A south beef breed was developed, approbated and adopted in Ukraine in 2008. However, the realization of the beef cattle genetic potential is not possible without the organizing of the valuable feeding in accordance with the animals’ physiological requirements in certain periods of the productive cycle.

Estimation of nutrients digestion and identification of indexes of nitrogen, Ca and P exchange in the organism of the south beef breed cows of the Black Sea region type with the different level of energy and protein feeding during the drought period was carried out in the stud farm LTD "Zelenogіrs'ke" in Liubashivky rayon, Odessa oblast’. The research was carried in three groups of cows with 8 animals in each one. The preparatory period lasted for 15 days and the record period lasted for 60 days. During the preparatory period the animals of all groups got the basic ration (BR) from the feeding-stuff of the farm. This stuff was normed according to the A. Kalashnikov’s recommendations given in 2003. In the record period the control group got BR, the second one got BR + 10% of metabolic energy, and the third one got BR + 10% of protein.

The analysis of the received research results showed that the increase of the level of metabolic energy by 10 % in the ration of cows during the drought period contributed to the improvement of digestion of the most nutrients in the feeding-stuff. Thus, the digestion of raw protein increased by 2,22 % (P<0,01), and raw fat increased by 1,68 % in comparison with the indexes of the control group. However, the declination of the raw ash digestion was marked.

Increasing the protein level by 10 % in the ration the digestion of the dry and organic substance increased by 0,47 and
0,67 % respectively. The coefficient of the raw protein digestion increased by 4,51 % (P<0,01), raw fat increased by 5,76 % (P<0,01), and raw cellulose increased by 2,4 % (P<0,05). However, the digestion of free-nitrogenextracts and raw ash reduced.

The increase of the metabolic energy level in the ration of cows in the drought period favoured the growth of nitrogen intake from the feeding-stuff by 6,6 % (P<0,01). Thus, the faecal excretion of nitrogen diminished, however, not substantially. That is why, the availability of nitrogen from the feeding-stuff increased by 3,4 % (P<0,01).

Meanwhile, the urinary recovery of nitrogen grew considerably and were 184,38 g., that is by 5,7 % (P<0,05) higher than the analogical index of the control group. However, the maintenance of nitrogen in the body rose by 9,5 % (P<0,01), and in a calculation on 1 kg of the used dry substance – by 3,6 % (P<0,05).

With the increasing of the protein level in the ration the cows got with the feeding-stuff more nitrogen by 8,5 % (P<0,001). The faecal excretion of nitrogen in the animals of this group diminished by 5,6 %. Accordingly, the availability of nitrogen from the feeding-stuff grew by 6,9 % (P<0,01). The considerable rise of urinary recovery of nitrogen was marked. Thus, the animals of this group lost more nitrogen by 6,8 % (P<0,001) comparatively with the analogues of the control group. However, the maintenance of nitrogen in the body grew by 15,8 % (P<0,001). In the calculation on 1 kg of the used dry substance the cows of the third experienced group retained in the body more nitrogen by 12,3 % (P<0,01).

The increased level of energy in the ration of cows of the second group favoured the growth of calcium consumption with the feeding-stuff by 8,2 %. At the same time, the faecal excretion of calcium enhanced by 1,7 %. Although, the availability of this element from the feeding-stuff of the ration rose by 0,8 %. The urinary recovery of calcium grew by 3,1 % (P<0,05), too. However, the maintenance of calcium in the body rose by 1,5 %, but in a calculation on 1 kg of the used dry substance – went down by 4,4 % in comparison with the analogical indexes of the control group.

With the increasing of the protein level in the ration of cows in the third group their calcium consumption from the feeding-stuff increased by 4,0 % (P<0,001). Although, the fecal excretion of calcium increased by 2,3 %, this availability increased by 1,3 %. The increase of urinary recovery of this element by 3,7 % (P<0,05) is marked. However, the maintenance of calcium in the body enhanced by 5,2 % and in a calculation on 1 kg of the used dry substance – by 2,2 % in comparison with the control group.

The changing of the level of the metabolic energy in a ration influenced on the phosphorus balance in the organism of cows of the second experienced group. Thus, the consumption of phosphorus from the feeding-stuff by the animals of this group grew by 3,8 % (P<0,01). The faecal excretion of phosphorus grew by 2,1 %, that is why its availability increased only by 1,5 %. Despite the increase of the urinary recovery of phosphorus by 3,0 %, the maintenance of this element in the body grew by 5,7 % in accordance with the control group. However, in a calculation on 1 kg of the used dry substance the equal amount of phosphorus in the body of animals of both groups was deposited.

The increased protein level in the ration of animals of the third experienced group affected on their consumption of phosphorus from the feeding-stuff. This index grew by 9,3 % (P<0,001). The increase of the faecal excretion of phosphorus by 8,0 % (P<0,01) was marked. That is why, the availability of this element grew only on 1,2 %. Although, the losses of phosphorus increased by 9,3 % (P<0,01), and its maintenance in the body increased by the same amount. Thus, in a calculation on 1 kg of the used dry substance the animals of this group contained more phosphorus by 5,7 % comparatively with their analogues of the control group.

The increase of the energy and protein feeding level by 10 % in the drought period ration of the south beef breed cows of the Black Sea region type helps the digestion of basic nutrients from the feeding-stuff and causes the rise of the nitrogen, calcium, and phosphorus maintenance in the body.

Key words: feeding, energy, protein, cows, drought period, nitrogen balance, calcium, phosphorus, south beef breed.