Relationships between body weight at first mating and subsequent body development,feed intake,and reproductive performance of rabbit does

A retrospective study was performed to evaluate the relationships between BW at first insemination and subsequent body development, feed intake, reproductive performance, and culling rate of rabbit does. Young rabbit does are vulnerable to body energy deficit in first lactation, resulting in decreased reproductive performance and high replacement rate. Heavy does at first insemination might be able to benefit from the extra amount of BW to cope with the energy deficit during first lactation. Data of three experiments were used in which does were given ad libitum access to feed during rearing and inseminated at 14.5 wk of age. The first two parities of each doe were recorded. Does were categorized in three groups based on their BW at 14.5 wk of age (first insemination): heavy (BW > or = 4,000 g), medium (BW 3,500 to 4,000 g), and small (BW < 3,500 g). Among does that kindled, differences in BW at first insemination were related to differences in voluntary feed intake and body growth rate during rearing. Heavy does consumed more feed per day (+ 45 g/d, P < 0.001) and had a higher BW gain (+ 12 g/d, P < 0.001) than small does from weaning (4.5 wk) to 14.5 wk of age. Body weight at first insemination did not affect BW, feed intake, and culling rate during the first two parities. Heavy does were heavier at first insemination and remained so throughout the reproductive period, but they followed a similar BW curve as medium and small does. A higher BW at first insemination (14.5 wk of age) improved litter size in the first parity (8.9, 7.7, and 6.4 for heavy, medium, and small does, respectively, P < 0.05). Extra BW at start of reproduction improves litter size in the first parity but does not contribute to an improved feed intake or increased BW development during reproduction.     

An increased feed intake during early pregnancy improves sow body weight recovery and increases litter size in young sows

This study evaluated the effect of feeding level and protein content in feed in first- and second-parity sows during the first month of gestation on sow BW recovery, farrowing rate, and litter size during the first month of gestation. From d 3 to 32 after the first insemination, sows were fed either 2.5 kg/d of a standard gestation diet (control, n = 49), 3.25 kg/d (+30%) of a standard gestation diet (plus feed, n = 47), or 2.5 kg/d of a gestation diet with 30% greater ileal digestible AA (plus protein, n = 49). Feed intake during the experimental period was 29% greater for sows in the plus feed group compared with those in the control and plus protein groups (93 vs. 72 kg, P < 0.05). Sows in the plus feed group gained 10 kg more BW during the experimental period compared with those in the control and plus protein groups (24.2 ± 1.2 vs. 15.5 ± 1.2 and 16.9 ± 1.2 kg, respectively, P < 0.001). Backfat gain and loin muscle depth gain were not affected by treatment (P = 0.56 and P = 0.37, respectively). Farrowing rate was smaller, although not significantly, for sows in the plus feed group compared with those in the control and plus protein groups (76.6% vs. 89.8 and 89.8%, respectively, P = 0.16). Litter size, however, was larger for sows in the plus feed group (15.2 ± 0.5 total born) compared with those in the control and plus protein groups (13.2 ± 0.4 and 13.6 ± 0.4 total born, respectively, P = 0.006). Piglet birth weight was not different among treatments (P = 0.65). For both first- and second-parity sows, the plus feed treatment showed similar effects on BW gain, farrowing rate, and litter size. In conclusion, an increased feed intake (+30%) during the first month of gestation improved sow BW recovery and increased litter size, but did not significantly affect farrowing rate in the subsequent parity. Feeding a 30% greater level of ileal digestible AA during the same period did not improve sow recovery or reproductive performance in the subsequent parity.     

Effects of altrenogest treatments before and after weaning on follicular development, farrowing rate, and litter size in sows

