# Improved Growth and Reproductive Performance and Reshaped Gut Microbiota in Jining Grey Goats Through Nubian Crossbreeding

## TL;DR

Crossbreeding Jining Grey goats with Nubian bucks improves growth and litter weight without reducing fertility, likely due to changes in gut bacteria.

## Contribution

This study reveals a microbial link to heterosis effects in crossbred goats, combining growth and reproductive performance analysis.

## Key findings

- Crossbred goats (Nubian × Jining Grey) showed 30% higher birth weight and faster growth than purebreds.
- Litter total birth and weaning weights were higher in crossbred does without affecting lambing rate or kid survival.
- Gut microbiota of crossbreds had a distinct structure with increased Firmicutes-to-Bacteroidota ratio and energy metabolism-related genera.

## Abstract

Jining Grey is a Chinese indigenous goat breed known for its high prolificacy but relatively low growth rate. To improve growth performance while maintaining prolificacy, we crossed Jining Grey does with Nubian bucks and compared purebred and crossbred goats. Crossbred kids were heavier at birth and grew faster from birth to one year of age, while lambing rate, litter size and kid survival remained unchanged. However, total litter birth weight and weaning weight were higher in crossbred does. These findings indicate that shifts in the gut microbiota are associated with variations in growth and reproductive output in crossbred goats, offering a potential microbial link to the heterosis effects.

Crossbreeding indigenous goats with exotic meat breeds is a common strategy to improve production performance, but its combined effects on growth and reproductive traits and the potential contribution of the gut microbiota have not been systematically evaluated in Chinese goat populations. This study used high-prolific Jining Grey (JJ) does mated with Nubian (N) bucks to establish three genetic groups: purebred Jining Grey (JJ), F1 Nubian × Jining Grey (NJ), and backcross offspring (Nubian × (Nubian × Jining Grey); NJJ). Body weight from birth to 12 months and average daily gain were recorded, reproductive traits (lambing rate, litter size, and kid survival) of primiparous and multiparous does were analyzed, and litter total birth weight and weaning weight per lambing were calculated. Fecal samples from JJ and NJJ goats were subjected to 16S rRNA gene sequencing to characterize gut bacterial communities. Body weight differed significantly among the three genetic groups at all ages (p < 0.01). Crossbred kids (NJ and NJJ) were about 30% heavier at birth and showed higher body weight and average daily gain during pre- and post-weaning periods than JJ kids (p < 0.05), representing a consistent growth advantage. In contrast, lambing rate, litter size and kid survival did not differ among genotypes (p > 0.05), whereas litter total birth weight and weaning weight were higher in crossbred than in purebred does (p < 0.05). Alpha-diversity indices were similar between JJ and NJJ goats (p > 0.05), but community structure was significantly distinct (PERMANOVA, p = 0.001), characterized by an increased Firmicutes-to-Bacteroidota ratio and shifts in several energy metabolism-related genera (p < 0.05). In conclusion, introgression of Nubian genetics into Jining Grey goats improves growth performance and litter weight while maintaining high prolificacy; these improvements are accompanied by a restructured gut microbiota that is associated with these growth patterns.