Responses to 19 generations of litter size selection in the Nebraska Index line. I. Reproductive responses estimated in pure line and crossbred litters

Our objective was to estimate responses in reproductive traits in the Nebraska Index line (I) after 19 generations of selection for increased litter size. Responses were estimated in dams producing pure line, F1, and three-way cross litters. A total of 850 litters were produced over six year-seasons, including 224 pure line litters, 393 F1 litters produced from I and C females mated with Danbred NA Landrace (L) or Duroc-Hampshire (T) boars, and 233 litters by F1 L x I and L x C females mated with T boars. Contrasts of means were used to estimate the genetic difference between I and C and interactions of line differences with mating type. Farrowing rates of lines I (u = 91.0%) and C (u = 92.8%) did not differ. Averaged across all genetic groups, mean number born alive per litter was 10.1 pigs, and number and weight of pigs weaned per litter, both adjusted for number nursed and weaning age of 12 d, were 9.7 pigs and 34.4 kg, respectively. Averaged across mating types, direct genetic effects of I were greater than C (P < 0.05) for total born (3.53 pigs), number born alive (2.53 pigs), number of mummified pigs (0.22 pig), and litter birth weight (2.14 kg). The direct genetic effect of line I was less than C (P < 0.05) for litter weaning weight (-1.88 kg). Interactions of line effects with crossing system were significant (P < 0.05) for total number born, number of stillborn pigs, number weaned, and litter weaning weight. In pure line litters, I exceeded C by 4.18 total pigs and 1.76 stillborn pigs per litter, whereas the estimate of I-C in F1 litters was 2.74 total pigs and 0.78 stillborn pig per litter. The contrast between I and C for number weaned and litter weaning weight in pure litters was 0.32 pig and -0.28 kg, respectively, compared with 0.25 pig and -2.14 kg in F1 litters. Crossbreeding is an effective way to use the enhanced reproductive efficiency of the Index line.     

The performance of gilts in a new group housing system: endocrinological and immunological functions.

The effect of a new group housing system on performance (132 gilts and litters) and endocrinological (35 gilts) and immunological functions (28 gilts) was studied. Animals were randomly assigned to a conventional system (control), involving greater than 2 mo in individual stalls, or to the Hurnik-Morris (H-M) housing system, involving continuous housing in small groups, for breeding-gestating swine. The gilts were reared throughout gestation in their respective housing systems and moved 3 to 5 d prefarrowing to a common farrowing facility. Various production data were collected, including sow weight and backfat measurements, number of pigs born, number born alive, number weaned, litter birth weight, and litter weaning weight. An adrenal function test using dexamethasone pretreatment and ACTH1-24 challenge was imposed on gilts 5 d prebreeding and once between d 81 to 87 of gestation. Plasma progesterone was measured at the same time. Immune function was measured by serum antibody response to hen egg white lysozyme (HEWL) and delayed-type hypersensitivity (DTH) to tuberculin. Gilts reared in the H-M housing system exhibited a number of pigs weaned per litter and litter weaning weights comparable to the number and weights in the control system (7.3 +/- .33 vs 6.9 +/- .38, P = .421 and 56.9 +/- 2.42 kg vs 51.3 +/- 2.76 kg, P = .132, respectively). Prefarrowing and weaning backfat measurements were significantly reduced in group-housed gilts (15.8 +/- .45 mm vs 17.8 +/- .55 mm, P = .005 and 14.6 +/- .4 mm vs 16.2 +/- .42 mm, P = .008, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

A field study of the associations between behaviors and reproductive performance in lactating sows

The present study examined factors associated with suckling, eating and postural behaviors (standing, lying and sitting) and the relationships between sow behaviors and reproductive performance. A commercial farrowing-to-finish farm with approximately 300 female pigs was visited eight times for 3 years to record sow behaviors using time-lapse video recorders for 24 hr. The lactational and postweaning reproductive performances of each sow were recorded using a recording software system. Statistical models were built to investigate the factors associated with each behavior. Regression analyses were performed to determine the associations between behavior measurements and adjusted 21-day litter weights (A21d-Wt), weaning-to-first-mating intervals (WMI) and occurrence of >or= 2 dead piglets during lactation. The means of suckling intervals and frequency of postural changes of the 145 recorded sows were 47.5 +/- 0.59 min and 86.8 +/- 2.97, respectively. As parity increased from 1 to >or= 4, the suckling interval and total standing duration increased (P<0.05). The number of nursing piglets and observation days 4 to 21 of lactation were not associated with the suckling intervals. A longer duration of lactation was associated with a longer total standing duration and a higher frequency of postural changes (P<0.05). Shorter suckling intervals were associated with heavier A21d-Wt (P<0.05). Each change in postural behavior increased the likelihood of occurrence of >or= 2 dead piglets during lactation (P<0.05). No postural or suckling behaviors were associated with WMI. Eating behavior was not associated with any reproductive performance. In conclusion, sow behaviors during lactation were related to lactational performance but were not related to postweaning reproductive performance.     

