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)     

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.     

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.     

Effects of Duroc, Meishan, Fengjing, and Minzhu boars on productivity of mates and growth of first-cross progeny.

Meishan, Fengjing, Minzhu, and Duroc boars were mated by AI to crossbred gilts to compare the sire breeds for effects on productivity of their mates and performance of their progeny. Gilts were derived from a four-way cross of Chester White, Landrace, Large White, and Yorkshire. At weaning, litters sired by Meishan boars averaged 1.69 and 1.32 more pigs than those sired by Duroc and Minzhu boars, respectively (P less than .05). Pigs sired by Meishan and Fengjing boars averaged 1.2 to 1.8 more nipples than pigs sired by Duroc and Minzhu boars (P less than .05). Minzhu-sired pigs had a lower (P less than .05) survival rate to 14 and 28 d of age than did those sired by Meishan, Fengjing, and Duroc. Fengjing-sired pigs were heavier than Minzhu-sired pigs at birth and heavier than Minzhu- and Duroc-sired pigs at 14, 28, and 56 d of age (P less than .05). At 70 d of age, Meishan-sired pigs were heaviest, followed in order by Fengjing-, Duroc-, and Minzhu-sired pigs. At 98 d of age, Meishan-sired pigs were significantly heavier than all other breed groups and Duroc-sired pigs were significantly heavier than Minzhu-sired pigs. At 126 and 154 d of age, Duroc-sired pigs were heaviest, followed in order by Meishan-, Fengjing-, and Minzhu-sired pigs; all differences were significant. Average backfat thickness of gilts at 99.7 kg was least for Duroc-sired gilts and highest for Meishan-sired gilts. Sire breed groups did not differ significantly in feed efficiency from 70 to 98 d of age. Duroc-sired pigs were the most efficient (P less than .05) from 98 to 126 and 126 to 154 d of age. Results indicate that use of these Chinese breeds in crossbreeding programs will decrease performance traits. This decrease would have to be offset by increases in reproductive efficiency of Chinese sows, use of repartitioning agents, or other management techniques if Chinese pigs are to improve overall production efficiency of a crossbreeding program.     

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.     

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.     

Deposition rates and accretion patterns of intramuscular fat, loin muscle area, and backfat of Duroc pigs sired by boars from two time periods

A study was conducted to evaluate differences in performance and in carcass composition and tissue deposition rates between purebred Duroc pigs sired by boars currently available and those sired by boars from the mid-1980s. Two lines were developed by randomly allocating littermate and half-sib pairs of females to matings by current time period (CTP) or old time period (OTP) boars. Pigs from 2 replications were placed on test at a group mean BW of 63.5 kg. Serial ultrasonic measurements of the 10th-rib LM area (LMA), off-midline backfat (BF10), and intramuscular fat percentage (IMF) were collected every 2 wk in the first replication and used to assess deposition rate differences. Off-test ultrasonic LMA, BF10, and IMF measurements from a total of 557 pigs from 23 CTP sires and 232 pigs from 15 OTP sires across 2 replications and at a mean BW of 109 kg were evaluated. All available barrows and randomly selected gilts (n = 277) were sent to a commercial abattoir, and carcass measurements of 10th-rib backfat, last-rib backfat, last lumbar backfat, and LMA were collected. Analysis of serial backfat measurements revealed a linear relationship between back-fat and BW between 73 and 118 kg for pigs from both time periods. Pigs sired by OTP boars deposited more backfat (P < 0.05) at a faster rate than pigs sired by CTP boars over the entire test period. A curvilinear cumulative tissue deposition pattern was revealed for ultrasonically estimated LMA and IMF within both time periods. Significant linear and quadratic regression coefficient differences between lines indicated that pigs sired by CTP boars deposited more LMA and less IMF per kilogram of BW gain than pigs sired by OTP boars. Pigs sired by CTP boars had more LMA and less BF10 (P < 0.05), whereas pigs sired by OTP boars had more IMF (P = 0.04). Carcass evaluation revealed more (P < 0.01) carcass measurements of LMA and less (P < 0.05) carcass measurements of 10th-rib backfat, carcass measurements of last-rib backfat, and carcass measurements of last lumbar backfat for pigs sired by CTP boars. No difference (P > 0.05) between the time periods was found for ADG over the entire test period. Results from this study illustrate that significant progress in carcass composition has been realized within the Duroc breed since the mid-1980s. The long-term selection response in carcass leanness has also resulted in changes in deposition rates of correlated traits such as LMA and IMF.     

