Relationship between in vitro assays and standardized ileal amino acid digestibility of animal protein meals in broilers.

Two identical trials were conducted to determine the relationship of a novel digestive enzyme assay, Poultry Complete IDEA (PC IDEA), and the pepsin digestibility assay with standardized ileal amino acid digestibility (SIAAD) of 20 animal protein meals (APM) fed to broilers from 25 to 30 d of age. Animal protein meals included 10 meat and bone meals (MBM) consisting of bovine, porcine, or mixed bovine and porcine raw materials (BP), and 10 animal protein blends containing animal proteins from various species. Treatments consisted of 20 semi-purified diets containing 1 APM as the sole source of dietary amino acids (AA), and 1 N-free diet to determine endogenous ileal AA flow. With the exception of the N-free diet, diets were formulated to contain 20% CP. In each trial, 756 Ross × Ross 708 male broilers were housed in battery cages and randomly assigned to 21 dietary treatments on d 25 (12 birds per cage; 3 replicate cages), and ileal digesta were collected on d 30 for determination of SIAAD. Pepsin digestibility and PC IDEA were determined for APM samples from each experimental diet (3 replicates per trial; 6 total replicates). Pepsin digestibility and PC IDEA were both correlated (P < 0.001) with SIAAD for each AA. Multiple linear regression of PC IDEA and pepsin digestibility on SIAAD resulted in the following equations: % Lys SIAAD = [-9.65 + (0.38 × % PC IDEA predicted Lys digestibility) + (0.69 × % pepsin digestibility)], % Met SIAAD = [-35.95 + (0.62 × % PC IDEA predicted Met digestibility) + (0.75 × % pepsin digestibility)], % Thr SIAAD = [-77.5 + (0.39 × % PC IDEA predicted Thr digestibility) + (1.37 × % pepsin digestibility)]. Values of R(2) were 0.46, 0.47, and 0.55 for Lys, Met, and Thr, respectively. The relatively low R(2) values may have been due to the limited range in SIAAD observed for the 20 APM, and additional data on APM varying in SIAAD are needed.

Correlated responses in reproductive and carcass traits to selection for 200-day weight in Landrace pigs.

Correlated responses in reproductive and carcass traits from a line of Landrace pigs selected for increased 200-d weight along with a randomly selected control line were studied in 195 litters (109 select, 86 control) and 285 pigs (132 select, 153 control). Reproductive and maternal traits studied included litter sizes born, born alive, and alive at 21 d and litter weights at birth and at 21 d. Carcass traits studied were carcass length, longissimus area, average backfat thickness, 10th-rib backfat thickness, specific gravity, weights of closely trimmed ham, loin, and shoulder, belly weight, subjective scoring of the longissimus muscle for color and marbling, estimated percentage of muscle, and lean growth. Total weighted cumulative selection differential for 200-d weight over six generations was 88.7 kg. The realized heritability for 200-d weight was .26 +/- .08, and the change in 200-d weight was 4.2 +/- 1.3 kg per generation. None of the regression coefficients for reproductive traits differed significantly from zero. Ham weight, belly weight, marbling score, and lean growth increased by .069 +/- .027 kg, .051 +/- .020 kg, .045 +/- .012 points, and .0042 +/- .0007 kg/d, respectively, per generation. Specific gravity decreased by -.00063 +/- .00023 per generation in response to the selection for 200-d weight. The increase in lean growth in the select line was the result of an increased growth rate and not from an improvement in percentage of lean in carcasses from pigs from the select line.

Mass selection for increased 200-day weight in a closed line of Duroc pigs.

Mass selection for increased weight at 200 d of age was conducted for six generations in a line of Duroc pigs. A randomly selected contemporary control line was maintained. Our objectives were to observe the response in 200-d weight, to measure correlated responses in weights at earlier ages, daily gains and ultrasound backfat thickness and to compare three methods for estimating responses to selection. Inbreeding coefficients averaged .213 and .202 for the select- and control-line pigs and .200 and .173 for the select- and control-line dams in the sixth generation, respectively. A total of 1,866 pigs were farrowed; 200-d weights were collected on 798 of them. These pigs were sired by 89 boars and were out of 193 sows. Twelve traits were studied: weights at birth and at 21, 35, 70, 154 and 200 d of age, daily gains from birth to 35 d, 35 d to 70 d, 70 d to 154 d and 154 d to 200 d, ultrasound backfat thickness at 200 d and ultrasound backfat thickness adjusted for 200-d weight. Three methods for estimating responses to selection gave similar results; therefore, the estimates were averaged. Total weighted cumulative selection differential for 200-d weight was 81.7 kg with a response in 200-d weight of 2.5 +/- 1.2 kg/generation. This response corresponds to a realized heritability for 200-d weight of .18 +/- .08. Increased weight at 200 d was the result of more rapid growth in the 154- to 200-d period, with decreased growth in the period from birth to 35 d. Growth at other periods was not changed significantly. Ultrasound backfat thickness at 200 d increased in the select line compared to the control line, but not when adjusted for 200-d weight.

