This summary provides the key details from the document in 3 sentences: The document discusses a study that examined the relationship between milk production and reproductive performance in crossbred dairy cows grazing in an intensive silvopastoral system in Colombia. The study found positive correlations between milk yield and longer reproductive intervals (days open and calving interval) during the dry season, though the correlations were not significant. During the rainy season, there were stronger positive correlations between milk production and days open and calving interval, indicating a stronger association between milk yield and reduced reproductive performance depending on the season.

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2015 Abstracts – Page 84
subsequent reproductive performance. Also, it is detected that the reproductive behavior improved along the years during each season,
which is an important fact that indicates the comfort and nutritional status of the herd under the silvopastoral system.
209. Milk yield and reproductive performance association in crossbred dairy cows grazing intensive silvopastoral system at
tropical dry forest of Colombia.
Zulma Tatiana Ruiz-Cortés1
, Elisa Sierra-Montoya2
, Rolando Barahona Rosales3
.
1
University of Antioquia, Group of research Biogénesis, Medellín, Antioquia, Colombia; 2
National University. University of Antioquia.
Group of research Biogénesis, Medellín, Antioquia, Colombia; 3
National University of Colombia, Medellín, Antioquia, Colombia
It has been a goal for the entire milk industry to increase milk production of dairy herd at early lactation. However, pursuing high
milk yielding, the reproductive behavior of the herd is affected most of the times. This happens due to the asynchrony of milk production
peak and dry matter intake peak, that induces the cow to a negative energy balance, which causes a delay reproductive activation. Recently,
to solve this problem, the intensive silvopastoral systems have been proposed to satisfy the nutritional requirements of the cows through a
higher availability of forage, turning the production system profitable and sustainable along the years. There is lack of information that
demonstrate the association between milk production and reproductive behavior of crossbred dairy cows grazing intensive silvopastoral
systems at a tropical dry forest in Colombia. The main objective of this research is to exhibit the correlation between milk yielding and
reproduction parameters of crossbred dairy cows, such as calving to first service interval, days open, calving interval and services per
conception. Data of crossbred dairy cows (Gyr x Holstein) at early lactation was registered during dry season months (n=41) (June, July,
August, September, December) and rainy season (n=12) (October and November) of 2011. At the same time, reproductive performance of
these cows calving during the same dry and rainy months was registered. Descriptive analysis was performed to the reproductive variables
and milk production of the cows evaluated. Data were analyzed using the Pearson correlation coefficient, to associate both variables. The
reproductive performance for the year 2011 was (Mean + SD): Calving to first service interval: 80.7+58.5 days; days open: 94.06+60.5;
services per conception: 1.45+0.6; calving interval: 378.4+61.1 days and milk production: 20.9+9.51 Lt/day. Regarding to the correlations,
during the dry season, days open, calving interval and services per conception exhibited a positive associations with milk production, even
though it was not significant (r=0.132, 0.121 and 0.025 respectively). Rainy season presented a positive correlation coefficient between
days open (r= 0.54) and calving interval (r= 0.49) and milk production, which indicates a stronger association between variables. The
longer reproductive intervals, the greater milk production, which could be interesting for the dairy farmer in terms of economic income per
liter of milk sold; however, for reproductive aspect, this would impede the goal of one calf per year per cow. This research concludes about
the important relationship between milk production and reproductive behavior under silvopastoral system, which must be adequate for both
profitability.
210. Hormonal regulation of female reproductive cyclicity: a role for progesterone?
Kaiyu Kubota1
, Wei Cui1
, M.A.K. Rumi1
, Pramod Dhakal1
, Michael W. Wolfe2
, Jay L. Vivian1
, Katherine F. Roby2
, Michael J. Soares1
.
1
Departments of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, USA; 2
Departments of
Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA
The fundamental elements regulating the female reproductive cycle have been known for decades and include a hierarchy of
control involving the hypothalamic/anterior pituitary/ovarian axis. The hypothalamus through its secretion of gonadotropin releasing
hormone drives anterior pituitary production of gonadotropins (luteinizing hormone, LH and follicle stimulating hormone, FSH), which act
on the ovaries to promote follicle development, ovulation, formation of the corpus luteum, and secretion of sex steroid hormones, estrogen
and progesterone, with well established actions on the female reproductive tract. At the core of the female reproductive cycle is a balance
of sex steroid hormone negative and positive feedback regulation of gonadotropin secretion. Both estrogen and progesterone signaling
pathways have been implicated in feedback control of gonadotropins and regulation of the female reproductive cycle. Estrogen and
progesterone exhibit context dependent negative and positive feedback regulation of gonadotropin secretion. These concepts have been
reinforced through phenotypic examination of mice possessing null mutations at either Esr1 or Pgr loci. ESR1 and PGR encode estrogen
receptor alpha and progesterone receptor, respectively. These two nuclear receptors mediate many of the actions of estrogen and
progesterone on the female reproductive system. Analysis of rats with an ESR1 deficiency has further strengthened the importance of
estrogen and ESR1 in regulating cyclicity (Endocrinology 155:1991-99, 2014); however, characterization of rats with a null mutation at the
Pgr locus has forced a reexamination of the role of progesterone in the regulation of the female reproductive cycle. We generated two
different Pgr mutant rat models. A 136 bp deletion within exon 1 of the Pgr gene (PgrΔ136E1) was produced by using zinc finger
nuclease-mediated genome editing. The other possesses a 984 bp deletion including all of exon 3 of the Pgr gene (PgrΔE3; the same exon
targeted in Pgr null mice) by using CRISPR/Cas9 system. In both cases, the deletion results in a truncated protein lacking the DNA binding
domain and ligand binding domain due to a nonsense frame- shift and the emergence of a stop codon. Similar to Pgr null mice, Pgr null
rats were infertile due to deficits in sexual behavior, ovulation, and uterine endometrial differentiation. However, in contrast to the reported
phenotype of female mice with disruptions in Pgr signaling (Endocrinology 138:4147-52, 1997), Pgr null female rats exhibit robust estrous
cycles. Four to five day cycles in vaginal cytology, uterine histology, serum hormone levels (LH, FSH, estradiol, and progesterone), and
wheel running activity were evident in Pgr null female rats similar to wild type controls. Furthermore, exogenous progesterone treatment
inhibited estrous cycles in wild type female rats but not in Pgr null female rats. This phenotypic description of Pgr null rats resembles
aspects of those previously described for a patient with progesterone resistance and normal menstrual cycles (J Clin Endocrinol Metabol
48:127-32, 1979). We conclude that in the rat, and possibly other species, progesterone signaling is not required for the establishment and
maintenance of the female reproductive cycle. (Supported by American Heart A ssociation, Japanese Society for the Promotion of Science
and Lalor Foundation postdoctoral fellowships and NIH grants: HD066406, OD01478)
211. Hypoxia induces differentiation of trophoblast stem cells despite the potency-maintaining FGF4.
Yu Yang1
, Marcia Arenas-Hernandez2
, Nardhy Gomez-Lopez3
, Jing Dai3
, Quanwen Li3
, Elizabeth E. Puscheck3
, Daniel A. Rappolee3
.
1
Physiology/Wayne State University, Detroit, MI, USA; 2
Department of Obstetrics and Gynecology, Wayne State University, MI, USA;
3
Department of Obstetrics and Gynecology/Wayne State University, Detroit, MI, USA