Selection for Increased Weaning or Yearling Weight in Hereford Cattle. II. Direct and Correlated Responses2

Abstract

Selection was applied from 1964 to 1978 for increased weaning weight (WWL) or yearling weight (YWL) in two Hereford lines. An Angus line was maintained as an unselected control line (CL). Each line was maintained with 50 cows and four sires each year (two sires selected each year and used for 2 yr). Primary traits measured in the lines were birth weight (BW), preweaning daily gain (WDG), weaning weight (WW), weaning conformation grade (WG), weaning condition score (WC), weaning to yearling daily gain (YDG), yearling weight (YW), yearling conformation grade (YG) and yearling condition score (YC). Averaged over two methods, estimated genetic responses/generation (in standard deviation units) in WWL and YWL were: BW, .29, .26; WDG, .17, .15; WW, .22, .19; WG, .19, .26; WC, .12, .12; YDG, -.02, .04; YW, .08, .14; YG, .19, .16; YC, -.13, -.03. The realized heritability estimates were .23 and .15 for WW and YW, respectively. The realized genetic correlation between WW and YW was .69. Progeny from crosses of selected WWL and YWL sires to Angus cows had similar feedlot and carcass performance. At the end of the study, milk yield and composition were similar for mature cows in WWL and YWL.

Effects of Using Sires Selected for Yearling Weight and Crossbreeding with Beef and Dairy Breeds: Birth and Weaning Traits2

“…Hough et al (1985) determined that correlated response and genetic trend for WWT in response to sire selection based upon yearling weight EPDs were 15 -+ 2 kg (P<.01) and 4.6 -+ .7 kg (P<.O1), respectively. Selection for yearling weight increased ADG and WWT, 3.61 + 1.44g'd -1 "yr -1 (P<.01) and 1.00 -+ .31 kg'yr -1 (P<.01), respectively (Frahm et al, 1985).…”

“…Hough et al (1985) found that BWT was increased 1.4 kg (P<.01) in response to openqine selection that used Hereford sires ranked on the basis of their progeny yearling weight performance. Frahm et al (1985) determined that BWT increased .26 kg'yr -1 (P< .01) in response to yearling weight selection. Koch et al (1982a) reported that selection for increased yearling weight and on an index of yearling weight and muscling score increased CD in 2-yr-old, first-calf heifers, Also, selection for weight in all selection lines resulted in increased calf mortality compared with the control line.…”

Potentiality of Growth Traits for Selection to Improve Productivity in Nilotic Cattle

“…Next, we sought to identify which of the correlations among the growth performance traits examined above offer the best selection option in Nilotic cattle, because selections based on growth traits sometimes yield undesirable outcomes. One of such undesirable outcomes is increased incidences of dystocia caused by increased birth weight, which often leads to the calf`s and/or mother`s death [32] and [33]. Indeed, dystocia is not uncommon in Nilotic cattle, although its rate of occurrence and causes remained uninvestigated [34].…”

Evaluation of Aberdeen Angus Breeding Bulls in the Northern Region of the Republic of Kazakhstan

“…Additionally, the selection of cows and heifers in respect of the uterine composition is crucial in achieving breeding herds with appropriate productivity, exterior and constitutional features, milk-producing ability, reproductive ability, good maternal qualities, health, and uniformity. All of these factors rely on the provenance of the cattle; according to those in the field, they must be from outstanding proven bulls [ 15 , 16 , 17 ].…”