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      Evaluation Of the NRC 1996 winter feed requirements for beef cows In western Canada

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      Date
      2007-02-28
      Author
      Bourne, Jodi Lynn
      Type
      Thesis
      Degree Level
      Masters
      Metadata
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      Abstract
      A trial was conducted to evaluate the accuracy of the 1996 NCR beef model to predict DMI and ADG of pregnant cows under western Canadian conditions. Over two consecutive years, 90 Angus (587±147 kg) cows assigned to 15 pens (N=6) were fed typical diets ad libitum, formulated to stage of pregnancy. Data collection included pen DMI and ADG (corrected for pregnancy), calving date, calf weight, body condition scores and ultrasound fat measurements, weekly feed samples and daily ambient temperature. DMI and ADG for each pen of cows in each trimester was predicted using the computer program “Cowbytes” based on the 1996 NRC beef model. The results indicate that in the 2nd and 3rd trimester of both years the model under predicted (P≤0.05) ADG based on observed DMI. Ad libitum intake was over predicted (P≤0.05) during the 2nd trimester, and under predicted (P≤0.05) during the 3rd trimester of pregnancy. A second evaluation was carried out assuming thermal neutral (TN) conditions. In this case, it was found that during the 2nd and 3rd trimesters there was an over prediction (P≤0.05) of ADG relative to observed. Under these same TN conditions, the ad libitum intake of these cows was under predicted (P≤0.05) for both the 2nd and 3rd trimesters. These results suggest current energy equations for modelling environmental stress, over predict maintenance requirements for wintering beef cows in western Canada. The results also suggest that the cows experienced some degree of cold stress, but not as severe as modelled by the NRC (1996) equations. Further research is required to more accurately model cold stress felt by mature cattle, and their ability to acclimatise to western Canadian winter conditions.
      Degree
      Master of Science (M.Sc.)
      Department
      Animal and Poultry Science
      Program
      Animal and Poultry Science
      Supervisor
      McKinnon, John J.
      Committee
      Lardner, Bart; Christensen, David A.; Buchanan, Fiona C.; Basarab, John
      Copyright Date
      February 2007
      URI
      http://hdl.handle.net/10388/etd-02282007-113710
      Subject
      NRC Evaluation
      beef cow performance prediction
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