Survival and postweaning performance of pigs from sows fed fat during late gestation and lactation

Sows were fed a control corn-soybean meal gestation diet to d 80 of gestation. One group of sows (n = 25) continued receiving the control diet until the end of lactation, whereas two groups were placed on other treatments. One group (n = 27) was fed a diet containing 5% added solid fat pellets from gestation d 80 through lactation, whereas another group (n = 25) was fed a diet with 10% added solid fat pellet from gestation d 100 through d 14 of lactation. Feed supply was 2.27 kg/d during gestation and to appetite during lactation. Pigs from sows fed the control diet or 5% solid fat pellet diet were weaned with an age range of 22 to 28 d and immediately allotted in a 2 x 3 factorially designed 4-wk feeding trial. Pigs from these two sow groups were fed diets 1) without fat, 2) with 4.5% choice white grease or 3) with 5% solid fat pellet. Sow weight loss, backfat change and pig weights were not different at weaning among treatments. Survival rates of all pigs to 21 d averaged 90% with no significant differences between treatments. Pigs from fat-fed sows had more (P less than .05) glycogen per gram of liver, 41% more total liver glycogen and 16% more serum glucose at birth. Weanling pigs from fat-fed sows grew slower (P less than .05) than pigs from control sows. Supplemental fat during gestation increased liver glycogen of pigs, which should help survival, but the feeding of fat throughout lactation had a negative effect on ADG during a 4-wk postweaning period.     

Host determinants of pneumonia in slaughter weight swine

A prospective cohort study was undertaken in a farrow-to-farrow swine herd to describe patterns of pneumonia, and to identify host risk factors associated with the extent of pneumonic lesions in 2 weight groups of slaughter swine. The risk of coughing and pneumonic lesions increased with increasing age of pigs within the herd (P less than 0.0001). The age-specific prevalence of pneumonic lesions was low (2.7%) in pigs less than 16 weeks old at slaughter, but increased rapidly when pigs were between 16 and 22 weeks old (8.6 to 67.9%). After 22 weeks, the prevalence remained relatively constant at about 80%. Associations between possible risk factors and pneumonia were investigated by use of multiple-regression models. Age at weaning (less than 24 days) and birth weight (less than 1 kg) exerted small, but significant (P less than 0.002), effects on the extent of pneumonic lesions in pigs slaughtered at 30 to 50 kg live weight. For pigs slaughtered at 90 to 110 kg, pneumonic lesions were more extensive (P = 0.007) in pigs sired by Yorkshire boars than pigs sired by non-Yorkshire sires (Duroc, Hampshire, Chester White, or American Spotted). Other host factor variables including weaning weight and clinical diseases (atrophic rhinitis, diarrhea, and arthritis) were not associated with pneumonia extent in either weight group. Higher pneumonia percentages were also associated with reduced growth rates in the grower/finisher phase. Pigs sired by Yorkshire boars grew significantly (P less than 0.0001) more slowly from entry into shed 2 (mean, 38 kg) until about the time of exit (mean, 92 kg) than pigs sired by other breeds (747 g/d and 795 g/d, respectively).     

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.     