Mass selection for increased 200-day weight in a closed line of Landrace pigs.

Mass selection for increased weight at 200 d of age was conducted for six generations in a line of Landrace pigs. In the select line, the heaviest nine boars and 18 gilts were selected from each generation to produce the subsequent generation. A contemporaneous control line was maintained by randomly selecting a son from each sire and a daughter from each dam to attain a line size of five boars and 10 gilts. Inbreeding coefficients averaged .182 and .191 for the select- and control-line pigs and .150 and .162 for the select- and control-line dams, respectively, in the sixth generation. The 200-d weights and ultrasound backfat thickness data were collected from 1,022 pigs of 2,181 pigs farrowed. These pigs were sired by 92 boars and out of 210 sows. The generation interval was 13 mo. Twelve traits were studied: weights at birth and at 21, 35, 70, 154, and 200 d of age; daily gains from birth to 35 d, 35 to 70 d, 70 to 154 d, and 154 to 200 d; ultrasound backfat thickness at 200 d; and ultrasound backfat thickness adjusted for 200-d weight. Total weighted cumulative selection differential for 200-d weight was 88.7 kg. Realized heritability for 200-d weight was .26 +/- .08 with an average response of 4.2 +/- 1.3 kg/generation. Correlated responses resulted in increases for all weights and daily gains evaluated. Although ultrasound backfat thickness at 200 d increased in the select line compared to the control line, it was not altered by selection for 200-d weight when adjusted for 200-d weight.

Mass selection for increased 70-day weight in a closed line of Landrace pigs.

Mass selection for increased weight at 70 d of age was practiced for six generations in a line of Landrace pigs. It was desired to have the next generation sired by the heaviest nine boars and out of the heaviest 27 gilts. A contemporaneous, randomly selected (by pedigree) control line was maintained in which the next generation was sired by five boars and out of 10 gilts. Inbreeding coefficients were .208 and .214 for the selected and control line litters and .177 and .189 for the selected and control line dams in the sixth generation, respectively. A total of 1,906 pigs was farrowed with 70-d weights collected on 1,267 pigs. These pigs were sired by 88 boars and out of 190 gilts. The generation interval was 13 mo. Six traits were studied: birth, 21-d, 35-d and 70-d weights and preweaning (from birth to 35 d) and postweaning (from 35 to 70 d) daily gains. Direct and correlated responses per generation and per weighted cumulative selection differential (WCSD) were estimated. Total WCSD for 70-d weight was 30.3 kg. This corresponds to a standardized WCSD of 6.11 phenotypic standard deviations. The response per generation for 70-d weight was .65 +/- .29 kg. The realized heritability for 70-d weight was .13 +/- .06. Nearly all the increased weight at 70 d was the result of more rapid growth in the postweaning period, with little difference in growth in the preweaning period; birth, 21-d and 35-d weights and preweaning daily gains remained unchanged by selection for 70-d weight.

Correlated responses in reproductive and carcass traits to selection for 200-day weight in Duroc swine.

