乏情母牛的诱发发情技术研究

饲喂PEP（含矿物质和维生素的添加剂）结合激素处理154头产后乏情母牛，以期诱导发情。结果表明：饲喂PEP 30d组结合激素处理比未处理对照组极显著（P＜0．01）提高发情率（100％比65．6％）和繁殖率（84％比46．9％），比单独的激素处理组极显著地（P＜0．01），提高发情率（100％比75％）；单独饲喂PEP（P）组比对照组可显著（P＜0．05）提高发情率（87．3％比65．5％）和繁殖率（76．4％和46．9％），激素处理结合饲喂PEP（P－H）组可极显著（P＜0．01）高于对照组的发情率（93．6％比65．5％）和繁殖率（78．7％比46．9％），但P组和P－H组间的发情率，受胎率和繁殖率均差异不显著（P＞0．05）。     

“1,2，1”哺乳法对仔兔生长发育的影响

选经产母兔同期产仔90窝，每窝选留仔兔6只，随机分为3组，进行3个时期不同哺乳次数试验。结果表明：睡眠期，每天哺乳1次与2次的窝重、窝增重和死亡率均差异不显著（P〉0．05）；开眼期，每天哺乳2次。Ⅰ、Ⅲ组窝重和窝增重显著高于哺乳1次的Ⅱ组（P〈O．05），各组死亡率差异不显著；追乳期、每天哺乳2次与1次，窝增重和仔兔死亡率均差异不显著（P〉0．05），但每天哺乳2次的断奶窝重，Ⅰ、Ⅲ组显著高于每天哺乳1次的Ⅱ组（P〈O．05），Ⅰ、Ⅲ组间差异不显著（P〉0．05）。Ⅰ组成活率虽高于Ⅱ、Ⅲ组，但差异均不显著（P〉0．05）。由此可见，仔兔阶段3个时期的哺乳次数以“1，2，1”较适宜。     

仔猪21日龄断奶试验初报

文章对21日龄仔断奶及相关技术进行研究，设28日龄仔猪断奶作对照试验。结果表明：仔猪63日龄平均体重，试验组19．43千克，显著高于对照组的17．69千克（P＜0．01）；保育期日增重，试验组322．1克，显著高于对照组的299．8克（P＜0．05）。保育期饲料转化率，试验组1．53，显著优于对照组的1．65（P＜0．01）；试验期间腹泻率，试验组2．4％，对照组5．33％，两者差异极显著（P＜0．01），断奶后母猪发情间隔，试验组5．48天，对照组5．12天，二者差异不显著（P．05）；受胎率基本一致。     

提高幼兔成活率的综合措施

1影响幼兔成活率的因素 1．1断奶时体况差 断奶前的饲养管理很重要，此时期仔兔的体质直接决定断奶后幼兔的抗病能力。实践中有些兔场不顾仔兔和母兔体质的好坏，一味地追求繁殖率，急功近利，其结果导致母仔体质不好，断奶后死亡率可达90％。再者是配套措施，若这些措施跟不上，很容易使仔兔感染疾病死亡。     

近交对獭兔生产性能影响的研究

近交系数分别为0．50、0．25、0．125、0的成年獭兔间交配对繁殖性能及所产后代的生活能力有很大影响，产活仔数分别为5．63只、6．13只、6．33只、7．00只；初生重分别为39．38g、47．70g、53．75g、53.80g，5月龄育成数分别为3．50只；4．38只、4．88只、5．88只，5月龄育成率分别为62．17％、71．45％、73．60％、84．00％，差异显著（P＜0．05）；30日龄断奶重分别为412．13g、455．63g、510．75g、512．13g，5月龄体重分别为2412．00g、2243．45g、2624．75g、2637．50g，0．50组和0．25组与0．125组和0组间差异显著（P＜0．05），0．125组与0组间差异不显著（P＞0．05）；随着近交系数的降低，母兔的繁殖性能、仔兔的生活力和生长速度明显提高。     

