Aspects of litter size (birth type) in goats and sheep production
Abstract
Increasing kid/lamb production is of paramount importance to goat and sheep producers. As a matter of one choice enhancing litter size becomes inevitable, because apart from litter size impacting on flock productivity, it is also implored as a major determinant of profitability due to its influence on kid/lamb survivability. There is a positive correlation between litter size and lifelong dam contribution and overall flock productivity. Increasing litter size to an optimal level might be crucial especially for the intensive goat and sheep production systems. A number of studies have proved that litter size is under the influence of both genetic and non-genetic factors. Currently, genome wide selection targeting established genetic markers is being employed to increase the efficiency of goat and sheep selection for reproductive traits, such as prolificity. This is on the background that litter size is lowly heritable, but on the other hand, immense genetic variability between and within breeds exist that could be exploited in breeding schemes by collaborating additive polygenic differences, breed complementarities, heterosis effects and major gene inheritance. Among the non-genetic factors that influence litter size in goats and sheep, parity order, age of dam and seasonal variation have been rated highly. Litter size tend to improve with age and parity order as a result it is highly likely that dams with large previous litter size may have high chances of producing multiple births in consecutive kidding/lambing. Environmental conditions are also an important source of variation on litter size, with chances of large litter size within natural reproductive seasons. Seasonal influence might be confounded by other factors such as flock nutritional management and genetic improvement strategies. The adverse effect of increase in litter size has been associated with an increase in number of underweight kids/lambs which in turn lower their survival rates. Underweight at birth is the probable explanation for reduced kid/lamb viability in goats and sheep. This entails a balance should be strike on optimal litter size, where too large and/or too small litter size may be impracticable desired and/or uneconomical, respectively. Proffered suggestion is that litter size of two is economically feasible for an intensive goat and sheep enterprise. The present review gives an insight on the influence of litter on flock performance and discuss the factors that are the major determinants of litter size in goat and sheep meat production.
References
Abdoli, R., Zamani, P., Mirhoseini, S.Z., Ghavi Hossein-Zadeh, N., Nadri, S., 2016. A review on prolificacy genes in sheep. Reprod. Domest. Anim., 51, 631-637.
Abegaz, S., Duguma, G., 2000. Genetic and phenotypic parameters of growth, reproduction, and survival performance of Horro sheep at Bako Agricultural Research Center. Research Report. International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia.
Açil, A.F., Demirci, R., 1983. The productivity and profitability of sheep breeding in Turkey. Proc. International Symposium on Production of Sheep and Goat in Mediterranean Area: 350-368, October 17-21, Ankara.
Adu, I., Buvanendran, V., Lakpini, C., 1979. The reproductive performance of Red Sokoto goats in Nigeria. J. Agr. Sci., 93(3), 563-566.
Afolayan, R.A., Fogarty, N.M., Gilmour, A.R., Ingham, V.M., Gaunt, G.M., Cummins, L.J., 2008. Reproductive performance and genetic parameters in first cross ewes from different maternal genotypes. J. Anim. Sci., 86(4), 804-814.
Akpa, G.N., Alphonsus, C., 2008. Relationship of parity with litter size and gestation length and their repeatability in rabbits. Proceedings of 13th annual conference of animal science association of Nigeria. (ASAN). 15th-19th September. ABU, Zaria. 76-77.
Alade, N.K., Mbap, S.T., Aliyu, J., 2008. Genetic and environmental factors affecting growth traits of goats in semi-arid area of Nigeria. Global J. Agr. Sci., 7(1), 85-91.
Alphonsus, C., Akpa, G.N., Sam, I.M., Agubosi, O.C.P., Finangwai, F.I., Mukasa, C., 2010. Relationship of parity and some breeding characteristics in Red Sokoto goats. Continent. J. Anim. Vet. Res., 2, 25-30.
Al-Shopery, S.A., Notter, D.R., 1994. Heritability of fertility and litter size in a fall lambing sheep flock. 83-86p in Proc. 5th Worl. Congr. Genet. Appl. Liv. Prod. 18, Guelph.
Amer, P.R., Jopson, N.B., Cocks, J., Scarlet, A.L., 2007. Impact of early age litter size on subsequent litter output in ewes. Proc. NZ. Soc. Anim. Prod., 67, 39.