Correlated responses in reproductive and carcass traits from a line of Duroc pigs selected for increased 200-d weight along with a randomly selected control line were studied in 189 litters (116 select, 73 control) and 191 pigs (106 select, 85 control), respectively. Reproductive and maternal traits studied included litter sizes born, born alive, and alive at 21 d and litter weight at birth and at 21 d. Carcass traits studied were carcass length, longissimus muscle area, average backfat thickness, 10th rib backfat thickness, specific gravity, weights of closely trimmed ham, loin, and shoulder, belly weight, subjective scoring of the longissimus muscle for color and marbling, estimated percentage of muscle and lean gain per day. Total weighted cumulative selection differential for 200-d weight was 81.7 kg. The realized heritability for 200-d weight was .18 +/- .08, and the change in 200-d weight was 2.5 +/- 1.2 kg per generation. The regression coefficient of litter size born on generation was -.29 +/- .12 (P less than .10) pigs per generation. None of the other regression coefficients for the reproductive traits differed from zero. Average backfat thickness, 10th rib backfat thickness, and belly weight increased by .093 +/- .016 cm, .122 +/- .029 cm, and .089 +/- .040 kg, respectively, per generation. Specific gravity, ham weight, shoulder weight, color score, and percentage of muscle decreased -.00086 +/- .00024, -.165 +/- .013 kg, -.104 +/- .011 kg, -.035 +/- .015 points, and -.47 +/- .12%, respectively, per generation in response to the selection.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlated responses in reproductive and carcass traits to selection for 70-day weight in Landrace swine.

Correlated responses in reproductive and carcass traits were studied in 181 litters and 218 pigs from a line of Landrace pigs selected six generations for increased weight at 70 d of age and a contemporaneous, randomly selected control line. The reproductive and maternal traits studied included litter sizes born, born alive, and alive at 21 d and litter weight at birth and at 21 d. Carcass traits studied were carcass length, longissimus muscle area, average backfat thickness, 10th-rib backfat thickness, specific gravity, weights of closely trimmed ham, loin, and shoulder, belly weight, subjective scoring of the longissimus muscle for color and marbling, estimated percentage of muscle, and lean gain per day. Total weighted cumulative selection differential for 70-d weight was 30.2 kg. The realized heritability for 70-d weight was .13 +/- .06, and the change in 70-d weight was .65 +/- .29 kg per generation. The regression coefficient of litter size at 21 d on generation was .24 +/- .10 (P less than .10) pigs per generation. None of the other regression coefficients for the reproductive traits differed from zero. Carcass length, specific gravity, and ham weight decreased (P less than .10) -.075 +/- .036 cm, -.00054 +/- .00027, and -.102 +/- .048 kg, respectively, per generation. Color score and lean gain per day increased .046 +/- .021 points and .0032 +/- .0013 kg/d, respectively, each generation in response to the selection.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of culling on selection response using phenotypic selection or best linear unbiased prediction of breeding values in small, closed herds of swine.

Records from 7,200 separate closed herds with either 12 or 25 sows that were mated to either four or eight boars per year were simulated by computer. Effects of selection method, herd size, and contemporary group variability on average genetic change, genetic variance, and inbreeding over 10 yr of selection were analyzed for traits with heritabilities of .1, .3, and .6. Selection of replacement animals was on individual phenotype or BLUP of breeding value using a reduced animal model. For both of these selection methods, two culling schemes were imposed: 1) based only on involuntary culling because of losses due to conception rate and age and 2) when an available replacement animal was projected to be superior to an existing breeding animal in the herd in addition to the involuntary culling. The contemporary group standard deviation was set at either .1 or .5 of a phenotypic standard deviation. Selection with BLUP gave 72, 36, and 12% more genetic improvement for heritabilities of .1, .3, and .6, respectively, than selection on individual phenotype after 10 yr. However, inbreeding increased 20 to 52% more rapidly and there was a decrease in genetic variance. Culling based on Scheme 2 increased genetic improvement over Scheme 1 by about 75% with coincident increases in inbreeding level and decreases in genetic variance. The largest changes in inbreeding and genetic variance were associated with culling on BLUP. Culling when a superior animal was available with individual phenotype had little effect on inbreeding and genetic variance. Use of four boars rather than eight boars and 25 rather than 12 sows per herd increased genetic response. Use of four boars also increased inbreeding and decreased genetic variance. Genetic variance was higher in herds with 25 sows, but the size of the sow herd had little effect on inbreeding. Contemporary group variation influenced only the genetic response of individual phenotypic selection with culling.

Estimates of additive genetic, maternal and specific combining abilities for some litter traits of swine.

