环境丰容和哺乳母猪舍内散养对仔猪断奶前后生产性能的影响

<正>我们研究了哺乳期舍饲散养母猪以及断奶前后猪栏丰容对刚断奶仔猪生产性能的影响。断奶前,将限位饲养或散养母猪(n=32)所产仔猪(n=320)饲养在丰容(稻草、木屑、泥炭和枝条)或者贫瘠的圈舍     

Comparative effects of sodium butyrate and flavors on feed intake of lactating sows and growth performance of piglets

We examined the effects of sodium butyrate and flavors on feed intake of lactating sows and growth performance of piglets. A total of 52 primiparous sows (Large White) were randomly divided into four treatments (n = 13) and received 6 g/kg sodium butyrate (SB), fruit‐milk (FM) flavor and fruit‐milk‐anise (FMA) flavor with pair feeding to the mothers receiving the control diet. The feeding trial lasted for 29 days, including 21 days of nursing and 8 days of post‐weaning period, respectively. The nursing and weaning piglets received creep diets with the same flavor or SB supplement as their mother. The results showed that FMA flavor increased average daily feed intake (ADFI) of lactating sows (P < 0.01), as well as improved litter weight gain (P = 0.05) and ADFI (P < 0.01) of nursing pigs among treatments. Indeed, greater ADFI and average daily gain of weaning piglets for the initial 8 days after weaning was observed in the FMA group compared with those in the control group (P < 0.01). These findings indicated that adding FMA flavor was superior to SB for increasing feed intake of lactating sows and improving growth performance of piglets.     

Protein (lysine) restriction in primiparous lactating sows: effects on metabolic state,somatotropic axis,and reproductive performance after weaning

Low protein intake during lactation has been demonstrated to increase the loss of body protein and to reduce the reproductive performance of female pigs. The objectives of the current experiment were 1) to determine whether protein (lysine) restriction alters levels of somatotropic hormones, insulin, follicle-stimulating hormone, and leptin around weaning, and 2) to evaluate the relationships between these eventual alterations and postweaning reproductive performance. One day after farrowing, crossbred primiparous sows were randomly allocated to one of two diets containing 20% crude protein and 1.08% lysine (C, n = 12) or 10% crude protein and 0.50% lysine (L, n = 14) during a 28-d lactation. Diets provided similar amounts of metabolizable energy (3.1 Mcal/kg). Feed allowance was restricted to 4.2 kg/d throughout lactation, and litter size was standardized to 10 per sow within 5 d after farrowing. Catheters were fitted in the jugular vein of 21 sows around d 22 of lactation. Serial blood samples were collected 1 d before (day W - 1) and 1 d after (day W + 1) weaning, and single blood samples were collected daily from weaning until d 6 postweaning (day W + 6). Sows were monitored for estrus and inseminated. They were slaughtered at d 30 of gestation. During lactation, litter weight gain was similar among treatment groups. Reduced protein intake increased (P < 0.001) sow weight loss (-30 vs -19 kg) and estimated protein mobilization throughout lactation (-4.1 vs -2.0 kg). On day W - 1, L sows had higher (P < 0.02) plasma glutamine and alanine concentrations, but lower (P < 0.05) plasma tryptophan and urea than C sows. Mean and basal plasma GH were higher (P < 0.001), whereas plasma IGF-I and mean insulin were lower in L than in C sows on day W - 1. Preprandial leptin did not differ between treatments on day W - 1, but was higher (P < 0.01) in L sows than in C sows on day W + 1. Mean FSH concentrations were similar in both treatments on day W - 1 (1.3 ng/mL), but L sows had greater (P < 0.001) mean FSH on day W + 1 than C sows (1.6 vs 1.2 ng/mL). The weaning-to-estrus interval (5 +/- 1 d) was similar in both groups. Ovulation rate was lower in L than in C sows (20.0 +/- 1 vs 23.4 +/- 1, P < 0.05). No obvious relationships between reproductive traits and metabolic hormone data were observed. In conclusion, these results provide evidence that protein (lysine) restriction throughout lactation alters circulating concentrations of somatotropic hormones and insulin at the end of lactation and has a negative impact on postweaning ovulation rate.     

Behavior and performance of lactating sows and piglets reared indoors or outdoors.

