Average Backfat Research Articles

Effects of modified tall oil and creatine monohydrate on growth performance, carcass characteristics, and meat quality of growing-finishing pigs.

The effects of feeding modified tall oil (MTO) and creatine monohydrate (CMH) on growing-finishing pig growth performance, carcass characteristics, and meat quality were determined. Eighty cross-bred barrows (initially 45.4 kg) were allotted randomly to one of four dietary treatments by weight and ancestry. The experiment was arranged as a 2 x 2 factorial with two levels of MTO (0 or 0.50%), which were fed throughout the growing-finishing period, and two levels of CMH (0 or 25 g/d), which were fed for the final 10 d before slaughter. The corn-soybean meal diets were fed in two phases (45.4 to 78.9 kg and 78.9 to 117.5 kg BW). When CMH was added to the diet in place of corn, average BW was 107.5 kg. Feeding MTO increased (P < 0.05) ADG and gain:feed ratio (G/F) during the 45.4- to 78.9-kg growth interval and tended to improve (P = 0.10) G/F during the 45.4- to 107.5-kg growth interval. Dietary treatment did not affect (P > 0.15) growth performance during the 78.9- to 107.5-kg growth interval. Modified tall oil increased (P = 0.02) G/F during the 10-d CMH supplementation period, and CMH numerically (P = 0.11) increased ADG and G/F. Supplementation of CMH did not affect (P > 0.20) any measured carcass characteristic or measures of meat quality at 24 h or 14 d postmortem. Feeding MTO reduced average back-fat (P = 0.05) and 10th rib backfat (P = 0.01) but did not affect (P > 0.10) other measured carcass characteristics or measures of meat quality at 24 h postmortem. Modified tall oil increased (P = 0.02) L* values (lightness) and tended to increase (P < 0.10) thawing and cooking losses of longissimus muscle chops at 14 d postmortem. These data demonstrate that MTO improves growth performance and reduces backfat in growing-finishing pigs, but supplementation of CMH, under the conditions of this experiment, was not beneficial for growing-finishing pigs.

Effects of modified tall oil versus a commercial source of conjugated linoleic acid and increasing levels of modified tall oil on growth performance and carcass characteristics of growing-finishing pigs.

Two experiments were conducted to evaluate the effects of conjugated linoleic acid (CLA)-enriched feed additives for swine. These additives included a source of CLA that was commercially available (CLA-60) and modified tall oil (MTO). Experiment 1 used 36 barrows (initially 37.6+/-2.8 kg) to compare the effects of CLA-60 and MTO on growth performance and carcass characteristics of finishing pigs. The corn-soybean meal diets contained .50% soybean oil (control), .50% CLA-60, or .50% MTO. Pigs fed CLA-60 had less (P = .03) ADG from 37.6 to 72.6 kg than the control pigs; otherwise, pigs fed either CLA-60 or MTO had growth performance similar (P > .15) to that of the control pigs. Pigs fed MTO grew faster (P = .03) and consumed more feed (P = .10) over the duration of the experiment (37.6 to 106.4 kg) than pigs fed CLA-60. Dietary treatment did not affect (P > .15) plasma triglycerides or carcass characteristics, but pigs fed either MTO or CLA-60 had greater saturation of fatty acids in the adipose tissue at the 10th rib than pigs fed the control diet. Experiment 2 used 80 barrows (initially 33.4+/-2.2 kg) to examine the effects of increasing levels of MTO on growth performance and carcass characteristics of finishing pigs. The corn-soybean meal diet contained 1% cornstarch, which was replaced with MTO to give dietary levels of .25, .50, or 1.00% MTO. Dietary treatment did not affect (P > .15) growth performance. Feeding increasing levels of MTO quadratically decreased (P = .02) average backfat thickness and longissimus muscle drip loss (P = .04) and quadratically increased longissimus muscle area (P = .07) and percentage lean (P = .03). Feeding MTO tended to increase belly firmness (P < .10) compared with pigs fed the control diet. These traits appeared to be optimized with .50% MTO. In summary, pigs fed MTO had greater ADG, ADFI, and ending BW than pigs fed CLA-60. Feeding MTO does not appear to affect growth performance but improves carcass lean content and may additionally improve some aspects of meat quality in growing-finishing pigs.

