Objective The aim of this experiment was to study the effects of yeast culture supplementation on serum hormone levels, blood biochemical indexes and body weight growth of lactating foals, and to provide reference for the production and healthy breeding of lactating foals.

Methods Eighteen 3-month-old nursing foals with an average body weight of (106.26 ± 3.00) kg and similar birth dates were selected, half male and half female. The foal is kept together with the mare, who is separated from the mare during the day for 8 hours of tethered milking, during which time the foal is not breastfed, and the remaining 16 hours of foal grazing is shared with the mare. Eighteen lactating foals were randomly divided into 3 groups with 6 in each group (3 males and 3 females), which were control group, experiment group Ⅰ and experiment group Ⅱ, respectively. Under the same feeding and management conditions, the control group was supplemented with basic diet, experiment groupⅠwas supplemented with 20 g/d Piomyces yeast culture, and experiment groupⅡwas supplemented with 30 g/d Piomyces yeast culture, and the feeding experiment lasted for 60 days.

Results (1) After 60 days of the experiment, the growth hormone levels in both experiment group Ⅰ and experiment group Ⅱ were extremely significantly higher than those in the control group, with increases of 60.44% and 63.88% respectively (P < 0.01). The somatostatin levels in the suckling foals of the control group were extremely significantly higher than those in experiment group Ⅰ by 40.09% (P < 0.01). The somatostatin levels in experiment group Ⅱ were significantly higher than those in experiment group Ⅰ by 27.99% (P < 0.05). After 60 days, there was no significant difference in body weight among the foals in all groups (P > 0.05). (2) At 30 days of the experiment, the cannon bone circumference in experiment group Ⅱ was significantly higher than that in the control group, with an increase of 7.75% (P < 0.05).

Conclusion Supplementing yeast cultivates to suckling foals during lactation can significantly increase growth hormone levels and decrease somatostatin levels, with the 30 g/day per foal dose exhibiting a more pronounced effect. Although no significant difference was observed in weight gain, foals supplemented with 30 g/day per foal of yeast cultivates showed a significant increase in cannon bone circumference at 30 days of the trial. In summary, supplementing yeast cultivates is beneficial to the growth of suckling foals during lactation, with a recommended dose of 30 g/day per foal, which helps improve their serum hormone levels and certain body measurement indicators.