EFFECT OF SELECTION FOR LEAN GROWTH RATE UPON FEED UTILIZATION BY THE MARKET HOG

Results from an individual feeding trial comparing the feedlot and carcass performance of pigs from two populations, an index selected line and a genetic control, are described. The populations were initiated in 1961, the select line restructured in 1972, and the present evaluation made on progeny born in 1976. The index was based on two traits, growth rate and backfat. Feedlot data for 123 pigs indicated a direct genetic response of.94 standard deviation units (SDU) for rate of feedlot gain and correlated responses of −1.07 SDU for days on test, −1.22 SDU for total feed required and −1.07 SDU for feed/gain ratio. Carcass data for 96 pigs indicated a direct genetic response of −1.51 SDU for average backfat and a correlated response of 1.21 SDU for carcass index. In economic terms (1976 values), the improvement in carcass merit represented an increased revenue of $3.04 per pig, the increased growth rate was equivalent to a 10% reduction in the fixed costs and non-feed variable costs per pig, and the correlated response in feed requirements reduced feed costs by $3.13 per pig. Practical implications in respect of pig testing programs are discussed.

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Selection for components of efficient lean growth rate in pigs 2. Selection pressure applied and direct responses in a Landrace herd

Animal Science ◽

10.1017/s0003356100007753 ◽

1994 ◽

Vol 59 (2) ◽

pp. 263-269 ◽

Cited By ~ 9

Author(s):

N. D. Cameron ◽

M. K. Curran

Keyword(s):

Growth Rate ◽

Genetic Correlations ◽

Correlated Response ◽

Selection Line ◽

Control Line ◽

Direct Response ◽

Lean Growth ◽

Ad Libitum ◽

Selection For ◽

Ad Libitum Feeding

AbstractResponses to divergent selection for lean growth rate with ad-libitum feeding (LGA), for lean food conversion (LFC) and for daily food intake (DFI) in Landrace pigs were studied. Selection was practised for four generations with a generation interval ofl year. A total of 2642 pigs were performance tested in the high, low and control lines, with an average of 37 boars and 39 gilts performance tested per selection line in each generation. The average within-line inbreeding coefficient at generation four was equal to 0·04. There was one control line for the DFI and LFC selection groups and another control line for the LGA selection group. Animals were performance tested in individual pens with mean starting and finishing weights of 30 kg and 85 kg respectively with ad-libitum feeding. The selection criteria had phenotypic s.d. of 32, 29 and 274 units, for LGA, LFC and DFI, respectively, and results are presented in phenotypic s.d.Cumulative selection differentials (CSD) were 5·1, 4·5 and 5·5 phenotypic s.d. for LGA, LFC and DFI, respectively. Direct responses to selection were 1·4,1·1 and 0·9 (s.e. 0·20) for LGA, LFC and DFI. In each of the three selection groups, the CSD and direct responses to selection were symmetric about the control lines. The correlated response in LFC (1·1, s.e. 0·19) with selection on LGA was equal to the direct response in LFC. In contrast, the direct response in LGA was greater than the correlated response (0·7, s.e. 0·18) with selection on LFC. There was a negative correlated response in DFI (-0·6, s.e. 0·18) with selection on LFC, but the response with selection on LGA was not significant (0·2, s.e. 0·16).Heritabilities for LGA, LFC and DFI ivere 0·25, 0·25 and 0·18 (s.e. 0·03), when estimated by residual maximum likelihood, with common environmental effects of 0·12 (s.e. 0·02). Genetic correlations for LFC with LGA and DFI were respectively positive (0·87, s.e. 0·02) and negative (-0·36, s.e. 0·09), while the genetic correlation between DFI and LGA was not statistically different from zero, 0·13 (s.e. 0·10). Selection on components of efficient lean growth has identified LGA as an effective selection objective for improving both LGA and LFC, without a reduction in DFI.