Genetic parameters and genetic trends in the Chinese x European Tiameslan composite pig line. I. Genetic parameters.

Genetic parameters of body weight at 4 (W4 w), 8 (W8 w) and 22 (W22 w) weeks of age, days from 20 to 100 kg (DT), average backfat thickness at 100 kg (ABT), teat number (TEAT), number of good teats (GTEAT), total number of piglets born (TNB), born alive (NBA) and weaned (NW) per litter, and birth to weaning survival rate (SURV) were estimated in the Chinese × European Tiameslan composite line using restricted maximum likelihood methodology applied to a multiple trait animal model. Performance data from a total of 4 881 males and 4 799 females from 1 341 litters were analysed. Different models were fitted to the data in order to estimate the importance of maternal effects on production traits, as well as genetic correlations between male and female performance. The results showed the existence of significant maternal effects on W4w, W8w and ABT and of variance heterogeneity between sexes for W22w, DT, ABT and GTEAT. Genetic correlations between sexes were 0.79, 0.71 and 0.82, respectively, for W22w, DT and ABT and above 0.90 for the other traits. Heritability estimates were larger than (ABT and TEAT) or similar to (other traits) average literature values. Some genetic antagonism was evidenced between production traits, particularly W4w, W8w and ABT, and reproductive traits.

Genetic parameters and genetic trends in the Chinese x European Tiameslan composite pig line. II. Genetic trends.

The Tiameslan line was created between 1983 and 1985 by mating Meishan × Jiaxing crossbred Chinese boars with sows from the Laconie composite male line. The Tiameslan line has been selected since then on an index combining average backfat thickness (ABT) and days from 20 to 100 kg (DT). Direct and correlated responses to 11 years of selection were estimated using BLUP methodology applied to a multiple trait animal model. A total of 11 traits were considered, i.e.: ABT, DT, body weight at 4 (W4w), 8 (W8w) and 22 (W22w) weeks of age, teat number (TEAT), number of good teats (GTEAT), total number of piglets born (TNB), born alive (NBA) and weaned (NW) per litter, and birth to weaning survival rate (SURV). Performance data from a total of 4 881 males and 4 799 females from 1 341 litters were analysed. The models included both direct and maternal effects for ABT, W4w and W8w. Male and female performances were considered as different traits for W22w, DT and ABT. Genetic parameters estimated in another paper (Zhang et al., Genet. Sel. Evol. 32 (2000) 41-56) were used to perform the analyses. Favourable phenotypic (ΔP) and direct genetic trends (ΔGd) were obtained for post-weaning growth traits and ABT. Trends for maternal effects were limited. Phenotypic and genetic trends were larger in females than in males for ABT (e.g. ΔGd = -0.48 vs. -0.38 mm/year), were larger in males for W22w (ΔGd = 0.90 vs. 0.58 kg/year) and were similar in both sexes for DT (ΔGd = -0.54 vs. -0.55 day/year). Phenotypic and genetic trends were slightly favourable for W4w, W8w, TEAT and GTEAT and close to zero for reproductive traits.

Effect of Lactation Diet Fat Level on Sow and Litter Performance

The primary objective of this study was to determine the effects of supplemental dietary fat during lactation on sow BW, sow backfat thickness, sow feed consumption, litter size, and pig growth rate. Dietary treatments included 0, 3, 6, and 9% supplemental low acid yellow fat in a traditional corn-soybean meal basal lactation diet. A total of 160 Landrace and crossbred sows (approximately 40 per treatment) were included in the study. Sows fed 3 and 6% supplemental fat had greater (P<0.10) average backfat thickness at weaning. Sow weight change and feed consumption were inconsistent among dietary fat levels. Dietary fat level during lactation did not affect number of pigs born alive or number of stillborns. However, the 9% fat level was associated with more mummified pigs at birth. Number of pigs weaned was greater for the 0% supplemental fat than for the 9% fat level. The largest average pig weights at 21 (5.8±0.29 kg) and 28 (7.48±0.38) d of age were those from sows fed the 3% added fat diet. Sows with ≤25.4mm backfat at farrowing had more pigs born alive (P<0.05), had less backfat at 21 and 28 d of lactation (P<0.05), and consumed more feed during wk 2 and 3 of lactation. Of all sows fed the control diet, sows with >25.4mm backfat at farrowing consistently had heavier pigs throughout the lactation phase (P<0.05). Backfat loss during lactation was lower (P<0.05) for sows with ≤25.4mm at farrowing within all dietary treatments. Consistent significant differences were not observed in sow weight loss or feed consumption between low and high backfat sows for each dietary treatment. Sow backfat loss during lactation is dependent on body condition at farrowing, in that, fatter sows at farrowing have greater backfat loss during lactation. Sows with ≤25.4mm of backfat at farrowing responded to added dietary fat treatments and produced heavier pigs throughout the lactation period.