Amer, P.R., McEwan, J.C., Dodds, K.G., Davis, G.H., 1998. Economic values for ewe prolificacy and lamb survival in New Zealand. Liv. Prod. Sci., 58, 75-90.
Amoah, E.A., Gelaye, S., 1990. Reproductive performance of female goats in South Pacific countries. Small Rumin. Res., 3(4), 257-267.
Amoah, E.A., Gelaye, S., Guthrie, P., Rexroad Jr, C.E., 1996. Aspects of reproduction of female goats. J. Anim. Sci., 74, 723-728.
Amoah, E.A., Gelaye, S., Guthrie, P., Rexroad Jr, C.E., 1996. Breeding season and aspects of reproduction of female goats. J. Anim. Sci., 74, 723-728.
An, X.P., Han, D., Hou, J.X., Li, G., Wang, J.G., Yang, M.M., Song, Y.X., Zhou, G.Q., Wang, Y.N., Ling, L., Yan, Q.M., Cao, B.Y., 2009. GnRH gene polymorphisms and their effects on reproductive performance in Chinese goats. Small Rumin. Res., 85, 130-134.
Analla, M., Muñoz-Serrano, A., et Serradilla, J.M., 1997. Analyse de la relation génétique entre la prolificité et les caractères de poids chez la race ovine Segureña. Can. J. Anim. Sci., 77, 17-21.
Awemu, E.M., Nwakolor, L.N., Abubakar, B.Y., 1999. Comparative influences of environmental sources of variation on preweaning growth traits in Yankassa sheep and Red Sokoto goats. In: Kolade, J., Babatunde, A., David, A., Belewu, M.A., Olu Atteh, J., Kolade, L. (eds.) Proceedings of the 26th Annual Conference of Nigerian Society of Animal Production, 21-25 March, Ilorin, Nigeria. 311-314.
Azis, R., Ciptadi, G., Suyadi, S., 2020. Genetic parameters of birth weight, litter size in crossbreeding of Boer and Indonesian goat. Budapest Int. Res. Exact. Sci. J., 2(3), 273-279.
Baiden, R.Y., 2007. Birth weight, birth type and pre-weaning survivability of West African Dwarf goats raised in the Dangme West District of the Greater Accra Region of Ghana. Trop. Anim. Health Prod., 39, 141-147.
Banerjee, G.C., 1989. A text book of animal husbandry. Seventh edition, Oxford and IBH publishing Co. India.
Bermejo, L.A., Mellado, M., Mata, J., Advalo, J.R., Nascimento, L.D., Camacho, A., 2010. Factors affecting days to conception, litter size and litter weight of intensively managed Canarian hair sheep. J. Appl. Anim. Res., 37, 261-264.
Bradford, G.E., 1985. Selection for litter size. In: Land, R.B., Robinson, D.W. (eds.) Genetics of reproduction in sheep. 3¬18p. Butterworths, London.
Brand, A.A., Cloete, S.W.P., De Villiers, T.T., 1985. Faktore wat lamvrektes in die Elsenburg Dormer- en S.A. Vleismerino-kuddes beinvloed. S. Afr. Tydskr. Veek., 15, 155.
Çetin, Y., Sagcan, S., Gungor, O., Ozyurtlu, N., Uslu, B.A., 2007. Effects of CIDR-G and melatonin implants, and their combination on the efficacy of oestrus induction and fertility of Kilis goats. Reprod. Domest. Anim., 44, 659-662.
Chay-Canul, A.J., Aguilar-Urquizo, E., Parra-Bracamonte, G.M., Piñeiro-Vazquez, Á.T., Sanginés-García, J.R., Magaña-Monforte, J.G., 2019. Ewe and lamb pre-weaning performance of Pelibuey and Katahdin hair sheep breeds under humid tropical conditions. Ital. J. Anim. Sci., 18, 850-857.
Chen, X., Sun, H., Tian, S., Xiang, H., Zhou, L., Dun, W., Zhao, X., 2015. Increasing litter size in a sheep breed by marker-assisted selection of BMPR1B A746G mutation. J. Genet., 94, 139-142.