Influence of exogenous growth hormone and gestational diet on sow blood and milk characteristics and on baby pig blood, body composition and performance

Sows (14) and gilts (6) were used in a 2 X 2 factorial experiment to evaluate the effect of diet and highly purified porcine growth hormone (pGH) on sow metabolic status and baby pig survival parameters. Injections were 10 mg/d pGH (GH) or sham control (SH). Diets consisted of a glucose-fat energy source (GF) or control (C). Treatments were administered the last 21 d before parturition (P). Serum GH concentrations were significantly elevated on d -19 P and d -4 P in sows receiving GH injections. Significantly elevated serum glucose and insulin concentrations were concomitantly observed in GH-treated sows, suggesting that the animals had developed a state of insulin resistance. Serum free fatty acids (FFA) were greater (P less than .01) on d -19 P for sows fed the GF diet. Fasted pigs from GH-C dams had greater (P less than .06) mean serum glucose concentrations than pigs from SH-C, SH-GF or GH-GF dams. Pigs from GH-injected sows had more (P less than .01) total body lipids at birth and tended to have increased mean FFA concentrations when compared to SH pigs. However, birth weight, number born live, number born dead, number that died and survival to 21 d were not affected by dam's injection or dietary treatment. Growth hormone injections resulted in a diabetogenic state in gestating sows and led to improved traits related to baby pig blood glucose homeostasis, including increased blood glucose, increased body lipids and a tendency toward increased liver glycogen concentrations. Injection X diet interactions indicate that dietary energy source should be regarded in future growth hormone experiments.     

Effect of birth and fraternal litter size and cross-fostering on growth and reproduction in swine

Twelve hundred fifty-one pigs from six farrowings (FGRP) were classified within a FGRP by their birth litter size (BL- = below average and BL+ = above average), randomly allotted to nursing litter sizes of 6 or 12+ pigs/sow (NL- vs NL+) and reared by their own or foster dams (XF- vs XF+). Pigs were weighed at birth, 21 d and when near 105 kg. A random sample of 40 gilts per FGRP was retained for observation of pubertal age and primipara conception. Twenty-four gilts per FGRP were farrowed and rebred for a second parity. Pigs born in large litters were younger at 105 kg than those born in small litters (189 vs 196 d +/- 1.4); no other differences (P greater than .05) were observed for BL. Pigs reared in larger litters had lower survival rate from birth to weaning (79 vs 86% +/- 1), had slower weight gains to 21 d of age (5.3 vs 6.6 kg +/- .17) and were older at 105 kg (195 vs 190 d +/- 1.4) than those reared in small litters (P less than .04). Cross-fostered pigs were slower gaining to 21 d (5.9 vs 6.1 kg +/- .14) and were older at 105 kg (195 vs 191 d +/- 1.4) than pigs not cross-fostered pigs (P less than .02). Growth beyond 105 kg and pubertal age were unaffected by any factor studied (P greater than .05). Although size of birth litter did not affect (P greater than .05) any reproductive trait, an interaction between litter size and farrowing group was detected.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of birth weight and feeding of supplemental milk replacer to piglets during lactation on preweaning and postweaning growth performance and carcass characteristics

The effects of piglet birth weight and liquid milk replacer supplementation of piglets during lactation on growth performance to slaughter weight was evaluated in a study carried out with 32 sows (PIC C-22) and their piglets (n = 384; progeny of PIC Line 337 sires). A randomized block design with a 2 x 2 factorial arrangement of treatments was used. Treatments were birth weight (Heavy vs Light) and liquid milk replacer (Supplemented vs Unsupplemented). The study was divided into two periods. At the start of period 1 (birth to weaning), pigs were assigned to either Heavy or Light (1.8 [SD = 0.09] vs 1.3 kg [SD = 0.07] BW, respectively, P < 0.001) litters of 12 pigs and half of the litters were given ad libitum access to supplemental milk replacer from d 3 of lactation to weaning (21 +/- 0.2 d). In period 2 (weaning to 110 kg BW), a total of 308 pigs were randomly selected from within previous treatment and sex subclasses and placed in pens of four pigs. Pigs were given ad libitum access to diets that met or exceeded nutrient requirements. Pigs in heavy litters were heavier at weaning (6.6 vs 5.7 kg BW; SE = 0.14; P < 0.001) and tended to have more pigs weaned (11.4 vs 10.9 pigs/litter; SE = 0.21; P = 0.10). After weaning, pigs in the Heavy litter had greater ADG (851 vs 796 g; SE = 6.7; P < 0.001) and ADFI (1,866 vs 1,783 g; SE = 17.6; P < 0.001), similar gain:feed (0.46 vs 0.45; SE = 0.003; P > 0.05), and required seven fewer days (P < 0.001) to reach slaughter weight compared to pigs in the Light treatment. Feeding supplemental milk replacer during lactation produced heavier pigs at weaning (6.6 vs 5.7 kg BW; SE = 0.14; P < 0.001) and tended to increase the number of pigs weaned (11.4 vs 10.9 pigs/litter; SE = 0.21; P = 0.10) but had no effect (P > 0.05) on growth performance from weaning to slaughter. However, pigs fed milk replacer required three fewer days (P < 0.01) to reach 110 kg BW. Sow feed intake and BW loss during lactation were not affected (P > 0.05) by either birth weight or milk replacer treatment. In conclusion, birth weight has a substantially greater impact on pig growth performance after weaning than increasing nutrient intake during lactation.     