In a previous study, we showed that follicle size at weaning affects the response of a sow to a short-term altrenogest treatment after weaning. In this study, an attempt was made to prevent the growth of follicles into larger size categories before weaning by using different altrenogest treatments before weaning to improve reproductive performance after postweaning altrenogest treatments. Sows (87 primiparous and 130 multiparous) were assigned to the following treatments: control (no altrenogest treatment; n=59), RU0-20 (20 mg of altrenogest from d -1 to 6; weaning=d 0; n=53), RU40-20 (40 mg of altrenogest from d -3 to 0 and 20 mg of altrenogest from d 1 to 6; n=53), and RU20-20 (20 mg of altrenogest from d -3 to 6; n=52). Follicle size was assessed daily with transabdominal ultrasound. Follicle sizes on d -3 (3.6 ± 0.7 mm) and at weaning (4.0 ± 0.7 mm) were similar for all treatments. Altrenogest-treated sows had larger follicles at the beginning of the follicular phase than did control sows [5.4 ± 0.1 and 3.8 ± 0.2 mm (least squares means), respectively; P < 0.0001] and on d 4 of the follicular phase [8.0 ± 0.1 and 6.7 ± 0.2 mm (least squares means), respectively; P < 0.0001]. Multiparous sows had larger follicles than did primiparous sows at the beginning of the follicular phase [5.3 ± 0.1 and 4.7 ± 0.1 mm (least squares means), respectively; P < 0.01] and on d 4 of the follicular phase [8.0 ± 0.1 and 7.0 ± 0.1 mm (least squares means), respectively; P < 0.0001]. Farrowing rate and litter size (born alive + dead) were not affected by treatment or parity. However, in primiparous sows, when mummies were included in litter size, altrenogest-treated sows had larger litters than did control sows (13.4 ± 0.5 and 11.9 ± 0.7 piglets, respectively; P=0.02). In primiparous control sows, backfat depth at weaning and litter size were positively related (slope of the regression line=0.82; P < 0.05), which was not the case in primiparous sows receiving altrenogest. In conclusion, the different altrenogest treatments before weaning did not prevent the growth of follicles before weaning and similarly affected subsequent follicle development and fertility. In primiparous sows, altrenogest treatment after weaning increased the number of fetuses during pregnancy, but positive effects seemed limited by uterine capacity. Altrenogest treatment after weaning improved litter size in primiparous sows with reduced backfat depth at weaning, which suggests a specific positive effect of a recovery period after weaning in sows with reduced BCS at weaning.     

The effects of weaning age, diet composition, and categorisation of creep feed intake by piglets on diarrhoea and performance after weaning

This study investigated the effects of weaning age, diet, and classification of piglets as ‘eaters’ or ‘non eaters’ of creep feed in lactation, on production and diarrhoea after weaning. Four antimicrobial-free diets were offered in lactation and for 14 days after weaning: (i) wheat–soy based diet with animal and vegetable (‘mixed’) protein sources (COMM), (ii) heat-processed rice (HPR) with barley hulls and potato starch and mixed protein sources (RBHPS), (iii) HPR with sugar-beet pulp and mixed protein sources (RSBP), and (iv) HPR with mixed protein sources (R). Piglets were individually examined for diarrhoea daily for 14 days after weaning, and antibiotic treatments were individually recorded. Faecal swabs were taken on day 10 after weaning and scored for β-haemolytic Escherichia coli. There were significant main effects of weaning age and diet (both P < 0.001) on daily gain between weaning and 14 days after weaning. Pigs weaned later grew 50 g/day more than pigs weaned earlier, and pigs fed the COMM diet grew slower than pigs fed the rice-based diets. The number of antibiotic treatments was influenced by diet (P < 0.001), with most treatments (2.1) given to pigs fed the diet RBHPS. Faecal score was influenced by a weaning age and diet interaction (P < 0.01). There was no correlation (P > 0.05) between the number of antibiotics treatments and the E. coli score.     

The effect of meal intervals and weaning on feed intake of early weaned pigs

Feed intake was investigated in early weaned pigs housed in two environments. In the first experiment, pigs in an unfamiliar environment (removed from the sow and placed in nursery pens) were offered a dry diet either ad libitum or at different meal intervals (2, 4 and 6 h). Regardless of meal interval (ad libitum or hourly intervals), early weaned (21 d) pigs failed to consume sufficient feed for maintenance during the first 3 d postweaning. Pigs provided feed ad libitum consumed more (P less than .001) feed (142 vs 84 g/d) and gained more (P less than .05) weight (57 vs 3 g/d) than meal-fed pigs over the 7-d period. Pigs fed at 2-h intervals consumed more (P less than .001) feed than pigs fed at 4-h or 6-h intervals. Compared with preweaning levels (307 mu eq/liter), plasma free fatty acid (FFA) levels increased approximately fourfold by d 1 postweaning (1,372 mu eq/liter), then decreased through d 7 to levels below preweaning (142 mu eq/liter). The FFA levels were not affected (P greater than .1) by meal interval. In a second experiment, feed intake was investigated in weaned pigs that were allowed to consume food by a familiar method and in a familiar environment (suckling the sow). When allowed to nurse following a 24-h weaning period, weaned pigs consumed (24.3 +/- 2.8 g/suckling) the same amount (P greater than .1) as non-weaned littermates (28.7 +/- 1.8 g/suckling).(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of premating feed intake on the reproductive performance of gilts.

