Evaluation of well-being, productivity, and longevity of pregnant sows housed in groups in pens with an electronic sow feeder or separately in gestation stalls

OBJECTIVE: To compare well-being, performance, and longevity of gestating sows housed in stalls or in pens with an electronic sow feeder (ESF). ANIMALS: 382 pregnant sows of parities 1 through 6. PROCEDURE: Sows were housed in separate stalls (n = 176) or group pens (206) with an ESF. Well-being of sows was assessed at various time points in terms of injuries, salivary cortisol concentration, and behavior in a novel arena or to a novel object. Farrowing performance and longevity of sows were also assessed. RESULTS: Total injury scores (TIS) of sows in pens were significantly higher at initial introduction and mixing. In stall-housed sows, TIS was significantly higher during late gestation. The TIS and cortisol concentration were significantly lower in stall-housed sows, compared with values for sows in pens. As parity increased, the likelihood of higher median TIS decreased significantly in pen-housed sows and increased significantly in stall-housed sows. The TIS of sows in pens was negatively correlated with body weight and backfat thickness, whereas these correlations were positive in stall-housed sows. Farrowing performance and results for novel arena or objects did not differ. Proportion of sows removed was significantly higher for pens than for stalls; lameness was the major reason for removal for both systems. CONCLUSIONS AND CLINICAL RELEVANCE: Stalls impose space restrictions for larger sows, resulting in injuries during late gestation. Interventions are needed to minimize aggression during initial introduction and mixing and at the ESF in pens to reduce severe injuries or lameness of gestating sows.     

Comparison of injuries in sows housed in gestation stalls versus group pens with electronic sow feeders

OBJECTIVE: To compare the location and severity of injuries in pregnant sows housed in individual gestation stalls with that in pregnant sows housed in dynamic groups in pens with electronic sow feeders. DESIGN: Prospective study. ANIMALS: 100 pregnant sows of parity 1 to 3 and various body weights. PROCEDURE: Fifty sows each were randomly allotted to gestation stalls or group pens with electronic sow feeders. Injuries were scored on the basis of location, number, and depth of wounds. Injury scores for sows in both housing systems were compared during a period of 90 days. The influence of factors such as duration of stay in the housing system, parity, and body weight on sow injuries was also examined. RESULTS: Injury scores were higher in group pens with electronic sow feeders. As body weight increased, injury scores decreased for sows housed in group pens with electronic sow feeders and increased for sows housed in gestation stalls. There was a significant negative association between second parity and total injury scores. CONCLUSIONS AND CLINICAL RELEVANCE: Modifications in housing system design and management procedures are needed to reduce injuries in pregnant sows.     

Performance of gestating sows in bedded hoop barns and confinement stalls

The effects of gestation housing systems on sow and litter performance were evaluated for 2.5 yr in southwest Iowa. Gestation housing system treatments were as follows: 1) individual gestation stalls in a mechanically ventilated confinement building with a partially slatted floor and a manure flush system and 2) group pens with individual feed stalls in deep-bedded, naturally ventilated hoop barns. In all, 957 litters from 353 sows were evaluated. Number of pigs born alive per litter differed for the 2 housing treatments (P = 0.002). Sows gestated in hoop barns gave birth to more live pigs per litter (10.0 +/- 0.2 pigs) than sows gestated in stalls (9.3 +/- 0.2 pigs). Preweaning mortality was not different for the 2 housing treatments (P = 0.70). Cross-fostering was done to equalize litter size within 24 h of birth, which resulted in an equal number of weaned pigs per sow (P = 0.50) regardless of gestation housing treatment. The weaning-to-breeding interval was different (P = 0.01), with sows kept in stalls (4.3 +/- 0.6 d) returning to estrus sooner than sows gestated in hoop barns (6.0 +/- 0.6 d). These results indicate that gestating sows can be housed as groups in deep-bedded hoop barns equipped with individual feeding stalls and will perform comparably to gestating sows housed in confinement systems with individual gestation stalls.     

