Accounting for lactation length and weaning-to-conception interval in genetic evaluations for litter size in swine

Effects of lactation length and weaning-to-conception interval on the subsequent litter size of purebred sows were estimated using an animal model. Data on 2,847 Landrace sows with 7,125 litters born between January 1989 and May 1997 and on 1,234 Yorkshire sows with 2,999 litters born between January 1990 and May 1997 were obtained from two Canadian selection herds. Sows having a lactation of less than 14 d (MMEW) were usually not mated until their second estrus, whereas sows weaned after at least 14 d of lactation (later weaning) were usually mated on their first estrus. Litter size included both number of pigs born alive and those stillborn. Linear, quadratic, and logarithmic effects of lactation length were tested. The effect of weaning-to-conception interval on litter size was modeled using an approach based on threshold variables and an approach using segmented polynomials. Results indicated linear and logarithmic effects of lactation length on subsequent litter size for Yorkshire and Landrace breeds, respectively. Litter size decreased as weaning-to-conception interval increased up to 7 and 10 d for Yorkshire and Landrace, respectively, then increased with further increases in weaning-to-conception interval up to 35 and 30 d for the two breeds, and then remained constant. The MMEW sows did not have lower subsequent litter sizes than later-weaned sows because the negative effect of a shorter lactation was offset by the positive effect of a longer weaning-to-conception interval. However, average time spent open per parity was longer for MMEW sows than for later-weaned sows. Both lactation length and weaning-to-conception interval should be considered in models for the genetic evaluation of litter size in purebred swine. Segmented polynomials can be used to predict litter size as a continuous function of weaning-to-conception interval or to derive weaning-to-conception interval adjustment factors for litter size.     

Influence of duration of litter separation and boar exposure on estrous expression of sows during and after lactation

The influence of litter separation (LS) that included a change in housing environment and social status of sows, boar exposure (BE), and parity on estrous expression by sows during and after lactation was examined in two experiments utilizing 140 crossbred sows. In Exp. 1 (Yorkshire X Duroc sows), limiting duration of LS to 6 or 3 h/d during the last 8 d of lactation in two trials, while maintaining 1 h BE, resulted in similar proportions of sows in estrus during lactation (65 vs 79% for 3- and 6-h sows). However, 6-h LS tended to reduce (P = .08) the interval to estrus by .6 d for those sows that expressed a preweaning estrus. Postweaning intervals to estrus were unaffected by duration of LS in the remaining sows. In Exp. 2, sows (Yorkshire X Duroc X Chester White) were assigned to four treatment groups during the last 8 d of lactation: 1) BE (1 h/d), 2) LS (6 h/d), 3) LS + BE and 4) no LS + no BE (control). Only nine sows expressed estrus during lactation; four of 28 LS sows and five of 28 LS + BE sows. No sows were in estrus before weaning during August 1985 and only one sow (LS group) was in estrus before weaning during October 1986. Postweaning intervals to estrus were reduced (P less than .05) by .9 d after preweaning BE compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of recombinant porcine somatotropin on lactational performance and metabolite patterns in sows and growth of nursing pigs

Sixteen crossbred sows (Yorkshire x Duroc) were used to determine the effect of recombinantly derived porcine somatotropin (pST) on lactational performance and the pattern of plasma metabolites and growth rate of nursing pigs. Daily s.c. injections of either pST (8.22 mg.sow-1.d-1) or excipient were administered at 1000 on d 12 through d 29 of lactation. Jugular cannulas were inserted in three sows/treatment and hourly blood samples were collected on d 11 to 13 and d 28 to 29 of lactation to determine the effect of treatment on plasma concentrations of somatotropin, glucose and nonesterified fatty acids in plasma. Milk production and weight of nursing pigs were determined pretreatment (d 9 and 10) and on d 16, 22 and 28. Milk production of sows receiving pST progressively increased above that of control sows and was 22% greater on d 28. Milk composition was not affected by treatment with pST (P greater than .10), so that the increase in yields of milk fat, lactose and solids paralleled the increases in milk yield. Total milk protein yield tended to be higher in sows receiving pST, but protein yield was greater (P less than .10) only on d 28. Pigs suckling sows treated with pST weighed .34 kg more at the end of the lactation period (P less than .05). Sows receiving pST consumed less feed (P less than .05) during the treatment period, and, as a result, lost more weight (P less than .10) and backfat (P less than .05) than control sows. Average concentrations of plasma somatotropin were elevated approximately 2.5-fold above baseline levels by exogenous pST. No acute alterations in plasma glucose or nonesterified fatty acids were observed in response to pST treatment, however, sows receiving pST had a chronic elevation of plasma glucose on d 29 of lactation.     

