Altering pre-lambing nutrition to impact colostrum and milk production in ewes, immunity transfer and growth of lambs

    Research output: ThesisDoctoral Thesis

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    Abstract

    Lamb mortality from birth to weaning causes major reproductive wastage in sheep breeding enterprises. The practices producers undertake on farm can alter lamb survival, especially supplementation, scanning and vaccination practices. It is also important for producers to be aware of mortality rates on farm to determine the effectiveness of these practices.
    A New South Wales producer survey investigated producer practices and perceptions on lamb survival. A comparison to published data indicated producers may be underestimating lamb mortality rates, with nearly half of producers estimating <10% mortality of lambs from birth to marking, compared to published data estimating 20-25%. This may lead to producers being unable to determine the actual benefit of practices such as supplementation and vaccination to increase lamb survival, therefore they may not supplement due to not realising the number of lambs lost. In comparison to literature on the cause of lamb deaths, producers also estimated that more lambs died from predation, which is concerning as the primary cause of death could be a starvation or exposure which could be altered by supplementation, with predation as a secondary cause of death. It is apparent extension services need to educate producers on lamb mortality which may be beneficial to increase production on farm, allowing producers to make informed decisions regarding supplementation and mortality. Ewe supplementation in late gestation and lactation can improve lamb survival increasing immunity transfer, colostrum and milk production. The value of various supplements for pregnant and lactating ewes to increase colostrum and milk production is based on the ability of the supplement to affect lactogenesis and energy production. A series of experiments were undertaken to determine the effectiveness of nutritional supplementation strategies on colostrum and milk production, immunity transfer and lamb weight gain. Supplementation of ewes for one week prior to lambing until 2-10 days post-lambing with 500g barley and 120g of canola meal did not affect colostrum or colostral IgG production compared to barley supplementation alone. Similarly, supplementation with 5 g/hd.day niacin for two-weeks pre-lambing did not alter colostrum production or IgG concentration. Supplementation of ewes with barley and canola meal or niacin using the tested supplementation practice was of limited commercial viability and would not be recommended to increase colostrum production.
    Supplementation of 500g maize and 3g of rumen-protected methionine to naturally mated ewes for at least seven days pre-lambing through to four weeks post-lambing increased milk production without altering colostrum production, immunoglobulin production and lamb growth rates compared to unsupplemented ewes. At similar energy intakes maize and methionine supplemented ewes had higher body condition scores four weeks post-lambing and higher β-hydroxybutyrate concentrations post-lambing compared to control ewes. β-hydroxybutyrate increase is possibly associated with the catabolism body fat, allowing for greater energy production leading to numerically higher colostrum production and increased milk production, however this was not able to be determined under the current study design. As body condition increased the ewes were not reliant on body reserves to meet the needs for production, leading to an increase in condition over lambing. Due to the benefits of supplementing maize and methionine, further research is required to determine the economics of supplementation and whether the increased lactational performance can alter lamb survival and growth.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • Charles Sturt University
    Supervisors/Advisors
    • Friend, Michael, Principal Supervisor
    • Abuelo Sebio, Angel, Co-Supervisor
    • Robertson, Susan, Co-Supervisor
    Place of PublicationAustralia
    Publisher
    Publication statusPublished - 2022

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