Breeding success of farmed silver foxes with top boxes

Transcription

1 8 Breeding success of farmed silver foxes with top boxes T Pyykonen*, J Asikainen**, M Miettinen***, J Mononen*, J Sepponen* & L Ahola* *Institute of Applied Biotechnology, University of Kuopio, P.O.Box 1627, Kuopio, Finland **Department of Biology, University of Joensuu, Joensuu, Finland ***Finnish Fur Breeders' Association, P.0.Box 5, Vantaa, Finland Abstract A nest box is a crucial part of the housing environment and a few earlier studies have shown that nest box configuration may influence reproduction and also animal welfare. Our study concentrated on the possible advantages of a top box as a breeding box for silver foxes. Silver fox vixens were provided with top boxes E group (154 primiparous, 70 multiparous) and with floor boxes C group (159 primiparous, 31 multiparous). As expected, the multiparous vixens reproduced markedly better than the primiparous vixens. In the primiparous vixens there were less ) barren femajes and more successful breeders with larger litters in the E group than in the C group. The reproductive performance (cubs per breeding female) was 0.7 cubs better in the top boxes than in the floor boxes. In the multiparous vixens, all variables pointed to better reproduction in E than in C, but the differences were not statistically significant. The differences between E and C groups were minor in the multiparous vixens but pronounced in the primiparous vixens. Accordingly it seems that the top boxes are beneficial in particular to primiparous vixens. Two-year field data, where top boxes were used as only breeding boxes for silver foxes, support the previous results. The reproductive performance was 2.7 cubs for the primiparous vixens and 3.1 cubs for the multiparous vixens. These values are good when compared to the national reproductive performance (2.82 cubs). There were no major differences between the multiparous and the primiparous vixens, which probably is a proof for the benefits of the top boxes especially to primiparous vixens. The top box can be recommended as a breeding nest box for farmed silver foxes. It is both practical and economical, and it may improve the welfare of the foxes.

2 1 NJF seminarium Vuokatti, Finland, 2 d-4th October 2002 Breeding success of farmed silver foxes with top boxes T Pyykonen*, J Asikainen**, M Miettinen***, J Mononen*, J Sepponen* & L Ahola* *Institute of Applied Biotechnology, University of Kuopio, P.O.Box 1627, Kuopio, Finland **Department of Biology, University of Joensuu, P.0.Box 111, Joensuu, Finland ***Finnish Fur Breeders' Association, P.0.Box 5, Vantaa, Finland Introduction ) The reproduction of farmed foxes varies considerably between farms and individual vixens. Reproductive performance is affected by the animal itself and the housing environment (Harri et al. 2000). A nest box is a crucial part of the housing environment during the breeding time and the type of the box may influence reproductive performance. Foxes have been traditionally provided with breeding nest boxes placed on the floor of the cage, and the boxes consist of a small anteroom and a larger main room. Recently, it has been shown that an entrance tunnel through which the fox enters the box improves reproductive performance in both silver foxes (Vulpes vulpes, Braastad 1994, 1996) and blue foxes (Alopex lagopus, Haapanen et al. 1990). The positive effects of the tunnel were pronounced especially in primiparous vixens. The effect may be stress related. The vixens may feel safer and less stressed in a more complicated nest box. Less stress may in tum reduce abortions during late pregnancy and neonatal cub deaths. Accordingly, it is obvious that a nest box that improves foxes reproductive performance may also have prominent positive welfare effects on both the vixens and the cubs. Another option is a top nest box, which is placed on the roof of the cage. In choice tests vixens of both fox species preferred a breeding box mounted high up in the cage to a box mounted lower as a place to give birth and nurse the cubs (Jeppesen and Pedersen 1990). A small-scale study in blue foxes showed that top boxes are at least as good breeding boxes as traditional floor boxes (Mononen e~ al. 1999). In primiparous blue foxes the number of barren females was even lower in vixens with top boxes than in vixens with floor boxes. The aim of the present study was to provide field information on the usefulness of a top box as a breeding box for silver foxes.