Lactation performance of sows injected with growth hormone-releasing factor during gestation and(or) lactation.

Fifty-two Yorkshire x Landrace gilts were equally allotted to four treatments: 1) controls, saline injections (CTL); 2) injections of 12 mg of growth hormone-releasing factor (GRF) (1-29)NH2 thrice daily (0700, 1500, and 2300) from d 100 of gestation until parturition (GEST); 3) injections of GRF thrice daily from d 3 to 29 of lactation (LACT); and 4) injections of GRF thrice daily during gestation (d 100 to parturition) and lactation (d 3 to 29) (GEST-LACT). Within 48 h of birth, litters were standardized to 9 +/- 1 pigs. Weights of the pigs were recorded weekly from birth (less than 24 h) until weaning (d 30) and on d 42 and 56. Weights of gilts at mating, d 110 of gestation, 1 d postfarrowing, and at weaning also were recorded. On d 24 of lactation, milk yield was estimated by the weigh-suckle-weigh method, and a representative milk sample was obtained the next day. Jugular vein cannulas were inserted into six sows per treatment on d 26, and a 6-h blood profile (sampling every 20 min from 0600 to 1200) was obtained on d 29. Daily feed consumption of sows was recorded throughout the study. Weights of the pigs at any one time or survival until weaning were not affected by treatments (P greater than .1). Sows injected with GRF during GEST (P = .05) and(or) LACT (P less than .01) were lighter than CTL sows at weaning; in addition, sows treated during lactation had less backfat (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of protein intake during gestation and lactation on the lactational performance of primiparous sows.

The effect of protein intake during gestation and lactation on the lactational performance of primiparous sows was evaluated using 35 Yorkshire x Landrace gilts, allocated to six dietary treatments in a 3 x 2 factorial arrangement. Treatments consisted of three protein levels during gestation, providing approximately 4, 8, and 16 g of lysine/d, and two protein levels (low [L] and high [HI), providing approximately 15 and 45 g of lysine/d, during lactation, respectively. Diets provided similar amounts of ME and all other nutrients. As dietary protein increased during gestation, sows gained more weight and tended to decrease their backfat thickness. There was no gestation x lactation treatment interaction for lactational performance of sows. Feed intake by sows during lactation was usually low but increased (P < .05) with increasing gestation and lactation protein intake and increased linearly (P < .001) as lactation progressed. This linear increase over time was greater (P < .05) in sows fed the H than in sows fed the L protein level. Increased protein intake during lactation reduced (P < .001) 21-d sow weight loss. Milk yield and pig weight gain increased as protein intake increased during gestation (P < .05) and lactation (P < .01). Milk yield did not increase as lactation progressed (P > .05). Pig weight gain increased (P < .05) from wk 1 to 2 of lactation and decreased thereafter. Simple linear regression analysis detected few important relationships between yield of milk components and metabolites or metabolic hormone concentrations. The R2 values for these relationships were < or = .30, except for some relationships between milk component yields and blood urea nitrogen (the range was between .17 and .55). Covariate adjustment for metabolite and metabolic hormone concentrations did not eliminate treatment effects in most cases. This suggests that effects of increased protein intake on milk yield are not fully mediated through metabolite and metabolic hormone concentrations.     

