Progress 10/01/18 to 09/30/19
Outputs
Target Audience:Projects are designed to 1) impact the profitability and productivity of the producer, specifically in New Mexico and theSouthwest region and 2) researchers and academia to increase the understanding of heifer development. Researchconducted through Hatch funding were presented at regional, national, and international conferences throughout the courseof the year. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?1 graduate student helped lead project design and completion for this ongoing project. Additionally, this graduate studenthelped supervise the activities of 1 undergraduate assisting with the project. Students were able to gain experience withsugrical preperation and the ovariectomy surgical procedure. Addition training was given to teach students lab proceduresassociated with ovary disection, follicle aspiration, and oocyte recovery. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?The graduate student responsible for the project is currently completing laboratory procedures and analyzing data for the projects completed through th reporting period.
Impacts
What was accomplished under these goals?
One of the key goals for this project was to determine the effects of pre-breeding nutrition on heifer reproduction and the ovarian microenvironment.Forty-eight Angus cross heifers werestratified by age, body weight, and puberty status and assigned to 1 of 4 pre-breeding nutritional regimes: constant gain drylot (CGD), low-high gain drylot (LHD), constant gain grazing (CGG), or low-high gain grazing (LHG).Specific objectives for this project wereto (1) determine the influence of improved nutrient intake on oocyte competence and the follicular microenvironment in beef heifers, (2) evaluate the effect of increased nutrient intake on primordial follicle number, and (3) identify the influence of increased nutrient intake on metabolic hormone concentrations and subsequent differences in follicular dynamics, oocyte competence and reproductive efficiency. Antral follicle count, which is a predictor of fertilty and the ovarian reserve was reduced in theCGD group compared to all other groups. Additionally, there were fewer primordial, primary, and secondary follicles per section in the CGD compared to their counterparts. These data would suggest that constant gain in the drylot had a deleterious effect on the ovarian reserve. Addtional lab work is being conducted to determine possible reasons for these results. A second study was continuing in to the third and final year of completion during the reporting year. The objective of this study was todetermine the influence of management decisions, such as utilizing growth promoting implants at different keytimepoints, would have on oocyte quality and mechanisms controlling fertility in the ovarian microenvironment. Body weight was greater at weaning in branding implanted heifers compared to heifers recieving an implant at weaning or non-implanted controls. However reproductive responses measured was not impacted by implant treatment. Estrus response, artificial insemination preganancy rate, and final pregnancy rate did not differ among treatments. Additionally, There was no effect of treatment on follicles per section, when investigating follicle density. These data would suggest impanting heifers with Synovex-C at either 3 months of age or 8 months of age did not reduce fertility in beef heifers grazing native forages.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
SL Rosasco, CJ Kassetas, SH Cox, RL Dunlap, J Hernandez Gifford, EJ Scholljegerdes, AF Summers. 2019. Effects of growth-promoting implants administered during the suckling phase or at weaning on growth and reproduction in replacement beef heifers grazing native range. Trans. Anim. Sci. 3:Supp.1 1774-1778.
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Progress 01/20/15 to 09/30/19
Outputs
Target Audience:Projects are designed to 1) impact the profitability and productivity of the producer, specifically in New Mexico andtheSouthwest region and 2) researchers and academia to increase the understanding of heifer development.Research conducted through Hatch funding were presented at regional, national, and international conferences throughoutthe courseof the year. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?One graduate student helped lead project design and completion for this ongoing project. Additionally, this graduate student helped supervise the activities of 3 undergraduate students that assisted with the projects. Students were able to gain experiencewithsugrical preperation and the ovariectomy surgical procedure. Addition training was given to teach students labprocedures associated with ovary disection, follicle aspiration, and oocyte recovery How have the results been disseminated to communities of interest?Conference proceedings What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Through the experiements conducted during the project we determined: 1. NRC estimates to predict heifers developed on forage diets did not allow for accurate gains, thus the compensatory growth expected in Lo-HI heifers did not occur. 2. Heifers developed in the dry lot utilizing a delayed gain strategy had increased body weight gains and feed efficiency during teh last 45 days of the development period, however reproductive parameters were similar to those on a constant gain diet. 3. heifers fed a control diet in the dry lot had a lower antral follicle count compared to heifers developed in the dry lot and devloped on a stair-step diet (having an increased plain of nutrition the last 45 day of the development period) and control fed and stair-step fed heifers grazing native range. 4. Utilization of growth promoting implants at branding resulted in a 13 kg increase in body weights at weaning, but did not impact reproductive function.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
SL Rosasco, CJ Kassetas, SH Cox, RL Dunlap, J Hernandez Gifford, EJ Scholljegerdes, AF Summers. 2019. Effects ofgrowth-promoting implants administered during the suckling phase or at weaning on growth and reproduction inreplacement beef heifers grazing native range
