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Unformatted text preview: J. Dairy Sci. 85:11651175 American Dairy Science Association, 2002. Effect of Concentrate Level and Feeding Management on Chewing Activities, Saliva Production, and Ruminal pH of Lactating Dairy Cows M. Maekawa,* K. A. Beauchemin, and D. A. Christensen* *Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada, S7N 5A8 Livestock Science Section, Agriculture and Agri-Food Canada, Research Centre, Lethbridge, Alberta, Canada, T1J 4B1 ABSTRACT Eight ruminally cannulated lactating Holstein cows were used in a double 4 4 Latin square to determine the effects of 1) proportion of barley silage [40, 50, and 60% of dry matter (DM)] in the diet, and 2) feeding a total mixed ration (TMR) compared with separate ingredients (SI) on chewing activities, saliva produc- tion, and ruminal pH. Although cows fed SI were offered a diet containing 50% silage, they actually consumed a diet containing 43% silage (DM basis). Dry matter intake and milk yield were similar for all diets (18.2 kg of DM/d and 27.2 kg/d, respectively). Cows fed the 40% silage TMR spent more time eating than cows fed SI (243 vs. 198 min/d), but rumination time was similar (546 min/d). Eating time was similar among the TMR diets, but rumination time increased from 498 to 516 and 584 min/d as silage in the TMR increased from 40 to 50, and then to 60%, respectively. The secretion of saliva per gram of feed was 4.43, 3.18, and 1.19 ml/g of DM with consumption of silage, TMR, and concentrate, respectively. Resting salivation rate was similar for all diets (101 ml/min). Regardless of the diet, cows secreted 239 17 L/d of saliva, and ruminal pH was below 5.8 for 10 h/d. Results indicated increased chewing time did not increase total daily saliva secretion because increased eating and ruminating saliva was associated with decreased resting saliva. Feeding SI increased the risk of acidosis, because cows ate a higher proportion of concentrate than intended. ( Key words: chewing, saliva production, feeding man- agement, ruminal pH) Abbreviation key: : F:C = forage-to-concentrate ratio, MP = multiparous cows, PP = primiparous cows, SI = diet with ingredients allocated separately. Received March 5, 2001. Accepted November 23, 2001. Corresponding author: K. A. Beauchemin; e-mail: beauchemin @em.agr.ca. 1 LRC contribution number 38701013. 1165 INTRODUCTION Subclinical ruminal acidosis is a temporarily altered state of the rumen, whereby pH is reduced below 5.8. The consequences can be reduced fiber digestion, incon- sistent feed intake, diarrhea, decreased milk fat, lami- nitis, and other health disorders (Nocek, 1997). Thus, subclinical ruminal acidosis can be a costly problem for commercial dairy herds (Stone, 1999)....
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This note was uploaded on 09/19/2011 for the course ANS 5446 taught by Professor Brown during the Spring '08 term at University of Florida.
- Spring '08