EN
The authors present methods to prevent a negative energy balance taking into consideration the effect of the most commonly applied energy preparations on the level of plasma metabolites, as well as on the productivity and fertility of cows. The first studies indicating the potential application of glucoplastic compounds, particularly synthetic glycerol (GLY), propylene glycol (PG) and propionic compounds in the prevention of the effects of energy deficit after calving, including ketonemia, were published approx. 50 years ago. Monopropylene glycol (1,2-propandiol) is particularly useful in the prevention of problems resulting simultaneously both from acidosis and ketosis. The administration of 500 ml PG from day 7 after calving did not have a significant effect on the dynamics of ovarian follicles, the mean number of days to the emergence of the first cohort of ovarian follicles, dominant follicles or the duration of the follicular wave. Due to supplementation of PG between day 7 and day 42 after calving an improvement of conception rate from 33 to 57% was obtained, the date of the first ovulation post partum was accelerated from day 44.5 to day 32.3 and the first luteal phase after calving was extended from 7.3 to 13.1 days. Currently a new trend may be observed in replacing synthetic PG by qualitatively more universal and effective substances contained in plants. The best known substance of this kind is 1,2,3-propanetriol, i.e. glycerol, obtained during biofuel production. Fats are most typically fed between week 4 and week 12 of lactation. In cows receiving an increased fat content with their feed no deterioration of yields was observed, or uptake of dry matter and starch for the production of blastocysts, found in cows receiving a diet poor in fat. Fatty acids, irrespective of their value, may constitute a threat for the ruminal environment due to the modification of the flora colonising it and metabolic indexes. An increased amount of unsaturated acids in the feed ration results in their enhanced availability in the duodenum. Cows receiving an addition of fat showed more evident estrus symptoms. Fat had a positive effect on hormone metabolism thanks to improved ovarian function. A higher probability of embryo implantation and their low mortality were also demonstrated. A diet rich in calcium salts of long-chain fatty acids (Ca-LCFA) fed in the preparturition period considerably reduced the frequency of postpartum complications, such as placenta retention, metritis as well as mastitis. Similarly, an addition of fat had an advantageous effect on the stimulation of ovaries as well as the development and diameter of corpora lutea. When feeding grain with an addition of Ca-LCFA after calving an increase was observed in the number of medium-sized and large follicles during the first 25 days after parturition and during the synchronized estrus cycle. Supplementation of the feed ration with calcium salts of fatty acids had an advantageous effect on the function of corpora lutea, conception rate and the length of pregnancy interval. Administration of wet crushed corn grain instead of dry grain results in enhanced ruminal fermentation. It also causes a more balanced energy and protein metabolism, a better state of health, a higher daily milk production, a higher protein concentration in milk as well as a better reproduction performance replacement of triticale with corn in the transition period as well as during lactation; it improved the conception rate, reduced the insemination index, and it also reduced calving interval. A considerable number of publications concerning the advantageous effect of an addition of corn on parameters of the energy metabolism, metabolic indexes, production traits and the milk composition does not change the fact that the body of data concerning reproduction in cows fed in this way is insufficient.