Behavioural response to mixing of entire bulls, vasectomised bulls and steers

Applied Animal Beha viour Science, 31 ( 1991 ) 157-168

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Behavioural response to mixing of entire bulls, vasectomised bulls and steers A.B. Mohan Raj ~'~, B.W. MOSS a'b'2, W.J. McCaughey ~, W. McLauchlan d, D.J. Kilpatrick e and S.J. M c G a u g h e y r aDepartment of Food and Agricultural Chemistry, The Queen's University of Belfast, Newforge Lane, BelJast BT9 5PX, UK bFood and Agricultural Resealvh Division, Department of Agriculture for Northern h'eland, New,forge Lane, Belfast, BT9 5PX, UK cVeterinary Research Laboratory, Department of Keterinary Science, The Queen's University of Belfast, Stoney Road, Stormont, Belfast, BT4 3SD, UK and Department of Agriculture for Northern Ireland, Stoney Road, Stormont, Belfast, BT4 3SD, UK aExperimental Husbandry Farm, Castle Archdale, Irvinestown, BT94 1PT. UK and Department of Agriculture for Northern Ireland, lrvinestown, BT94 IPT, UK ~Department of Biometrics, The Queen's University of Belfast, Neuforge Lane, Belfast BT9 5PX, UK and Department of Agriculture for Northern Ireland, Ne~forge Lane, Belfast, BT9 5PX, UK flood Industry Marketing Service, Department of Agriculture for Northern Ireland, Manor ttouse, Loughgall, BT61 8JA, UK (Accepted 19 February 1991 )

ABSTRACT Mohan Raj, A.B., Moss, B.W., McCaughey, W.J., McLauchlan, W., Kilpatrick, D.J. and McGaughey, S.J., 1991. Behavioural response to mixing of entire bulls, vasectomised bulls and steers. Appl. Anita. Behav. Sci., 31: 157-168. Four groups of cattle each consisting of two entire bulls, two vasectomised bulls and two steers, were created by mixing the constituent animals together and their homosexual (teasing and mounting) and aggressive (butting and pushing) behaviours were investigated in detail for the initial 4-h period. The behavioural interactions differed between groups as a result of the different temperament of animals. Vasectomised bulls were homosexually hyperactive but less aggressive compared with entire bulls. The homosexual behaviours were expressed in a preferentially unidirectional manner irrespective of the male type. The motive of mounting appeared to be both antagonistic as well as sexual. Aggressive behaviours occurred in retaliation to homosexual acts. Statistically significant positive correlations were found between the homosexual and aggressive behaviours.

INTRODUCTION

Dark-cutting or dark firm dry ( D F D ) beef is a direct consequence of physical activity or emotional stress prior to slaughter (McVeigh et al., 1982). Pre-slaughter mixing of bulls and steers is a typical stressor which leads to this condition through high rates of both aggressive and sexual activities (Price Ipresent address: D e p a r t m e n t of Meat Animal Science, School of Veterinary Science, University of Bristol, Langford, Bristol, BSI8 7DY, UK. 2Author to w h o m correspondence should be addressed. 0 1 6 8 - 1 5 9 1 / 9 1 / $ 0 3 . 5 0 © 1991 Elsevier Science Publishers B.V. All rights reserved.

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and Tennessen, 1981 ). Evidently it is the physical exertion owing to mounting behaviour which has a deleterious effect on meat quality (Kenny and Tarrant, 1984 ). The rate of mounting is higher among unfamiliar bulls and steers than among familiar animals (Fabiansson et al., 1984 ) and in general is higher among bulls than among steers (Tennessen et al., 1985). The agonistic encounters that occur during mixing are c o m m o n to all the animals, and help to establish social dominance. Such dominance behaviours have, however, been reduced by procedures such as the removal of submaxillary salivary glands in pigs (McGlone, 1985 ) and implantation of 17-fl oestradiol (Compudose) in feedlot bulls (Baker and Gonyou, 1985 ). There have been conflicting reports on the motive for mounting behaviour in bulls (Hafez and Bouissou, 1975; Reinhardt et al., 1978 ). Robertson et al., (1982) suggested that immunocastration of bulls produced more docile behaviour. Vasectomy of bulls is used to produce teasers for detecting oestrus in cattle and thus by implication is considered not to affect heterosexual behaviour. There have not been any reports on the effect of vasectomy in bulls on their behaviour and subsequent meat quality. However, Mohan Raj et al. (1991 ) suggested that vasectomised bulls could be more susceptible to dark-cutting than entire bulls and immunised bulls, even under a controlled pre-slaughter handling situation. Considering the restrictions on the implantation of steroids in steers and the intrinsic behavioural problems leading to dark-cutting meat in bulls, it was felt that there was a need for a better understanding of animal behaviour to control the situation both at production and at marketing. Therefore, an experiment was designed to investigate the behavioural patterns of entire and emasculated male cattle using entire bulls (EB), vasectomised bulls (VB) and steers (S). ANIMALS, MATERIALS AND METHODS