In an attempt to improve the reproductive performance of gilts mated at puberty, 70 Yorkshire x Landrace gilts were allocated at 120 d of age and 60 kg body weight to one of two treatments. Restricted gilts were fed 2.0 kg d-1 of a diet formulated to provide 18% crude protein and 14.5 MJ DE kg-1 from selection until mated at their first estrus (n = 35). Flushed gilts were fed 2.0 kg d-1 of the same diet from 120 to 150 d of age, but then had their feed intake increased to 3.5 kg d-1 until mated at their first estrus (n = 35). An additional group of gilts (control fed; n = 33) were fed 3.0 kg d-1 from selection until they were bred at their third estrus in order to investigate the influence of feed restriction on the onset of puberty. During gestation all gilts were fed 1.8 to 2.2 kg d-1 of a 16.8% crude protein diet having 13.7 MJ DE kg-1. Control fed gilts were younger (p less than 0.05) at puberty (150 d) than restricted (165 d) or flushed gilts (165 d). There was no difference in subsequent litter size between the restricted and flushed gilts (7.7 and 8.0, respectively). It is concluded that the institution of a flushing nutritional regime in the prepubertal period will not enhance piglet production from gilts mated at puberty.     

Energy intake, body composition and reproductive performance of the gilt

The relationship between age, live weight, body composition and energy status on the onset and maintenance of reproductive activity in females is reviewed. When possible, swine studies have been employed, although, of necessity, much data are drawn from other species. The relationship between age, weight and puberty is controversial. However, from the available data we conclude that neither age nor weight are reliable indices of reproductive development, but that minimum threshold values for these characteristics must be achieved before puberty can occur. Human data provides a strong indication that a minimum adipose to lean tissue ratio is a prerequisite for puberty onset. Limited data from swine support this contention and indeed it may be a superior measure of reproductive development than either age or weight. However, the value of this ratio remains to be defined in pigs, and again it is minimum threshold level, the attainment of which is necessary, but not in itself sufficient, for puberty onset. A positive energy balance seems to be necessary for puberty onset and the maintenance of estrous cycles in some species, but this has not been investigated in swine. The mechanisms whereby adiposity and energy status influences reproduction are discussed. Human studies demonstrate a negative correlation between energy status, body fatness and plasma gonadotrophin levels. Also, adipose tissue has the ability to metabolize sex steroids, aromatizing androgens to estrogens and changing the direction of estrogen metabolism to produce more or less biologically potent estrogens.     

Effects of catechins on litter size,reproductive performance and antioxidative status in gestating sows

This study was conducted to investigate the effects of catechins on reproductive performance, antioxidative capacity and immune function of gestating sows. A total of 60 cross-bred(Landrace × Large White) multiparious sows were blocked by body weight, parity and backfact and randomly allocated to 1 of 5 treatments: 0.100,200,300, or 400 mg/kg catechins. Dietary treatments were imposed from mating to d 40 of gestation of sows. At farrowing, litter total born, born alive, dead, and normal-(healthy piglets,0.85 kg) and low-birth weight piglets(0.85 kg) were recorded. Within 3.00 ± 0.50 days after farrowing litter size was standardized to 8,00 ± 1.50 piglets within treatment. The piglets were weighed at birth(d 1) and weaning(d 28). Sows serum samples were obtained from blood samples collected on d 40 of gestation for analyses of glutathione peroxidase(GSH-Px), superoxide dismutase(SOD), catalase(CAT),malondialdehyde(MDA), hydrogen peroxide(H_2 O_2), nitric oxide synthetase(NOS) and nitrogen monoxide(NO). Our results showed that supplementation of catechins at levels of 200 or 300 mg/kg led to improvements in litter born alive(P 0.01) and piglet born healthy(P 0.01) and a decrease in stillborn(P 0.05) at farrowing when compared with the control. In comparison with the control, catechins at any supplemental levels all enhanced the serum SOD(P 0.05) and CAT(P 0.01) activities of sows at farrowing but no obvious differences in the serum GSH-Px and NOS activities were observed in this trial(P 0.05). Sows received 200 mg catechin per kg diets showed a reduction(P 0.05) of the serum MDA level at farrowing compared with all other treatments. Sows received all the levels of catechin showed a reduction(P 0.05) of serum H_2 O_2 level compared with sows received the control diet on both d 40 of gestation and farrowing. Our results demonstrated that the catechins may be a potential antioxidant to increase the reproductive performance and antioxidative capacity of sows when it was added into diets during the early gestation.     

