Browsing by Author "Cloete J.J.E."

Now showing 1 - 6 of 6
  • No Thumbnail Available
    Item
    A comparison between slaughter traits and meat quality of various sheep breeds: Wool, dual-purpose and mutton
    (2012) Cloete J.J.E.; Hoffman L.C.; Cloete S. W. P. (Schalk Willem Petrus van der Merwe)
    The slaughter and meat quality traits of 20-month-old wool (Merino), dual-purpose (Dohne Merino and South African Mutton Merino [SAMM]) and mutton (Dormer) type sheep were compared. Average live weights of SAMM and Dormer sheep were 23% heavier than those of Dohne Merinos which were 28% heavier than Merinos. Fat depths at the thirteenth rib and lumbar regions of Merino and Dohne Merino sheep were lower than those of SAMM and Dormer sheep. The cooking loss, drip loss and shearing value from the M. longissimus dorsi did not differ between breeds. The initial juiciness and sustained juiciness of meat from Merinos were rated significantly lower by sensory analysis. Meat from Dohne Merino was rated significantly more tender for the attribute first bite. It was demonstrated that Dormer and SAMM sheep had heavier but fatter carcasses than Merinos and Dohne Merinos, with differences in meat quality between breeds. © 2012 Elsevier Ltd.
  • No Thumbnail Available
    Item
    A comparison between the body composition, carcass characteristics and retail cuts of South African Mutton Merino and Dormer sheep
    (2004) Cloete J.J.E.; Hoffman L.C.; Cloete, S. W. P. (Schalk Willem Petrus van der Merwe); Fourie J.E.
    The body composition, carcass characteristics and retail cuts of 61 Dormers (21 rams and 40 ewes) and 35 South African Mutton Merinos (SAMM) (17 rams and 18 ewes) were determined. A range of carcass measurements was recorded. Since there was no sex x breed interaction, only main effects of breed and sex were considered. There were no differences in slaughter weight between Dormer and SAMM sheep at 18 months of age. Dormers had a 2.7% point higher dressing percentage and a 6.2% higher carcass weight than the SAMM. The Dormer had a higher fat content (kidney fat, back-fat depth) than the SAMM. The eye-muscle area of the Dormers was 13% larger than that of the SAMM sheep. Rams were heavier than the ewes at slaughter. All the traits measured, indicated advantages in favour of rams. Only the saturated, monounsaturated fatty acids and polyunsaturated fatty acids to saturated fatty acids ratio differed significantly between the Dormer and SAMM sheep. Based on the fatty acid profile, SAMM meat is slightly healthier than that of Dormer sheep. The higher retail cut weights of Dormers suggested that they were superior to the SAMM as far as meat production was concerned.
  • No Thumbnail Available
    Item
    Behaviour of Merinos divergently selected for multiple rearing ability in response to external stimuli
    (2005) Cloete J.J.E.; Cloete S.W.P.; Hoffman L.C.
