OESTRUS AND HEAT PERIOD IN ANIMALS. what is the Oestrus and heat period?
The terms “estrus” and “heat” are related to the reproductive cycles of female mammals, and they refer to specific periods during which the female is sexually receptive and able to conceive. These terms are commonly used in the context of animals. Let’s explore the meanings of estrus and the heat period:
OESTRUS AND HEAT PERIOD IN ANIMALS
Oestrus:
- Definition: Estrus is a specific stage in the reproductive cycle of female mammals characterized by heightened sexual activity and receptivity to mating. It is often referred to as the “heat” period.
- Purpose: The primary purpose of estrus is to facilitate reproduction by signalling to males that the female is ready to mate.
- Hormonal Changes:
- Estrogen: Levels of estrogen increase during estrus, promoting the physical and behavioural changes associated with receptivity.
- Signs of Estrus:
- Behavioural Changes: Females may exhibit increased restlessness, vocalization, mounting behaviour, and a more accepting attitude toward males.
- Physical Changes: Swelling of the external genitalia and changes in vaginal discharge may occur.
Heat Period:
- Definition: The heat period is synonymous with estrus and refers to the time when a female is in a state of sexual receptivity and fertility.
- Duration: The duration of the heat period varies among species. In some animals, it may last for a specific number of days, while in others, it may be continuous until mating occurs.
- Cyclicity: The heat period is typically a cyclical event, recurring at regular intervals, influenced by the species’ reproductive and hormonal patterns.
- Indicators: Observing behavioural and physical indicators helps determine when an animal is in the heat period.
OESTRUS Examples in Domestic Animals:
- Cattle:
- Female cattle exhibit estrus approximately every 21 days, with the heat period lasting about 18 hours.
- Swine:
- The oestrous cycle in pigs is approximately 21 days, with the heat period lasting around 48 hours.
- Dogs:
- The oestrous cycle in dogs is variable, but on average, it occurs every 6 months, with the heat period lasting around 9 days.
- Cats:
- Cats experience a polyestrous cycle, meaning they can go into heat multiple times during the breeding season, with the heat period lasting about a week.
- Horses:
- Mares typically have a 21-day oestrous cycle, with the heat period lasting about 5-7 days.
Proper recognition of estrus and the heat period is crucial for successful breeding programs in domestic animals. It allows for optimal timing of mating or artificial insemination to increase the chances of conception.
Breeders and farmers often use behavioural cues and, in some cases, hormone assays to identify when females are in estrus.
REASONS WHY OESTRUS PERIOD DETECTION IS IMPORTANT IN FARM ANIMALS
the oestrus period detection is important because it enables the farmer to know when his animals can be serviced
the heat period enables the farmer to properly manage the animals for the purpose of cross-breeding and high breeding of farm animals
(iii) the oestrus and heat period also helps the farmer to start preparation for the impending pregnancy
HEAT calculation in animals
(i) The heat or oestrus period is the time when the female animal shows signs of its readiness to mate
It is the period of sexual receptivity in female animals when the ovum or ova are released. That is, the period when ovulation takes place
the heat and oestrus period occurs within the oestrus cycle and is controlled by oestrogen hormones
(iv) Heat period varies from one animal to another e.g
Cow = 5 – 24hours
Ewe = 35 – 36 hours
Sow = 40 – 48 hours
Doe (Goat) = 40 – 50hours
SIGNS OF HEAT IN FARM ANIMALS
The vulva becomes large, red and swollen
There is undue noise-making or granting
A clear viscous secretion comes from the vigina and this arouses and excites the mates
The animal becomes restless
(v) It shows a tendency to be ridden or mounted by other animals
(vi) There is a loss of appetite during the heat period of farm animals
during the oestrus heat period, The animal has an abnormally high body temperature
(viii) Frequent urination
Standing still to be mounted
(x) Frequent tail shaking as in goat
how mating takes place during oestrus heat in animals
The majority of mammals become sexually receptive (express estrus) and ovulate spontaneously at defined intervals. The female will only allow the male to mate during a restricted time coinciding with ovulation. The inefficiency of reproduction is attributable in part to prolonged periods of estrus; thus, the female might need to be bred several times to augment the chances of conception (eg., the mare and dog).
differences in the oestrus and heat period of farm animals
Differences in lengths of oestrous cycles among species are determined primarily by the duration of the luteal phase. Luteal phases of larger mammals are long compared to species of lesser body stature.
Many small animals are subject to predation, and cannot afford the luxury of lengthy nonpregnant cycles (moreover, they are usually litter-bearing, have short gestations, abbreviated or no lactational anestrus, and their young attain puberty quickly). Extinction can quickly besiege those species with extended reproductive cycles (eg., rhinoceroses and elephants).
what are the stages of oestrus and the heat period?
Stages. The oestrus and heat period cycle can be divided into four stages: proestrus, estrus, metestrus, and diestrus. During proestrus, the CL regresses (progesterone declines) and a preovulatory follicle undergoes its final growth phase (estradiol increases).
Ovulation usually occurs during estrus (cows ovulate during metestrus). Proestrus and estrus comprise the follicular phase. Corpora lutea develop during metestrus and function at optimum during diestrus. Metestrus and diestrus make up the luteal phase.