Chiezey, N.P., Ajanusi, O.J., Oyedipe, E.O., 2008. The reproductive performance of sheep carrying natural infections of gastro-intestinal nematodes. Asian J. Anim. Vet. Adv., 3, 236-243.
Chniter, M., Hammadi, M., TouhamiKhorchani, T., Krit, R., Lahsoumi, B., Sassi, M.B., Nowak, R., Ben Hamouda, M., 2011. Phenotypicand seasonal factors influence birth weight, growth rate and lamb mortality in D’man sheep maintained under intensive management in Tunisian oases. Small Rumin. Res., 99, 166-170.
Chowdhury, S.A., Bhuiyan, M.S.A., Faruk, S., 2002. Rearing black Bengal goat under semi-intensive management 1. Physiological and Reproductive Performances. Asian Aust. J. Anim. Sci., 15(4), 477-484.
Chu, M.X., Wu, Z.H., Feng, T., Cao, G.L., Fang, L., Di, R., Huang, D.W., Li, X.W., Li, N., 2011. Polymorphism of GDF9 gene and its association with litter size in goats. Vet. Res. Comm., 35, 329-336.
de Lima, L.G., de Souza, N.O.B., Rios, R.R., de Melo, B.A., dos Santos, L.T.A., Silva, K.M., Murphy, T.W., Fraga, A.B., 2020. Advances in molecular genetic techniques applied to selection for litter size in goats (Capra hircus): A review. J. Appl. Anim. Res., 48(1), 38-44.
de Nicolo, G., Morris, S.T., Kenyon, P.R., Morel, P.C., Parkinson, T.J., 2008. Induced seasonal reproductive performance in two breeds of sheep. Anim. Reprod. Sci., 103(3-4), 278-289.
Deribe, B., Taye, M., 2014. Reproductive performance of Abergelle goats raised under traditional management systems in Sekota district, Ethiopia. Iran J. Appl. Anim. Sci., 4, 59-63.
Dingwall, W.S., Robinson, J.J., Fraser, C., 1981. Foetal growth during early pregnancy in prolific ewes. Anim. Prod., 32, 364.
Doloksaribu, M., Elieser, S., Mahmalia, F., Pamungkas, F.A., 2005. Produktivitas Kambing Kacang Pada Kondisi Dikandangkan: 1. Bobot Lahir, Bobot Sapih, Jumlah Anak Sekelahiran Dan Daya Hidup Anak Pra Sapih. Seminar Nasional Teknologi Peternakan dan Veteriner. Bogor, 12-13 September. Pusat Penelitian dan Pengembangan Peternakan, Bogor. P. 586589.
Donald, H.P., Russel, W.S., 1970. The relationship between liveweight of ewe at mating and weight of new-born lamb. Anim. Prod., 12, 273-280.
Dwyer, C.M., Calvert, S.K., Farish, M., Donbavand, J., Pickup, H.E., 2005. Breed, litter and parity effects on placental weight and placentome number, and consequences for the neonatal behaviour of the lamb. Theriogenol., 63(4), 1092-1110.
Ebozoje, M.O., Ngere, L.O., 1995. Incidence of preweaning mortality in West African Dwarf goats and their Red Sokoto half-bred. Niger. J. Anim. Prod., 22(3), 93-98.
Ekiz, B., Kocak, O., Ozcan, M., Yilmaz, A., 2007. Effects of parity and litter size on maternal behaviour in Kivircik ewes. 81-88.
Elieser, S., Sumadi, S., Budisatria, I.G.S., Subandriyo, S., 2012. Productivity comparison between Boer and Kacang goat dam. J. Indonesian Trop. Anim. Agr., 37(1).
Elsen, J.M., Bodin, L., Francis, D., Poivey, J.P., Teyssier, J., 1994. Genetic improvement of litter size in sheep. INRA Station d'Amelioration Genetique des Animaux. BP27 -31326 Castanet Tolosan -FRANCE 2 INRA Unite Zootechnique Mediterraneenne, ENSAM, 34060 Montpellier - France.
Fahumy, M.H., 1990. Reproductive performance, growth and wool production of Romanov sheep in Canada. Small Rumin. Res., 2, 253-264.
