Responsiveness, behavioural arousal and awareness in fetal and newborn lambs: Experimental, practical and therapeutic implications

New Zealand Veterinary Journal

Volumn 51, Issue 1, 2003, Pages 2-13

  Mellor, D J ^a   Gregory, N G ^b  

^a MASSEY UNIVERSITY   (New Zealand)

^b SOUTH AUSTRALIAN RESEARCH AND DEVELOPMENT INSTITUTE   (Australia)

Author keywords

Animal welfare; Arousal; Awareness; Behaviour; Birth changes; Fetal blood (serum) collection; Fetal surgery; Fetotomy; Fetus; Newborn; Pain; Slaughter

Indexed keywords

ANIMAL BEHAVIOR; ANIMAL WELFARE; AROUSAL; AWARENESS; BLOOD SAMPLING; BRAIN FUNCTION; BRAIN STEM; BREATHING; COLD EXPOSURE; DELIVERY; ESTROGEN BLOOD LEVEL; FETUS CIRCULATION; LAMB; NOCICEPTION; NONHUMAN; OXYGEN BLOOD LEVEL; OXYGENATION; PREGNANCY; PROGESTERONE BLOOD LEVEL; REVIEW; STIMULATION; UTERUS; VETERINARY MEDICINE;

ANIMALIA; LAMB; OVIS ARIES;

EID: 0037300657     PISSN: 00480169     EISSN: 11760710     Source Type: Journal    
DOI: 10.1080/00480169.2003.36323     Document Type: Article

References (130)

