Utilization of monensin in protein-energy licks by lactating ewes on sour winter veld; (a) Preweaning.

The influence of monensin, at a level of 0,36 mg/kg body mass, to ewes in high and low energy licks (HEL and LEL) and in creep feed for lambs was investigated during the 1979 to 1981 winter seasons. The average daily intake of lick (P ≤:0,01; 206 vs 289 g) and creep feed (P ≤ 0,05; 170 vs 320 g) was lower with monensin than without monensin. Monensin had no significant effect on the DM digestibility (56 ± 2,4%). Ewes on the LEL suffered a bigger (P ≤ 0,01) mass loss per day (133 g) than on the HEL (112 g). Monensin in the lick also resulted in a bigger (P ≤5 0,01) mass loss (145 g) than lick without monensin (100 g). The efficacy of monensin in the lick in maintaining the ewe's body mass, was 47 and 53% lower for the HEL and LEL respectively. The ADG of lambs on creep feed plus monensin (150 g) was lower (P ≤ 0,01) than without (178 g). The efficacy of preweaning creep feed utilization was, however, 37% better with monensin as 1,13 kg creep feed plus monensin was needed/kg mass gain vs. 1,80 kg creep feed without. The energy content of the lick did not affect the wool yield significantly (2,38 ± 0,05 g/100 cm² midrib samples). Monensin in the lick resulted in a lower (P ≤ 0,01) wool yield per ewe (2,26 g) per 100 cm² than without monensin (2,51 g).