Reproductive tract. Changes in contractility and development of the reproductive tract are regulated by cyclic alterations in secretory patterns of steroid hormones. The oviducts and uterus are motile under the influence of estradiol; progesterone has the opposite effect. The endometrium undergoes proliferation during the follicular phase in response to rising circulatory titers of estradiol.
Progesterone causes endometrial glands to become branched and secretory. Estradiol primes the endometrial response to progesterone (expressed during the luteal phase) by stimulating the synthesis of receptors for progesterone (which inhibits the synthesis of receptors for estradiol).
The cervix becomes dilated in the follicular phase and constricted in the luteal phase; correspondingly, cervical mucus is of either a watery or more dense consistency. Each of the noted changes in the reproductive tract of the female during the oestrus cycle or period have relevance to gamete transport and pregnancy – topics discussed in the next chapter.
Because the structural integrity of the endometrium requires steroidal support, regression of the CL (or ovariectomy leads to atrophy. An ebb and flow of degeneration, growth, and remodelling of the endometrium occur in all mammals (necrosis and sloughing are pronounced in menstrual animals).
The vagina also presents cyclic changes according to hormonal fluctuations. Epithelial cells exfoliated from the vaginal wall can be collected onto a swab, smeared onto a slide, and examined under the microscope; the presence of cornified cells is indicative of estrus (Figure 4-45).
Keratinization of the mucosal lining helps to minimize irritation to the vagina during copulation. With a drop in circulatory estradiol, cornified epithelia is sloughed and the vaginal mucosa becomes very thin; phagocytic leukocytes can then readily migrate into the vaginal lumen
Cows sometimes exhibit a bloody vaginal discharge during oestrus and heat periods; the bleeding originates from essentially intact uterine vessels – diapedesis or pseudo menstruation. Diapedesis also occurs in the proestrous bitch. In some species (eg., murine rodents), conspicuous uterine intraluminal water imbibition at estrus occurs without overt loss of blood cells.
Vessels apparently become leaky in response to an acute elevation in circulatory estradiol. Diapedesis is not the result of hormonal withdrawal, and therefore from a mechanistic standpoint is not comparable to menstruation.
Possible local mediators of diapedesis are histamine, catecholamines, and arachidonate metabolites. Eosinophils infiltrate the uterus in response to estradiol.
Synchronization of estrus. There are advantages to being able to synchronize the timing of estrus and ovulation in livestock. Synchronization techniques result in a uniform animal crop and labor can be concentrated at parturition.
Furthermore, the efficient use of an AI technician is maximized when animals are synchronized to estrus. Oestrous synchronization technologies are costly, laborious, generally yield lower rates of conception than natural service, and require skill and specialized facilities.
The decision to implement a new system of management should be made only after it is deemed feasible and will solve more problems than it creates.
Two basic approaches to synchronization of estrus and ovulation have evolved from an understanding of female reproductive endocrinology – progestin and prostaglandin. Progestins mimic the luteal phase. Estrus and ovulation follow the removal of the progestational influence. Prostaglandin F2a causes luteal regression, thereby synchronizing the onset of a follicular phase.
The Syncro-Mate-B system (history) involved placing a norgestomet-releasing implant between the skin and cartilage of the ear of a cow for nine days.
At the time of implant insertion, the cow was injected with estradiol valerate to induce endogenous uterine production of luteolysin – so when the implant was removed, there was no natural source of progesterone to prevent a prompt return to estrus. Animals can be either observed for estrus (Table 4-6) and bred 12 hours later or bred by appointment 48 hours following implant removal.
The advantages of the Syncro-Mate-B system were that some anestrous animals responded and the synchrony of estrus was tight (timed insemination is practical).
The system was expensive and labour-intensive (animals must be handled twice). It was approved for use in beef animals and dairy heifers. A new alternative for (intravaginal) progesterone delivery is the Eazi-Breed CIDR (controlled internal drug-releasing), which is inserted for 7 days; Lutalyse is given on Day 6.
Orally-active progestins (eg., melengestrol acetate or altrenogest) have been incorporated into livestock rations. Feeding progestins is effective for the induction of oestrus but has not met with widespread application because of cost, unequal consumption, and poor synchrony following cessation.
Ewes can be induced to estrus by treatment with progestin (eg., two weeks by vaginal sponge impregnated with MPA or flurogestone acetate) and PMSG (at pessary removal); however, because of low corporate profits, these products are no longer readily available in the US marketplace.
Naturally-occurring PGF2a as the tromethamine salt (Lutalyse, Upjohn; ProstaMate, Phoenix Scientific), and synthetic analogues of PGF2a such as cloprostenol (Estrumate, Haver), are sold for synchronization of estrus in nonlactating cattle (Figure 4-46) and horses.
The cost of a single-injection prostaglandin program is less than that of a progestin system and not as laborious. Animals must be in diestrus to respond to PGF2a (the young CL is insensitive to treatment), return to estrus is somewhat variable (semen is wasted if breeding by appointment), and treatment of pregnant females can cause abortion.
Porcine CL will not respond to PGF2a until about Day 12 of the oestrous cycle. Gonadotropin-releasing hormone (to induce ovulation and CL formation) is being used in cattle in combination
oestrus and heat period
shares
population
money market
raises funds for expansion
WEED AND THEIR BOTANICAL NAMES
13. FARM YARD MANURE