Experimental animals The experimental animals were 15-16 months old male Limousin and Simmental cross Friesian cattle comprising EB, VB and S obtained from two beef herds, maintained under similar management practice in one farm, referred to as two replicates. Caudal epididymectomy (subsequently referred to as 'vasectomy') of the VB calves was performed by the method of McCaughey and Martin (1980) at the age of about 91 days, and total castration under anaesthesia was performed on S calves at about 82 days. These animals were penned in groups of eight or nine of the same male type for 260 days until the time of mixing and were handled for weighing, blood sampling and testicular measurements at fortnightly intervals. Four animals were randomly chosen from each group of Replicate 1 and allocated at random to each of two exper-

RESPONSE TO MIXING OF BULLS AND STEERS

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imental mixed groups. This was repeated using four animals of each group from Replicate 2.

Animal handling and mixing Prior to mixing, animals selected for a particular group were identified by a code number painted on their backs. All animals had been fasted for 20 h prior to mixing to obtain an assessment of their empty body weights as part of a production experiment in which they were involved. At 16:00 h on the day of the experiment, animals were mixed in a large open yard which was familiar to all the animals and were then immediately moved to a pen of 3 X 7 m and allowed to stay overnight. The behaviours were recorded, using portable video recorders, continuously for the initial 4 h from the time of mixing. After 1 h of recording time ( 17:00 h), the animals were fed at the rate of 4 kg of concentrates per head and offered silage ad libitum. The video recordings were viewed and scored for the occurrence of aggressive (i.e. butting and pushing) and sexual (i.e. teasing and mounting) behaviours. The descriptions of each kind ofbehaviour are: (a) butting, one animal butts another, usually at the flank or shoulder; (b) pushing, two animals butt their heads together and push; (c) teasing, sexually motivated activities like licking of rump, chin resting on other animal's hind quarters and attempted mounting; (d) mounting, one animal mounts another from any angle. The video recordings were analysed by dividing the entire duration of recording (4 h) into 16 periods of 15 min each, and the cumulative occurrence of any one kind of behaviour over a 15 min period was expressed as events per period. Interactions between any two individuals were scored as two-way events. Thus, a score of 1 was recorded under 'exhibited act' for an animal which initiated an interaction and a score of 1, along with the exhibitor's identification number, was recorded for the same act for the animal which 'received' the interaction. As each experimental group comprised three different male types, the results could be analysed for between-groups differences, male-type differences, individual's preferential expression of homosexual behaviours and the relationship between aggressive and homosexual behaviours.

Statistical methods A 4 X 4 contingency table (four experimental groups and four kinds of behavioural interactions) was used to test the significance of differences between the experimental groups in their total number of interactions over the 4 h period. Friedman's analysis of variance test for ranked data Was performed on the individual animal's behavioural scores for 4 h to determine the differences between the male types for each behaviour. In addition correla-

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R A J E T AL.

tion coefficients were calculated for the overall data to determine the relationships between the behavioural interactions. RESULTS

After penning, all animals showed typical exploratory behaviour, for example smelling and licking, especially at the corners of the pens. This investigation of the environment was common during the initial 5 min and sniffing of group members' genitalia and hind quarters was frequent during this period. Vasectomised bulls and entire bulls showed more of this kind of'genital sniffing' behaviour than steers. After 10 min they began interactions such as butting, pushing, teasing and mounting. 8

~6

--I~----

entire b u l l s

------o---- vasectomisedbulls + steers

& 4

Time

of feeding

~2 z

.= 6

4 E = z

2

.~ 6 4 E

2 0 8

"== 6

g E

4

E_2

Z

,

,

,

,

,

,

0

15

30

45

60

75

,

,

,

,

,

,

,

,

,

,

,

,

90 105 120 135 150 165 180 195 210 225 240 255 T i m e f r o m m i x i n g (rain)

Fig. 1. Behavioural pattern of male types of cattle from the time of mixing.