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。     

Lactational variation and relationship to postnatal growth of insulin-like growth factor-I in mammary secretions from genetically diverse sows

Mammary secretions obtained from four groups of sows at parturition and on days 7, 14 and 21 of lactation were defatted and assayed for total protein and insulin-like growth factor-I (IGF-I). Sows (n = 57) represented two breeds (Landrace and Duroc) and two genetic lines (selected for differences in sow productivity index, SPI) within each breed. Colostrum of Duroc sows was 4-6 fold and 30-60 fold greater in protein (P less than .001) and IGF-I (P less than .001) concentrations, respectively, than the corresponding day 7 milk from these sows. In contrast, the colostrum of Landrace sows was 2-3 fold and 30-50 fold greater in protein (P less than .001) and IGF-I (P less than .001) concentrations, respectively, than the corresponding day 7 milk. The IGF-I content in milk from Duroc sows did not differ among days 7, 14 and 21 of lactation, whereas the IGF-I content of day 7 milk from Landrace sows exceeded those for the corresponding 14 day and 21 day secretion (P less than .05). IGF-I concentration in days 14 and 21 milk was higher in Duroc (P less than .001 respectively) than Landrace sows. No significant differences in total protein or IGF-I content of mammary secretions were observed between the selected and control lines within each breed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Estimates of genetic parameters associated with lactation feed intake and growth and composition traits measured during a performance test

Days to reach 113.4 kg, adjusted backfat depth and adjusted loin muscle area to 113.4 kg were evaluated on pure‐bred Landrace (n = 15 660) and Yorkshire (n = 14 808) boars and gilts. Daily lactation feed intake (LFI) was recorded within parity records from pure‐bred Yorkshire (n = 1587) and Landrace (n = 2197) females during day 1–22 of lactation, and LFI curves were predicted using a mixed model. Evaluation of feed intake differences between 2 consecutive days of lactation resulted in the following periods: day 1–6 (PB1), day 7–10 (PB2) and day 11–18 (PB3). Average rate of change in intake (ARC), average daily intake (ADI) and variation from predicted daily LFI values (VAR) metrics were computed for each period of lactation. Gibbs sampling was used to estimate the genetic covariance between LFI metrics and grow‐finish traits. Genetic correlations were strongest between grow‐finish traits, and LFI metrics in first parity sows and were generally favourable, but correlations with LFI metrics during parity 2 or greater were low and not different from 0 (p > 0.05). Genetic correlations between LFI metrics in parity 1 sows with growth and composition traits varied greatly in strength and direction. Selection for leaner, heavier muscled gilts had a limited effect on LFI metrics. However, selection for increased growth rate was associated with higher ARC and ADI and smaller VAR values.     

Characterization of luteinizing hormone secretion in the primiparous, lactating sow: relationship to blood metabolites and return-to-estrus interval.

Lactating, primiparous Landrace x Yorkshire sows were used to characterize LH secretion during lactation in sows that experienced an early (less than 9 d; n = 14) or late (greater than 15 d; n = 9) return to estrous postweaning and to evaluate the relationship between LH secretion and blood metabolites. Twenty-three sows were fed one of nine corn-soybean meal diets to achieve a matrix of lysine (15 to 45 g/d) and energy (6.5 to 16.5 Mcal of ME/d) intakes and a range in metabolite concentrations and return-to-estrus intervals. Blood samples for LH analysis were collected every 15 min for 6 h on d 0, 7, 14, 21, and 28 of lactation. Circulating concentrations of glucose, amino acids, insulin, triglycerides, urea N, and nonesterified fatty acids also were measured on d 7 and 21. Mean LH concentrations were .27 and .42 ng/mL at farrowing for sows with an early and late return to estrus, respectively, but decreased (P less than .01) to .12 ng/mL by d 7 in both early and late groups. Mean LH and number of LH peaks per 6 h increased linearly (P less than .01) from d 7 to 28 for early sows. Early sows had a higher LH mean and more LH peaks per 6 h on d 14, 21, and 28 than did late sows (P less than .05). Early sows had higher serum insulin on d 7 (P less than .05) and d 21 (P less than .01) than did late sows. Concentrations of other metabolites did not differ (P less than .10) between early and late sows.(ABSTRACT TRUNCATED AT 250 WORDS)     