Data from 1,234 purebred and crossbred litters were analyzed with a multiple regression procedure to obtain estimates of breed additive, breed maternal, specific combining ability (SCA) and average maternal heterosis effects for the Duroc (D), Hampshire (H), Landrace (L), Spot (S) and Yorkshire (Y) breeds. The traits studied were: number farrowed (NB), litter birth weight (LBWT), average pig birth weight (BWT), litter size at 21 d (N21), litter weight at 21 d (L21WT) and average pig weight at 21 d (WT21). The three traits measured at birth included stillborn pigs. The data were analyzed with a statistical model that included effects of research farm, sow group within year and farm and the regressions of the dependent variables on the D, H, S and Y breed additive genetic and breed maternal effects, deviated from the L breed. The model also included the regressions of the dependent variables on all possible two-breed heterotic combinations (SCA) and on average maternal heterosis. The breed additive and maternal regression coefficients indicated phenotypic effects of substituting D, H, S and Y genes for L genes. The SCA regression coefficients were the phenotypic effects of individual heterosis increasing from 0 to 100% for each two-breed combination. For the breed additive genetic component of the phenotype, the breeds ranked (from largest to smallest effect) H, Y, L, D, S for NB; Y, L, H, S, D for LBWT and Y, H, L, S, D for BWT. At 21 d, the breeds ranked Y, D, L, S, H for N21; Y, L, H, D, S for L21WT and Y, H, L, S, D for WT21.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of teat number, teat abnormalities and underline length on litter sizes and weights at 21 and 42 days in swine.

Data from 80 first-litter purebred and crossbred gilts of Duroc and Landrace breeding were analyzed to determine the effects of traits associated with their udder on the sizes and weights of their litters at 21 and 42 d. Traits measured on each first-litter gilt included: number of teats in front of the navel; number of functional teats; number of inverted and pin nipples; length of the underline; body length and weight at parturition. When the litter size nursed at 1 d was held constant, litter size at 21 and 42 d was not influenced by number of teats in front of the navel, number of functional teats, number of inverted nipples, number of pin nipples, body length or weight at parturition. First litter gilts with shorter underlines tended to raise larger litters at 21 and 42 d (P less than .05). Litter weights at 21 and 42 d were not affected by the number of teats in front of the navel, number of functional teats, number of inverted nipples, or by the number of pin nipples when the size and weight of the litters born alive were held constant. First-litter gilts with shorter body lengths tended to have heavier litters at 21 d, (P less than .05) while those with shorter underlines (P less than .05) and those that weighed more at parturition (P less than .10) tended to have heavier litters at 42 d. Results from this study are interpreted to indicate a replacement-gilt selection program that applies selection pressure for only increased teat number and against teat abnormalities seems unwarranted.

Halothane gene and swine performance.

One hundred thirty-one pigs representing seven different breed groups (Minnesota No. 1 [M], Pietrain [P], Yorkshire [Y], and crosses PY, P[PY], P[NP], and P[YP]P) and three halothane gene genotypes (NN, Nn, and nn) were tested for breed, sex, and halothane gene (HAL) effects on growth and carcass performance. Breed effects were significant for all traits measured. Sex effect was significant for most traits except for meat scores. The HAL-locus linkage group explained 20 to 30% of the total variation for meat quality scores and 1 to 10% for meat quantity and growth traits. Pietrain x Yorkshire was the fastest growing breed group and had relatively good carcass quality. Pietrain and its related crosses had the most lean muscle but the lowest meat quality. The HN (HAL negative, genotype Nn) individuals within the PPY and PNP groups grew more quickly and had higher meat quality scores and less muscling than HP (HAL positive, genotype nn) individuals. A second experiment with 40 pigs showed significant differences in fat concentration in the loin muscle between breeds (M, Y, and P) and between genotypes within the NP population (NP[HP] and NP[HN]). The phenotypic correlation between fat percentage and marbling was .59 (P less than .01). The NP(HP) had higher water percentage in lean than the NP(HN). The water percentage was negatively correlated with meat quality scores of color, firmness, and marbling with phenotypic correlations of -.10, -.23, and -.57 (P less than .01), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

An experimental comparison of equivalent terminal and rotational crossbreeding systems in swine: pig performance.