Lifetime reproductive and financial performance of female swine

OBJECTIVE: To evaluate reproductive and financial performance for commercial swine herds grouped on the basis of pattern of removal of female swine. DESIGN: Cohort study. SAMPLE POPULATION: 25 swine herds. PROCEDURES: Lifetime reproductive productivity was summarized as number of pigs weaned per herd day per mated female and as number of herd days per pig weaned per mated female. Factors associated with these 2 measures were determined by use of linear regression. Financial data from a commercial database were used to estimate maximum number of parities at removal associated with profitability. Sensitivity analysis was used to simulate how variations in daily maintenance cost and value per weaned pig would influence profitability. RESULTS: Mean number of pigs weaned per herd day per mated female was 0.054; mean number of herd days per pig weaned per mated female was 20.2. Both these measures were associated with proportion of nonproductive days during herd life, preweaning mortality rate per litter weaned, mean lifetime number of pigs born alive per litter weaned, and mean lifetime lactation duration. Maximum parity at time of removal associated with profitability ranged from 5 to 8. Daily maintenance costs per female had a greater impact on lifetime profitability than did value per weaned pig. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that lifetime reproductive and financial performance is optimized among swine herds that have higher proportions of high-parity females.     

杂谈猪的遗传改良——冻精与批次分娩对大白猪繁殖性状遗传参数估计或繁殖性能的影响

本研究旨在分析影响大白猪繁殖性能因素(批次管理体系和精液类型)与遗传参数估计,为目标群体的遗传评估及生产管理奠定理论基础。利用DMU和ASREML软件分析2 026头大白母猪共4 512窝繁殖记录,涉及4个繁殖性状(总产仔数、产活仔数、21日龄窝重和断奶仔猪数)。结果表明:大白猪4个繁殖性状的遗传力估计值均在0.10左右,各性状间均成强正遗传相关(0.54以上)。精液类型(鲜精和冻精)效应对断奶仔猪数和21日龄窝重影响不显著(P>0.05),对总产仔数和产活仔数影响显著(P<0.05),其中冻精在总产仔数和产活仔数上较鲜精均少1头左右(P<0.05)。批次管理体系研究表明,由单周批次管理体系转变为4周批次管理体系后,母猪繁殖性能有所下降,产活仔数、断奶仔数猪和21日龄窝重分别下降0.51头、0.61头和10.13 kg。     

撒坝猪专门化母系繁殖性状的相关与通径分析

利用撒坝猪专门化母系 7个世代共 576头母猪的繁殖性能数据 ,对总产仔数 (x1 )、活产仔数 (x2 )、初生窝重 (x3)、 2 0日龄窝重 (x4 )、断奶窝重 (x5)、育成率 (x6 )和断奶仔数 (y) 7个繁殖性状进行了相关和通径分析 ,并在此基础上建立了估计断奶仔数的最优回归方程。结果表明 ,撒坝猪专门化母系的繁殖性能在经过 7个世代的选育后 ,获得了明显提高。各繁殖性状间在表型值上都存在不同程度的相关 ,其中以总产仔数与活产仔数的相关程度最高 (r=0 92 0 1 ) ,其次为 2 0日龄窝重与断奶仔数 (r=0 82 88) ,而初生窝重与育成率间的相关系数最低 (r=0 0 381 )。在所分析的 7个性状中 ,除了总产仔数和活产仔数与育成率间为负相关外 ,其余性状间均为正相关。所建立的估计断奶仔数的多元回归方程为 :y=- 6 1 1 90 +0 6986x2 +0 0 33 7x4 +0 0 0 4 8x5+0 0 71 8x6 。     

