EFFECT OF MATING METHOD , SEX AND BIRTH TYPE ON GROWTH OF LAMBS

Estrus synchronization methods was use to control the reproductive traits of sheep, as well as bringing more females at the same stage of estrus and ovulation. According to the points mentioned above, the aim of the present study was to investigate and compare mating method and influence of fixed factors on birth and weaning weight of lambs. Statistical analysis showed that exist difference in the body weights between genotypes of lambs. In the first group, the difference in weight of lambs at birth, regardless of mating method was not significant (P> 0.05), while in the second group, the difference was slightly significant (P <0.05). As for the birth type,sex and within the same genotype, there was a statistical significance (P <0.05) between singles obtained naturally, between the triplets obtained naturally and between triplets received hormonal method. All the differences between body weight at 30 days (mating method, sex and birth type under the same genotype) were statistically significant (P <0.05).The determined differences in the body weights at 60 days (sex, mating method and type of birth under the same genotype) were statistically significant (P <0.05). The results showed that the differences (mating method, sex and type of birth under the same genotype) were statistically significant (P <0.05), except in between body weight at 90 days in twins among two genotypes obtained by natural method, which were not statistically significant (P> 0.05).


Introduction
In order to boost the production of sheep and technological process of organizing principles in industry, science has made efforts to successfully manage the process of breeding ewes.Today, in many countries, including ours, estrus synchronization methods was use to control the reproductive traits of sheep, as well as bringing more females at the same stage of estrus and ovulation.This method enabled the two or three lambs a year for two years, with the aim of increasing meat production.Petrovic (2007) point out that the use of proper hygiene in the reproduction of sheep, breeding age, environmental conditions, qualitative and quantitative nutrition, prevention and treatment are the key factors.The same authors argue that, the recognition of estrus and time of admission is the essential part of the concept, and therefore the pregnancy of animals.For more than half a century attempts have been made to synchronize the period of sexual receptivity, or estrus, in farm animals.Synchronization of estrus can save labor and is a key component in artificial insemination (AI) programs.Synchronizing estrus during the normal breeding season provides a means for producers to schedule the lambing period, concentrating labor needs into a short frame of time.Estrous synchronization also can help in improving and the uniformity of the lamb crop for market, Knights et al,(2001).Estrus synchronization (ES) in goats and sheep is achieved by control of the luteal phase of the estrous cycle, either by providing exogenous progesterone or by inducing premature luteolysis.The latter approach is not applicable during seasonal anestrus, whereas exogenous progesterone in combination with gonadotropin can be used to induce and synchronize estrus in anovular does and ewes, S. Wildeus ( 1999).Successful estrus synchronization programs have a key role in lambing rate efficiency and profitability of sheep holders in semi-intensive production systems (Knights et al., 2001).Using different intravaginal devices impregnated with P4 or synthetic progestogens has been extended all over the world.Controlled internal drug release (CIDR) device impregnated with 300 mg P4 and intravaginal sponges containing with 60 mg medroxyprogesterone acetate (MAP) or 40 mg fluoroprogesterone acetate (FGA) are two main intravaginal devices that are used vastly for ewes estrus synchronization (Ungerfeld and Rubianes, 2002).PGF2α and/or its analogue are luteolytic factors and according to its role in regression mechanism of corpus luteum (Turk et al., 2008), double injections (9 to 11 days interval) of PGF2α is common for ewes' estrus synchronization (Atamani and Akoz, 2006;Wildeus 2000).Also, Dixon et al. (2006) used progesterone and/or its analogue treatment and reported greater estrus observation in progesterone-PGF2α combination treated ewes than those received PGF2α alone.Combination of PMSG and P4 impregnated intravaginal devices causes readily estrus synchronization (Romano 2004).PMSG treatment reduces the interval between the onset of estrus and ovulation (Dogan and Nur, 2006), also in no PMSG received ewes, ovulations occurs later (Barrett et al., 2004).One dose of PMSG can stimulate follicular development and higher ovulation rate in ewes (Koyuncu and Ozis Alticekic, 2010).Due to the importance of PMSG in sheep reproduction efficiency and injection of 500 IU PMSG with 40 mg of FGA for estrus synchronization in breeding season, 87% of treated ewes exhibited overt sign of estrus when compared with 48% in the control group (Langford, 1982) or CIDR removal until the estrus onset was shorter in progesterone-PGF2α.Obtained results by Dogan and Nur (2006) demonstrated that the interval between Sponge progesterone -PGF2α combination treated ewes than those that received progesterone alone.One dose of PMSG can stimulate follicular development and higher ovulation rate in ewes (Koyuncu and Ozis Alticekic, 2010).Estrous synchronization is a valuable management tool which has been successfully employed to enhance reproductive efficiency, particularly in ruminants (Kusina et al., 2000).In small ruminants, estrous synchronization is achieved either by reducing the length of the luteal phase of the estrous cycle with prostaglandin F2α or by extending the cycle artificially with exogenous progesterone or more potent progestagens (Jainudeen et al., 2000;Kusina et al., 2000).As prostaglandin treatment is limited to the breeding season, different protocols of estrous synchronization using progestin's have been introduced (Ainsworth and Wolynetz, 1982;Godfrey et al., 1997;Rosado et al., 1998).Estrus synchronization by CIDR method was as effective as Sponge (MAP) and PGF2α treatment for inducing estrus.Also, CIDR treated ewes exhibited overt signs of estrus earlier than other treatment groups, Naderipour et al, (2012).According to the points mentioned above and the importance of estrus synchronization to optimize ewes reproduction efficiency, the aim of the present study was to investigate and compare mating method and influence of fixed factors on birth and weaning weight of lambs.