1. Adamson SL, Richardson BS, Homan J. Initiation of pulmonary gas exchange by fetal sheep in utero. Journal of Applied Physiology 62, 989-98, 1987
2. Adamson SL, Kuipers IM, Olson DM. Umbilical cord occlusion stimulates breathing independent of blood gases and pH. Journal of Applied Physiology 70, 1796-1809, 1991
3. Akerstedt T, Hume K, Minors D, Waterhouse J. Experimental separation of time of day and homeostatic influences on sleep. American Journal of Physiology: Regulation, Integrative and Comparative Physiology 274, R1162-8, 1998
4. Alexander G. Husbandry practices in relation to maternal and offspring behaviour. In: Wodzicka-Tomaszewska M, Edey TN, Lynch JJ (eds). Behaviour - Reviews in Rural Science, Behaviour in Relation to Reproduction, Management and Welfare of Farm Animals. Vol. 4. Pp 99-107. University of New England Press, Armidale, 1980
5. Alvaro R, de Almeida V, Al-Alaiyan S, Robertson M, Nowacsyk B, Cates D, Rigatto H. A placental extract inhibits breathing induced by umbilical cord occlusion in fetal sheep. Journal of Developmental Physiology 19, 23-8, 1993
6. Baars BJ. There are no known differences in brain mechanisms of consciousness between humans and other mammals. Animal Welfare 10, S31-40, 2001
7. Baier RJ, Hasan SU, Cates DB, Hooper B, Nowaczyk B, Rigatto H. Effects of various concentrations of O2 and umbilical cord occlusion on fetal breathing and behavior. Journal of Applied Physiology 68, 1597-1604, 1990
8. Barcroft J, Barron DH. Movements in midfoetal life in the sheep embryo. Journal of Physiology 91, 329-51, 1937
9. Barcroft J, Barron DH. The development of behaviour in foetal sheep. Journal of Comparative Neurology 70, 477-502, 1939
10. Barcroft J, Kennedy JA, Mason MF. Oxygen in the blood of the umbilical vessels of sheep. Journal of Physiology 97, 347-56, 1940
11. Barlow RM. The fetal sheep: morphogenesis of the nervous system and histochemical aspects of myelination. Journal of Comparative Pathology 135, 249-62, 1969
12. Barron DH, Meschia G. The carbon dioxide gradient between the foetal and maternal bloods of sheep and goats. Yale Journal of Biology and Medicine 29, 480-95,1957
13. Bassett JM, Oxborrow TJ, Smith ID, Thorburn GD. The concentration of progesterone in the peripheral plasma of the pregnant ewe. Journal of Endocrinology 45, 449-57, 1969
14. Berger PJ, Walker AM, Horne R, Brodecky V, Wilkinson MH, Wilson F, Maloney JE. Phasic respiratory activity in the fetal lamb during late gestation and labour. Respiratory Physiology 65, 55-68, 1986
15. Berger PJ, Horne RSC, Soust M, Walker AM, Maloney JE. Breathing at birth and the associated blood gas and pH changes in the lamb. Respiratory Physiology 82, 251-66, 1990
16. Berger PJ, Kyriakides MA, Cooke IRC. Supraspinal influence on the development of motor behavior in the fetal lamb. Journal of Neurobiology 33, 276-88, 1997
17. Bernhard CG, Meyerson BA. Morphological and physiological aspects of the development of recipient functions in the cerebral cortex. In: Comline RS, Cross KW, Dawes GS, Nathanielsz PW (eds). Fetal and Neonatal Physiology. Pp 1-19. Cambridge University Press, Cambridge, 1973
18. Bocking AD, Harding R. Effects of reduced uterine blood flow on electrocortical activity, breathing, and skeletal muscle activity in fetal sheep. American Journal of Obstetrics and Gynecology 154, 655-62, 1986
19. Bocking AD, Gagnon R, Milne KM, White SE. Behavioural activity during prolonged hypoxemia in fetal sheep. Journal of Applied Physiology 65, 2420-6, 1988
20. Boddy K, Dawes GS, Fisher R, Pinter S, Robinson JS. Foetal respiratory movements, electrocortical and cardiovascular responses to hypoxaemia and hypercapnia in sheep. Journal of Physiology 243, 599-618, 1974
21. Brierly JB, Prior DF, Calverly J, Jackson SJ, Brown AW The pathogenesis of ischaemic neuronal damage along the cerebral arterial boundary zone in Papio anubis. Brain 103, 929-45, 1980