泌乳母猪饲粮适宜赖氨酸水平的初步研究

将30头大长北经产母猪随机分为3组，产后饲喂0．60％（I组），0．80％（II组），1．00％（III组）3种赖氨酸水平的泌乳期饲粮，研究饲粮赖氨酸水平对泌乳母猪生产性能及血液，奶生化指标的影响，结果表明，增加饲粮赖氨酸浓度对哺乳21天的母猪体重，采食量，断奶至再发情天数（P＞0．10）和21日龄的平均窝仔数，仔猪腹泻率无显著影响（P＜0．05），21日龄仔猪窝重随着饲粮赖氨酸浓度的增加而显著增加（P＜0．06），初生至7日龄（P＜0．06），14日龄（P＜0．03）和21日龄（P＜0．01），的窝增重均随饲粮赖氨酸浓度增加而增加，产后14天猪乳蛋白II组，III组极显著（P＜0．01）高于I组；固形物含量II组显著（P＜0．05）高于I组，产后21天猪乳固形物含量II组显著（P＜0．05）高于I组，泌乳期母猪血清尿素氮[浓度I组显著（P＜0．05，泌乳14天），极显著（P＜0．01，泌乳21天）高于II组，III组；白蛋白浓度II组显著（P＜0．05），高于I组，从本次试验的结果看出，在生产条件下，大长北母猪泌乳期饲粮赖，氨酸水平以0．80－1．00％为宜。     

果寡糖对肉鸡生长、肠道菌群和肠形态的影响

研究了饲粮中分别添加0、2000、4000、6000mg/kg果寡糖对艾维菌商品代肉鸡生长性能、肠道菌群和肠形态的影响。结果表明：目粮中添加4000mg/kg果寡糖使肉鸡日增重提高了9．53％（P＜0．01），2000、4000mg/kg果寡糖使料重比分别降低了5．09％（P＜0．05）和7．87％（P＜0．05）；4000mg/kg果寡糖使盲肠中双歧杆菌和总厌氧菌数分别增加了257．65％（P＜0．05）和100．00％（P＜0．05），使梭菌数下降了79．36％（P＜0．05）；2000、4000mg/kg果寡糖使盲肠中乳酸杆菌数分别增加了45．73％（P＜0．05）和67．97％（P＜0．01），使大肠杆菌数分别下降了75．71％（P＜0．05）和71．35％（P＜0．05）；4000和6000mg/kg果寡糖使盲肠中乙酸、丁酸和总短链脂肪酸含量分别提高了23．25％（P＜0．05）和26．08％（P＜0．05）、144．36％（P＜0．05）和202．97％（P＜0．01）、47．08％（P＜0．01）和58．31％（P＜0．01）；2000、4000和6000mg/kg果寡糖使盲肠中丙酸含量分别提高了45．27％（P＜0．05）、73．22％（P＜0．01）和89．37（P＜0．01）；4000、6000mg/kg果寡糖使盲肠上皮黏膜腺窝深度和细胞密度分别提高了22．62％（P＜0．05）和25．72％（P＜0．01）、19．28％（P＜0．05）和23．07％（P＜0．05）。     

瘦肉型猪杂交组合的筛选研究

本试验研究了早籼稻饲粮中添加NSP酶对生长猪作用效果的影响。结果表明，与对照组比较，早灿稻饲粮中添加NSP酶制剂使生长猪日增重提高了11．18％（P＜0．05），料重比降低了9．42％（P＜0．05）；粗蛋白、粗脂肪和粗纤维的表观消化率分别提高了18．76％（P＜0．01）、16．04％（P＜0．05）、108．57％（P＜0．05）；腹泻率、粪便大肠杆菌数分别下降了37．00％（P＜0．05）、81．29％（P＜0．05）。     

饲粮中添加高剂量无机锌对断奶仔猪消化性能的影响

本试验研究了饲粮中添加高剂量无机锌对断奶仔猜消化性能的影响。结果表明：饲粮中添加3000mg／kg氧化锌使饲料粗蛋白、粗脂肪的表观消化率分别提高了11.35％（P〈0．01）和36.94％（P＜001）；胃、胰脏、小肠的相对重量分别增加了20.00％（P＜0．05）、20．57%（P〈0．05）和38．80%（P〈0．01）；十二指肠内容物总蛋白水解酶、胰蛋白酶、α-淀粉酶和脂肪酶活性分别较对照组提高了6.97％（P〈0．05）、25.37％（P〈0．05）、41.86％（P〈0．05）和110．91％（P〈0．01）．此外．3000mg／kg氧化锌和硫酸锌健粪中大肠杆菌数量减少了50.38％（P〈0．01）、48.50%（P＜0．01），腹泻频率则分别降低了96.88％（P〈0.01）和68.75％（P〈0．01）。     

