The 2009 Colorado Nutrition Roundtable took place on Sept. 24 at ColoradoStateUniversity’s Agriculture Research, Development and EducationCenter in Fort Collins. The annual event is sponsored by the regional chapter of the American Registry of Professional Animal Scientists and allied feed industry.

The theme for this year’s conference was “Interactions of nutrition and reproduction in beef cattle.”

Presentations include:

  • Dr. Jason Ahola, Colorado State University Department of Animal Sciences
    Historical review and the general dogma relating to nutrition and reproduction in beef cattle
  • Dr. Andrea Cupp, University of Nebraska Department of Animal Science
    Factors influencing embryonic loss in food animals
  • Dr. Andy Roberts, USDA/ARS research scientist, FortKeogh, Miles City, Mont.
    A review of nutrition/reproduction work at USDA MilesCity Research Station
  • Dr. Jack Whittier, Colorado State University Department of Animal Sciences
    What we’ve done well, and what has hindered dissemination of nutrition/reproduction knowledge to producers?

Dr. Jason Ahola, Colorado State University Department of Animal Sciences

Historical review and the general dogma relating to nutrition and reproduction in beef cattle

Dr. Ahola began his presentation with some questions. “Why is managing beef cow reproduction with nutrition a challenge? Isn’t more better?

The answer, of course, is that it isn’t that simple. While reproduction is probably the most economically important factor in cow-calf production, production costs ultimately drive profitability.

Ahola cites CSU data from 1995 showing the variability in annual cow costs. The average annual cow cost at the time was $377 per head, but producers with cow cost in the lowest one-third of those studied averaged $268 per head. Producers in the high-cost group averaged $490 per head. Breakeven prices ranged from $61 per hundredweight for the low-cost group and $86 for the average group to $117 for the high cost group. The data also show differences between the groups in calf crop percentages, weaning weights and calf weights per cow exposed, but Ahola says annual cow costs account for most of the difference – $222 per head – in annual returns.

Producers who participated in the survey listed “reducing supplemental feed costs” as their top strategy for achieving lower cow costs and breakeven prices. The challenge, Ahola says, is to find a balance between reducing those costs and maintaining reproductive performance.

He offered the following observations:

  • The cow partitions available nutrients, first for maintenance, then for growth, then to reproductive processes such as estrous and pregnancy.
  • Given a 365-day year and the cow’s 283-day gestation period, the cow has 82 days for breeding. The post-partum anestrous interval is one of the key factors in preventing cow pregnancies.
  • Several factors can be involved in extended post-partum anestrous, but nutrition, and especially lack of energy in the diet, plays a major role.
  • Breeding takes place during mid lactation, meaning the cow has her highest energy requirements at this time, and feed availability often is low.
  • Research has shown clear relationships between a cow’s body condition score (BCS) at weaning and pregnancy percentages.
  • The greatest increases in pregnancy percentages occur when producers improve BCS at weaning from 2 or 3 to BCS 4. Moving cows from BCS 4 to BCS 5 also improves pregnancy rates, but the improvement from shifting them from BCS 5 to 6 is less, and from BCS 6 to 7 almost nonexistent.
  • There also is a linear relationship between BCS at birth and days to estrus.
  • Research has shown that adding 1 BCS score, from BCS 3 to BCS 4 at calving, can improve income per cow by 68 percent and improving from BCS 4 to BCS 5 increases income by 152 percent. Improving from BCS 5 to BCS 6 only brings an 8 percent improvement in returns.
  • The benefits from getting more cows to give birth early in the calving season are clear – less labor, better use of feed resources, more uniform calf crop and heavier calves at sale time. Simply breeding earlier probably won’t make late calvers into early calvers. Improving BCS at calving time with good nutrition can shorten the post-partum estrous interval and tighten the calving season.
  • Data from the National Animal Health Monitoring System’s cow-calf surveys show a reduction in the number of producers using BCS to monitor energy reserves in their cow herds.
  • For reproductive efficiency, it is more critical to have higher BCS scores in younger females than in older cows.

Dr. Andrea Cupp, University of Nebraska Department of Animal Science

Factors influencing embryonic loss in food animals

Dr. Cupp’s was the most technical presentation of the day, outlining current research in the role of nutrition in reproductive physiology. She also described how genetic research could produce some new heifer-selection tools based on predictions of fertility. A few key points:

  • A negative energy balance affects follicular growth in females.
  • A starch-rich diet might have a negative effect, while the affect of fat levels are unclear. A high-protein diet seems to improve follicular growth. Overall, no single dietary factor regulates follicular growth – heifers need a good balance of nutrients.
  • Under-nutrition of heifers during the first trimester diminishes the size of ovarian follicles in female offspring.
  • Lower numbers of follicles relates to a need for repeat breedings and longer estrus interval.
  • Follicle counts tend to peak at five to seven years, but cows that start with low counts probably drop out of the breeding herd earlier than those that start high.
  • The “ovarian reserve” is the number of oocytes in the ovary available for ovulation. The reserve is developed while in gestation. There could be a genetic component to high versus low ovarian reserves.
  • The ovarian reserve in females is an indicator of fertility, and could be a heritable trait for predicting heifer pregnancy rates.
  • High ovarian reserves and follicle counts probably provide a “margin for error” in terms of other factors involved in fertility. If the counts are low to medium, producers might be able to improve ovulation with environmental factors such as nutrition.

