母猪发情与配种

1发情1.1发情时间母猪发情周期平均21d(18～24d),经产母猪一般断奶后一周内(3～7d),可再次发情排卵,配种受孕,每次发情持续时间为3～5d,后备母猪比经产母猪持续时间长。1.2检查发情的方法1.2.1母猪喂料后0.5h和天黑前,每天进行2次发情鉴定上、下午各一次。     

高海拔条件下锌硒对猪繁殖性能的影响

通地对基础妊娠母猪、后备公母猪及哺乳仔猪饲料添加不同剂量的锌、硒 ,试验组和对照组比较 ,基础妊娠母猪产仔能力有显著的提高 ,断奶后再发情率和受胎率提高 ,断奶及发情时间缩短。后备母猪初次发情时间提前 ,初情期体重明显增加 ,产仔性能显著提高。生长发育后备公猪采精时间提前 ,睾丸发育迅速 ,射精量、精子活率和精子数量显著提高 ,精子畸形率降低。哺乳仔猪抗病力增强 ,成活率和平均断奶个体重明显提高     

犊牛的行为观察

1981年在上海崇明跃进奶牛场进行,观察初生至四月龄的健康黑白花奶犊。该场的续牛两周龄内在犊牛笼内饲养,两周龄后移至犊牛栏中饲养。喂奶的工具是奶桶,人工辅喂。两周龄内的犊牛每天喂三次,每次5斤,二周至二月龄的每天喂二次,每次5斤,二月龄后开始采用颈架,强制犊牛采食精料及草料,犊牛栏内饲养时每天刷拭三次,运动场上活动一次,时间3～4小时。本试验采用24小时连续观察法,分别记录了45头犊牛24小时内的主要行为——哺乳、采食、反刍、排泄、躺卧、睡眠、站立、     

母猪的发情鉴定及适时输精

1母猪的发情鉴定1.1发情周期特点母猪的发情周期为21d(17～25d),发情周期长短,在不同年龄和不同品种差异不大。正常情况下,无明显发情季节,但在严寒和酷暑季节,或饲养管理不良时,会暂时出现不发情或发情延迟。产后第1次出现发情时间与哺乳有关。一般在哺乳期间不发情,通常在断奶后4～7d发情。但也有少数母猪会在产后3～6d出现第1次发情,但持续期比断乳后发情约短2/3,多因不排卵而不能受孕,且其发情不易发现。如果在哺乳期间任何时候停止哺乳仔猪,则在4～10d后便可发情。后备母猪持续期为1～2d,经产母猪2～3d;断奶后第1次发情持续期比以后出…     

金华猪行为特性的观测

在定时充分喂饲等条件下,对金华猪妊娠后期和哺乳期某些行为的观测结果:日均采食风干料分别为4.48和5.96公斤;每100公斤体重相对采食量分别为4.45和5.96公斤:哺乳母猪采食置在产后30天左右达到高峰并持续10余天。日均饮水量分别为23.41和34.15公斤。一昼夜总排粪量分别为6.90和6.60公斤,均为6.7次。走动时间分别占全天时间的23.8％和20％;哺乳仔猪在30日龄左右活动最频凡。母猪产前平均14.88小时开始“闹圈”;12小时左右有初乳分泌;5小时左右乳汁变为乳白色;产仔持续时间平均为1.77小时。     

一种新型公猪信息素对无初情期记录的大龄后备母猪发情的影响实证

为了研究新型公猪信息素对大龄后备母猪发情的影响,选取526头255日龄左右无初情期记录的二元回交后备母猪,随机分为2组,试验组每天在鼻镜上喷新型公猪信息素4 mL,连喷21 d,21 d后还不发情的猪则并栏7 d应激,每天喷1次新型公猪信息素,每次4 mL;期间有发情表现的猪即可停止喷洒。对照组在相同条件下仅仅依靠人工查情,期间只要出现发情并且符合配种条件即可配种。分别统计每组的发情率,刺激-发情间隔。结果发现,在无初情期记录的大龄后备母猪.上每天喷4 mL新型公猪信息素,可显著提升后备母猪的发情比例(P<0.01),缩短刺激-发情的间隔(P<0.01)。由此得出,对大龄后备母猪使用新型公猪信息素28 d,可有效提升其发情率,缩短刺激-发情间隔。     