Connection between body condition score, chemical characteristics of body and reproductive traits of rabbit does

Body condition scoring (BCS) is widely used to evaluate the nutritional status of livestock (cows, ewes, sows). In intensive systems, rabbit does are generally inseminated 11 days post partum and, due to a hormonal antagonism and an energy deficit caused by concurrent lactation and pregnancy, they show low fertility. The aim of this investigation was to assess an in vivo method for scoring the body condition of does by verifying the association with the body fat depots, the chemical composition of body tissues, the ovarian status, the hormonal response and the reproductive performance. The evaluation of BCS, involving 66 multiparous lactating does inseminated at 11 days post partum, was based on the test of bone protrusions and fullness of muscle of the loin, rump and hind leg. The traits were subjectively scored using 0, 1 and 2 for poor, intermediate and good condition, respectively. For calculating an aggregate BCS, the hind leg score was omitted, because it is less correlated with the real body condition. Adding the respective score (0–2) of the loin and rump regions, 5 classes of BCS were obtained (0–4). This aggregate BCS was highly correlated with the body fat depots (r = 0.79), the ether extract content of muscle samples of Obliquus abdominis (r = 0.87) and Biceps femoris (r = 0.84), and the ether extract of the empty body (r = 0.84). There was a lower correlation with the body weight (r = 0.45). The increase of BCS corresponded to higher lipid content in the body parts considered, especially the Obliquus abdominis (from 2.0 to 10.0%) and fat depots (from 10.6 to 107.7 g/doe). BCS was not related to ovulation rate or embryo production, but was correlated with sexual receptivity and fertility.Plasma FSH and LH concentrations were determined by RIA, 48, 24, 0 h before and 1 h after GnRH administration and artificial insemination. Animals with extreme body condition scores (BCS ≤ 1 or BCS = 4) showed lower plasma FSH levels (20.0 vs. 34.5 ng/mL) than does with optimal body condition (2 ≤ BCS ≤ 3) and their preovulatory LH surge, released after GnRH administration, was less evident (16.9 vs. 20.3 ng/mL). The poor reproductive performance of does with extreme BCS could be explained by this pituitary activity. On day 11 post-partum, a high number of does (71.2%) had extreme BCS and showed a lower sexual receptivity (37.2% vs. 80.0%) and fertility rate (50.9% vs. 86.6%) than does in optimal condition. On these results, the possibility of applying an in vivo method for scoring the body condition of lactating rabbit does appears promising for use in on-farm reproductive management.     

Effect of sex ratio of the birth litter on subsequent reproductive performance of gilts

Records on age at puberty from 1,555 gilts and total number of pigs born in litters of 1,187 gilts from the Nebraska gene pool population were used to evaluate the effects of uterine environment on subsequent reproductive performance. Independent variables were line, year, line x year, proportion of males in the birth litter (sex ratio), number born in the birth litter (fraternity size) and sex ratio x fraternity size. Sex ratio, fraternity size and their interaction influenced age at puberty (P less than .01) but not number born (P greater than .2). Partial regression coefficients indicated that age at puberty tended to decrease as sex ratio increased, particularly in small litters. Although the regression coefficients were relatively large, sex ratio, fraternity size and their interaction accounted for only 1.3% of the variation in age at puberty within line x year subclass. These results offer little encouragement for the use of sex ratio as a phenotypic selection criterion for improvement of reproductive performance in gilts. Results suggest that female swine are similar to rodents in response to uterine environmental effects.     

