Summary: | The objectives of this study were to evaluate the influence of RFI and cow age on the supplement intake and grazing behavior of beef cattle. Average daily supplement intake (kg/cow/d) displayed an RFI × cow age interaction (<i>p</i> < 0.01), with a linear increase in average daily supplement intake with increasing RFI of 3-year-old cows (<i>p</i> < 0.01). Average daily supplement intake (g ∙ kg BW<sup>−1</sup> ∙ d<sup>−1</sup>) displayed an RFI × cow age interaction (<i>p</i> < 0.01), with a quadratic effect on supplement intake of 3-year-old cows (<i>p</i> = 0.01). Cow age displayed a quadratic effect on variation of supplement intake (<i>p</i> < 0.01), where 1-year-old cows had a greater CV of supplement intake than all other cow ages (<i>p</i> < 0.01). Distance traveled displayed a cow age × RFI interaction (<i>p</i> = 0.02), where high-RFI 5-year-old cows traveled further per day than low 5-year-old RFI cows. The probability of grazing site selection was influenced by cow age (<i>p</i> ≤ 0.03). In summary, heifer post-weaning RFI had minimal effects on beef cattle performance, grazing behavior, or resource utilization; however, cow age impacted both grazing behavior and resource use.
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