22. Challis JRG, Patrick JE. Fetal and maternal oestrogen concentrations throughout pregnancy in sheep. Canadian Journal of Physiology and Pharmacology 59, 970-8, 1981
23. Clapp JF, Peress NS, Wesley M, Mann LI. Brain damage after intermittent partial cord occlusion in the chronically instrumented fetal lamb. American Journal of Obstetrics and Gynecology 159, 504-9, 1988
24. Clewlow F, Dawes GS, Johnston BM, Walker DW. Changes in breathing, electrocortical and muscle activity in the unanaesthetized fetal lamb with age. Journal of Physiology 341, 463-76, 1983
25. Comline RS, Silver M. Daily changes in foetal and maternal blood of conscious pregnant ewes with catheters in umbilical and uterine vessels. Journal of Physiology 209, 567-86, 1970
26. Comline RS, Silver M. The composition of foetal and maternal blood during parturition in the ewe. Journal of Physiology 222, 233-56, 1972
27. Cook CJ, Gluckman PD, Johnston BM, Williams C. The development of the somatosensory evoked potentials in the unanaesthetised fetal sheep. Journal of Developmental Physiology 307, 335-53, 1987
28. Crenshaw MC, Meschia G, Barron, DH. Role of progesterone in inhibition of muscle tone and respiratory rhythm in foetal lambs. Nature 212, 842, 1966
29. Crossley KJ, Nicol MB, Hurst JJ, Walker DW Thorburn GD. Suppression of arousal by progesterone in fetal sheep. Reproduction Fertility and Development 9, 767-73, 1997
30. Dawes GS. The 1987 James A.F. Stevenson Memorial Lecture. The development of fetal behavioural patterns. Canadian Journal of Physiology and Pharmacology 66, 541-8, 1988
31. Dawes GS, Fox HE, Leduc BM, Liggins GC, Richards RT. Respiratory movements and rapid eye movement sleep in the foetal lamb. Journal of Physiology 220, 119-43, 1972a
32. Dawes GS, Fox HE, Richards RT. Variations in asphyxial gasping with age in lambs and guinea-pigs. Quarterly Journal of Experimental Physiology 57, 131-8, 1972b
33. de Haan HH, Gunn AJ, Gluckman PD. Experiments in perinatal medicine: what have we learnt? Prenatal and Neonatal Medicine 1, 16-25, 1996
34. Dolling M, Seamark RF. Progesterone metabolites in fetal sheep plasma: the effect of nephrectomy. Journal of Developmental Physiology 1, 399-413, 1979
35. Dufty JH, Sloss V. Anoxia in the bovine foetus. Australian Veterinary Journal 53, 262-7, 1977
36. Eales FA, Small J. Summit metabolism in newborn lambs. Research in Veterinary Science 29, 211-8, 1980
37. Eales FA, Small J. Effects of acute hypoxia on heat production capacity and summit metabolism in newborn lambs. Research in Veterinary Science 39, 212-5, 1985
38. Eales FA, Small J. Practical Lambing and Lamb Care - a Veterinary Guide. 2nd Edtn. Longman Group Ltd, Harlow, 1995
39. Eisele JH, Eger EI, Muallem M. Narcotic properties of carbon dioxide in the dog. Anesthesiology 28, 856-65, 1967
40. Empson J. Sleep and Dreaming. 2nd Edtn. Pp 22-39. Harvester Wheatsheaf, New York, 1993
41. Endo T, Roth C, Landolt H-P, Werth E, Aeschbach D, Achermann P, Borbely AA. Selective REM sleep deprivation in humans: effects on sleep and sleep EEG. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology 274, R1186-94, 1998
42. Fewell JE, Konduri GG. Repeated exposure to rapidly developing hypoxemia influences the interaction between oxygen and carbon dioxide in initiating arousal from sleep in lambs. Pediatric Research 24, 28-33, 1988
43. Fewell JE, Konduri GG. Influence of repeated exposure to rapidly developing hypoxaemia on the arousal and cardiopulmonary response to developing hypoxaemia in lambs. Journal of Developmental Physiology 11, 77-82, 1989
44. Fitzgerald M. Development of somatosensory function. In: Gluckman PD, Heyman MA (eds). Pediatrics and Perinatology. 2nd Edtn. Pp 379-82. Arnold (Hodder Headline Group), Auckland, 1996