低磷低蛋白日粮添加植酸酶和氨基酸对泌乳母猪粪氮磷排出量的影响

选择3~7胎长白×大白二元杂交母猪45头,随机分为3个组,每个组15头,泌乳期21 d。处理1组的日粮粗蛋白为18%、总磷为0.68%;处理2组的日粮粗蛋白为16.5%、总磷为0.58%;处理3组的日粮粗蛋白为15%、总磷为0.58%;处理2组和处理3组日粮中添加植酸酶。结果表明,日粮蛋白质降低1.5~3个百分点和总磷降低0.1%,对泌乳母猪的采食量和哺乳仔猪日增重无显著影响,母猪泌乳期体重损失显著减少,粪氮和磷的排放量显著减少。     

二花脸猪乳中生长因子的动态分析及其与大约克猪的比较

通过 2个系列实验 ,分析了二花脸猪乳中生长因子 (IGF Ⅰ、EGF和胰岛素 )在泌乳早期 (1～ 2 1d)的含量及其变化规律 ,并与大约克猪进行了比较研究。结果表明 ,二花脸和大约克猪乳中IGF Ⅰ在初乳中浓度很高 ,分娩 1周后迅速下降 ,泌乳第 7～ 2 1天变化不大。在泌乳第 1～ 7天 ,二花脸猪乳中IGF Ⅰ低于大约克猪 ,泌乳第 7天以后又高于大约克 ,但 2种猪的差别不显著 (P >0 0 5)。猪乳中的EGF变化规律基本上和IGF Ⅰ相同。在泌乳第 1天 ,二花脸猪乳中的EGF显著低于大约克猪 (P <0 0 5) ,第 1天以后 2种猪没有明显差异。二花脸和大约克猪乳中的胰岛素在初乳很高 ,产后 4d迅速下降 ,4d以后变化幅度不大。二花脸猪乳中的胰岛素在泌乳早期 (1～ 2 1d)全都低于大约克猪 ,其中在泌乳第 1天、第 6～ 7天、第 8～10天和第 11～ 14天这 4个阶段显著低于大约克猪 (P <0 0 5)。     

Nucleotides in sow colostrum and milk at different stages of lactation

An experiment was conducted with the objective of measuring the concentrations of total milk solids (TMS), CP, and 5'monophosphate nucleotides in sow colostrum and milk. Twelve multiparous sows (Landrace x Yorkshire x Duroc) were used. Litter size was standardized at 11 piglets for all sows at farrowing. Sows were fed an 18.45% CP corn-soybean meal-based diet throughout lactation. The experimental period was the initial 28 d of lactation, with colostrum collected within 12 h of farrowing and milk collected on d 3, 7, 14, 21, and 28. Colostrum and milk samples were analyzed for TMS, CP, adenosine 5'monophosphate (5'AMP), cytidine 5'monophosphate (5'CMP), guanosine 5'monophosphate (5'GMP), inosine 5'monophosphate (5'IMP), and uridine 5'monophosphate (5'UMP). Total milk solids decreased (P < 0.05) from 26.7% on d 0 to 23.1% on d 3. The TMS further decreased (P < 0.05) to 19.3% on d 7, but remained relatively constant thereafter at 18.2, 18.8, and 19.2% on d 14, 21, and 28, respectively. The concentration of CP decreased from 16.6% in colostrum to 7.7, 6.2, 5.5, 5.7, and 6.3% in milk collected on d 3, 7, 14, 21, and 28, respectively (linear and quadratic effect; P < 0.05). Concentrations of 5'AMP, 5'CMP, 5'GMP, and 5'IMP increased from d 0 to d 3 and d 7, and then decreased during the remaining lactation period (quadratic effect; P < 0.05). The concentration of 5'UMP decreased from d 0 to 28 of lactation (linear and quadratic effects; P < 0.05). In colostrum, 5'UMP represented 98% of all 5'monophosphate nucleotides, and in milk, 5'UMP accounted for 86 to 90% of all nucleotides, regardless of day of lactation. The results of this experiment suggest that the concentrations of TMS and CP in sow mammary secretions changed during the first week of lactation, but were constant thereafter. Likewise, the concentrations of 5'monophosphate nucleotides changed during the initial week postpartum, but during the last 2 wk of a 4-wk lactation period, the concentrations were constant.     

