Effect mineral mixture with a buffering properties on production and quality milk of cows in heat stress conditions

Abstract

This paper presents the results of investigations on the effects of a mineral mixture with a buffering properties, 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 cows; the control-C (129) and experimental-E (119). The cows were in linked system of keeping. Groups were formed according to 'couple' system (two cows with similar characteristics) after 7-10 days calving and alloted to one of two stables. The given meals were identical with the difference that in the complete feed mixture in group E a mineral mixture with buffering properties was added in the quantity of 1%. The mixture was produced at the Institute for Technology of Nuclear and Other Mineral Raw Materials, Belgrade, Serbia. The mixture composition is based on natural bentonite, natural zeolite, magnesium oxide and sodium bicarbonate, The milk yield during the hottest summer months (June - August) in group E was higher by 1.99 kg or 8.16% (p lt 0.05). During the period (September - November) the milk yield in this group was also higher, but insufficiently to make the difference (0.38kg or 1.53%) between the C and E group (p>0.05). The differences in the content and yield of milk fat and protein, (% and kg) were insignificantly higher for group E during both investigation periods. The pH value of the rumen content was higher in group E and was within the optimal physiological limits. Before the morning meal the values for group K and E were 6.25 ; 6.79 (p>0.05), respectively. After the morning meal the corresponding rumen pH values were 6.01 ; 6.92 (p lt 0.05).The number and motility of the infusoria present in the rumen of group E cows was increased. That the studied mineral mixture with buffering properties 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.