In July, I had the opportunity to attend the American Society of Animal Science and American Dairy Science Association Joint Annual Meetings in Indianapolis, Ind. This annual meeting is where much of the latest research, covering all aspects of livestock production, is reported by scientists from across the county and world.
There were numerous interesting research findings presented, and though I cannot share them all, I thought a few would be of interest to our producers here in Minnesota and around the region.
In recent years, our lab at the University of Minnesota, in collaboration with other scientists at South Dakota State University, University of Wyoming, and Purdue University, have been investigating how transitioning beef heifers from winter development in the dry lot, to turn out on spring pastures at the start of the breeding season impacts growth and reproductive performance.
In past years it was reported that when dry lot developed heifers were placed on spring pastures, heifers lost significant weight in the first week after turn out (>3 lb/d). Furthermore, if this transition from dry lot to pasture happened at the time of artificial insemination (AI), pregnancy rates to AI were reduced, likely due to a change in nutrient intake and the previously observed weight loss.
At this year’s meetings, we presented research (1) demonstrating that if heifers failed to receive adequate nutrition immediately following AI, early embryonic development was slowed and embryo quality was reduced. Research from South Dakota State University (2) further demonstrated that during this transition from the dry lot to pasture heifer behavior was affected.
In heifers that had been developed in a dry lot since weaning, turn out into pasture resulted in increased walking activity. A heifer walking the fence line or looking for a feed bunk is not eating grass; and as would be expected, average daily weight gain in these heifers was decreased.
Collectively, these research presentations and those presented at previous meetings suggest that the transition from the dry lot to pasture is a stressful event for a beef heifer that can cause reduced growth performance and reduce pregnancy success if this transition corresponds to the start of the breeding season.
With the development of estrous synchronization protocols that allow for fixed-time artificial insemination, producers can now AI all females at a set time without the need to detect heat. This dramatically reduces the labor involved with heat detection and often makes conducting AI programs easier for the producer.
These fixed-timed AI protocols are effective, but ask anyone that has used them; you still want to see cows in heat just before or at the time of AI.
Larimore and coworkers (3) investigated the effects of heat expression in a fixed-time AI protocol on early embryonic development. They reported that heifers that were in heat prior to or at fixed-time AI yielded embryos (collected 6 days after AI) that were improved in quality and advanced in development compared to embryos from heifers that were not in heat before fixed-time AI.
In short, heifers that showed heat had better embryos than heifers that did not. Hence, although the fixed-time AI protocols available to producers have been proven effective, the goal of these protocols should still be to have the majority of cows or heifers in heat just before or at the time of fixed-time AI.
It has long been recognized that for optimal reproductive performance cows must receive proper nutrition. The interaction between reproduction and the amount of energy in the cow’s diet has been the focus of many studies.
Results from Gunn (4) and colleagues would suggest that amount and type of protein in a cow’s diet might also be critical for reproductive function. They demonstrated that increasing dietary protein, specifically providing a protein source rich in rumen undegradeable protein (e.g. distillers grains) benefited various reproductive functions in beef cows.
Although these results were interesting, additional research is needed to further determine if the type of protein offered to reproducing beef cattle can improve pregnancy rates.
We all have had calves with poor temperaments from time to time. Usually we blame it on genetics; “her mom is crazy too.” Results from Littlejohn5 and coworkers, however, suggest that ‘crazy’ calves might be due to the stress their mother received during pregnancy.
These scientists demonstrated that stressing a pregnant cow via transporting her several times during gestation, affected the temperament of her subsequent calf. Calves from cows that were stressed during gestation were more excitable and had a poorer temperament than calves from cows that were not stressed during gestation. Therefore, keeping momma calm during pregnancy may be important to ensure that junior is calm when he hits the ground in the spring.
These are just a few of the very interesting research discoveries presented at this year’s meeting. I am sure that the meeting next year will yield many more interesting and important discoveries that can be useful to Minnesota’s beef producers.
If you have any further questions, please contact Dr. Allen Bridges firstname.lastname@example.org; 218-327-4490 or check out the University of Minnesota Beef Team website at www.extension.umn.edu/beef.
(Bridges is a reproductive physiologist at the North Central Research and Outreach Center in Grand Rapids, Minn.)
- Kruse 2013. Influence of post-insemination nutrition on embryonic development in beef heifers. J. Anim. Sci. 91 E-Suppl. 2, Abstract 589.
- Perry 2013. Influence of previous experience on performance and grazing behavior in beef heifers. J. Anim. Sci. 91 E-Suppl. 2, Abstract T176.
- Larimore 2013. Influence of estrus at fixed-time AI on accessory sperm numbers and embryonic development. J. Anim. Sci. 91 E-Suppl. 2, Abstract 220.
- Gunn 2013. Excess dietary protein rich in RUP alters ovulatory ovarian follicle growth and circulating steroid hormone concentrations in nonpregnant, nonlactating beef cows. J. Anim. Sci. 91 E-Suppl. 2, Abstract W366.
- Littlejohn 2013. Effects of prenatal transportation stress on preweaning temperament and growth of Brahman calves. J. Anim. Sci. 91 E-Suppl. 2, Abstract 593.