Terminal Sire Line Research Articles

Crossbreeding parameters for growth and feed consumption traits from a five diallel mating scheme in rabbits1

Twenty-five genetic groups of young rabbits originated from a diallel-crossbreeding scheme among 5 selected lines: 3 maternal and 2 terminal sire lines belonging to 2 Spanish research institutions. A sample of 2,773 young rabbits from 525 litters was controlled during the fattening period lasting from 5 to 9 wk. Growth and feed consumption traits were evaluated throughout different biweekly batches. A Bayesian approach was used for inference from an animal model with common litter effects. On average, genetic groups coming from lines selected for growth rate were heavier (+58.9 g at 32 d and +315.5 g at 60 d), had greater growth rate (9.24 and 8.15 g/d from individual or cage analysis, respectively) and feed intake (+13.24 g/d), and showed better feed conversion ratio (-0.21 g of intake/g of gain), than the genetic groups originated from crosses among lines selected for litter size. Crossbreeding parameters were estimated from the samples of the marginal posterior distribution of the genetic group effect according to the Dickerson model. Maternal genetic and individual heterosis effects were null or very low. Direct genetic effects mainly regulated the expression of growth traits.

Genetic and phenotypic variation in reproductive traits of AI boars

The primary objective of this paper is to review our current understanding of phenotypic variation in reproductive traits of AI boars. The proportion of boars that cannot be trained for collection in commercial studs is low and differences among genetic lines are small. In contrast, there is a considerable variation in sperm production and significant differences are present among genotypes. The general pattern is for sperm numbers to increase rapidly between 9 and 13 months of age and then gradually reach a plateau. This initial period of enhanced production occurs over a longer period in some genetic lines, resulting in differences of 30 × 10 9 sperm cells or more per ejaculate. There also are genetic lines of boars that seem to have a high “heat tolerance”. Decreases in sperm production during periods of high environmental temperatures average 5–7% in these lines, compared with 15–20% in others. Finally, there are boars currently being used in the industry that are capable of producing exceptional fertility results with low numbers of sperm. Unfortunately, several breeding practices common to swine AI make their routine identification difficult. Based on the phenotypic variation observed in modern terminal sire lines of AI boars, current prospects for influencing sperm production, boar fertility, and mounting behaviours through genetic selection are viewed as being good, moderate to low, and poor, respectively.

Letter to the Editor

I have read with interest the editorial by David S. Buchanan and Lawrence P. Reynolds (84:1307, 2006), and the letter to the editor by James R. Males and Michael L. Galyean (84:1308, 2006), regarding the matters of alleged scientific misconduct or erroneous reporting associated with papers concerning work previously published in the Journal of Animal Science concerning the National Pork Producers Council (NPPC) Terminal Sire Line Genetic Evaluation Program and Maternal Line Genetic Evaluation Program. In reference to 2 papers that rely on data from the NPPC-sponsored Maternal Line Genetic Evaluation Program (82:41–53, 2004 and 84:2590–2595, 2006), I call upon the authors and co-authors to publish corrected data. Before reading these published articles, I had worked hard to bring to light the truth regarding data that I believe was incorrectly represented in the initial NPPC reports and subsequent papers. Concerning your editorial and letter, I would like to call attention to 2 specific obligations that I believe we have as scientists, and then discuss the data that I have already presented to you and others.

Influence of sex and terminal sire line on performance and carcass and meat quality of Iberian pigs reared under intensive production systems

A trial was conducted to study the effects of sex (castrated males; females) and terminal sire line (DD, Danish Duroc; SD, Spanish Duroc; RIB, Retinto Iberian) on performance and carcass and meat quality of pigs slaughtered at 145 kg body weight. The female line was pure Iberian in all cases. Each treatment was replicated five times (six pigs). Females were more efficient, had less carcass and inter- and intramuscular fat and more trimmed primal cuts yield than castrated males. Duroc sired pigs grew faster and had better feed conversion and carcass quality than RIB sired pigs. Crossbreeds from SD had less carcass yield than crossbreeds from DD or RIB. We conclude that productive performance and primal cuts yield were higher for females than for castrated males. Danish Duroc sires are an alternative to Spanish Duroc and Retinto Iberian sires for production of heavy pigs destined for the dry cured industry.