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The amount of pushing per 15-min observation period was low and did not show any marked trends with time from mixing for any of the sex types (Fig. 1 ). Of the other behaviours (mounting, teasing and butting), the mounting of the vasectomised bulls and butting of the entire bulls tended to decline with time from mixing. There was no clear time-related trend in the activity of the steers for any of the behaviours studied.

Group comparisons and correlations between behaviours Figure 2 shows the type of behavioural interactions that occurred in the four experimental groups. Analysis by using a 4 X 4 contingency table (four experimental groups and four kinds ofbehaviour) showed that the four groups differed significantly in their behavioural interactions (Z 2= 236.6; d.f. = 9; P<0.001 ). The ratio of homosexual to aggressive behaviour ranged from approximately 2:1 (Groups 1 and 4) to 1 : 1 (Groups 2 and 3) and did not appear to be a function of total activity within a group. There was a wide range of individual behaviour scores and in many cases these were expressed preferentially between pairs of animals. In this regard, the homosexually hyperactive animals expressed 80-90% of their total number of teasing and mounting events on their partners within the group. Thus the total group score may be derived principally from two or three animals within the group. Correlations between the different behavioural interactions exhibited and received by the experimental animals are presented in Table 1. As the majority of the exhibited teasing was followed by mounting, there was a statistically significant correlation between these two homosexual acts (r=0.79; P < 0.001 ). Correlation between these two interactions and their preferential expression strengthened when the correlation between teasing received and mounting received by the animals was calculated (r--0.94; P < 0.001 ). Butting, however frequent or forceful, was an aggressive behaviour occurring mainly in retaliation to the homosexual acts. Thus, butting received 1200 1000 800 600 400 200 0 1

2

3

4

Group numbers

•

mounting

[] teasing

[] butting

[] pushing

Fig. 2. Behaviouralinteractions in four mixed groups of male types of cattle.

1 6 ")

A.B. M O H A N RAJ ET AL.

TABLE 1 Correlations between the behavioural interactions I of four groups of mixed male types in cattle

MR TE

TR BE BR PE PR

ME

MR

NS 0.79*** NS NS 0.75*** NS 0.57**

-

NS 0.94*** 0.64*** NS NS NS

TE NS NS 0.56** NS 0.43*

TR

BE

BR

PE

NS 0.53** NS

NS 0.76***

NS

0.57**

NS NS NS

~ME, mounting exhibited; MR, mounting received; TE, teasing exhibited; TR, teasing received: BE, butting exhibited; BR, butting received; PE, pushing exhibited; PR, pushing received. Statistical significance of differences (d.f. = 2 2 ) : NS, not significant; *P<0.05; **P< 0.01; ***P< 0.001.

showed significant correlations with mounting exhibited ( r = 0.75; P < 0.001 ) and teasing exhibited (r=0.56; P < 0 . 0 1 ). Similarly the mounting received and teasing received were significantly correlated with the butting exhibited (r=0.64, P<0.001; r=0.57, P < 0 . 0 1 , respectively). There were significant correlations between the homosexual acts exhibited and pushing received (r=0.57, P < 0 . 0 1 ; r=0.43, P < 0 . 0 5 for mounting and teasing, respectively), between butting exhibited and pushing exhibited ( r = 0.53; P < 0.01 ), and between the butting received and pushing received ( r = 0.76; P < 0.001 ).

Comparison between male types Owing to the involvement of three different male types in each experimental group, the data were subjected to Friedman's non-parametric test to check for any behavioural differences between the male types. The results are presented in Table 2. Although individual variations were found between the same male type of different experimental groups, the mean values for each behaviour exhibited showed that the vasectomised bulls were homosexually hyperactive as they showed more mounting and teasing behaviour in comparison with the entire bulls and steers (Fig. 1 ). The mean values for exhibited butting and pushing showed that the entire bulls, followed by steers, were more aggressive than the vasectomised bulls. The differences between the male types were statistically significant for exhibited teasing ( P < 0.01 ) and butting ( P < 0 . 0 5 ) . These contributed most to the overall differences in their homosexual and aggressive scores. Similarly when the acts received by different male types were investigated (Table 2 ), it clearly showed that the entire bulls received the highest number of mountings and teasings, while the vasectomised bulls received the majority of butting and pushing behaviour. However, among the acts received, only

