Effects of pre-mating undernutrition on oestrus, ovulation and prenatal mortality in Merino ewes

Abstract

Oestrus, ovulation rate and prenatal mortality were studied in 114 mature Merino ewes of high and low body weight at mating. Three nutritional treatments were imposed over 8 weeks prior to hand mating to fertile rams; high plane (HH), low plane (LL) and 7 weeks of high plane followed by 1 week of fasting immediately prior to mating (HL). Ovarian activity, ovulation rate and the extent and timing of prenatal loss were assessed by the appropriate use of direct ovarian observations, pregnancy diagnosis, returns to service and lambing records.While both prolonged undernutrition (LL) and acute nutritional restriction (HL) were associated with some suppression of behavioural oestrus, neither had any appreciable effect on ovulation rate or prenatal mortality. In all groups the right ovary was more active in producing ova than the left, and the HH group had more ovarian follicles (^ 4 mm diameter) than the other two groups. Large unruptured ovarian follicles (6-15 mm diameter) were observed in nine ewes. Significantly more ova shed in multiple ovulations were lost, and multiple-ovulating ewes were more likely to suffer complete rather than partial loss of both embryos. Impaired fertility was evident when ewes that returned to service at an extended cycle length were re-mated.

Effect of protein and energy intake on digestion and nitrogen metabolism in wethers and on ovulation in ewes

“…This apparent stepwise progression in the increase in BCAA concentration with increases in ovulation number is in agreement with the step-like effect of increased protein intake described by Smith (1985). The importance of a change in BCAA concentration also supports the observations that larger increases in ovulation rate occur when ewes are changed from a low to a high, rather than from a medium to a high, level of nutrition (Mackenzie and Edey, 1975;Fletcher, 1981).…”

“…r • , • a poor-quality diet are supplemented with a Digestion and appearance of ammo acids in sub F stant f al q ' u a n t i t y o f h i^ p r o t e i n f o o d ) > rather than when nutrition is increased from The relationship between AA intake from a medium to a high plane (e.g. Mackenzie food and AA concentration in blood is and Edey, 1975;Fletcher, 1981). As little as complex.…”

Embryonic survival and development at various stages of gestation after bilateral egg transfer in the cow

“…In sheep, embryonic loss is higher after multiple ovulation than single ovulation (Casida, Woody & Pope, 1966;Edey, 1966;Mackenzie & Edey, 1975). Among twin-ovulating sheep, mortality is greater if both ovulations occur from the same ovary (Baier & Russe, 1968;Scanlon, 1972).…”