In order to reduce staff hours, particularly for those that find themselves short-staffed during this time, some may ask whether we can be more targeted with lambing surveillance by utilising knowledge of when ewes lamb and what influences this.
Proposed theories for this effect include rumen contractions affecting uterine contractions and hormonal changes. However other studies have not managed to replicate this effect — suggesting the interactions with sheep are more complicated — consider how much management of ewes will vary between farms.
Another study showed that peak lambing period of housed ewes was unrelated to feeding time or diet but was associated with periods of reduced human activity in the barn2. It is important to fertility test rams, particularly in one-sire flocks. Semen testing by qualified veterinarians is recommended to farm-flock producers, especially when only one or two rams are being used.
If semen testing is not possible, the use of a marking harness can be beneficial. If several of the ewes return to heat, it may be necessary to substitute another ram. Reproduction in sheep can be controlled by artificially inducing estrus, ovulation, and fertilization. The use of hormones is effective if management, genetic selection of breeds, and strains of breeds allow for out-of-season breeding. For accelerated lamb production or out-of-season breeding, use sheep that most normally fit the desired reproductive pattern.
To further alter the reproductive process, regulate conditions such as light, temperature, nutrition, association with the ram, and other environmental factors that affect reproduction. In general, three types of hormones are used alone or in combination to achieve these objectives. These are female sex hormones. They include those produced naturally as well as artificially.
Progesterone is produced after ovulation by the corpus luteum, which forms on the ovary. Exogenous progestogens are used during the breeding season to synchronize estrus and ovulation. They also may be used during the anestrous period to help prepare the uterus for pregnancy and to sensitize the animal to be more responsive to hormones that cause estrus and ovulation. They can be administered by ear implant, daily injection, daily feeding, or by insertion of an impregnated sponge pessary placed in the vagina.
During the normal breeding season, progestogens can be used to synchronize estrus when used for a to day period. Estrus and ovulation usually occur between the second and fifth day following the end of treatment.
However, fertility is usually suboptimal on the first cycle after progestogens are administered. Higher fertility is obtained from breeding at the second estrus. When ewes have been synchronized, they generally remain well synchronized through at least the first three post-treatment estrous periods.
Estrogens also are female sex hormones. They are produced naturally by the ovary or they can be produced synthetically. The estrogen concentration in the blood is highest just before and during estrus. The follicles on the ovary from which eggs are developed and released are the main source of estrogens in the female.
The estrogen level, therefore, drops rapidly near the end of estrus, when ovulation occurs. Estrogens are responsible for behavioral estrus or heat. In combination with progesterone, they sensitize the animal to respond to ovulating hormones. They also influence uterine development and the preparation of the uterus for pregnancy. Gonadotropins are hormones that cause ovulation. They are produced by the pituitary gland as well as by certain other tissues.
The gonadotropin that is used most successfully in controlling reproduction in sheep is follicle stimulating hormone. Additionally, human chorionic gonadotropin HCG has been used to induce ovulation. How long do sheep breed for? During her lifetime, a ewe can produce lambs typically from about a year of age up to ten years.
Feed Flushing. How fast do lambs grow? Do you need a milk replacer? This field is for validation purposes and should be left unchanged. This means that the sheep are primarily feeding on hay and grain which is most often kept down at a barn. Incidentally, this also means the sheep are down at the barn making it more likely for them to lamb in the safety and protection of the barnyard areas.
Winter lambing also means that the farmer has more close, direct contact with the sheep as the are spending more time in and around the barn.
0コメント