木瓜粉对新西兰白兔繁殖性能及泌乳性能的影响

选取前2胎产仔数相近、体况一致的新西兰白兔妊娠母兔48只,随机分成3组,探讨木瓜粉对母兔繁殖性能、泌乳量及血清激素等指标的影响。对照组饲喂基础日粮,试验Ⅰ、Ⅱ组分别在基础日粮中添加5％、10％木瓜粉。妊娠18天时试验开始至仔兔30日龄断奶时结束,为期42天。结果显示：与对照组相比．试验组仔兔初生窝重、21天窝重、断奶窝重显著提高（P〈0．05）,产仔数、活仔数、断奶数等差异不显著（P〉0．05）．两试验组间差异不显著（P〉0．05）;木瓜粉显著提高母兔7、14、21天的泌乳量（P〈0．05）,提高21天血清E2、PRL水平（P〈0．05）。结果表明添加木瓜粉可提高母兔的繁殖性能和泌乳性能。     

Effect of dietary crude protein level on the reproductive performance and growth of New Zealand white rabbits

An experiment utilizing 391 preweaning and 187 postweaning litter records from 145 does was conducted for 12 mo to determine the effect of dietary crude protein level on performance of commercial New Zealand White rabbits. Does and their litters were fed alfalfa-based pelleted diets containing either 17.5, 19 or 20.5% crude protein (CP). In a separate experiment, the 17.5 and 20.5% CP diets were fed during lactation to 10 does to determine nitrogen (N) digestibility and retention. Body weights of does fed 17.5% CP were lower (P less than .01) than for the other treatments after 21 and 28 d of lactation. No differences (P greater than .10) were observed for doe weight at kindling, percentage fertility, litter size, preweaning litter mortality, 1- to 21-d consumption, preweaning feed efficiency and 28- to 56-d average daily consumption, average daily gain and average weight. Total born tended to be higher (P = .07) on higher protein levels but percentage born alive was greatest (P less than .01) on the 17.5% CP diet. Does fed 19% CP tended to have a greater number of parities (P = .06). Other significant differences observed for preweaning litter traits were between 17.5 and 19% CP groups. Does fed 19% CP had heavier litters at birth (P less than .01), at 21 d (P = .05) and 28 d (P = .06) and had greater 1- to 21-d litter gains and 21- to 28-d consumption (P = .05) than those fed 17.5% CP. For postweaning performance, feed efficiency values were lowest and mortality was highest for litters fed 20.5% CP. When litters were switched to different diets after weaning, mortality tended to be higher (P = .07) for animals that were fed 20.5% CP before weaning. The month of experiment effect did not influence any of the characters studied (P greater than .05). Parity number was important for percentage fertility, percentage born alive, litter birth weight and doe weight at 21 and 28 d (P less than .05). Does at first parity showed the poorest performance for all traits (except percentage fertility). Fertility fluctuated throughout the first four parities and then steadily declined. Does fed 20.5% CP had greater apparent dry matter and acid detergent fiber digestibilities and N intakes (P less than .05) and retained 90% more N during lactation (P = .22) than does fed 17.5% CP. Milk production and CP digestibility did not differ between the two diets tested.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparison of Finnish landrace crossbred ewes with Columbia, Rambouillet and Targhee ewes on western range

The objective of this study was to compare reproductive efficiency and wool production of 1/4 Finn crossbred ewes with straightbred Columbia, Rambouillet and Targhee ewes. In Phase I, white-faces ewes (WF; Columbia, Rambouillet and Targhee) were bred to either rams of their own breed or Finnish Landrace X Rambouillet rams (F X R) to produce 821 lambs from 563 lambings. Ewes bred to F X R had similar average litter size and individual lamb weights at birth, 60 d and weaning as those bred to WF. Lambs sired by F X R had 7% higher (P less than .01) lamb weaned per ewe lambing for ewes bred to F X R rams. For Phase II, approximately equal numbers of F X R-sired (1/4Fx) and WF-sired female lambs produced in Phase I each year were exposed to Suffolk rams at yearly intervals beginning at 7 mo of age. At 1 yr of age, 1/4Fx had higher fertility (P less than .01) than WF (37.7% vs 1.3%), resulting in 14.0 kg more lamb weaned per ewe exposed to breeding. Mature (ages 2 to 6 yr) 1/4Fx ewes had similar fertility to mature WF ewes, but litter size, number of lambs at 60 d and weaning was .36, .24 and .22 lambs higher (P less than .01), respectively, for mature 1/4Fx. Progeny of 1/4Fx were lighter at birth (P less than .01), but not different (P greater than .05) at 60 d and weaning than those of WF. Survival to 60 d unadjusted and adjusted for birth weight was 4.6% (P less than .05) and 7.6% (P less than .01) higher, respectively, for 1/4Fx progeny than for WF progeny.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of L-carnitine fed during gestation and lactation on sow and litter performance