Dietary protein concentration affects plasma arteriovenous difference of amino acids across the porcine mammary gland

The objective of this study was to determine whether the porcine mammary gland responds to increasing dietary CP concentration through changes in AA arteriovenous difference (a-v). Sixteen Landrace x Yorkshire lactating sows were provided ad libitum access to one of four isocaloric diets varying in CP concentration (7.8, 13.0, 18.2, and 23.5 %; as-fed basis). Litters were adjusted to 11 pigs within 48 h of birth. Sows were fitted with catheters in the carotid artery and main mammary vein on d 4. On d 10, 14, 18, and 22 of lactation, arterial and venous blood samples were obtained every 30 min over 6 h. Milk yield was estimated on d 11 and 21 using the D2O dilution technique. Final litter sizes on d 21 were 10.3, 11, 9.5, and 11 piglets for sows fed the 7.8, 13.0, 18.2, and 23.5% CP diets, respectively. Piglet ADG tended (P = 0.088) to increase with increasing dietary CP concentration and were 186, 221, 220, and 202 g for sows fed the 7.8, 13.0, 18.2, and 23.5% CP diet, respectively. Daily total milk yield on d 21 (kg milk/d) tended (P = 0.099) to increase, and average milk yield per nursed piglet (kg of milk-pig(-1)d(-1)) increased (P < 0.05) with increasing CP concentration and were, on a per-piglet basis, 0.95, 1.19, 1.14 and 1.13 kg of milk/d for the 7.8, 13.0, 18.2, and 23.5% CP diets, respectively. As dietary CP increased from 7.8 to 23.5%, isoleucine and leucine a-v increased linearly only (linear, P < 0.01); all other AA a-v increased, reached a maximum in sows fed 18.2% CP, and decreased thereafter in sows fed 23.5% CP (quadratic, from P = 0.10 to P < 0.05). Amino acid uptake by the entire udder and by each gland increased (linear, P < 0.05) with increasing dietary CP. Arteriovenous differences response to increasing day of lactation varied among AA, from no change for histidine, isoleucine, lysine, methionine, tryptophan, and valine, to a linear trend increase for arginine (P = 0.055), leucine (P = 0.064), phenylalanine (P = 0.101), and threonine (P = 0.057). In summary, for the majority of AA, a-v increased with increasing dietary CP concentration from 7.8 to 18.2%, but decreased when CP concentration exceeded 18.2%. In contrast, mammary AA uptake, piglet ADG and milk yield per pig increased linearly with increasing dietary CP, suggesting a coordinated regulation between AA delivery and transport to meet the demand for milk yield.     

Composition of sow milk during lactation

The composition of sow colostrum and milk was quantitated in 25 sows at 14 time points throughout lactation. All animals belonged to the same experimental herd of German Landrace, farrowed within 4 d, and were of various lactation numbers and various litter sizes. In the first 6 h of lactation colostrum total solids (TS) and protein contents were higher, while fat and lactose contents were lower than in mature milk. Decreased total protein and whey protein contents and concomitantly increased fat and lactose content, with nearly unchanged TS levels, indicate transition from colostrum to mature milk. The high protein content of colostrum was largely due to immunoglobulin (Ig). During the first 6 h, IgG accounts for nearly all the protein in colostrum but plays a decreasing role in sow milk as lactation proceeds. After 2 wk, IgA levels begin to increase and at the end of lactation, IgA constitutes 40% of the total whey protein. No influences of lactation number and litter size on milk composition could be ascertained in this study.     