Marker-assisted selection for commercial crossbred performance1

Several studies have shown that selection of purebreds for increased performance of their crossbred descendants under field conditions is hampered by low genetic correlations between purebred and commercial crossbred (CC) performance. Although this can be addressed by including phenotypic data from CC relatives for selection of purebreds through combined crossbred and purebred selection (CCPS), this also increases rates of inbreeding and requires comprehensive systems for collection of phenotypic data and pedigrees at the CC level. This study shows that both these limitations can be overcome with marker-assisted selection (MAS) by using estimates of the effects of markers on CC performance. To evaluate the potential benefits of CC-MAS, a model to incorporate marker information in selection strategies was developed based on selection index theory, which allows prediction of responses and rates of inbreeding by using standard deterministic selection theory. Assuming a genetic correlation between purebred and CC performance of 0.7 for a breeding program representing a terminal sire line in pigs, CC-MAS was shown to substantially increase rates of response and reduce rates of inbreeding compared with purebred selection and CCPS, with 60 CC half sibs available for each purebred selection candidate. When the accuracy of marker-based EBV was 0.6, CC-MAS resulted in 34 and 10% greater responses in CC performance than purebred selection and CCPS. Corresponding rates of inbreeding were 1.4% per generation for CC-MAS, compared with 2.1% for purebred selection and 3.0% for CCPS. For marker-based EBV with an accuracy of 0.9, CC-MAS resulted in 75 and 43% greater responses than purebred selection and CCPS, and further reduced rates of inbreeding to 1.0% per generation. Selection on marker-based EBV derived from purebred phenotypes resulted in substantially less response in CC performance than in CC-MAS. In conclusion, effective use of MAS requires estimates of the effect on CC performance, and MAS based on such estimates enables more effective selection for CC performance without the need for extensive pedigree recording and while reducing rates of inbreeding.

Characterizing linkage disequilibrium in pig populations.

Knowledge of the extent and range of linkage disequilibrium (LD), defined as non-random association of alleles at two or more loci, in animal populations is extremely valuable in localizing genes affecting quantitative traits, identifying chromosomal regions under selection, studying population history, and characterizing/managing genetic resources and diversity. Two commonly used LD measures, r(2) and D', and their permutation based adjustments, were evaluated using genotypes of more than 6,000 pigs from six commercial lines (two terminal sire lines and four maternal lines) at ~4,500 autosomal SNPs (single nucleotide polymorphisms). The results indicated that permutation only partially removed the dependency of D' on allele frequency and that r(2) is a considerably more robust LD measure. The maximum r(2) was derived as a function of allele frequency. Using the same genotype dataset, the extent of LD in these pig populations was estimated for all possible syntenic SNP pairs using r(2) and the ratio of r(2) over its theoretical maximum. As expected, the extent of LD highest for SNP pairs was found in tightest linkage and decreased as their map distance increased. The level of LD found in these pig populations appears to be lower than previously implied in several other studies using microsatellite genotype data. For all pairs of SNPs approximately 3 centiMorgan (cM) apart, the average r(2) was equal to 0.1. Based on the average population-wise LD found in these six commercial pig lines, we recommend a spacing of 0.1 to 1 cM for a whole genome association study in pig populations.