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Selection for lean growth rate and correlated responses in litter traits in a synthetic line of Yorkshire-Meishan pigs

Canadian Journal of Animal Science ◽

10.4141/a00-082 ◽

2001 ◽

Vol 81 (2) ◽

pp. 205-214 ◽

Cited By ~ 6

Author(s):

P. Chen ◽

T. J. Baas ◽

J. C. M. Dekkers ◽

L. L. Christian

Keyword(s):

Growth Rate ◽

Regression Coefficients ◽

Correlated Response ◽

Selection Line ◽

Control Line ◽

Correlated Responses ◽

Lean Growth ◽

Litter Traits ◽

Selection For ◽

Synthetic Line

Selection for lean growth rate (LGR) was conducted for four generations in a synthetic line of Yorkshire-Meishan pigs to study the effectiveness of selection for LGR and correlated responses in litter traits. Lean growth rate was estimated from ultrasound measurements of 10th-rib backfat thickness and longissimus muscle area. In the selection line, 7 boars and 20 gilts with the highest LGR were selected to produce the next generation. The generation interval was 13 mo and the average selection differential per generation was 1.1 phenotypic standard deviation units. A contemporaneous control line was maintained by randomly selecting 5 boars and 15 gilts. Data from a total of 1057 pigs sired by 58 boars and out of 133 sows were available from the two lines. Selection responses were estimated from deviations of the selection line from the control line using least squares (LS) and by multiple trait derivative-free restricted maximum likelihood analysis using an animal model (AM). The estimate of response to selection per generation using LS was 9.4 ± 0.95 g d–1 for LGR. The corresponding estimate from the AM was 9.8 ± 0.51 g d–1. Correlated responses in litter traits were regressed on generation. For the LS method, regression coefficients were negative but not significant (P > 0.05) for total number born, number born alive, and number at 21 d and at 42 d. Significant, positive correlated responses occurred in 42-d litter weight and 21-d piglet weight (P < 0.05). For the AM method, the regression coefficients were also negative, but were not significant (P > 0.05) for numberalive at birth, at 21 d, and at 42 d. A significant positive correlated response occurred only for 42-d litter weight (P < 0.05). Although results are based on a population of limited size, it can be concluded that selection for LGR in a synthetic line is effective and should have little effect on litter traits. Key words: Pigs, selection, lean growth rate, correlated response

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Genetic parameters and predicted response to selection for lean growth in an Australian commercial nucleus pig herd

Australian Journal of Agricultural Research ◽

10.1071/ar99127 ◽

2000 ◽

Vol 51 (7) ◽

pp. 833 ◽

Cited By ~ 2

Author(s):

Nguyen Hong Nguyen ◽

Cam P. McPhee ◽

Claire M. Wade ◽

Brian G. Luxford

Keyword(s):

Growth Rate ◽

Genetic Parameters ◽

Average Daily Gain ◽

Genetic Correlations ◽

Genetic Response ◽

Lean Growth ◽

Derivative Free ◽

Total Data ◽

Selection For ◽

Daily Gain

Genetic parameters for performance traits in a pig population were estimated using a multi-trait derivative-free REML algorithm. The 2590 total data included 922 restrictively fed male and 1668 ad libitum fed female records. Estimates of heritability (standard error in parentheses) were 0.25 (0.03), 0.15 (0.03), and 0.30 (0.05) for lifetime daily gain, test daily gain, and P2-fat depth in males, respectively; and 0.27 (0.04) and 0.38 (0.05) for average daily gain and P2-fat depth in females, respectively. The genetic correlation between P2-fat depth and test daily gain in males was –0.17 (0.06) and between P2-fat and lifetime average daily gain in females 0.44 (0.09). Genetic correlations between sexes were 0.71 (0.11) for average daily gain and –0.30 (0.10) for P2-fat depth. Genetic response per standard deviation of selection on an index combining all traits was predicted at $AU120 per sow per year. Responses in daily gain and backfat were expected to be higher when using only male selection than when using only female selection. Selection for growth rate in males will improve growth rate and carcass leanness simultaneously.

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Selection for components of efficient lean growth in Landrace pigs

Proceedings of the British Society of Animal Production (1972) ◽

10.1017/s0308229600025642 ◽

1994 ◽

Vol 1994 ◽

pp. 10-10

Author(s):

M.K. Curran ◽

N.D. Cameron

Keyword(s):