Two hundred eighty-seven lactating Newsham sows and their litters were used to determine the effects of intensive indoor (n = 147) and intensive outdoor (n = 140) production systems on sow and litter productivity and behavior. All sows were of contemporary age and fed a completely balanced sorghum-based diet. Behavior data were collected by live observation on 40 sows and litters (20 indoor and 20 outdoor) using a 5-min scan sample over a 4-h period in the afternoon (1400 to 1800). The durations of lying (90.0 vs 72.1 +/- 2.76% of time observed) and drinking (4.42 vs 1.41 +/- 0.6% of time observed) were higher (P < 0.01) among indoor than among outdoor lactating sows. Nursing interval and feeding and sitting behaviors were not different (P > 0.05) between production systems. Piglets spent more (P < 0.05) time walking (10.1 vs 5.2 +/- 1.72% of time observed) and engaged in play activity (5.0 vs 1.7 +/- 1.26% of time observed) when housed outdoors than indoors. Outdoor piglets had more (P < 0.05) nursing behaviors directed toward the sow (27.5 vs 20.3 +/- 2.02% of time observed) but time spent in contact with the sow did not differ between environments (38.8 vs 39.2 +/- 2.78% of time observed). Treatments did not influence (P > 0.05) any of the sow or piglet production parameters. In conclusion, outdoor-kept Newsham sows and their piglets showed a richer behavioral repertoire, but the diverse environments did not influence production parameters.     

音乐刺激对断奶仔猪行为和生长的影响

本试验采用随机分组设计,选用45日龄断奶的长白仔猪32头,随机分成对照组和试验组,试验组每天接受3小时的音乐刺激,进行对比试验.经25天试验表明,试验组在4天后就能适应音乐刺激,平均卧息时间较对照组提高7.74%,活动时间下降5.26%,断奶应激行为也明显少于对照组;同时,平均日增重提高10.07%(P>0.05),饲料利用率提高5.76%.     

音乐刺激对断奶仔猪行为和生长的影响

本试验采用随机分组设计，选用４５日龄断奶的长白仔猪３２头。随机分成对照组和试验组，试验组每天接受３小时的音乐刺激，进行对比试验。经２５天试验表明，试验组在４天后就能适应音乐刺激，平均卧息时间较对照提高７．７４％，活动时间下降５．２６％，断奶应激行为明显省于对照组；同时，平均日增重提高１０．０７％（Ｐ〉０．０５），饲料利用率提高５．７６％。     

Post-farrowing stress management in sows by administration of azaperone: effects on piglets performance

This study examined the impact of a single dose of azaperone administered to sows at the end of farrowing on piglet weight gain and mortality during the lactation period. Two hundred fifty-two sows (JSR hybrid) housed in a conventional farrowing crate system were assigned to either a treatment or a control group. The parities of the sow were between 1 and 6. The differences between live birth weight and weight at weaning were recorded for 3,093 individual piglets. Serum concentrations of IgG of 485 piglets also were recorded during tail docking. Median and interquartile range (IQR) were 5.1 (2.9 to 9.5) mg·mL(-1) in the control group and 5.6 (3.1 to 12.1) mg·mL(-1) in the azaperone group (P > 0.05). Litter size was 13.0 (11 to 15) total born piglets and birth weight was 1.28 (1.05 to 1.52) kg. Weaning weight for the control group was 5.64 (4.73 to 6.54) kg compared with 5.78 (4.79 to 6.71) kg for the azaperone treated group (P = 0.005). Daily BW gain differed significantly (P = 0.001) between the 2 groups, 205 g for the controls, compared with 214 g for the azaperone group. There were no significant differences between piglet mortality rates (17% and 20%). Azaperone applications to sows tended to have a positive effect on productivity. Effect was greatest in the primiparous sows and declined with increasing parity. This may have been due to both physiological and behavioral differences between the sows as they experienced increasing numbers of gestations, farrowings, and lactation periods.     