Mapping genes for growth and fatness in pigs with data from international studies

The use of genetic markers to identify regions of the genome associated with variation in quantitative traits (QTL) is now widespread. Several studies have attempted to find QTLs for growth and fatness in pigs. Since the first published study (Anderssonet al., 1994) many groups have found effects on chromosome 4, albeit with different breeds. In theory, joint analysis offers considerable potential to extract additional information from the data. This study aims to investigate the benefits and drawbacks of joint analysis.Data on birth weight (BWT), growth rate to end of test or slaughter (GRE) and average backfat depth (BF) were supplied from seven different pig populations in six countries. The data from Scotland, France, USA, Netherlands and half of the data from Germany were Meishan (MS) x commercial F2populations. Data from Sweden and the remaining German data were from wild boar (WB) x commercial F2populations. A total of 31 different markers were used, all on chromosome 4.

A directed search for quantitative trait loci on chromosomes 4 and 7 in pigs.

Improvements in the porcine genetic map and availability of resource families to study performance traits in pigs have made it possible to re-examine previous findings that linked certain traits to genes or chromosomal regions. Previous studies suggested that chromosomes 4 and 7 may be associated with growth and performance traits. To confirm these previous results, an interval mapping-regression approach was used to determine whether quantitative trait loci (QTL) exist in the Iowa State University reference/resource families. Traits measured were birth weight; body weight at 21 d; weaning weight (weight at 42 d); average daily gain; backfat at the first, 10th, lumbar, and last ribs and average backfat thickness; loin eye area; meat color; marbling; and firmness. The total number of F2 pigs used ranged from 241 to 330 and came from five Chinese x American resource families. Five markers (S0001, SW871, S0175, S0214, and SW445) were genotyped and mapped on chromosome 4, and so were 10 markers (S0064, tumor necrosis factor alpha [TNFalpha], S0102, S0078, S0158, S0066, SW304, SW1083, S0101, and S0212) on chromosome 7. Data were analyzed for each family (breed cross) separately and were also pooled. Experiment-wise thresholds were used to determine significance. Suggestive evidence of QTL on chromosomes 4 and 7 was observed for several traits in pooled and individual family analyses. Suggestive evidence of a QTL with a relatively large effect for average daily gain was detected on chromosome 4 in the pooled analysis. Significant (P < .05) evidence for QTL was seen on chromosome 7 for 10th-rib, last-rib, and average backfat thickness in the pooled data set in a region of the chromosome that was near TNFalpha. These results verify in part that chromosomes 4 and 7 contain QTL for growth and carcass traits.

ブタの日平均増体重と屠体形質における遺伝的パラメーターの推定

Estimates of heritability, genetic and phenotypic correlations among carcass traits, and between average daily gain and carcass traits are reported. The data came from Miyazaki and Iwate prefectures in Japan, and involved 1, 256 records of Large White barrows born between 1981 and 1986. The traits of interest were average daily gain (ADG), dressing out percentage (DOP), carcass loin length (CLL), loin eye area (LEA), average backfat thickness (ABF) and proportion cut ham (PCH). Genetic parameters were estimated by REML under a multitrait animal model including all the six traits. Line and generation were considered as fixed effects in the model. All traits were adjusted for body weight at slaughter. Estimates of heritability were, 0.32, 0.43, 0.56, 0.65, 0.71 and 0.52 for ADG, DOP, CLL, LEA, ABF and PCH, respectively. Genetic correlations between ADG and carcass traits ranged from -0.34 to 0.06. Genetic correlations among carcass traits ranged from -0.65 to 0.37. It was concluded that selection for improved growth rate and carcass composition should be effective.