Impact of genetic selection on management of boar replacement

Boars in an artificial insemination centre have been selected for their superior genetic potential, with ‘superior’ being defined as having traits the customer wants transmitted to his herd. The ability to meet the customers’ needs depends on the heritability of the trait, the geneticist's success in devising a selection scheme for the trait in balance with other economically important traits, and the boar's ability to produce sperm that can fertilise oocytes. Genetic evaluation research over the past 20 years has greatly increased the number of traits for which a boar can be selected: currently in the Canadian national program, these include age at 100 kg, backfat at 100 kg, feed efficiency, lean yield and litter size. In the near future, traits that are very likely to be added to this selection list include piglet survival, marbling, loin eye area and structure traits. In Canada, sires are ranked on two estimated breeding value (EBV) indices; one, focused on development of terminal sire lines, is based on the growth and yield traits and another, primarily focused on maternal line development, de-emphasises these traits and incorporates litter size. Boars that are in Canadian AI centres because of their excellent growth traits are typically in the top 5–10% of the national population for terminal sire line index, but they may be only average or substandard for litter size. Conversely, boars selected to be in the top 5–10% for conveying such reproductive traits as litter size may only be in the top 33% for growth traits. The more offspring from a superior boar in either of these indices, the faster the population average for the trait improves. The original sire gets knocked out of the elite group, is culled and replaced by a higher ranked young boar from the now improved general population. Although genetic superiority should govern an AI centre's selection and culling of boars, decision-making in real life is seldom that simple. Selection criteria may be contradictory as above, or a boar with truly superior traits may be excluded because a newly-developed molecular genetics test determines he carries an undesirable gene such as PSS, RN or others being developed. Selection for terminal sire or maternal line traits can ignore important practical factors that affect an AI centre—boars with superior genetics may not produce good semen because skeletal or penile problems prevent ejaculation, or because sperm production is poor due to a genetic flaw, disease, or some other cause. Interestingly, selection pressure for one trait may inadvertently select for a trait that is linked but whose linkage is unrecognised, and such unintentionally selected genes could benefit, harm, or have no effect on production traits. An AI centre serving a variety of customers must select boars in anticipation of their customers’ needs (including new, foreign and niche markets). A centre should also review its genetic evaluation results and progeny records, both to critique its own selection success and to try to detect unexpected linkages. Finally, an AI centre needs to predict its own future, selecting not just for production traits for the swine producer, but also for factors that enhance the centre's efficiency including boar conformation and temperament, and sperm quantity, quality and hardiness. Can we select for efficiency? Our colleagues in dairy cattle AI evaluate bull performance—should the swine industry consider evaluation of male fertility traits?

Design and standards for genetic evaluation of swine seedstock populations.

The purpose of this article is to describe a program for evaluation of seedstock populations in the swine industry. Differences among seedstock populations for economically important traits must be identified in order for pork producers to efficiently use available genetic resources. National genetic evaluation programs have the potential to identify the important differences among populations and to increase the rate of genetic improvement in a population. Program results provide performance benchmarks that stimulate testing and selection procedures by seedstock suppliers that further increase the rate of genetic improvement. A Terminal Sire Line Genetic Evaluation Program was designed and conducted in the United States by the National Pork Producers Council (Des Moines, IA) to compare seedstock populations for use in crossbreeding systems. High levels of statistical accuracy for program results were established; the ability to detect differences of 0.25 SD per trait, a power of test of 75%, and a 5% significance level were selected. Pure breeds and breeding company sire lines were nominated for the program. Semen was collected from nominated boars and distributed to cooperating commercial producers during eight 1-wk breeding periods. Pigs were produced in 136 commercial herds and transported to testing facilities at 8 to 23 d of age. Nine of the 11 sire lines originally entered in the program completed the sampling requirements for statistical analysis. High levels of statistical accuracy and a large, representative sample of boars with restrictions on genetic relationships ensured that the program results included unbiased, highly accurate sire line data for growth, carcass, meat quality, and eating quality traits of economic importance. This program has shown commercial producers that they have several choices of sire lines for changing their crossbreeding programs in desired trait areas. Commercial product evaluation must be an ongoing process, and this program serves as a model for future testing and evaluation of diverse genetic seedstock populations.

Feeding patterns, growth performance and carcass traits in group-housed growing-finishing pigs: the effect of terminal sire line, halothane genotype and age

