Impact of severity of ruminal acidosis on feed-sorting behaviour of beef cattle
Devries, T.J., Schwaiger, T., Beauchemin, K.A., Penner, G.B. (2014). Impact of severity of ruminal acidosis on feed-sorting behaviour of beef cattle, 54(9), 1238-1242. http://dx.doi.org/10.1071/AN14227
The objective of this study was to determine how feed sorting changes in response to the severity of an induced episode of acute ruminal acidosis. Sixteen Angus heifers (261 ± 6.1 kg; bodyweight (BW) ± s.e.m.) were adapted to a high-grain diet (9% forage) before a ruminal acidosis challenge. Ruminal acidosis was induced by restricting feed to 50% of dry matter intake (DMI) as a proportion of BW for 24 h, followed by an intra-ruminal infusion of ground barley at 10% of DMI as a proportion of BW. Ruminal pH and feed sorting were monitored for 8 days (Base) before the challenge and on the challenge (CH) day. Ruminal pH data (duration (min) and area above the curve (min × pH) of pH <5.5) were recorded using an indwelling measurement system. To assess feed sorting, feed and orts were sampled daily and subjected to particle-size analysis. The particle separator had three screens (19, 8, 1.18 mm) and a bottom pan, resulting in four fractions (long, medium, short, fine). Sorting (%) was calculated as the actual intake/predicted intake of each particle fraction. During the Base period and the CH day, heifers sorted for long, medium and short particles, and sorted against fine particles. During the Base period, heifers experienced ruminal pH <5.5 for 489 ± 73 min/day with an area of 154 ± 29 (pH × min)/day; on the CH day, the duration increased to 1020 ± 75 min/day with an area of 631 ± 102 (pH × min)/day. A greater change in duration of pH <5.5 was associated with a greater increase in sorting for long and medium particles. A greater change in the area of pH <5.5 was associated with a greater increase in sorting for long particles and against fine particles. Overall, results show that cattle that experienced a greater degree of acidosis partially coped by sorting their ration more to consume a greater proportion of long, fibrous particles. © CSIRO 2014.
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