Metabolic and production parameters of dairy cows with different dry period lengths and parities

To assess the effects of dry period (DP) length on metabolic, reproductive, and productive parameters, second- (SP) and third- (TP) parity cows were assigned to a traditional (9 weeks, T) or short (5 weeks, S) DP, obtaining four subgroups: second-parity cows with traditional (SPT = 8) and short (SPS = 8) DP, third-parity cows with traditional (TPT = 8) and short (TPS = 10) DP. Plasma insulin-like growth factor-I (IGF-I) and non-esterified fatty acid (NEFA) levels were assessed from 5 weeks before to 14 weeks after parturition. IGF-I concentrations were affected by parity (P < 0.05) and by the interaction of time and DP length (P < 0.01). NEFA levels were affected only by time (P < 0.01). S DP cows showed a shorter interval between calving and ovarian cyclicity resumption (P < 0.01) and a higher milk yield (P < 0.01) and fat and protein corrected milk (P < 0.01) compared with T DP cows. Decreased milk protein content was found in the SPS group compared to the SPT (P < 0.05) and the TPS (P < 0.05) group. In conclusion, a short DP length does not affect reproductive performances, except for hastening the resumption of ovarian cyclicity. A short DP appears to increase milk production and is associated with higher IGF-I levels both in the prepartum and the postpartum period.

Regulators and Integration of Peripheral Signals

In mammals, reproductive function is closely regulated by energy availability. It is influenced by both extremes of nutrition, too few calories (undernutrition) and an excessive amount of calories (obesity). Atypical decreases or increases in weight can have adverse effects on the reproductive axis. This includes suppression of reproductive function, decreases in ovarian cyclicity, reduction in fertility, anovulation, and dysregulation of spermatogenesis. The balance between energy regulation and reproduction is supervised by a complex system comprised of the brain and peripheral tissues. The brain senses and integrates various systemic and central signals that are indicative of changes in body physiology and energy status. This occurs via numerous factors, including metabolic hormones and nutrients. Adipokines, endocrine factors primarily secreted by white adipose tissue, and adipose tissue related cytokines (adipocytokines) contribute to the regulation of maturity, fertility, and reproduction. Indeed, some adipokines play a fundamental role in reproductive disorders. The brain, predominantly the hypothalamus, is responsible for linking adipose-derived signals to pathways controlling reproductive processes. Gonadotropin-releasing hormone (GnRH) cells in the hypothalamus are fundamental in relaying adipose-derived signals to the pituitary–gonadal axis, which consequently controls reproductive processes. Leptin, adiponectin, apelin, chermin, resistin, and visfatin are adipokines that regulate reproductive events via the brain.

Resumption of postpartum ovarian cyclicity in winter-lambing Lohi sheep (Ovis aries)

The postpartum ovarian cyclicity which is associated with uterine involution has significant importance in fertility of sheep. The study was conducted to estimate the postpartum resumption of ovarian cyclicity in Lohi sheep during winter lambing season. Twelve pregnant ewes were selected. The commencement of ovarian cyclicity was investigated in postpartum ewes by estimating progesterone (P4) concentration in blood samples collected on weekly intervals starting from day of parturition till 12th week of postpartum. On the day of parturition, mean P4 concentration was 0.38 ± 0.08 ng / mL. After that, P4 level raised to 0.70 ± 0.13 and 0.83 ± 0.13 ng / mL during 1st and 2nd weeks respectively. During 3rd week, P4 concentration was 1.02 ± 0.18 ng / mL (ovulation). The peak P4 level during first estrous cycle was 3.02 ± 0.8 ng / mL and detected on 5th week. Second ovulation was observed during 6th week and again peak P4 concentration of 2nd cycle was found as 2.5 ± 0.64 ng / mL on 7th week. Based upon the hormonal profile, it was concluded that postpartum ovarian cyclicity resumed on 3rd week of postpartum in winter lambed Lohi sheep.

