Abstract

Genetic variation of foot and jaw 'abnormalities' in ewe hoggets and ewes has been studied with several breeds and strains at the Rotomahana Research Station. Foot and digit placement, foot roll, pastern angle and degree of hoof growth were scored for all 4 feet of each sheep at 9 months, 18 months and 5 years of age. Teeth occlusion, measured as the distance in mm (+ or -) between the front surface of the central incisors and the anterior edge of the upper pad, was recorded at 18 months and 5 years of age. Differences in incidence of foot abnormalities at 18 months of age among 2251 ewe hoggets representing 6 Romney strains and Coopworth or Border Leicester x Romney crosses, were significant for all traits except foot roll and digit placement. Border Leicester cross hoggets had a lower incidence of foot placement, pastern angle and hoof growth abnormalities than straightbred Romneys or Coopworth crosses. In a separate trial, 602 Booroola Merino first cross hoggets out of Romney and Perendale ewes had a significantly higher incidence of foot abnormalities than 480 straightbred Romney or Perendale ewe hoggets for all traits recorded at 18 months of age except pastern angle. There were only small differences among Romney strains and among breeds and crosses for teeth occlusion. Paternal half sib heritability estimates of foot traits recorded at 9 months of age were low (less than 0.11) and non-significant except for hoof growth (0.18 to 0.29). Similar heritability estimates for hoof growth were found in 189 month ewe hoggets (0.14 to 0.27) with low to moderate estimates for the other foot traits (0.02 to 0.17), and teeth occlusion (0.13 to 0.25). Heritability estimates were similar in 5- year-old-ewes for foot traits (0.03 to 0.20) but increased with age for teeth occlusion (0.36). Correlations between foot traits recorded at 18 months and 5 years of age were low (0.08 to 0.25), but were higher for teeth occlusion (0.49). Foot abnormalities and teeth occlusion were not found to have significant effects on either hogget growth, wool production or ewe reproduction, live weight or wool production. It is concluded that undue culling emphasis in ewes or rams on teeth or feet abnormalities is not warranted and may be counter productive.

H, Smit, and BW Wickham

Proceedings of the New Zealand Society of Animal Production, Volume 46, , 77-82, 1986