Materials and Methods
Investigation of the effect of estrus synchronization was performed on private farm in Vrnjacka Banja.
• The first group of 60 local Pirot ewes mated with ram of Wurttemberg breed of sheep.• Second group of 60 local Pirot ewes were mated with ram of Improved Pirot breed of sheep.
Within each group 30 sheep were subjected to natural mating and the rest 30 sheep within each group have been utilized for estrus synchronization.The first subgroup of both groups performed the synchronization and the second subgroup of both groups performed the natural mating.One ram was mated for every ten ewes.For induction of estrus synchronization and in sheep experimental group applied the technique of intra vaginal sponges with progestin's (Veramix, Pharmacia & Upjohn, Belgium) Applicator coated Vaseline on the outside and the inside part, frimly held and introduced into the vagina to the cervix.Rod applicator sponge is pushed forward and then pilled out a tube applicator from the vagina, extracting rod that holds the sponge that carried control setting using a plastic end that protrudes from the vagina.Synchronization of sheep had done in the month of April.Sponges were removed from the vagina 12 days after the application.The first sign of estrus were reported 35 hous after the extraction.The experimental sheep lambing commenced on the 30 th of August those that are conceptualized by, or on the 16 th September who became pregnant in the next estrus.Before the synchronization of estrus a dose of an anthelmintic treatment and vaccination of sheep against anaerobic bacteria was performed.Determination of the production result based on the body weight have been made for both groups.Recording of body weight started from newborn lambs (birth weight-BW), lambs body weight at 30 days, (BW30), 60 days (BW60) and 90 days (BW90).Statistical analysis was performed by GLM procedure of SPSS package, using the next model: Yijklm = μ + Gi+ Mj+ Bk + Sl + εijklm, where Yijklm = body weight of m th lamb of l th sex, kj th birth type, j th mating method, i th genotype μ = overall population mean Gi= effect of genotype(fixed effect -2 classes) Mj= effect of mating method (fixed effect -2 classes) Bk = effect of birth type (fixed effect -3 classes) Sl = effect of sex (fixed effect -2 classes) εijklm = residual error

S-synchronization, N-natural
On table 2 showed that the birth weight of single born male lambs and female from natural mating were heavier than the single born male and female lambs from synchronized mating for the same difference of 0.26 kg.The male and female lambs born twin from natural mating were heavier for 0.31 kg and 0.24 kg.The male and female lambs born triplet were heavier in natural mating with a difference of 0.11 kg for male lambs and 0.21 kg for female in synchronized mating.