Feng, T., Geng, C.X., Lang, X.Z., Chu, M.X., Cao, G.L., Di, R., Fang, L., Chen, H.Q., Liu, X.L., Li, N., 2011. Polymorphisms of caprine GDF9 gene and their association with litter size in Jining Grey goats. Mol. Biol. Rep., 38, 5189-5197.
Fogarty, N.M., 1995. Genetic parameters for live weight, fat and muscle measurements, wool production and reproduction in sheep a review. Anim. Breed. Abst., 63, 102-143.
Freetly, H.C., Leymaster, K.A., 2004. Relationship between litter birth weight and litter size in six breeds of sheep. J. Anim. Sci., 82, 612-618.
Galal, E.S.E., Aboul-Naga, E.A., Elatawil, E.A., Kishin, E.S., 1972. Estimates of combining abilities and maternal influence in crosses between Merino, Ossimi and Barkie sheep. Anim. Prod., 15, 47-52.
Gaskins, C.T., Snowder, G.D., Westman, M.K., 2005. Influence of body weight, age and weight gain on fertility and prolificacy in four breeds of ewe lambs. J. Anim. Sci., 83, 1680-1689.
Gbangboche, A.B., Youssao, A.K.I., Senou, M., Adamou-Ndiaye, M., Ahissou, A., Farnir, F., Michaux, C., Abiola, F.A., Leroy, P.L., 2006. Examination of non-genetic factors affecting the growth performance of Djallonke sheep in Soudanian zone at the Okparabreeding farm of Benin. Trop. Anim. Health Prod., 38, 55-64.
Godfrey, R.W., 2005. Hair sheep production in the tropics: A Caribbean perspective. Hair Sheep Workshop Virginia State University, USA, 3-5.
Godfrey, R.W., Dodson, R.E., 2003. Effect of supplemental nutrition around lambing on hair sheep ewes and lambs during the dry and wet seasons in the U.S. Virgin Islands. J. Anim. Sci., 81, 587-593.
Gootwine, E., 2005. Variability in the rate of decline in birth weight as litter size increases in sheep. Anim. Sci., 81, 393-398.
Hagan, B.A., Nyameasem, J.K., Asafu-Adjaye, A., Duncan, J.L., 2014. Effects of non-genetic factors on the birth weight, litter size and preweaning survivability of West African Dwarf goats in the Accra plains. Liv. Res. Rural Dev., 26.
Haldar, A., Pal, P., Datta, M., Paul, R., Saumen, K., Pal Majumdar, D., Biswas, C.K., Pan, S., 2014. Prolificacy and its relationship with age, body weight, parity, pre-vious litter size and body linear type traits in meat-type goats. Asian Aust. J. Anim. Sci., 27, 628-634.
Hamed, A., Mabrouk, M.M., Shaat, I., Bata, S., 2009. Estimation of genetic parameters and some non-genetic factors for litter size at birth and weaning and milk yield traits in Zaraibi goats. Egypt. J. Sheep Goat Sci., 4, 55-64.
Haresign, W., 1985. The physiological basis for variation in ovulation rate and litter size in sheep: A review. Liv. Prod. Sci., 13, 3-20.
Haresign, W., 1992. Manipulation of reproduction in sheep. J. Reprod. Fertil. Suppl., 45, 127-139.
Harowi, M., 2016. Perbandingan Koefisien Heterosis antara Kambing Boerawa dan Saburai Jantan pada Bobot Sapih di Kecamatan Sumberejo Kabupaten Tanggamus.
Husain, S.S., Horst, P., Islam, A.B.M.M., 1996. Study on the growth performance of black Bengal goats in different periods. Small Rumin. Res., 21, 165-171.
Husain, S.S., Islam, A.B.M.M., Horst, P., 1995. Effect of different factors on pre-weaning survivability of black Bengal kids. Small Rumin. Res., 18, 1-5.
Ikwuegbu, O.A., Ofodile, S., 1994. Wet season supplementation of West African Dwarf goats raised under traditional management in the sub-humid zone of Nigeria. In: Lebbie, S.H.B., Rey, B., Irungu, E.K. (eds.) Small ruminant research and development in Africa. Proceedings of the African Small Ruminant Research Network AICC, Arusha, Tanzania. 7-11 December, 1992. 179-182.
