Lactation in the Horse: The Mineral Composition of iVIare IVIillc

Changes in the mineral composition of mare milk during lactation were studied. Milk samples were obtained from five Thoroughbred mares 0"«^« thr• times weekly from the first to the eighth week of lactation and from two of the mar^ for an additional 8 wk. Samples averaging 500 mL were obtained after oxytoc.n was administered to the mares. Each sample was analyzed for total sohds, ash ca ciuna isphorus, magnesium, sodium, potassium, copper and zinc. The concentration of all constituents except sodium and potassium decreased throughout lactation. The rates of decline of ash, calcium, phosphorus and magnesium concentration were similar, but the rates of decline of the other elements differed. Thus, *« mm-^^^^^^^^ position of mare milk should be described in terms of the stage of lactation of the mat "he total solids and ash content of mare milk were 12 and 0.61% respectively at the end of the first week of lactation, 10.5 and 0.45% at 4 wk, 10 and 0.38% at 8 wk and 10.2 and 0.32% at 16 wk. The calcium, phosphorus and magnesium concentrations at the end of the same periods were 1345, 943 and 118 ^g/g o milk at 1 wk; 1070, 659 and 86 at 4 wk; 831, 574 and 58 at 8 wk and 700 540 and f/g'S f ^"'1^ at 16 wk. Cooper and zinc concentrations were 0.85 and 3.1, 0.55 and 2 2, 0.29 and 1.9 and 0.28 and 1.8 ,.g/g of milk at 1, 4, 8 and 16 wk, respectively J. Nutr. Ub: 2142-2147, 1986. INDEXING