胎次对杜洛克、长白和大白母猪繁殖性能的影响

为了研究胎次对杜洛克、长白和大白母猪繁殖性能的影响,根据江苏省某国家级生猪核心育种场2009-2011年出生的繁殖母猪资料,分别选取128头杜洛克、681头长白和610头大白母猪共7280窝生产数据,统计分析不同胎次母猪的总产仔数、产活仔数、断奶仔猪数、初生窝重及校正21日龄窝重。此外,依据胎次将母猪分为3个繁殖阶段（1～2胎、3～6胎及7～8胎）来探究品种差异对母猪繁殖性能的影响。结果表明：胎次对母猪繁殖性能有显著影响（P<0.05）,母猪1～4胎的总产仔数、产活仔数、断奶仔猪数及初生窝重随胎次呈增加趋势,第4胎达到高峰,且显著高于其他胎次（P<0.05）;3～6胎繁殖性能较好,7胎之后出现迅速下降趋势;除在第4胎略有下降外,其他胎次的校正21日龄窝重随胎次递增。品种对母猪繁殖性能的影响显著（P<0.05）,长白和大白母猪的繁殖性能均极显著高于杜洛克母猪（P<0.01）;长白母猪的产活仔数和校正21日龄窝重显著高于大白母猪（P<0.05）,2个品种其他繁殖性能无显著差异（P＞0.05）。综上所述,杜洛克、长白和大白母猪的最佳繁殖胎次为3～6胎,长白猪的繁殖性能总体上优于大白猪,就本试验所在的育种场而言,长白猪可能更适合作为二元母猪生产中的母本。     

Impact of diet deprivation and subsequent over-allowance during prepuberty. Part 2. Effects on mammary gland development and lactation performance of sows

The impact of diet deprivation and subsequent over-allowance in prepubertal gilts on their mammary development and mammary gene expression at the end of gestation and their lactation performance over 2 parities was determined. Seventy-seven gilts were reared under a conventional (control, CTL; n = 41) or an experimental (treatment, TRT; n = 36) dietary regimen. The experimental regimen provided 70 (restriction diet, RES) and 115% (over-allowance diet, OVER) of the protein and DE contents provided by the CTL diet. Experimental diets were fed ad libitum starting at 27.7 ± 3.4 kg of BW as follows: 3 wk RES, 3 wk OVER, 4 wk RES, and 4 wk OVER. All gilts were bred, and 34 were slaughtered on d 110 of gestation (18 CTL and 16 TRT) to collect mammary tissue for compositional analyses and gene expression measurements. Remaining gilts (23 CTL and 20 TRT) were maintained for 2 parities, and litter performance data were obtained. Blood samples for hormonal and metabolite assays were obtained on d 110 of gestation from all sows slaughtered at that time and from 14 sows per treatment on d 2 and 17 of lactation in the first parity. Milk samples were obtained from these same sows on d 17 of lactation in both parities. There was a tendency for mammary parenchymal tissue to contain less protein in TRT than CTL sows (P < 0.10), and relative mRNA abundance of the signal transducer and activator of transduction 5B gene was increased in parenchyma from TRT sows (P < 0.05). Circulating prolactin (P < 0.05) and milk lactose concentrations (P < 0.01) were less, whereas milk protein content was greater (P < 0.05) in TRT sows than CTL sows on d 17 of lactation. Nevertheless, growth rate of suckling piglets over the first 2 parities was unaffected by treatment. In conclusion, the use of a diet deprivation and over-allowance regimen in the growing-finishing period did not have beneficial effects on mammary gene expression or on sow and piglet performance.     

Effects of genetic line and supplemental dietary fat on lactation performance of Duroc and Landrace sows.

A total of 124 Duroc and 99 Landrace primiparous and multiparous sows were assigned, within breed and contemporary group, to control (N) or 10% added fat (F) diets on d 105 of gestation based on parity and genetic line (control or selected for improved sow productivity), to determine the effects of genetic line and fat addition to the lactation diet on sow and litter performance. Weekly feed intake was not affected (P greater than .10) by genetic line for Duroc and Landrace sows but feed intake was reduced (P = .08) during wk 1 to 4 for Duroc sows and during wk 1 and 4 for Landrace sows (P less than .05) when they were fed diet F compared with diet N. Select (S)-line Duroc and Landrace sows lost more weight during lactation (P less than .01) than did control (C)-line sows. Select-line Landrace sows lost more backfat during lactation (P less than .05) than did C-line sows. Landrace sows lost less weight during lactation (P less than .05) when fed diet F than when fed diet N. The total number of pigs born, born alive, and alive at 21 d and at weaning were higher (P less than .01) for S-line Duroc sows, and litter size at 21 d and at weaning was higher (P less than .01) for S-line Landrace sows than for C-line litters within each breed. Pig survival from birth to weaning was increased (P = .07) for Duroc sows fed diet F but not for Landrace sows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Quantitative influence of lysine and energy intake on yield of milk components in the primiparous sow.

