Abstract
There is a growing interest in the influence of vitamin D on ovine non-skeletal health. The aim of this study was to explore the relationship between pre-mating vitamin D status, as assessed by serum concentrations of 25-Hydroxyvitamin D [25(OH)D; comprising D2 and D3] and subsequent reproductive performance of genetically unimproved Scottish Blackface (UBF), genetically improved Scottish Blackface (IBF) and Lleyn ewes kept under Scottish hill conditions. 25-Hydroxyvitamin D2 (25(OH)D2) and 25-Hydroxyvitamin D3 (25(OH)D3) concentrations were determined in serum samples harvested in November from ewes grazed outdoors. There were no significant differences in 25(OH)D2concentrations amongst the 3 genotypes. Lleyn ewes had significantly higher 25(OH)D3 and 25(OH)D concentrations than both Scottish Blackface ewe genotypes, whereas these vitamin D parameters did not differ significantly between the UBF and IBF ewes. Concentrations of 25(OH)D3 and 25(OH)D were positively associated with subsequent birth weights of singleton and of twin lamb litters. No significant associations between vitamin D status and number of lambs born or weaned per ewe were found. This study demonstrates that concentrations of cutaneously-derived 25(OH)D3, but not of orally consumed 25(OH)D2, differed between breeds. The positive association between ewe vitamin D status and offspring birth weight highlights the need for further investigations.
Highlights
Blackface (IBF) and Lleyn ewes kept under Scottish hill conditions. 25-Hydroxyvitamin D2 (25(OH)D2) and 25-Hydroxyvitamin D3 (25(OH)D3) concentrations were determined in serum samples harvested in November from ewes grazed outdoors
In regions where the latitudes are above 39°N, such as the UK, the low level of ultraviolet B radiation results in no previtamin D3 being synthesized from 7-Dehydrocholesterol in human skin during exposure to sunlight, from October to March[6,7,8]
The results for five unimproved Scottish Blackface (UBF) ewes were excluded from the data reported here, as either their measured serum 25(OH)D3 concentration, or both 25(OH)D2 and 25(OH)D3 concentrations were beneath the lower quantification limit (7.2 and 5.6 nmol/l for 25(OH)D2 and 25(OH)D3, respectively) of the assay as applied in the current experiment
Summary
Blackface (IBF) and Lleyn ewes kept under Scottish hill conditions. 25-Hydroxyvitamin D2 (25(OH)D2) and 25-Hydroxyvitamin D3 (25(OH)D3) concentrations were determined in serum samples harvested in November from ewes grazed outdoors. In regions where the latitudes are above 39°N, such as the UK (from 49 to 60°N), the low level of ultraviolet B radiation results in no previtamin D3 being synthesized from 7-Dehydrocholesterol in human skin during exposure to sunlight, from October to March[6,7,8] This could lead to low vitamin D status in sheep farmed in such high latitude locations, literature quantifying optimal ultraviolet radiation levels for sheep is difficult to find. We investigated the hypothesis that there is a breed-dependent effect on vitamin D status of sheep in North West Scotland (56°N) and that there is a positive relationship between ewe reproductive performance and vitamin D status To investigate this hypothesis, serum 25(OH)D2 and 25(OH)D3 concentration of three populations of ewes were determined using high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The relationship between vitamin D status of contrasting genotypes, all in the same flock, and breeding outcomes was investigated
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