Dr. Andy Roberts, USDA/ARS research scientist, FortKeogh, Miles City, Mont.

A review of nutrition/reproduction work at USDA MilesCity Research Station

Dr. Roberts discussed how nutrition can affect lifetime reproductive efficiency in beef cattle. He also presented data showing that among some populations of cattle, body condition scores might not need to be as high as previously thought to achieve good reproduction, potentially allowing producers to select for more efficient cows. Key points of his presentation include:

  • A certain percentage of cows will reproduce consistently at BCS 4, although more will consistently produce a calf at BCS 5.
  • The lifetime productivity of a cow depends the weight of calf weaned each year, and on the number of years she produces a calf. Researchers at FortKeogh are studying the inputs required to optimize lifetime productivity in beef females.
  • The difference in calf weaning weights from a two-year-old heifer to a five-year-old cow averages about 100 kilograms, so there is a clear advantage to keeping middle-aged cows in production.
  • Since 2001, FortKeogh researchers have maintained two similar cow herds with two different nutritional treatments. Both graze the same rangeland during the summer, but during the winter they treat one herd normally, with supplemental feed, the other herd has more restricted winter feeding.
  • Heifers entering the study in the restricted group are lighter after their first winter, but tend to catch up with higher gains during the summer.
  • Heifers from the full-feed group have, on average, about a 3.5 percent higher pregnancy rate than those in the restricted group. However, the restricted group, with 27 percent less feed for 140 days during the winter, save about $23.50 per head in feed costs.
  • Factoring in the sale price of the open heifers, the restricted group comes out ahead economically.
  • Restricted cows remained lighter than controls, and the restricted diet affects their offspring. Cows from restricted dams are heavier than cows from control dams in this study.
  • During the first three years of production, retention was greater for control cows from control dams. However, restricted cows from restricted dams have greater retention in later years.
  • Restricted cows out of restricted dams have lighter calves at birth and at weaning, possibly suggesting better adaptation to more restricted environments or drought conditions.
  • Asked about when to look at body condition scores, Roberts stressed monitoring BCS in the cow herd throughout the year, so you know which way they are headed, rather than just a snapshot. If you look at a cow today with a BCS of 5, she might have been a 3 two months ago, meaning she’s improving (good). Or, she might have been a 7 two months ago, meaning she’s declining (bad.) Critical times for BCS observations include calving, weaning and breeding.

Dr. Jack Whittier, Colorado State University Department of Animal Sciences

What we’ve done well, and what has hindered dissemination of nutrition/reproduction knowledge to producers?

Dr. Whittier reviewed the trend for new, Continental genetics influencing U.S. beef herds beginning in the 1970s. These bigger cattle produced more milk and had higher maintenance requirements, bringing reproductive challenges where nutrition was restricted. Today, with a better understanding of relationships between nutrition and reproduction, producers are moderating their cow herds and using composite genetics to capitalize on the benefits of Continental breeds while keeping cow size, milk and maintenance requirements more manageable. Economic realities, he says, have forced the industry to re-think genetic selection and cow nutrition.

Things we have done well, he says, include identifying the critical role of nutrition in reproduction, using BCS scores as a tool, and timing condition changes for targeted gains and efficient use of forage resources. The industry also has made corrections in biological type, and developed new tools for measuring and evaluating performance.

Key points from Whittier’s presentation include:

  • Body condition scoring provides a simple system for measuring and communicating the results of nutritional management in the cow herd.
  • The study of reproduction in beef cattle is relatively new. Nutritional research dates back to the 1700s, genetics to the 1800s, but reproduction research didn’t begin until late in the 1900s.
  • Nationally, cow pregnancy percentages declined during the 1990s, but have moderated in recent years as producers gain better understanding of nutrition.
  • The percentage of calves born in the first 21 days of the calving season has increased from about 56 percent in 1997 to about 64 percent today.
  • Almost 90 percent of calves are born in the first 42 days of calving, reflecting improvements in matching cows to their environments and more efficient breeding systems.
  • Average calf age at weaning has declined in recent years.
  • Cow frame scores have become more moderate, and cow longevity has improved over the past 10 years. Cow replacement rates have declined from about 20 percent in the mid 1990s to around 15 percent today.
  • The CHAPS III (Cow Herd Appraisal Performance System) offers a state-of-the-art beef production record system providing vital information about management decisions and herd performance.
  • The program was developed at North DakotaStateUniversity and is approved by NCBA’s IRM coordinating committee.
  • The North Dakota Beef Cattle Improvement Association will process your records and send reports for $0.35 per cow and an annual $5 membership fee.
  • The CHAPS III program is available for individual use for $200.
  • Find more information on the CHAPS program at NDSU’s Web site. 

Whittier offers the following recommendations:

  • If cows are thin in the summer and fall, wean calves early and feed a protein supplement.
  • If cows are in moderate body condition in the summer and fall and weaning will occur after mid-October, feed a protein supplement from early September to weaning.
  • If cows are in moderate body condition at a September to early-October weaning time, defer feeding a protein supplement until December or early January.
  • Weaning after mid-October without supplementing protein in the preceding months is not recommended.
  • Feed a protein supplement to spring-calving cows grazing range in January through March.
  • Generally, if cows come into winter in good condition, they can afford to lose some condition. But remember, an abundance of winter forage does not mean the forage is good quality. Feeding some protein can help cows utilize dormant forage.