芪归催乳散对母猪泌乳性能及仔猪免疫和抗氧化功能的影响

旨在研究饲料中添加中药"芪归催乳散"超微粉对母猪泌乳性能及仔猪免疫和抗氧化功能的影响。选取24头胎次、分娩期相近的待产长白二元母猪,随机平均分为3组,每组8个重复。自产前7d开始,对照组母猪饲喂基础日粮,试验1,2组的母猪分别在基础日粮中添加1%和2%的芪归催乳散超微粉,直至断奶。仔猪分别于出生当日、20日龄及断奶时测体质量,计算泌乳量;并于断奶当日从每窝随机挑选2头仔猪采血,检测血清免疫和抗氧化指标。母猪则收集初乳,并于产后4,21d采血,用于检测初乳成分及泌乳相关激素水平。结果显示,在饲料中添加芪归催乳散超微粉能显著提高母猪泌乳量、初乳中蛋白含量以及初乳中催乳素(PRL)、生长激素(GH)和促甲状腺素(TSH)水平(P0.05),显著提高母猪血清中催乳素(PRL)和生长激素(GH)水平(P0.05);同时能显著提高仔猪血清免疫球蛋白(IgG,IgM,IgA)和补体C3的含量以及超氧化物歧化酶(SOD)活性(P0.05),降低丙二醛(MDA)含量(P0.05)。上述结果表明,芪归催乳散能显著提高母猪泌乳相关激素水平,促进泌乳;同时能提高哺乳仔猪免疫和抗氧化功能。     

Effects of repeated cross-fosterings on preweaning behavior and growth performance of piglets and on maternal behavior of sows

Extensive cross-fostering is widely used in early-weaning units in order to standardize and improve body weight at weaning. However, young suckling piglets develop teat fidelity and repeated cross-fosterings could go against this behavior. This experiment was therefore conducted to compare the behavior and growth of 13 control and 14 fostered litters. Once every 3 d (from d 1 to 16 of lactation), all piglets were weighed and three piglets were switched between two fostered litters. Their unfostered littermates were called residents. Behavior was recorded for 2 h after weighing and(or) adoption and during one nursing period 24 h later. Fights were more frequent (P < 0.05) in treated than in control litters during and between nursings at all ages of adoption except d 1. Most fights occurred between resident and fostered piglets (P < 0.001), except at d 1. Fights during nursing were still more frequent in treated than in control litters 24 h after adoption (P < 0.02), except at d 1 and 16. More piglets had skin lacerations in treated than in control litters except at d 1 (P < 0.05), and scratches were more frequent in fostered than in resident piglets at d 1 (P = 0.07), 7, 13, and 16 (P < 0.01). At all ages except d 1, failed nursings and snaps at piglets were more frequent in fostered than in control litters (P < 0.05), most snaps being directed at adopted piglets (P < 0.001). In fostered litters, sows spent 15 to 30% less time lying on their sides at d 4, 7, 13, and 16 (P < 0.05). Finally, adopted piglets were 13% lighter than controls at weaning (P < 0.001), whereas residents were heavier than adopted piglets (P < 0.05) but lighter than controls (P = 0.1). These data demonstrate that cross-fostering done repeatedly during lactation is stressful for piglets and sows and does not improve body weight at weaning.     

Fender design and insulation of farrowing huts: effects on performance of outdoor sows and piglets

Two studies assessed sow and litter performance when design features of farrowing huts varied. A fender is a structure that extends out the front of the hut to create a veranda that prevents young piglets from leaving. In Exp. 1, 206 lactating sows and their litters were used to assess litter performance and the time required to process litters for two fender designs (short wooden [WS] vs. tall metal with a board front [MT-b]) and insulation status (insulated [IN] vs. uninsulated [UN]) farrowing huts. A significant fender x insulation interaction was observed for total litter weaning weight. Lighter litters weaned (P = 0.013) from WS fenders with UN huts compared with the other treatments. Fender design did not (P > 0.05) influence the time required to process a litter with one stockperson. Less total time (P = 0.001) was required to process a litter when two people were present (10.60 +/- 0.74 min) compared with one stockperson (14.52 +/- 0.74 min). There were no (P > 0.05) differences between IN and UN huts for temperature and relative humidity measurements. In Exp. 2, 331 lactating sows and their litters were used to determine sow and litter performance when using one of two fender front designs (boards [MT-b] vs. roller [MT-r]). The front design of the fender did not influence (P > 0.05) most litter performance measures. We conclude that fender design, fender fronts, and insulation effects did not have large influences on sow and litter performance in a West Texas environment.     

