Selection Intensity and Response to Selection for Yearling Weight in Beef Cattle

Newman, J. A.; Fredeen, H. T.; Rahnefeld, G. W.

doi:10.4141/cjas73-001

Cited by 48 publications

(27 citation statements)

References 11 publications

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“…Thompson & Juga (1989) showed that the method of Newman et al (1973) is biased downwards as a result of a reduction in variance due to linkage disequilibrium (Bulmer, 1971) and proposed a recursive method to estimate realized heritabilities. Reporting on a selection experiment with sheep, Johnson et al (1995) found lowest realized heritabilities estimated by the method of Newman et al (1973) followed by those estimated using the method of Thompson & Juga (1989) which were similar to, but still lower than, the REML estimates. The low selection response for weaning weight was due to the low REML heritability estimate which was influenced by the presence of sire x year interaction (Beffa et al, 2009b).…”

Section: Resultsmentioning

confidence: 99%

“…Direct and correlated cumulative selection differentials (CSD) were calculated within the control lines using the method of Newman et al (1973) where an individual's selection differential, calculated as a deviation from the mean performance of its contemporary group, is added to the mean accumulated selection differential of all parents contributing progeny to the group. Only pre-weaning weight and weight gain traits were considered as males selected to be parents were managed separately post-weaning.…”

Section: Methodsmentioning

confidence: 99%

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Long-term selection experiment with Afrikaner cattle 3. Selection applied and response in calf growth traits

2009

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________________________________________________________________________________ AbstractA selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, after approximately two generations of selection, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over approximately six generations of selection (40 years) were analyzed. The average age of sires and dams at the time of birth of their progeny was 5.9 and 7.5 years respectively in the pre-crossover phase and was reduced to 4.4 and 6.5 years respectively in the post-crossover phase. The rate of inbreeding across lines and environments was 1.2%/generation. The cumulative selection differential trends for both the S and NS lines for adjusted weaning weight plotted against generation number were very low, relatively linear and greater for the S line (0.10 s.d./year) compared with the NS line (0.08 s.d./year). Direct and correlated responses were uniformly low, approximating 1% of the trait mean per generation, and indicating that considerable attention was given to secondary characters. These results concur with general findings of effective direct and correlated responses of weight traits to individual selection. ________________________________________________________________________________

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Long-term selection experiment with Afrikaner cattle 3. Selection applied and response in calf growth traits

2009

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“…Cattle in the second study consisted of 48 purebred Shorthorn cows ranging in age from 2 to l0 yr and their calves. Twenty-three of these cows belonged to a line that had been selected for yearling weight for a total of 14 yr and the other 25 were from a nonselected control line (Newman et al 1973 (Tilakaratne et al 1980), higher concentration of T3 and T4 (Land et al 1983), and higher level of glucose (Flux et al 1984) For personal use only. (Smith and Goodman 1970) in chickens and to growth rate and milk production in mice (Yamaki and Mizuma 1982).…”

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Blood Composition of Different Beef Breed Types

Tong¹,

Doornenbal²,

Newman³

1986

Can. J. Anim. Sci.

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“…Response to yearling weight selection has been documented by Newman et al (1973) from the data used in this study. All the data were included in one data set even though more than one location was used.…”

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confidence: 99%