The effect of genotype on feedlot performance, carcass composition, and lean meat quality from commercial pigs

A total of 60 female and 54 castrated male progeny of commercial Landrace × Large White F1 sows, backcrossed to Landrace or Large White boars, were slaughtered at an average liveweight of 102 kg. Four same-sex pigs were penned together. Large White sires were homozygous normal (NN) but Landrace sires were heterozygous carriers (Nn), at the halothane locus. Progeny genotypes at the halothane locus were determined by a DNA probe. Barrows grew 136 g d−1 faster (P &lt; 0.0001), reaching market weight 13 d sooner (P &lt; 0.0001) but with 3.2 mm more average back-fat (P &lt; 0.0001) than gilts. Both sexes had similar feed requirements (P = 0.1221). Landrace and Large White-sired pigs had similar growth rate (P = 0.6458) and feed requirements (P = 0.9354), but Large White-sired pigs had 1.33 mm less grade fat thickness (P = 0.0131) and 1.72 more muscle depth (P = 0.0218) than Landrace-sired pigs. Nn pigs required 7 d longer (P &lt; 0.0001) and 22 kg (P = 0.0393) more total feed to reach market weight than NN pigs, but they had 2.6 mm greater muscle depth (P = 0.0008) and had 1% greater commercial lean yield (P = 0.0291). However, meat quality of Nn pigs was reduced when compared with NN pigs. For example, colour reflectance and drip loss were higher (P &lt; 0.0001) and soluble protein was lower (P &lt; 0.0001) among the Nn pigs which also had less intrasmuscular fat (P = 0.0184). The results emphasize that the increased value of the carcass from Nn pigs may be offset by reduced feedlot performance and reduced meat quality, and questions the merit of the use of halothane gene to improve production efficiency in the commercial market. Key words: Swine production, halothane gene, breed effect, Landrace, Large White

Genetic association between feed intake and feed intake behaviour at different stages of growth of group-housed boars

Abstract Voluntary feed intake, feed intake pattern and performance traits were recorded on 3188 group housed boars of Landrace and Large White tested from day 100 to day 170. Measurements of feed intake and feed intake behaviour were obtained by electronic feed dispensers (ACEMO) under ad libitum conditions. Heritabilities of feed intake in periods 1 to 5 and over the entire test period were estimated to be 0.16, 0.24, 0.30, 0.27, 0.26, and 0.22, respectively. The maximum heritability of daily feed intake in the third time period on test corresponds to about 130 days of age at about 85 kg of weight. Daily feed intake in this period showed a high genetic correlation with the average feed intake over the whole performance test (rg = 0.91). Estimates of genetic correlations between daily feed intake and feed conversion ratio, residual feed intake, average daily gain or backfat thickness were 0.04, 0.97, 0.62 and 0.42, respectively. Boars feed intake activities decreased over time while time per day in the feeder was almost constant. Traits of feed intake behaviour as feeding rate, feed intake/visit, number of visits, time per visit, and time per day in the feeder showed high heritabilities of 0.44, 0.51, 0.43, 0.42, and 0.43, respectively, but genetic correlations with performance and carcass traits were generally low. One exception was the behavioural trait time per day in the feeder with its moderate genetic correlations to daily feed intake (rg = 0.44) and average daily gain on test (rg = 0.32). Selection for lean growth will improve lean growth feed efficiency as indicated by the negative correlation of −0.47. But more efficient may be the use of the component traits, lean content, daily feed intake and daily gain in particular of the most informative test period.

Genetic and phenotypic relationships between performance test and reproduction traits in Large White pigs

AbstractGenetic and phenotypic relationships between performance test and reproduction traits were estimated, after five generations of divergent selection for components of efficient lean growth, in a population of Large Wltite pigs. On ad-libitum feeding, a total of 4334 pigs were performance tested, of which 884 selected gilts had measurements of reproduction traits. On a restricted feeding regime, 1558 pigs were tested, which included 336 selected gilts with reproduction records. For pigs given food ad libitum, genetic correlations between litter weights at birth and weaning with daily food intake (0·48 and 0·42, s.e. 0·16) and with growth rate on test (0·65 and 0·52) were positive, but correlations with backfat depths were not significantly different from zero. For pigs given food at a restricted level, litter birth weight was positively genetically correlated with growth rate (0·50, s.e. 0·18) and negatively correlated with backfat depths (-0·48, s.e. 0·16). Phenotypic and environmental correlations between performance test and reproduction traits were all less than 0·10 in magnitude, for pigs tested on either feeding regime. The variation in backfat depth enabled detection of a non-linear relationship between predicted breeding values for litter weight at birth with predicted breeding values for average backfat depth of farrowing gilts performance tested on ad-libitum feeding, but not for gilts tested on restricted feeding. The positive genetic correlations between growth rate and daily food intake with litter traits suggested that selection strategies which change growth and daily food intake may result in relatively greater genetic changes in piglet growth rate than in litter size.