Effects of Duroc, Meishan, Fengjing, and Minzhu boars on carcass traits of first-cross barrows.

Duroc, Meishan, Fengjing, and Minzhu boars were mated to crossbred gilts during two breeding seasons. From each sire breed group each season, six pens of approximately eight barrows each were slaughtered. A pen of pigs from each sire breed group was slaughtered at 7-d intervals from 168 to 203 d of age each season. Breed of sire effects were significant for all age-adjusted carcass traits except carcass length, fat thickness at the last rib, color score, and firmness score. At 184 d of age, Duroc crosses had the heaviest (P less than .05) slaughter and carcass weights; Minzhu crosses were lighter (P less than .05) than Meishan crosses but not lighter than Fengjing crosses. Differences among age-constant traits reflect differences in BW. After adjustment to a constant carcass weight of 78 kg, the three Chinese breeds had very similar carcass characteristics. Carcasses sired by Durocs had significantly less backfat and larger longissimus muscle area than carcasses sired by the Chinese breeds. Weight of each trimmed wholesale lean cut and their total weight were significantly higher for Duroc crosses than for Chinese crosses. Breed of sire means did not differ significantly for belly weight, but Duroc crosses had less (P less than .05) weight of leaf fat. Relative to Chinese crosses, longissimus muscles from Duroc crosses had more marbling (P less than .05). Sire breed groups did not differ significantly for color or firmness score. Pigs sired by Meishan, Fengjing, and Minzhu produced carcasses with significantly less lean content at a carcass weight of 78 kg than did pigs sired by Duroc.     

Genetic and maternal effects on pig weights, growth and probe backfat in diallel crosses of high- and low-fat lines of swine

Two Duroc and two Yorkshire lines of pigs that had been selected at Beltsville Agricultural Research Center for 12 and 10 generations, respectively, for either thinner or thicker backfat were mated to produce all possible pure lines and reciprocal crosses in 1967, 1969 and 1970. Data for littermate gilts and barrows from 136 litters were analyzed to estimate genetic and maternal influence on individual pig weights at birth, 21 d, 56 d and 140 d of age; age at 79.4 kg; average backfat thickness at 79.4 kg and postweaning average daily gain (56 d to 79.4 kg). Pure-line gilts differed among breed-lines (P less than .05 or P less than .01) for all traits except weight at 56 d. Gilts of the two low-fat lines were heavier than gilts of the two high-fat lines through 56 d of age, but Yorkshire low-fat gilts were lightest at 140 d, were oldest at 79.4 kg and had the slowest daily gain, in addition to the least backfat. The Duroc low-fat line gilts were heaviest at 140 d, youngest at 79.4 kg and were second thinnest in backfat. Among pure-line barrows, the low-fat lines were heaviest at birth, at 21 d and at 140 d and were thinnest in backfat. Line-cross gilts were heavier than pure-line gilts at all four ages, were younger at 79.4 kg and higher in daily gain. Among barrows, line crosses were heavier in all weights except at 21 d, were younger at 79.4 kg and were higher in daily gain than pure lines. Differences between pure lines and line crosses in backfat were not significant for either sex. Heterosis varied from 6.5 to 16.7% among weights and growth traits. Pigs of both sexes differed among breed-lines in general combining ability for all traits except 21-d weight, and differed in maternal ability for weights through 56 d and for backfat. Specific combining ability (SCA) was significant only for intra-breed crosses for weight at 21 d, and for inter-breed, intra-line crosses for 21- and 56-d weights and for age at 79.4 kg among gilts, with no significant effects in SCA for any trait among barrows. General combining ability was not correlated with maternal effects for any trait except 21-d weight, for which they were positively correlated (r greater than .80).     

