1/2 L. Results in table 2 indicate an expected im-provement of (0.32, 0.19), (0.32, 0.23), (0.18, 0.13) and ((0.18, 0.15) in LBJ and L4J for F.R, F.O, R.RF and O.OF after two genera- tion of inter se mating, respectively.The ex- pected increase in LBL and L4L are (0.50, 0.28), (0.59, 0.40), (0.23, 0.15) and (0.28, 0.22) for the same synthetics, respectively.It can be concluded that introducing the F to the local Egyptian breeds would substan- tially improve their lamb output at different levels of F inheritance.However, the costs of these schemes in relation to their potential eco- nomic benefits and the performance of these crosses under the breeders condition should be evaluated before any wide scale application.

Table 2 .
The predicted values for the difference between performance of different genotypes minus the local Räh- mäni and Ossimi.