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RESPONSETO MIXINGOF BULLSAND STEERS TABLE 2

Behavioural interactions during 4 h after mixing in three different male types of cattle Bchaviour and sex type ~

Acts exhibited

Acts received

Mean

SE

Mean rank Z2 ( d . f . = 2 )

50.25 19.88 16.50

17.93 8.78 14.55

2.38 2.00 1.63

63.38 16.75 1.75

18.09 8.17 1.08

2.94 1.94 1.13

15.63 56.00 23.63

4.90 20.42 17.40

1.81 2.75 1.44

8.75 12.13 5.13

2.57 3.10 3.29

2.06 2.25 1.69

Mounting VB EB S

15.63 55.63 15.13

8.03 21.89 4.54

1.88 2.38 1.75

12.63 49.00 18.50

6.65 16.05 5.38

1.69 2.38 1.94

50.88 27.50 18.13

27.37 10.12 8.38

1.88 2.38 1.75

10.50 7.63 3.75

2.77 2.08 1.75

2.50 2.19 1.31

X2

(d.f.=2)

1.75 NS

1.94 NS

7.31"

Pushing VB EB S

Mean rank

13.19"*

Butting VB EB S

SE

2.25 NS

Teasing VB EB S

Mean

1.75 NS

1.31 NS

6.06*

~VB, vasectomised bulls; EB, entire bulls; S, steers. Statistical significance of differences between male types were calculated by Friedman's test. NS, not significant; *P< 0.05 **P< 0.01.

pushing showed statistically significant differences ( P < 0 . 0 5 ) between the male types. If hyperactive animals are defined as those which showed more than 50 mountings in the 4-h observation period then we can identify four vasectomised bulls, two entire bulls and one steer as hyperactive. The homosexual behaviours exhibited by these seven animals accounted for 86% of the total homosexual encounters that occurred during the 4-h observation (all the groups added together). The remaining 14% of homosexual behaviours were distributed more or less equally over the remaining animals of all male types. The vasectomised bulls received 226 homosexual acts (mounting and teasing) and exhibited 195 retaliative aggressive acts (butting and pushing), while the entire bulls received 844 homosexual acts and exhibited 524 aggressive acts compared with 269 and 230, respectively, for steers. When the ratios of aggressive to homosexual behaviours were calculated (0.86, 0.86 and 0.62 for steers, vasectomised bulls and entire bulls, respectively), they showed that steers and vasectomised bulls retaliated more than the entire bulls. Observation revealed that the butting behaviour of entire bulls could be severe, ranging from a simple butt at the shoulder to butting at the flank and lifting of the hindquarters of the receiver off the floor. These observations tended to sug-

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gest that the aggressive behaviours of the entire bulls were more severe in force when compared with vasectomised bulls. DISCUSSION

In the present study male animals of different sex types were mixed together, thus it is difficult to make direct comparisons with the literature. General comparisons on the frequency of behaviours indicated that Group 2 showed a similar level of interactions to that reported among familiar groups of steers and bulls when re-penned (Kenny and Tarrant, 1987a,b ), and Groups 1 and 4, which were moderately active, showed interactions similar to mixed groups of cattle (Price and Tennessen, 1981; Kenny and Tarrant 1987a,b). The high number of interactions shown by Group 3 could be described as hyperactive. Mohan Raj (1988) suggested that an animal which in the preslaughter period showed more than 16 mounts, at a rate of five mounts per 15 min, would result in dark-cutting condition and suggested that the stress of being mounted and the physical response to escape a n d / o r retaliate had very little effect on the meat quality. The circling behaviour involved in the development of preferential expression of behaviours of mixed groups could well be a sign of hyperactivity and the animals involved could be separated to avoid the consequences. However, changes in the membership of established heifer groups have been reported to increase interactions (Hook et al., 1965 ), and therefore separation should not be achieved by forming new groups. By implication this would mean that the active groups in the lairage should slaughtered as soon as possible. Owing to the continued activity it could be suggested that there was no social rank formation even 4 h after mixing. This contrasts with the report by Bouissou ( 1981 ) who found that among heifers, 70% of the relationships were established within 10 min of regrouping and within 1 h almost all of them settled down with their rank order. This difference between heifers and male types is suggestive of sex differences in the rank formation. Although the homosexually hyperactive nature of vasectomised bulls has not been reported in the literature, Reinhardt et al. (1978) concluded that, in general, mounting was play behaviour in established groups of cattle, because it lacked motivation and because the roles were reversible. In this study the roles did not reverse except between one pair of animals and the severity of mounting was so intense, exhibited by crouching and grunting, that it was suggestive of a sexual motive. Hinch et al. (1982) suggested that frequent mounting immediately after regrouping, but decreasing thereafter, indicates that mounting may have an antagonistic as well as a sexual role among 10month-old bulls. Tennessen et al. ( 1985 ) reported that the rate of mounting and teasing was higher among bulls than steers, which is in accordance with this study. Cecim

