Zinc methionine hydroxy analogue chelate supplementation at a low level could replace pharmacological level of zinc oxide in nursery pigs

Pharmacological levels of zinc oxide (ZnO) are widely used in the weaning pig diets to promote growth and prevent post-weaning diarrhea. This practice is not environmentally sustainable; therefore, an effective alternative is warranted to be investigated. The objective of this study is to evaluate supplementation of Zn as Zn methionine hydroxy analogue chelate (Zn-MHAC, MINTREX® Zn, Novus International Inc., St. Charles, MO, USA) at NRC (2012) recommended Zn level on growth performance, Ca, P digestibility and gut morphology in nursery pigs in comparison with a pharmacological level of ZnO.

A total of 288 weaning barrows (BW = 5.71 ± 0.81 kg), blocked by initial body weight, were randomly allotted to 1 of 2 dietary treatments, with 36 pens per treatment and 4 pigs per pen. The dietary treatments include: 1) 2000 mg/kg Zn as ZnO during phase 1 (d 1 to 14) and 2 (d 15 to 28), and 100 mg/kg Zn as ZnO during phase 3 (d 29 to 42), 2) 100 mg/kg Zn as Zn-MHAC from phase 1 to 3. Fecal samples were collected via grab sampling from d 25 to 27. Two cm segments of duodenum (10 cm distal to pylorus), mid-jejunum and ileum (5 cm proximal to the end of small intestine) were collected on d 42 for morphometry examination and measurements.

ZnO supplementation significantly (P < 0.05) increased growth performance of nursery pigs during phase 1 compared with Zn-MHAC supplementation, in terms of average daily gain, average daily feed intake and gain to feed ratio. However, pigs fed Zn-MHAC tended to have greater (P = 0.06) gain to feed ratio during phase 2. There were no differences (P > 0.10) between ZnO and Zn-MHAC groups in terms of growth performance during the entire nursery period. Additionally, pigs fed Zn-MHAC had significantly greater standardized total tract digestibility of Ca (59.46% vs. 53.83%; P < 0.01) and P (39.50% vs. 18.17%; P < 0.01) during phase 2 compared with those fed a pharmacological level of ZnO. Furthermore, pigs fed ZnMHAC tended (P = 0.07) to have shorter villus width in ileum on d 42 compared with those fed ZnO.

Results indicated that Zn-MHAC supplementation at 100 mg/kg could replace pharmacological levels of ZnO without affecting growth performance of nursery pig under the conditions of the current study. Nursery piglets supplemented with Zn-MHAC caught up with the positive effect of pharmacological levels of ZnO after phase 1. This could possibly be attributed to improved Ca and P digestibility, as well as enhanced gut morphology

Keywords: Zinc oxide, zinc methionine hydroxy analogue chelate, growth, Ca and P digestibility, gut morphology, nursery pigs