PSIII-14 - the effects of co-twin sex on fitness traits in young meat goat does

Abstract: This study examined if co-twin status influenced reproductive and health traits in meat goat does. Herd records of does identified as twin-born between 2003-2022 in the Tennessee State University Research herd were evaluated for fitness traits as two and three-year-olds. Twin category (TC) was classified as female co-twin (n=188; FT) or male co-twin (n=194; MT). Study does were the crossbred or purebred daughters of Kiko, Myotonic, Spanish, and South African (Boer and Savanna) sire breeds. Traits analyzed were birth weight (BWT), weaning weight ratio (WWR), doe breeding body weight (DWT), fecal egg count (FEC), packed cell volume (PCV), kidding rate (KR), weaning rate (WR), and survival rate (SR) using MIXED and GLIMMIX models of SAS. Birth weight revealed doe sire breed (p < 0.0001) and twin category (p = 0.002) were significant. Study does born with a FT were heavier (2.68 ± 0.06 vs. 2.53 ± 0.06 kg) than does born with MT. South African breeds were heavier (p < 0.0001) than all three breeds, while the Myotonic was lighter (p < 0.0001) than all three breeds. Weaning weight ratio revealed the interaction of TC with doe sire breed (p = 0.05) was significant. The interaction showed that FT Spanish does had a higher (p = 0.01) WWR than MT Spanish does (103.90 ± 2.86 vs. 91.69 ± 2.94). Sire breed (p < 0.0001) and doe age (p < 0.0001) were significant for doe breeding weights but not twin category (p = 0.47). Twin category was significant (p = 0.01) for breeding FEC; does with FT had lower counts (2.53 ± 0.12 vs 2.34 ± 0.12 eggs/g) than does with a MT. Doe age and TC were not significant for breeding PCV while sire breed (p = 0.01) was significant. Doe age, litter size born, and TC were not significant for kidding FEC and PCV. Doe sire breed was significant (p = 0.003) for kidding FEC. The interaction of TC and litter size weaned was significant for weaning FEC (p = 0.01) and weaning PCV (p = 0.04). The nature of the interaction was within TC class for litter size differences. Doe age (p = 0.008) and sire breed (p < 0.0001) were significant for weaning FEC whereas TC was not significant (p = 0.47). Sire breed (p = 0.86) and TC (p = 0.71) were not significant for SR. Sire breed (p < 0.0001) was significant for KR and WR but not TC (p = 0.29 and p = 0.13). Based on the findings of this study, sex of co-twin had limited influence for the traits tested. Sire breed and doe age had more impact on the traits tested.