Celoletna poliestričnost pri ovcah

diplomsko delo

Marjana Gerželj (Author), Tatjana Pirman (Reviewer), Simon Horvat (Mentor), Mojca Simčič (Co-mentor)

Abstract

Za razliko od ostalih rejnih živali ovce večinoma redimo v ekstenzivnih pogojih reje, zato se je pri tej vrsti pretežno ohranila sezonska poliestričnost. Izjema so določene pasme, ki so celoletno poliestrične. Na sezonsko izraženo reproduktivno aktivnost pri ovcah vpliva več dejavnikov, na primer fotoperioda, geografska širina, prisotnost plemenskega ovna in telesna kondicija. Pasme ovc, ki izvirajo iz ekvatorialnega območja, v svojem izvornem okolju kažejo celoletno poliestričnost, ki pa v zmernem pasu ni vedno izražena. Prav tako lahko posamezne ovce sezonsko poliestričnih pasem izražajo celoletno poliestričnost v območjih okrog ekvatorja. Celoletna poliestričnost se je pri ovcah zaradi ugodnih razmer v okolju pojavila že v neolitiku. Jagnjeta, rojena izven običajne sezone rojstev, so lahko preživela le z dodatno oskrbo neolitskih rejcev in so tako prenesla lastnost celoletne poliestričnosti v naslednjo generacijo. Za rejo celoletno poliestričnih pasem ovc imamo na voljo več tehnologij reje, ki omogočajo več kot eno jagnjitev letno. Celoletna poliestričnost je pomembna lastnost, saj omogoča kontinuirano prirejo jagnjet za zakol. Klasična selekcija na to lastnost je zaradi več dejavnikov otežena, genetski napredek pa manjši in počasen. Zato znanstveniki poskušajo identificirati genetske označevalce s pozitivnimi učinki na to lastnost, ki bi omogočali genomsko selekcijo in večji ter hitrejši genetski napredek. Na podlagi pregledane literature sklepamo, da je na pojav celoletne poliestričnosti verjetno imelo večji vpliv okolje kot genetski dejavniki.

Keywords

ovce;reprodukcija;genomska selekcija;celoletna poliestičnost;diplomske naloge;

Data

Language:	Slovenian
Year of publishing:	2021
Typology:	2.11 - Undergraduate Thesis
Organization:	UL BF - Biotechnical Faculty
Publisher:	[M. Gerželj]
UDC:	636.3(043.2)
COBISS:	76964099
Views:	203
Downloads:	27
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Out-of-season lambing in sheep
Secondary abstract:	Unlike other livestock species, we mostly rear sheep extensively, which is why they are still mainly bred seasonally. Exceptions are certain breeds that can lamb out of season. Seasonal rearing of sheep is influenced by many factors, such as photoperiod, geographic latitude, exposure to rams, and the body condition of ewe. Sheep breeds originating from tropical regions tend to lamb out of season in their native habitat but do not always show this trait in temperate zones. Similarly, some seasonal breeding sheep breeds lamb out of season in tropic regions in both tropical and temperate zones. Out-of-season lambing in sheep first appeared at Neolithic Period because environmental conditions were favourable. The lambs that were born out of season were only able to survive due to extra care provided by Neolithic breeders and were therefore able to pass on the out-of-season lambing trait to the next generation. There are several production systems for sheep breeds that lamb out of season and where sheep can lamb more than once per year. Out-of-season lambing is an economically important trait as it allows continuous production of lambs for slaughter throughout the year. Due to many factors, classical selection for this trait is slow and inefficient, so scientists are trying to identify genetic markers with positive effects on this trait that would allow genomic selection and greater and faster genetic gain. Based on the literature review, we conclude that environment likely has a greater influence on the occurrence of out-of-season lambing than genetic factors.
Secondary keywords:	sheep;reproduction;genomic selection;out of season lambing;
Type (COBISS):	Diploma project paper
Study programme:	0
Thesis comment:	Univ. v Ljubljani, Biotehniška fak., Oddelek za zootehniko
Pages:	VII, 16 str.
ID:	13477297