公猪诱情对后备母猪初情期和经产母猪断奶后发情配种的影响试验

就现在普遍存在的青年母猪性成熟及经产母猪断奶后发情延迟现象,我们于2002年在本场,进行了公猪诱情对后备母猪初情期和经产母猪断奶后发情配种的影响试验。选择本场4月龄大约克后备母猪48头,随机分成试验组和对照组,每组24头,每组6个重复(栏),每个重复4头。两组后备母猪饲养于环境条件完全相同的不同后备猪舍中,试验组后备母猪达160日龄起每天以栏为单位与成年公猪同栏接触2次,每次15～20分钟,直至初情期到来。对照组后备母猪不接触公猪。选择本场体况、胎次相近大约克经产断奶母猪32头,随机分为试验组和对照组,每组16头,每组4个重复(栏),…     

利用发情经产母猪诱情对后备母猪初情期影响的试验研究

选择5月龄丹系长白后备母猪60头,随机分成试验组和对照组,每组30头,每组5个重复(栏),每个重复6头。试验组达161日龄起每天以栏为单位与发情经产母猪同栏接触2次,每次15~20 min,直至180日龄;对照组达161日龄起每天以栏为单位与成年公猪同栏接触2次,每次15~20 min,直至180日龄。结果:试验组和对照组后备母猪180日龄内的初次发情率和初情期分别为63.33%、179.82 d和70.00%、176.54 d。表明2种诱情法的效果基本相同,都能有效促进后备母猪初情期提前,故利用发情经产母猪诱情代替公猪诱情是可行的。     

限量哺乳诱导泌乳母猪发情受精和对仔猪性能的影响

试验由126头带仔母猪及所带仔猪组成7个试验小组,从分娩后21天开始进行限量哺乳(LN),目的是观测限量哺乳对母猪在泌乳期中的发情、受胎率以及对仔猪生产性能的影响情况。试验分两期进行,前三个试验小组为一个试验期,组内二分之一的母猪每天给自己的仔猪哺乳4次,每次30分钟,持续12天;后4个试验小组为一个试验期,组内二分之一的母猪先每天给自己的仔猪哺乳4次3天,后每天哺乳3次4天(限量哺乳7天);两个试验期剩余的母猪按常规哺乳。所有仔猪限量哺乳期结束时全部断奶。结果前3个试验小组内26头限量哺乳的母猪有8头在断奶以前发情,常规哺乳的泌乳期未发现发情的母猪(p<0.01),限量哺乳和常规哺乳的母猪从断奶到再配种的平均间隔时间是1.7天和6.6天(p<0.01);后4个试验小组内37头限量哺乳的母猪有5头断奶前发情,常规哺乳的泌乳期也没有发现有发情的母猪(p<0.07),限量和常规哺乳的母猪从断奶到发情的平均间隔时间是3.3天和4.3天(p<0.05);母猪的受胎情况:虽限量哺乳期和哺乳方法不同,但母猪受胎率都差不多。仔猪性能:主要研究了仔猪断奶及断奶后14天的增重情况和限量哺乳期仔猪补料的摄入情况,结果试验期母猪限量哺乳养育的仔猪比常规哺乳养育的仔猪增重低(p<0.01)、饲料摄入量多(p<0.01)。断奶后,前3个试验小组限量哺乳养育的仔猪比常规哺乳养育的仔猪增重快(p<0.05),后4个试验小组内限量哺乳和常规哺乳养育的仔猪增重情况却差不多。整个试验中不同限量哺乳期及不同哺乳方法哺育的仔猪死亡情况也基本相同。     

