Download DIETARY CATION-ANION DIFFERENCE EFFECTS ON FRESH HOLSTEIN AND JERSEY COWS

DIETARY CATION-ANION DIFFERENCE EFFECTS ON
FRESH HOLSTEIN AND JERSEY COWS
Wenping Hu, Michael R. Murphy, Peter D. Constable, and Elliot Block
TAKE HOME MESSAGES
•
Although breed differences were expected and significant statistically, intake of dry
matter and performance of fresh cows were not improved when dietary cation-anion
difference increased from 22 to 47 meq/100 g of dry matter. This was likely because
cows immediately after calving respond more variably to dietary treatments and that
makes treatment effects more difficult to detect.
•
As in the companion experiment, an elevated blood plasma essential amino acid to
nonessential amino acid ratio with increasing dietary cation-anion difference indicated
that nitrogen metabolism in the rumen was affected, probably resulting in more microbial
protein flowing to the small intestine.
INTRODUCTION
The major effects of dietary cation-anion difference (DCAD, milliequivalents of Na + K – Cl – S
per 100 grams of dry matter) on animal performance are thought to be linked to acid-base
regulation. Manipulating DCAD might benefit cows postpartum; however, little information was
available about DCAD effects on cows immediately after calving. Our objective was to examine
the effect of DCAD on performance, acid-base status, and protein and mineral metabolism in
cows postpartum.
MATERIALS AND METHODS
Sixteen Holstein and 8 Jersey multiparous cows were used immediately after calving to compare
two DCAD [22 or 47 milliequivalents/100 g of dry matter] in a completely randomized design.
The corn silage based diets contained 19% crude protein, 25% neutral detergent fiber, 15% acid
detergent fiber, and 1.69 Mcal of NEL/kg (on a dry matter basis). An additional 5 lb of alfalfa
hay was fed during the first 5 days postpartum then milk, blood, and urine samples were
collected weekly for 6 weeks.
RESULTS AND DISCUSSION
Although breed differences were expected and significant statistically (Table 1), DCAD did not
affect dry matter intake, or milk production or composition.
Table 1. Dry matter intake and production of milk and milk components.
DCAD1
Breed
Item
22
47
Holstein
Jersey
Dry matter intake, lb/day
40.1
40.4
43.9
36.8
Body weight, lb
1222
1191
1402
1010
Milk
Yield, lb/day
73.9
73.4
84.2
63.1
4% FCM, lb/day
72.3
73.4
78.5
67.3
Fat, %
3.96
4.11
3.58
4.49
Protein, %
3.11
3.00
2.74
3.38
Lactose, lb/day
3.62
3.62
4.15
3.09
SNF, %
8.95
8.83
8.57
9.22
SNF, lb/day
6.59
6.42
7.19
5.82
1
DCAD: dietary cation-anion difference, milliequivalents of (Na + K – Cl – S)/ 100 g of
DM.
Elevated plasma branched chain amino acids and ratios of essential amino acids to total amino
acids in cows with DCAD of 47 versus 22 meq/100 g of dry matter again indicated that nitrogen
metabolism in the rumen was affected, probably resulting in more microbial protein flowing to
the small intestine. Urinary pH tended to increase with DCAD. Higher net acid excretion in cows
with DCAD of 22 versus 47 meq/100 g of dry matter suggested that net acid excretion was much
more indicative of acid load than blood acid-base parameters in cows postpartum.
Intake of dry matter and performance of fresh cows were not improved when DCAD increased
from 22 to 47 meq/100 g of dry matter, likely because cows immediately after calving respond
more variably to dietary treatments and that makes treatment effects more difficult to detect.