Long-term effects of corn gluten feed on the reproductive performance and weight of gestating sows

Corn gluten feed (CGF) was evaluated as the primary energy and protein source for gestating sows. Eighty gravid multiparous Yorkshire x Landrace sows were assigned randomly to three treatment groups for the entire three-parity trial. The gestation treatment diets were 1) corn-soybean meal fed at 1.8 kg/d (control), 2) CGF plus soybean meal fed at 2.3 kg/d (CGF-low) and 3) CGF plus soybean meal fed at 2.6 kg/d (CGF-high). The CGF diets contained 92.2% and 93.7% CGF, respectively. Feeding levels of Diets 2 and 3 were based on the assumption that CGF had 80% and 70% of the net energy value of corn, respectively. All sows had ad libitum access to a conventional corn-soybean meal diet during lactation and were fed 3.2 kg/d during breeding. Intakes of gestation treatment diets were increased 25% during winter months. Based on litter size and weight, the performance of sows fed CGF did not differ from that of the sows fed the control diet. Mean number of pigs at birth and 21 d (weaning) for the three parities were: (control) 10.16, 7.65; (CGF-low) 11.30, 8.44; (CGF-high) 10.73, 8.13, respectively. Pigs from CGF-fed sows were smaller at birth (P less than .05), but subsequent pig weights did not differ. Mean pig birth and 21-d weights for the three parities were: (control) 1.44, 5.18; (CGF-low) 1.30, 4.84; (CGF-high) 1.31, 5.01 kg, respectively. CGF-low sows weighed less (P less than .01) at d 109 of gestation than did the control and CGF-high sows, which did not differ in weight.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of additional feed during late gestation on reproductive performance of sows: a cooperative study

A cooperative research study involving 1,080 litters was conducted at eight stations to determine the effects of additional feed during the last 23 d of gestation on reproductive performance of sows and on preweaning performance of their pigs. Primiparous and multiparous sows were fed fortified corn- or sorghum-soybean meal diets (14% crude protein). Control sows received 1.82 kg/d from March through November and 2.27 kg/d from December through February. Treated sows were fed an additional 1.36 kg of feed/d from d 90 of gestation to farrowing. Sows were allowed to consume the same diet ad libitum during a 21-d lactation. Additional feed in late gestation resulted in greater (P less than .001) sow weight gain from d 90 to d 110 of gestation (16.8 vs 9.0 kg) and greater (P less than .001) parturition-lactation weight loss (21.3 vs 16.4 kg). Total weight gain from breeding to 21 d of lactation favored sows that received extra feed (27.5 vs 22.7 kg; P less than .001). Sows receiving extra feed had more live pigs at farrowing (10.05 vs 9.71, P = .06) and at 21 d postpartum (8.35 vs 8.06, P = .09), and the pigs were heavier at birth (1.48 vs 1.44 kg, P = .003) and at 21 d (5.37 vs 5.20 kg, P = .006). Lactation feed intake and number of days from weaning to estrus were not affected by treatment. The results indicate that additional feed in late gestation improves reproductive performance in sows. In this study, the cost of an additional 31 kg of feed/sow was more than offset by the value of the additional sow weight gain (approximately 5 kg), the additional .3 of a pig/litter at weaning and the additional 2.6 kg of total litter weaning weight.     

