The response to the
male effect as for velocity, synchrony intensity and percentage of ovulating
females, is dependent on environmental, social, physiologic and genetic
factors.
These
factors are broadly explained below:
Sexual status of the
animals involved in male effect: The sexual status of
the animal is extremely important to obtain a favourable result when working
with biostimulation because it performs sexual behaviors more frequently (Veliz
et al, 2002 ) which favour the quality of the stimulus an important factor for
successful male effect (Veliz et al, 2006).
The
sexual experience of the female:
The experience of the
female which will be submitted to the male effect can be a regulatory fact in
the response to the male effect (Gelez and Fabre-NYS 2006 Veliz et al; 2009).
Chanvalllon et al 2010 found that muil-iperous goats had shorter latency
between the introduction of male and the onset of physiologic changes when
compared to nulliparous females, which showed physiological changes 45 minutes
after the nulliparous.
However, the latency
between the introduction of the male and luteinizing hormone surge was not
affected by the female experience. In term, Walkden Brown et al (1993) reported
that when exposed to buck fleece, nulliparous does show a better response to
treatment than nulliparous female.
Ferandez et al (2011)
and Sampaio et al (2012) verified no physiological changes (alterations in L.H
surge), neither on the fertility of the nulliparous compared to nulliparous
goats after the introduction of the male. Previously higher for small
follicles, which evidences the role of the male in ovulation induction
(Delgadills et al 2011).
According to Alvarez et
al (2009) does subject to the male effect showed luteinizing hormone surge (LH)
from 80 to 317 minutes, with 5.7 to 80 pulses within 39 hours and ovulation
between 8 to 10 days after the introduction of the male. The first estrous
induced by male’s presence may be accompanied by ovulation. The male effect is
similar (1.8+0.2, 2.0 + 0.9) (Delgadillo et al; 2011) for the first time and
second estrous respectively.
Thus, a female
naturally or artificially inseminated at the first estrous can be fertile.
Therefore, in all ruminant with the introduction of male, there is a
progressive hormonal adjustment, promoting stabilization of physiologic and
adequate ovarian functionality. Thus, it is commonly observed that short
estrous at the beginning of bio stimulation of the male (Gonalez-Bulnes et al,
2006).
These physiological
regulations mean that the females are likely to conceive on the next-estrous
when compared to the physiological state existing at the first estrous since
the ovarian functions are re-established to normality (Mellado et al; 1994).
Fores et al (2000)
achieved a pregnancy rate of 95% at the second estrous and only 10% at the
first estrous.
Stage
of Postpartum:
This method alone has
been shown to effectively synchronize estrus (all does breed in 10 days) with buck introduction 28 days post-kidding.
Unless male induced estrus activity is initially preceding the natural breeding
season, the response is temporary in nature and the doe will return to
initiating breeding season early or in combination with some drug-induced out
–of-season breeding manipulation.
Sexual
Experience:
According to Bench et
al. (2002), prior contact of males with females can provide experience to the
male regarding copulation or can help in disinhibiting of inexperienced males.
Veliz et al (2002),
studied the combination of sexually active males with the introduction of
estrous females at the start of treatment and observed an efficient response to
the male effect (94.7% estrous females in estrous) and concentrated induction
because 79% cows and does demonstrate estrous in the first three days.
Environmental
Factors:
These deals with such
factors as nutrition, the health status of the animal season of the year and
density and group size.
1. Nutrition and health of animals involved in
bio stimulation by the male effect one of the fundamental importance of direct
influence on the results (Scaramuzzi and Martin, 2008)
2. Density and group size: maintenance of high
animal densities per unit of space is a common practice in intensive animal
production systems. High population density of animals in a pen, affects the
behavior and performance to the male effect. Some of these animal behaviors
affected include feeding, drinking and walking. This also makes it difficult
for most of the females to be mated when induced into estrus by the males
present.
3. Season of the year: After estrous induction
by the male effect lambing, calving or kidding is usually delayed during summer
period until estradiol benzoate treatment is given to the animal to induce
parturition.
Genetic
Factor
The factor discussed is
related to the body weight of the animal Body weight:
This is
directly related to the reproductive response of the female when subjected to
the male effect (Rivas Munoz et al; 2010), even when using sexually active
males.
These limiting factors continue to have a negative effect on the
response to the male effect, resulting
in abnormalities related to the estrous cycle, ovulation rate in addition to
increasing the number of does showing an anovulatory estrous. Mallado et al
(1994) observed that in extensive conditions, Does with good condition scored (
BSc: 7 on 9 1-9 range) when compared to the low score (Bsc:2 1-9 range) tends to respond to the male effect
earlier.
Thus, animals selected for the
implementation of the male effect must have optimal body weight related to
parameters such as breed, physiology age etc. other factors include:
Physiological
Factors
These include
temperament of females and the influence of emotional reactivity on the
reproductive success of sheep to be investigated over the past two decades by
Blache and Bickell (2010) who suggested that the temperament is one the
requirements for selection of animals.
Lima (2006) noted that females with calm
temperament responded better to biostimulation by the ram than nervous ewes.
Solva et al (2012) considered that the observation of this parameter influences
the responses of reproductive behavior.