Estimation of lifetime productivity of female swine

OBJECTIVE: To develop estimates of lifetime productivity for breeding female swine calculated longitudinally during time in the breeding herd, and to compare estimates of lifetime productivity for female swine removed from the herd at different parities. DESIGN: Retrospective cohort study. ANIMALS: 9,416 breeding female swine from 29 herds. PROCEDURE: A frequency distribution for parity at the time of removal was generated. Estimates of lifetime productivity (lifetime nonproductive days [NPD], lifetime NPD as a proportion of herd life, total number of pigs born per litter weaned, number of pigs born alive per litter weaned, number of pigs weaned per litter weaned, number of NPD per year in the herd, number of litters weaned per year in the herd, and number of pigs weaned per year in the herd) were calculated for females with parity > or = 1 at the time of removal. RESULTS: For 58% of all females, parity at the time of removal was < or = 3. On average, 20.7% of herd life was spent in nonproductive activities, but the proportion of herd life that was nonproductive decreased significantly as parity at the time of removal increased. Number of NPD per year in the herd decreased and number of litters weaned per year in the herd and number of pigs weaned per year in the herd increased significantly as parity at the time of removal increased. CLINICAL IMPLICATIONS: Higher parity at the time of removal from the herd is associated with improved lifetime productivity for female swine. Parity at time of removal is commonly used as an approximation for lifetime productivity, but it does not take into account the impact of NPD, especially NPD during early reproductive cycles.     

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)     

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)     

Performance of gestating sows in bedded hoop barns and confinement stalls

The effects of gestation housing systems on sow and litter performance were evaluated for 2.5 yr in southwest Iowa. Gestation housing system treatments were as follows: 1) individual gestation stalls in a mechanically ventilated confinement building with a partially slatted floor and a manure flush system and 2) group pens with individual feed stalls in deep-bedded, naturally ventilated hoop barns. In all, 957 litters from 353 sows were evaluated. Number of pigs born alive per litter differed for the 2 housing treatments (P = 0.002). Sows gestated in hoop barns gave birth to more live pigs per litter (10.0 +/- 0.2 pigs) than sows gestated in stalls (9.3 +/- 0.2 pigs). Preweaning mortality was not different for the 2 housing treatments (P = 0.70). Cross-fostering was done to equalize litter size within 24 h of birth, which resulted in an equal number of weaned pigs per sow (P = 0.50) regardless of gestation housing treatment. The weaning-to-breeding interval was different (P = 0.01), with sows kept in stalls (4.3 +/- 0.6 d) returning to estrus sooner than sows gestated in hoop barns (6.0 +/- 0.6 d). These results indicate that gestating sows can be housed as groups in deep-bedded hoop barns equipped with individual feeding stalls and will perform comparably to gestating sows housed in confinement systems with individual gestation stalls.     

Effect of dietary fibre on reproductive performance of sows during the first two parities

The aim of this study was to investigate the effect of dietary fibre on reproductive performance during the first two parities. Gilts were randomly allocated to receive three fibrous diets from days 1-90 of gestation, including low fibre [low fiber (LF), 10.8% neutral detergent fiber (NDF), n=132], middle fibre [middle fiber (MF), 15.8% NDF, n=132] and high fibre diet (HF, 20.8% NDF, n=135), until completion of the second parity. Response criteria included backfat measurements, litter size and pig weight at parturition and day 22 of lactation, weaning-oestrus-interval, oestrus rate, sow farrowing and culling rate, uniformity of newborns and relative organ weights. The results showed sows fed LF diet in parity 1 gained more backfat (p<0.05) during gestation but lost more (p<0.05) during lactation than sows fed HF diet. Furthermore, sows fed LF diet farrowed more pigs (+0.7-1.1 pigs, p<0.05) and pigs born alive (+1.0 pigs, p<0.05) relative to sows fed HF diet. Likewise, sows fed LF and MF diets had greater litter weights at parturition (both p=0.06) and day 22 after lactation (both p<0.05). In parity 2, yet, it was MF diet to increase both total pigs born and pigs born alive (+0.9-1.1 pigs, p<0.05) and litter weight (p=0.05) relative to other diets. After 22 d of lactation, intriguingly, sows fed HF diet had most pigs alive (p<0.01-0.07) and heavier litter weight (p=0.07 or 0.2). Feeding HF diet also increased internal organs weight of newborns (p<0.05). Collectively, feeding LF and MF diets had beneficial effects on litter weight at parturition and day 22 of lactation in parity 1, and feeding MF diet until parity 2 was able to improve litter size and weight at parturition, but this positive effect disappeared after 22 days of lactation, instead feeding HF diet showed the optimal litter performance.     

Influence of pig substitution on milk yield, litter weights, and milk composition of machine milked sows.