Real-time ultrasound image analysis for the estimation of carcass yield and pork quality

Average backfat thickness measurements (liveweight of 92.5 kg) were made on 276 pigs using the Krautkramer USK7 ultrasonic machine. Immediately preceding and 1 h after slaughter real-time ultrasonic images were made between the 3rd and 4th last ribs with the Tokyo Keiki LS-1000 (n = 149) and/or CS-3000 (n = 240) machines. Image analysis software was used to measure fat thickness (FT), muscle depth (MD) and area (MA) as well as scoring the number of objects, object area and percentage object area of the loin to be used for predicting meat quality. Carcasses were also graded by the Hennessy Grading Probe (HGP). Prediction equations for lean in the primal cuts based on USK7 and LS-1000 animal fat measurements had R2-values (residual standard deviations, RSD) of 0.62 (27.0) and 0.66 (25.7). Adding MD or MA to LS-1000 FT measurements increased the R2-values to 0.68 and 0.66. Prediction equations using animal fat measurements made by the USK7 and CS-3000 had R2-values (RSD) of 0.66 (26.5) and 0.76 (22.4). Adding MD or MA to CS-3000 FT measurements made no further improvement in the R2-values. Estimation of commercial lean yield from carcass FT and MD measurements made by the HGP and LS-1000 had R2-values (RSD) of 0.58 (1.72) and 0.65 (1.56). Adding MA to LS-1000 measurements made no further improvement in the R2-values. Prediction equations based on carcass FT and MD measurements made by the HGPandCS-3000 had R2-values (RSD) of 0.68 (1.65) and 0.72 (1.54). Adding MA to CS-3000 measurements made no further improvement in the prediction equation. It was concluded that RTU has most value for predicting carcass lean content and further improvements in precision will come from more accurate FT measurements from RTU images made by image analysis software. Correlation of the number of objects, object area and of percent object area of image from RTU images with intramuscular fat or marbling score made on the live pig or carcass were low, and presently do not appear suitable for predicting intramuscular fat. Key words: Carcass composition, meat quality, marbling, intramuscular fat, sex, pigs

Effect of a single injection of a long-acting gonadotropin-releasing hormone agonist on prepubertal male and female pigs on reproductive organs, growth performance and sensory qualities of pork roasts.

Crossbred pigs (n = 200) were used to study the effects of a long-acting form of gonadotropin-releasing hormone (GnRH) agonist on the reproductive systems of male and female pigs and their growth performance and sensory quality of pork roast. Treatment was a single injection of a controlled release formulation of GnRH agonist [D-Trp6, des-Gly10]-GnRH ethylamide to release 5 micrograms/(kg x day) for 4 months beginning when the pigs were 66 +/- 2 days old. Pigs were allocated to five groups of 40 animals each: males castrated (CM) at 13 +/- 2 days, intact males (IM), treated males (TM), intact females (IF) and treated females (TF). Ovarian and uterine weights at slaughter averaged 3.67 and 79.8 g, respectively, in IF compared with 1.38 and 26.5 g in TF (P < 0.05). Testicular weights were 203 g in IM and 36.8 g in TM (P < 0.05). Microscopic observations of the testes revealed an absence of sperm cells but the presence of germ cells. Steroid concentrations at slaughter from all pigs showed that intact males had significantly more testosterone in their serum (26.36 +/- 9.87 nmol/L) compared with TM, CM, IF or TF groups and that treated males had intermediate concentrations (12.50 +/- 7.44 nmol/L) higher (P < 0.05) than those in CM and TF. Administration of GnRH agonist during the growth period of male pigs had no consistent effect on growth performance, but as compared to IM pigs, some of the carcass characteristics such as meat ratio (49.1 vs 50.2% in TM and IM; P < 0.001), dressing percentage (77.5 vs 76.5% in TM and IM; P < 0.05) and average backfat (20.8 vs 17.6 mm in TM and IM; P < 0.05) were modified by such a treatment. Meat quality, however, as determined by flavor and tenderness evaluations by sensory panelists, were similar (P < 0.05) in all groups and off-flavor scores were lower in TM than in IM (P < 0.001). As for males, backfat and meat ratio were different in TF compared to IF (P < 0.05) and roast juiciness was higher in TF than IF (P < 0.05). These results suggest that GnRH agonist can reduce gonadal secretory activity to castration levels during the growth period of prepubertal male pigs and could be an alternative to surgical castration in the pork industry with no negative effects on growth and meat quality. No advantage to endocrine castration in females was found.