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:Projects are designed to 1) impact the profitability and productivity of the producer, specifically in New Mexico and the Southwest region and 2) researchers and academia to increase the understanding of heifer development. Research conducted through Hatch funding were presented at regional, national, and international conferences throughout the course of the year. Changes/Problems:Twenty-one heifers (7 from each treatment group) were selected for unilateral ovariectomy based on power analysis. Care was taken to select heifers after antral follicle counts to ensure fertility group was not a confounding factor in the study. However, at the time of ovariectomy, 5 heifers were removed from the study (2 branding implant and 3 weaning implant) due to lack of significant structure being present (no follicle >10 mm in diameter) or pregnancy was detected. Due to this factor, we will be preforming unilateral ovariectomies on a subset of heifers in the third and final year of the project. Our objectives in this study will be to determine the mechanisms by which growth promoting implants may alter ovarian function, follicle development or fertilty of heifers. This work is vital to cattle producers due to the challenges in selecting replacement heifers early in their life cycle. Previous data from our group suggest implaning heifers at braning improves weaning weight by 20 pounds compared to no-implanted heifers. However concerns regarding previously published data suggest fertility may be compromised. Although our data reports similar pregnancy rates when heifers are implanted at branding, additional work is warranted to determine the mechanisms that may be impacted if heifers are implanted at a later time-point. What opportunities for training and professional development has the project provided?1 graduate student helped lead project design and completion for this ongoing project. Additionally, this graduate student helped supervise the activities of 1 undergraduate assisting with the project. Students were able to gain experience with sugrical preperation and the ovariectomy surgical procedure. Addition training was given to teach students lab procedures associated with ovary disection, follicle aspiration, and oocyte recovery. How have the results been disseminated to communities of interest?Results have begun to be distributed to communities of interest through public presentations. As additional data are made available once laboratory analysis is completed, materials will be published in regional proceedings and scientific journals. What do you plan to do during the next reporting period to accomplish the goals?The graduate student repsonsible for the project is continuing to oversee the third year of the current study. An additional subset of heifers will be unilaterally overectomized this spring. The graduate student will then have the opportunity to take tissue samples collected to the USDA Meat Animal Research Center to learn bioinformatic analsysis. A secondary study will be initiated this spring to focus more on the management decisions associated with prebreeding nutrition level. heifers will be fed one of 4 diets and prior to the breeding season unilateral ovariectomy occur to collect ovarian tissue and analyze follicle microenvironment.
Impacts
What was accomplished under these goals?
To help determine the influence of management decisions, such as utilizing growth promoting implants atdifferentkey timepoints,would have on oocyte quality and mechanisms controlling fertility in the ovarian microenvironment, a subset of heifers were placed in one of three treatment groups. Heifers recieved a single administration of Synovex C growth promoting implant at 2 months of age (Branding), recieved a single administration of Synovex C growth promoting implant at7 months of age (Weaning), or recieved no implant. Heifers were developed in a single group after weaning and at approximately 15 months of age (coienciding with the breeding season)underwent unilateral ovariectomy to collect ovariantissue for analysis. Hiefers were synchronized prior to ovariectomy utilizing the 7-d Co-Synch + CIDR protocol, with the exception that heifers were ovariectomized at 36-h post CIDR removal and PGF administration. Those heifers not undergoing ovariectomy, were synchronized for artificial insemination utilizing the7-d CIDR protocol with 5 days of heat detection and AI occuring after CIDR removal and PGF administration.Heifers recieveing a growth promoting implant at branding (2 mo of age) had similar numbers of primordial and primary follicles compared to their non-implanted counterparts. However, heifers receiving a growth promoting implant at weaning had reduced numbers ofprimordial and primary follicleswhen compared to both non-implanted and implanted at branding heifers.Ovarian length was smallest (P > 0.01) in heifers receiveing Synovex-C at weaning and did not differ among Branding implanted and non-implanted heifers.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Management decisions impacting reproduction and longevity in the Southwest
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Opportunities for enhancing reproductive success and cow longevity through heifer development
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Effects of growth-promoting implants administered during the suckling phase on growth, conception rates, and longevity in replacement beef heifers grazing native range.
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Progress 10/01/16 to 09/30/17
Outputs
Target Audience:Primary audience for this project include livestock producers and scientists. Results from these studies will be presented at scientific meetings; primarily at the American Society of Animal Science Western Section annual meetings and ultimately published as refereed journal articles. Results will also be presented at livestock producer meetings throughout the state. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Graduate and undergaduate training has been utilized with undergraduates having the opportunity to be involved in day to day animal care, assist in tissue and sample collection and with the analysis of data. Graduate students have had the opportunity to aid in experimental design, data collection, supervision of undergaduate students and data analysis. Additional MS student was able to spend 6 weeks at USDA-MARC with our collaborator learning follicle counting/ultrasounding techniques and lab/ data analysis procedures. How have the results been disseminated to communities of interest?Student compiled current project results in western section ASAS proceedings report What do you plan to do during the next reporting period to accomplish the goals?We are focusing now on management factors that may impact gain during the suckling and developmental phases, utilizing growth promoting implants at various stages of development. We will monitor heifer growth and reproductive performance and conduct unilateral ovariectomies to allow us investigate molecular menchanisms that may be altered to due administration of growth promotants. Additionally, we will continue to work on laboratory procedures to analyze cells collected from follicle aspirations conducted during the first experiments performed.