Eleven thousand forty-nine pigs produced from 934 litters using 262 rotational and F1 crossbred sows were used to study differences in pig weights, survival rates and pen average daily gain, daily feed intake, and feed conversion between pigs from equivalent three-breed rotational and three-breed terminal crossbreeding systems using Duroc, Yorkshire, and Landrace breeds. Pig weights at birth and 21 and 56 d and days to reach 100 kg did not differ (P > .10) between the terminal and rotational crossbreeding systems. However, ultrasound backfat thickness of pigs from the terminal crossbreeding system was .04 cm greater (P < .007) than that of pigs from the rotational crossbreeding system. Survival rate from 56 d to 100 kg was .8% greater (P < .01) for pigs from the terminal crossbreeding system than for those from the rotational crossbreeding system. The crossbreeding system had no effect (P > .10) on survival rate at birth, from birth to 21 d, from 21 to 56 d, or from birth to 100 kg. Differences between the two crossbreeding systems were nonsignificant (P > .20) for pen average daily gain, daily feed intake, and feed conversion. Breed composition of pigs was an important source of variation (P < .01) for pig weights at birth and at 56 d. Similarly, breed composition of the pig also affected ultrasound backfat thickness at 100 kg (P < .01), but not days required to reach 100 kg (P > .10). For survival traits, only survival rate from 56 d to 100 kg was influenced by breed composition of the pig.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of mass selection for increased weight at two ages on growth rate and carcass composition of Duroc-Landrace pigs.

Duroc boars from a line previously selected over five generations for 200-d weight and those from a randomly selected control line were mated to Landrace sows either from a line previously selected for increased 70-d weight or from a randomly selected pedigree control line. From these matings, 900 pigs were farrowed to examine the effects of crossing lines of pigs mass selected for weight at two ages on growth rate, survival, and carcass composition. A greater (P less than .01) percentage of pigs farrowed survived birth from control-line sows (.974) than from select-line sows (.914). Of those pigs born alive, a greater (P less than .05) percentage of pigs out of control-line sows survived to 21 d (.893) than out of select-line sows (.829). Pigs sired by select-line boars weighed 2.1 kg heavier (P less than .05) at 70 d than pigs sired by control-line boars. Pigs out of select-line sows weighed .11 kg less (P less than .10) at birth and .3 kg less (P less than .10) at 21 d of age but grew .026 kg/d faster (P less than .10) from 70 d to slaughter, weighed 3.9 kg more at 165 d of age (P less than .05), and reached 100 kg 7.0 d sooner (P less than .05) than pigs out of control-line sows. Carcasses from barrows sired by select-line boars had .29 cm more (P less than .10) fat at the 10th-rib than carcasses from barrows sired by control-line boars. Marbling scores were .31 unit greater (P less than .05) and muscle color scores were .25 unit greater (P less than .10) for carcasses from pigs out of select-line sows than for carcasses from pigs out of control-line sows. Selection for increased 70-d weight decreased age at 100 kg without increasing fat deposition. However, survival rates up to 100 kg were reduced. Mass selection for 200-d weight effectively increased 70-d weight, but fat thickness at 100 kg also increased.

An experimental comparison of equivalent terminal and rotational crossbreeding systems in swine: sow and litter performance.

Two hundred sixty-two rotational and F1 sows were mated to Duroc, Yorkshire, or Landrace boars to study performance differences between equivalent three-breed rotational and three-breed terminal crossbreeding systems. Matings were made to maximize heterosis. The sows were fed either 1.8 or 2.7 kg/d (2.25 and 3.15 kg/d in winter months) during gestation. These matings produced 934 litters to determine the effect of crossbreeding system, breed composition within crossbreeding system, and gestation feeding level on litter sizes and weights, sow weight and backfat thickness at weaning, daily feed intake of the sow during lactation, interval from weaning to estrus, and farrowing rate. Feeding level during gestation was not an important source of variation for any of the traits except litter birth weight and daily feed intake of the sow during lactation. Litter size marketed was .37 pigs/litter greater (P < .05) for the terminal-cross sows than those sows from the rotational crossbreeding system. Litter weights at birth and 56 d were .8 and 6.5 kg heavier (P < .02, .03), respectively, for the terminal crossbreeding system than for the rotational crossbreeding system. Sow weight and backfat thickness at weaning, daily feed intake during lactation, and farrowing rate were not affected (P > .10) by crossbreeding system. Weaning-to-estrus interval was 1.3 d shorter (P < .03) for sows in the terminal crossbreeding system than for those in the rotational system.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterosis losses resulting from incorrect matings in a three-breed rotational crossbreeding system in pigs.