IZ-PIB, 2005. Program Ochrony Zasobów Genetycznych owiec rasy olkuskiej. Kraków.
Kaczor, U., 2017. Genes involved litter size in Olkuska. Sheep Department of Animal Biotechnology, Agriculture University in Krakow, Poland.
Keskin, M., 2003. Influence of buck effect and exogenous hormone treatments on oestrus synchronisation and litter size of Shami (Damascus) goats. Turk. J. Vet. Anim. Sci., 27, 453-457.
Khanum, S.A., Hussain, M., Kausar, R., 2007. Assessment of reproductive parameters in female Dwarf goat (Capra hircus) on the basis of progesterone profiles. Anim. Reprod. Sci., 102, 267-275.
Kominakis, A., Rogdakis, E., Koutsotolis, K., 1998. Genetic parameters for milk yield and litter size in Boutsico dairy sheep. Can. J. Anim. Sci., 78, 525-532.
Koycegiz, F., Emsen, E., Alcibiades-Gimenez, C.A., Kutluca, M., 2009. Effects of lambing season, lamb breed and ewe parity on production traits of fat tailed sheep and their lambs. J. Anim. Vet. Adv., 8, 195-198.
Kumar, S., Mishra, A.K., Kolte, A.P., Arora, A.L., Singh, D., Singh, V.K., 2008. Effects of the Booroola (FecB) genotypes on growth performance, ewe's productivity efficiency and litter size in Garole x Malpura sheep. Anim. Reprod. Sci., 105(3-4), 319-331.
Macías-Cruz, U., Álvarez-Valenzuela, F.D., Olguin-Arredondo, H.A., Molina-Ramírez, L., Avendaño-Reyes, L., 2012. Ovejas Pelibuey sincronizadas con progestagénos y apareadas con machos de razasDorper y Katahdin bajo condiciones estabuladas: producción de laoveja y crecimiento de los corderos durante el período predestete. Arch. Med. Vet., 44, 29-37.
MacLaughlin, S.M., Walker, S.K., Roberts, C.T., Kleemann, D.O., McMillen, I.C., 2005. Periconcepional nutrition and the relationship between maternal body weight changes. I. The periconceptional period and feto-placental growth in the sheep. J. Physiol., 565, 111-124.
Maghsoudi, A., Torshizi, R.V., Jahanshahi, A.S., 2009. Estimates of (co)variance components for productive and composite reproductive traits in Iranian Cashmere goats. Liv. Sci., 126, 162-167.
Malik, C.P., Kanaujia, A.S., Balaine, D.S., Rathi, S.S., 1990. Mortality pattern in Beetal and Black Bengal goats and their reciprocal crosses. Indian J. Anim. Sci., 60(2), 228-232.
Maund, B.A., Duffel, S.l., Winkler, C.E., 1980. Lamb mortality in relation to prolificacy. Exp. Hush., 36, 99.
Mavrogenis, A.P., 1992. Breed group and parity effects on gestation duration and litter size at birth of sheep. Technical Bulletin 142, April 1992. Agr. Res. Inst. Ministr. Agr. Nat. Res., Nicosia, Cyprus.
Mellado, M., Foote, R.H., Borrego, E., 1991. Lactational performance, prolificacy and relationship to parity and body weight in crossbred native goats in north Mexico. Small Rumin. Res., 6, 167-174.
Mellado, M., Valdez, R., García, J.E., López, R., Rodríguez, A., 2006. Factors affecting the reproductive performance of goats under intensive conditions in a hot arid environment. Small Rumin. Res., 63, 110-118.
Mendel, C., Scholaut, W., Pirchner, F., 1989. Performance of Merinolandschaf and Bergschaf under an accelerated lambing system. Liv. Prod. Sci., 21, 131-141.
Menezes, L.M., Sousa, W.H., Cavalcanti-Filho, E.P., Gama, L.T., 2016. Genetic parameters for reproduction and growth traits in Boer goats in Brazil. Small Rumin. Res., 136, 247-256.