Genetic correlations between test station and on-farm performance traits in Large White and French Landrace pig breeds

Abstract Genetic correlations between test station and on-farm performance traits were estimated in Large White (LW) and French Landrace (LF) pig breeds using a restricted maximum likelihood procedure applied to a bivariate individual animal model. Traits recorded in test stations were average daily gain (ADG1), average backfat thickness (BT90), feed conversion ratio (FCR) measured on candidates to selection, average daily gain (ADG2), dressing percentage (DP), estimated carcass lean content (ECLC) and meat quality index (MQI) measured on slaughtered sibs. On-farm traits were age (A100) and average backfat thickness (BT100) at 100 kg. Test station data involved records on 7068 and 3392 candidates, 3332 and 1735 slaughtered sibs for LW and LF breeds, respectively. On-farm data consisted of records from 16670 (LW) and 8244 (LF) pigs of both sexes. Genetic correlations between A100 and ADG1 or ADG2 varied between −0.50 ± 0.05 and −0.67 ± 0.03. BT100 was strongly related to BT90 (0.91 ± 0.03 and 0.91 ± 0.05 in LW and LF breeds, respectively) and ECLC (−0.84 ± 0.05 and −0.70 ± 0.07 in LW and LF breeds, respectively). Strongly favourable genetic correlations were also obtained between FCR and A100 (0.32 ± 0.04 in LW; 0.54 ± 0.06 LF) or BT100 (0.45 ± 0.04 and 0.51 ± 0.06 in LW and LF breeds, respectively). MQI was almost independant of A100, but unfavourably related to BT100 in both breeds. These results tend to indicate that genotype × environment interactions in French national breeding programmes are limited for backfat depth, but remain significant for growth rate.

The effects of dietary protein concentration on compensatory growth in barrows and gilts.

An experiment using 120 crossbred pigs (60 barrows and 60 gilts) was conducted to determine the effect of dietary protein concentration on the compensatory response in growth after a period of feed restriction. Thirty pigs were allowed ad libitum (AL) access to one of five corn-soybean meal diets (13.1 to 18.4% CP) from approximately 42 to 102 kg BW. Thirty additional pigs were restricted (R) to a maintenance amount of a 14.4% CP diet for 21 d, after which they were allotted to one of the five diets and allowed ad libitum access to feed until they reached 102 kg. Restricted pigs had lower ADFI, ADG, and ADG/ADFI (P < .05) than did AL pigs. During the postrestriction period, R pigs had higher ADFI and ADG (P < .001) and tended to be more efficient (P < .08) than AL pigs. Average backfat thickness was not different (P > .8) between AL and R pigs. Lean percentage (5% fat) was not affected (P > .5) by feeding regimen but increased linearly (P < .1) as protein level increased. Organ weights (expressed as a percentage of empty BW.75) were similar in AL and R pigs. However, kidney and stomach weights differed among protein levels (P < .01), as did liver weight (P < .06), with a linear increase (P < .02) in both kidney and liver weights to dietary protein level. Barrows had higher ADFI and ADG and greater average backfat thickness (P < .02) than gilts. Barrows had smaller LMA, a lower percentage of lean (P < .001), and higher average backfat (P < .005) than gilts. Liver weight was heavier (P < .02) and small intestine weight tended to be heavier (P < .07) for barrows than for gilts. Kidney, spleen, and lungs were heavier (P < .05) in gilts than in barrows. Livers from barrows tended to contain more protein (P < .06) and less fat (P < .05) than livers from gilts. These results indicate that a compensatory growth response occurred during relimentation, and that the effects of dietary protein concentration on growth rate and carcass measurements were similar in both AL and R pigs.

