Feeding Lactating Dairy Cattle Long Hay Separate from the TMR Can Maintain DMI During Incidents of Low Rumen pH

Monday, July 21, 2014: 12:15 PM
2103B (Kansas City Convention Center)
Alanna D Kmicikewycz , The Pennsylvania State University, University Park, PA
A. J. Heinrichs , The Pennsylvania State University, University Park, PA
Abstract Text:

The objective of this study was to investigate effects of orchardgrass hay (H) quality and feeding method on rumen pH and feed preference in lactating dairy cows.  Eight rumen-cannulated Holstein cows (104 ± 34 DIM, 601 ± 116 kg, and parity of 2.38 ± 1.69; mean ± SD) were used in a replicated 4 × 4 Latin Square.  Each period encompassed 21 d divided into 5 phases: adaptation, d 1 to 14, ad libitum TMR; baseline, d 15 to 17, ad libitum TMR; restricted feeding, d 18, cows fed for 75% of baseline DMI; challenge, d 19, 4 kg (as-fed) fine ground wheat mixed into the digesta of each cow via rumen cannula before feeding; and recovery, d 20 to 21, ad libitum TMR.  Cows were assigned to squares by parity and randomly assigned to treatments.  Treatments were: corn silage (CS) with coarse H TMR (CC), CS and fine H TMR (CF; both hays chopped and included in TMR), CS TMR with 5.2% supplemental long coarse H (TMR+C), and CS TMR with 5.2% supplemental long fine H (TMR+F; both hays fed separate from TMR).  Coarse H was 8.6% CP and 67.1% NDF, fine H was 14.4% CP and 56.2% NDF.  Animals were housed individually, milked 2X/d, and fed 1X/d for 10% refusal rate.  Data was analyzed using MIXED procedure of SAS.  Rumen challenge decreased weighted average rumen pH from 5.72 to 5.51.  Cows fed TMR+C had higher rumen pH compared to CC and TMR+F on d 19.  During d 20, cows fed H had higher rumen pH than cows fed supplemental long H.  Cows fed supplemental long H had greater DMI during baseline and challenge d compared to TMR H treatments.  Minimal differences among diets were found for TMR particle size selection during challenge d; however, cows had a greater preference for fine long H during recovery d.  Milk production averaged 38.3 kg/d and did not differ among treatments.  Fat, protein, and lactose yields were also not different among treatments.  Milk fatty acid profile was altered by treatment.  The TMR+C and CF treatments increased production of conjugated linoleic acid (CLA) cis-9, trans-11 (P = 0.02).  Results of this study indicate that feeding TMR plus supplemental long H can maintain DMI during incidents of and recovery from periods of low ruminal pH.

Keywords: subacute ruminal acidosis, ruminal pH, particle size