Evaluation of drop versus trickle-feeding systems for crated or group-penned gestating sows

A total of 160 gilts were used to evaluate the effects of pen vs. crated housing systems and drop- vs. trickle-fed feeding systems on sow productivity, occurrence of lesions during farrowing and weaning, immune measures, and behavioral responses during 2 consecutive gestation periods. Of the 160 eligible gilts, 117 farrowed in parity 1, and of those, 72 farrowed in parity 2. The gilts were randomly assigned to represent 1 of 4 factorially arranged treatment groups: pen drop-fed, crate drop-fed, pen trickle-fed, or crate trickle-fed. Replicate blocks were used for each parity with 5 sows per block initially in each treatment. At weaning, sows housed in pens had greater (P < 0.05) backfat thickness than sows housed in crates. The piglet weaning weight was greater (P < 0.05) for sows fed with the single drop compared with the trickle-feeding system. Lesions scores and all other productivity measures did not differ among treatments. An interaction was observed for percentage of neutrophil phagocytosis (P < 0.05) between penning and feeding systems. In pens, drop-fed sows had greater phagocytosis than trickle-fed sows, but in crates, drop-fed sows had a tendency for lower phagocytosis than trickle-fed sows. All other immune measures were not different among treatments. The occurrence of oral-nasal-facial (ONF) behaviors (chewing, rooting, and rubbing) and active behaviors increased, and lying behavior decreased (P < 0.05), from 0800 to 1200 for all sows. During the 0800 to 1200 period, crate drop-fed sows displayed more (P < 0.05) ONF and active behaviors than did sows in the 3 other treatments. Sows housed in groups of 5 had a greater (P < 0.05) duration of standing in the 0400 to 0800 period compared with crated sows. Housing systems had complex effects on sow behavioral sequences, but penned sows had more sequences associated with stress than did crated sows. Also, crate drop-fed gilts and sows expressed more ONF behaviors than gilts and sows in other treatments. Generally, productivity, skin lesions, and immune measures were not different, but behaviors at certain times of day and behavioral sequences were different for sows in pens and crates with drop or trickle-feeding systems. None of the environments evaluated were associated with significant physiological stress responses among the sows. Thus, sows were able to adapt within each environment through behavioral mechanisms without the need to invoke major physiological adjustments.     

Effects of different gestation housing types on reproductive performance of sows

This study evaluated the effects of different gestation housing types on reproductive performance of sows. A total of 60 sows (218 ± 24 kg body weight) with mixed parity were used. During gestation, 28 sows were housed in groups with electronic sow feeders (space allowance = 1.26 m²/sow) and 32 sows were housed in individual stalls (space allowance = 1.20 m²/sow). Sows from both housing types were moved to farrowing crates on day 109 of gestation and stayed until weaning (18 days post‐farrowing). Typical corn‐soybean meal diets were provided to sows during gestation and lactation. Measurements were reproductive performance of sows at farrowing as well as performance of sows and their litter during lactation. Similar total numbers of piglets born at farrowing were observed for sows gestated in both housing types. However, group‐housed gestation sows had more mummies (0.321 vs. 0.064; P < 0.05) and stillbirths (0.893 vs. 0.469; P = 0.073) at farrowing than individual‐housed gestation sows. Consequently, individual‐housing type had higher percentage of piglets born alive (95.5 vs. 90.4%; P < 0.05) than the group‐housing type. Therefore, improved reproductive performance of sows from individual gestating housing was confirmed in this study.     

Space allowance for dry, pregnant sows in pens: body condition, skin lesions, and performance

Different floor space allowances for dry, pregnant sows in pens were evaluated to determine the impacts of space on sow performance, productivity, and body lesions during 2 consecutive farrowings. Treatment groups of 5 sows/pen were assigned to 1.4, 2.3, or 3.3 m(2) of floor space/sow or of 5 sows in individual stalls (1.34 m(2)). The experiment consisted of 6 replications (blocks 1 to 6), and within each block measurements were recorded for 2 consecutive pregnancies and farrowings. A total of 152 sows were measured at 1 farrowing, and 65 of those sows were measured at the successive farrowing (n = 217 records). Performance traits were BCS, BW, backfat (BF), days until rebred, and proportion culled. Litter traits were number of piglets born alive, male:female ratio, and proportions of stillborn, mummified, or dead piglets after birth. Litter performance measures were mean piglet BW and gain and litter BW. Lesion scores were assessed for several body regions. There were treatment and parity effects and interactions for several traits. An interaction of space treatment and parity occurred for sow mean BW, d-110 BW, BF, litter size, and litter and piglet BW and gain, with most effects in parity 2, 3, and 4 sows. Space affected sow mean (P < 0.001) and d-110 BW (P < 0.05) and mean BF and adjusted BF (P < 0.001); sows in pens at 相似文献   

