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Effects of low levels of food intake before and/or after mating on gonadotrophin and progesterone profiles in Greyface ewes

Published online by Cambridge University Press:  02 September 2010

S. M. Rhind ,
S. McMillen ,
G. Z. Wetherill ,
W. A. C. McKelvey  and
R. G. Gunn
S. M. Rhind
Affiliation:
Macaulay Land Use Research Institute, Bush Estate, Penicuik, Midlothian EH26 0PY
S. McMillen
Affiliation:
Scottish Agricultural Statistics Service, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ
G. Z. Wetherill
Affiliation:
Scottish Agricultural Statistics Service, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ
W. A. C. McKelvey
Affiliation:
Macaulay Land Use Research Institute, Bush Estate, Penicuik, Midlothian EH26 0PY
R. G. Gunn
Affiliation:
Macaulay Land Use Research Institute, Bush Estate, Penicuik, Midlothian EH26 0PY
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Abstract

Gonadotrophin profiles during the follicular phase of the cycle prior to a synchronized mating and LH and progesterone profiles at days 2, 6 and 10 post mating were investigated in three groups of 16 ewes. of one group were given 0·5 × estimated metabolizable energy requirements for maintenance (MEM) from 14 days before mating until slaughter 11 days after mating (LL). Ewes of a second group were given 1·5 × MEM during the 14 days prior to mating and then 0·5 × MEM thereafter (HL) and the remaining ewes (HH) were given 1·5 × maintenance throughout the experiment. During the day before mating, plasma samples were collected at 10-min intervals for 8 h and assayed for LH and FSH. Samples were collected at 15-min intervals for 8 h on days 2, 6 and 10 after mating. Each ewe was then injected intravenously with 10 μg LH and samples were collected for a further 3 h. All of these samples were assayed for LH and progesterone. Nutritional treatment did not affect mean follicular phase concentrations of FSH or LH or mean LH pulse amplitude but the mean LH pulse frequency (pulses per h) of LL ewes was lower than that of HH + HL ewes (0·37 v. 0·48; P < 0·05). After mating, mean LH concentrations were unaffected by sampling date or nutritional treatment but the mean LH pulse frequency was lower in HL + LL than HH ewes at day 2 (0·25 v. 0·40; P < 0·01) and day 10 (0·28 v. 0·38; P < 0·05). Mean progesterone concentrations (ng/1) were higher in HL + LL than HH ewes at day 10 (6·77 v. 4·80; P < 0·05) but pulse frequency was not significantly affected. Injection of 10 μg LH on days 2, 6 and 10 after mating was followed by a significant increase in progesterone concentrations. The progesterone response was greater (P < 0·05) in LL + HL ewes than in HH ewes. It is concluded that increased rates of embryo mortality often associated with undernutrition are unlikely to be related to lower circulating progesterone levels per se but may be attributable to reductions in mean LH pulse frequency and consequent changes in progesterone profiles.

Type
Papers
Information
Animal Production , Volume 49 , Issue 2 , October 1989 , pp. 267 - 273
Copyright
Copyright © British Society of Animal Science 1989

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References

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