Seasonal changes of metabolism and appetite in Soay rams

Relationships between photoperiod and cycles of voluntary food intake (VFI) and maintenance energy requirements (MER) were determined in Soay rams, subjected to a 6-month photoperiodic regime. Food was offered ad libitum (no. = 5) or at a predicted maintenance level (no. = 5). All rams demonstrated...

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Bibliographic Details
Published inAnimal science (Penicuik, Scotland) Vol. 69; pp. 191 - 202
Main Authors Argo, C.M, Smith, J.S, Kay, R.N.B
Format Journal Article
LanguageEnglish
Published 01.08.1999
Subjects
ad libitum feeding
appetite
blood plasma
body weight
energy balance
energy cost of maintenance
energy intake
energy retention
heat production
length
photoperiod
prolactin
rams
restricted feeding
seasonal variation
sexual development
sexual flush
testes
testosterone
thyroxine
voluntary intake
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Summary:Relationships between photoperiod and cycles of voluntary food intake (VFI) and maintenance energy requirements (MER) were determined in Soay rams, subjected to a 6-month photoperiodic regime. Food was offered ad libitum (no. = 5) or at a predicted maintenance level (no. = 5). All rams demonstrated 6-month cycles of VFI, growth and reproductive status. Metabolizable energy intake (MEI) was greatest in rams given food ad libitum (666 (s.e. 21.7) kJ/kg metabolic live weight (M(0.75)) and food-restricted (528 (s.e. 12.2) kJ/kg M(0.75)) rams during sexual quiescence. Conversely, MEI was minimal (ad libitum, 289 (s.e. 8.4) kJ/kg M(0.75); restricted, 428 (s.e. 8.1) kJ/kg M(0.75)) during the rut. Distinct cycles of heat production (HP) accompanied changes in MEI. Changes in HP were similar (P > 0.05) for both groups (ad libitum, 520 (s.e. 22.1) to 394 (s.e. 9.2) kJ/kg M(0.75); restricted 503 (s.e. 14.0) to 407 (s.e. 17.5) kJ/kg M(0.75)) and therefore energy retention varied more (P < 0.015) when rams were given food ad libitum (ad libitum, 131 (s.e. 43.1) to -106 (s.e. 38.2) kJ/kg M(0.75); restricted, 78.0 (s.e. 27.1) to -53.0 (s.e. 38.2) kJ/kg M(0.75)). Apparent digestibility of dietary energy varied inversely with MEI (P < 0.01). MERs ranged from 524 (s.e. 35.0) kJ/kg M(0.75) to 401 (s.e. 27.3) kJ/kg M(0.75), a proportional fluctuation of +/- 0.13. Changes in metabolic rate preceded those in appetite, suggesting a causal relationship.
ISSN:1357-7298
1748-748X
DOI:10.1017/S1357729800051237