Effect of dietary cation-anion difference on performance of lactating dairy cows and stability of milk proteins

Abstract

Casein micelle stability is negatively correlated with milk concentrations of ionic calcium, which may change according to the metabolic and nutritional status of dairy cows. The present study aimed to evaluate the effect of dietary cation-anion difference (DCAD) on concentrations of casein subunits, whey proteins, ionic calcium, and milk heat and ethanol stability. Sixteen Holstein cows were distributed in 4 contemporary 4 × 4 Latin square designs, which consisted of 4 periods of 21 d and 4 treatments according to DCAD: 290, 192, 98, and -71 mEq/kg of dry matter (DM). The milk concentrations of ionic calcium and κ-casein were reduced as DCAD increased, whereas the milk urea nitrogen and β-lactoglobulin concentrations were increased. As a result of these alterations, the milk ethanol stability and milk stability during heating at 140 °C were increased linearly with increasing DCAD [Y = 74.87 (standard error = 0.87) + 0.01174 (standard error = 0.0025) × DCAD (mEq/kg of DM) and Y = 3.95 (standard error = 1.02) + 0.01234 (standard error = 0.0032) × DCAD (mEq/kg of DM), respectively]. In addition, 3.5% fat-corrected milk and fat, lactose, and total milk solids contents were linearly increased by 13.52, 8.78, 2.5, and 2.6%, respectively, according to DCAD increases from -71 to 290 mEq/kg of DM, whereas crude protein and casein content were linearly reduced by 4.83 and 4.49%, respectively. In conclusion, control of metabolic changes in lactating dairy cows to maintain blood acid-base equilibrium plays an important role in keeping milk stable to ethanol and during heat treatments.

Effect of dietary cation–anion difference on ruminal metabolism, total apparent digestibility, blood and renal acid–base regulation in lactating dairy cows

“…Thus, based on results of the present study, increasing DCAD can maintain the blood pH near homeostasis, reduce milk concentrations of divalent cations, and probably contribute to avoiding problems with unstable milk proteins during ethanol test and also industrial heat treatment (Martins et al, 2015).…”

“…The increase in concentration of divalent ions in milk can reduce the negative charges of casein micelles and the electrostatic repulsion forces between them (Barros et al, 1999;Marques et al, 2011;Fisher et al, 2012), which can facilitate the coagulation of milk proteins during the alcohol test performed in dairy farms and dairy plants, as well as during milk thermal treatment (Fisher et al, 2012). In a companion study (Martins et al, 2015), we described that milk ethanol and thermal stability were linearly increased when DCAD increased from −71 to 290 mEq/kg DM, which suggested that the control of metabolic changes in lactating dairy cows to maintain the blood acid-base status in equilibrium play an important role to maintain milk stability to ethanol and during heat treatments, probably due to a lower milk concentration of iCa.…”

“…According to Barros et al (1999), when milk concentrations of iCa is increased, negative charges of casein micelles is reduced, which accelerates micelle interactions and reduces heat stability of milk during industrial processing (Jeurnink and DeKruif, 1995). In a companion paper (Martins et al, 2015), we reported that milk concentration of iCa reduced and milk ethanol and heat stability at 140°C increased according to increase of DCAD. Moreover, it was observed that increased milk yield and fat, lactose and total milk solids contents according to DCAD increases.…”

“…The experimental treatments consisted of four DCAD levels, calculated according to the Na, K, Cl and S concentrations of the dietary ingredients as 290,192,98, and −71 milliequivalent (mEq)/kg of dry matter (DM). The table with ingredients proportion and chemical composition of experimental diets was described in detail in a companion paper (Martins et al, 2015). The DCAD levels were calculated based on Tucker et al (1991) using the formula: mEq/kg of DM = [(% Na in DM/0.023)…”

Subclinical intramammary infection does not affect bovine milk ethanol stability

“…The increase of milk concentrations of iCa may reduce the negative charges of the casein micelles and the strength of electrostatic repulsion between them, which reduces the casein resistance to coagulation during contact with ethanol or milk heat processing (BARROS et al, 1999). Previous studies reported that feed restriction (BARBOSA et al, 2012;STUMPF et al, 2013) and metabolic disorders associated with blood acid-base changes (MARQUES et al, 2011;FAGNANI et al, 2014;MARTINS et al, 2015) of dairy cows could be followed by increased milk concentration of iCa and reduced stability of milk proteins. Other milk characteristics were also associated with a lower stability, such as changes in concentrations of caseins' subunits and β-lactoglobulin, milk urea nitrogen (MUN), temperature of the milk sample during analysis, pH, and concentrations of citrate and phosphate (JEURNINK; KRUIF, 1995;SINGH, 2004;LEWIS, 2011).…”