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165

and Hausler (1988) reported that the mounting behaviour of androgenised detector heifers used in their study was based upon individual preferences rather than stage of oestrous cycle. This seemed to imply that mounting behaviour in heifers had a more antagonistic role for establishing dominance rather than being sexually motivated. This interpretation tends to suggest that the motive of mounting behaviour in cattle may be different between types (either in androgen-withdrawn males or administered females ), possibly owing to the androgens playing a role in the development of sexual behaviour through the central nervous system. However, mounting behaviour seems to play a major role in the development of hierarchy in a group. Pairing behaviour was found to be a characteristic of the homosexual bonding between the animals. Both sight and smell seemed to have been involved in the development of the relationship, as behaviours like sniffing of genitalia and hindquarters occurred between all the animals soon after mixing. Hafez and Bouissou (1975) reported that mounting which occurred in an established group as a non-agonistic or positive interaction, occurred in preferential directions between pairs of animals irrespective of their rank. Preferential directions in a mixed group of male cattle have been reported between similar genotypes but also depend on the phenotype (Jezierski et al., 1985). In the present study, such relationships developed between bulls rather than between bulls and steers which may suggest both antagonistic and sexual motives to establish dominance among the bulls. There is some indication that preferential relationships were made between strange animals rather than previous group members, which is contrary to the reports of Jezierski et al. (1985). Pushing occurred between the animals which were involved in homosexual interactions and it appeared to play a role in the preferential relationships that developed between bull types. The correlations between the homosexual and aggressive acts clearly indicate that aggression plays an integral role in the homosexual behaviour (Garlichs and Varner, 1985 ). Aggressive and sexual behaviour in males has been linked to the production of testosterone (Reece, 1990). The absence of testosterone in steers is likely to explain the lesser mounting and teasing in steers than bulls reported in the present study and by others (Tennessen et al., 1985 ), and also the reduction of sexual and aggressive behaviour following immunocastration (Robertson et al., 1982 ). In vasectomised animals testicular products accumulate in the tubular genitalia, therefore testosterone which would normally be excreted may be reabsorbed. The quantity of testosterone in serum is small in relation to daily production, therefore it is unlikely that this could account for the increased homosexual behaviours shown by vasectomised bulls. In addition bulls testes can release testosterone rapidly (Lindner, 1961 ) but in limited quantities which are metabolized rapidly (Weatherbee and Lodge, 1976), hence the effect of the hormone may be transient. Agarwal et al. (1985) reported that entire and vasectomised buffaloes had similar pre-exercise serum

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testosterone levels and exercise reduced testosterone levels in both types. The serum testosterone levels recovered to pre-exercise levels faster in vasectomised buffaloes than entire buffaloes and the authors (Agarwal et al., 1985) suggested that this may be related to corticosteroid function following stress. Administration of corticosteroids has been shown to reduce plasma testosterone levels in cattle (Thibier and Rolland, 1976 ) and in rats (Doerr and Pirke, 1978 ). In the present study the mixing of the animals may be considered as both stress and exercise (resulting from mounting), and thus the greater sexual and aggressive activity of the vasectomised animals may represent different responses in the pituitary/adrenal function and testosterone. It is difficult to hypothesise further, particularly as pituitary/adrenal response depends on social rank or dominance (Papova and Naumenko, 1972). Sex differences in both pituitary/adrenal function (Grey, 1971 ) and thyroid function (Moss, 1980) have been reported. Jezierski et al. (1985) found that bulls with typical male body conformation initiated fewer and received more mounts, and initiated and received more butts. There were no obvious differences in body conformation between the entire and vasectomised bulls in the present study, although body conformation may be a contributory factor to the differences in behaviour observed. Vasectomised bulls showed a more overt teasing in the form of twitching of tail and shaking of head during their approach. In contrast the only hyperactive steer in this study mounted directly without exhibiting teasing. However, this may not be characteristic of steers as a previous investigation showed that teasing is a c o m m o n behaviour in mixed groups of steers which were laired overnight prior to slaughter (Mohan Raj, 1988 ). The teasing behaviour of cattle which occurred as sexual foreplay, included a range of actions such as licking and chin resting on the hindquarters, and attempted mounting (without lifting fore-legs). Although this would involve muscular exertion it is difficult to assess the effect of teasing alone on the meat quality. However, the sexual arousal associated with teasing could lead to changes in the physiology of the animal, particularly stimulation of catecholamine-mediated metabolic pathways, which would affect meat quality. Franc et al. (1987) considered sniffing and licking as non-agonistic social behaviour and reported a correlation of 0.68 (P < 0.01 ) between these behaviours and the ultimate pH of muscle longissimus dorsi. Similar correlations were found during investigation of meat quality in the sex types in the present study (Mohan Raj, 1988). CONCLUSION

