Table 2.
Use of REE-based feed additives in livestock: observed effects
| Target species/strains | Tested REEs | REE concentration (mg/kg) | Observed effects | References |
|---|---|---|---|---|
| 1. Poultry | ||||
| Ross broiler chicks | REE citrate or REE chloride | 70 | Increased gain in body weight and feed conversion ratio | He et al. (2010) |
| Arbor Acre broiler chicks | LaCl3 or La2O3 | 100–400 | No significant difference in the final live weight, daily weight gain and feed conversion ratio | Igbasan and Adebayo (2012) |
| Ross 308 1d-old broilers | REE-enriched yeast | 500–1500 | No significant influence on growth performance, but improved nutrient digestibility and meat quality | Cai et al. (2015) |
| Lohman LSL laying hens | La2O3 | 100–400 | Significantly increased egg production; no effect on egg weight; decreased MDA and TBARS | Durmuş and Bölükbaşı (2015) |
| Lohman LSL laying hens | CeO2 | 100–400 | Increased egg production, feed conversion ratio and egg shelf life; decreased SOD, MDA and TBARS | Bölükbaşı et al. (2016) |
| ISA brown laying hens | REE-enriched yeast | 500–1000 | Significantly increased egg production and coefficient of apparent digestibility | Cai et al. (2016) |
| Japanese quails | REE citrate | 50–200 | Improved growth and efficiency of protein and energy utilization | Eleraky and Rambeck (2011) |
| 2. Pigs | ||||
| Piglets | La2O3 or REE mixture | 300 | Gain in body weight increase and feed conversion ratio | He and Rambeck (2000) and He et al. (2001) |
| (Landrace × Yorkshire) × Duroc finishing pigs | REE-enriched yeast | 500–1500 | Improved growth performance, digestibility, blood lymphocyte counts, and fecal Lactobacillus counts | Cai et al. (2018) |
| Piglets | REE mixture | 200 | Growth performance of REE-citrate and control fed piglets did not differ significantly | Kraatz et al. (2006) |
| Sows and piglets | REE mixture | 200 | Improved antioxidant effects and immunity of sows and piglets | Xiong et al. (2019) |
| 3. Ruminants | ||||
| West African dwarf sheep | La2O3 | 100–300 | Better daily weight gain and total weight gain; no significant effects on serum and hematological endpoints, except for significant WBC increase | Adu et al. (2006) |
| German Holstein bulls | REE citrate | 100–300 | Decreased weight gain; no increase in nutrient digestibility | Schwabe et al. (2011) |
| Ruminally cannulated Simmental steers | LaCl3 | 450–1800 | Improved rumen fermentation and feed digestion; simulated digestive microorganisms or enzymes | Liu et al. (2008) |
| Ruminally cannulated Simmental steers | CeCl3 | 80–240 | Increased the digestibility of neutral detergent fibre, decreased molar ratio of rumen acetate to propionate | Lin et al. (2015) |