AbstractThe effects of terminal sire line, halothane genotype and age on feeding patterns and growth performance were studied in 208 castrated growing-finishing pigs distributed in two batches. In batch 1 (no. = 130), pigs came from crosses of NN Landrace × Large White sows with a Pietrain Nn (Pi-Nn) or a Large White × Pietrain Nn terminal sire line (LwPi-Nn). In batch 2 (no. = 78), the same sows were used but crossed with three different terminal sire lines : a Pietrain nn (Pi-nn), and two Pietrain NN (Pi-NNa and Pi-NNb). Growth performance and feeding patterns of the progeny (Nn or NN for the halothane gene) were measured from 67 to 166 days of age. Pigs were housed in groups of 10 and 13 individuals in Batch 1 and 2, respectively, with a random mixed-breed and halothane genotype sample in each group (space allowance 1·3 m2 per pig and 1·1 m2 per pig, respectively). Feeding patterns were monitored with a computerized food intake recording system (IVOG®-station) and every 3 weeks pigs were weighed and backfat and loin-muscle depth were ultrasonically recorded (PIGLOG®). Carcass quality was assessed with the Fat-o-Meater grading probe. In batch 1, halothane genotype did not have a significant effect on any of the feeding patterns recorded, but Nn individuals had a significantly higher body weight (P <0·05), loin-muscle depth (P <0·05) and lower backfat thickness (P <0·01) in the last measurement taken, 3/4 carcass loin depth (P <0·05) and lower carcass last rib backfat (P <0·05) than NN pigs. Terminal sire line had a significant effect on all feeding patterns recorded except for feeding rate, Pi-Nn sired pigs showing a significantly higher food intake per visit (P <0·05) and feeder occupation time per visit (P <0·05) and lower number of visits (P <0·001) compared with LwPi-Nn sired pigs which, in turn, showed significantly higher food intake per day (P <0·001) and feeder occupation time per day (P <0·01). Terminal sire also affected growth performance and body composition, Pi-Nn sired pigs having a significantly lower body weight (P <0·001) and backfat thickness (P <0·001) but higher killing-out proportion and 3/4 loin depth (P <0·01) than LwPi-Nn sired pigs. In batch 2, Pi-NNb sired pigs showed a significantly lower food intake per day compared with the progeny of the other two terminal sires lines at some of the age measurements taken (P <0·05). The rest of the feeding patterns was not affected by terminal sire line. Body and carcass weights were also significantly lower (P <0·01) for Pi-NNb sired pigs, but their killing-out proportion was higher than Pi-NNa sired pigs. With regard to these variables, Pi-nn sired pigs held an intermediate position between the two NN terminal sire lines. In both batches, age was associated with a significant increase in food intake per visit and per day and feeding rate (P <0·001) and a decrease in feeder occupation time per visit and per day and frequency of visits to the feeder (P <0·001). Overall, the present results suggest differences between terminal sire lines for feeding patterns and confirm their evolution with age from short and frequent meals to long and larger ones in growing-finishing pigs. Under our conditions, the effects of terminal sire line on feeding patterns and growth performance surpassed those of the halothane genotype.

Effect of gender, terminal sire line and age at slaughter on performance, carcass characteristics and meat quality of heavy pigs

AbstractTwo hundred and forty pigs of 56 ± 3 days of age were used to investigate the effects of sex (barrows; gilts), boar sire (DD, Danish Duroc; ND × LW, Dutch Duroc × Large White ; P × LW, Pietrain × Large White) and slaughter age (160; 175 days) on performance and carcass and meat quality. Treatments were arranged factorially (2 × 3 × 2) and there were four replicates (five pigs per replicate) per treatment. The female line was Landrace × Large White in all cases. Barrows had greater daily food intake (P <0·001) and average daily gain (P <0·01) and had poorer food conversion ratio (P <0·001) than gilts. Carcasses from castrates were fatter and had a lower yield of trimmed lean cuts than carcasses from females (P <0·001). Longissimus muscle from barrows had more intramuscular fat and higher a* value than muscle from gilts (P <0·05). Pigs from DD sire line grew faster (P <0·05) and had a better food conversion ratio (P <0·001) than pigs from the other two lines. Dressing proportion and backfat thickness were greatest for P × LW sired pigs (P <0·01) and proportion of trimmed lean cuts was greater for DD and P × LW than for ND × LW sired pigs (P <0·01). Longissimus muscle from DD sired pigs had less protein (P <0·01) and more intramuscular fat (P <0·001) than muscle from the remaining lines. Longissimus muscle from P × LW line had more intense colour than muscle from DD and ND × LW lines (P <0·01). Pigs slaughtered at 175 days had poorer food conversion ratio (P <0·01) and less trimmed primal cut proportion (P <0·001) than pigs slaughtered at 160 days. Also, increasing the age at slaughter increased intramuscular fat content (P <0·01), a* value (P <0·001) and colour intensity of the muscle (P <0·01). Danish Duroc boars are a good alternative to ND × LW or P × LW boars for production of heavy pigs whether the crossbreds are sacrificed at 160 or 175 days. Also, an increase in age at slaughter impairs growth efficiency and yield of lean cuts but improves some aspects of meat quality, which might be of interest in the production of heavy pigs destined for the dry-cured product industry.