This study was conducted to 1) determine milk yield of sows that were machine milked up to four times daily; 2) determine the effect of pig substitution on milk yield; 3) assess litter weight changes for sows that are milked; and 4) determine milk composition. Eight sows were milked four times daily to d 51 postpartum. Sows either maintained their own litter or had a week-old replacement litter to replace 25-d-old pigs. Individual gland milk yields were obtained on random days throughout lactation, and different diameter and weighted teat cups were rotated so that all glands received all combinations. Composite milk samples were analyzed for fat, protein, and somatic cells. Milk yields peaked at about 19 d postpartum and declined to 45 d postpartum in sows with their own litter, whereas milk yields peaked earlier and had a more dramatic decline after fostering of a younger litter. Litter weights were 17.1 +/- 1.0 kg at farrowing with 13.6 +/- .6 pigs born alive. Final litter weights were 34.4 +/- 11.7 kg for sows with replacement litters and 74.4 +/- 13.5 kg for sows with their own litters, and numbers of pigs weaned were 6.5 +/- 1.3 and 9.7 +/- 1.5, respectively. Milk fat was influenced by route of oxytocin administration (6.53 +/- .12 for i.v. vs 7.21 +/- .19% for i.m. administration; P < .05). Milk fat percentage was highest on d 2 and declined to 13 d postpartum. Milk protein was influenced by time of day of milking (lowest at the fourth milking, 5.57 +/- .11%) and followed a pattern similar to that for milk fat. Milk protein was affected in a linear manner by milk yield, with highest protein associated with lowest milk yields. Somatic cells in milk were influenced by litter replacement (P < .05) and oxytocin administration (P < .01). There was a linear increase in somatic cells from about 8 x 10(6) cells/mL milk at d 2 to more than 12 x 10(6) cells/mL milk at d 51 postpartum. These results show that pig replacement affects the amount of milk obtained. Moreover, milk composition changes throughout lactation. However, milk removal from sows has a severe impact on litter weight gains, and in systems where sow's milk is needed for commercial purposes, pig supplementation is necessary.     

Genetic and phenotypic parameters for sow productivity

Data from 609 purebred Yorkshire, Hampshire and Duroc litters were utilized to obtain genetic and environmental parameter estimates for litter number and weight traits at birth, 21 d (first creep) and 42 d (weaning) considered as traits of the sow. Differences among paternal half-sib sets of sows were analyzed. Heritability estimates from this study were .26 +/- .12, .28 +/- .12 and .30 +/- .12 for litter size at birth, 21 and 42 d and .54 +/- .13, .17 +/- .11 and .15 +/- .11 for litter weights at those times, respectively. These estimates indicated that the dam's genetic contribution to litter weight was higher for prenatal growth than during nursing. The heritabilities for litter size were encouraging for within breed selection. Genetic correlations among litter sizes and genetic correlations among litter weights at birth, 21 and 42 d were large and positive. Large, positive genetic correlations also were found between litter size and weight at each of the three times. Negative correlations between litter size and average pig weight at both birth and 21 d and between litter size at birth and average pig weight at 21 d indicated that larger litters were associated genetically with smaller pigs. Phenotypic and environmental correlations generally indicated the same associations.     

The National Pork Producers Council Maternal Line National Genetic Evaluation Program: a comparison of six maternal genetic lines for female productivity measures over four parities

Litter (n = 8,424) and female performance records were collected in two breed-to-wean production units in order to evaluate genetic line differences for sow longevity and maternal performance over four parities. Lines evaluated were American Diamond Genetics, Danbred North America, Dekalb-Monsanto DK44, Dekalb-Monsanto GPK347, Newsham Hybrids, and National Swine Registry. Females within a line were derived from a minimum of 65 sires, 197 dams (three dams per sire), and a maximum of three daughters per dam, except in the GPK347, which were produced using semen from 12 Nebraska Index boars mated with Dekalb-Monsanto Line 34 females. All lines expressed 100% maternal heterosis. Mixed model statistical procedures were used with fixed effects including genetic line, parity, production unit, and two-way interactions. Random effects included a contemporary week of production and female for repeated records. Lactation length (average 15 d) was included as a linear covariate where appropriate. In total, 3,599 females entered as early-weaned pigs, 3,283 entered the breeding herd, 2,592 farrowed at least a single litter, and 1,656 and completed four parities. Line (P < 0.001) and parity (P < 0.001) effects were observed for virtually all traits measured. Ranges of genetic line differences averaged across parities were 1.76 pigs for total born, 1.45 pigs born alive, and 0.31 stillborn pigs per litter. Ranges of line differences in total and live litter weight were 1.4 and 1.3 kg, respectively. Ranges among lines, within Parities 1 through 4, for litter size at weaning were 0.56, 1.08, 0.91, and 0.64 pigs per litter, respectively. Line differences for weight (33.8 kg) and backfat depth (6.4 mm) at farrowing, lactation feed intake (8.7 kg), weight loss (5.0 kg), and backfat loss (0.87 mm) were observed. Extended wean-to-estrus interval was related to variation in weight, feed intake, and backfat loss in all lines except the GPK347. The GPK347 females farrowed and weaned the largest number of pigs, ate less feed in lactation, and lost more backfat and weight during lactation, yet they had the largest litters and the shortest wean-to-estrus intervals. Line x parity interactions existed for many traits due to small rank changes, but in general, the high- and low-ranked lines did not change. Genetic line differences in reproductive efficiency through four parities exist and must be recognized when choosing a female line.     

