Reproductive performance of pregnant red deer hinds fed swede forage-crops in winter

Reproductive wastage has been identified as a significant cause of productivity loss in New Zealand deer herds. The objective of this study was to investigate the impact on reproductive performance of red deer hinds fed swedes over winter. Forty rising two-year-old and 40 mixed-aged pregnant hinds were drafted into two groups each and grazed for 100 days over winter on either a swede forage-crop or pasture. Hinds were blood sampled regularly, weighed fortnightly and pregnancy scanned monthly. Blood samples were analysed for blood urea nitrogen and indicators of liver damage. Swede forage-crops were sampled for nutrient and toxin concentrations. No significant differences in hind foetal loss were found between the two wintering systems or two age classes. Swede toxin levels were above thresholds considered dangerous for animal consumption but no liver damage was indicated. Blood urea nitrogen levels did not differ between the swede and pasture fed hind groups until day 80, which was 10 days after the swede groups were transferred to another swede crop, when levels were significantly lower in the swede groups. This research indicated that grazing on swedes did not influence reproductive wastage in this instance, however the effect of low protein intake over an extended period during pregnancy needs to be investigated further.