Genetic and economic evaluation of genetic improvement schemes in pigs. – II. Comparison of selection strategies in a three-way crossbreeding scheme

Abstract. Alternative selection strategies for a three-way cross in pigs (Pietrain as the sire line and Large White boars mated to German Landrace sows to produce the F1-female) are investigated to maximise both genetic gain and profit. The number of nucleus sows in the main female line (German Landrace) can vary within a wide range without noticeable effect on the genetic and economic response. Productive lifetimes of approximately one year are recommended for nucleus boars and sows after the progeny test. Boars mated to produce crossbreds should be used longer, especially in the terminal sire line. F1-sows can have a productive lifetime of more than two years and can be used close to their biological maximum. Four testing schemes are compared and the contribution of the three breeds to the return is evaluated. Testing crossbred animals at a central test Station cannot be recommended. This capacity should be used to test purebred animals. Both monetary genetic gain and profit are higher in a scheme with a self-performance testing of boars at Station, in comparison to a scheme with only progeny testing at Station, by 36 and 68%, respectively. Due to a reduced generation interval, using boars to produce breeding boars straight after their self-performance test leads to a further increase of monetary genetic gain by 5% and profit by 13%. In all schemes, selection in Pietrain leads to the highest return due to the highest gene proportion in and its shorter distance to the terminal product and the therefore faster transfer of genetic gain.

An evaluation of a terminal sire line for feedlot performance, carcass composition, and meat quality

Three QM Hamline™ (HL; National Pig Development, Canada), four pure-bred Landrace (LR) and Large White (LW) sires were bred to 12, 18 and 8 Manor Hybrid™ (National Pig Development, Canada) sows, respectively, which provided 37 NN-, and 37 Nn- HL, 39 NN- and 37 Nn- LR and 34 NN- LW commercial pigs for a study on the effect of breed of sire and genotype at the halothane locus on pig performance, carcass yield and meat quality. Four pigs per pen, within breed of sire and genotype, were placed on performance test at 56 d of age until total pen weight was 440 kg. Large White, LR and HL NN-pigs were slaughtered at 178, 172 and 177 d of age, adjusted to 110 kg, while LR and HL Nn-pigs were slaughtered at 177 and 178 d of age. HL pigs had 12.7 mm backfat and 44.5 mm of muscle depth at the grade site, while LW and LR had greater backfat thickness (15.1 and 15.7 mm), and less muscle depth (41.1 and 38.7 mm). The halothane genotype did not affect live animal measurements. Feed utilisation was similar in all five groups of pigs. Lean yield of the HL NN-pigs (58.8%) was greater than that found in the NN-LW (56.6%) and NN-LR (56.8%) while the halothane gene made only modest improvement in lean yield in the leaner HL (P = 0.0789) and a more substantial improvement was observed in the fatter LR (P = 0.0161). Total dissected lean was 613, 596, and 639 g kg−1 in LW, LR and HL NN-pigs, respectively, while this increased to 611 and 649 g kg−1 in LR and HL Nn-pigs. QM Hamline™ NN-pigs had larger commercial hams (9878 g) compared with NN-LW and NN-LR sired pigs. Furthermore, they also had greater lean yield in all four lean cuts. The halothane gene had no consistent effect on carcass merit. While initial pH was similar (6.03–6.04) in the three NN-groups of pigs, it dropped to 5.73 and 5.84, among the Nn-LR and HL pigs. Luminosity (59.2%, 58.7%) and hue angle (31.1°, 30.5°) of Nn-LR and HL were higher, with greater drip (5.8%, 5.3%) losses and lower soluble protein (130, 148 g kg−1), compared with NN-LR (54.8%, 24.4°, 3.0%, 185 g kg−1) and HL (55.3%, 26.1°, 3.4%, 182 g kg−1) pigs, respectively. This study indicates carcass merit can be substantially improved without use of the halothane gene and without serious effects to meat quality. However, introduction of the halothane gene can seriously compromise meat quality. Key words: Large White, Landrace, Hamline, halothane gene

Growth, development, and carcass composition in five genotypes of swine.