不同饲喂次数对哺乳母猪生产性能及营养物质消化率的影响

选择妊娠107 d,3～4胎龄的健康母猪36头,随机分为4个处理,每个处理3个重复,每个重复3头母猪.试验期28 d,饲喂相同的饲粮,但处理1每天饲喂2次(每天上午7:30和下午5:30),处理2每天饲喂3次(每天上午7:30,12:30和下午5:30),处理3每天饲喂4次(每天早上6:30,上午10:30和下午1:30,6:30),处理4每天饲喂5次(每天早上5:30,上午9:00,12:30和下午4:00,7:30),考察不同饲喂次数对哺乳母猪生产性能和营养物质消化率的影响.试验结果表明,增加饲喂次数可以使母猪尽快恢复体况,减少产后不食的发生;适当增加饲喂次数,可以提高哺乳母猪的采食量,改善营养物质的消化率,增加泌乳量从而提高仔猪断奶重,并缩短母猪断奶后发情间隔天数;哺乳母猪每天饲喂3～4次为宜.     

Effects of postweaning dietary energy source on reproductive traits in primiparous sows

An experiment was conducted to study the effects of major dietary energy source fed from weaning to ovulation or from ovulation to d 35 of pregnancy on reproductive traits in primiparous sows. Dietary energy sources were used to manipulate the plasma insulin concentration. One hundred thirteen sows were used in a split-plot design. From weaning to ovulation sows were fed at two times maintenance either a diet with tallow (Fat) or maize starch plus dextrose (Starch) as the major energy source. From ovulation onward, sows within each dietary group were alternately reassigned to either the Fat or the Starch diet and were fed at 1.25 times maintenance. Estrus detection was performed three times a day from d 3 to 9 after weaning and sows were inseminated each day of standing estrus. On d 35 of pregnancy, the sows were slaughtered and their reproductive tracts were removed. Plasma insulin concentration was higher in sows fed the Starch-rich diet than in sows fed the Fat-rich diet on d 4 after weaning (1.30 vs 0.97 ng/mL, P = 0.08) and on d 32 of pregnancy (1.20 vs 0.51 ng/mL, P < 0.001). Plasma glucose and IGF-I concentration on d 4 after weaning and d 32 of pregnancy did not differ between sows on the two dietary energy sources. The percentage of sows exhibiting estrus within 9 d after weaning was 52 and 67% for the Fat and Starch diet before ovulation, respectively (P = 0.11), whereas the weaning-to-estrus interval was 134 vs 123 h, respectively (P = 0.12). Survival analysis showed that sows fed the Fat-rich diet had a 1.6 times higher risk to remain anestrous until d 9 after weaning than sows fed the Starch-rich diet (P = 0.04). No effect of dietary energy source, either before or after ovulation, on uterine, placental, or embryonal development on d 35 of pregnancy was found. It can be concluded that the dietary energy source provided after weaning can affect the risk of sows to remain anestrous but does not affect uterine, placental, or embryonic traits.     

皖南花猪泌乳力的研究

抽选２～９胎次的皖南花哺乳母猪６头,每头母猪带仔１０～１４头,有效乳头数７对。试验母猪日粮含ＤＥ１１．７２ＭＪ／ｋｇ和ＣＰ１２％,取日粮２．５～３．０千克,按１２与青绿多汁饲料混合打匀投喂。供试母猪自分娩开始,每５天进行一次泌乳量测定,直到产后泌乳５０天。利用线性模型校正不同胎次和带仔数的泌乳量,再采用一元高次方程进行泌乳曲线分析。结果表明,皖南花猪泌乳高峰期在分娩后的第１０～１５天,其间平均泌乳量为５．６６～５．９１ｋｇ／天,分娩后的第３５天泌乳量为３．７ｋｇ／天。不同乳头的泌乳量为第１、２和３号乳头最高,平均每个单乳头泌乳３８０～３８５ｇ／天,向后乳头的泌乳量呈下降趋势,第７号乳头泌乳量为３００．５ｇ／天。不同泌乳阶段表现出明显的节律性,泌乳曲线方程的拟合度均在０．９０以上。     