3 2 Material and methods The experimental data was collected from the Siikasalmi Research Station of the University of Joensuu in years and the Juankoski Resear~h Station of the University of Kuopio in years Siikasalmi The experimental vixens were provided with wooden nest boxes, either a top box (E) or a floor box (C). The floor boxes consisted of two anterooms (25 x 42 x 36 cm and 17 x 42 x 36 cm, length x width x height) and a main room ( 43 x 42 x 36 cm). They were placed on the floor inside the breeding cages. The cages with floor boxes were without platforms, but the animals could use the roof of the box as a platform. The top boxes were mounted on the roof of the cages and consisted of an anteroom (46 x 46 x 36 cm) and a main room (42 x 46 x 36 cm). A wire-mesh platform ( x 30 cm) was hung 25 cm below the cage ceiling to enable the foxes to enter the top box. The openings through which the foxes entered the boxes or the various compartments of the boxes measured in both box types 20 x cm. Cages were of four size measuring x 105 x 70cm. There were a total of 313 primiparous and 101 multiparous silver fox vixens in the study. The number of the primiparous and multiparous vixens in the top box group (E) was 154 and 70 and in the control group (C) 159 and 31, respectively. (Thus, the groups were biased towards primiparous females, what is the opposite of the normal situation on commercial fur farms). The foxes were artificially inseminated and placed in the experimental shed houses in expected whelping order. Due ) to the field nature of the present experiment all factors were not fully controlled: cage size, placing of foxes in shed houses and time for providing foxes with nest boxes. However, these factors were reasonable well equal between the two experimental groups. The cubs were not counted at birth but it was only recorded whether or not a vixen had cubs. The cubs were counted at ten days of age and at weaning (49 days). Reproductive performance has been expressed as presented in Table 1. Comparisons between the age classes or experimental groups for the numbers of barren females, the females that lost all their cubs and the females that reproduced successfully were performed with x 2 -test. Litter size and reproductive performance comparisons were calculated with Mann-Whitney test. The timing of insemination was biased so that in primiparous females E vixens were inseminated about week before the C vixens (P<0.001, analysis of variance). Therefore the difference in the total reproductive performance between the

4 3 groups was compared also with the analysis of covariance (ANCOV A) where the insemination day was used as the covariate. Table 1. Variables describing reproductive performance of silver fox vixens in the Siikasalmi experiment. Variable Barren Litters lost until I 0 d Explanation The number of vixens that did not give birth to any cubs The number of vixens that had had cubs (one or more), but who had lost all of them until the age of 10 d Litters lost until weaning The number of vixens that had had cubs (one or more), but who had lost all of them until the age of 49 d Successful at 10 d The number of vixens that had cubs (at least one) when the cubs were 10 d old Successful at weaning The number of vixens that had cubs (at least one) when the cubs were 49 d old Litter size at 10 d The number of cubs per vixen; calculated for the vixens that had cubs (at least one) at the age of 10 d Litter size at weaning The number of cubs per vixen; calculated for the vixens that had cubs (at least one) at the age of 49 d (i.e. the same vixens as at 10 d because entire litters were not lost after 10 d of age) Reproductive performance 10 d The number of cubs per vixen at 10 d; calculated from all - ) = RP at 10 d inseminated vixens, i.e. includes also barren vixens and vixens that lost all their cubs Reproductive performance 49 d The number of cubs per vixen at 49 d; calculated from all = RP at 49 d inseminated vixens, i.e. includes also barren vixens and vixens that lost all their cubs Juankoski In the Juankoski Research Station a total of 60 breeding vixens (13 pnm1parous and 47 multiparous) were provided with a wooden top box in the breeding seasons of the years 2001 and The boxes were mounted on the top of standard fox cages measuring 115 x 105 x 70 cm. A wall with a round opening (diameter 20 cm) separated the anteroom (44 x 32 x 33 cm) and the main room ( 44 x 44 x 33 cm). A wire-mesh platform (30 x 105) was hung about 25 cm from the ceiling