Multiparous sows (n = 307) were used to evaluate the effects of added dietary L-carnitine, 100 mg/d during gestation and 50 ppm during lactation, on sow and litter performance. Treatments were arranged as a 2 (gestation or lactation) x2 (with or without L-carnitine) factorial. Control sows were fed 1.81 kg/d of a gestation diet containing .65% total lysine. Treated sows were fed 1.59 kg/d of the control diet with a .23 kg/d topdressing of the control diet that provided 100 mg/d of added L-carnitine. Lactation diets were formulated to contain 1.0% total lysine with or without 50 ppm of added L-carnitine. Sows fed 100 mg/d of added L-carnitine had increased IGF-I concentration on d 60 (71.3 vs. 38.0 ng/mL, P<.01) and 90 of gestation (33.0 vs. 25.0 ng/mL, P = .04). Sows fed added L-carnitine had increased BW gain (55.3 vs 46.3 kg; P<.01) and last rib fat depth gain (2.6 vs. 1.6 mm; P = .04) during gestation. Feeding 100 mg/d of added L-carnitine in gestation increased both total litter (15.5 vs. 14.6 kg; P = .04) and pig (1.53 vs 1.49 kg; P<.01) birth weight. No differences were observed in pig birth weight variation. Added L-carnitine fed during gestation increased litter weaning weight (45.0 vs. 41.3 kg, P = .02); however, no effect of feeding L-carnitine during lactation was observed. No differences were observed in subsequent days to estrus or farrowing rate. Compared to the control diet, feeding added L-carnitine in either gestation, lactation, or both, increased (P<.05) the subsequent number of pigs born alive, but not total born. In conclusion, feeding L-carnitine throughout gestation increased sow body weight and last rib fat depth gain and increased litter weights at birth and weaning.     

Production traits of litters in 2 crossbred Duroc pig lines

Genetics of different pig lines affects litter size, birth weight, and neonatal losses. Low birth weight has long been associated with neonatal losses, but piglet body mass index is reported to show stronger correlation with stillbirth. The aim of this study was to investigate differences in litter size, number of stillborn piglets, piglet BW gain, and body mass index between 2 different Duroc crossbred lines. Landrace × Yorkshire sows in 2 farms (n = 89) were divided into 2 groups on each farm. One group of sows on each farm was inseminated with semen from Landrace × Duroc boars (boar group LD, n = 48), and the other was inseminated with semen from purebred Duroc boars (boar group DD, n = 41). Piglets were monitored from birth to weaning at the age of 5 wk. Litter size in boar group LD was larger than in boar group DD (P = 0.03). Number of stillborn piglets in boar group LD tended to be greater than in boar group DD (P = 0.07). Piglets in boar group DD had a greater BW at birth (P = 0.02) and at 3 wk (P = 0.01) than those in boar group LD. Body mass index from birth to weaning was greater in piglets in boar group DD vs. LD (P < 0.01), and both BW and body mass index of liveborn piglets at birth for both groups combined showed a positive correlation with survival at weaning (P < 0.01). In conclusion, breeding for larger litter size in boar group DD may be one approach to increase the number of vigorous piglets in production, but the inverse relationship between litter size and birth weight was more pronounced for this group than for boar group LD (P = 0.03). Further studies of the impact of litter size on BW gain are necessary before a final conclusion can be reached.     