Effect of drinker type on water intake and waste in newly weaned piglets

During the first few days after weaning, pigs often experience BW loss as they adapt to eating solid food. During this time period, they are also known to drink excessively and develop abnormal oral behavior such as belly nosing. The excessive drinking may stem from the piglets' attempt to satiate hunger through gut fill from a familiar ingestive source. Gut fill through water intake may affect the establishment of feeding behavior. Using drinker devices other than the standard nipple drinker may ease the piglets' transition at weaning by facilitating the initiation of feeding and preventing the development of behavioral problems such as excessive drinking and belly nosing. In this experiment, we examined the effect of drinker type on water and food intake, growth rates, and belly nosing in newly weaned piglets. Eighteen pens of 15 piglets each (270 piglets total) were weaned at 18.1 +/- 0.1 d of age and housed in pens containing 1 of 3 drinker devices (standard nipple, push-lever bowl, and float bowl). Piglets' water and feed intake, water use, BW, and behavior were examined on a pen basis through 2 wk after weaning. Piglets with nipple drinkers wasted more water than the other piglets (P < 0.001; float, 295 +/- 70 mL x pig(-1) . d(-1); nipple, 1,114 +/- 63 mL x pig(-1) . d(-1); and push-lever, 186 +/- 63 mL x pig(-1) . d(-1)), whereas piglets with float bowls consumed less water than the other piglets (P < 0.001; float, 475 +/- 81 mL . pig(-1) x d(-1); nipple, 870 +/- 76 mL x pig(-1) . d(-1); push-lever, 774 +/- 76 mL x pig(-1) . d(-1)). Drinker type affected feeding behavior (P = 0.02); piglets with push-lever bowls spent less time at the feeder than the other piglets, although no difference was detected for feed intake (P = 0.64) or overall ADG (P = 0.16). Piglets with push-lever bowls also tended to perform less piglet-directed nosing behavior than piglets with the float bowl (P = 0.04). Piglets appear to use more water during the first 2 d after weaning with certain drinker devices. However, piglets do not appear to attain satiety through water consumption because most of the water used during the first few days after weaning is wasted. This excessive drinking and water wastage can be abated through the use of push-lever drinkers without negative implications for feed intake or growth rates.     

Effect of drinker type and sound stimuli on early-weaned pig performance and behavior

Early-weaned pigs appear to be highly motivated to engage in motor patterns associated with nursing, which is thought to lead to the development of abnormal ingestive behaviors. If performance of these behaviors is related to sucking motivation, then the normal stimuli associated with nursing should stimulate pigs to perform these abnormal behaviors, specifically belly nosing. The goal of this study was to determine whether belly nosing could be affected by sow nursing vocalizations and whether the style of the drinker device influenced early-weaned pig behavior. Over six trials, 352 Yorkshire pigs were weaned at 15 d and assigned to pens (n = 44) of eight pigs based on litter, weight, and sex. Four pens in each of two rooms were outfitted with either a water nipple drinker or a drinker bowl. Rooms either had recorded sow vocalizations broadcast at hourly intervals or no sound (control). Pig behaviors were videotaped in a sample of pens (n = 32) on d 0, 1, 2, 5, 9, 11, 13, 16, and 18 after weaning. On d 0 to 2, pigs were observed continuously for feeding and drinking behaviors. On d 5 to 18, pigs were observed by scan sampling every 5 min for time budgets. Pigs with drinker bowls had higher apparent feed intakes during the first 2 d after weaning (P = 0.024), whereas they spent less time engaged in drinking behavior (P = 0.001). This coincided with an overall lower water use (P = 0.001) than that of pigs with nipple drinkers. Pigs with bowl drinkers also spent less time belly nosing than those with access to a nipple drinker (P = 0.012). Pigs in the sow vocalization treatment tended to have a higher ADG (P = 0.075), whereas they spent less time performing feeding behavior (P = 0.064). However, there was no effect of sow nursing grunts on belly nosing. These results suggest that there is a complex relationship between feeding, drinking and sucking, and belly nosing is not controlled by the same external stimuli as sucking. Because drinker type and the motor patterns that it accommodates affect belly nosing, it may be that the internal stimuli associated with nursing, such as the actual act of sucking, play a large role in the development of abnormal oral-nasal behaviors.     