Losses in individual heterosis were estimated using performance records from 11,700 pigs, 959 litters, and 377 pens of pigs from a three-breed rotational crossbreeding system. Three types of rotational crossbred sows were produced using the Duroc, Landrace, and Yorkshire breeds. Twenty-nine Duroc, 27 Landrace, and 25 Yorkshire boars were mated to 275 sows to produce pigs with theoretical levels of breed heterozygosity of 85.7, 71.4, or 42.9% depending on the genetic composition of the sows and boars. Orthogonal polynomials for unequally spaced levels were used to partition sum of squares for individual heterozygosity into linear and quadratic responses. There was a linear decline in 56-d litter weight (-.222 kg; P < .01) for each 1% decrease in heterozygosity. Responses for pig weight at 56 d (-.02 kg; P < .001) and age at 105 kg (.12 d; P < .001) were linear for each 1% decrease in heterozygosity. Likewise, post-weaning average daily gain ( -.0004 kg/d; P < .05) and feed conversion (-.0001; P < .01) responses were linear for each 1% decrease in heterozygosity. There were linear responses for survival rates of pigs born alive to 21 d (-.089%; P < .01), alive from 21 to 56 d (-.025%; P < .05), alive from 56 d and to 105 kg (-.042%; P < .05), and from birth to 105 kg (excluding stillborn pigs) (-.129%; P < .001) for every 1% decline in heterozygosity from 85.7 to 42.9%, respectively. Quadratic responses were not important for any of the traits examined (P > .05). Decreased productivity, resulting from decreased heterozygosity, can be expected when three-breed rotational crossbred sows are mated to boars from the wrong breed.

Comparisons of specific crosses from Duroc, Hampshire and Spot backcross sows.

One hundred 3/4 Duroc-1/4 Landrace (DDL), 3/4 Hampshire-1/4 Landrace (HHL) and 3/4 Spot-1/4 Landrace (SSL) backcross sows were randomly mated to Yorkshire boars to produce a total of 299 litters and 3,271 pigs to determine the effect of dam breeding on preweaning and postweaning performance of the pigs and litters. Litter sizes born and born alive were not significantly different among the three dam breeds studied. However, litter sizes alive at 21 d out of HHL sows were significantly larger than litter sizes out of SSL sows, while the litter sizes out of DDL sows were intermediate to the other two dam breeds. The DDL sows had significantly heavier litters at birth than did SSL sows, but the dam breeds did not differ in the weights of their litters at 21 and 42 d. Pigs out of DDL sows were heaviest at birth but weighed the least at 21 d, while pigs out of SSL sows were heaviest at 21 and 42 d of age. Pigs out of HHL sows weighed the least at birth and at 42 d. There were no significant differences among the dam breeds in the survival rate of their pigs. In the postweaning period, pigs out of HHL sows were the slowest growing and took the most days to reach 100 kg. Feed conversion and average daily feed consumption did not differ significantly among the three dam breeds studied.

Comparisons of specific crosses from Duroc-Landrace, Yorkshire-Landrace and Hampshire-Landrace sows managed in two types of gestation systems: pig performance.

Ten thousand one hundred sixty-nine pigs were farrowed in 844 litters that were produced by mating Duroc (D), Yorkshire (Y) and Hampshire (H) boars to Duroc-Landrace (DL), Yorkshire-Landrace (YL) and Hampshire-Landrace (HL) sows to study the effect of sire breed, dam breeding and gestation environment (pasture lots vs confinement stalls) on pig weights, survival rates and feed efficiency. Pigs sired by H boars were .05 kg heavier at birth than Y-sired pigs and .2 kg heavier at 21 d than Y- and D-sired pigs, but they were .6 kg smaller at 56 d. D-sired pigs grew .028 kg/d faster from 56 d to 100 kg and reached 100 kg approximately 5 d sooner than the Y- and the H-sired pigs. At birth, pigs out of DL sows were .21 kg heavier than pigs out of YL sows. Pigs out of HL sows grew .025 and .021 kg/d slower from 56 d to 100 kg compared with pigs out of DL and YL sows, respectively. Sows in the pasture gestation system produced pigs that were .05 kg heavier at birth than pigs out of sows in gestation stalls. Three-breed-cross pigs were .9 kg heavier at 56 d, grew .039 kg/d faster and took 7.9 fewer days to reach 100 kg than backcross pigs. The H sire breed had lower survival rates of pigs at 21 d and to 100 kg of those born alive (P less than .10), compared with pigs sired by D and Y boars. Pigs out of HL dams had the highest survival rates, whereas pigs out of YL sows had the lowest survival rates at birth, 21 d and at 100 kg. Three-breed-cross pigs averaged .025, .028 and .035 greater survival rates at birth, 21 d and 56 d than backcross pigs. Feed efficiency was most desirable in pens of pigs sired by H and D boars compared with pens of pigs sired by Y boars. However, pens of pigs with YL dams were more efficient than pens of pigs with HL dams.

