scholarly journals The Cambridge sheep — its exploitation for increased efficiency of lamb production

1988 ◽  
Vol 60 (6) ◽  
pp. 585-590
Author(s):  
J. B. Owen ◽  
I. AP Dewi
Keyword(s):  
Litter Size ◽  
Large Range ◽  
Major Gene ◽  
Ovulation Rate ◽  
Gene Effect ◽  
Generation Interval ◽  
Major Gene Effect ◽  
Feed Utilisation ◽  
Relationship Of ◽  
The Relationship

The Cambridge breed has been developed since 1964, based on a foundation group of 54 ewes representing 11 breeds mated initially to seven Finnsheep rams. Data presented show that a high litter size(LS) has been established (mean 2.8 in 3 year old ewes) by a policy of selection coupled with minimising generation interval. Observations on ovulation rate (OR)show a large range (1—13) and are consistent with an hypothesis that OR is influenced by a major gene effect superimposed on a basal level of about 2.5 ova. The gene appears to increase ovulation by about two ova per copy and to have a frequency approaching 0.3 in the Bangor University flock. Data on the relationship of LS at birth and of lambs weaned per ewe are presented which indicate that under ideal conditions the optima for OR and LS at birth cannot exceed 5 and 3.5 respectively for mature ewes. The practical utilisation of the breed as a dam-line sire of crossbred ewes show that the Cambridge crossbreds are more precocious, more prolific, have slower growing lambs with carcasses of similar quality to the corresponding Border Leicester crosses. Overall superiority inefficiency of feed utilisation is about 20 %. Methods of genotyping sheep and utilising the major gene in practice are discussed.

Detection of a major gene for litter size in Thoka Cheviot sheep using Bayesian segregation analyses

2002 ◽  
Vol 75 (3) ◽  
pp. 339-347 ◽  
Author(s):  
G. A. Walling ◽  
S. C. Bishop ◽  
R. Pong-Wong ◽  
G. Gittus ◽  
A.J. F. Russel ◽  
...  
Keyword(s):  
Litter Size ◽  
Variance Components ◽  
Fixed Effects ◽  
Major Gene ◽  
Single Copy ◽  
Threshold Analysis ◽  
Data Set ◽  
Gene Effect ◽  
Inverse Gamma ◽  
Major Gene Effect

AbstractSegregation analyses were applied to data from an experimental sheep flock to investigate the presence of a major gene affecting litter size. The data set contained 14 years of litter size data, with up to five parities per ewe, from Cheviot sheep carrying the putative Thoka fecundity gene from Icelandic sheep. Segregation analyses were performed using a Markov chain Monte Carlo method implemented using Gibbs sampling. Uniform priors were initially used for estimating variance components, the gene effect and fixed effects in the data. Genotypes in the base generation were assumed known based on the use of the imported Icelandic donor semen from the founder rams. The use of alternative priors (naïve and inverse-gamma distributions) for the variance components did not significantly affect the results, demonstrating the data to be sufficiently powerful for the analyses used. Segregation analyses detected a major gene for litter size in the Thoka Cheviot flock increasing litter size by 0·70 lambs per ewe lambing for a single copy of the gene. When the analysis was repeated without fixing the genotypes in the base population, the analyses predicted a different genotype than that previously used for one of the founder rams and suggested the major gene to be segregating in the Cheviot founder animals prior to the introduction of the Thoka rams. A liability threshold analysis was also applied to the data. As identified in other studies, the threshold analysis overestimated the heritability, but the estimated major gene effect was not significantly different from other analyses. The results confirm the segregation of the Thoka gene in a Cheviot flock and highlight the statistical method as a useful tool for identifying carrier animals to be used for future matings.

scholarly journals A Major Gene Effect Controls Resistance to Caries

2011 ◽  
Vol 90 (6) ◽  
pp. 735-739 ◽  
Author(s):  
R.I. Werneck ◽  
F.P. Lázaro ◽  
A. Cobat ◽  
A.V. Grant ◽  
M.B. Xavier ◽  
...  
Keyword(s):  
Major Gene ◽  
Gene Effect ◽  
Major Gene Effect

Segregation analysis of idiopathic scoliosis: Demonstration of a major gene effect

1999 ◽  
Vol 86 (4) ◽  
pp. 389-394 ◽  
Author(s):  
T.I. Axenovich ◽  
A.M. Zaidman ◽  
I.V. Zorkoltseva ◽  
I.L. Tregubova ◽  
P.M. Borodin
Keyword(s):  
Idiopathic Scoliosis ◽  
Segregation Analysis ◽  
Major Gene ◽  
Gene Effect ◽  
Major Gene Effect

scholarly journals Variation in ovulation rate and litter size

1988 ◽  
Vol 60 (6) ◽  
pp. 602-602
Author(s):  
G. E. Bradford ◽  
Y. M. Berger
Keyword(s):  
Litter Size ◽  
Production Systems ◽  
Major Gene ◽  
Ovulation Rate ◽  
Intensive Management ◽  
Coefficients Of Variation ◽  
Sheep Production

An increase in mean prolificacy is a goal for many sheep production systems, but it is also desirable that variation be minimized around the optimum value. Lambs born in litters of 3 or 4 can be reared with intensive management, but at higher input costs than for twins. Thus for a mean litter size (LS) goal of 2.0, producers desire the maximum possible proportion of twins with as few singles and litters of 3 or more as possible. Coefficients of variation for ovulation rate (OR) range from about 22 % for Romanov to about 40 % for Booroola Merinos; breed CV’s for LS vary less. The most uniform LS’s are achieved by populations with a uniform OR and high prenatal survival. Variability in Booroola populations results in part from segregation of a gene with large effect on OR, but variation is high within genotypes (FF or F+). Among breeds where high prolificacy appears to be inherited quantitatively, there are differences in variability, with Romanov quite uniform, Finnsheep intermediate, and D’Man more variable. The possibility of a gene with large effect in the D’Man breed, in addition to many favorable quantitative genes for prolificacy, has not been ruled out. In general, these three breeds (and some others) transmit their prolificacy additively, making it possible to choose a wider range of mean prolificacy values by crossing and backcrossing with such breeds than by use of a major gene such as the Booroola. Data on variability of first and later generation crossbreds between non-prolific and different prolific breeds are now available.

The relationship between age at first effective service and numbers born in the gilt litter in purebred pigs

1987 ◽  
Vol 1987 ◽  
pp. 101-101
Author(s):  
J.T. Mercer
Keyword(s):  
Standard Deviation ◽  
Litter Size ◽  
Management System ◽  
Ovulation Rate ◽  
Reproductive Parameters ◽  
Large White ◽  
The Relationship ◽  
Effective Service

Practical use is made of an increase in the ovulation rate of gilts over the first few oestrous cycles. In large herds it may well be easier to increase the interval between entry into the herd and first service in order to improve the size of the first litter. The present study considers existing herd records, taken from the Easicare management system, in which the relationship between age at first litter and reproductive parameters in the first parity are examined. A total of 3778 gilt litters were involved, mostly Large White or Landrace, from 14 nucleus or multiplication herds. Average age at first litter ranged from 342 to 376 days across herds and total numbers born per litter from 9.03 to 11.27. Within herd variation in age at first service ranged from a standard deviation of 19 days to 40 days, that of litter size being more consistent, ranging from 2.45 to 3.21. The within herd regressions between these traits were generally small, averaging 0.007 piglets per day, and insignificant (p>0.05).

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