The effect of dietary crude protein and phosphorus on grass-fed dairy cow production, nutrient status, and milk heat stability

Abstract

Dietary crude protein (CP) and phosphorus (P) have the potential to alter dairy cow production, nutrient status, and milk heat stability, specifically in early lactation. This study examined the effect of supplementary concentrates with different CP and P concentrations on blood N and P status and on milk yield, composition, and heat stability. The concentrates [4kg of dry matter (DM) concentrate per cow daily] were fed to grazing dairy cows (13kg DM grass) during early lactation. Forty-eight spring-calving dairy cows were allocated to 4 treatments: high CP, high P (HPrHP; 302g/kg DM CP, 6.8g/kg DM P), medium CP, high P (MPrHP; 202g/kg DM CP, 4.7g/kg DM P), low CP, high P (LPrHP; 101g/kg DM CP, 5.1g/kg DM P), and low CP, low P (LPrLP; 101g/kg DM CP, 0.058g/kg DM P), for 8wk. Levels of N excretion were significantly higher in animals fed the HPrHP and MPrHP concentrates; P excretion was significantly lower in animals fed the LPrLP concentrate. Reducing the level of P in the diet (LPrLP concentrate) resulted in a significantly lower blood P concentration, whereas milk yield and composition (fat and protein) were not affected by either CP or P in the diet. The effect of the interaction between treatment and time on milk urea N was significant, reflecting the positive correlation between dietary CP and milk nonprotein N. Increasing supplementary CP and P (HPrHP) in the diet resulted in significantly lower milk heat stability at pH 6.8. The findings show that increasing dietary CP caused a decrease in milk heat stability, which reduced the suitability of milk for processing. The study also found that increasing dietary CP increased milk urea N and milk nonprotein N. Increasing dietary P increased fecal P excretion. These are important considerations for milk processors and producers for control of milk processing and environmental parameters.

Feed additives containing sequestrant clay minerals and inactivated yeast reduce aflatoxin excretion in milk of dairy cows

“…We also found an interactive effect of treatment and time on MUN (P = 0.03; Table 3), apparently due to a difference between PC versus TN and UP (P = 0.06). Concentrations of MUN are typically related to levels of dietary CP (Reid et al, 2015) and reflect protein metabolism but 3 other studies on AF and mycotoxin binders did not find any effect on MUN (Maki et al, 2016;Sulzberger et al, 2017;Weatherly et al, 2018).…”

Effect of calcium, citrate and urea on the stability of ultra-high temperature treated milk: A full factorial designed study

“…As seen in Figures 2 and 3, the sensory attributes and, as in Figure 4, the stability during storage, were not improved compared to the reference UHT milk. Milk urea is known to vary with feed, and in a study by Reid et al [15], cows with high crude protein intake had a significantly higher milk urea concentration compared to intake of a low protein feed. However no difference in heat coagulation time was reported [15].…”

Spectral indicators of forage quality in West Africa’s tropical savannas

“…Pullanagari et al, 2012;Thulin et al, 2012). Phosphorus is an important macro element in animal nutrition (Reid et al, 2015) and has therefore been investigated by several authors (e.g. Albayrak et al, 2011;Kawamura et al, 2009).…”