Evaluation of the relationship between injuries and size of gestation stalls relative to size of sows

OBJECTIVE: To determine whether there is a relationship between sow injuries and size of gestation stalls relative to sow size. DESIGN: Prospective study. ANIMALS: 267 pregnant sows. PROCEDURE: Sows were randomly selected from 4 swine farms. Sow and stall measurements were obtained, and injuries were scored on the basis of location, number, and depth. Ratios of stall length to sow length and stall width to sow height were calculated. RESULTS: High injury scores were associated with low ratios of stall length to sow length and stall width to sow height. CONCLUSIONS AND CLINICAL RELEVANCE: A small increase in stall dimensions could reduce injuries and improve well-being of sows considerably.     

Factors influencing farmers' responses to welfare legislation: A case study of gestation sow housing in Flanders (Belgium)

In the light of the EU ban on individual confinement of gestating sows which will have to be fully implemented by 2013, a survey was conducted among a representative sample of Flemish pig producers. The questionnaire was sent by post to 250 farmers in 2003 and 352 farmers in 2005 of which 219 and 296, respectively, provided valid responses via telephone. The percentage of respondents housing (some of) their sows in group was 10.5% in 2003 and 16.2% in 2005. These farmers were more likely to have a successor than farmers housing their sows individually. The most common group housing systems were free access stalls (24%) followed by electronic feeding stations (21%), ad libitum feeding (20%), feeding stalls/troughs (18%), and drop/trickle feeding systems (13%). Interval (4%) and electronic feed dispensers (0%) were very rare in Flanders. The main criteria for having chosen a particular group housing system related to sow health and welfare, investment costs and amount of labour. The relative importance of economic reasons has increased over time. Users were generally rather satisfied with their group housing system. Farmers using group housing for all their sows were more satisfied than farmers using both group and individual housing. Users of ad libitum feeding systems (and feeding stalls/troughs) were more satisfied than users of electronic feeding stations. A minority of respondents was planning to change to group housing within two years time (4.1% in 2003 and 7.4% in 2005). These tended to be young farmers with a large sow herd and 58% reported to opt for free access stalls. The main reason why the remaining respondents were not planning to change to group housing yet is that they will stop farming activities before 2013. This reason was particularly important for older small-scale farmers without a successor. In contrast, the lack of financial resources and security was particularly important for young farmers of a large sow herd with a likely successor. An increasing group of farmers (often without a successor) reported to delay changing to group housing because they consider individual housing more profitable. These results show that, in Flanders, the conversion to group housing is taking place slowly, that the reasons for not converting yet vary according to the farmers' age, the likelihood of a successor and herd size, and that there are differences between operational group housing systems concerning herd size, age of the system, sow management and user satisfaction.     

不同饲养模式对妊娠母猪行为、唾液皮质醇和淀粉酶水平的影响

本试验利用母猪行为以及唾液皮质醇和淀粉酶含量探索空间限制对母猪生理心理状态造成的影响。试验选择大白妊娠母猪64头,随机平均分成2组,分别采用限位栏(180 cm×60 cm×110 cm)和群养模式(568 cm×448 cm×50 cm)饲养,群养模式下每圈8头母猪,共4圈。于试验1、3、5、6、8、10、11、13、15周第1、2天分别采用10 min间隔扫描取样法记录母猪行为和采集试验母猪唾液样本,检测唾液皮质醇水平和唾液淀粉酶含量。结果表明:限位栏母猪表现无食咀嚼、啃栏、啃槽行为的次数显著高于群养母猪。限位栏母猪的唾液皮质醇和淀粉酶表现出相反的分泌趋势,无食咀嚼与唾液淀粉酶含量之间存在显著的正相关关系(r=0.336,P=0.048)。群养模式下试验母猪的唾液皮质醇水平、淀粉酶含量与无食咀嚼行为之间没有显著性相关的关系。     