藏猪在舍饲条件下的行为观察

对藏猪在舍饲条件下的行为特性进行了观察，结果表明：一天内母猪走动时间约占15％－25％，臣息时间占75％－85％，一天内妊娠母猪排粪5－6次，藏母猪性成熟早，发情特征明显，情期长，青年母猪70－85日龄出现性行为，母猪产前20h开始出现闹圈等一系列产前行为，产仔持续时间1．9－4．2h，母猪一天哺乳25次，仔猪拱乳时间52－57s，母猪持续放乳15－26s，藏猪调圈或合群后经咬斗过程，在一周内建立新的位次序列，藏猪耐粗食，抗逆性强，对高原恶劣的气候条件有独特的适应能力，并具有良好的定圈能力。     

Effect of housing system and boar exposure on estrus expression in weaned sows

Reproductive efficiency depends on detection of estrus, which may be influenced by housing and boar exposure. This experiment investigated the effects of housing system and boar contact on measures of estrus in weaned sows. Mixed-parity sows were randomly assigned to be weaned into gestation crates away from boars (AWC, n = 45), into pens away from boars (AWP, n = 42), or into pens adjacent to a mature boar (ADJ, n = 46). Estrus detection was initiated at approximately 0700 (0 h) and again at 0.25-, 0.5-, 1-, 2-, 4-, and 8-h intervals beginning on d 4 and continuing through d 7 following weaning. Estrus detection involved observation of the standing response after application of nose-to-nose boar exposure, backpressure, and side rubbing. For the AWC sows, a mature boar was moved to the front of the crates for a 10-min period and then removed. Sows housed in AWP were moved approximately 15 m to an empty pen adjacent to a mature boar for a 10-min period, and then returned to their pen. Sows housed ADJ were not moved and estrus detection was performed in their home pen for a 10-min period. The proportion of sows expressing estrus within 7 d from weaning was lowest for ADJ (80%, 37/46) compared with AWP (98%, 41/42) and AWC (96%, 43/45; P < 0.05). There was an effect of interval from weaning to estrus on the percentage of sows expressing estrus, but there was no interaction with treatment. Sows in AWC and AWP (4.7 d) had decreased (P = 0.01) intervals from weaning to estrus compared with ADJ (5.2 d). The duration of estrus was also shorter (P < 0.001) for ADJ (45 h) compared with AWC (58 h) or AWP (62 h). There was a treatment x interval x day of estrus effect for the percentage of sows expressing estrus. After detection of the first standing response on the first day of estrus, only 62 to 82% of sows were detected standing over the next 2 h for all treatments. However, at 4 to 8 h, this increased to 85 to 98% for the AWC and AWP sows, but <73% of the ADJ sows were detected during this period. On the second day of estrus, estrus expression was not influenced by interval for the AWC and AWP sows and was between 90 to 100% during the 8-h period, whereas ADJ sow detection rates were between 68 to 88%. These data suggest that housing sows adjacent to boars negatively affects estrus expression and detection. In addition, refractory behavior occurs in approximately 30 to 40% of sows and is influenced by housing relative to the boar, day of estrus, and interval from last boar exposure.     

Reproductive, metabolic, and endocrine responses to feed restriction and GnRH treatment in primiparous, lactating sows