结构性饲料对哺乳期和断奶应激期犊牛采食量和生长性能的影响

试验旨在研究群饲犊牛自由采食酸化奶的条件下,结构性饲料对哺乳犊牛和断奶应激期犊牛生长性能的影响。选择3～5日龄、体重相近犊牛300头,随机分为6栏,每栏50头,随机选择3栏饲喂常规颗粒犊牛开食料(颗粒料组),其余3栏饲喂结构性犊牛开食料(结构料组)。两种日粮的配方完全一致。颗粒犊牛料中所有物料均经粉碎、混合、制粒,制成颗粒料。将饲粮配方中玉米和大麦取出,换为蒸汽压片玉米和带壳大麦,其余物料粉碎、混合、制粒,为颗粒浓缩料,再将颗粒浓缩料与蒸汽压片玉米、带壳大麦混合,制成结构性饲料。整个试验分为哺乳期和断奶应激期共计90 d,哺乳期试验第1 d饲喂酸化奶,第15 d供应开食料。颗粒料组犊牛在哺乳期饲喂开食料,断奶后补饲苜蓿干草。结构料组犊牛断奶后饲喂结构性生长料。将结构性开食料与20%苜蓿干草混合,制成结构性生长料。结果表明:哺乳期间,结构性饲料采食量比颗粒料组高40%(P<0.05),日增重高19%(P<0.01);断奶应激期间,结构性饲料采食量比颗粒料组高29%(P<0.01),日增重高25%(P<0.01),饲料利用效率高11%(P<0.05);试验结束时,结构料组犊牛体重更高(P<0.05)。综上所述,在哺乳期自由饮用酸化奶的条件下,结构性饲料在哺乳期和断奶应激期的效果均优于传统颗粒开食料,可促进犊牛生长,缓解断奶应激。     

Renewed selection for heat loss in mice: direct responses and correlated responses in feed intake, body weight, litter size, and conception rate

Divergent selection in mice was renewed in 3 independent replicates for high (MH) and low (ML) heat loss. An unselected control (MC) was maintained in all replicates. Heat loss was measured for individual male mice for 15 h, overnight in direct calorimeters. After 16 initial generations of selection followed by 26 generations of relaxed selection, divergent selection resumed for 9 generations. The realized selection applied was very close to the maximum possible selection according to the criteria and protocol. Selection differentials were greater for high than for low selection due to greater variation in the MH line. When corrected for SD, standardized selection differentials were similar for MH and ML selection. Unintended selection in MC was negligible. Realized heritability for divergence was 0.14 +/- 0.01, which was considerably less than that realized during the initial generations of selection (0.28 +/- 0.03). Realized heritabilities for MH selection (0.16 +/- 0.05) and for ML selection (0.07 +/- 0.06) were less, especially for ML selection, than were observed in the earlier generations. The difference in heat loss between MH and ML males was 55.7% of the MC mean at generation 51, compared with a difference of 53.6% in generation 15; this difference had decreased to 34.4% at the end of the relaxed selection (generation 42). For feed intake between 8 and 11 wk, MH and ML males differed by 34.0% of the MC mean by the end of the selection process. Body weight at 12 wk for MH and ML males was less than for MC males. Litter size response was positively related to the heat loss response. Conception rate was poorer in MH matings than in MC and ML matings.     

The effects of vomitoxin and feed intake on the performance and blood characteristics of young pigs

Thirty barrows (average weight 8.4 kg) were used in a 3-wk experiment to determine the effects of the ingestion of vomitoxin (deoxynivalenol)-contaminated feed on performance and blood chemistry. The barrows were assigned randomly to consume either: 1) a control diet (C), fed ad libitum, 2) a vomitoxin contaminated diet (V; 10.5 ppm), fed ad libitum, or 3) a vomitoxin contaminated pair-fed at levels equal to those consumed by V animals (PF). The V and PF pigs had similar daily gains (.19 vs .20 kg) and feed intakes (.40 and .39 kg), but both of these were lower (P less than .01) than those for the C-fed pigs (.38 kg daily gain and .72 kg feed intake). The V-fed pigs had lower (P less than .05) hematocrit, hemoglobin, serum glucose and serum phosphorus and tended to have lower serum calcium (P less than .06) than C-fed pigs. The V-fed pigs had higher (P less than .05) hemoglobin and tended to have higher (P less than .08) serum phosphorus and lower (P less than .07) serum calcium than PF animals. There was a high total- and free-bilirubin concentration in serum of C- and V-fed pigs in the last sampling period (3-wk), which may be due to fasting and not cholestasis. No differences among treatments were observed in any of the other blood parameters. These results suggest that the differences in animal performance and blood parameters observed between control-and vomitoxin-fed pigs are mainly due to differences in feed intake.     