Behavioral and stress responses to feeding time in pregnant sows under limit-fed regime

We investigated the effect of feeding time on behavior and stress responses in pregnant sows under isocaloric conditions. Twenty-four sows were balanced for parity and randomly assigned to 1 of 3 feeding times. Corn–soybean meal-based diet was fed once at: 0730 (Control, T1), 1130 (T2), and 1530 hours (T3). On average, sows received 7,062 kcal ME/d from 2.20 kg of diet formulated to contain SID Lys/ME of 1.71 g/Mcal. The study was conducted for 28 d (21 d acclimation to the feeding regime and 7 d data collection). Saliva samples were collected every 2 hr for 12 hr in stalls on day 52 of pregnancy. Behavior data were collected 24 hr for 7 d from day 53 of gestating by affixing a remote insights ear tag to each sow. Each sow had 120,960 data points categorized into: “Active,” “Feed,” or “Dormant”. Due to housing constraint, all sows were housed in individual stalls in the same barn presenting a potential limitation of the study. Data were analyzed using PROC MIXED and GLIMMIX procedures of SAS 9.4 for cortisol and behavior data, respectively. Sow was the experimental unit. The area under the curve (AUC) is quantitative evaluation of response as threshold varies over all possible values. A 12-hr cortisol total AUC for sows fed once daily at 1130 hours was reduced relative to sow group fed at 1530 hours (P = 0.046) but similar compared with the control sows (P = 0. 323). The control sows (0730 hours) had reduced total (P < 0.001) and feeding (P = 0.001) activity AUCs relative to sows on 1130 hours but did not differ compared with sows on 1530 hours feeding schedules (P > 0.100). Sows on 1130 hours feeding schedule had greater feed anticipatory activity, 24-hr total activity count, total (P < 0.001) and feeding (P < 0.001) activity AUC compared with sows fed daily at 1530 hours. In conclusion, feeding pregnant sows earlier in the morning (0730 hours) appears to minimize sows’ behavior but similar cortisol response. Sows on 1130 hours feeding schedule had greater activities but reduced cortisol concentration, suggesting that elevated sow activity might not necessarily indicate activation of hypothalamic–pituitary–adrenal axis.     

Survey among Belgian pig producers about the introduction of group housing systems for gestating sows

There is a global move from individual to group housing of gestating sows. In the European Union, individual gestating stalls will be banned by 2013. Just like in other industrialized regions, these stalls have been the standard housing system for intensively kept sows from the 1960s onward in the Flemish region of Belgium. Because the socioeconomic consequences for the pig industry may be far-reaching and because farmer attitude may influence the realization of the hoped-for improvement in animal welfare in practice, we conducted a survey from 2003 until 2009 among representative samples of Flemish pig producers every 2 yr. The share of farms with group housing increased from 10.5% in 2003 to 29.8% in 2007, but then dropped to 24.6% in 2009. It appears that after 2005 users of old group housing systems in particular stopped farming. Because sow herd size increased more on farms with vs. without group housing and because the proportion of the herd that was group-housed also tended to increase between 2003 to 2009, the change to group housing took place faster when expressed at the level of the sow (from 9.1% in 2003 to 34.1% in 2009) instead of farm. The percentage of farmers planning to convert to group housing within 2 yr was 4.1% in 2003, and 6 to 7% thereafter. These were typically young farmers (P = 0.006) with a large sow herd (P < 0.001) and with a likely successor (P = 0.03). Free access stalls were the most common group housing system (31% of farms, 37% of sows). Their popularity is expected to increase further at the expense of electronic feeding stations, ad libitum feeding, and stalls/troughs with manual feed delivery. User satisfaction was generally high but depended on whether or not all gestating sows were kept in group (P < 0.001), the provisioning of environmental enrichment (P = 0.057), and the age (P = 0.012) and type (P = 0.016) of system. The main criteria for choosing a certain group housing system were the investment costs and sow health and welfare. The importance of economic reasons (P = 0.007) and type of labor (P = 0.043) decreased with the age of the system. In 2003 and 2005 the main reason for not having converted to group housing was that farmers would stop keeping sows by 2013. In 2007 and 2009 the reasons mainly concerned uncertainty about the future and maximally delaying the conversion. Belgium is one of the European Union countries where the pig industry is expected to undergo drastic changes during the few years remaining before the ban on individual housing.     