S-synchronization, N-natural
From table 2, can also be seen, that the body weight of male lambs and female lambs from natural mating at 30 days were heavier in all birth type with differences of: 0.23 kg; 0.47 kg, 0.58 kg; 0.83 kg, 0.41 kg; 0.52 kg.At 60 days, lambs from natural mating were heavier in both sexes as well as in all birth types the differences were: 0.9 kg ;1.46 kg, 1.09 kg;1.36 kg, 0.3 kg;1.88 kg.Same at 90 days, lambs from natural mating were dominant in weight in all ages and in both sexes.The differences were as follows : 0.71 kg;1.8 kg, 1.61 kg;1.99 kg, 0.67 kg;2.54 kg.
As shown in table 3, the birth weight of male and female lambs from natural mating were heavier than synchronized in all birth type..The differences were: 0.19 kg;0.37 kg, 0.07 kg;0.21kg, 0.19 kg;0.26kg respectively.Yilmaz and Altin, (2011) birth type and the sex of the lambs were found to significantly affect birth weight, which is an important factor in lamb production which was in accordance with ours.As can be seen on tables 2 and 3 indicated that generally synchronized mating affected the body weight of lambs from birth to 90 days.Özbey and Esen (2000) quoted that estrus synchronization usually increases the number, but reduces the birth weight of lambs, which is related with the results we obtained.The average birth weight in our study was (3.17 kg) was lower than the average found by other studies performed by some authors on different genotypes Chios × Akkaraman F1, 4.72 kg; Kıvırcık × Akkaraman F1, 4.75 kg; Chios × (Kıvırcık × Morkaraman) F1, 4.45 kg; Kıvırcık × (Chios × Morkaraman) F1, 4.25 kg; crossbred lambs (Akcapinar et al .;2000, Ozbey andEsen 2000); Kıvırcık lambs under half-intensive conditions, 3.69 kg (Altine et al., 1998,); and Akkaramans, Merino, and their crosses under village conditions, 3.74 kg (Thieme et al., 1999) but almost similar with the result (3.18 kg) obtained by Yilmaz and Altin, (2011).
At 30 days, the lambs born singles and twins were heavier from natural mating but born triplets were heavier from synchronized in both sexes.Differences in weight: 0.31 kg; 0.47 kg, 0.53 kg; 0.39 kg, 0.26 kg; 0.4 kg.
The lambs at 60 and 90 days, female born triplets were heavier from synchronized but lambs born singles and twins in both sexes and the male born triplets were heavier from natural mating.The weight differences were as follows: 0.49 kg;0.76 kg, 0.75 kg;0.95kg, 1.21 kg;1.29 kg and 1.09 kg;1.24kg, 1.41 kg;1.41 kg (same differences in both sexes), 1.53 kg;0.58 kg.Our results were similar with results of Petrovic et al.(2011).
Statistical analysis of our results showed that exist difference in the body weights between groups of lambs depending of investigated factors.In the first group, the difference in weight of lambs at birth, with regard of mating method was not significant (P> 0.05), while in the second group, the difference was statistically significant (P <0.05).As for the birth type, and within the same group, there was a statistical significance (P<0.05) between singles obtained naturally, between the triplets obtained naturally and between triplets received hormonal method.
All the differences between male body weight at 30 days (mating method, sex and birth type under the same genotype) were statistically significant (P <0.05).
The determined differences in the body weights at 60 days (between genotypes, mating method, sex and type of birth under the same genotype) were statistically significant (P <0.05).
The results showed that the differences (mating method, sex and type of birth under the same genotype) were statistically significant (P <0.05), except in between body weight at 90 days in twins among two genotypes obtained by natural method, which were not statistically significant (P> 0.05).

Conclusion
Based on the results obtained can be concluded that sex had a significant effect on body weight of lambs in all ages regardless of mating method.The estrus synchronization can increase the number of offspring, but reduces the birth weight of lambs.Generally, natural mating shows dominance in body growth in all ages of lambs.

Acknowledgment
Research was financed by the Ministry of Education and Science of Republic of Serbia under the projects TR31001 and TR31053.