Abstract
Two CYP17 genes, located on different loci and expressing enzymes with significantly different activities, have been identified in the South African Angora goat population. Three unique genotypes (named H e , H u , and H o ), which differed not only in the genes encoding CYP17 , but also in copy number were subsequently identified in the Angora goat. The aim of this study was to evaluate the production and reproduction performance of these three genotypes. Bodyweight, fleece and reproduction data, and blood samples from 466 Angora ewes from three flocks were obtained from the GADI-Biobank. Data had been collected on Flock 1 from 2000 to 2015, Flock 2 from 2000 to 2014 and Flock 3 from 2000 to 2010. Bodyweight data included birth weight, weaning weight, 8-, 12-, and 16-month bodyweight, as well as bodyweight recorded annually for the ewe flock before mating. Fleece data included fleece weight and fibre diameter recorded at the second and third shearings at 12 and 18 months old, respectively. Fleece weight, fibre diameter, style and character were also recorded annually for the ewe flocks during the winter shearing. Individual reproduction records included information on whether the ewe had kidded, whether the ewe had aborted, number of kids born, stillborn kids, kids that died soon after birth, kids reared by a foster mother, kids reared as orphans, number of kids weaned and total weight of kids weaned. Total lifetime reproductive performance of genotyped ewes was calculated for number of kids born, number of kids weaned, and total weight of kids weaned. Blood samples were also collected from 100 sexually active Angora rams from four sources. CYP17 genotyping was carried out using an ARMS-qPCR (amplification refractory mutation system qPCR) assay. Serum testosterone was quantified using high performance liquid chromatography mass spectrometry. The distribution of the ewes across the three CYP17 genotypes was 36.7% H e , 51.5% H u , and 11.8% H o , and was in accordance with the distribution of the Angora veld rams (38.0% H e , 46.4% H u , and 15.6% H o ). In this study, animals of the H u genotype were heavier from weaning age onwards, although this difference in bodyweight was significant only at 8 months old and in the adult ewes. No differences were observed between the H e and H o animals. Adult ewes of the H e genotype (1.35 kg) produced heavier ( P 0.05). No significant differences were recorded in reproductive performance among the genotypes, although the H o ewes had the lowest (1.03 and 0.89) and the H e ewes the highest (1.07 and 0.93) number of kids born and weaned per year respectively. Results on the rams indicated that the CYP17 genotype had no effect on testosterone production by Angora rams. From the results of this study no evidence could be found that selection for any of the three genotypes would adversely affect any growth, mohair production or reproduction function of Angora ewes. A breeding strategy incorporating selection for productive traits and the CYP17 genotype, aimed at increasing the frequency of the ACS+ gene and thus the He genotype in the population, could be followed without having a negative effect on the genetic progress of productive traits. Keywords: Bodyweight, fleece weight, number of kids weaned, testosterone, weight of kids weaned
Highlights
One of the continual problems that face the South African mohair industry is the severe loss of Angora goats during cold spells, owing to the inability of the goats to cope with severe stress (Wentzel et al, 1979; Fourie, 1984; Storbeck et al, 2007; Snyman & Van Heerden, 2011; Snyman et al, 2017)
Genotype had a significant effect on 8-month bodyweight (Table 2), adult bodyweight, adult fleece weight, and style of the fleece (Table 3)
A significant interaction between genotype and flock was observed for adult bodyweight, fleece weight, fibre diameter and the individual reproductive traits
Summary
One of the continual problems that face the South African mohair industry is the severe loss of Angora goats during cold spells, owing to the inability of the goats to cope with severe stress (Wentzel et al, 1979; Fourie, 1984; Storbeck et al, 2007; Snyman & Van Heerden, 2011; Snyman et al, 2017). Sci. vol 47 has shown that the Angora goat is unable to produce sufficient cortisol (the adrenal steroid hormone released in response to physiological stress) in reaction to cold stress (Van Rensburg, 1971; Herselman & Pieterse, 1992; Herselman & Van Loggerenberg, 1995; Engelbrecht et al, 2000; Engelbrecht & Swart, 2000; Storbeck et al, 2008; Storbeck et al, 2009). This deficiency in cortisol production could be attributed to anomalies in the adrenal steroidogenesis of the Angora goat. Depending on CYP17 activity, the adrenal steroid hormone biosynthesis pathway is either directed to the formation of mineralocorticoids and glucocorticoids or to precursors of sex hormones (Gilep et al, 2011)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.