5 4 so that an animal could enter the box through a round opening (diameter 20 cm) in the bottom of the anteroom. The front wall of the top nest boxes could be opened for detecting and counting the cubs, which was done two weeks after delivery. The reproductive performance was calculated as in the Siikasalmi experiment with the exception that there was data available only until the day that the cubs were around two weeks old. Primiparous and multiparous vixens were compared as in the Siikasalmi experiment. Results & Discussion As expected, mulriparous vixens had markedly better reproductive performance than the primiparous vixens (Table 2). Therefore the effects of the two types of nest boxes on the reproductive performance were analysed separately for the two age classes in the Siikasalmi experiment. Losses of entire litters were not observed between 10 d and weaning (49 d). Therefore "Litters lost until 10 d" and "Successful at 10 d" have been skipped from the nest box comparisons (see Table 3). Table 2. Reproductive performance of primiparous and multiparous silver fox vixens in the Siikasalmi experiment. See Table 1 for the explanations of the variables. =not significant (P>O.l). Variable Primiparous Multiparous P (X 2 -test or Mann- (N=313) (N=lOl) Whitney test) ) Barren 85 (27%) 22 (22%) Litters lost until 10 d 89 (28%) 13 (13%) <0.001 Litters lost until weaning 89 (28%) 13 (13%) <0.001 Successful at 10 d 139 (44%) 66 (65%) <0.001 Successful at weaning 139 (44%) 66 (65%) <0.001 Litter size at 10 d 3.5± ±1.5 <0.001 Litter size at weaning 3.3± ±1.5 <0.001 RP at lod 1.6± ±2.4 <0.001 RP at49 d 1.5± ±2.4 <0.001 In the primiparous vixens all parameters except "Litters lost until weaning" showed that top boxes are better breeding boxes than the floor boxes (Table 3). Thus, the nest box type affected

6 5 reproduction both postpartum and prepartum. The postpartum effects are easier to explain. If a vixen feels the breeding nest box safe and comfortable, it chooses to stay with her cubs and nurses them, whereas unsafe or uncomfortable box may have negative effects on maternal behaviour of stress sensitive individuals. The effect on the number of barren females is more surprising, although the same effect has been observed also in blue foxes (Mononen et al. 1999). Since the nest boxes are given to the vixens in the latter part of the pregnancy, the positive effect of the top boxes must result from a reduced number of abortions of entire litters. Table 3. The reproductive performance of primiparous and multiparous silver fox vixens with top nest boxes (E) or floor nest boxes (C) in the Siikasalmi experiment. P: comparison of E and C within each age class; X 2 -test or Mann-Whitney test. ) Variable Primiparous (N=313) Multiparous (N=lOl) E c p E c p Number of inseminated vixens Barren 32 (21 %) 53 (33%) < (21%) 7 (23%) Litters lost until weaning 43 (28%) 46 (29%) 7 (10%) 6 (19%) Successful at weaning 79 (51 %) 60 (38%) < (69%) 18 (58%) Litter size at 10 d 3.8± ±1.6 < ± ±1.6 Litter size at weaning 3.5± ±1.5 < ± ±1.6 RP at lod 2.0± ±1.8 < ± ±2.5 RP at49 d 1.8± ±1.7 < ± ±2.5 The E animals were inseminated on an average a week earlier than the C animals in the primiparous vixens. Vixens that have their heat and give birth late in the breeding season tend to have poorer reproduction. This was the case also in the primiparous vixens in the present experiment (r=-0.11, p=0.059, Pearson correlation). Therefore it might be possible that the differences between the E and C vixens result from the bias in the breeding time between the groups. ANCOV A showed, however, that the difference in the reproductive performance at weaning remained (P<0.05) although the insemination date was used as the covariate. In the multiparous vixens, all variables pointed to better reproduction in the top boxes than in the floor boxes, but the differences were not statistically significant (Table 3). Furthermore the

