Negative dietary cation-anion difference and amount of calcium in prepartum diets: Effects on milk production, blood calcium, and health

Abstract

Acidogenic prepartum diets with negative dietary cation-anion difference (DCAD) induce compensated metabolic acidosis, which stimulates calcium (Ca) mobilization before calving and decreases clinical and subclinical hypocalcemia postpartum. This strategy is often combined with limiting dietary Ca concentrations, which historically has been used to mobilize Ca prepartum to prepare cows for lactation. Supplemental dietary Ca in combination with a negative DCAD formulation that does not reverse the effect of compensated metabolic acidosis may be beneficial. Our objective was to determine the effects of prepartum dietary strategies on dry matter intake (DMI), milk production, peripartal Ca status, and health during the transition period in multiparous Holstein cows (n = 81). Treatments during the last 28 d before calving were:(1) positive DCAD diet, +6 mEq/100 g of DM, target urine pH >7.5, low dietary Ca (0.40% DM; CON); (2) negative DCAD diet, −24 mEq/100 g of DM, target urine pH 5.5 to 6.0, low dietary Ca (0.40% DM; ND); or (3) negative DCAD diet, −24 mEq/100 g of DM, target urine pH 5.5 to 6.0, , high dietary Ca (2.0% DM; NDCA). Preplanned treatment contrasts were:(1) CON versus (ND and NDCA), and (2) ND versus NDCA. Individual DMI were recorded daily. Cows were milked 3 times daily, with individual DMI and milk yield summarized by week. Whole blood sampled at calving and 24 h, 48 h, and 4 d after calving was analyzed for ionized Ca concentration, and serum was analyzed for total Ca. Prepartum urine pH for cows fed ND or NDCA averaged 5.7, whereas cows fed CON remained >7.5. During the 3 wk before calving, cows fed CON had greater DMI than cows fed ND or NDCA, with NDCA greater than ND. Postpartum DMI (% of body weight) tended to be less for cows fed CON than for those fed ND or NDCA prepartum. Thresholds for subclinical hypocalcemia were ionized Ca <1.0 mM at 24 h, and total Ca ≤2.125 mM at 48 h after calving. On average, blood Ca for cows fed CON indicated subclinical hypocalcemia, whereas blood Ca for cows fed ND or NDCA was greater than subclinical hypocalcemia thresholds for both ionized Ca and total Ca. No milk production differences were detected. Cows fed CON had an elevated adverse health score (calculated by assigning numerical values to recorded health events) and tended to have an elevated somatic cell count during the fresh period compared with cows fed ND or NDCA. Overall, an acidogenic diet prepartum without or with high Ca improved postpartum Ca status and health. Supplementation of additional Ca to the acidogenic diet had little effect.

Metabolic and blood acid-base responses to prepartum dietary cation-anion difference and calcium content in transition dairy cows

“…Additionally, Amundson et al (2018) demonstrated that feeding a low DCAD diet with high dietary Ca increased the amount of EGTA required to place cows in a state of SCH, suggesting an increased amount of rapidly available Ca in cows fed a low DCAD, high Ca diet. Recently, we (Glosson et al, 2020) reported little effect of high Ca supplementation in a negative DCAD diet on blood Ca concentration or production of Holstein cows, but their reproductive performance including uterine health and fertility was improved by the higher dietary Ca (Ryan et al, 2020). How the blood acid-base balance system and metabolism around parturition respond to a negative DCAD diet with or without supplemental dietary Ca is still unclear.…”

Low potassium diets with different levels of calcium in comparison with different anionic diets fed to prepartum dairy cows: Effects on sorting behaviour, total tract digestibility, energy metabolism, oxidative status and hormonal response

“…In contrast, Glosson et al. (2020) showed that increasing the Ca content from 0.44% to 1.97% by adding limestone did not affect DMI. As sorting behaviour was not altered, differences in palatability between the HCLK and the LCLK diets in palatability seem unlikely, but cannot be excluded.…”

Effect of polyhalite on urine pH, dry matter intake, blood calcium (Ca) concentration and urinary Ca output when fed to pregnant and non-lactating dairy cows

“…Following an approach similar to that of Weiss and Wyatt (2000), we performed an a posteriori power calculation based on the variance in DMI observed in this study and concluded that a sample size of 32 cows per treatment would have been necessary to make the 2.4-kg/d difference statistically different with an 0.80 statistical power at a 0.05 significance level. Compared to other studies (Goff and Koszewski, 2018;Lopera et al, 2018;Glosson et al, 2020), we acknowledge the limited sample size of our study to detect a 2.4-kg/d difference on DMI with an 0.80 statistical power at a 0.05 significance level. In regard to polyhalite, DMI during the prepartum period of cows consuming the NEG diet differed numerically, but not statistically (P = 0.80), by 0.9 kg/d less than DMI of cows consuming the CON diet.…”