Effect of feeding mixed microbial culture fortified with trace minerals on ruminal fermentation, nutrient digestibility, nitrogen and trace mineral balance in Sheep

Feeding animals with microbials directly improves ruminal acidosis prevention, gut microbial balance, feed intake, weight gain, and feed efficiency in ruminants [1–3]. For instance, feeding with yeast culture increased feed intake in lactating cows [4, 5] and Hereford steers [6, 7], resulting in better animal performance. The use of microorganisms in animal diets has been shown to improve trace mineral balance. Yeast culture supplementation improved the retention of zinc and iron in lambs [7] and copper and iron in growing ruminants [1]. Feeding with mixed microbial (Bacillus and Saccharomyces) culture was shown to improve bioavailability of trace minerals (zinc, copper, and iron) to beef steers [8].

Trace mineral deficiency affects almost all physiological processes like growth, reproduction, immunity, milk production and other functions of animals [9]. Dietary trace minerals such as zinc and copper are essential components of enzymes needed for growth and lactation [10]. Fat metabolism seems to be associated with zinc. The glucose incorporation into fatty acids is greatly reduced in zinc-deficient animals [11]. According to previous studies, addition of zinc to cattle diets improves the growth of animals and carcass characteristics [12, 13].

Copper deficiency is an important problem in ruminants in many areas of the world. Copper deficiency frequently occurs because copper antagonists that reduce the bioavailability of copper, such as molybdenum, sulfur, and iron, are often high in ruminant diets [14]. Relatively low dietary concentrations of sulfur and molybdenum can increase copper requirement by 2 to 3-fold [10]. Copper supplementation affected lipid metabolism by reducing cholesterol concentrations in the longissimus muscle of Brangus bulls in the study of Netto et al. [15]. Indoor confinement systems of cattle lowered zinc and copper intake from pastures and soils. Zinc and copper supplementation of cattle diets becomes increasingly important with regard to the greater use of high concentrate feeds [11]. In practice, feed manufacturers use higher concentration of zinc and copper than those specified for ruminants to achieve the maximum performance [16]. Zinc and copper supplementation in human food is especially important for pregnant women, and people consuming less animal products rich in zinc and copper [11]. As found in our previous research, feeding a combination of mixed microbial culture and clay minerals to beef steers increased the concentrations of zinc and copper in the longissimus muscle [8]. Feeding with trace minerals-fortified mixed microbial culture (TMC)-supplemented diet increased concentrations of certain trace minerals in the longissimus muscle of Hanwoo steers [17]. Thus, in the current research, we hypothesized that supplementing a mixed microbial culture with trace minerals (zinc and copper) will positively affect the ruminant performance and still increase bioavailability or retention of zinc and copper when the dietary zinc and copper contents increase from 1.5-fold to 2.5-fold of dietary requirement.

Accordingly, the aim of the study was to evaluate the effects of TMC on nutrient digestibility, ruminal fermentation, blood electrolytes, nitrogen (N) balance, and trace mineral balance of sheep.