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Title: Technical note: daily variation in intake of a salt-limited supplement by grazing steers

Author
item REUTER, RYAN - Oklahoma Agriculture Experiment Station
item Moffet, Corey
item HORN, GERALD - Oklahoma Agriculture Experiment Station
item ZIMMERMAN, SCOTT - C-Lock Inc
item BILLARS, MIKE - C-Lock Inc

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2017
Publication Date: 5/23/2017
Citation: Reuter, R.R., Moffet, C., Horn, G.W., Zimmerman, S., Billars, M. 2017. Technical Note: Daily variation in intake of a salt-limited supplement by grazing steers. Professional Animal Scientist. 33:372-377.

Interpretive Summary: Limiting intake of free-choice supplements with salt is a widely-implemented practice, and can be used to achieve targeted levels of supplement intake for herds over time. However, intake of self-fed, salt-limited supplements varies considerably among animals within the herd and among days for the same animal. This study demonstrated that self-fed, salt-limited supplements are not sufficient for precisely controlling the amount of supplement an individual animal gets to improve efficiency on an individual animal basis. It also suggests the need for other strategies, such as improved limiters or electronic feeders. Additional research is needed to understand and manipulate the behavior and nutrition of grazing cattle when attempting to manage at the level of individual animal or animal on a given day.

Technical Abstract: The objective of this research was to develop and test an automated supplement intake measurement system (SmartFeed, SF) in grazing trials. The SF was developed by C-lock Inc., (Rapid City, SD), and was designed using a stainless steel feed bin with load cells and an radio frequency identification device (RFID) reader. The testing approach was to use salt to limit intake of a self-fed supplement in SF, and measure variation of intake. Over a 14-d test period, 15 RFID-tagged steers (256 ± 31 kg mean BW) grazing dormant native range pasture had ad-libitum, 24-h access to SF. The supplement provided in SF was 55% supplement (80% soybean meal, 20% soybean hulls, as-fed basis) and 45% fine mixing salt (as-fed basis). Supplement (including salt) intake was 1.21 ± 1.15 kg per day per animal (as-fed basis). The high CV (95%) indicated that there is considerable variation in daily supplement intake among group-supplemented steers. Overall, SF has the potential to measure individual animal supplement intake in grazing experiments. However, animal- and animal × day-level variation of supplement intake is considerable. Strategies other than using salt as a limiter may offer the potential to more precisely control supplementation, while improving experimental design and efficiency.