An experiment with 127 barrows representing five genotypes, 1) H x HD, 2) SYN, 3) HD x L[YD], 4) L x YD, and 5) Y x L (H = Hampshire, D = Duroc, SYN = synthetic terminal sire line, L = Landrace, and Y = Yorkshire), was conducted to evaluate growth and development of swine from 59 to 127 kg live weight. Animals were allowed ad libitum access to a pelleted finishing diet containing 18.5% CP, .95% lysine, and 10.5% fat, with an energy density of 3,594 kcal of ME/kg. Pigs were serially slaughtered at either 59, 100, 114, or 127 kg live BW. After slaughter, carcasses were chilled and backfat was measured at four locations. The right side of each carcass was fabricated into primal cuts of ham, loin, Boston Butt, picnic, and belly. Composition of each primal cut was determined by physical dissection into lean, fat, bone, and skin. Estimated allometric growth coefficients for carcass length, carcass weight, and longissimus muscle area relative to BW; carcass lean, fat, bone, and skin relative to both BW and carcass weight; and lean in each of the primal cuts relative to total carcass lean did not differ (P greater than .05) among genotypes. Relative to BW, the pooled growth coefficient(s) for carcass weight was (were) greater (P less than .001) than unity, whereas those for carcass length, longissimus muscle area, and backfat at first rib were smaller (P less than .001) than unity. Those for other backfat measurements were close to 1.00. Relative to either BW or carcass weight, the pooled coefficient(s) for fat was (were) greater (P less than .001) than unity, whereas those for lean, bone, and skin were smaller (P less than .001) than unity. Growth of lean, backfat, bone, and skin in the carcass were nearly linearly associated with increases in BW. The increase in fat weight was curvilinear as the pig grew and was accelerated in later growth stages, indicating that carcass fat percentage increased with increased BW.

Genotype and treatment biases in estimation of carcass lean of swine.

Carcasses of 181 barrows, representing five genotypes, 1) H x HD, 2) SYN, 3) HD x L[YD], 4) L x YD, and 5) Y x L (H = Hampshire, D = Duroc, SYN = synthetic terminal sire line, L = Landrace, and Y = Yorkshire), and two levels of ractopamine (RAC) treatment (0 and 20 ppm) were completely dissected and the data were used to examine genotype and treatment (RAC) biases in estimation of fat-standardized lean weight and to evaluate accuracies and precisions realized by use of equations based on variables derived from different technologies. Independent variables used to establish regression equations represented technologies of direct carcass measurements, optical probe data, TOBEC (total body electrical conductivity) readings, and dissected (DHMLN) and fat-standardized (FSHMLN) ham lean. Genotype bias existed when any equation from a single technology was used and was minimized by combining FSHMLN with one TOBEC reading, carcass length, and the probe measurement of 10th rib fat depth. Large RAC biases appeared when equations from direct carcass measurements or optical probe data were used and were minimized by an equation using either DHMLN or FSHMLN. A practical equation with relatively high R2 value and small genotype and RAC biases were developed by combining TOBEC readings with direct carcass measurements of 10th rib fat depth and warm carcass weight.

Effects of ractopamine, genotype, and growth phase on finishing performance and carcass value in swine: I. Growth performance and carcass merit

A replicated factorial experiment using 183 individually fed crossbred barrows was conducted. Pigs were fed an 18.5% CP (.95% lysine) diet with 3,594 kcal of ME/kg. The effects of five genotypes (GT): 1) Hampshire (H) x (H x Duroc [D]), 2) synthetic terminal sire line, 3) (H x D) x (Landrace [L] x [Yorkshire (Y) x D]), 4) L x (Y x D), and 5) Y x L; two levels of ractopamine (RAC) treatment: 0 and 20 ppm; and three treatment weight periods (WT): 1) 59 to 100, 2) 73 to 114, and 3) 86 to 127 kg live weight on growth performance and carcass traits were evaluated. Ractopamine increased (P less than .0001) amount (FSL) and percentage (PFSL) of carcass lean standardized to 10% fat content, loin eye area (LEA), and dressing percentage (PDRES) and reduced (P less than .01) amount (DF) and percentage (PDF) of dissected fat. Magnitudes of RAC effects were smaller than those reported by other researchers. Effects of GT and WT on all growth and carcass traits were highly significant (P less than .001) except for those of WT on ADG (P less than .05) and GT on average feed intake (AFI) and backfat thickness at the last rib (BFLR; P less than .05). Genotype 3 performed better for most economically important traits than did GT 1 and 4, suggesting that heterosis existed in GT 3, which essentially was obtained by crossing GT 1 and 4. Among the three treatment periods, WT 2 had the highest ADG. As BW increased from WT 1 to 3, AFI and AFI/ADG ratio (FCR) increased and lean percentage decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Associations between carcass lean and predictors of lean in the pig

