Hay to Reduce Dietary Cation-Anion Difference for Dry Dairy Cows

• Published in: Journal of dairy science 2008-04, Vol.91 (4), p.1585-1596
• Main Authors: Charbonneau, E., Chouinard, P.Y., Tremblay, G.F., Allard, G., Pellerin, D.
• Format: Article
• Language: English
• Subjects: Acid-Base Equilibrium - physiology; Animal productions; Animals; Anions; Biological and medical sciences; blood calcium; Blood Chemical Analysis - veterinary; Calcium - blood; Calcium - urine; Cations; Cattle - blood; Cattle - physiology; Cattle Diseases - prevention & control; cow feeding; dairy cows; Diet - veterinary; dietary cation anion difference; dry matter intake; dry period; Eating; Edetic Acid - administration & dosage; experimental diets; Feces - chemistry; Female; Food industries; Fundamental and applied biological sciences. Psychology; hay; Hydrochloric Acid - administration & dosage; Hypocalcemia - prevention & control; Hypocalcemia - veterinary; metabolic studies; metabolism; Milk and cheese industries. Ice creams; nonlactating cow; Phleum - chemistry; Phleum - metabolism; Phleum pratense; ruminant nutrition; Terrestrial animal productions; Time Factors; Urine - chemistry; Vertebrates
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2007-0775

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 3×3 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. 3.8mM) and HCO3− (23 vs. 27mM), 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. 708min); 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.