Meyer, H.H., Clarke, J.N., Harvey, T.G., Malthus, I.C., 1983. Genetic variation in uterine efficiency and differential responses to increased ovulation rate in sheep. Proc. NZ Soc. Anim. Prod., 43, 201-204.
Mia, M.M., Khandoker, M.Y., Husain, S.S., Faruque, M.O., Notter, D.R., 2013. Estimation of genetic and phenotypic parameters of some reproductive traits of black Bengal does. Iran. J. Appl. Anim. Sci., 3(4), 829-837.
Moaeen-ud-Din, M., Yang, L.G., Chen, S.L., Zhang, Z.R., Xiao, J.Z., Wen, Q.Y., Dai, M., 2008. Reproductive performance of Matou goat under sub-tropical monsoonal climate of Central China. Trop. Anim. Health Prod., 40, 17-23.
Morel, P.C.H., Kenyon, P.R., 2006. Sensitivity analysis of weaner lamb production in New Zealand. Proc. NZ Soc. Anim. Prod., 66, 377-381.
Mourad, M., Anous, M.R., 1998. Estimates of genetic and phenotypic parameters of some growth traits in common African and Alpine crossbred goats. Small Rumin. Res., 27, 197-202.
Nalbandov, I., 1990. Fisiologi Reproduksi pada Mamalia dan Unggas. Translated by S. Keman. UI-Press, Jakarta.
Notter, D.R., 2008. Genetic aspects of reproduction in sheep. Reprod. Domest. Anim., 43(Suppl 2), 122-128.
Nurgiartiningsih, V.A., 2012. Evaluasi genetik pejantan Boer berdasarkan performans hasil persilangannya dengan kambing lokal. TERNAK TROPIKA J. Trop. Anim. Prod., 12, 82-88.
Ocak, S., Emsen, E., Köycegiz, F., Kutluca, M., Onder, H., 2009. Comparison of placental traits and their relation to litter size and parity weight in sheep. J. Anim. Sci., 87(10), 3196-3201.
Perry, R.C., Corah, L.R., Cochran, R.C., Beal, W.E., Stevenson, J.S., Minton, J.E., Simms, D.D., Brethour, J.R., 1991. Influence of dietary energy on follicular development, serum gonadotropins, and first postpartum ovulation in suckled beef cows. J. Anim. Sci., 69, 3762-3773.
Radhika, G., Raghavan, K., Aravindakshan, T., Thirupathy, V., 2015. Genetic diversity and population structure analysis of native and crossbred goat genetic groups of Kerala, India. Small Rumin. Res., 131, 50-57.
Rashidi, A., Mokhtari, M., Gutiérrez, J., 2011. Pedigree analysis and inbreeding effects on early growth traits and greasy fleece weight in Markhoz goat. Small Rumin. Res., 124, 1-8.
Rattray, P.V., Jagusch, K.T., Smith, J.F., Winn, G.W., MacLean, K.S., 1980. Flushing responses from heavy and light ewes. Proceedings of the New Zealand Soc. Anim. Prod., 40, 34-37.
Safari, E., Fogarty, N.M., Gilmour, A.R., 2007. A review of genetic parameter estimates for wool, growth, meat and reproduction traits in sheep. Liv. Prod. Sci., 92, 271-289.
Sánchez-Dávila, F., Bernal-Barragán, H., Padilla-Rivas, G., del Bosque-González, A.S., Vázquez-Armijo, J.F., Ledezma-Torres, R.A., 2015. Environmental factors and ram influence litter size, birth, and weaning weight in Saint Croix hair sheep under semi-arid conditions in Mexico. Trop. Anim. Health Prod., 47(3).
Sancristobal-Gaudy, M-S., Bodin, L., Elsen, J-M., Chevalet, C., 2001. Genetic components of litter size variability in sheep. Genetics Selection Evolution, Bio. Med. Centr., 33(3), 249-271.
Sarmento, J.L.R., Filho, P., Abreu, E.C., Ribeiro, M.N., Sousa, J.E.R., 2010. Prolificidadede caprinos mestiços leiteiros no semiárido nordestino. R. Bras. Zootec., 39, 1471-1476.
Scales, G.H., Burton, R.N., Moss, R.A., 1986. Lamb mortality, birth weight and nutrition in late pregnancy. New Zealand J. Agr. Res., 29, 75.