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.     

Well-being in Pregnant Sows: Confinement versus Group Housing with Electronic Sow Feeding

Abstract

Indicators of stress, behaviour in the pen, and lesions of the integument were used as indicators of sow well-being in a comparison of group housing with electronic sow feeding [GH] and confinement in gestation crates [C] in experiment 1, which included 2 × 4 groups of 20–25 sows. Effects of earlier experience with a gestation system on the indicators of stress was investigated in experiment 2, which included 2 × 3 groups of 20–25 sows. Reaction in a novelty test and reactivity in plasma Cortisol to the procedure of blood sampling were used as indicators of stress. Behaviour in the pen as well as lesions of the integument revealed that both gestation systems were suboptimal in some manner. However, following acclimatization for 1–2 weeks, young GH sows experienced less stress than young C sows as measured by reduced fear in the novelty test. In experiment 2 this interpretation was further supported by lower reactivity in plasma Cortisol. It was concluded that sow well-being was higher for the majority of the gestation period in young group-housed animals. Thus, in spite of the inadequate feeding method, well-being of sows may be improved in group housing systems with electronic sow feeding if the system is well functioning with low levels of aggression and vulva bites. One of the major determinants of vulva biting is suggested to be the mechanism of gate control.     

Effect of group size and structure on the welfare and performance of pregnant sows in pens with electronic sow feeders

Pregnant sows were housed in dynamic, twice-mixed, and static groups of different sizes in pens with electronic sow feeders (ESFs) to study the effect of group size and structure on sow welfare and performance. The total injury score (TIS) was significantly higher (P < 0.05) in the dynamic group than in the other groups in general and 2 wk after mixing. The salivary cortisol concentrations were similar in the 3 groups. The frequency of queuing was significantly higher (P < 0.05) in the twice-mixed group and the frequency of nonagonistic social interactions significantly lower (P < 0.05) in the dynamic group. The total number of aggressive acts was positively and significantly correlated (P < 0.05) with the frequency and duration of queuing in all the groups. Farrowing performance and longevity did not differ between the groups. The higher TIS and lower number of nonagonistic social interactions indicated that welfare was compromised in the dynamic group as compared with the other groups.     

The induction of parturition in sows using prostaglandin F2alpha

Intramuscular injections (10 mg) of prostaglandin F2alpha were administered to 19 pregnant sows in one herd on either the 112th or 113th day of gestation and a similar number of untreated sows served as controls. Induced sows for up to 6h after injection generally showed more walking, drinking defaceating and postural changes. Over the last 20 h prepartum they spent more time lying and urinated more frequently. Mean interval from injection to onset of parturition in treated sows was 24.5 h and 16 of them commenced farrowing during the working day, compared with 6 in the control group. Induction of parturition did not influence litter size at birth, piglet body-weights at birth or 14 days of age, the incidence of the mastitis, metrititis agalactae syndrome, re-breeding interval of the sow or size of the subsequent litter at birth. Farrowing time was significantly longer (6.48 h v 4.08 h) for treated sows and litter pre-weaning mortality was higher but not significantly so. Most piglet deaths in each group resulted from overlaying or starvation but mortality from anaemia and septicaemia occurred only in the treated group. It is considered that the technique could have practical application on well-managed intensive pig units.     

