Ducháček J., Stádník L., Ptáček M., Beran J., Okrouhlá M., Čítek J., Stupka R. (2014): Effect of cow energy status on the hypercholesterolaemic fatty acid proportion in raw milk. Czech J. Food Sci., 32: 273-279.We evaluated the proportion of fatty acid groups, with an emphasis on hypercholesterolaemic fatty acids, in the milk of 25 Holstein cows during the 1 st period of lactation in relation to their negative energy balance (NEB). Sampling of each cow's milk started on the 7 th day after calving. Milk samples (n = 425) were collected at 7-day periods during the first 17 weeks of lactation. The proportion (%) of saturated (SFA), hypercholesterolaemic (HCFA), volatile (VFA), unsaturated (UFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids in the milk fat was determined. Body condition score and fat to protein ratio in milk were applied for precise determination of the NEB breakpoint during the observed period. The effects of parity, NEB, regression on lactation week and fat to protein ratio were evaluated using SAS 9.3. Milk contained a lower proportion of SFA as well as equally higher UFA (± 2.13%; P < 0.01) during the NEB period. The overcoming of NEB caused an increase in SFA, however, and simultaneously a significant decline in total HCFA (-1.86%; P < 0.01) as well as main MUFA (-1.81%, P < 0.05). The results document the necessity of increasing Holstein cow robustness to meet the production conditions in dairy farms in relation to the requirement of higher nutrient quality as well as the potential health benefits of cow's raw milk for consumers.

No abstract

No abstract

The aim of the present study was to optimize the conventional method of sperm freezing in liquid nitrogen (LN₂) vapour for successful cryopreservation of Wallachian ram sperm, the genetic resources of the Czech Republic. Sperm in straws were frozen using the conventional freezing method via a static exposure of sperm doses to LN₂ vapour, or by four different modified freezing methods. Under modified freezing, straws were frozen by a discontinuous, time-dependent decremental change in the distance between the straws and the surface of LN₂. The viability of sperm was evaluated by flow cytometry after sperm equilibration, and immediately after thawing. Besides the observed inter-sire and daily variation, the obtained results suggest the methodological weakness of the conventional freezing method via the static exposure of sperm doses to LN₂ vapour. With the use of the optimized freezing procedure, all parameters of thawed sperm were significantly (P &lt; 0.05) improved in comparison with the conventional method: percentage of thawed sperm viability increased up to 48.3%, percentage of sperm with plasma membrane damage after thawing decreased to 6.58%, percentage of sperm with acrosome damage decreased to 24.4%, and percentage of sperm with deteriorated mitochondrial activity decreased to 6.28%. In conclusion, our results suggest that an optimized freezing procedure should be routinely used instead of the conventional method to cryopreserve Wallachian ram sperm.

The aim of this work was to analyze the growth abilities of bull and heifer calves (n = 190) of the Charolais breed calved in one herd from 2006 to 2011. The evaluation was carried out during the period of calf raising, focusing to the eff ects of sex, parity and the mating method on live birth weight (BLW) and the live weight at 120 (LW120), 210 (LW210) and 365 (LW365) days of life, as well as the average daily weight gain reached by the age of 120 (G120), 210 (G210), and 365 (G365) days. Statistical analysis was carried out with the use of the SAS 9.3 program. The eff ect of sex on the live weight and average daily weight gain was statistically signifi cant on the level of P < 0.01 always in favour of the bull calves (BLW +3.05 kg, LW120 +29.35 kg, LW210 +36.98 kg, and LW365 +117.23 kg). The lowest live birth weight was detected in the calves of primiparous cows (BLW = 45.46 kg; P < 0.01). The higher parity, the higher live birth weight was determined, with maximum values in cows from the fourth calving. The trends were similar in live weight at 120, 210 and 365 days of age, when signifi cance level was P < 0.05. The parity eff ect on the average daily weight gain (G120, G210 a G365) was statistically insignifi cant (P > 0.05). The eff ect of embryo transfer (ET) and other commonly used reproduction methods (insemination and natural mating, AI/PP) was evaluated as well as. The calves born a er embryo transfer showed a signifi cantly (P < 0.01) higher the live birth weight as well as weight at diff erent ages (BLW +5.85 kg, LW120 +18.15 kg, LW210 +22.94 kg and LW365 +35.43 kg), and G120 only (+100 g×day −1 ; P < 0.05). These results pointed the suitability of using the biotechnological reproduction methods, especially in relation to the total weight of the reared and fattened animals.