May 31, 2020

Interpretive Summary: Feeding narasin to ewes during lactation

Interpretive Summary: Milk yield and composition from ewes fed diets containing narasin and their lambs’ performance

By: Anne Wallace

Probiotic bacteria produce a variety of fermentation byproducts with useful functions in both health and animal science. Some of these byproducts include organic compounds with antimicrobial activity, such as lactic acid, bacteriocins, and ionophores. Narasin is an ionophore produced by the bacteria Streptomyces aureofaciens. Narasin is of particular interest in animal science due to its ability to shift the rumen microbiome in favor of bacteria that produce propionate as a fermentation byproduct. Propionate positively benefits energy production and may potentially increase milk yield. 

Feed efficiency and average daily gain of feedlot lambs have improved with narasin in past studies, but its effects on the milk production of lactating ewes is not well studied. Therefore, the authors of this May 2020 Translational Animal Science paper hypothesized that feeding postpartum ewes the ionophore narasin would increase milk production and subsequently improve the performance of their suckling lambs.

In ewes, dry matter intake (DMI), milk production, milk composition and plasma metabolites were measured. In lambs, only growth rate was measured. Ewes were fed basal feed with either no narasin, or 13 mg narasin per kg of dry matter feed. Results found no differences in ewe DMI. Milk production and feed efficiency were significantly increased in ewes fed narasin. Milk composition of narasin-fed ewes also had increased fat, protein, lactose and total solids. There was no difference in the ADG or body weight of suckling lambs after weaning in either group.

Overall, the results of this study support narasin supplementation as a potential way to increase milk production in lactating ewes. More in-depth studies looking at how narasin impacts the gut microbiota of lactating ewes and further exploration into potential synergistic effects of additional fermentation byproducts on the performance and production of lactating ewes and their suckling lambs is justified.