A regression approach was used to assess quantitatively the influence of lysine and ME intake during lactation on yield of milk components and to determine whether this influence was mediated through precursor metabolite concentrations in the blood. The influence of lysine and energy intake on sow weight and backfat loss also was analyzed by linear regression. Twenty-three primiparous Landrace x Yorkshire sows were fed one of nine corn-soybean meal diets to achieve a matrix of lysine (15, 30, or 45 g/d) and ME (6.5, 11.5, or 16.5 Mcal/d) intakes. Sow BW and backfat losses were found to be predominantly controlled by ME intake (P less than .02), with no response to lysine intake (P greater than .92). Lysine and ME intake explained a smaller portion of the variability in milk component yield on d 8 (R2 less than .34) than on d 22 (R2 = .64 to .78), evidence that dietary effects of milk production increased as lactation progressed. Lysine and ME intake had an interactive influence (P less than .05) on yield of all milk components except lactose, demonstrating that the amount of lysine required to maximize milk production increased as ME intake increased. Strong relationships between diet and most blood precursor metabolite concentrations (R2 = .5 to .7) were detected on d 22. No obvious relationships between precursor metabolite concentrations and milk component yield (R2 = .05 to .2) were observed. These results describe quantitatively the prominent interactive effects of lysine and ME intake on yield of milk components and demonstrate that these effects are not directly associated with changes in precursor pool concentrations.     

Genetic correlation between leg conformation in young pigs,sow reproduction and longevity in Danish pig populations

Abstract

Selection for sow longevity using information from traits, which are expressed in early life and genetically highly related to longevity, is expected to be more effective than direct selection as it can overcome the disadvantage of late recording of true longevity. Our aim was to investigate the correlation between leg conformation recorded on young pigs, litter size at first parity and longevity of Danish Landrace and Yorkshire sows. Information on conformation from 116,733 Landrace and 89,963 Yorkshire pigs and information on reproduction and longevity from 27,070 Landrace and 11,895 Yorkshire sows were analyzed. All considered traits were low to moderately heritable, ranging from 0.02 to 0.41. In general, both conformation and reproduction traits were favorably genetically correlated with longevity (0.07–0.39 and 0.00–0.58, respectively). These estimates suggest a potential of improving sow longevity by selection on conformation recorded at young age and litter size at first parity.     

Milk Production in Sows after Spontaneous Delivery and after Delivery Induced by PGF2α Analogs

In this study the amount of milk produced during the first week of lactation was compared in sows with induced parturition and sows which delivered spontaneously (with special attention to sows showing MMA symptoms). Fifteen sows (L X LW) were used from a pig farm in which MMA was seen in 20 to 25% of all farrowings. The animals were divided into three groups of 5 each. Group A and B were treated with two different PGF ₂ α analogs (2 mg of alfaprostol or 0.45 mg of tiaprost) on 111 day of pregnancy, and group C (control) with 2 ml of saline solution. Treatment with PGF analogs induced parturitions 24 to 30 h later, controls delivered spontaneously on day 114. Litters were equalized to nine piglets per sow. The milk yield of each sow was calculate using the method of weighing piglets before and after each suckling. Piglets were allowed to suckle 12 times in the first 24 h after parturition, then 8 or 9 times in the next 24 h and from 48 h onwards 8 times during 24 h, until the end of the 7 day observation period. During the first day after parturition the control group appeared to produce slightly more milk than groups A and B whereas from 24 to 48 h, milk yields decreased in all animals. From 48 onwards milk production increased in all groups. Between 72–96 h, two sows of the control group showed symptoms of MMA and their piglets developed diarrhea. Microbiological analysis confirmed the presence of haemolytic Streptococci. The lactation curves of treated and untreated sows with no signs of MMA were very similar; the pattern was more erratic in sows with MMA. The total milk yields during the first week of lactation did not differ between groups; there were no significative difference in the weight gain of the piglets in groups A, B and C. The difference recorded in milk yield and release patterns between sows with or without MMA opens new aspects with regard to the aetiology of a syndrome that not only involves the sows health, but produces intestinals disease in their piglets.