Continuous and Long-Term Measurement of Reticuloruminal pH in Grazing Dairy Cows by an Indwelling and Wireless Data Transmitting Unit

Abstract

The aim of the present study was the continuous measurement of ruminal pH in grazing dairy cows to monitor the diets effects on ruminal pH value. A novel indwelling pH-measurement and data transmitting system was given to 6 multiparous cows orally. Ruminal pH was measured every 600 sec over a 40 d period. After barn feeding and changeover to pasture, the following 3 treatments (2 cows/treatment) were included in the measurement period: continuous grazing (G), continuous grazing plus 4 kg/d of hay fed twice daily (GH), and continuous grazing plus 4 kg/d of concentrate (GC). Ruminal pH decreased significantly (P < 0.05) from 6.58 ± 0.15 to pH 6.19 ± 0.19 during feed changeover to pasture. Mean ruminal pH for G, GH, and GC was 6.36, 6.56, and 6.01. Mean 24-h minimum pH was 5.95, 6.20 and, 5.58. The time pH was below 6.3, 6.0, 5.8, and 5.5, for G it was 583, 91, 26, and 3 min/d, for GH it was 97, 12, 0, and 0 min/d and for GC it was 1126, 621, 347, and 101 min/d, respectively. Results were significantly influenced by the diet. The indwelling pH-measurement and data transmitting system is a very useful and proper tool for long-term measurement of ruminal pH in cows.

Figure 1

Phase patterns of mean reticuloruminal pH during the first 26 days of examination (feed changeover period) from barn feeding (phase 1), 10 h/d-pasture (phase 2), and 20 h/d (phases 3–7). Vertical bars indicate SE of phase means. ¹Least squares means, ²SE of least squares means.

Figure 2

Diurnal patterns of mean reticuloruminal pH of cows from group G and GC (20 hours grazing per day) between day 25 and day 30 with the diet change of group GC to additional concentrate feeding (GC) on day 27, whilst group G was still receiving only pasture (20 h/d). Group GH is not shown in this figure due to clear arrangement.