The current experiment was carried out to determine whether exogenous GnRH treatment in primiparous, lactating sows undergoing feed restriction would improve reproductive performance after weaning. Sows were allocated to one of three treatments: AA sows (n = 8) were fed to appetite throughout a 28-d lactation, AR (n = 12) and AR + GnRH (n = 12) sows were fed as AA sows from farrowing to d 21 of lactation, and feed intake was reduced to 50% of the ad libitum intakes from d 22 to 28. The AR + GnRH sows received 800 ng of GnRH i.v. every 6 h from d 22 to 28 of lactation, and AA and AR sows received saline. Sow weight, backfat, and litter weight were recorded weekly. Within 2 d after farrowing, litter size was standardized to 8 to 10. At d 17 of lactation, an indwelling jugular catheter was surgically implanted in each sow. Blood samples were taken for characterization of plasma LH, FSH, insulin, IGF-I, and leptin by RIA at d 21 and before and after weaning on d 28 of lactation. After weaning, all sows were given ad libitum access to feed, checked for onset of standing estrus twice daily with mature vasectomized boars, and inseminated 12 and 24 h after onset of standing estrus with pooled semen from the same fertile boars (3 x 10(9) sperm/AI). After breeding, feed allowance was reduced to NRC (1988) requirements for gestation. At d 28 +/- 3 of gestation, sows were killed and ovulation rate and embryo survival were determined. Restricted sows lost more weight during lactation than AA sows (P < .02). During the period of feed restriction, plasma IGF-I and postprandial insulin and leptin in AR and AR + GnRH sows, and LH pulse frequency in AR sows, were lower than those in AA sows (P < .04). Associations (P < .004) between plasma insulin and leptin and between leptin and mean LH concentrations were established. The LH pulse frequency in AR + GnRH sows did not differ from that in AA sows before weaning. After weaning, maximum, mean, and minimum LH concentrations in the AA and AR sows, and FSH concentrations in AR sows, increased (P < .05) in response to weaning. Paradoxically, GnRH treatment in lactation seemed to suppress the expected LH and FSH responses to weaning. Ovulation rate and embryo survival were not different among the three groups. In conclusion, although exogenous GnRH therapy restored LH secretion in feed-restricted sows, it did not improve overall reproductive performance.     

Responses to delayed estrus after weaning in sows using oral progestagen treatment

Oral progestagen treatment extends the weaning-to-estrus interval (WEI) in weaned sows. Particularly in lower parity sows, this allows recovery from lactational catabolism and improves sow productivity. However, the optimal duration of progestagen treatment in contemporary dam-line sows is unclear. Therefore, sows (n = 749) weaned over consecutive 3-wk periods in June and July and classified as parity 2 and 3 (P2-3); 4, 5, and 6 (P4-6); or parity 7 or higher (P7+) were organized into 2 breeding groups using 1 of 3 strategies: 1) oral progestagen for 2 d before and 12 d after weaning (M14; n = 249); 2) oral progestagen for 2 d before and 5 d after weaning (M7; n = 250); or 3) no progestagen treatment (M0; n = 250). Progestagen (altrenogest) was administered directly into the sow's mouth at a dosage of 6.8 mL (15 mg of altrenogest) daily. Sows were bred using artificial insemination at first detection of estrus after weaning (M0) or altrenogest withdrawal, and every 24 h thereafter, until they no longer exhibited the standing reflex. The WEI for M0 sows was 5.1 +/- 0.1 d. Estrus was recorded sooner (P < 0.001) after withdrawing treatment in M14 than in M7 sows (6.9 +/- 0.1 vs. 7.4 +/- 0.1 d, respectively). More (P < 0.001) M14 sows (88.6 +/- 2.5%) were bred within 10 d of altrenogest withdrawal than M7 (72.8 +/- 2.8%) sows, or within 10 d of weaning in M0 sows (78.8 +/- 2.6%). Reproductive tracts were recovered after slaughter at d 30 or 50 of gestation. For P2-3 sows, ovulation rate (least squares mean +/- 95% confidence interval) in M7 (23.1 +/- 1.0) was greater (P < 0.001) than in M14 (20.7 +/- 1.0) or M0 (19.7 +/- 1.0) sows; no differences were detected in P4-6 and P7+ sows. At d 30, M7 and M14 sows had more (P < 0.01) embryos (16.4 +/- 0.6 and 15.8 +/- 0.4, respectively) than M0 (13.9 +/- 0.5) sows. At d 50 of gestation, number of fetuses in M14 sows (13.6 +/- 0.4) was greater (P < 0.001) than in M0 (11.8 +/- 0.4) and M7 (12.2 +/- 0.3) sows. Use of oral progestagen to delay the return to postweaning estrus for greater than 18 d appears to have potential for improving weaned sow productivity. Given the incidence of high ovulation rates and associated evidence of intrauterine crowding of embryos around d 30 of gestation, the changing dynamics of prenatal loss resulting from longer periods of progestagen treatment may represent an additional production advantage.     