Intermittent suckling: effects on piglet and sow performance before and after weaning

An experiment was conducted to study effects of intermittent suckling on creep feed intake and weight gain of litters. Loss of weight and backfat during lactation, as well as reproductive performance, were also measured. Batches of multiparous sows (Parity 1 to 12, 4.1 on average) were either suckled intermittently (IS, eight batches; n = 50) or continuously (control, eight batches; n = 62). Litters were weaned at 27 +/- 2 d of age, on average. Litter size (11.1 +/- 0.2 piglets, on average) was standardized within a batch within 3 d of birth. All litters had free access to creep feed and water from 1 wk of age onward. In the IS group, litters were separated from the sow for a period of 12 h/d (0930 to 2130), starting 11 d before weaning. Rectal ultrasonography was applied at d 3 after weaning to check the ovaries for follicle development or presence of corpora lutea. Creep feed intake by the litters during lactation was higher in IS litters than in control litters (686 +/- 57 vs. 314 +/- 42 g/piglet, P < 0.01). The distribution of creep feed intake shifted from a skewed one, with a majority of litters consuming less than 250 g/piglet in control litters, to a normal distribution, with an average creep feed intake of 500 to 750 g/piglet in IS litters. During the 7 d after weaning, creep feed intake in IS litters was also higher (281 +/- 15 vs. 204 +/- 9 g-piglet(-1) x d(-1), P < 0.01). The ADG of piglets during lactation was negatively affected by IS, resulting in lower weight at weaning (7,229 +/- 140 vs. 7,893 +/- 145 g/piglet, P < 0.05). During the 7 d after weaning, however, ADG was higher in IS litters (255 +/- 10 vs. 177 +/- 8 g-piglet-1 x d(-1), P < 0.01), and 7 d after weaning, the weights of the litters were similar (9,011 +/- 167 vs. 9,132 +/- 164 g/ piglet, P = 0.81). The IS litters that consumed little or no feed during lactation had an ADG after lactation that was higher than in control litters, with comparable creep feed intake during lactation: 204 vs. 136 g/d. Body weight loss by the sows during lactation was lower in IS sows (-10 +/- 2 vs. -16 +/- 1 kg, P < 0.05). A higher percentage of IS sows ovulated during lactation (22 vs. 3%, P < 0.01), and weaning-to-ovulation interval (excluding sows with lactational ovulation) was shorter in IS sows (4.7 +/- 0.2 vs. 5.3 +/- 0.2 d, P < 0.05). We conclude that IS increased creep feed intake during lactation, and that IS increased ADG after weaning, despite lower weaning weights. Ovulation during lactation was induced in 22% of the IS sows.     

Effect of pre- and postweaning zeranol implant on steer calf performance

One hundred ninety-five steer calves were assigned to five zeranol implant treatment (trial 1). Treatments were no implants (0000), two implants during the finishing period (00XX), three implants during growing and finishing periods (0XXX), one implant at 1 to 2 mo of age during the suckling period and two during the finishing period (X0XX) or four implants (XXXX). The growing period implant was administered at weaning. Weaning weights (211 vs 208 kg) of implanted and nonimplanted suckling calves were not different (P greater than .05). Calves implanted at weaning, before shipment to the feedlot, had greater (P less than .05) weight loss in shipment than nonimplanted calves. In the feedlot, finishing-period daily gains of steers implanted in the growing and finishing period (0XXX) were greater (P less than .05) than gains of steers that had received a suckling period implant (X0XX and XXXX). Nonimplanted steer gains were less (P less than .05) than gains of steers from the other four treatment groups. Postweaning daily gains and final weights were 1.18 and 517 (0000), 1.26 and 533 (00XX), 1.32 and 551 (0XXX), 1.26 and 540 (X0XX) and 1.25 and 533 kg (XXXX), respectively. Gains and final weights of nonimplanted steers were less (P less than .05) than gains of steers implanted only in the feedlot growing and finishing periods (0XXX). In a second trial, 82 steers were assigned either to a 0XXX or XXXX implant scheme. Weaning weights were 11 kg greater (P less than .05) for the implanted steers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary arginine supplementation during gestation and lactation on the performance of lactating primiparous sows and nursing piglets