Growth Rate ◽

Selection Criteria ◽

Conversion Ratio ◽

Control Line ◽

Food Conversion ◽

Lean Growth ◽

Food Conversion Ratio ◽

Daily Food ◽

Selection For ◽

One Year

To study responses to divergent selection for lean growth rate (LGA), lean food conversion ratio (LFC) and daily food intake (DFI), an experiment was started in 1984 at Edinburgh and Wye. This paper measured the selection pressure applied, the responses in the selection criteria and estimated the genetic and phenotypic relationships between the selection criteria with ad-libitum feeding of Landrace pigs after four generations of selection.The LGA (LFC) selection objective was to obtain equal correlated responses in growth rate (food conversion ratio) and carcass lean content, measured in phenotypic s.d. The LGA, LFC and DFI selection criteria had phenotypic s.d. of 32, 29 and 270 units and results are presented in s.d. units.Boars and gilts were purchased from eight British nucleus herds and boars from national artificial insemination centres in 1982. Homozygous or heterozygous halothane positive pigs were not included in the experiment. The base population consisted of 20 sires and 89 dams. Within each of the three selection groups, there were high and low selection lines with a control line, each consisting of 10 boars and 20 gilts, with a generation interval of one year. There were two control lines, one for LGA and one for LFC and DFI, as selection groups were arrowed continuously. The total number of pigs tested per line and average inbreeding coefficient at generation 4, within selection group are given below.

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Meat and eating quality responses to selection for components of efficient lean growth rate in pigs

Proceedings of the British Society of Animal Science ◽

10.1017/s030822960003230x ◽

1998 ◽

Vol 1998 ◽

pp. 17-17

Author(s):

N.D. Cameron ◽

G. Nute ◽

S. Brown ◽

J.D. Wood

Keyword(s):

Growth Rate ◽

Eating Quality ◽

Quality Traits ◽

Selection Strategies ◽

Lean Growth ◽

Selection For

Information on the responses in meat and eating quality to selection for components of lean growth rate is important to the British pig breeding industry when evaluating alternative selection strategies. The current study determined responses in meat and eating quality traits to selection for components of lean growth rate.

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Responses in gilt post-farrowing traits and pre-weaning piglet growth to divergent selection for components of efficient lean growth rate

Proceedings of the British Society of Animal Science ◽

10.1017/s0308229600029925 ◽

1996 ◽

Vol 1996 ◽

pp. 17-17

Author(s):

J. C. Kerr ◽

N. D. Cameron

Keyword(s):

Growth Rate ◽

Food Intake ◽

Fixed Time ◽

Divergent Selection ◽

Large White ◽

Lean Growth ◽

Fixed Weight ◽

Ad Libitum ◽

Selection For ◽

Piglet Growth

Responses in sow traits at farrowing and during lactation and in pre-weaning piglet growth rate were determined in a population of Large White pigs, after seven generations of divergent selection for components of efficient lean growth rate. Information on the factors influencing preweaning piglet growth rate is required for a comprehensive evaluation of alternative selection strategies.There were four selection groups: daily food intake (DFI), lean food conversion (LFC), lean growth rate (LGA) on ad-libitum feeding and lean growth rate on scale feeding (LGS). There were 242 gilts in the study, with 20 gilts in the high, low and control lines of each selection group. Pigs in the ad-libitum selection groups were performance tested over a fixed weight range of 30 to 85 kg. Pigs fed on scale feeding were performance tested for a fixed time period of 84 days from 30 kg with food intake equal to 0.75 g/g of daily ad-libitum food intake. Matings were unsupervised and took place in outside paddocks.

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Genetic and phenotypic relationships between performance test and reproduction traits in pigs selected for components of efficient lean growth rate

Proceedings of the British Society of Animal Science ◽

10.1017/s030822960002780x ◽

1995 ◽

Vol 1995 ◽

pp. 9-9

Author(s):

J. C. Kerr ◽

N. D. Cameron

Keyword(s):

Growth Rate ◽

Performance Test ◽

Divergent Selection ◽

Large White ◽

Selection Strategies ◽

Lean Growth ◽

Reproduction Traits ◽

Breeding Programmes ◽

Selection For

Genetic and phenotypic relationships between performance test and reproduction traits were estimated in a population of Large White pigs, after five generations of divergent selection for components of efficient lean growth rate. The parameters are required to evaluate alternative selection strategies in pig breeding programmes.