Circulating biomarkers associated with pelvic organ prolapse risk in late gestation sows

Sow mortality, as the result of pelvic organ prolapse (POP), has been increasing in the last decade in the U.S. swine industry. The objective of this study was to identify potential biological markers associated with risk of POP in sows. We hypothesized that sows differing in perineal score (PS) from PS1–PS3 (PS1—a presumed low POP risk; PS2—a presumed moderate POP risk; and PS3—a presumed high POP risk) would differ in circulatory biomarkers of inflammation and hormonal profiles. On gestation week 15, 2,864 individual sows were assigned a PS, and subsequently, 1.0%, 2.7%, and 23.4% of PS1, PS2, or PS3 sows, respectively, experienced POP. During PS assignment at days 107–116 of gestation, blood samples were collected from sows on two farms of similar genetics, feed sources, and health status. Whole blood was subjected to complete blood count (CBC) analysis (n = 212) and steroid hormones were measured in serum from a subset (n = 110) of animals assigned PS3 parity matched to PS1. Lipopolysaccharide-binding protein (LBP), tumor necrosis factor-alpha (TNF-α), haptoglobin, C-reactive protein (CRP), and creatine kinase (CK) levels were also evaluated. Complete blood count analysis revealed decreased (P ≤ 0.05) mean platelet volume (3.9%), lymphocytes (6.5%), and monocytes (7.5%) in PS3 compared to PS1 sows. Increased (P ≤ 0.02) abundance of androstenedione (13.4%), androsterone (18.2%), estrone (24.8%), and 17β-estradiol (26.2%) was observed in PS3 compared to PS1 sows. Additionally, a 25.8% increase (P = 0.04) in LBP in PS3 compared to PS1 sows was observed. Many dynamic physiological changes occur in sows during late gestation as they approach farrowing. The data presented herein demonstrate that distinct differences in concentrations of circulating biomarkers exist between late gestation sows at high or low risk for POP and may serve as a useful tool for understanding the etiology of POP and evaluation of mitigation strategies.     

Morphine suppresses luteinizing hormone concentrations in transiently weaned sows and delays onset of estrus after weaning

Lactating sows were used to evaluate effects of morphine and suckling on secretion of LH and prolactin (PRL) and occurrence of estrus after weaning. In the first experiment, crossbred multiparous sows nursing 7.9 +/- .4 pigs per litter at 25.2 +/- .3 d of lactation were subjected to one of three treatments during the middle 8-h segment of a 24-h experimental period. Treatments were infusion (i.v.) of morphine (200 mg/h) with the litter present (n = 4) or transiently weaned (n = 4), or transient weaning of litters without morphine (n = 4). Transient weaning decreased (P less than .05) prolactin and increased (P less than .05) the frequency of LH pulses and average concentration of LH. Infusion of morphine caused transient hyperthermia and suppressed (P less than .05) LH release in two of four sows nursing litters and in four sows whose litters were absent. Infusion of morphine, in the presence or absence of litters, suppressed PRL during the middle and last 8-h segments. A second experiment was conducted to test the hypothesis that chronic administration of morphine delays onset of estrus after weaning. Primiparous Duroc sows were assigned at weaning (53 to 63 d postpartum) to receive morphine (n = 10) or saline (n = 11). Saline (1.5 ml) or morphine (75 mg) was administered s.c. three times a day for 5 d after weaning. Onset of estrus after weaning was delayed in sows given morphine compared with those given saline (9.7 +/- .4 vs 5.2 +/- .3 d, respectively; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Dietary energy source at two feeding levels during lactation of primiparous sows: II. Effects on periestrus hormone profiles and embryonal survival

