Effect of incorporation of a heat tolerance gene into dairy cattle and effect on farm profitability : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatū, New Zealand. EMBARGOED until 18th December 2024.

dc.contributor.authorThant, Aung Myo
dc.date.accessioned2024-04-16T20:34:12Z
dc.date.available2024-04-16T20:34:12Z
dc.date.issued2023
dc.descriptionEmbargoed until 18th December 2024
dc.description.abstractHeat stress is an impediment to dairy production not only in tropical countries but also in temperate countries. In previous studies, dairy cows with a slick hair phenotype were more resistant to heat stress than cows with wild-type hair. Therefore, the incorporation of the slick hair gene, a heat tolerance gene, into dairy cows would be an opportunity to improve heat stress resistance of dairy cows, and it may also enhance productivity and profitability of dairy cows in temperate countries. The objectives of the current study were to evaluate the effect of incorporation of the slick gene into dairy cattle and the effect on farm profitability in New Zealand. Performances between the first cohort born in 2017, comprised of slick (SL) cows (n = 6) and the contemporary (CT) cows (n = 144) were compared across four production years (2019/20 to 2022/23), whilst a second cohort born in 2019, comprised of SL cows (n = 20) and the CT cows (n = 105) were compared across two production years (2021/22 and 2022/23). For the 2017-born group, milk volume, fat, and protein yields of SL cows were 9%, 13%, and 9% lower than those of CT cows. Liveweight (LW), body condition score (BCS), somatic cell score (SCS), and survival rate of SL cows were 6%, 11%, 18%, and 31% greater, respectively, than those of CT cows. Moreover, the age at first calving (AFC) of SL cows was 25 ± 8 days greater than that of CT cows, but calving interval (CI) and inseminations per pregnancy were not different between SL and CT cows. Slick cows required more calving assistance, however, the level of veterinary assistance for calving was lower than CT cows in the 2017-born group. Income from milk over feed cost (IOFC) for SL cows was 17% lower than that for CT cows. In the 2019-born group, milk volume, fat, and protein yields of SL cows were 33%, 29%, and 24% lower, respectively, than those of CT cows. The survival rate of SL cows was 19% lower than that of CT cows, whilst LW, BCS, and SCS of SL cows were 4%, 8%, and 6% greater than those for CT cows. The AFC for SL cows was 11 ± 4 days greater than that for CT cows, but the CI and inseminations per pregnancy were not different. Slick cows required more calving assistance both at a slight and veterinary assistance level, while CT cows required more significant level calving assistance in the 2019-born group. The IOFC for SL cows was 43% lower than that for CT cows in the 2019-born group.
dc.identifier.urihttps://mro.massey.ac.nz/handle/10179/69453
dc.language.isoen
dc.publisherMassey University
dc.rightsThe authoren
dc.subject.anzsrc300104 Genetically modified animalsen
dc.titleEffect of incorporation of a heat tolerance gene into dairy cattle and effect on farm profitability : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatū, New Zealand. EMBARGOED until 18th December 2024.
dc.typeThesis
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