The effect of dietary lysine on growth, carcass composition, and lipid metabolism in high-lean growth gilts fed from 72 to 136 kilograms.

One hundred fourteen high-lean growth gilts (72.5 kg BW) were used to determine the apparent digestible lysine requirement for maximum growth performance and carcass protein deposition rate from 72.5 to 136 kg BW. The experiment was a randomized complete block design with initial BW used to establish blocks. Six dietary treatments were included, ranging from .44 to .94% (.10% increments) apparent digestible lysine (.62 to 1.13% total lysine) with six replicate pens per treatment and three pigs per pen. Pig weights and feed consumption were collected weekly to determine ADG, ADFI, and gain: feed ratio (G/F). Six gilts were slaughtered at 72.5 kg BW to determine initial carcass composition. When the mean weight of pigs in a pen reached 104 or 136 kg, one pig per pen was selected (closest to 104 or 136 kg, respectively) and slaughtered for determination of carcass measurements and composition. From 72.5 to 104 kg and from 104 to 136 kg, ADG and G/F increased (linear, P < .05; quadratic, P < .10, respectively) as apparent digestible lysine increased. From 72.5 to 136 kg, G/F increased (quadratic, P < .10) as apparent digestible lysine increased. Average backfat thickness and longissimus muscle area at 104 kg were not influenced (P > .10) by apparent digestible lysine. However, average backfat thickness increased (quadratic, P < .05) with increasing digestible lysine for gilts slaughtered at 136 kg. Carcass CP accretion was not influenced (P > .10) from 72.5 to 104 kg but tended to increase (linear, P < .10) from 72.5 to 136 kg as digestible lysine increased. Plasma and longissimus muscle cholesterol concentrations were unaffected (P > .10) by increasing digestible lysine. These results suggest that high-lean growth gilts require greater dietary lysine than current NRC (1988) estimates to maximize ADG, G/F, and carcass CP accretion from 72.5 to 104 and from 104 to 136 kg.

Effects of urea as a source of extra dietary nitrogen on growth performance and carcass traits of finisher pigs

Forty-two crossbred pigs weighing 54.2 ± 5.5 kg were used to evaluate the value of urea as a source of extra nitrogen ( N) to enhance carcass leanness of finisher pigs. Three soybean meal ( SBM) diets were formulated to contain 0.60 and 13.2% ( Low), 0.73 and 15.5% ( Med) or 0.85 and 16.7% ( High) lysine and crude protein ( CP), respectively. Two urea diets were formulated to be iso-nitrogenous ( Iso-N) to the Med and High SBM diets. Two additional urea diets were formulated to be iso-lysinic ( Iso-Lys) to the Med and High SBM diets by incorporating crystalline amino acids. The indispensable amino acid contents were at least 20.8 and 41.7% above the current NRC requirements for the Med and High Iso-Lys diets, respectively. To ensure an adequate supply of CP from common feed ingredients for pigs, corn and SBM contributed 13.2% CP to four urea diets, and urea supplied additional CP equivalent. Pigs were housed individually, and allowed ad libitum access to feed. All pigs were slaughtered at an average weight of 103.2 ± 4.5 kg. Pigs fed the Low SBM diet tended to grow faster ( P = 0.09) than those fed other diets (1.09 vs 1.02 kg/day). However, the average backfat ( BF; 36.4 vs 32.1 mm; P < 0.05) and 10th rib BF (33.1 vs 28.9 mm; P = 0.10) were higher, and carcass specific gravity (1.046 vs 1.041; P < 0.05) and proportion of lean (47.6 vs 44.7%; P = 0.08) were lower in pigs fed the Low diet than those fed the Med and High diets, indicating that a higher weight gain was achieved by the increased rate of fat accretion. The results indicated that the carcass quality was improved by increasing lysine and(or) N levels from low to medium regardless of the source [ SBM or urea and(or) amino acids]. In addition, simply incorporating urea to increase dietary N (Iso-N) from low to medium and amino acid supplementation of urea diets (Iso-Lys) were equally effective in enhancing the carcass quality of pigs, indicating that overall utilization of diets was improved by the inclusion of urea. There was, however, no improvement in the carcass quality of finisher pigs with further increases in dietary lysine and(or) N levels from medium to high.

Effect of divergent selection for postweaning average daily gain on front-end soundness of market-weight pigs.

