Fig 1.
PRISMA flow chart showing exclusion and inclusion criteria for selection of the peer-reviewed articles used to derive the phosphorus and calcium requirements system for lactating dairy cows.
A first systematic review was performed in November 6, 2017 (53 articles). The second systematic review was done in March 13, 2024 using the same terms, but included published ≥ 2018 year (n = 4 articles). A total of 57 peer-reviewed articles were included to create our complete dataset [21].
Table 1.
Descriptive statistics of the complete dataset use to develop the new phosphorus and calcium requirement model for lactating dairy cows.
Table 2.
Nonlinear mixed regression analysis of sum of total fecal and urinary excretions of phosphorous (PFU) or calcium (CaFU) and mineral intake to obtain the net requirements for maintenance of lactating dairy cows.
Fig 2.
Relationship between the sum of daily phosphorus (P) or calcium (Ca) total fecal and urinary excretion and mineral intake.
The dotted lines are the predicted values from Eqs 3 and 4 (Table 2). n = 130 treatment means reported from 39 P balance trials, and n = 70 treatment means reported from 23 trials Ca balance trials.
Fig 3.
Plot of observed versus predicted total phosphorus (PFU) or calcium (CaFU) fecal and urinary excretion (prediction equations are in Table 2).
Predicted values were derived from the 5-fold cross-validation procedure. The five folds were previously created by study grouping to guarantee independence between observed and predicted values. n = 130 treatment means reported from 39 P balance trials, and n = 70 treatment means reported from 23 trials Ca balance trials.
Fig 4.
Box plot of the estimated diet metabolizable coefficient of phosphorus and calcium for lactating dairy cows from Eq 2.
Estimated metabolizable coefficient for phosphorus: mean ± standard error (SE) = 0.69±0.01 and n = 157 treatment means. Estimated metabolizable coefficient for calcium: mean ± SE = 0.65±0.02 and n = 81 treatment means. Final dataset, codes and outputs are described in S2.1 and S2.2 in S2 File.
Table 3.
Effects of the diet composition on estimated diet metabolizable coefficient of phosphorous (MC-P) and calcium (MC-Ca) in lactating dairy cows.
Fig 5.
Box plot of milk phosphorus (P) and calcium (Ca) concentration for Holstein and Jersey cows (complete dataset, Table 1).
Milk P mean (95% confidence interval): 0.90 (0.89, 0.92) g/kg milk (n = 135 treatment means) for Holstein; and 1.00 (0.96, 1.04) g/kg milk for Jersey (n = 41). Milk Ca mean (95% confidence interval): 1.18 (1.12, 1.23) g/kg milk (n = 56 treatment means) for Holstein; and 1.38 (1.28, 1.47) g/kg milk for Jersey (n = 47).
Table 4.
Summary of proposed factorial system of phosphorus and calcium requirements for maintenance and lactation of dairy cows.
Fig 6.
Estimated net and dietary requirements of phosphorus and calcium for lactating dairy cows from our proposed system (Table 4), NASEM (2021, [12]) and NRC (2001, [19]) models.
NASEM (2021) P requirement: maintenance (g P /d) = 1 × dry matter intake (DMI; kg/d) + 0.0006 × body weight (BW; kg); lactation (g P/d) = 0.90 × milk yield (kg/d); overall absorption coefficient (default) = 0.72; estimated DMI for multiparous cows with 60 days in milk, three points of body condition score, and milk energy of 0.73 Mcal/kg. NASEM (2021) Ca requirement: maintenance (g Ca/d) = 0.9 × DMI (kg/d); lactation (g P/d) = 1.03 × milk yield (kg/d); absorption coefficient = 0.60 for concentrate and 0.40 for forage; assuming forage in diet of 800, 600, 500, 450 and 400 g/dry matter (DM) for 10, 20, 30, 40 and 50 kg/d of milk yield, respectively. NRC (2001) P requirement: maintenance (g P /d) = 1 × DMI (kg/d) + 0.0002 × BW (kg); lactation (g P/d) = 0.90 × milk yield (kg/d); absorption coefficient = 0.70 for concentrate and 0.64 for forage. NRC (2001) Ca requirement: maintenance (g Ca/d) = 0.031 × BW (kg); lactation (g Ca/d) = 1.22 × milk yield (kg/d); absorption coefficient = 0.60 for concentrate and 0.30 for forage; assuming forage in diet of 800, 600, 500, 450 and 400 g/DM for 10, 20, 30, 40 and 50 kg/d of milk yield, respectively.