A 2 x 2 factorial arrangement of treatments in a randomized block design was used to determine the effects of dietary Arg supplementation during gestation and lactation on the lactation performance of 38 first-parity sows. At 30 d of gestation, pregnant gilts were allotted based on BW to 1 of 2 diets supplemented with 1% L-Arg.HCl or 1.7% L-Ala (isonitrogenous control). After farrowing, sows were further allotted based on BW within previous gestation treatment groups to 1 of 2 lactation diets supplemented with 1% L-Arg.HCl or 1.7% L-Ala (isonitrogenous control). All gestation diets contained 3.1 Mcal/kg and 12.2% CP (as is) and were fed 2 kg/d in 2 equally sized meals, whereas all lactation diets contained 3.2 Mcal/kg and 18.6% CP (as is) and were fed ad libitum. Litter size was standardized to 10 piglets by cross-fostering within 24 h postfarrowing. On a weekly basis, BW and backfat (BF) thickness of sows, as well as piglet BW were measured, and blood and milk samples were obtained from the sows. Number of days from weaning to estrus and ADFI were also recorded. There were no differences in BW, BF thickness, ADFI, or days until return to estrus among treatment groups. There was no effect of the gestation diet or a gestation x lactation diet interaction on any parameter measured. On d 7 of lactation, plasma concentrations of Arg and insulin in sows, as well as concentrations of most AA in milk, were greater (P < 0.05) in response to Arg supplementation during lactation compared with the control. Weight gain of piglets from sows fed the Arg-supplemented diet during lactation was greater between d 0 and 7 (P < 0.01) and between d 0 and 21 (P < 0.05) of lactation compared with piglets from sows fed the control diet. Collectively, results from this study indicate the potential beneficial effects of dietary Arg supplementation in improving the lactation performance of first-parity sows.     

仔猪出生后的生理变量对其存活率及断奶前生长性能的影响

文章旨在评估一些出生后测量的生理变量对仔猪在出生第一周的存活率和断奶前生长性能的影响。试验选择612头来自3~5胎龄母猪所产的仔猪,监测氧饱和度、心率、血糖浓度、出生后0和24h直肠温度,同时记录遗传谱系、是否助产、出生顺序、性别、肤色、脐带的完整性以及出生后到第一次站立的时间。分别在仔猪出生时、7、14和21d对仔猪称重,评估仔猪产后发育情况。出生后第3、7和21天的累积死亡率分别为3.3%、5.4%和8.7%。出生时直肠体温对仔猪的生存和生长性能无影响(P>0.05)。与正常肤色仔猪和站立时间在1min前的仔猪相比,青紫肤色的仔猪和站立时间在5min以上的仔猪死亡率更高(P<0.05)。脐带断裂的仔猪在出生后3d内死亡率较高(P<0.05)。仔猪在出生后3或7d较高的死亡率发生在出生顺序>9,出生体重<1275g,血糖浓度24~30mg/dL和45~162mg/dL以及出生后24h直肠温度<38.1℃。体重<1545g、出生后24h直肠温度<38.6℃的仔猪在断奶时体重较轻的概率较高(P<0.05)。在研究因素中,皮肤发紫、站立迟缓、脐带断裂、出生顺序高、体重低、出生后24h直肠温度低、血糖浓度低均是导致仔猪出生后第一周存活力较低的因素。     

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.     

熟化软颗粒教槽料对断奶仔猪生长性能及腹泻率的影响

为研究熟化软颗粒教槽料对仔猪断奶前后生长性能及腹泻率的影响,试验选用8窝(共计84头)15日龄仔猪,随机分为对照组和试验组,分别饲喂同配方的粉状教槽料和软颗粒教槽料,每个组4个重复,每个重复1窝猪;试验分为两个阶段,分别为断奶前10d和断奶后5d,即15~25日龄和26~30日龄,仔猪在25日龄断奶。结果表明:在15~25日龄阶段,试验组仔猪平均日增重(ADG)较对照组无明显差异,平均日采食量(ADFI)增加了40.90%;在26~30日龄阶段,试验组ADG较对照组增加了12.21%,ADFI增加了34.41%;整个试验期,试验组ADFI较对照组增加了35.12%,ADG无明显差异,试验组的腹泻率也低于对照组;在仔猪断奶前后的3d,试验组的ADG和ADFI均高于对照组。综上,软颗粒教槽料在仔猪断奶后前期可有效地提高其采食量和日增重。     

酸化剂对断奶仔猪生长性能及腹泻的影响

试验选用 72头 2 8日龄断奶的三元杂交 (杜×长×大 )仔猪 ,平均体质量 (6 .8± 0 .3)kg。研究玉米 -豆粕型基础日粮中添加不同水平酸化剂对断奶仔猪生长性能及腹泻的影响。采用完全随机设计 ,分 3个处理 ,每个处理 6个重复 (圈 ) ,每个重复 4头猪 ,公母各半混合饲养。饲养期 2 8d ,自由采食及饮水。处理 1为无酸化剂对照组、处理 2为添加 0 .3%酸化剂组、处理 3为添加 0 .6 %酸化剂组。试验结果表明 :酸化剂降低断奶仔猪胃内容物的pH ,降低病原微生物感染是快速的 ,对仔猪的生理效应需要一个渐进的过程 ,在试验的 4周才显著提高断奶仔猪日增重 (P <0 .0 5 )、增加采食量 (P <0 .0 1)、改善饲料转化效率 (P <0 .0 5 )。     

