| Summary: | The effects of the lactation period, breed, and feed on amino acids profile of mare’s milk were investigated. The feed contained two major essential amino acids (EAAs) leucine (7.31 – 10.3 g.kg-1) and arginine (6.37 – 9.59 g.kg-1); it also included minor EAAs methionine (2.11 – 3.05 g.kg-1) and histidine (2.48 – 3.60 g.kg-1). Glu+Gln, Asp+Asn, and proline, major nonessential amino acids (NEAAs), constituted approximately 60% of total NEAAs (TNEAAs). The ratio of total EAAs to NEAAs ranged from 1:1.2 to 1:1.4. Amino acids (AA) content throughout all milk samples varied due to mare’s different conditions and lactation days. Except for the 1P milk sample, total AA content in the 2 – 8Ps specimens caused by differences in breed oscillated from the 2nd to 28th day of lactation within the following limits: 21.9 – 54.6 g.kg-1, 33.6 – 70.7 g.kg-1, 38.1 – 71.2 g.kg-1, 29.46 – 74.2 g.kg-1, 52.2 – 87.1 g.kg-1, 37.9 – 70.3 g.kg-1 and 26.4 – 64.5 g.kg-1, respectively. In relation to TEAAs in milk, the highest EAAs levels were reached in arginine, leucine and lysine ranging between 2.41 – 4.35 g.kg-1, 3.36 – 5.59 g.kg-1 and 2.72 – 4.80 g.kg-1, respectively, while the lowest AAs amounts were indicated in histidine and methionine, 0.91 – 1.58 g.kg-1 and 1.23 – 2.04 g.kg-1 respectively. Total NEAAs content was slightly higher than that of EAAs; the TNEAAs to TEAAs ratio was 1:0.9 proximately. Glu+Gln, Asp+Asn and proline were determined as major NEAAs of milk ranging between, 6.77 – 11.0 g.kg-1, 3.21 – 5.60 g.kg-1 and 1.25 – 2.18 g.kg-1, respectively; levels of NEAAs such as cysteine and glycine oscillated between 0.89 – 1.52 g.kg-1 and 0.64 – 1.15 g.kg-1, respectively. The average TAAs contents caused by breed differences were 62.8 g.kg-1, 42.8 g.kg-1, 44.7 g.kg-1 and 44.8 g.kg-1, respectively, on the 2nd, 5th, 10th, and 28th lactation days.
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