7 6 differences between the E and C groups especially in the litter size and total reproductive performance were not so marked in the multiparous than in the primiparous foxes. Accordingly, it seems that the top boxes are beneficial in particular to primiparous foxes. The positive effects of alternative nest boxes on reproduction in primiparous foxes has been observed also earlier in silver foxes (tunnel box, Braastad 1994) and in blue foxes (top box, Mononen et al. 1999). The reproductive ability of multiparous vixens has already been tested and the individuals that were affected by possibly sub-optimal farming conditions have been selected out from the breeding stock, whereas the primiparous part of the stock includes a larger proportion of individuals that are still prone to be affected by the sub-optimal farm environment. Thus, it is not surprising that any improvements to the farming practice during the breeding time affect more clearly the primiparous animals. Encouraged by the preliminary results from the Siikasalmi Research Station we started to use only top boxes as breeding boxes for our silver foxes in the Juankoski research station. Our e~periences from the first two years ( ) are promising. The total reproductive performance ':in the top boxes was 3.0 cubs per breeding female. This can be considered as good since the national total reproductive performance in the year 2001 was 2.82 cubs. Although the number of breeding vixens has been limited, the results show, that there are no major differences in the breeding success of primiparous and multiparous vixens (Table 4). This could be predicted from the Siikasalmi experiment where the top boxes were beneficial in particular for the primiparous vixens. In addition to that young vixens seem to reproduce better in the top than floor boxes, the top boxes have some other advantages (as reviewed in Mononen et al. 1999). The top box does not ) demand space inside the cage and it does not obstruct the view from the cage. As the top box is situated higher than the traditional floor box and the front wall of the top box can be opened, inspection of the nest box is an easy task for the farmer. Human-animal relationship can be improved if the solid front wall is replaced with a wire-mesh wall when the cubs are young. After the breeding season top boxes need no warehouse, because they can be left on the top of the cages. Top box can be simple in construction and therefore of reasonably cheap in price. Conclusions The top box can be recommended as a breeding nest box for farmed silver foxes. It is both practical and economical, and it may improve the welfare of the foxes.

8 7 Table 4. Reproductive performance of silver fox vixens in top boxes in the Juankoski Research Station. The data is based on data collected for Sampo breeding software. See Table 1 and text for detailed explanation of the variables. P: x 2 -test or Mann-Whitney test. Variable Total Primiparous Multiparous p N=60 N=22 (N=47) Barren 6 (10%) 1 (8%) 5 (11 %) Litters lost until 14 d 12 (20%) 3 (23%) 9 (19%) Successful at 14 d 42 (70%) 9 (69%) 33 (70%) Litter size at 14 d 4.2± ± ± 1.6 RP at 14 days 3.0 ± ± ±2.4 ) References Braastad B Reproduction in silver fox vixens in breeding boxes with and without an entrance tunnel. Acta Agriculturae Scandinavica, Section A- Animal Science 44: Braastad B Behaviour of silver foxes in traditional breeding boxes and in boxes with an entrance tunnel. Animal Welfare 5: Haapanen K, Harri M, Mononen J, Korhonen H, Niemela P, Rouvinen K and Fors F Lymodellens och andra miljofaktorers inverka pa blaravens valperesultat. NJF-Seminariurn nr September 1990, Kopenhagen, Danmark. Harri M, Mononen J, Rekila T, Ahola 1 and Pyykonen T Attempts to improve reproductive performance of farmed foxes. In: NN Tyutyunnik, LK Kozhevnikova, VA Ilukha, VM Oleinik_and LB Uzenbaeva (Eds), Problems of Ecological Physiology, Fur Animals. Karelian Recearch Centre, ) Russian Academy of Science, Institute of Biology. Pp Jeppesen LL and Pedersen V hnprovement of management routines and cage systems in fox production. Scientifur 14: Mononen J, Harri M, Sepponen J, Korhonen H, Rekila T & Ahola L A top box and a floor box as breeding nest boxes in farmed blue foxes (Alopex lagopus): Reproductive performance, use of the boxes and cub currying. Acta Agriculturae Scandinavica, Section A- Animal Science 49: NJF seminarium Vuokatti, Finland, 2nd _4th October 2002