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Sex effects on fat hardness meter readings of market weight pigs

Canadian Journal of Animal Science ◽

10.4141/cjas95-077 ◽

1995 ◽

Vol 75 (4) ◽

pp. 509-515 ◽

Cited By ~ 12

Author(s):

A. P. Sather ◽

S. D. M. Jones ◽

W. M. Robertson ◽

Sophie Zawadski

Keyword(s):

Growth Rate ◽

Growth Rate Constant ◽

Quadratic Term ◽

Cross Sectional ◽

Linear Interaction ◽

Fat Quality ◽

Lean Growth ◽

Fat Thickness ◽

Selection For ◽

Sectional Surface

A portable fat hardness meter (FHM) was used to measure the firmness of the inner fat layer on a cross sectional surface over the second thoracic vertebra of pork carcasses. This was a 4-yr study with data collected on 141 barrows, 214 gilts and 270 boars. A statistical model, after adjusting for year and breed of sire (i.e., Lacombe, Landrace, Yorkshire), included sex, linear and quadratic covariates for carcass growth rate (i.e., carcass weight per day of age), a linear covariate for leanness (i.e., carcass fat thickness or dissectible lean) within sex, and a linear by linear covariate of growth rate by leanness, and was used to describe a response surface with fat hardness. No pigs in this study had extremely soft fat (i.e., FHM < 420). However, 4, 2 and 0% of the boars, gilts and barrows had very soft fat (i.e., FHM 420–619). While 10% of the barrows had extremely hard (i.e., FHM > 970) or very hard fat (i.e., FHM 930–970), only 1% of the gilts had very hard fat, and no boars were included in these classes. Relative to the FHM readings of gilts (i.e., 805 ± 6.2), boars (i.e., 780 ± 5.6) had softer fat (P = 0.0002) while barrows (i.e., 835 ± 7.4) had harder fat (P = 0.0001). The majority of boars had slightly soft fat (i.e., FHM 750–829) while gilts and barrows had slightly hard (i.e., FHM 830–889) fat. Regression coefficients for growth rate on fat hardness were homogeneous among the sexes. As growth rate increased fat hardness increased, but was attenuated by a negative quadratic term. Increased leanness was linearly antagonistically related with fat hardness. There were differential effects across sexes (P = 0.0261). As leanness increased, fat became softer among boars and gilts compared with barrows. A linear by linear interaction of growth rate with leanness attenuated this effect. Holding growth rate constant, a 25% reduction of carcass fatness would be expected to reduce fat hardness by 40, 35 and 20 points in boars, gilts, and barrows, respectively. While selection for increased lean growth may result in some degradation in fat quality, the trend towards marketing heavy pigs as they become leaner should be sufficient to offset this effect. Key words: Swine, carcass, grading, growth rate, fat, lean

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LIVE PERFORMANCE AND CARCASS CHARACTERISTICS OF BEEF BULLS IN RELATION TO SELECTION FOR YEARLING WEIGHT

Canadian Journal of Animal Science ◽

10.4141/cjas70-068 ◽

1970 ◽

Vol 50 (3) ◽

pp. 491-497 ◽

Cited By ~ 2

Author(s):

A. H. MARTIN ◽

H. T. FREDEEN ◽

J. A. NEWMAN

Keyword(s):

Growth Rate ◽

Live Weight ◽

Direct Selection ◽

Control Line ◽

Live Performance ◽

Carcass Yield ◽

Yield And Quality ◽

Lean Growth ◽

Kidney Fat ◽

Selection For

Data over two years on a total of 149 Shorthorn bulls from a closed herd under direct selection for yearling weight were used to examine line differences in carcass yield and quality and to evaluate relationships between live performance and carcass yield and quality. No significant differences [Formula: see text] in performance or carcass data between control and selected lines were apparent in 1967. However, in 1968 bulls from the selected line were heavier at slaughter (470.5 kg vs. 441.8 kg), their carcasses contained more kidney fat (9.14 kg vs. 8.46 kg), and they had larger loin eye area but smaller weight-adjusted loin eye area. Rate of gain was superior for the selected line whether examined as live-weight, carcass weight, trimmed primal cut weight or lean weight per day of age. There were no significant differences between lines for percent fat, lean or bone in primal cuts, or for rib fat thickness, percent trimmed prime cuts, percent seam fat, muscle/bone and hind/front ratios, or for chemical composition or tenderness evaluations of the longissimus dorsi. Averaged over the two years and at the same averaged slaughter weights (418 days), selected-line bulls produced a significantly greater quantity of total carcass, of trimmed primal cuts and of total lean than did the control-line bulls; selection for yearling weight appeared to have been effective in increasing rate of lean growth. Phenotypic correlations indicated that liveweight/day of age was more highly related to variation in lean growth rate than growth rate of fat. From 20 to 60% of the variation in wholesale cut weights was associated with differences in rate of gain. Distribution of the gains was little influenced by rate of gain. Tenderness evaluations were not related to live performance.

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