Beschreibung
Background
Current socio-political discussions about a reorientation of agriculture also include the issue of animal husbandry. Here, the economic interest seems to be partly opposed to an improvement in animal welfare. To gain insight into the degree to which increased space around parturition represents an improvement for pigs and, if so, whether sows of a modern high-proliferate breed can also benefit from this, two different housing conditions were used in this study. In addition, a breed comparison was made between the courses of parturition of German Landrace dams (GLR), as representatives of a highly proliferative breed, and those of Angeln Saddleback pigs (ASB) as a robust breed, to gain insight into their respective birthing stability. The scope of investigation included clinical, endocrinological and metabolic parameters. Pre-weaning mortality and vitality of piglets were also studied.
Material and method
The study took place at the Leibniz Institute for Farm Animal Biology, Dummerstorf, Mecklenburg-Vorpommern. Pigs of the GLR (n=26) were chosen as representatives of the modern breeding line, and those of the ASB (n=20) as the native breed. Animals were transferred to one of two housing conditions on the 105th day of gestation. In the farrowing pen, the dams had a total area of 5.8 m2 at their disposal, while under farrowing crate conditions they had an area of 1.08 - 1.26 m2, depending on body size. From the 112th day of gravidity, the animals were equipped with a venous indwelling catheter. Until the onset of parturition, blood samples were taken, and clinical examinations were performed daily. From the beginning of the expulsive phase (stage II of parturition), this examination scheme was performed at half-hourly intervals until the end of the expulsive phase. This was followed by daily checks until the fourth day post-partum. Expulsion intervals of more than 60 minutes were defined as birth complications. Obstetric intervention in such cases consisted of manual vaginal exploration. Post natum, piglets were examined for vitality and pre-weaning mortality was recorded until one week after birth. Clinical examination of the dams included body temperature, respiratory rate, and heart rate. Hormone levels obtained from blood samples were progesterone, estradiol, oxytocin, PGFM, cortisol, epinephrine, and norepinephrine. Metabolic parameters determined were total calcium, ionized calcium, magnesium, phosphorus, glucose, NEFA, bHBA, and creatine kinase.
Results
GLR had a gestation period 1,4 days longer than ASB dams (GLR: 115,8 ± 1,29; ASB: 114,6 ± 1,27). Litter size was on average 3,3 piglets larger in GLR dams than ASB (GLR: 14,7 ± 3,61, ASB: 11,4 ± 3,08, p = 0,0041). Mean birth length differed significantly between breeds (GLR: 266,6 ± 126,1, ASB: 173,0 ± 104,7, p = 0,0115). The decisive factor for this difference was that GLR pigs had a significantly higher rate of birth protractions based on myometric hypotonia than ASB animals, regardless of housing conditions. While 46% of births in GLR animals were affected by this complication, only 12% in ASB animals were (p = 0,0186). While up to 5 protractions of > 60 min were recorded in farrowing crate births in the dystocia group, a maximum of two such delays occurred under farrowing pen conditions (p = 0,0866). In eutocia, the mean expulsion interval until expulsion of the third piglet was 18,5 (x ?g, SF = 1,71) min and in dystocia 32,9 (x ?g, SF = 2,42) min. Dystocial courses thus showed significantly longer expulsion intervals (p = 0,0012) even before the first protraction occurred.
The evaluation of the clinical parameters revealed a significant influence of the interaction breed x time on the measured body temperatures (p = 0,0129) and respiratory rates (p = 0,0109). ASB animals showed a lower temperature trend than GLR animals ante partum as well as at the end of parturition and especially in the early post-partum period. In contrast, for respiratory rate, ASB animals showed a slightly higher level over time than GLR animals. Husbandry conditions had no effect on these parameters. There was a significant breed difference with respect to heart rates. GLR animals showed significantly higher values than ASB animals (p = 0,0287). The course of parturition (eutocia or dystocia) affected the clinical parameters in such a way that during stages II and III of parturition dystocia-sows had higher respiratory rates than eutocia-sows (p = 0,0001).
Both pig breeds entered parturition with similarly high P4 levels around 17 ng/ml. During the expulsive phase, P4 concentrations remained constant at this level. Only at the transition to the post-partum period did a reduction to baseline values occur, with a steeper declining profile in GLR animals than in ASB animals. No husbandry-related influences on P4 progression could be detected.
Estradiol concentrations were significantly higher in GLR animals than in ASB animals throughout the peripartum period (a.p., i.p. and p.p.: p = 0.0127; 0.0045 and 0.0320, respectively). In ASB animals, the influence of the husbandry x time-interaction was evident at the transition to stage III of parturition in that dams that gave birth in the farrowing pen showed a steeper loss of values than those in the farrowing crate.
From the last day of gestation until the birth of the first piglet (stage II), ASB dams showed a significantly greater increase in oxytocin than those of the GLR breed (p = 0.0359). Within the expulsive phase, the breed x time-interaction was significant (p = 0.0257). This was expressed in that levels in ASB animals started at a significantly higher level, increased even slightly during stage II, but showed a decreasing trend in the last third of the expulsive phase. In contrast, concentrations in GLR animals were at a lower level but showed a distinct increase in quantities sub partu that persisted until the end of stage II. Eutocia oxytocin concentrations in GLR pigs were at significantly higher levels than in dystocia as soon as they entered stage II parturition, and this increased significantly as they progressed (p = 0.0082). Among the GLR births, it was found that in 35% of these births, only low to moderate oxytocin quantities were registered within the expulsive phase, remaining significantly below 60 pg/ml. Sows with such low oxytocin concentrations within parturition suffered from birth protraction in 85.7% of cases. In ASB animals, this hypooxytocinemia was detected in only one of 17 births (5.9%). An influence of the housing conditions on the intrapartum oxytocin profiles could only be proven at the transition of stage II to the early post-partum phase, in which ASB animals that had given birth in the farrowing pen showed a steeper drop in values than animals from the farrowing crate group.