It is concluded that behavioural interactions between members of a mixed group depend upon the temperament of individual animals. The vasectomised bulls were homosexually more active when compared with entire bulls or

R E S P O N S E T O M I X I N G O F BULLS A N D STEERS

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steers. The entire bulls showed more aggressive behaviours than the vasectomised bulls and steers, suggesting that vasectomy reduced aggression. Mounting as a behavioural component of a mixed group of cattle has both an antagonistic as well as a sexual role. There were indications of possible sex differences in the motive of mounting. However, when homosexual behaviour occurred between unfamiliar cattle, irrespective of male types, there was preferential unidirectional expression. Aggressive behaviours occurred as retaliative acts. Although teasing and mounting were exhibited by both entire bulls and vasectomised bulls, the vasectomised bulls showed greater intensity, which would be detrimental to meat quality. Further investigation is warranted to explain the reason (s) for the hyperactive nature of vasectomised bulls and to assess the importance of the integral role of mounting in the development of social bonding between the individuals of a group. ACKNOWLEDGEMENTS

Thanks are due to G. Kirkpatrick and R. Caldwell for their technical assistance and staff at the Experimental Husbandry Farm, Loughgall for assistance in the handling of animals. The first author was in receipt of a Visiting Studentship awarded by the Queen's University of Belfast.

REFERENCES Agarwal, S.P., Agarwal, V.K., Narinder Singh and Dwarknath, P.K., 1985. Effect of stress of exercise on serum testosterone levels in buffalo males. Indian J. Dairy. Sci. 38: 1-3. Baker, A.M. and Gonyou, H.W., 1985. Effects of Compudose implants on the sexual, agonistic and handling behaviours of feedlot bulls. J. Anim. Sci., 61 (Suppl. 1 ), Abstract 13, p. 210. Bouissou, M.F., 1981. Behaviour of domestic cattle under modern management techniques. In: D.E. Hood and P.V. Tarrant (Editors), The Problem of Dark-cutting in Beef. Curr. Top. Vet. Med. Anim. Sci., Vol. 10, Martinus Nijhoff, The Hague, pp. 141-164. Cecim, M. da S. and Hausler, C.L., 1988. Social preferences affect mounting activity in dairy heifers. J. Anim. Sci. 66 (Suppl. 1 ), Abstract 37, p. 231. Doerr, P. and Pirke, K.M., 1976. Cortisol induced suppression of plasma testosterone in normal adult males. J. Clin. Endocrinol. Metab., 43: 622-629. Fabiansson, S., Erichsen, I. and Laser Reutersward, A., 1984. The incidence of dark-cutting beef in Sweden. Meat Sci., 10: 21-33. Franc, C., Bartos, L., Hanys, Z. and Tomes, Z., 1987. Pre-slaughter social activity of young bulls relating to the occurrence of dark-cutting beef. Anim. Prod., 46 (2): 153-161. Garlichs, S.C. and Varner, M.A., 1985. Frequency of aggressive behaviour compared to mounting in dairy cows. J. Anim. Sci., 61: (Suppl. 1 ), Abstract 13, p. 212. Grey, J., 1971. The route from gene to behaviour: sex differences and fear. In: J. Grey (Editor), The Psychology of Fear and Stress. Weidenfeld and Nicolson, London. pp. 83-96. Hafez, E.S.E. and Bouissou, M.F., 1975. Behaviour of cattle. In: E.S.E. Hafez (Editor), The Behaviour of Domestic Animals. Baillere Tindall, London, 3rd edn., pp. 203-245. Hinch, G.N., Lynch, J.J. and Thwaites, C.J., 1982. Patterns and frequency of social interactions in young grazing bulls and steers. Appl. Anita. Ethol., 9:15-30.