POSTPARTUM CONCENTRATIONS OF ESTRADIOL AND PROGESTERONE IN THREE GENOTYPE OF SHEEP FED VARYING LEVELS OF PROTEIN

The study aims to evaluate the effects of feeding different protein levels on the resumption of postpartum ovarian activity by measuring serum estradiol (E2) and progesterone (P4) concentrations bi-weekly starting one week postpartum in three genotypes of sheep (Yankasa, Uda and Balami). Eighteen (18) multiparous sheep with aged range of 2.5 – 3 years old consisting of six (6) each of Yankasa, Uda and Balami breeds were divided into three groups and reared on different protein concentrations. The protein concentrations were 15.2% (high), 9.5% (medium) and 6.5% (low). Results showed a gradual increase of estradiol in both Yankasa and Uda breeds fed low protein diet from 100 – 3000 concentration. However, Uda breed had the highest value of estradiol when both medium and high protein diets were fed to the three genotypes of sheep. Nevertheless, Yankasa sheep had more consistent values of progesterone when fed low protein diet compared to Balami and Uda. Also Uda breed recorded the highest progesterone values in both medium and high protein diets among the three genotypes followed by Yankasa sheep. All the three genotypes returned to estrous earlier on high protein concentration followed by those on medium protein level. It is concluded that increase protein concentration hastened resumption of ovarian cyclicity and thereby leading to increase fertility in sheep

Neuroendocrine Basis for Disrupted Ovarian Cyclicity in Female Mice During Chronic Undernutrition

Chronic undernutrition is a type of metabolic stress that impairs reproduction in multiple species. Although energy balance and female reproductive capacity is recognized as tightly coupled, the neuroendocrine loci and molecular mechanisms that mediate ovarian cycle dysfunction during chronic undernutrition in adult females remain poorly understood. Here, we present a series of studies in which we tested the hypothesis that inhibition of kisspeptin (Kiss1) neurons, which are critical for controlling luteinizing hormone (LH) pulses and the preovulatory LH surge in females, underlies the impairment of the ovarian cycle by undernutrition. We first investigated the effect of chronic undernutrition (70% of unrestricted feed intake) on estrous cyclicity in intact female c57bl6 mice. Undernutrition caused a rapid cessation of ovarian cyclicity during the two-week treatment, suppressing ovarian steroidogenesis and inhibiting ovulation. Using two well-defined estradiol replacement paradigms, we directly tested the hypothesis that undernutrition inhibits Kiss1 neurons in the arcuate nucleus (ARC Kiss1) which are required for LH pulses and in the anteroventral periventricular nucleus (AVPV Kiss1) which are necessary for LH surge secretion. Undernutrition prevented LH pulses and impaired ARC Kiss1 neuronal activation, using c-Fos as a marker, in ovariectomized females subcutaneously implanted with a pellet containing a diestrus-like level of estradiol. In addition, undernutrition completely blocked the estradiol-induced LH surge and diminished Kiss1 mRNA abundance, without decreasing Erα, in micropunches of the AVPV. Collectively, these studies demonstrate that undernutrition disrupts ovarian cyclicity in females via impairment of both ARC Kiss1 control of LH pulses and AVPV Kiss1 induction of the LH surge.

Squamous metaplasia of the rete ovarii do not suppress ovarian cyclicity and pregnancy in cattle: case report

ABSTRACT Squamous metaplasia of the rete ovarii is an ovarian pathologic change characterized by replacement of the normal single layered cuboidal epithelium of the rete ovarii by a stratified squamous keratinized epithelium. Uterus and ovaries from a local slaughterhouse pregnant crossbreed cow were evaluated through ultrasound, macroscopically and histologically. Grossly, there were multiple cysts in both ovaries, which were histologically characterized as rete ovarii cysts with squamous metaplasia and intraluminal accumulation of keratinized material. Squamous metaplasia of the rete ovarii has been previously reported in cows, however this is the first report of this condition in a pregnant animal, demonstrating that this ovarian change is compatible with pregnancy.