PGFM concentrations were not influenced by breed or housing conditions. Only at the transition from stage II to stage III of parturition was the interaction between breed x time relevant in that GLR animals still had PGFM concentrations twice as high as ASB animals on the first day post-partum (p = 0.0215). The comparison of PGFM concentrations between the group of GLR animals that gave birth under normative oxytocin and those with a reduced oxytocin profile showed that the first group had significantly lower values than those with permanently reduced oxytocin quantities.
Measurements of cortisol revealed a significant effect of breed on concentrations (a.p., i.p., and p.p.: p = 0.0001; 0.0020; 0.0058, respectively). Throughout the peripartum period, levels in ASB animals were significantly higher than those in GLR animals. Individual ASB animals were characterized by cortisol concentrations significantly above the mean. The only common feature of these animals was a significantly earlier parturition date that fell on days 112 and 113 (mean DLR: 115.8 ± 1.29, ASS: 114.6 ± 1.27 d). No influence of housing conditions on cortisol concentrations could be detected at any point in time.
For epinephrine, antepartum concentrations were visibly higher in ASB animals than in GLR animals (p = 0.0053). Neither intra- nor post-partum this difference was found again. Epinephrine and norepinephrine were the only two endocrinological parameters which were significantly affected by the influence of housing conditions at one stage of parturition, without interaction with any other factors. While, at the end of parturition, GLR animals in the farrowing crate had 60% higher adrenaline concentrations than animals in the farrowing pen, ASB animals showed a completely opposite result. At the last sampling time point in the expulsive phase, adrenaline concentrations were 170% lower in ASB dams that had given birth in farrowing crates compared to those in farrowing pens. However, these ratios reversed on the first day postpartum, with crate animals having 70% higher adrenaline concentrations than farrowing pen animals (p = 0.0406).
Also, as with epinephrine, norepinephrine levels were at significantly higher levels antepartum in ASB animals than GLR animals (p = 0.0023). However, in contrast to epinephrine, norepinephrine levels remained at higher levels in ASB even within the expulsive phase. The influence of housing conditions on norepinephrine levels was evident at the end of the expulsive phase (p = 0.0248). GLR animals under farrowing pen conditions revealed a more than twofold decrease in norepinephrine concentrations from the last sampling time point intrapartum to the first post-partum day than animals of the same breed under farrowing crate conditions. The same effect was seen in ASB animals but was even more pronounced here.
When evaluating the total calcium measurement results, significant influences of the breed x time (p = 0.0312) and husbandry x time (p = 0.0109) interactions were evident in the intrapartum period. Total Ca concentrations in ASB pigs were, over this period, lower than those in GLR. This difference built up until minute 120 of the expulsive phase, then converged again until the end of this stage. It is interesting to note that GLR dams whose parturition proceeded with complications had lower total Ca values even before the onset of the expulsive stage. This lower level persisted until the 150th minute intra partum, but after that there was no difference between Eutocia and Dystocia groups. Regarding the influence of housing conditions, it could be seen in both breeds that the values of the farrowing pen animals lagged behind those of the farrowing crate animals.
Comparison of concentrations of ionized calcium showed no significant differences between breeds or housing conditions.
Magnesium proved to be dependent on the breed x time interaction within the expulsion phase (p = 0.0215). Over this period, concentrations in GLR animals were higher than those in ASB animals. In the antepartum phase, magnesium was significantly affected by housing (p = 0.0053) and in the ante- and intrapartum periods by the housing x time interaction (a.p.: p = 0.0274, i.p.: p = 0.0490). In GLR breed, higher Mg concentrations were present in farrowing pen animals than in farrowing crate animals. In ASB animals, antepartum values of farrowing pen animals were also higher than those of farrowing crate animals. At the beginning of the expulsion phase, the ratios were reversed, but during stage II, there was a two-phase increase in the values in farrowing pen animals.
The development of phosphate levels, breed differences occurred only in the postpartum period (p = 0.0398). Concentrations in GLR animals were higher than those in ASB animals until postpartum day 4. In contrast, an influence of housing was evident both antepartum and intrapartum. In the group of ASB dams, significantly higher concentrations were present in farrowing pen births than in farrowing crate births. In GLR animals, this relationship was only subtle.
Concentrations of glucose were neither breed- nor posture dependent at any stage of the peripartum period.
NEFA concentrations in ASB animals were significantly higher than those of GLR animals throughout the parturition period (a.p., i.p., and p.p.: p = 0.0003; 0.0001; 0.0002). No effect of housing was evident.
For bHBA, the concentrations of ASB animals were also significantly higher than those of GLR animals (a.p., i.p. and p.p.: p = 0.0055; 0.0111; 0.0217). No dependencies of the housing conditions could be detected.
Direct comparison of breeds showed no differences for creatine kinase. In ASB animals, there were visible influences of housing conditions. Animals under farrowing pen conditions had significantly lower CK concentrations ante- and intrapartum than animals under farrowing crate conditions.
In addition, piglet vitality immediately postnatum and pre-weaning mortality rates, categorized into periods up to day 7 of life, were also recorded. There were no differences in the distribution of piglet vitalities between breeds and housing types. The mortality rate in GLR was 10.9% in the first postpartum week, while in ASB it was 14.3%. This difference was not statistically significant. Also, the housing conditions had no significant influence on the mortality rates.
