- Growth and carcass characteristics of hair and wool type Dorper lambs under veld conditions in the Arid Karoo
|Last update: November 25, 2010 09:08:06 AM|
GROWTH AND CARCASS CHARACTERISTICS OF HAIR AND WOOL TYPE DORPER LAMBS
UNDER VELD CONDITIONS IN THE ARID KAROO
M. A. Snyman, W. J. Olivier, P.J. Griessel & J.A.N. Cloete
Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg (EC), 5900
Due to the limited natural resources in many of the mutton producing areas of South Africa, it is important to increase the efficiency of mutton production within the limits of these resources. It is therefore essential that the most suitable type of sheep for these areas, in terms of adaptability and efficiency, be identified. Dorper sheep constitute a large proportion of the small stock numbers in these areas, and it is therefore obvious that the most efficient type within this breed should be identified. Animals within the Dorper breed are classified into different types, mainly according to their coat cover, conformation or fat distribution. Several perceptions as to the productive and reproductive potential of these types exist among breeders and farmers. One of these is that the hair type Dorper is more hardy and adapted and produces better than the more woolly type under extensive conditions. This study was therefore conducted to evaluate growth, conformation and slaughter traits in hair and wool type Dorper sheep under extensive conditions at the Klerefontein Experimental Station in the north-western Karoo region of the Republic of South Africa. The following data from lambs born from 1993 to 2000 in the hair (n=1070) and wool (n=1044) Dorper flocks were available : birth weight, coat cover score at birth, 42-day and 120-day (weaning) body weight, condition score and coat cover score at 120 days of age, monthly body weight from five to 12 months of age, various conformation traits (measured or assessed subjectively on a linear scale ranging from one to 50 at six months of age), slaughter weight, carcass weight, dressing percentage and various carcass measurements. Leastâ€‘square means procedures (SAS) were used to analyse data from 2114, 1708 and 816 lambs for the growth, conformation and slaughter traits respectively. Birth weight of wool lambs was significantly higher than that of the hair lambs. No differences between hair and wool lambs were found for body weight recorded from 42 days till 12 months of age, nor for pre- or post-weaning growth rate. Coat cover score at birth and weaning differed significantly between hair and wool lambs. Wool lambs also had a higher condition score at weaning ( 28.26 " 0.51 vs. 24.93 " 0.51). Testis circumference of hair ram lambs measured at six months of age was larger than that of the wool type ram lambs (28.09"0.40 cm vs. 27.60"0.40 cm). Hair lambs had a better conformation than wool lambs when considering the traits, chest width and depth, protrusion of the chest between the front legs, shoulders, hind quarters and width of the rump. Wool lambs had a higher body height and length of hind leg, as well as better hocks and less sloped rumps, compared to the hair lambs. No differences in general conformation of the head, width of hind leg, body length, body depth, front or hind pasterns or top line were evident between hair and wool lambs. From these it seems as if the hair lambs were bulkier with shorter legs, compared to the leggier appearance of the wool lambs. Hair and wool lambs were slaughtered at a live body weight of 40.10"0.31 kg and 39.75"0.31 kg respectively. There was no difference in the age when hair and wool lambs reached slaughter weight, as was also evident from the growth performance. The higher dressing percentage recorded for wool lambs (49.88"0.14 % vs. 48.96"0.13 %) resulted in their higher carcass weights (19.56"0.06 kg vs. 19.19"0.05 kg). Carcass length (108.47"0.14 cm vs. 107.16"0.13 cm) and length of hind leg were longer in wool than hair lambs. With regard to fat measurements, no significant differences were observed between groups. It therefore follows that there should be no difference in carcass grading between types, as grading is based primarily on V3 fat measurements. It is concluded that, in terms of the economically important growth and carcass traits, there are no differences between hair and wool Dorpers. Differences that do occur, such as some conformation and carcass traits, will not have any effect on the economic realisation from the different types.