The release of LH at oestrus in ewes on two planes of nutrition during lactation.

Abstract

Departments of Animal Science and Biochemistry, University of Natal, Pietermaritzburg, South Africa The anoestrous condition which follows upon periods of underfeeding in ewes is apparently similar to the normal seasonal anoestrus and is usually manifested as a prolongation (Hunter, 1962) or precipitated onset (Smith, 1962) of the seasonal period of sexual rest. It has been suggested that the ovarian quiescence noted in underfed animals may be the result of pseudohypophysectomy (Mulinos & Pomerantz, 1940; Lamming, 1966; Leathem, 1966). An acute release of LH at oestrus in ewes has been demonstrated by Niswender, Roche, Foster & Midgley, 1968; Goding, Catt, Brown, Kaltenbach,Cumming & Mole, 1969; Wheatley & Radford, 1969) and it is possible that changes in the pattern of LH release may indicate functional changes in the pituitary of ewes which become anoestrous after periods of inanition. This phenomenon was studied in an attempt to elucidate the mechanism involved in a