Strategije selekcije živali za prirejo mleka A2

magistrsko delo

Kaja Mezinec (Author), Andreja Čanžek Majhenič (Reviewer), Klemen Potočnik (Mentor)

Abstract

Mleko A2 je nišni proizvod po katerem porabniki v tujini že povprašujejo, v Sloveniji pa imamo samo enega ponudnika takega mleka. Samo krave, ki imajo dve kopiji gena A2 za beta kazein, lahko proizvajajo t.i. mleko A2. Beta kazein A2 ima na mestu 67 prisotno aminokislino prolin, ki prepreči sproščanje beta-kazomorfina 7 (BCM7) iz beta kazeina A2. BCM7 je znan kot močan opioid in ga povezujejo z dejavniki tveganja za zdravje ljudi, saj lahko prizadene opioidne receptorje v živčnem, endokrinem in imunskem sistemu. Tradicionalne pasme goveda, ki so bile podvržene manj intenzivni selekciji na proizvodne lastnosti, imajo praviloma večjo frekvenco alela A2 za beta kazein. Prireja mleka s temi pasmami bi lahko bila model sistema trajnostnega upravljanja z marginalnimi območji. Namen naloge je bil primerjati različne strategije selekcije živali za prirejo mleka A2 in oceniti posledice posamezne strategije selekcije. Dobili smo podatke 965 živali rjave pasme govedi z znanim genotipom za beta kazein in PV12 za količino mleka, vsebnost maščobe in beljakovin v mleku, število somatskih celic ter skupni selekcijski indeks. Do statusa črede 100 % A2 najhitreje pridemo z uporabo semena bikov z genotipom A2A2 in z genotipizacijo krav. Hitrost spreminjanja lahko dodatno povečamo z uporabo seksiranega semena. Ugotovili smo, da genotip A2A2 statistično značilno vpliva na PV12 za vsebnost beljakovin v mleku ter na skupni selekcijski indeks. Interakcija med spolom in genotipom ni imela statistično značilnega vpliva na nobeno od opazovanih lastnosti, spol pa je statistično značilno vplival na skupni selekcijski indeks ter na PV12 za količino mleka. Uporaba semena bikov z genotipom A2A2 lahko povzroči manjši genetski napredek, ki je posledica neuporabe semena, sicer nekaterih elitnih bikov, z genotipom za beta kazein A1A1 ali A1A2.

Keywords

govedoreja;krave molznice;selekcija;mleko A2;magistrske naloge;

Data

Language:	Slovenian
Year of publishing:	2021
Typology:	2.09 - Master's Thesis
Organization:	UL BF - Biotechnical Faculty
Publisher:	[K. Mezinec]
UDC:	636.2:575(043.2)
COBISS:	78884611
Views:	246
Downloads:	93
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Selection strategy for production of A2 milk
Secondary abstract:	A2 milk is a niche product that is already in demand by consumers abroad, but in Slovenia we have only one supplier of A2 milk. Only cows that have two copies of the A2 gene for beta-casein can produce A2 milk. A2 beta-casein has a proline at position 67 that prevents the release of beta casomorphin 7 (BCM7) from A2 beta-casein. BCM7 is potentially known to be an opioid and has been linked to a risk factor for human health because it can affect opioid receptors in the nervous, hormonal, and immune systems. Traditional cattle breeds subjected to less intensive selection for production traits generally have a higher frequency of the A2 allele. The objective of this thesis was to compare different strategies for breeding animals for A2 milk production and to evaluate the consequences of each selection strategy. We obtained genotyping data from 965 brown cattle. Data included BV12 per milk yield, fat and protein contents in milk, somatic cell count, and total merit index. The fastest way to achieve herd status 100% A2 is to use semen from sires with the A2A2 genotype and genotyping all cows. The speed of replacement can be further increased by using sexed semen. We found that genotype had a significant effect on BV12 for protein content and on BV12 for total merit index. Animals with genotype A2A2 had higher BV12 for these two traits. The interaction between sex and genotype had no effect on the observed traits, but sex had a significant effect on BV12 for total merit index and on BV12 for milk yield. The use of sires with the A2A2 genotype may result in lower genetic gain because elite sires with the genotype A1A1 or A1A2 for beta casein was not used.
Secondary keywords:	cattle production;dairy cows;selection;A2 milk;
Type (COBISS):	Master's thesis/paper
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Biotehniška fak., Oddelek za zootehniko
Pages:	X, 39 str.
ID:	13620772