Relation of growth hormone response to growth hormone-releasing hormone before weaning and postweaning growth performance in beef calves

Previously, GH response to GHRH challenge at weaning has been shown to be indicative of ADG during a standard postweaning growth performance test in Angus cattle. In this study, we tested the hypothesis that GH response to GHRH before weaning would predict postweaning ADG. Bulls with the highest and lowest GH responses to GHRH over a 3-yr period, relative to their contemporaries, were used as sires, to allow for examination of the persistence of GH response to GHRH through selection. The selected calves in this study were sired by one of four Angus bulls chosen based on their GH response to GHRH (high response, n = 2; low response, n = 2). Forty-nine Angus calves (bulls, n = 24; heifers, n = 25) were challenged with GHRH at approximately 60, 105, and 150 d of age and at weaning (219 d; SD = 25). Blood samples were taken immediately prior to and 10 min following an i.v. clearance dose of 4.5 microg of GHRH/100 kg BW and, 2 h later, immediately prior to and 10 min following a challenge dose of either 1.5 or 4.5 microg of GHRH/100 kg BW. Two hours later, the procedure was repeated, with each calf receiving the other challenge dose. Body weight was measured every 28 d and ADG was calculated over a 140-d growth performance test (heifers and bulls maintained separately). Data were log-transformed for statistical analyses. In the selected bulls and heifers, response of GH to 1.5 microg of GHRH/100 kg BW at 60 and 105 d of age was positively related (P < 0.05) to postweaning ADG. Response to 4.5 microg of GHRH/100 kg BW at 105 d of age and at weaning was positively related (P < 0.01) to postweaning ADG. Inclusion of sire in the analysis improved the relationship between GH response and ADG for calves of sires with high GH responses from R2 = 0.18 (P = 0.01) to R2 = 0.33 (P = 0.02). When the GH response to GHRH of the unselected calves at weaning was added to the data from the selected animals and analyzed, the GH response of the bulls was related to postweaning ADG (R2 = 0.09; P = 0.04). In conclusion, GH response to GHRH as early as 60 d of age is indicative of postweaning ADG in beef cattle. In addition, the relationship between GH response to GHRH and postweaning ADG is improved with selection for greater GH response to GHRH.     

Effects of magnesium on the performance of sows and their piglets

The objective of this study was to evaluate the effects of supplemental magnesium(Mg) on the performance of gilts and parity 3 sows and their piglets.Fifty-six gilts(Trial 1) and 56 sows(Trial 2) were assigned to one of 4treatments according to their mating weight,respectively.The treatments comprised corn-soybean meal based gestation and lactation diets(0.21%magnesium) supplemented with 0,0.015,0.03,or 0.045%Mg from mating until weaning.The results showed that magnesium supplementation significantly(P 0.05) reduced the weaning to estrus interval in both gilts and sows.There were significant effects(P 0.05) of supplemental magnesium on the total number of piglets born,born alive and weaned in sows.In late gestation and lactation,the digestibility of crude fiber(quadratic effects,P 0.05),and crude protein(P 0.05),were significantly influenced by magnesium in gilts and sows,respectively.There were differences among the 4 groups in terms of the apparent digestibility of dry matter and crude fiber in sows(P 0.05) during both early and late gestation.The apparent digestibility of gross energy was increased for sows in late gestation(P 0.05),and lactation(quadratic effects,P 0.05).At farrowing and weaning,serum prolactin levels and alkaline phosphate activities linearly increased in sows as the Mg supplementation increased(P 0.05).Serum Mg of sows at farrowing and serum urea nitrogen of sows at weaning was significantly influenced by Mg supplementation(P 0.05).The Mg concentration in sow colostrum and the serum of their piglets were increased by supplemental magnesium(P 0.05).In addition,growth hormone levels were linearly elevated(P 0.05) in the serum of piglets suckling sows.Our data demonstrated that supplemental magnesium has the potential to improve the reproduction performance of sows,and the suitable supplemental dose ranged from 0.015%to 0.03%.