45. Fitzgerald M. Development and neurobiology of pain. In: Wall PD, Melzack R (eds). Textbook of Pain. 4th Edtn. Pp 235-51. Churchill Livingstone, Edinburgh, 1999
46. Fraser AF. The phenomenon of pandiculation in the kinetic behaviour of the sheep fetus. Applied Animal Behaviour Science 24, 169-82, 1989
47. Fraser AF, Broom DM. Farm Animal Behaviour and Welfare. Pp 198-207, 227-38, 247-55. Beilliere Tindall, London, 1990
48. Gluckman PD, Gunn TR, Johnston BM. The effect of cooling on breathing and shivering in unanaesthetised fetal lambs in utero. Journal of Physiology 343, 495-506, 1983
49. Gluckman PD, Gunn TR, Johnston BM, Quinn JP. Manipulation of the temperature of the fetal lamb in utero. In: Nathanielsz PW (ed). Animal Models in Fetal Medicine IV. Pp 37-56. Perinatology Press, Ithaca, New York, 1984
50. Gluckman PD, Johnston BM, Nathanielsz PW. Advances in fetal physiology: reviews in honour of G.C. Liggins. Advances in Perinatal Medicine 7. Pp 1-420. Perinatology Press, Ithaca, New York, 1989
51. Gregory NG, Wilkins LJ. Effect of cardiac arrest on susceptibility to carcass bruising in sheep. Journal of Science of Food and Agriculture 35, 671-6, 1984
52. Gregory NG, Wotton SB. Sheep slaughtering procedures. II. Time to loss of brain responsiveness after exsanguination or cardiac arrest. British Veterinary Journal 140, 354-60, 1984
53. Gunn TR, Johnston BM, Iwamoto HS, Fraser M, Nicholls MG, Gluckman PD. Haemodynamic and catecholamine responses to hypothermia in the fetal sheep in utero. Journal of Developmental Physiology 7, 241-9, 1985
54. Gunn TR, Butler J, Gluckman PD. Metabolic and hormonal responses to cooling the fetal sheep in utero. Journal of Developmental Physiology 8, 55-66, 1986
55. Gunn TR, Ball KT, Gluckman PD. Reversible umbilical cord occlusion: Effects on thermogenesis in utero. Pediatric Research 30, 513-7, 1991
56. Gunn AJ, Parer JT, Mallard EC, Williams CE, Gluckman PD. Cerebral histologic and electrocorticographic changes after asphyxia in fetal sheep. Pediatric Research 31, 486-91, 1992
57. Gunn AJ, Gluckman PD, Gunn TR. Selective head cooling in newborn infants after perinatal asphyxia: a safety study. Pediatrics 102, 885-902, 1998
58. Harding R, Poore ER, Cohen GL. The effect of brief episodes of diminished uterine blood flow on breathing movements, sleep states and heart rate in fetal sheep. Journal of Developmental Physiology 3, 231-43, 1981
59. Harding JE, Jones CT, Robinson JS. Studies on experimental growth retardation in sheep. The effects of a small placenta in restricting transport to and growth of the fetus. Journal of Developmental Physiology 7, 427-42, 1985
60. Hart R, Mackay JMK, McVittie CR, Mellor DJ. A technique for the derivation of lambs by hysterectomy. British Veterinary Journal 127, 419-24, 1971
61. Hasan SU, Rigaux A. The effects of lung distension, oxygenation, and gestational age on fetal behavior and breathing movements in sheep. Pediatric Research 30, 193-201, 1991
62. Hattingh J, Cornelius ST, Ganhao MF, Fonseca F. Arterial blood gas composition, consciousness and death in rabbits. Journal of the South African Veterinary Association 57, 13-16, 1986
63. Hirst JJ, Egodagamage KC, Walker DW. Effect of neuroactive steroid infused into the cerebral ventricles of fetal sheep in utero using small infusion volumes. Journal of Neuroscience Methods 97, 37-44, 2000
64. Horne RSC, Berger PJ, Bowes G, Walker AM. Effect of sinoaortic denervation on arousal responses to hypotension in newborn lambs. American Journal of Physiology 256, H434-40, 1989
65. Jansen AH, Ioffe S, Russell BJ, Chernick V. Influence of sleep state on the response to hypercapnia in fetal lambs. Respiratory Physiology 48, 125-42, 1982
