![]() | Only 14 pages are availabe for public view |
Abstract SU!UIAlly This work was carried out on Dokki-4 chickens (as a na~ive breed) raised in the Poultry Research Farm at Inshas (Sharkia Governora~e), Animal Production Research Institute, Ministry of Agriculture, Egypt. A ~otal number of 4057 progeny produced by 3S aires in three consecutive hatches were collected in the period from March 1979 ~o June”1980. Data of individual body weight (DV) at hatch and biweekly thereafter up to 12 weeks of age were analysed. Other growth traits such as daily gain (DG), absolute gain (AG) and relative growth rate (BS) between 0-4, 4-8, 8-12 and 0-12 weeks of age were analysed separa~ely. Kixed Kodel analyses were performed in order to quantify the average genetic, phenotypic and environmental variation and covariation of such growth traits and to a••••• the direct and correlated re.pon.e. expected from selection for these traits. The follOWing reSUlts were obtained: (1) DG and AS of Dokki-4 chickens increased wi~h the advancement of age. KG was higher (137.45%) at the early s~age. (0-4 weeks), then decreased gradually with the advancement of age at the interval of 8-12 weeks. (2) Coefficient. of variation (CV) for growth ~ralt. are tended generally ~o increase as the chick advaneeed in age. The AS and KG during the period of 0-4 weeks were 19.83% and 7.2% compared to 31.12% and 22.88% during the period of 8-12 weeks, respectively. (3) Higbly .ignificant difference. (P(O.OS or P(O.Ol or P<O.001) due to effects of hatch, .ex and ba~cb x sex interaction for mo.t growth trait. were o~ined. (4) The difference. due ~o sire. and daas for all growtb trait. at diff.ren~ ages were highly .lgnlficant (P(O.01 or P<O.001). Perc.n~ •• (~) of sire, daa .i~ln .ire and error component. of variance are variable for different growth trait. • S••11 proportiona of variation eft) due to sire eff.c~s on B1J (2.4’) and.on bo’thD6 and M (2.7’) .ere obtained. Ho.ever, large proportions of variation due to daIII effect. were recorded at all ag.. coaparabl. to ~o.. of sire. It ranged.froll 13.8. to 27.~ for _ (with an average of 19.~) and 12._ ’to17._ for both D8 6. AS (1fi~ an average of 14.5*). ” ” (5) Bo con.i.~ent treDd for e.ti••t•• of b.ri~ility fra. paternal half-sibs (b2s) was observed for growth trai~s. In ~---- 0’ __ - • •• ~ __ , , ~ • __ , • 91 general, low estimates of b2• for all growth traits were obtained which ranged from-0.041 to 0.153 with an average estimate equal to 0.097. The heritability estimates from maternal half-sib. (b2D) ranged from 0.553 to 1.079 (with an average equal to 0.760) for BW and from 0.511 to 0.717 (with an average equal to 0.614) for both DG and AG. Estimat•• of h2D for RG ranged from 0.343 to 0.602 (with an average equal to 0.485). The estimates of heritability based on full-siba (h2s+D) for growth traits at different age intervals were moderate or high which ranged between 0.312 to 0.606 for aw (averaged 0.429), 0.317 to 0.395 for both DG & AG (averaged 0.357) and between 0.227 to 0.360 for RG (averaged 0.289). (6) All estimates of phenotypic correlation (rp) and both of genetic (re) and environmental (rE) from paternal half-sib (PHS), maternal half-sib (KHS) and full-sib (FS) components among aw, DG and AG at different ages were positive and of moderate or high magnitude, and tended to decrease in value as the differences between the two ages get larger. (7) Expected estimates of annual direct genetic progress based on PHS for BY selected for hatch-, 2-, 4-, 6-, 8-, 10- and 12-week weight are 0.12, 0.75, 2.97, 1.74, 3.21, 2.71 ~nd 4.23 grams per chick per generation, respectively. The corresponding estimates based on FS were 0.80, 3.41, 4.98, 7.66, 11.85, 16.42 and 22.62 grams in the same order. Selection for 4-we.1t body weigh1: and for both AG & R6 at In1:ervalof 0-4 weeks of age have been generally associated with a moderate or high rate of expected correlated response in growth traits a1:subsequent ages. |