A total of 975 barrows and gilts from lines divergently selected for postweaning ADG were evaluated for front-end structural soundness (scored on a scale from 1, extreme leg weakness, to 8, superior leg structure) at approximately 100 kg, as well as growth performance and backfat thickness. Selection was for either fast (line F) or slow (line S) ADG from 9 wk of age to 100 kg and was replicated in spring- and fall-farrowing groups. The cumulative divergent selection differential corresponding to the animals evaluated was .47 kg/d (approximately 5 standard deviations). There was a line x sex x farrowing group interaction (P < .05) for ADG. Pigs from F grew faster (P < .01) than pigs from S, but the difference between lines was greater in gilts than in barrows. This interaction between line and sex was more pronounced in the spring- than in the fall-farrowing group. Average daily feed intake was 23% greater (P < .01) for F pigs than for S pigs. Even though pigs from F consumed more feed than those from S, their relatively faster ADG resulted in a greater (P < .01) feed efficiency (gain/feed) in F than in S. There was a line x farrowing group interaction (P < .05) for average backfat thickness adjusted to 105 kg. Barrows and gilts from F had 3.9 and 8.3% greater backfat thickness than those from S in the fall- and spring-farrowing groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of PIT1 polymorphisms with growth and carcass traits in pigs2

PIT1, a member of the POU-domain family of genes, is a positive regulatory factor of growth hormone, prolactin, and thyrotroph-stimulating hormone beta in several mammals. Therefore, PIT1 was chosen as a candidate gene to investigate its association with growth and carcass traits in pigs. The five Iowa State University reference/resource three-generation families consisting of crosses of Meishan x Duroc, Meishan x Hampshire, Meishan x Landrace, Minzhu x Hampshire, and Minzhu x Landrace were used. The three PIT1 polymorphisms were based on two RFLP using a PIT1 POU-domain cDNA probe and the restriction enzymes BamHI and MspI and a PCR/RFLP using RsaI. Birth, 21-d, and 42-d weights, average daily gain, several backfat measurements, longissimus muscle area, muscle color, marbling, and firmness scores were evaluated for their association with the three PIT1 polymorphisms. Mixed-animal-model analyses were used with the informative family data in which the PIT1 polymorphisms were segregating. Results from mixed-model analyses revealed that pigs with the MspI CC genotype (P < .01) were associated with heavier birth weight (.12 kg) than DD genotype pigs. The MspI CC genotype pigs were also significantly associated with greater average backfat (.41 cm, P < .01), greater first-rib backfat (.45 cm, P < .01), greater last-rib backfat (.32 cm, P < .07), and greater last lumbar backfat (.46 cm, P < .10) than the DD genotype pigs. The CC genotype represents primarily Chinese alleles and may be useful for future genetic improvement in synthetic lines involving Chinese and American pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect on performance and carcass characteristics of nursery to finisher pigs fed reduced crude protein, amino acid-supplemented diets

An experiment was conducted to evaluate the effect of feeding reduced CP, amino acid (AA)-supplemented diets to pigs from weaning to slaughter weight on growth performance and carcass characteristics. Pigs were fed a 19%-16%-14% CP starter-grower-finisher high-CP sequence of diets, respectively, or a sequence of diets reduced in CP by 4 percentage units (3 percentage units in the finisher period) with or without lysine (LYS), tryptophan (TRP), and threonine (THR) supplementation. Pigs fed the low-CP diets without AA supplementation grew more slowly, were less efficient in feed conversion, and developed carcasses that contained a smaller longissimus muscle, greater, average backfat depths, and a lower percentage of muscle compared with pigs fed the high-CP sequence of diets (P < .01). The reduction in growth performance, feed efficiency, longissimus muscle area, and percentage of muscle in pigs fed the low-CP diets was alleviated by LYS, TRP, and THR supplementation (P > .10). Although pigs fed the low-CP diets supplemented with AA had reduced average and 10th rib backfat depths compared with pigs fed the unsupplemented, low-CP diets (P < .01), these fat depth measures remained greater (P < .05) than those of pigs fed the high-CP diets. Feeding reduced dietary CP, regardless of AA supplementation, resulted in reduced heart (P < .10) and liver weights (P < .01) compared with feeding the high-CP diets.(ABSTRACT TRUNCATED AT 250 WORDS)