Reproductive responses of rabbit does to a supplemental lighting program

The objective was to investigate whether the productivity of rabbit does can be improved, when natural photoperiod is decreasing, by adopting a supplemental lighting program. Three experiments were conducted involving two groups: control, submitted to the natural decreasing photoperiod, and supplemented with a lighting program which provided 14 h light/24 h beginning at 10 weeks of age. In the first experiment, 20 nulliparous does, 10 from each group, were euthanized 8 h after being presented to a buck; the overall number of follicles, whose diameter exceeded 1 mm, was determined macroscopically. The right ovaries were collected, histologically analyzed, and electronically measured. In the second experiment, 30 nulliparous does, 15 from each group, were presented to a buck (day 1). Receptive does were euthanized on day 8 to evaluate embryonic survival (number of normal embryos/ovulation rate). In the third experiment, 48 nulliparous does, 24 from each group, were followed from the first presentation to the buck until the weaning of the first litter. The effect of treatment on reproductive and body weight traits of does, and litter performance traits, at birth and weaning, was evaluated. The average number of follicles whose diameter exceeded 1 mm was higher in the treatment group (12.05±1.07 vs. 8.63±1.00, P=0.037). Receptive does of the treatment group had heavier ovaries relative to those of the control group (790±59 vs. 470±64 mg, P=0.004), whereas no treatment difference regarding this trait was found for non-receptive ones. Treatment had a favorable effect on pregnancy rate of total exposed and of receptive does (80.0% vs. 33.3%, P=0.01, and 92.3% vs. 50.0%, P=0.02, respectively). The number of underdeveloped embryos was lower (0.067±0.380 vs. 2.500±0.455, P=0.004), embryonic survival up to day 8, and uterus weight was higher in the treatment group (0.839±0.075 vs. 0.534±0.087, P=0.033 and 13.83±0.72 vs. 10.99±0.84, P=0.037, respectively). Number of presentations tended to be lower (1.32±0.17 vs. 1.75±0.16, P=0.077) and adjusted litter size in the first reproductive cycle tended to be higher (7.09±0.89 vs. 5.22±0.68, P=0.091) in the treatment group relative to the control group. A supplemental lighting program providing 14 h light/24 h favors reproductive performance of primiparous does; its application may be recommended to increase productivity when natural photoperiod is decreasing.     

Lifetime parental productivity in twenty-seven crosses of mice. II. Weaning traits reflecting reproduction and lactation

Twenty-seven crosses of mice derived from three random-mating, unselected strains (SWO, J. PGH) with 16 matings/pureline or cross were cohabited continuously and monogamously for a 365-d reproduction period to evaluate lifetime reproductive performance of the parents. Data from 3,249 litters born (2,792 surviving to weaning) were analyzed to study the effects of parity (number of litters) and type of cross (pureline, two-way, backcross, three-way) on certain traits measured at weaning (21 d). The traits evaluated were 1) weaning to weaning interval (WWI), 2) litter size at weaning (LSW), 3) fraction alive at weaning (FAW)-the ratio of LSW to number born alive, 4) total litter weight at weaning (LWT), 5) pup weight at weaning (PWT), 6) weaning weight per pup observed alive at birth (WPP), 7) parental feed consumption per day (FPD) and 8) parental costs (PCT). Cost per live weanling animal was estimated as the ratio of cumulative parental costs to cumulative number weaned. Cost per unit of weaning weight was defined as the regression of cumulative parental costs on cumulative litter weight. Parity effects were important (P less than .01) for all traits measured. Type of cross effects were noted for LSW, LWT, PWT, WPP, FPD (P less than .01) and PCT (P less than .05). A parity X cross-type interaction was expressed for WWI, LSW, PWT, WPP, FPD (P less than .01) and FAW (P less than .05). Three-way crosses were more productive than backcrosses, two-way crosses and pureline matings for all traits studied. Three-way crosses displayed the smallest cost per animal weaned and smallest cost per unit of weaning weight. The influence of parity on traits measured at weaning was less than for traits measured at birth. Weight per pup born alive (WPP) was found to be a better indicator of reproduction and lactation ability than LWT because WPP accounts for preweaning mortality.     

Influence of prenatal and postnatal fraternity size on reproduction in swine

Hypotheses of a negative association between fraternity size (size of litter in which an individual develops prior to birth or is reared following birth) and ovulation rate or litter size were tested by examining reproduction of females born or reared in varying prenatal and postnatal fraternities. Gifts were randomly assigned to develop prenatally and be reared postnatal in small or large fraternities. Dams of experimental animals were randomly assigned to one of two prenatal fraternity size treatments, either unilateral oviductal ligation (to bear a small prenatal litter) or no ligation (to bear a normal prenatal litter). Whereas this did result in differences (P less than .01) in litter size at birth (small = 6.2 +/- .4 vs large = 9.6 +/- .9), there was considerable overlap in observed litter sizes between ligated and nonligated dams. Consequently, effects of prenatal fraternity size were examined by regression. Distinct differences in postnatal fraternity size were created by randomly assigning piglets to small (5 piglets) or large (10 piglets) postnatal fraternities within 24 h of birth. Differences in postnatal fraternity size were maintained through weaning at 3 wk (small = 4.9 +/- .1 vs large = 9.4 +/- .2). Weights at birth (regression of birth weight on prenatal fraternity size = -.07 +/- .02, P less than .01) and weaning (small = 6.09 +/- .15 vs large = 5.46 +/- .17 kg, P less than .01) were heavier for gilts from small prenatal and postnatal fraternities, respectively, compared with gilts from large fraternities. Effects of prenatal and postnatal size on BW did not persist following weaning (P greater than .20).     