The use of feed-grade amino acids in lactating sow diets

Background: The use of feed grade amino acids can reduce the cost of lactation feed. With changing genetics,increasing feed costs, and higher number of pigs weaned with heavier wean weights further evaluation of higher inclusion levels of feed-grade amino acid in lactation diets than previously published is warranted. Two experiments(Exp.) were conducted to determine the optimal inclusion level of L-lysine HCl to be included in swine lactation diets while digestible lysine levels remain constant across dietary treatments and allowing feed grade amino acids to be added to the diet to maintain dietary ratios relative to lysine to maximize litter growth rate and sow reproductive performance. Furthermore, the studies were to evaluate minimal amino acid ratios relative to lysine that allows for optimal litter growth rate and sow reproductive performance.Results: Exp. 1: Increasing L-lysine HCl resulted in similar gilt feed intake, litter, and reproductive performance.Average litter gain from birth to weaning was 2.51, 2.49, 2.59, 2.43, and 2.65 kg/d when gilts were fed 0.00, 0.075,0.150, 0.225, and 0.30% L-lysine HCl, respectively. Exp. 2: The average litter gain from birth to weaning was 2.68,2.73, 2.67, 2.70, and 2.64 kg/d(P 0.70) when sows were fed 0.1, 0.2, 0.3, 0.4, and 0.4% L-lysine HCl plus valine,respectively. No other differences among dietary treatments were observed.Conclusions: Collectively, these studies demonstrate corn-soybean meal based lactation diets formulated with a constant SID lysine content for all parities containing up to 0.40% L-lysine HCl with only supplemental feed grade threonine and a methionine source have no detrimental effect on litter growth rate and subsequent total born.     

瑞典大白猪繁殖性能的研究

本文统计分析了2 063窝瑞典大白猪的繁殖性能,总产仔数、产活仔数、初生窝重、断奶头数、28日龄断奶窝重分别达到了12.03头、11.21头、17.09 kg、10.44头和83.21 kg,第4胎繁殖性能达到了最佳,最佳使用年限为6胎次。平均产仔间隔161.24 d,繁殖性能与产仔间隔呈反比关系。     

Novel insight into the control of litter size in pigs, using placental efficiency as a selection tool.

Chinese Meishan pigs produce three to five more pigs per litter than less-prolific U.S. or European pig breeds as a result of a markedly decreased placental size and an increased pig weight: placental weight ratio (placental efficiency). We hypothesized that as a result of their intense selection for prolificacy, the Chinese had indirectly selected for a smaller, more efficient placenta in the Meishan breed. The goals of this study were to determine whether 1) significant variation in placental size and efficiency existed within our population of purebred Yorkshire pigs and 2) selection of pigs (boars and gilts) based on clear differences in placental size and efficiency would affect litter size. There was significant (approximately threefold) variation in placental efficiency in our herd of Yorkshire pigs, and marked (approximately twofold) variation existed within individual litters. We then selected pigs (boars and gilts) that had either a higher (A Group) or lower (B Group) than average placental efficiency. Although the birth weights of selected A Group pigs were similar to those of the B Group pigs, they had markedly smaller placentae. Males from each group (A or B) were bred to the females of the same group, and farrowing data were collected from parities 1 and 2. In both parities, A Group females farrowed more live pigs per litter than did B Group females (12.5 +/- .7 vs 9.6 +/- .5, P < .05). Although A Group pigs were on average approximately 20% lighter than B group pigs (1.2 +/- .1 vs 1.5 +/- .1 kg, P < .05), their placentae were approximately 40% lighter (250 +/- 10 vs 347 +/- 15 g, P < .01), resulting in a marked increase in placental efficiency. The results of this study suggest that selection on placental size and efficiency may provide a valuable tool for optimizing litter size in commercially important pig breeds.     

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)