Impacts
What was accomplished under these goals?
Granulosa cells collected from heifers on differing planes of nutrition were analyzed by a graduate student and our collaborator at USDA-MARC to determine mechanisms that may be altered due to treatment.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Influence of increased nutrient intake pre- and post-breeding on performance and reproductive efficiency of beef heifers
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:Primary audience for this project include livestock producers and scientists. Results from these studies will be presented at scientific meetings; primarily at the American Society of Animal Science Western Sectionannual meetings and ultimately published as refereed journal articles. Results will also be presented at livestock producer meetings throughout the state. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A single graduate student has been assigned to the study and has been given the opportunity to assist with study design and implimentation. Furthermore, this student has gained training in data collection, management, and analysis. This student was heavily involved in the development of the study to include canulated heifers as well as a second study being conducted in a confinement setting. Training has also included learning basic laboratory techniques, such as radioimmunoassays and DNA and RNA extraction. How have the results been disseminated to communities of interest?Data are being prepared for regional scientific meetings (American Society of Animal Science- Western Section) and are being shared with extension personnal to present in statewide presentations. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period we will conduct microarray analysis on granulosa cells and finalize collected data. Manuscripts will be prepared and data presented at regional meetings.
Impacts
What was accomplished under these goals?
Two studies were conducted as outlined in the main proposal with one set of animals grazing dormant native forages. The second study was conducted in a Calan individual feeding system with heifers fed to mimic gains reported on dormant forage. Additionally, we grazed 8 cannulated heifers alongside animals assigned to graze dormant forage with 4 cannualted animals on each of the two planes of nutrition. Based on the supplement levels provided we found their was no difference in nulliparious heifer performance, with AI and final pregnancy rates being similar among treatment groups. Additionally, age at puberty was similar. These results are thought to be cause, in part by the improvement in diet selectivity of grazing heifers compared with clipped forage samples. Heifer supplement levels were determined based on NRC recommendations and clipped forage values. However, masticate samples recovered from cannulated heifers indicate the ability of these animals to select diets up to 8 percentage points greater in crude protein than that of the clipped forage samples. In the second study, confinement fed heifers were subjected to oocyte pick up to determine the effects of plane of nutrition on oocyte competence and follicular quality. Folliclular fluid samples have been analyzed for steroid hormone concentrations and granulosa cells prepared for microarray analysis.
Publications
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2016
Citation:
Effects of increased nutrient intake on growth, reproduction, and productivity of beef heifers
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Progress 01/20/15 to 09/30/15
Outputs
Target Audience:Primary audience for this project include livestock producers and scientists. Results from these studies will be presented at scientific meetings; primarily at the American Society of Animal Science and Society for the Study of Reproduction annual meetings and ultimately published as refereed journal articles. Results will also be presented at livestock producer meetings throughout the state. Changes/Problems:As mentioned previously, heifer performance in the first year of the study did not follow expected gains based on NRC modeling. This may impact results with regard to variation in oocyte quality due to overall similarites in phenotypic performance of the groups. To overcome this challenge we have initiated steps to duplicate the study in a more controlled individual feeding system allowing us to closly monitor heifer performance. However, we have also added ruminally cannulated heifers to the experiment being conducted on native range to help identify factors that may be improving performance above that of the NRC estimates. What opportunities for training and professional development has the project provided?A single graduate student has been assigned to the study and has been given the opportunity to assist with study design and implimentation. Furthermore, this student has gained training in data collection, management, and analysis. Training has also included learning basic laboratory techniques, such as radioimmunoassays and DNA and RNA extraction. How have the results been disseminated to communities of interest?results will be disseminated at producer meetings and regional scientific meetings What do you plan to do during the next reporting period to accomplish the goals?This year we plan to continue the initial study being conducted on native range; however, cannulated heifers will be utilized to identify differences in NRC modeled gains based on forage samples and actual gains using masticate samples to determine diet selection. Furthermore, a subset of heifers (n =24) will be placed in a Calan individual feeding system and feed to gain at similar rates to the initial experiment resulting in a constant and low-high gain group. These groups will also undergo follicle aspiration and oocyte quality will be measured.
Impacts
What was accomplished under these goals?
The experiment listed in the proposal was initiated with 65 heifers randomly assigned to either the constant gain or low-high gain treatment for the 90 day treatment period. A subset of heifers (10 constant gain and 10 low-high) underwent follicle aspiration at the conclusion of the treatment period and folliclular fluid and cumulus oocyte complexes recovered. Radioimmunoassays were used to determine follicular fluid steroidogenic hormone profiles and to determine heifer age at puberty based on blood plasma concentrations collected bi-monthly throughout the experiment. Heifer pregnacy rates and calving data will be added as the data becomes available. Follicular aspirates will be utilized to help determine the role on nutrient intake on prebreeding oocyte quality.
Publications
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