Browsing by Author "Lean, I J"

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    Publication
    Impact of dietary protein levels on adrenaline sensitivity of beef cattle
    (Wageningen Acad Publ, 2019)
    Alvarenga, F A P 
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    Lean, I J
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    Alvarenga, T I R C 
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    McGilchrist, P 

    The aim of the current study was to evaluate the impact of dietary protein on adrenaline sensitivity in an effort to determine if this is increasing the incidence of dark cutting in beef cattle. Eighteen Angus steers, approximately 12 month old, with an average live weight of 284±23 kg were used. The animals were randomly split into 10.4, 20.1 and 29.7% dietary protein levels and were challenged with 3 levels of adrenaline (1, 3 and 5 ug/kg live weight). The diets were balanced according to NRC (2016) with minerals and metabolizable energy remained constant for a growth daily gain of 1 kg. Plasma was analysed for non-esterified fatty acids (NEFA) and glucose concentration and area under curve over time 10 minutes post-challenge (AUC10) was calculated to reflect the tissue responses to adrenaline. There was a significant effect of diet on glucose basal concentration where 10% dietary protein had a higher adrenaline response within the liver or muscle comparing to 20 and 30% dietary protein.

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    Publication
    On farm factors increasing dark cutting in pasture finished beef cattle
    (Elsevier BV, 2018-10)
    Loudon, K M W
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    Lean, I J
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    Pethick, D W
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    Gardner, G E
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    Grubb, L J
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    Evans, A C
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    McGilchrist, P 
    The on-farm factors increasing the incidence of dark cutting were studied in 3145 pasture raised cattle consigned in 66 lots. Animal, environmental and farm management factors were recorded and pasture quantity, quality and mycotoxin concentrations were measured. The relative risk of dark cutting decreased by 26% in cattle grazing pastures with magnesium concentrations exceeding 0.24%. There was a 50% increase in relative dark cutting risk of cattle drinking from dams compared to drinking from troughs. Feeding supplements (hay/silage) in the last 7 days prior to slaughter reduced the relative risk of dark cutting by 25%. A high prevalence of mycotoxins was detected in pastures across all farms. In this case pasture ergot alkaloid concentrations above 600PPB increased the relative risk of dark cutting by 45%, while the presence of FumonisinB1 increased risk by 58%. In contrast the presence of 3acetyldeoxynivalenol reduced the relative dark cutting risk by 37%. Sex also affected the incidence of dark cutting, with heifers less likely to cut dark than steers by 47%.
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    Publication
    Short term magnesium supplementation to reduce dark cutting in pasture finished beef cattle
    (Elsevier BV, 2021-10)
    Loudon, K M W
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    Tarr, G
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    Lean, I J
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    McLerie, L
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    Leahy, N
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    Pethick, D W
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    Gardner, G E
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    McGilchrist, P 

    This study assessed the capacity of magnesium supplementation to reduce muscle glycogen loss, ultimate pH and increase plasma magnesium in pasture fed slaughter cattle. Beef cattle (n = 1075) from 14 farms were supplemented with or without magnesium pellets for 7–14 days prior to slaughter. Magnesium was allocated at 9.83 g of elemental magnesium per head per day, while the control diet was balanced to be isoenergetic and isonitrogenous, but contained no added magnesium. Groups of cattle (n = 44) were slaughtered at the same processing plant over two consecutive seasons, from August – September 2016 to May – July 2017.

    Magnesium supplementation increased muscle glycogen (P < 0.01) in cattle supplied from 2 of 14 farms, and increased plasma magnesium in 4 of 14 farms (P < 0.01). Magnesium supplementation had no effect on overall incidence of ultimate pH between the magnesium and control supplementation groups. The benefits of short term magnesium supplementation prior to slaughter was inconsistent for protecting muscle glycogen.