    Data of Merino sheep descended from two divergent selection lines for (H line) and against (L line) multiple rearing ability were collected in three different trials to compare response to stressful situations between lines. Trial 1: the behaviour of 138, 20-month-old sheep born in 2001 and 124, 8-month-old sheep born in 2002 were observed in an arena test. Experimental animals amounted to 111 and 101 for the H line in the respective years. Corresponding numbers for the L line were 27 and 23, respectively. Progeny born in 2001 were accustomed to handling, as the tests were performed shortly after routine performance recording. Lambs born in 2002 were unaccustomed to handling when tested. Progeny from the H line born in 2002 allowed a smaller (P < 0.01) minimum distance between them and the human operator seated between them and a group of similar aged sheep than L line contemporaries. Progeny born in the L line during 2002 defecated more (P < 0.05) frequently than H line contemporaries. No line differences were found in progeny born during 2001. Trials 2 and 3 were designed to test whether the putative line difference in stress response would impact on physical meat quality. Trial 2: a total of 103, 18-20-month-old progeny from the two selection lines were slaughtered during 2001, 2002-2003. Mean slaughter weight, dressing percentage and carcass weight of H line animals were between 5 and 13% higher (P < 0.05) than that of L line animals. There were no differences in cooking loss, drip loss and tenderness between the two lines. As pertaining to the meat colour, L line progeny had less vivid red meat, as seen by their lower (P < 0.05) a* colour reading and chroma values. The L line animals had lower (P < 0.01) initial pH values as measured in the Musculus longissimus dorsi. These results are indicative of susceptibility to acute, short-term stress. Trial 3: 20 progeny of the two selection lines were slaughtered and their muscle pH measured at 11 intervals from 45 min to 48 h post slaughter. As in Trial 1, the initial pH of the L line animals were lower (P < 0.05) than that of H line animals. An opposite tendency was observed by 48 h post slaughter. The obtained results support a hypothesis that divergent selection for ewe multiple ability resulted in adaptations to cope with unfamiliar conditions. © 2005 Elsevier B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Effect of production system on the growth rate, carcass characteristics and carcass composition of Dorper lambs
    (2012) Cloete J.J.E.; Hoffman L.C.; Claasen B.; Cloete S. W. P. (Schalk Willem Petrus van der Merwe)
    An investigation on the effect of production system on growth rate, carcass characteristics and carcass composition of Dorper lambs was carried out under South African conditions. The study involved sixty lambs which were divided into two production/feeding groups (feedlot (FL) vs. free-range (FR)) at weaning. Each group consisted of 10 lambs from three gender classes (ewes, rams and castrates). The FL-lambs were fed a commercial pelleted ration while the FR-group grazed natural pastures. The production system x gender interaction indicated that male lambs (castrates and rams) grew twice as fast as ewes under FL-conditions. Gender groups were less pronounced in FR-lambs. FL-lambs produced heavier carcasses, higher dressing percentages and greater carcass fatness levels than FR-lambs. Ram lambs attained heavier slaughter weights and produced heavier carcasses than ewe lambs with castrates being intermediate. Production system did not have an effect on intramuscular lipid concentration, barring a tendency in the Biceps femoris muscle. It was concluded that the FL-diets were generally associated with better lamb growth rates, greater carcass fatness and an improved dressing percentage. Although animal performance was generally improved in the more intensive FL-system, it was also concluded that discerning consumers will likely prefer the more natural (and therefore more ethically acceptable) FR-meat.
  • No Thumbnail Available
    Item
    Sensory and objective mutton quality characteristics of SA Merino sheep selected for and against reproductive fitness
    (2003) Hoffman L.C.; Schmidt D.; Muller M.M.; Cloete J.J.E.; Cloete S.W.P.
