MAGNESIUM-METABOLISM IN LACTATING GOATS FED ON GRASS DIETS DIFFERING IN MINERAL-CONTENT

A balance experiment was carried out using four young lactating goats in a Latin square design, fed with perennial ryegrass (Lolium perenne) from plots that had received 377 kg K/ha (diet 1); 63 kg K plus 377 kg Na/ha (diet 2); 188 kg K plus 188 kg Na/ha (diet 3) or no fertilizer (control diet 4). The apparent availability of Mg was high in all the grass diets (0-355-0.469); it was significantly depressed (P 0–05) when the intake of K was high (diet 1); but was not significantly different when a high intake of K was accompanied by a high intake of Na (diet 3). There was a significantly lower (P 0.05) apparent availability of Na in diet 4 and a significantly higher (P 0–05) apparent availability of K in diet 3. There were no significant differences in the apparent availability of Ca. The plasma Mg concentration was not significantly affected by any dietary treatment but did decrease temporarily when diets were changed. There were no significant effects on mineral concentrations in the milk. © 1990, Cambridge University Press. All rights reserved.