Social rank of pregnant sows affects their body weight gain and behavior and performance of the offspring

Previous studies on group housing of pregnant sows have mainly focused on reproduction, but we hypothesized that the social rank of pregnant sows housed in groups could also affect birth weight, growth, and behavior of their offspring. Therefore, in the present study, pregnant gilts and sows were housed in 15 different groups (n = 7 to 14 animals per group) from 4 d after AI until 1 wk before the expected farrowing date. All groups were fed by an electronically controlled sow feeding system that registered, on a 24-h basis, the time of first visit, number of feeding and non-feeding visits, and number of times succeeding another sow within 2 s. Only in the first 6 groups (n = 57 animals), agonistic interactions were observed continuously. The percentage of agonistic interactions won was highly correlated (r(s) = 0.90, P < 0.001) with the percentage of displacement success (DS) at the feeding station, which was calculated as: [the number of times succeeding another sow within 2 s/(the number of times succeeded by another sow within 2 s + the number of times succeeding another sow within 2 s)] x 100. This allowed us to classify all sows (n = 166) according to their DS: high-social ranking (HSR) sows had a DS >50% (n = 62) and low-social ranking (LSR) sows a DS <50% (n = 104). Body weights before AI did not differ between HSR and LSR sows, but HSR sows gained more BW during gestation, and lost more BW and back-fat during lactation (P < 0.001). Maternal salivary cortisol concentrations at 2, 7, and 13 wk after AI did not differ between HSR and LSR sows, nor did gestation length, litter size, or percentage of live born piglets. During a novel object (NO) test at 3 wk of age, HSR offspring moved and vocalized more than LSR offspring (P < 0.05). In addition, the latency time to touch the NO was shorter in HSR offspring (P < 0.05), and HSR males spent more time near the NO than LSR males (P < 0.01). At weaning, HSR offspring weighed more than LSR offspring (P < 0.05), and at slaughter HSR offspring had more lean meat than LSR offspring (P < 0.05). Results indicate that the social rank of the sow during gestation affects her own BW gain and loss as well as the growth and behavior of her offspring. Pig breeders that apply group housing for pregnant sows should pay attention to reducing competition around the feeding area, which may reduce aggression among the sows and minimize differences between HSR and LSR sows.     

The induction of parturition in sows using prostaglandin F2auml;

Intramuscular injections (10mg) of prostaglandin F2ä were administered to 19 pregnant sows in one herd on either the 112th or 113th day of gestation and a similar number of untreated sows served as controls. Induced sows for up to 6h after injection generally showed/more walking, drinking defaceating and postural changes. Over the last 20h prepartum they spent more time lying and urinated more frequently. Mean interval from injection to onset of parturition in treated sows was 24.5h and 16 of them commenced farrowing during the working day, compared with 6 in the control group. Induction of parturition did not influence litter size at birth, piglet bodyweights at birth or 14 days of age, the incidence of the mastitis, metrititis agalactae syndrome, re-breeding interval of the sow or size of the subsequent litter at birth. Farrowing time was significantly longer (6.48h v 4.08h) for treated sows and litter pre-weaning mortality was higher but not significantly so. Most piglet deaths in each group resulted from overlaying or starvation but mortality from anaemia and septicaemia occurred only in the treated group. It is considered that the technique could have practical application on well-managed intensive pig units.     

Cortisol response of gilts in tether stalls

Several experiments were conducted to evaluate serum cortisol concentrations and the circadian rhythm of this hormone in gilts tethered in stalls. Control animals were penned individually. In the initial experiment, 18 nongravid gilts were placed in tether stalls after being in either tether stalls or individual pens for 2 wk. No significant differences were found in serum cortisol concentrations. In a second experiment, 16 ovariectomized gilts were placed in tether stalls or individual pens for up to 5 wk. Estrus was induced during wk 3 and 4. During the first day in tether stalls, serum cortisol concentrations increased (P less than .05) and the circadian rhythm of cortisol was disrupted for 4 d. During estrus, the circadian rhythm of cortisol was interrupted for several days in the gilts, regardless of housing. After 4 wk, morning concentrations of cortisol were higher for gilts in tether stalls. The results indicate that: 1) the initial response to tethering varies according to previous penning and handling experience, 2) although the circadian rhythm of cortisol was either altered or disrupted during estrus, such disruptions were not influenced by type of penning and 3) tether stalls may chronically increase cortisol concentrations in gilts.