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R W Purchas - One of the best experts on this subject based on the ideXlab platform.

  • patterns of change with growth for muscularity and other composition characteristics of Southdown rams selected for high and low backfat depth
    New Zealand Journal of Agricultural Research, 1998
    Co-Authors: A Y Abdullah, R W Purchas, A S Davies
    Abstract:

    Abstract Male Southdown sheep ranging in age from birth to near maturity (c. 28 mo) from genetic lines selected for about five generations for increased (n = 40) and decreased (n = 40) weight‐adjusted ultrasonic backfat depth were used to investigate patterns of change in muscularity and other composition characteristics. Measures of muscularity in terms of muscle depth relative to bone length were greater for the high‐backfat line in anatomical areas around or beside the femur, tibia, total pelvic limb, humerus, and scapula, but not the radius/ulna. Levels of muscularity increased at a decreasing rate with increasing carcass weight from about 1 to 36 kg in all areas. Where there was a genetic line effect on muscularity, this tended to be greater at higher carcass weights, with minimal differences at birth. Muscle to bone ratios corresponding to these measures of muscularity showed similar patterns of change and line differences. Leg bone weight was higher for the low‐backfat line; for the same femur leng...

  • direct and correlated responses to selection for high or low ultrasonic backfat in depth in Southdown sheep
    New Zealand Journal of Agricultural Research, 1993
    Co-Authors: J Solisramirez, H T Blair, R W Purchas
    Abstract:

    Abstract Direct selection for high or low liveweight-adjusted backfat depth (LABF), assessed by ultrasound at Position C over the longissimus dorsi muscle at the last rib, in Southdown sheep resulted in highly significant differences (3.7 versus 2.0 mm at 33 kg liveweight for rams, P < 0.01) between the lines after 8 years of selection. The response to selection per unit of cumulative selection differential was generally high and apparently linear. A generation interval of 3.01 years was estimated resulting in c. 2.7 generations of selection for 1986-born animals. Correlated responses in birth weight, pre-weaning growth, and post-weaning growth were not significant. However, consistent correlated responses were observed in liveweight-adjusted height and length over the selection period with low-line animals being longer and taller. These responses imply a negative genetic correlation between these traits and LABF. It was concluded that divergent selection for LABF was effective, resulting in lines with si...

  • meat quality and muscle fibre type characteristics of Southdown rams from high and low backfat selection lines
    Meat Science, 1993
    Co-Authors: I T Kadim, R W Purchas, A S Davies, A L Rae, R A Barton
    Abstract:

    Characteristics of the meat of 15–18-month Southdown rams from lines selected for high or low backfat depths (assessed ultrasonically at position C over the last rib) were compared. Half of the carcasses were electrically stimulated (ES) and within each carcass post-mortem treatments chosen to produce effects on meat tenderness were ageing periods of 1 or 15 days (Semimembranosus), early or delayed chilling (Biceps femoris), and trimming of the s.c. fat cover (Longissimus dorsi). These treatments had the expected effects on shear values, but the sizes of the effects were little affected by selection line or ES treatment. Selection line did not have any direct effects on shear values, reflectance values at several wavelengths, waterholding capacity, cooking loss or sarcomere length. The Semitendinosus muscle had a higher proportion of predominantly oxidative fibres for the high-backfat line, based on succinic dehydrogenase activity (P < 0·05), but there was no line difference in alkaline-stable ATPase activity in the same muscle. Muscle fibre diameter was similar for the two lines.

  • an objective measure of muscularity changes with animal growth and differences between genetic lines of Southdown sheep
    Meat Science, 1991
    Co-Authors: R W Purchas, A S Davies, A Y Abdullah
    Abstract:

    A measure of muscularity, based on objective measurements, and expressed in terms of muscle depth relative to skeletal dimensions, is proposed and investigated using a simulation model. Average muscle depth is assessed as the square root of the muscle weight per unit length of a bone adjacent to the muscle. Muscularity is then defined as average muscle depth divided by bone length. Evidence based on a theoretical model, results from the literature and data from backfat selection lines of Southdown sheep is used to illustrate how muscularity defined in this way changes with growth, and the extent to which it parallels changes in muscle to bone ratio. It is concluded that although these two characteristics often change together there are situations where differences in muscularity are not accompanied by differences in muscle to bone ratio and vice versa.

R A Barton - One of the best experts on this subject based on the ideXlab platform.

  • meat quality and muscle fibre type characteristics of Southdown rams from high and low backfat selection lines
    Meat Science, 1993
    Co-Authors: I T Kadim, R W Purchas, A S Davies, A L Rae, R A Barton
    Abstract:

    Characteristics of the meat of 15–18-month Southdown rams from lines selected for high or low backfat depths (assessed ultrasonically at position C over the last rib) were compared. Half of the carcasses were electrically stimulated (ES) and within each carcass post-mortem treatments chosen to produce effects on meat tenderness were ageing periods of 1 or 15 days (Semimembranosus), early or delayed chilling (Biceps femoris), and trimming of the s.c. fat cover (Longissimus dorsi). These treatments had the expected effects on shear values, but the sizes of the effects were little affected by selection line or ES treatment. Selection line did not have any direct effects on shear values, reflectance values at several wavelengths, waterholding capacity, cooking loss or sarcomere length. The Semitendinosus muscle had a higher proportion of predominantly oxidative fibres for the high-backfat line, based on succinic dehydrogenase activity (P < 0·05), but there was no line difference in alkaline-stable ATPase activity in the same muscle. Muscle fibre diameter was similar for the two lines.