    The effect of divergent selection for ewe multiple-rearing ability over a 15-year period on mutton quality was examined on the M. longissimus dorsi and M. semimembranosus of entire rams (R) and ewes (E) derived from two Merino lines. The selection of these two lines was based on maternal ranking values for multiple-rearing ability in a positive (P) and negative (N) line. In the negative line the replacements were based on the progeny of ewes that rear less than one lamb per joining or lambing opportunity (i.e. failed to lamb or lost all progeny born at least once). Progeny of ewes that reared more than one lamb per joining (i.e. reared twins at least once) were selected for the positive line. Ratings of sensory quality characteristics on the M. semimembranosus of the different genotype lines were obtained from a trained taste panel and related to data on physical and chemical characteristics. The moisture, total lipids, protein, ash, mineral concentrations and fatty acid composition of the M. semimembranosus were obtained. Physical parameters measured on the M. longissimus dorsi were: ultimate pH (pH48), drip loss, cooking loss and Warner-Bratzler shear force (WBS). The influence of selection line on the sensory characteristics of the mutton was generally negligible, with the exception of the sensory attribute of first bite, where meat derived from the positive line was rated to be less tender than that of the negative line contemporaries. Chemically, the meat derived from the four different groups differed significantly in moisture and lipid content. The Positive Ram (PR) group had the highest moisture (ca. 76%) and the lowest lipid (ca. 7%) concentrations, whereas the Negative Ewe (NE) group had the lowest moisture (ca. 70%) and the highest lipid (ca. 10%) concentration. No significant differences were detected in the proximate chemical composition between the P and N lines. The pH48 and WBS values showed significant differences between the four groups. The Negative Ram (NR) group had the highest pH48 and the lowest WBS values. Results indicated a line effect on WBS tenderness. Meat derived from the positive line was less tender compared to the meat from the negative line. Differences between the reproductive lines pertaining to the mineral and fatty acid composition were also noted. A general tendency found, was for the Positive Ewes (PE) to have the highest and the NE to have the lowest mineral concentration. Significant differences were detected between the four groups in the individual fatty acids arachidic acid (C20:0), lignoceric acid (C24:0), eicosenoic acid (C20:1n-9), linoleic acid (C18:2n-6), homo-γ-linolenic acid (C20:3n-6), arachidonic acid (C20:4n-6), eicosapentaenoic acid (C20:5n-3), docosadienoic acid (C22:2n-6), docosapentaenoic acid (C22:5n-3) and docosahexaenoic acid (C22:6n-3) concentrations. The PR group had the highest total PUFA (polyunsaturated fatty acids) content (ca. 8%) and the NR the lowest PUFA content (ca. 6%). The positive group had significantly higher C18:2n-6, C20:3n-6, C20:4n-6, C20:5n-3, C22:5n-3 and C22:6n-3 concentrations in comparison with the negative line. Significant difference in the total PUFA composition was also detected between lines, with the positive line showing a higher concentration (ca. 7%) compared to the negative line (ca. 6%).
  • No Thumbnail Available
    Item
    Terminal crossbreeding of Dorper ewes to Ile de France, Merino Landsheep and SA Mutton Merino sires: Ewe production and lamb performance
    (2007) Cloete J.J.E.; Cloete S.W.P.; Olivier J.J.; Hoffman L.C.
    The effect of crossing Dorper ewes with Ile de France (IdF), Merino Landsheep (ML) and SA Mutton Merino (SAMM) rams in a terminal crossbreeding program was investigated during 2000 and 2001. Expressed as percentage of purebred Dorper lambs, the average birth weights of IdF cross and ML cross lambs were increased by 12 and 7%, respectively. Crossbred progeny of IdF sires were 10% heavier than purebred Dorpers at weaning. A corresponding difference in favour of ML sires amounted to 5%. IdF crossbred lambs reached slaughter weight earlier than the other cross lambs and purebred Dorper lambs. Lamb mortality prior to weaning was unaffected by the breed of the service sire, and ranged between 0.13 for lambs sired by IdF rams to 0.22 for purebred Dorper lambs. Ewe joining weight, as well as number of lambs born and weaned per ewe lambed was independent of the breed of the service sire. When weight of lamb weaned per ewe lambed was considered, there was a tendency towards higher lamb outputs in ewes that were joined to IdF and SAMM sires. Estimated repeatability derived for joining weight and the various measures of reproduction generally accorded with literature estimates. Backfat depth (taken at the 13th rib, 25 mm from the midline) indicated that purebred Dorper lambs had a thicker fat cover compared to all combinations of crossbred lambs. Corresponding sire breed differences were found between the 3rd and 4th lumbar vertebra, 25 mm from the midline. Terminal crossbreeding of Dorper ewes with IdF, ML and SAMM sires did not deleteriously affect lamb growth and survival or ewe reproduction. Terminal crossbreeding could thus be implemented in commercial Dorper flocks, without compromising productivity and/or product quality. © 2005 Elsevier B.V. All rights reserved.