168

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Hook, S.L., Donaldson, S.L. and Albright, J.L., 1965. A study of social dominance behaviour in young cattle. Am. Zool., 5, Abstract no. 425, p. 714. Jezierski, T.A., Kogiorowski, M., Goszczynski, J. and Sieradyka, I., 1985. Homosexual and social behaviours of young bulls of different geno- and phenotypes and plasma concentrations of some hormones. Appl. Anita. Behav. Sci., 24:101- l 13. Kenny, F.J. and Tarrant, P.V., 1984. Meat quality in beef heifers slaughtered at oestrus. Proceedings of the 30th European Meeting of Meat Research Workers, Bristol, University of Bristol, pp. 99-100. Kenny, F.J. and Tarrant, P.V., 1987a. The reaction of young bulls to short-haul road transport. Appl. Anim. Behav. Sci., 17: 209-227. Kenny, F.J. and Tarrant, P.V., 1987b. The physiological and behavioural responses of crossbred friesian steers to short-haul transport by road. Livest. Prod. Sci., 17: 63-75. Lindner, H.R., 1961. Androgens and related compounds in the spermatic vein blood of domestic animals. Neutral steroids secreted by the bull testes. J. Endocrinol. 23:139-159. McCaughey, J.W. and Martin, J.B., 1980. Preparation and use of teaser bulls, Vet. Rec., 106: 119-121. McGlone, J.J., 1985. Role of the submaxillary salivary gland and 5a-androst-16-en-3-one in modulation of swine aggression and dominance. J. Anim. Sci., 61: (Suppl. 1 ), Abstract no. 1, p. 207. McVeigh, J.M., Tarrant, P.V. and Harrington, M.G., 1982. Behavioural stress and skeletal muscle glycogen metabolism in young bulls. J. Anim. Sci., 54: 790-795. Mohan Raj, A.B., 1988. Biochemical, physiological and behavioural parameters as determinants of meat quality. Ph.D. Thesis, Queen's University of Belfast. Mohan Raj, A.B., Moss, B.W., McCaughey, W.J., McLauchlan, W., McCauchey, S.J. and Kennedy, S., 1991. Effect of surgical and immunocastration of beef cattle on meat colour, postmortem glycolytic metabolites and fibre type distribution. J. Sci. Food. Agric., 54:111-126. Moss, B.W., 1980. The development of a blood profile for stress assessment. In: W. Sybesma (Editor), Welfare of Pigs. Martinus Nij hoff, The Hague, pp. 112-131. Papovra, N.K. and Naumenko, E.V., 1972. Dominance relations and the pituitary adrenal systems in rats. Anim. Behav., 29:108-111. Price, M.A. and Tennessen, T., 1981. Pre-slaughter management of dark-cutting in the carcasses of young bulls. Can. J. Anim. Sci., 61: 205-208. Reece, W.O., 1990. Physiology of Domestic Animals. Lea and Febiger, London (see pp. 282283). Reinhardt, V., Mutiso, F.M. and Reinhardt, A., 1978. Social behaviour and social relationships between female and male prepubertal bovine calves. Appl. Anita. Ethol., 4: 43-54. Robertson, I.S., Frazer, H.M., Innes, G.M. and Jones, A.S., 1982. Effect of immunological castration on sexual and production characteristics in male cattle. Vet. Rec., 111: 529-531. Tennessen, T., Price, M.A. and Berg, R.T., 1985. The social interactions of young bulls and steers after re-grouping. Appl. Anim. Behav. Sci., 14: 37-47. Thiebier, M. and Rolland, O., 1976. The effect of Dexamethasone (DXM) on circulating testosterone and luteinizing hormone (LH) in young post-pubertal bulls. Theriogenology, 5: 53-60. Weatherbee, P.S. and Lodge, J.R., 1976. Serum testosterone and oestrogen concentration in the Holstein Friesian bull after successive ejaculations. Am. J. Vet. Res., 37: 465-467.