Comparisons of specific crosses from Yorkshire-Landrace, Chester White-Landrace and Chester White-Yorkshire sows.

One hundred thirty Yorkshire-Landrace (YL), Chester White-Landrace (CL) and Chester White-Yorkshire (CY) F1 crossbred sows were mated randomly to Duroc (D), Hampshire (H), Farmers Hybrid 414 (FH414) or Farmers Hybrid 929 (FH929) boars. These matings produced 321 litters and 3,379 pigs, which were used to determine the effect of sire breeding and dam breeding on preweaning and postweaning performance of the pigs and litters. Litter size born alive, litter size at 56 d, litter weight at 56 d and litter weight per day of age to 100 kg were lower in litters sired by H boars than in those sired by D boars. However, sizes and weights of litters sired by D and H boars were not different from those sired by FH414 and FH929 boars. Litter sizes at birth were larger for litters out of CL and CY sows than those out of YL sows, but significant differences were not found for litter sizes at 21 d, 56 d or at marketing. Pigs sired by H boars were heavier at birth than pigs sired by D boars. Pigs sired by H boars did not differ significantly in weights at 21 and 56 d or in postweaning daily gains or days to 100 kg from pigs sired by D boars. Pigs out of CL dams were heavier at birth, 21 d and 56 d of age than pigs out of CY dams, but did not differ significantly in postweaning gains or in days to 100 kg. Pigs sired by D and H boars had less ultrasonic fat than pigs sired by FH414 and FH929 boars. Pigs sired by FH929 boars were leaner than pigs sired by FH414 boars.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of caffeine on blood creatine phosphokinase levels in swine.

Eight stress-susceptible and eight normal pigs weighing 35 to 50 kg were studied to determine if caffeine administration would trigger the stress syndrome and affect blood CPK levels. The pigs were littermates of Yorkshire descent. One gram of caffeine (dissolved in 10 ml of saline-sodium benzoate solution) was infused into the pigs through a jugular catheter at a rate of 1.0 ml/min. Blood samples were collected through the catheter before caffeine administration and at specific intervals up to 8 hr after the caffeine administration for the determination of blood creatine phosphokinase levels. The pigs were sacrificed approximately 48 hr after caffeine administration, and M. longissimus pH and reflectance values were obtained 45 min and 24 hr postmortem. Caffeine administration stimulated the development of the signs associated with the porcine stress syndrome in seven of the eight pigs genetically classified as stress-susceptible, and only one control pig exhibited an early sign of the stress syndrome, muscle tremors. Blood CPK levels did not differ significantly between the normal and stress-susceptible groups until visual signs of the stress syndrome were no longer observed (approximately 45 min after caffeine administration). Stress-susceptible pigs had significantly higher blood CPK levels than controls 45 min after the initial caffeine administration. Physical stress received by the pigs during transport and the stress from being held in a new environment resulted in a greater elevation of blood CPK than did the stress administered through the caffeine infusion.

The relationship of thyroxine secretion rate to growth of swine.

The thyroxine secretion rate of five barrows and five gilts (Yorkshire x Landrace) was monitored at 4-week intervals from 10 to 26 weeks of age. Thyroxine secretion rate was determined by injecting 131I-thyroxine (20 MUCi) and monitoring both thyroxine concentration in plasma and the decline of labeled thyroxine in plasma over the next 48 to 60 hours. The thyroxine secretion rate increased from 10 to 14 and 14 to 18 weeks of age but remained unchanged thereafter. The metabolic clearance rate of thyroxine increased significantly through 22 weeks of age 11.83, 2.98, 4.65, 6.32 and 6.90 leter/hr), as did the thyroxine distribution space (2.32, 4.32, 7.10, 90.72 and 10.36 liters. Body size (/.75) was correlated with thyroxine distribution space (r = .49) and thyroxine secretion rate (r = .44).