Influences of parity and level of feed intake on reproductive response to insulin administration after weaning in sows

In three experiments, the influence of insulin administered after weaning was examined in primiparous sows given extra feed or in primiparous compared to multiparous sows. In Exp. 1, 171 primiparous and 231 multiparous crossbred sows on a commercial farm were injected with 0.4 IU/kg BW insulin (Eli Lilly Lente Iletin II) or saline for 4 d beginning the day after weaning (d 0) and were fed 2.3 kg/d until mating. In Exp. 2, 153 primiparous sows from the same farm as those in Exp. 1 were injected with insulin or saline as in Exp. 1 and were fed 2.7 or 3.6 kg/d until mating. In Exp. 3, 63 primiparous crossbred sows were injected with insulin or saline as described above and fed either 2.3 or 4.5 kg/d for 5 d after weaning and were remated. On the commercial farm (Exp. 1 and 2), insulin administration increased percentage in estrus for primiparous sows compared to multiparous sows (treatment x parity interaction, P < 0.02) but tended to lower litter size in primiparous sows (treatment x parity interaction, P < 0.06). In Exp. 2, insulin combined with extra feed increased (P < 0.05) litter size by two pigs but tended (P < 0.07) to decrease farrowing rate in that group (treatment x feed interaction). Weaning-to-estrus interval, pregnancy rate, ovulation rate, and embryo survival were not influenced by treatment or feeding level (Exp. 3); however, postweaning intake and embryo survival were negatively related for saline-treated sows only (r = -0.55; P < 0.01), and backfat depth at weaning and embryo survival were positively related for insulin-treated sows only (r = 0.44; P < 0.05). Overall, insulin administration differentially influenced reproduction in primiparous sows and may have interacted with metabolic or nutritional state of the animal.     

The effect of varying flock size on the development and subsequent laying performance of floor‐reared pullets

Light‐weight, hybrid pullets were reared on litter in flocks of 400, 800 and 1200 birds per pen. Floor space allowance was held constant at 0–093 m² per bird and other related factors of management were standardised. The different sizes of flock had no significant effect on growth rate or mortality, but individual food consumption was significantly higher in the 400‐bird flocks than in the larger units.

At 18 weeks of age, some of the birds from each treatment were transferred to battery cages and others to deep‐litter laying quarters and records of their performance in terms of egg numbers and size, food consumption, mortality and body weight gain were taken over a period of 1 year. The only consistently significant finding was that birds reared in groups of 1200 tended to produce larger eggs (as shown by market grading) and, when housed on deep litter, to eat more food than birds reared in the smaller flocks.     

Comparison of rabbit breed types for postweaning litter growth, feed efficiency, and survival performance traits

Postweaning data on 643 rabbits from 122 litters representing four breed types, New Zealand White (NZW) and Californian (CAL) purebreds, CAL X NZW (CXN), and Flemish Giant (FG) crossbreds (the latter group was a collection of FG X CAL, FG X Champagne D'Argent [CHA], and 1/2 FG X 1/4 CAL X 1/4 CHA), were gathered over five seasons and compared for growth, feed efficiency, and survival-related performance traits. Evaluation criteria included litter size and weight at weaning (28 d); 28- to 70-d litter feed intake, weight gain, feed efficiency, and mortality rate; and litter and average market weight (70 d). The least squares model included main effects of breed type, season of birth of the litter and parity of dam, litter size at weaning as a linear covariate, and the random error. Breed-type differences were not detected for litter size and weight at weaning and feed efficiency. Purebred NZW and CAL litter trait performances were comparable (P greater than .05). Purebred NZW litters consumed less feed than CXN and FG crosses, gained weight less rapidly than FG crosses, and weighed less per fryer at 70 d than CXN and FG crosses (P less than .05). Feed intake was lower and average market weight was lighter for CAL purebred litters than for CXN and FG crossbred litters (P less than .05). The CXN and FG crossbreds only differed (P less than .05) for average market weight (2,078 vs 2,192 g). Mortality rate was lower (P less than .05) in CXN crossbred litters than in CAL purebred litters.(ABSTRACT TRUNCATED AT 250 WORDS)