66. Jensen A, Hohmann M, Kunzel W. Dynamic changes in organ blood flow and oxygen consumption during acute asphyxia in fetal sheep. Journal of Developmental Physiology 9, 41-55, 1987
67. Jensen A, Roman Ch, Rudolph AM. Effect of reducing uterine blood flow on fetal blood flow distribution and oxygen delivery. Journal of Developmental Physiology 15, 309-23, 1991
68. Jochems, CEA, ven der Valk JBF, Stafleu FR and Baumans V. The use of fetal bovine serum: ethical or scientific problem? Alternatives to Laboratory Animals 30, 219-27, 2002
69. Johnston RV, Grant DA, Wilkinson MH, Walker AM. Repetitive hypoxia depresses arousal from active sleep in newborn lambs. Journal of Physiology 510, 651-9, 1998
70. Jones CT. The development of some metabolic responses to hypoxia in the foetal sheep. Journal of Physiology 265, 743-62, 1977
71. Jones CT, Boddy K, Robinson JS, Ratcliffe JG. Developmental changes in the responses of the adrenal glands of foetal sheep to endogenous adrenocorticotrophin, as indicated by hormone responses to hypoxaemia. Journal of Endocrinology 72, 279-92, 1977
72. Kent JE, Molony V, Graham MJ. Comparison of methods for the reduction of acute pain produced by rubber ring castration or tail docking of week-old lambs. Veterinary Journal 155, 39-51, 1998
73. King KJ, McCullagh P. Splenectomy of the fetal lamb early in development as a model of congenital asplenia. Australian and New Zealand Journal of Surgery 71, 41-5, 2001
74. Kirkwood JK, Hubrecht RC, Wickens S, O’Leary H, Oakeley S. Consciousness, cognition and animal welfare. Animal Welfare 10 (Supplement), S1-251, 2001
75. Ladds PW Summers PM, Humphrey JD. Pregnancy in slaughtered cows in north-eastern Australia. Australian Veterinary Journal 51, 472-7, 1975
76. Landolt H-P, Raimo EB, Schierow BJ, Kelsoe JR, Rapaport MH, Gillin JC. Sleep and sleep electroencephalogram in depressed patients treated with phenelzine. Archives of General Psychiatry 58, 268-76, 2001
77. Lehman H. Animal awareness. Applied Animal Behaviour Science 57, 315-25, 1998
78. Liggins GC, Faircough RT, Grieves SA, Kendall JZ, Knox BS. The mechanism of initiation of parturition in the ewe. Recent Progress in Hormone Research 29, 111-59, 1973
79. Lynch JJ, Hinch GN, Adams DB. The behaviour of the lamb. The Behaviour of Sheep: Biological Principles and Implications for Production. Pp 153-77. CSIRO, Melbourne, Australia, 1992
80. Mallard EC, Gunn AJ, Williams CE, Johnston BM, Gluckman PD. Transient umbilical cord occlusion causes hippocampal damage in the fetal sheep. American Journal of Obstetrics and Gynecology 167, 1423-30, 1992
81. Mann LI, Prichard JW, Symmes D. EEG, ECG, and acid-base observations during acute fetal hypoxia. American Journal of Obstetrics and Gynecology 106, 39-51, 1970
82. Mattsson JL, Stinson JM, Clark CS. Electroencephalographic power-spectral changes coincident with onset of carbon dioxide narcosis in rhesus monkey. American Journal of Veterinary Research 33, 2043-9, 1972
83. Mellor DJ. Vascular anastomosis and fusion of foetal membranes in multiple pregnancy in sheep. Research in Veterinary Science 10, 361-7, 1969
84. Mellor DJ. Investigations of the fluid spaces of the sheep conceptus. In: Nathanielsz PW (ed). Animal Models in Fetal Medicine I. Pp 59-106. Elsevier, Amsterdam, 1980
85. Mellor DJ. Nutritional and placental determinants of fetal growth rate in sheep and consequences for the newborn lamb. British Veterinary Journal 139, 307-24, 1983
86. Mellor DJ. Investigations of fetal growth in sheep. In: Nathanielsz PW (ed). Animal Models in Fetal Medicine IV. Pp 149-73. Perinatology Press, Ithaca, New York, 1984
87. Mellor DJ. Feeding pregnant ewes and newborn lambs during experiment. In: Nathanielsz PW (ed). Animal Models in Fetal Medicine VI. Pp 55-92. Perinatology Press, Ithaca, New York, 1987
88. Mellor DJ. Integration of perinatal events, pathophysiological changes and consequences for the newborn lamb. British Veterinary Journal 144, 552-69, 1988
