Effect of dietary crude proteins on the reproductive function in the postpartum dairy cow

The study was conducted on 216 dairy cows. Samples of feeds distributed to cows were collected monthly for the purpose of determining their content in dry matter, energy, crude proteins and mineral matter. Milk samples were collected weekly for every cow from newly calved cows until confirmation of pregnancy by rectal palpation at least 2 months after artificial insemination. These samples were used for progesterone assays in skimmed milk, in order to assess the interval between calving and return to ovarian activity [C-ROA], calving and first insemination [C-I1], calving and conception [C-C] and number of inseminations per conception (nI/C). Results have shown a significant negative correlation between the duration of [C-ROA] and [C-C] intervals and the dietary content in crude proteins (r = -0.720, p < 0.05 and r = -0.914, p < 0.01 respectively).