EFFECTS OF MINERAL SUBSTANCES WITH A BUFFERING EFFECT ON MILK PRODUCTION AND MILK COMPOSITION IN HEAT STRESS CONDITIONS

This paper presents the results of investigations on the effects of a mineral mixture with a buffering effect, (bentonite, zeolite, magnesium oxide and sodium bicarbonate), on the quantity and composition of milk, pH value of cow's rumen contents, number and motility of microorganisms.The study was conducted from June to November on two groups of cows: the control -C (129) and experimental -E (119).The investigated mineral mixture was included in the complete feed mixture (1%).The milk yield during the hottest summer months (June -August) in the group E was higher by 1.99 kg or 8.16% (p<0.05).During the period from September to November the milk yield in this group was also higher, but insufficiently to make the difference (0.38 kg or 1.53%) between the C and E groups (p>0.05).The yield of milk was higher in the group E by 1.19 kg or 4.85% (p<0.05) for the duration of the experiment from June to November.The differences in the content and yield of milk fat and protein, (% and kg) were insignificantly higher for the group E during both investigation periods.The pH value of the rumen content was higher in the group E and was within the optimal physiological limits.Before the morning meal the values for the groups C and E were 6.25 and 6.79 (p>0.05),respectively.After the morning meal the corresponding rumen pH values were 6.01 and 6.92 (p<0.05).The number and motility of the infusoria present in the rumen of the group E cows was increased.The studied mineral mixture has a positive effect on the pH stability and development of the microorganisms present in the rumen under conditions of heat stress.This contributes to the arousal of favorite conditions for food digestion and utilization and hence to higher milk production and increased fat and protein content.