The effects of crossfostering pigs on survival and growth

Data from 254 crossfostered pigs and 753 noncrossfostered pigs of Duroc and Landrace first-parity litters were used to assess the phenotypic effects of crossfostering on baby pigs. Differences between crossfostered and noncrossfostered pigs in the recipient litter were analyzed. Phenotypic correlations were calculated for selected individual pig traits (n = 1007, combined foster and nonfoster data). Birth weight was correlated positively with improved birth vigor (r = .40; P less than .01), survival to 21 d (r = .34; P less than .01) and weight at 21 d (r = .37; P less than .01). Improved birth vigor was correlated positively with pig survival to 21 d (r = .70; P less than .01) and to weaning (r = .66; P less than .01). These correlations indicate that baby pig size and strength are related and that these two characteristics influence survival and performance. Pigs that were not crossfostered (adjusted for birth vigor) had a 4.8% (P less than .10) higher rate of survival to 21 d and a 6.8% (P less than .05) higher rate of survival to weaning (42 d). However, crossfostered pigs had greater birth vigor (P less than .01). Unadjusted for vigor, crossfostered pigs had an 11.3% (P less than .01) higher rate of survival to 21 d and an 8.6% (P less than .05) higher rate of survival to weaning than noncrossfostered pigs. These results indicate that when average-strength pigs were crossfostered, livability was reduced. However, crossfostered pigs that were stronger than average had greater livability than pigs that were not crossfostered.(ABSTRACT TRUNCATED AT 250 WORDS)     

应用动物模型REML法估计金华猪繁殖性状遗传参数

试验资料取自金华猪场 1 979～1 999年金华猪繁殖性能的生产记录。采用动物模型约束性最大似然法 (REML)对该猪群的遗传参数进行估计 ,测定 1 1 4 4头纯繁金华母猪的产仔哺育记录。结果表明 ,产仔数 (TNB)、产活仔数 (NBA)、初生重 (PBW)、初生窝重 (LBW)、 2 0日龄头数(NFC)、 2 0日龄窝重 (LWFC)、 2 0日龄重 (PWFC)、 60日龄头数 (NW)、 60日龄窝重 (LWW)、 60日龄重 (PWW)、乳头数 (TN)的遗传力分别为0 1 2± 0 0 9、 0 1 8± 0 1 1、 0 1 5± 0 0 9、 0 0 2± 0 0 9、 0 1 0± 0 1 1、 0 0 8± 0 1 3、 0 1 8± 0 1 0、 0 2 3± 0 1 1、 0 31± 0 1 3、 0 35± 0 1 1和 0 1 9± 0 1 0。TNB与NBA、LBW、NW、LWW的遗传相关范围为 0 66～ 0 88,TNB与PBW的遗传相关为 - 0 43。NBA与LBW、NW、LWW的遗传相关范围为 0 60～ 0 64,NBA与PBW遗传相关为 - 0 63。PBW与PWW的遗传相关为 0 51。     

Traits affecting postweaning weight gain and feed intake of primiparous sows

Seventy-six primiparous Duroc and Landrace sows from two genetic lines with or without selection for improved sow productivity were used to identify sow traits that affect postweaning gain (positive or negative) and feed intake. Sows lost weight (P less than .01) and consumed less feed (P less than .01) during wk 1 postweaning (37 d) compared with wk 2, 3, and 4. Sows gained more weight during wk 2 and 3 (P less than .01) than during wk 4. Weekly feed consumption was similar during wk 2 and 4 and highest during wk 3 (P less than .05). Sow weight gain postweaning was predicted by sow weaning weight (P less than .01) and adjusted 21-d litter weight (P less than .05) during wk 1, wk 1 to 2, and wk 1 to 4 feeding periods. Feed consumption was best predicted by adjusted litter weaning weight (P less than .01), sow weaning weight (P less than .01), average backfat at farrowing (P less than .01), average backfat change (P less than .05), and adjusted 21-d litter weight (P less than .05). Feed intake was positively correlated (P less than .01; r = .77) and sow weight at breeding, farrowing, and weaning was negatively correlated (P less than .05; r = -.23, -.21, and -.26, respectively) with sow weight gain. Average backfat at weaning was negatively correlated (P less than .05) with gain and feed intake during each period. Adjusted 21-d litter weight and adjusted litter weaning weight were positively correlated with postweaning feed intake (P less than .05; r = .22 and .23, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)