For the pig breeder there are many important selection objectives - optimum progress can be made if sires and dams are selected for different objectives. In dam lines some emphasis on maternal traits is practicable while maintaining slightly higher fat levels than in sire lines. Meanwhile lean growth and low fatness can be emphasised in the terminal sire lines. This gives the flexibility to fulfil different end markets and weights. Selection accuracy in such programmes is often improved by the addition of detailed carcass information from slaughtered sibs or other relatives of selection candidates.For the commercial producer, classification schemes differentiate payments on the basis of backfat and in some cases, lean measurements. However, despite the fact that future payments are likely to place greater emphasis on leanness, there is no differentiaton for breed or genotype.The purpose of this investigation was to follow up a previous study (Walters and Simpson, 1988) to determine whether lean prediction in the carcass depends on slaughter weight and genotype, to identify the best predictors of leanness and to estimate multiple correlation coefficients for predicting lean in carcass from lean in sample joints.

Postweaning performance and carcass characteristics of crossbred ewe lambs produced in accelerated or annual lambing systems.

Weaning, postweaning and carcass characteristics of ewe lambs were analyzed to determine if significant interactions occurred among management options. Management options considered were type of lambing system, choice of maternal and terminal sire lines and month of birth within lambing system. In general, significant interactions were not observed, suggesting production (output) characterizations for the postweaning period can be extended across management options. The experimental protocol associated with the types of lambing system resulted in a highly significant effect of lambing system upon all characteristics, especially in relation to age, weight and feed consumption characteristics prior to slaughter. Suffolk-sired lambs tended to be heavier for most weight characteristics, fatter and have higher carcass quality and leg conformation scores relative to Columbia-sired lambs. Differences of fraction of Finn sheep (Finn, .50 vs .25) of the dam were not noted, with the exception of weaning weight (21.2 +/- .28 and 22.2 +/- .27 kg, respectively) and carcass quality and leg conformation scores. Within the annual lambing season, lambs born in March and April were heavier at weaning, consumed less feed and required less weight gain to attain market weight than lambs born in May. Lambs from the May lambing had significantly higher gross feed efficiency ratios. Within the accelerated lambing system, the lambs born in January to February period tended to be heavier than lambs from the other lambing periods. Observed differences among month of lambing within lambing system for other characteristics were not consistent.

Some considerations on selection criteria and optimization for terminal sire breeds

SUMMARY The efficiency of selection of beef breeds for terminal crossing has been analysed in terms of selection criteria for growth and methods for selection of sires, notably with reference to the situation and research in France. With respect to selection of specialized beef lines, the advantage of control of the individual feed intake and of carcass performances as compared to control of growth only is shortly discussed. For this purpose, not only the favourable indirect response but also the resulting increment of feed intake and changes in body composition according to the reference system used (weight, duration, age) should be taken into account. Because of the increase in birth weight due to the intensification of selection for muscle growth within the beef breeds and the strong genetic correlation between this weight and the paternal component of calving difficulties, it seems advisable to use restricted indices for selection on birth weight, at least for terminal sire lines used in heifers. In the French situation of terminal crossing practised on suckling cows of dual purpose or hardy breeds with the aim of producing veal calves, a special attention has been paid to the genetic and economic advantage of two stage selection for choosing bull sires : selection on a sta

Experimental designs for building a synthetic dam line for meat production in sheep

A synthetic new dam line to be mated by a terminal sire line (C-line) for fat lamb production in commercial crossbreeding is to be developed by crossing a local breed (Merinolandschaf, A-line) and an exotic breed (Finnish Landrace, B-line). Therefore the following parameters must be known: • a = mean performance level by crossing dams of the home line with sires of the C-line (= control level). • d = change of performance compared to a, if B ewes are mated to C rams. • h = maternal heterosis, caused by AB cross gene combinations. The derivation of these parameters is shown in detail. Two alternative experimental designs for estimation of these parameters are discussed: method 1 requires importation of B ewes so that test results for this group are available; method 2 requires only importation of rams of the B-line. It is shown that in order to estimate the parameters with equal precision many more animals must be tested by method 2 than by method 1.