89. Mellor DJ, Cockburn F. A comparison of energy metabolism in the newborn infant, piglet and lamb. Quarterly Journal of Experimental Physiology 71, 361-79, 1986
90. Mellor DJ, Murray L. Effects of tail docking and castration on behaviour and plasma cortisol concentrations in young lambs. Research in Veterinary Science 46, 387-91, 1989
91. Mellor DJ, Pearson RA. Some changes in the composition of blood during the first 24 hours after birth in normal and growth retarded lambs. Annales de Recherches Vétérinaires 8, 460-7, 1977
92. Mellor DJ, Slater JS. Daily changes in amniotic and allantoic fluid during the last three months of pregnancy in conscious, unstressed ewes with catheters in their foetal fluid sacs. Journal of Physiology 217, 573-604, 1971
93. Mellor DJ, Mackay JMK, Williams JT. Effects of oestrogen on activity and survival of lambs delivered by hysterectomy. Research in Veterinary Science 13, 399-401, 1972
94. Meschia G, Hellegers A, Blechner JN, Wolkoff AS, Barron DH. A comparison of the oxygen dissociation curves of the bloods of maternal, foetal and newborn sheep at various pHs. Quarterly Journal of Experimental Physiology 46, 95-100, 1961
95. Meschia G, Cotter JR, Breathnach CS, Barron DH. The haemoglobin, oxygen, carbon dioxide and hydrogen ion concentrations in the umbilical bloods of sheep and goats as sampled via plastic indwelling catheters. Quarterly Journal of Experimental Physiology 50, 185-95, 1965
96. Mohan Raj AB, Wrtton SB, Gregory NG. Changes in the somatosensory evoked potentials and spontaneous electroencephalogram of hens during stunning with a carbon dioxide and argon mixture. British Veterinary Journal 148,147-56, 1992
97. Mott JC. Ability of young animals to withstand total oxygen lack. British Medical Bulletin 17, 144-8, 1961
98. Newhook JC, Blackmore DK. Elecetroencephalographic studies of stunning and slaughter of sheep and calves: Part 1 - The onset of permanent insensibility in sheep during slaughter. Meat Science 6, 221-33, 1982
99. Nicol MB, Hurst JJ, Walker DW, Thorburn GD. Effect of alteration of maternal plasma progesterone concentrations on fetal behavioural state during late gestation. Journal of Endocrinology 152, 379-86, 1997
100. Nicol MB, Hurst JJ, Walker DW Effect of pregnane steroids on electrocortical activity and somatosensory evoked potentials in fetal sheep. Neuroscience Letters 253, 111-4, 1998
101. Nitsos I, Rees S. Development of immunoreactivity for calcitonin gene-related peptide, substance P and glutamate in primary sensory neurons, and for serotonin in the spinal cord of fetal sheep. Neuroscience 54, 239-52, 1993
102. [125]I rat-a-CGRP binding sites in the spinal cord of sheep: a prenatal and postnatal study. Neuroscience 62, 257-64,1994
103. Pallis C. Reappraising death. British Medical Journal 285, 1409-12, 1982
104. Paul SM, Purdy RH. Neuroactive steroids. Federation of American Society of Experimental Biology Journal 6, 2311-22, 1992
105. Pearson RA, Mellor DJ. Some physiological changes in pregnant sheep and goats before, during and after surgical insertion of uterine catheters. Research in Veterinary Science 19, 102-4, 1975
106. Persson HE. Functional development in the somatosensory cortex of foetal sheep. In: Comline RS, Cross KW, Dawes GS, Nathanielsz PW (eds). Fetal and Neonatal Physiology. Pp 20-7. Cambridge University Press, Cambridge, 1973
107. Piggins D, Phillips CJC. Awareness in domesticated animals - concepts and definitions. Applied Animal Behaviour Science 57, 181-200, 1998
108. Pinheiro Machado FLC, Hurnik JF, Burton JH. The effect of amniotic fluid ingestion on the nociception of cows. Physiology and Behavior 62, 1339-44, 1997
