Timothy Hay with a Low Dietary Cation-Anion Difference Improves Calcium Homeostasis in Periparturient Holstein Cows

• Published in: Journal of dairy science 2008-05, Vol.91 (5), p.1959-1968
• Main Authors: Penner, G.B., Tremblay, G.F., Dow, T., Oba, M.
• Format: Article
• Language: English
• Subjects: Animal productions; Animals; Anions - analysis; Biological and medical sciences; calcium; Calcium - blood; Calcium Chloride - administration & dosage; calcium homeostasis; Cations - analysis; Cattle - physiology; dairy cow; dairy cows; Diet; dietary cation anion difference; dietary minerals; Female; Fertilizers; Food industries; Fundamental and applied biological sciences. Psychology; hay; Holstein; homeostasis; Homeostasis - physiology; Hydrogen-Ion Concentration; hypocalcemia; Kinetics; maternal nutrition; Milk and cheese industries. Ice creams; mineral metabolism; Parturition; Phleum - chemistry; Phleum - growth & development; Phleum pratense; Postpartum Period; Pregnancy; ruminant nutrition; Terrestrial animal productions; timothy hay; Vertebrates
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2007-0882

The current study was undertaken to evaluate the effects of feeding timothy (Phleum pratense L.) hay differing in dietary cation-anion difference (DCAD) on the capability of cows to maintain calcium homeostasis around parturition. We hypothesized that feeding low-DCAD timothy hay during the prepartum period would induce a mild metabolic acidosis prepartum and improve calcium homeostasis postpartum with no effect on dry matter intake. Forty-one dry pregnant Holstein cows entering their second lactation or greater were used in a randomized complete block design. Timothy hay was obtained from an established timothy stand under a pivot irrigation system. Low-DCAD timothy hay was produced by fertilizing the area between the second and third pivot towers at a rate of 224kg of CaCl2/ha, and control timothy hay (high DCAD) was grown on the area between the fourth and fifth pivot towers of the same field. The chloride concentration was 1.07 and 0.15% on a dry matter (DM) basis, and the DCAD was 1.2 and 21.6 mEq/100g of DM for the low- and high-DCAD timothy hay, respectively. Experimental diets, containing timothy hay at 63% of dietary DM, were fed ad libitum starting 30 d before the expected calving date. The DCAD values were 1.6 vs. 14.5 mEq/100g of DM for the low- and high-DCAD timothy-based diets, respectively. At the beginning of the study, urine pH and blood bicarbonate concentration averaged 8.22±0.06 and 28.5±0.3mM, respectively. The low-DCAD timothy diet decreased urine pH compared with the high-DCAD timothy diet on d 21 (7.75 vs. 8.31), d 14 (7.69 vs. 8.22), and d 7 (7.50 vs. 8.19) before calving, and it also decreased the prepartum blood bicarbonate concentration by 2mM. In addition, cows fed the low-DCAD timothy diet had greater blood ionized calcium concentration prepartum (1.22 vs. 1.19mM), greater blood ionized calcium concentration at 0 and 8h after calving, and similar prepartum dry matter intake. These results indicate that timothy hay differing in DCAD affects the acid-base balance of periparturient dairy cows, and that low-DCAD timothy hay improves calcium homeostasis postpartum with no negative effect on dry matter intake.