Hay to reduce dietary cation-anion difference for dry dairy cows.
Timothy grass has a lower dietary cation-anion difference [DCAD = (Na + K) - (Cl + S)] than other cool-season grass species. Growing timothy on low-K soils and fertilizing it with CaCl2 could further decrease its DCAD. The objective of this study was to evaluate the effects of feeding low-DCAD timothy hay on dry dairy cows. Six nonpregnant and nonlactating cows were used in a replicated 3 x 3 Latin square. Treatments were as follows: 1) control diet (control; DCAD = 296 mEq/kg of dry matter); 2) low-DCAD diet based on low-DCAD timothy hay (L-HAY; DCAD = - 24 mEq/kg of dry matter); and 3) low-DCAD diet using HCl (L-HCl; DCAD = - 19 mEq/kg of dry matter). Decreasing DCAD with L-HAY had no effect on dry matter intake (11.8 kg/d) or dry matter digestibility (71.5%). Urine pH decreased from 8.21 to 5.89 when L-HAY was fed instead of the control. Blood parameters that decreased with L-HAY were base excess (- 0.4 vs. 3.8 mM) and HCO3- (23 vs. 27 mM), and blood parameters that increased were Ca2+ (5.3 vs. 5.1 mg/dL), Cl- (30.5 vs. 29.5 mg/dL), and Na+ (60.8 vs. 60.1 mg/dL). Compared with the control, L-HAY resulted in more Ca in urine (13.4 vs. 1.2 g/d). Comparing L-HAY with L-HCl, cow dry matter intake tended to be higher (11.5 vs. 9.8 kg/d), and blood pH was higher (7.37 vs. 7.31). Urine pH; total dry matter; Ca, K, P, and Mg apparent absorption; and Ca, K, Na, Cl, S, P, and Mg apparent retention were similar. Absorption as a percentage of intake of Na and Cl was lower for L-HAY as compared with L-HCl. In an EDTA-challenge test, cows fed L-HAY regained their initial level of blood Ca2+ twice as quickly as the control treatment (339 vs. 708 min); there were no differences between L-HAY and L-HCl. This experiment confirms that feeding low-DCAD hay is an effective means of decreasing the DCAD of rations and obtaining a metabolic response in dry dairy cows.
Charbonneau
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Département des Sciences Animales, Université Laval, Québec, Québec, Canada G1K 7P4. edith.charbonneau@fsaa.ulaval.ca
Chouinard
P Y
PY
Tremblay
G F
GF
Allard
G
G
Pellerin
D
D
D000136:Acid-Base Equilibrium / Q000502:physiology*; D000818:Animals; D000838:Anions; D001774:Blood Chemical Analysis / Q000662:veterinary; D002118:Calcium / Q000097:blood / Q000652:urine; D002412:Cations; D002417:Cattle / Q000097:blood / Q000502:physiology; D002418:Cattle Diseases / Q000517:prevention & control*; D004032:Diet / Q000662:veterinary*; D004435:Eating; D004492:Edetic Acid / Q000008:administration & dosage; D005243:Feces / Q000737:chemistry; D005260:Female; D006851:Hydrochloric Acid / Q000008:administration & dosage; D006996:Hypocalcemia / Q000517:prevention & control / Q000662:veterinary*; D031784:Phleum / Q000737:chemistry / Q000378:metabolism*; D013997:Time Factors; D014556:Urine / Q000737:chemistry
D000838:Anions; D002412:Cations; D004492:Edetic Acid; D006851:Hydrochloric Acid; D002118:Calcium