109. Power SGA, Patrick JE, Carson GD, Challis JRG. The fetal membranes as a possible source of progesterone in the amniotic and allantoic fluids of pregnant sheep. Endocrinology 110, 481-6, 1982
110. Rees S, Rawson J, Nitsos I, Brumley C. The structural and functional development of muscle spindles and their connections in fetal sheep. Brain Research 642, 185-98, 1994a
111. Rees S, Nitsos I, Rawson J. The development of cutaneous afferent pathways in fetal sheep: a structural and functional study. Brain Research 661, 207-22, 1994b
112. Richardson BS, Carmichael L, Homan J, Patrick JE. Electrocortical activity, electroocular activity, and breathing movements in fetal sheep with prolonged and graded hypoxemia. American Journal of Obstetrics and Gynecology 167, 553-8, 1992
113. Richardson BS, Carmichael L, Homan J, Johnston L, Gagnon R. Fetal cerebral, circulatory, and metabolic responses during heart rate decelerations with umbilical cord compression. American Journal of Obstetrics and Gynecology 175, 929-36, 1996
114. Rigatto H, Blanco CE, Walker DW The response to stimulation of hindlimb nerves in fetal sheep, in utero, during the different phases of electrocortical activity. Journal of Developmental Physiology 4, 175-85, 1982
115. Rigatto H, Lee D, Davi M, Moore M, Rigatto E, Cates D. Effect of increased arterial CO2 on fetal breathing and behaviour in sheep. Journal of Applied Physiology 64, 982-7, 1988
116. Robinson JS, Kingston EJ, Jones CT, Thorburn GD. Studies on experimental growth retardation in sheep. The effect of removal of endometrial caruncles on fetal size and metabolism. Journal of Developmental Physiology 1, 379-98, 1979
117. Robinson JS, Jones CT, Kingston EJ. Studies on experimental growth retardation in sheep. The effects of maternal hypoxaemia. Journal of Developmental Physiology 5, 89-100, 1983
118. Ruckebusch Y, Gaujoux M, Eghbali B. Sleep cycles and kinesis in the fetal lamb. Electroencephalographic and Clinical Neurophysiology 42, 226-37, 1977
119. Rudolph AM. The fetal circulation and its response to stress. Journal of Developmental Physiology 6, 11-19, 1984
120. Rudolph AM, Itskovitz J, Iwamoto H, Reuss ML, Heymann M. Fetal cardiovascular responses to stress. Seminars in Perinatology 5, 109-21, 1981
121. Seamark RF, Nancarrow CD, Gardner J. Progesterone metabolism in ovine fetal blood: the formation of 3a-hydroxy-pregn-4-en-20-one and other substances. Steroids 15, 589-603, 1970
122. Sieker HO, Hickam JB. Carbon dioxide intoxication: the clinical syndrome, its etiology and management with particular reference to the use of mechanical respirators. Medicine 35, 389-423, 1956
123. Silver M, Steven BH, Comline RS. Placental exchange and morphology in ruminants and mare. In: Comline RS, Cross KW, Dawes GS, Nathanielsz PW (eds). Fetal and Neonatal Physiology. Pp 245-71. Cambridge University Press, Cambridge, 1973
124. Slee J, Springbett A. Early postnatal behaviour in lambs of ten breeds. Applied Animal Behaviour Science 15, 229-40, 1986
125. Sommerville BA, Broom DM. Olfactory awareness. Applied Animal Behaviour Science 57, 269-86, 1998
126. Thorburn GD, Challis JRG. Endocrine control of parturition. Physiological Reviews 59, 877-88, 1979
127. Tyler H, Ramsey H. Hypoxia in neonatal calves: effect on selected metabolic parameters. Journal of Dairy Science 74, 1957-62, 1991
128. 3H-diazapam binding. Paediatric Pharmacology 2, 179-87, 1982
129. Walker AM, Carroll J, de Preu ND, Horne RSC. Modification of arousal responses following hypoxia in newborn lambs. In: Walker AM, McMillan C, National SIDS Council (eds). Second SIDS International Conference and First SIDS Global Strategy Meeting. Pp 238-42. Perinatology Press, New York, 1993
130. West JB, Hackett PH, Maret KH, Milledge JS, Peters RM, Pizzo CJ, Winslow RM. Pulmonary gas exchange on the summit of Mt. Everest. Journal of Applied Physiology 55, 678-87, 1984