Growth curve and serum calcium and magnesium concentrations in duck breeders (Anas boschas) from hatching to the prelaying period reared under subtropical conditions

Optimizing duck production requires understanding growth variability and monitoring serum calcium and magnesium levelsas health indicators. This study aimed to analyze the growth curve, mortality, and serum calcium (Ca) and magnesium (Mg) levels in White Mallard ducks from hatching to the prelaying period in subtropical conditions. A total of 1100 females and 270 males were raised for 146 days. At hatch, day 6 (D6), D13, D23, D34, D50, D64, D80, D94, D111, and D146, ducks were weighed separately to assess body weight (BW). Blood samples were collected at hatch, D50, D94, and D146 to determine serum calcium and magnesium levels. The influence of age, sex, and their interactions on body weight, growth rate, calcium, and magnesium concentrations was tested, and the growth curves were fitted with the Gompertz nonlinear regression model. There was an interaction between sex and age for all evaluated traits (p < 0.05). Males and females exhibited the same BW up to D64, when males started to become heavier. The growth patterns differed between males and females, with males exhibiting a higher theoretical mature body weight (3.62 kg vs. 3.11 kg) and a later age at the inflection point (29.68 days vs. 26.98 days) than females. The relative growth rate for both sexes peaked up to D23 and then decreased gradually, while absolute growth rates peaked between 13 and 23 days for females and at multiple intervals (13–23 days, 34–50 days, and 50–64 days) for males. Males also had a higher mortality rate compared to females (18.40% vs. 7.78%). At D94, females showed lower serum calcium levels than males, and at D146, lower serum magnesium levels were observed in females. Males and females displayed distinct growth patterns, with males achieving a higher body weight and a later age at the inflection point. Females had lower serum Ca and Mg levels.