Sex effects on macromineral requirements for growth in Saanen goats: A meta-analysis

Abstract

The aim of this study was to investigate the effects of sex on the net requirements of growth for Ca (NCa_g), P (NP_g), Na (NNa_g), K (NK_g), and Mg (NMg_g) in Saanen goats from 5 to 45 kg BW, with or without consideration of the degree of maturity. A database containing 209 individual records for Saanen goats (69 castrated males, 71 intact males, and 69 females) was generated from 6 comparative slaughter studies. Total amounts of Ca, P, Na, K, and Mg in the body were fitted to logarithmized allometric equations using empty BW (EBW) or degree of maturity (EBW/mature EBW) as regressors. The equations were fitted using a mixed model, where sex was considered a fixed effect and study was considered a random effect. Net requirements were estimated by the first derivative of the logarithmized allometric equations. Then, a Monte Carlo simulation was used to assess the uncertainty of calculated net requirement values. Without considering the degree of maturity, sex did not affect NCa_g, NP_g, and NNa_g (<i>P</i> > 0.10). Conversely, considering the degree of maturity, NCa_g and NP_g of intact males were 5% and 2%, respectively, greater than those of castrated males and females (<i>P</i> < 0.01), and NNa_g of males (castrated and intact) was 6% greater than that of females (<i>P</i> < 0.01). Regardless of approach used, NCa_g and NP_g remained constant, whereas NNa_g decreased by 32% as BW ranged from 5 to 45 kg. Without considering the degree of maturity, NMg_g of castrated and intact males were 8% and 18% greater than that of female goats (<i>P</i> = 0.054), respectively. Hereof NMg_g of castrated and intact males increased by 8% and 15%, respectively, whereas that of females decreased by 8% as BW ranged from 5 to 45 kg. Considering the degree of maturity, NMg_g of castrated and intact males were 7% and 17% greater than that of female goats (<i>P</i> = 0.054), respectively. In this regard, NMg_g of castrated and intact males increased 8% and 16%, respectively, whereas that of females decreased by 7% from 5 to 45 kg BW. Both approaches showed that, regardless of sex (<i>P</i> > 0.10), NK_g decreased by 26% (i.e., without considering the maturity degree) or 27% (i.e., considering the degree of maturity) from 5 to 45 kg BW. Therefore, the consideration of maturity stage highlights differences across sexes in the net macromineral requirements for growth in goats. Elucidation of sex effects on macromineral requirements for growth may be useful for improving the accuracy of recommendations for mineral requirements for dairy goats.