Population parameter estimates for performance and reproductive traits in Polish Large White nucleus herds

Performance test records from on-farm tests of young Polish Large White boars and reproductive records of Polish Large White sows from 94 nucleus farms during 1978 to 1987 were used to estimate population parameters for the measured traits. The number of boar performance records after editing was 114,347 from 3,932 sires, 21,543 dams, 44,493 litters and 1,075 herd-year-seasons. Reproductive performance records of sows involved 41,080 litters from 2,348 sires, 18,683 dams and 1,520 herd-year-seasons. Both data sets were analyzed by using restricted maximum-likelihood programs. The model used for the performance records included fixed herd-year-seasons, random sires, dams and error effects, and covariances for the year of birth of sire and year of birth of dam. The model used for the reproduction data set was the same as the performance data with parity as an additional fixed effect. Estimated heritabilities were .27, .29, .26, .07, .06, .06 for average daily gain standardized to 180 d (ADG), backfat thickness standardized to 110 kg BW (BF), days to 110 kg (DAYS), litter size at birth born alive (NBA), litter size at 21 d (N21) and litter weight at 21 d (W21), respectively. Estimated common environmental effects for the same traits were .09, .10, .09, .06, .07 and .08, respectively. Genetic correlations were .25 (ADG and BF), -.99 (ADG and DAYS), -.21 (BF and DAYS), .91 (NBA and N21), .68 (NBA and W21) and .80 (N21 and W21). The respective phenotypic correlations were .23, -.99, -.20, .88, .75, .86. These population parameters for Polish Large White pigs are similar to those for breeds in other countries.     

The effect of two different feed levels on the development of the reproductive organs in boars.

The aim of the present investigation was to study the development of the reproductive organs in boars fed restrictively and fed ad libitum. A total of 120 boars were purchased by the experimental station at 20 kg live weight. Three groups of 4 litter mates were selected after each of 10 A.I. boars (7 Swedish Landrace and 3 Swedish Yorkshire). The dams were unselected sows from pigletproducing herds. Two boar pigs from each litter were allocated at random among 2 treatment groups. One group ( = N) was fed restrictively and the other group (=A) ad libitum. The boars were slaughtered at 90 kg or at 120 kg live weight. The reproductive organs were removed at slaughter and examined.The ad libitum fed boars were about 2 weeks younger at slaughter than those fed restrictively (16.5 and 13.7 days respectively for the 2 weight classes). The weights of the testes were somewhat higher for ad libitum fed than for restrictively fed boars. Out of 94 examined pairs of testes, epididymides, seminal vesicles and bulbo-urethral glands, the left was heavier than the right in 68%, 62%, 48%, and 36%, respectively. Fewer (4/23) ad libitum fed than restrictively fed boars (9/26) had reached puberty at 90 kg live weight. Age at puberty thus seems to be less variable than body size in boars.     

Effects of age and diet on the development of the pancreas and the synthesis and secretion of pancreatic enzymes in the young pig

Effects of age and diet composition on amylase, trypsin and chymotrypsin activities in the pancreas and intestinal contents, pancreas weights and body weights were determined from birth to 56 d. A total of 120 pigs, five to seven pigs/litter from 18 litters, were slaughtered at birth, 14, 27, 29, 31, 42 and 56 d. Litters were allotted to dietary treatments (corn-soy, A; corn-soy + 20% dried whey, B; corn-soy + 5% lard, C) and offered these diets as creep feed at 14 d. All pigs were weaned at 28 d, placed in elevated nursery pens and fed their respective diets. Total activities of amylase, trypsin and chymotrypsin in the pancreas and small intestine increased (P less than .05) with age. Both trypsin and amylase activities, measured per kilogram body weight or gram pancreas weight, were low at 29 d in the intestine and increased to 56 d. Pigs on diet B had the highest level of trypsin and chymotrypsin in the intestinal contents (P less than .05). Trypsin activity in the pancreas (units/kg body weight) was lowest (P less than .05) for pigs on diet B and highest (P less than .05) for those on diet C (units/g pancreas and units/kg body weight). Amylase activity (units/kg body weight) was lower (P less than .05) in the pancreas for pigs on diet B than for those on diets A and C. Pigs on diet A had lower (P less than .01) intestinal amylase activities than those on diets B and C. Enzyme activities in the intestinal contents and pancreas were low following weaning. In the pancreas, activities decreased at 31 d.(ABSTRACT TRUNCATED AT 250 WORDS)