Suppliments to enhance breeding performance/fertility? - Page 5

lol no worries  : ) 

Moons, timing, OK. And also possible uterine crowding too (litters).

Moons, here's a couple good reasons to manipulate sex ratios that I think are important.

1.  Males perform more consistently throughout their schutzhund careers (no heat-cycle)

2.  More males means less females, and less crowded animal shelters because "everbody's breeding" unwanted pets from those females.

Here's an excerpt from one study by Cheryl S. Rosenfeld and R. Michael Roberts

Theoretical Mechanisms of Sex-Ratio Skewing

Several hypotheses, none of which have been rigorously
tested, have been proposed to explain skewing of sex ratios
in mammals. These hypotheses are not necessarily mutually
exclusive because more than one mechanism could operate
within a single species, and mechanisms might well vary
between species. The proposed mechanisms fall into two
classes: those that operate prior to conception and those that
favor one sex over the other after fertilization has occurred
(Fig. 1).

1. Sperm of one sex might have differential motility or
make their way more directly to the oocyte than the
other depending on the conditions prevailing in the reproductive
tract of the impregnated female, e.g., state of
cervical mucus, nutrient/energy status of tract secretions,
vaginal pH relative to the precise time at which copulation
occurred in relation to estrus (Fig. 1A) [71, 94].
One class of sperm might have intrinsic physiological
differences in viability, capacitation, or the dynamics of
the acrosome reaction [75, 95].

2. Sperm of one sex might be more capable of effecting
fertilization once the egg has been reached, depending
on factors such as the condition of the female reproductive
tract and the penetrability of the zona pellucida,
which likely vary according to the time of ovulation
relative to time of insemination. Depending on the maturational
state at the time of fertilization, the oocyte
might preferentially bind X- or Y-bearing sperm (Fig.
1B) [96].

3. Differences in the rate of development or in the sensitivity
to conditions of XX versus XY embryos within
the female reproductive tract cause a selective loss of
embryos of one sex prior to placentation (Fig. 1, C and
D). Such selection might be favored by particular nutritional
components or developmental asynchrony between
the embryos and uterus. For example, faster
growth of embryos of one sex in a litter-bearing species,
where the space available limits the number of fetuses
that survive, could provide a competitive advantage to
that gender.

4. Selective fetal resorption/abortion is the final possible
means of skewing offspring sex ratio. It would appear
to provide a relatively costly means for adapting sex
ratio to maternal and environmental selective pressures
and was not found to be the cause of sex-ratio skewing
in the recent studies of Jimenez et al. in mice [78]. Nevertheless,
as a result of fetal resorption following implantation,
the Norway rat produces litters biased toward
females if mating occurs at first postpartum estrus following
removal of the first litter [97]. Induced uterine
crowding also leads to a female bias in these rat litters.
In each case, the bias arose from absorption of male
fetuses after they had implanted but within the first half
of pregnancy. Examination of implantation sites in subordinate
female hamsters reveals a preferential fetal loss
of male pups between Days 5 and 10 of pregnancy [65].
Analysis of preterm mortality records from the Medical
Birth Registry in Norway revealed that human male embryos
appear to be more sensitive to uterine stress and
thus likely to be aborted than females [98].

Here's Figure1, as described by the excerpt above.

 Have you ever tried extenze?  Just kidding.  ;)

Three years ago one of my bitches had a litter of 8 all males , don't know if it is true or not but I was told that she must have been bred early in her fertile period ???  Those boys were so much hard work, I couldn't go in the puppy pen unless I wore gum boots and every pair of jeans I owned were torn and holey, NOT to mention my poor hands and legs
BUT BOY THEY WERE A LOT OF FUN I missed them when they were gone .

Her her second breeding she whelped 4 males and 4 females. (thank goodness).

Interesting info, Daryl.