title: Grazing behavior affects daily ruminal pH and NH3 oscillations of dairy cows on pasture.
abstract: Grazing behavior of Holstein cows in late lactation at 2 pasture allowances without or with supplementation was studied in a single reversal design. Twenty multiparous cows (4 ruminally cannulated) grazed a bromegrass/orchardgrass pasture offered at 2 pasture allowances: 1) low, and 2) high, with 25 and 40 kg/d of DM per cow, respectively. Half of the cows were supplemented with a mineral/vitamin mixture (1 kg/ d of the mix in a corn/molasses carrier) and the other half supplemented with a corn-based concentrate (1 kg of concentrate per 4 kg of milk). Automatic behavior recorders were used to measure grazing time and number of bites. For the mineral/vitamin mixture-supplemented cows, grazing time and number of bites after the p.m. milking was greater and ruminal pH was numerically lower at the high pasture allowance. For the concentrate-supplemented cows, grazing behavior and ruminal pH did not differ between the 2 pasture allowances. Pattern of grazing time of mineral/vitamin mixture-supplemented and concentrate-supplemented cows influenced daily oscillations of ruminal pH and NH3-N concentration. Pasture allowance affected grazing behavior of mineral/vitamin mixture-supplemented cows; however grazing behavior of concentrate-supplemented cows was not affected by pasture allowance.
authors.affiliation: Department of Dairy and Animal Science, The Pennsylvania State University, University Park, 16802, USA. fbargo@agro.uba.ar
authors.forename: F
authors.initials: F
authors.lastname: Bargo
authors.forename: L D
authors.initials: LD
authors.lastname: Muller
mesh_terms: D000641:Ammonia / Q000032:analysis*; D000818:Animals; D001826:Body Fluids / Q000737:chemistry; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D004032:Diet; D019587:Dietary Supplements; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007774:Lactation; D008903:Minerals / Q000008:administration & dosage; D012417:Rumen / Q000737:chemistry* / Q000378:metabolism; D013048:Specimen Handling / Q000379:methods / Q000662:veterinary; D013997:Time Factors; D014815:Vitamins / Q000008:administration & dosage; D003313:Zea mays
chemical_list: D008903:Minerals; D014815:Vitamins; D000641:Ammonia