THE FLEECE TYPE OF SHEEP AND ITS ROLE IN THE ADAPTATION TO SEMI-ARID ENVIRONMENTS. | ||||
| Journal of Animal and Poultry Production | ||||
| Article 5, Volume 30, Issue 1, January 2005, Page 159-171 PDF (618.26 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jappmu.2005.237951 | ||||
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| Authors | ||||
| R. A. Guirgis,1; M. M. El-Ganaieny1; E. A. Kotby2; Safaa O. Amin2 | ||||
| 1Desert Research Center, Matareya, Cairo, Egypt. | ||||
| 2Department of Animal Production, College of Agriculture, Ain Shams University, Shubra El-Kheima, Cairo, Egypt. | ||||
| Abstract | ||||
| This study was carried out on 201 lambs, 110 of local coarse wool desert Barki sheep and 91 5/8 Merino 3/8 Barki, born during the winter and raised under semi-arid conditions. Ambient temperature ranged from 11.1 to 20.8 ؛C, during winter, and 33.4 to 38.6 ؛C, during the summer. The purpose of the study was to investigate the role played by coat type, from birth to the adult stage (16 months of age) on thermoregulation, hence adaptation to the prevailing semi-arid conditions. Newly born lambs were classified, in an increasing order of halo hair density, into 7 grades, which were grouped into three types: Type 1, the lower birthcoat halo hair grades (1,2,3), Type 2, the medium grades (4,5) and Type 3, the high halo hair grades (6,7). A third of the local Barki lambs birthcoats are of the medium type, and two thirds of the high type, whereas the of 5/8 Merino crossbred lambs were distributed between the low type ( 34.07%), the medium type (38.46%) and the high type (27.47%). Lambs, regardless of breed, with lower type of birthcoat (1) retained more heat during winter, followed by Type 2 and the least was Type 3. Type 1 birthcoat, with its short, dense wavy appearance, compared to Types 2 & 3 with the long, less dense, straight and higher content of coarse fibers, provided more protection during winter. Lambs with Type 1 birthcoat were more comfortable during winter where the respiration rate, RR, was the lowest and increased towards type 3. Lambs were regraded, at 2 months of age up to the 1 st shearing at 16 months of age, with a trend of increase, from type 1 to type 3, in coat depth, belly staple length and kemp score and a reversed trend in staple structure, where type 3 had more open structure. Rectal temperature, RT, of the three regraded types were almost similar. However, a trend of decrease in RR occurred towards Type 3. At the first fleece level, a trend of an increase was encountered in staple length, mean fiber diameter, kemp, coarse fibers and medullation index and a reversed trend in fine fibers % towards Type 3. This paralleled a trend of decrease in RR, towards higher fleece types, where type 3 was the most comfortable and favorable during the prevailing hot summer. A general trend of increase, towards higher coat type was encountered in birth, weaning and yearling weights, birth-weaning and weaning –yearling daily gains and daily production (grammes) of greasy fleece and clean fleece weights. Lower types of birthcoat, 1 and 2 in crossbreds and 2 in Barki, were the best in thermoregulation during winter (lambing season), as they retained more heat, compared to the high type 3. When lambs were regraded, during the period 2-16 months, and at the adult fleece level (16-month) the same trend was observed. Regardless of breed group, a general trend was reported of an increase in reproductive efficiency, as kilograms weaned per animal joined at mating, of ewes that had type 1 towards higher types. Values were 10.98, 11.29 and 11.43kg for types 1,2 and 3, respectively. However, selection would be chanelled towards the reproductive efficiency suitable to the prevailing environmental conditions, which would reflect adaptation, and this would mean certain fleece type. | ||||
| Keywords | ||||
| Wool coat; Thermoregulation; Adaptation; Semi-arid environments | ||||
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