20.500.12556/DKUM-85863 Spolno razmerje potomstva pri govedu glede na prehranjenost matere magistrsko delo Offspring ratio in cattle in accordance with maternal nutrition V živinoreji se pri potomcih pogosto favorizira določen spol. Dandanes se za namen produkcije željenega spola potomca uporabljajo izključno biotehnološke metode, predvsem seksirano seme. Vendar pa poznamo tudi biološke mehanizme, ki pod določenimi okoljskimi pogoji, na primer razpoložljivost virov in prehranska preskrba samice, povzročajo odklon spolnega razmerja pri potomstvu. V nalogi smo na podlagi podatkov Centralne podatkovne zbirke Govedo iskali povezavo med prehranjenostjo krav, predvsem na osnovi oskrbe z energijo, ocenjene posredno prek sestave mleka, in spolnim razmerjem potomstva. Ocena prehranjenosti je temeljila na razmerju med mlečnimi maščobami in beljakovinami ter na vsebnosti sečnine v mleku v obdobju od 7 do 14 dni pred uspešno osemenitvijo. Uporabili smo podatke krav različnih pasem, vključenih v kontrolo prireje od leta 2009 do 2022. Izhodiščni podatkovni set je skupno vseboval podatke za 51.766 kontrol prireje mleka od skupno 43.261 krav molznic iz 4.227 rej. Podatkov o količini sečnine v mleku smo imeli za 39.437 kontrol, podatke o številu somatskih celic (ŠSC) v mleku pa za 50.226 živali, od tega je imelo 23.300 živali ŠSC pod 150.000. ŠSC nad 150.000 nakazuje na začetek vnetnih procesov v vimenu, ki lahko pomembno vpliva na sestavo mleka, zato smo takšne živali obravnavali posebej. Rezultati kažejo, da imajo živali z nižjim razmerjem med mlečnimi maščobami in beljakovinami značilno večji delež moških potomcev, živali z visokim razmerjem pa večji delež ženskih potomcev. Krave z nizkimi in srednjimi vrednostmi sečnine v mleku imajo značilno višji delež ženskih potomcev. Živali, ki so boljše energijsko oskrbljene, imajo torej večji delež moških potomcev, pri živalih s slabšo energijsko oskrbljenostjo pa se kaže nasprotna tendenca. V vseh primerih so imele živali s ŠSC >150.000 moško odklonjeno spolno razmerje potomstva. Rezultati deloma potrjujejo Trivers-Willardovo hipotezo, ki implicira žensko odklonjeno spolno razmerje potomcev krav s slabšo preskrbljenostjo (energetsko bilanco), kar je pri poliginih živalih evolucijsko smotrnejše in rezultira z višjim biološkim fitnesom. Rezultati raziskave nakazujejo možnost uporabe prilagajanja krmnega obroka v obdobju pred osemenitvijo kot sorazmerno enostavnega načina manipulacije spolnega razmerja pri kravah molznicah In livestock production, offspring of a particular sex are often preferred. Nowadays, solely biotechnological methods are used, especially sexed semen, in order to produce offspring of a preferred sex. However, there are also biological mechanisms that cause a deviation in the sex ratio of the offspring under certain environmental conditions, such as the availability of resources and the nutritional status of the female. Using data from the Slovenian Central Cattle Breeding Database, we analysed the relationship between cow nutritional status, estimated indirectly through the energy balance based on milk composition, and the sex ratio of the offspring. Cow nutritional status was estimated from the fat:protein ratio and the urea content measured in milk in the period from 7 to 14 days before successful insemination. Data set comprised cows of different breeds that underwent regular milk recording from 2009 to 2022. The original dataset contained data for a total of 51,766 milk recordings from a total of 43,261 dairy cows from 4,227 farms. Data on milk urea content was available for 39,437 animals and data on somatic cells count (SSC) for 50,226 animals, of which 23,300 had SSC below 150,000. SSC above 150,000 indicates the onset of inflammatory processes in the udder that can significantly affect milk composition, therefore, we analysed such animals separately. The results show that cows with a lower milk fat: protein ratio have a greater proportion of male offspring, while cows with a high ratio have a greater proportion of female offspring. Cows with low to medium milk urea levels had a greater proportion of female offspring. Animals with a better energy supply thus had a higher proportion of male offspring, while the opposite tendency was observed in animals with a lower energy supply. In all cases, animals with SSC over 150.00 had generally male-biased offspring sex ratio. The results at least partially support the Trivers-Willard hypothesis that the sex ratio of offspring from cows with poorer nutritional status (energy balance) is more likely to be female-biased, resulting in higher biological fitness in polygynous animals. The results suggest that adjusting the diet in the period before insemination could be a relatively simple way of manipulating offspring sex ratio in dairy cows. govedo spolno razmerje prehranjenost sestava mleka teorija dodelitve spola cattle sex ratio nutrition composition of milk theory of sex assignment true true false J. Belšak Slovenski jezik Angleški jezik Magistrsko delo/naloga 2023-09-15 10:57:47 2023-10-10 13:12:09 2023-10-11 03:12:32 0000-00-00 00:00:00 2023 0 Maribor 0 Maribor 1 spletni vir (1 datoteka PDF (VI, 37 str., [1] str. pril.)) 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 636.2.082/.084:637.127(043)=163.6 167796227 MAG_Belsak_Janez_2023.pdf MAG_Belsak_Janez_2023.pdf 1 3DD69350600E6C80E16FB00C33318604 02bc6fc84568e405e2590cefb08aa1040a80f4a5a8c42709623c49904b784cbf 8d9cd3c2-5e36-11ee-aa7c-00155d000105 https://dk.um.si/Dokument.php?lang=slv&id=173140 Fakulteta za kmetijstvo in biosistemske vede 0 0 0