A S Davies - One of the best experts on this subject based on the ideXlab platform.

  • patterns of change with growth for muscularity and other composition characteristics of Southdown rams selected for high and low backfat depth
    New Zealand Journal of Agricultural Research, 1998
    Co-Authors: A Y Abdullah, R W Purchas, A S Davies
    Abstract:

    Abstract Male Southdown sheep ranging in age from birth to near maturity (c. 28 mo) from genetic lines selected for about five generations for increased (n = 40) and decreased (n = 40) weight‐adjusted ultrasonic backfat depth were used to investigate patterns of change in muscularity and other composition characteristics. Measures of muscularity in terms of muscle depth relative to bone length were greater for the high‐backfat line in anatomical areas around or beside the femur, tibia, total pelvic limb, humerus, and scapula, but not the radius/ulna. Levels of muscularity increased at a decreasing rate with increasing carcass weight from about 1 to 36 kg in all areas. Where there was a genetic line effect on muscularity, this tended to be greater at higher carcass weights, with minimal differences at birth. Muscle to bone ratios corresponding to these measures of muscularity showed similar patterns of change and line differences. Leg bone weight was higher for the low‐backfat line; for the same femur leng...

  • meat quality and muscle fibre type characteristics of Southdown rams from high and low backfat selection lines
    Meat Science, 1993
    Co-Authors: I T Kadim, R W Purchas, A S Davies, A L Rae, R A Barton
    Abstract:

    Characteristics of the meat of 15–18-month Southdown rams from lines selected for high or low backfat depths (assessed ultrasonically at position C over the last rib) were compared. Half of the carcasses were electrically stimulated (ES) and within each carcass post-mortem treatments chosen to produce effects on meat tenderness were ageing periods of 1 or 15 days (Semimembranosus), early or delayed chilling (Biceps femoris), and trimming of the s.c. fat cover (Longissimus dorsi). These treatments had the expected effects on shear values, but the sizes of the effects were little affected by selection line or ES treatment. Selection line did not have any direct effects on shear values, reflectance values at several wavelengths, waterholding capacity, cooking loss or sarcomere length. The Semitendinosus muscle had a higher proportion of predominantly oxidative fibres for the high-backfat line, based on succinic dehydrogenase activity (P < 0·05), but there was no line difference in alkaline-stable ATPase activity in the same muscle. Muscle fibre diameter was similar for the two lines.

  • an objective measure of muscularity changes with animal growth and differences between genetic lines of Southdown sheep
    Meat Science, 1991
    Co-Authors: R W Purchas, A S Davies, A Y Abdullah
    Abstract:

    A measure of muscularity, based on objective measurements, and expressed in terms of muscle depth relative to skeletal dimensions, is proposed and investigated using a simulation model. Average muscle depth is assessed as the square root of the muscle weight per unit length of a bone adjacent to the muscle. Muscularity is then defined as average muscle depth divided by bone length. Evidence based on a theoretical model, results from the literature and data from backfat selection lines of Southdown sheep is used to illustrate how muscularity defined in this way changes with growth, and the extent to which it parallels changes in muscle to bone ratio. It is concluded that although these two characteristics often change together there are situations where differences in muscularity are not accompanied by differences in muscle to bone ratio and vice versa.

Allen L Jenny - One of the best experts on this subject based on the ideXlab platform.

  • naturally occurring scrapie in Southdown sheep
    Journal of Veterinary Internal Medicine, 1999
    Co-Authors: Jeff W Tyler, Dusty M Weaver, James R Turk, Katherine I Orourke, Michael G Harrington, William Taylor, Allen L Jenny
    Abstract:

    The purpose of this study was to characterize naturally occurring scrapie in the Southdown breed of sheep. Experimental subjects included 4 Southdown ewes admitted to the University of Missouri, College of Veterinary Medicine Large Animal Clinic. All 4 sheep had signs compatible with clinical scrapie. Cerebrospinal fluid (CSF) cell counts ranged from a low of 1 nucleated cell/microL to high of 4 cells/microL with a median of 3 cells/microL. Cerebrospinal protein concentrations ranged from 26 to 78 mg/dL with a median of 53 mg/dL. Immunoassay of the CSF for the 14-3-3 protein yielded positive results in 3 of the 4 sheep. Sequencing of the prion protein (PrP) gene revealed that all 4 sheep were homozygous for glutamine at codon 171 and, hence, were of the QQ genotype. Histopathologic examination of brain stem tissue sections revealed intracytoplasmic neuronal vacuolation and mild spongiform changes in the gray matter neuropil in all 4 ewes. The diagnosis of scrapie was confirmed by immunohistochemical staining for the abnormal PrP Our results suggest that the genetics of scrapie susceptibility are probably similar in Suffolk and Southdown sheep. Positive immunoassay results for the 14-3-3 protein were observed in 3 of the 4 sheep.

O. Bentancur - One of the best experts on this subject based on the ideXlab platform.