Neuroendocrine Basis for Disrupted Ovarian Cyclicity in Females During Chronic Undernutrition: A Mouse Model

Chronic undernutrition is a type of metabolic stress that impairs reproduction across species and, in women, is implicated in the development of functional hypothalamic amenorrhea. Although the tight coupling of energy balance to reproductive capacity is recognized in principle, the neuroendocrine loci and molecular mechanisms that mediate ovarian cycle dysfunction during undernutrition remain poorly understood. Ovarian cyclicity is dependent on a population of kisspeptin (Kiss1) neurons in arcuate nucleus (ARCKiss1) for luteinizing hormone (LH) pulses and in the anteroventral periventricular nucleus (AVPVKiss1) for LH surge secretion. Here, we present a series of studies in which we tested the hypothesis that inhibition of both Kiss1 cell populations underlies the impairment of the cycle by undernutrition. During a baseline period, body weight, feed intake, and ovarian cycle stage (via vaginal cytology) were evaluated in female c57bl6 mice. Then, animals were randomly assigned into one of two groups (n=6-8/grp): 1) ad libitum fed controls or 2) feed restricted (70% of feed consumed during the baseline period). Control animals displayed clear and regular cycles throughout the 4-week treatment period. In contrast, feed restriction caused a significant and rapid cessation of ovarian cyclicity (4.8±0.3 vs. 1.5±0.5 estrus cycles/4 weeks; control vs. restricted, p&lt;0.05), causing all females to enter and remain mostly in diestrus. Based on these results, we conducted two experiments to directly test the hypothesis that undernutrition inhibits both modes of LH secretion (and both Kiss1 cell populations) using two well-defined estradiol (E) replacement paradigms. We first evaluated LH pulses in mice that were ovariectomized and implanted subcutaneously with a pellet containing a diestrus level of E (100 ng, OVX+LowE). Following 3 days of feed restriction or control diet (n=3/grp), serial blood samples were collected every 8 min for 88 min. Undernutrition prevented LH pulses and significantly reduced mean LH (5.2±0.6 vs. 0.6±0.2 ng/mL; control vs. restricted, p&lt;0.05). Fixed neural tissue was evaluated by immunohistochemistry to determine whether undernutrition impairs ARCKiss1 neuronal activation, using c-Fos as a marker. The percent of ARCKiss1 neurons expressing cFos was reduced by 90% (p&lt;0.05). We next evaluated the LH surge. After 3 days, control or feed restricted mice were OVX and implanted subcutaneously with a surge-inducing estradiol implant (OVX+HighE, 1 µg, n=3-4/grp). Undernutrition completely blocked the E-induced LH surge (1.9±0.3 vs. 0.2±0.02 ng/mL; control vs. restricted, p&lt;0.05) and diminished Kiss1 mRNA abundance in micropunches of the AVPV (42%, p&lt;0.05). Collectively, these studies clearly show that undernutrition impairs both ARCKiss1 control of LH pulses and AVPVKiss1 induction of the LH surge, via mechanisms that remain to be identified.

Effects of spaceflight aboard the International Space Station on mouse estrous cycle and ovarian gene expression

Ovarian steroids dramatically impact normal homeostatic and metabolic processes of most tissues within the body, including muscle, bone, neural, immune, cardiovascular, and reproductive systems. Determining the effects of spaceflight on the ovary and estrous cycle is, therefore, critical to our understanding of all spaceflight experiments using female mice. Adult female mice (n = 10) were exposed to and sacrificed on-orbit after 37 days of spaceflight in microgravity. Contemporary control (preflight baseline, vivarium, and habitat; n = 10/group) groups were maintained at the Kennedy Space Center, prior to sacrifice and similar tissue collection at the NASA Ames Research Center. Ovarian tissues were collected and processed for RNA and steroid analyses at initial carcass thaw. Vaginal wall tissue collected from twice frozen/thawed carcasses was fixed for estrous cycle stage determinations. The proportion of animals in each phase of the estrous cycle (i.e., proestrus, estrus, metestrus, and diestrus) did not appreciably differ between baseline, vivarium, and flight mice, while habitat control mice exhibited greater numbers in diestrus. Ovarian tissue steroid concentrations indicated no differences in estradiol across groups, while progesterone levels were lower (p < 0.05) in habitat and flight compared to baseline females. Genes involved in ovarian steroidogenic function were not differentially expressed across groups. As ovarian estrogen can dramatically impact multiple non-reproductive tissues, these data support vaginal wall estrous cycle classification of all female mice flown in space. Additionally, since females exposed to long-term spaceflight were observed at different estrous cycle stages, this indicates females are likely undergoing ovarian cyclicity and may yet be fertile.