Sodiq, A., Yuwono, P., Santos, S.A., 2011. Litter size and lamb survivability of Batur sheep in upland areas of Banjarnegara Regency Indonesia. J. Anim. Prod., 13, 166-172.
Song, H.B., Jo, I.H., Sol, H.S., 2006. Reproductive performance of Korean native goats under natural and intensive conditions. Small Rumin. Res., 65, 284-287.
Sulieman, A.H., Sayers, A.R., Wilson, R.T., 1990. Evaluation of Shugor, Dubasi and Watish subtypes of Sudan desert sheep at the El-Huda national sheep research station, Gezira province, Sudan. ILCA Research Report No. 18. International Livestock Centre for Africa, Addis Ababa, Ethiopia.
Tummaruk, P., Tantasuparuk, W., Techakumphu, M., Kunavongkrit, A., 2007. Age, body weight and backfat thickness at first observed oestrus in crossbred Landrace*Yorkshire gilts, seasonal variations and their influence on subsequence reproductive performance. Anim. Reprod. Sci., 99, 167-181.
Turkson, P.K., Sualisu, M., 2005. Risk factors for lamb mortality in Sahelian sheep on breeding station in Ghana. Trop. Anim. Health Prod., 37, 4964.
Turkyilmaz, D., Esenbuga, N., 2019. Increasing the productivity of Morkaraman sheep through crossbreeding with prolific Romanov sheep under semi-intensive production systems. S. Afr. J. Anim. Sci., 49(1).
Vanimisetti, H.B., Notter, D.R., Kuehn, L.A., 2007. Genetic(co) variance components for ewe productivity traits in Katahdin sheep. J. Anim. Sci., 85, 60-68.
Vihan, V.S., Kala, S.N., Singh, V.P., 1992. Epidemiological investigation of neonatal kid mortality due to enteropathogenic colibacillosis. Prevent. Vet. Med., 13(3), 179-183.
Waldron, D.F., Thomas, D.L., 1992. Increased litter size in Rabouillet sheep. II. Expected response from alternative selection criteria. J. Anim. Sci., 70, 3345-3350.
Wilson, R.T., 1986. Livestock production in central Mali: Long term studies on cattle and small ruminants in the agropastoral system. Research Report 14. ILCA, Addis Ababa, Ethiopia.
Xu, S.-S., Li, M., 2017. Recent advances in understanding genetic variants associated with economically important traits in sheep (Ovis aries) revealed by high-throughput screening technologies. Front. Agr. Sci. Eng., 4, 279-288.
Xu, S-S., Gao, L., Xie, X-L., Ren, Y-L., Shen, Z-Q., Wang, F., Shen, M., Eyþórsdóttir, E., Hallsson, J.H., Kiseleva, T., Kantanen, J., Li, M-H., 2018. Genome-wide association analyses highlight the potential for different genetic mechanisms for litter size among sheep breeds. Front. Genet., 9, 118.
Yonghong, H., Qinkang, C., Genghua, H., Zhangping, Y., 2001. Effect of Boer goat crossbreeding with Haimen goats and Huai goats in Jiangsu province. Proc. Int. Conf. Boer Goats, Guizhou, China, 192-197.
Yuan, Z., Zhang, J., Li, W., Wang, W., Li, F., Yue, X., 2019. Association of polymorphisms in candidate genes with the litter size in two sheep breeds. Anim., 9, 958.
Yue, G.H., 1996. Reproductive characteristics of Chinese Hu sheep. Anim. Reprod. Sci., 44, 223-230.
Zahraddeen, D., Bustwat, I.S.R., Mbap, S.T., Naibi, S.A., 2008. Correlation of some reproductive traits with partial daily milk yield and growth traits in local goats of Nigeria. Proceeding of 13th annual conference of animal science association of Nigeria, September 15-19, A.B.U Zaria. 13-15.
Zhang, C.Y., Chen, S-L., Li, X., Xu, D-Q., Zhang, Y., Yang, L-G., 2009. Genetic and phenotypic parameter estimates for reproduction traits in the Boer Dam. Liv. Sci., 125, 60-65.
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2020 Never Assan
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