Our objective was to study the effects of dietary energy source (fat or starch) on periestrus hormone profiles and embryonal survival in primiparous sows. During lactation, 48 primiparous sows were fed either a starch-rich or a fat-rich diet, at either a high (44 MJ NE/d) or a low (33 MJ NE/d) feeding level. After weaning, all sows received the same amount of feed (31 MJ NE/d from weaning to estrus and 17.5 MJ NE/d from breeding to slaughter) of the same dietary energy source fed during lactation. Around estrus, blood samples were taken to analyze the preovulatory LH surge, estradiol (E2), and progesterone (P4). Sows were inseminated on each day of standing estrus. On d 35 after last insemination, all 35 pregnant sows were slaughtered and their reproductive tracts were removed. The number, weight, and length of the embryos and placentas were determined as well as the weight and length of the uterus. The LH, E2, and P4 profiles were similar for the treatment groups, except for the E2 levels at 16, 12, and 8 h before the LH surge, which were lower in the sows fed the fat-rich diet at a low level. Ovulation rate tended to be higher in sows fed the high compared to the low feeding level during lactation (18.0 vs. 16.2; P = .09), but the number of total and viable embryos as well as embryonal survival rate were not influenced by the treatments. Neither uterine length and weight nor length and weight of the embryos and placentas were affected by treatments. However, after removal of the embryo-placental units, uterine weight was greater in sows fed the high than in those fed the low feeding level during lactation (1.8 vs. 1.6 kg; P = .03). Plasma insulin concentration during lactation was not related to any of the uterine, placental, or embryo traits. Mean progesterone concentration between 24 and 250 h after the LH surge was positively correlated with embryonal survival. Differences in progesterone concentration between sows with high and low embryonal survival were evident from 172 h after the LH surge. From the present study, we conclude that altering feeding level during lactation or dietary energy source from farrowing until d 35 of subsequent pregnancy did not affect embryonic development and embryonal survival.     

Measurement of blood flow through the mammary gland in lactating sows: methodological aspects

Two replicates of three multiparous crossbred Large White x Landrace lactating sows were used to develop a technique for the continuous direct measurement of the blood flow through the mammary gland using transit time ultrasound. Four to six days after farrowing, an ultrasonic transit time flow probe was implanted around the right external pudic artery in order to measure the short-term variations of mammary blood flow through this vessel in response to postural change (standing vs lying), meal distribution, hand-milking, and weaning. After surgery, all sows were fed 3.8 kg/d of a lactation diet and housed either at 20 or 28 degrees C. The implantation of the ultrasonic blood flow probe was successful in all six operated sows. Postmortem examination did not indicate the presence of infection, any collateral bypassing the flow probe, or a reduction of artery diameter. The right pudic artery mammary blood flow (PMBF) was measured for 8.5 h over two periods of three days (d 11 to d 13 and d 18 to d 20 of lactation). The PMBF averaged 910 +/- 238 mL/min but was variable within 1 d. Compared with the lying position, PMBF was decreased (- 6%, P < 0.05) when sows were standing. Between 0 to 15 and 16 to 30 min after oxytocin injection (t = 0) and hand-milking, PMBF remained constant (P = 0.05; 801 vs 767 mL/ min) and increased (P = 0.02), respectively, in comparison with the mean calculated over the preceding 30-min period (982 vs 784 mL/min). The PMBF increased (P < 0.05) after meal distribution and reached a peak 65 min later (i.e., 980 mL/min). The PMBF decreased regularly after separation of piglets at weaning; at 8 and 16 h after weaning, PMBF was 60 and 40% of the value recorded before weaning, respectively. Assuming that PMBF drains one-quarter of the whole mammary gland, it can be calculated that blood flow through the entire mammary gland averages 3.6 L/min and that about 470 L of blood are required to produce 1 kg of milk. The proposed methodology constitutes a new technique to measure direct mammary blood flow and its short-term factors of variation.