@conference {40816,
	title = {Prediction of carcass tissue weight in vivo using live weight, ultrasound or X-ray CT measurements},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {205-211},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Twenty-one Dorset Down ewe hoggets (49.4kg body weight, 9months  old) were scanned by ultrasound and X-ray computer tomography (CT).  Total carcass tissue (fat, muscle and bone) weights were assessed by the  Cavalieri procedure from 16-18 CT slices per animal. Additional CT slices  were taken at four anatomical reference sites; 7th thoracic (TV7), 2nd  lumbar and 5th lumbar vertebrae (LV5), and mid-shaft of the femur.  Subcutaneous fat depth and muscle depth were assessed over the last rib  using ultrasound. Body weight, ultrasound measurements and reference slice  carcass tissue areas were used to predict total carcass tissue weights by  multiple regression techniques. In combination with BW, single CT slices predicted tissue weight more  accurately than ultrasound measurements with BW for fat (R2=72-84\% vs.  63\%) but not for muscle (R2=79-87\% vs. 83\%) or bone (R2=62-66\% vs.  65\%). The best combination of two CT slices was TV7 \& LV5. In  combination with BW these improved prediction accuracy further (fat,  R2=92\%, muscle, R2=91\%, bone, R2=71\%). It is possible that data from a single CT slice predict carcass tissue weight  less accurately than expected due to anatomical registration errors despite  CT producing better quality images than ultrasound. These errors are  attributed to scanning protocol constraints for CT equipment.  Two or more CT slices need to be scanned in order to predict tissue weight  more accurately than ultrasound.},
	issn = {1176-5283},
	author = {Young MJ and Nsoso SJ and Logan CM and Beatson PR}
}
@conference {40611,
	title = {Genetic and phenotypic parameters associated with lean tissue growth in Dorset Down sheep},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {251-254},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Genetic and phenotypic parameter estimates were derived from  
performance data collected over nine years for the Lincoln University Dorset  
Down flock.  Data were for animals born each spring and run at pasture.  Ewes  
(n=922) were measured in autumn and rams (n=819) in winter.  Measurements  
were live weight and <I>in vivo</I> fat and muscle depths. 
 
Genetic and phenotypic parameters were estimated using multi-variate  
AIREML analyses by fitting an individual animal model with animal as a  
random effect, birth rank, age of dam and year of birth as fixed effects  
and age at measurement as a covariate.  Multi-variate heritability estimates  
({\textpm} s.e.) for live weight, fat and muscle depths were 0.42 ({\textpm}0.04), and 0.30({\textpm}0.05)  
for rams and 0.26({\textpm}0.01), 0.20({\textpm}0.05) and 0.13({\textpm}0.03) for ewes respectively.   
Estimates of genetic correlations were generally moderate to high for the two  
sexes.  The genetic correlation between live weight and fat depth was significantly  
different for the two sexes, with rams (0.42{\textpm}0.10) having a higher value than  
ewes (0.24{\textpm}0.02).  Phenotypic correlations differed between the sexes, with  
estimates for ewes being slightly higher.  For both sexes, parameter estimates  
were different from those used to derive the indices used to select for lean  
tissue growth, ram estimates being consistently higher while those for ewes  
were more equivocal. },
	issn = {1176-5283},
	author = {Nsoso SJ and Young MJ and Beatson PR and Bell ST}
}
@conference {40612,
	title = {Responses to selection for lean tissue growth in Dorset Down sheep},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {255-260},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Responses to selection using a lean tissue growth index were estimated  
from performance data of the Lincoln University Dorset Down flock.  Data  
were available for ewes (n=922) born in the years 1984 - 1991 and rams  
(n=816) born in 1984 - 1992.  Data were from two closed lines, one control and  
the other selected for high lean tissue growth.  Initially selection was on the  
basis of an index comprising measurements of live weight and fat depth.   
Subsequently muscle depth was incorporated into the index.  Ewes and rams  
born in spring each year were run separately at pasture from weaning (late  
summer) onwards.  Performance testing was in the following autumn for ewes  
and winter for rams.  Measurements were live weight and <I>in vivo</I> ultrasonic 
fat and muscle depths.  Responses were calculated from regression of the  
difference between the line means for breeding value against time.  Breeding  
value estimates were derived by AIREML analyses. 
 
Both sexes exhibited desirable responses in all component traits: rams;  
+0.290kg/yr, +0.019mm/yr and -0.013mm/yr and ewes; +0.154kg/yr,  
+0.028mm/yr and -0.028mm/yr for live weight, muscle and fat depths  
respectively.  Increases in muscle depth occurred after it was incorporated  
into the selection index. },
	issn = {1176-5283},
	author = {Nsoso SJ and Beatson PR and Young MJ and Logan CM}
}
