The Importance of Nutrition During Cattle Pregnancy
by Sara Flexor
Winter feeding and supplementation is often necessary in the harsh Wyoming winter. Grazing alone usually does not meet the nutritional requirements of cows for the duration of pregnancy.
Understanding the requirements of pregnant cattle and how the nutritional needs of cows change as pregnancy progresses is imperative for cow and calf health, as well as generational nutrition.
Late gestation and proper nutrition
Cattle in the first and second trimester are often still nursing their previous calves. The energy they are consuming goes toward milk production, as well as new fetus development.
During this time, the fetus is developing organs, skeletal frame and muscles. Male reproductive system and testicular development is complete by the end of the first trimester.
Early nutrition and diet change have effects on puberty and semen quality in bull offspring. Females form ovaries during the first and second trimester as well.
Therefore, nutrition can affect future reproductive competency in all progeny.
By the third trimester, rapid growth in the fetus, uterus and placenta is occurring, increasing the energy needs of the dam by 21 percent and protein by 12 percent.
The effects and consequences of late gestation undernutrition in cows is significant.
Cows underconditioned prior to and at calving time have an increase in dystocia – difficult birth. These cows also have reduced colostrum volume and quality, as well as reduced mammary gland blood flow.
Additionally, they are prone to producing weak calves which are more susceptible to hypothermia, respiratory disease and scours.
As the calf matures, they are often poor performers with compromised immune systems, reduced growth rate and muscle mass, as well as lower reproductive results.
Conversely, cows receiving supplementation and adequate feed in the last trimester produce heifers which are heavier at weaning, pre-breeding and at pregnancy.
The calves are heavier at birth, exhibit higher average daily gain and improved feed efficiency.
Steer calves from cows managed with a higher plane of nutrition had improved meat tenderness, growth and carcass composition.
Marbling can be impacted prenatally as the muscle fiber number and type is changed and impacted from maternal under and overnutrition.
Proper late-gestation nutrition has long-term consequences in a variety of ways including growth and meat quality.
Importance of BCS
Increasing body condition score (BCS) during the time between weaning and calving is generally easier and more economical than trying to increase BCS from calving to breeding.
Evaluating cows and aiming for a BCS of five to six by calving time is ideal. This score range means the tail head is filled, ribs are not noticeable to the eye and hindquarter muscles are plump and full.
Cows under a BCS of four have noticeable bone structure of the spine, ribs, shoulder, hooks and pins, with little muscle and fat present.
Cows and heifers that calve with a BCS of five or above have a greater percentage of pregnancy rates. Pregnancy rates on cows with BCS of less than four were decreased by up to 29 percent.
Data from the University of Wyoming (UW) demonstrated, during a 60-day breeding season, cows with a BCS between five and six had an overall pregnancy rate of 88 percent, while cows with a BCS of four had an overall pregnancy rate of only 69 percent.
For maximum profit, a cow must produce a calf once every 365 days. This means she must rebreed around 80 to 85 days after calving.
Cows with lower BCS have more difficulty conceiving and are more likely to conceive later in the breeding season, thus calving later in the season the next year. This leads to lighter calves, delayed rebreeding and an eventual decrease in the number of calves produced in a lifetime.
On the other hand, cows which are overconditioned and have a BCS of more than seven also results in poor reproduction rates.
Calves born late in the calving season will be approximately 35 pounds lighter for every 21 days delayed in calving.
It is more economical to supplement cows and improve BCS than to have reduced pregnancy rates.
Key takeaways
Based on the analyses and studies on cows and offspring which have been supplemented correctly during late gestation, it would be worthwhile and valuable to producers to make sure cows are getting adequate protein and energy in the third trimester.
A dry cow during early gestation has a crude protein (CP) requirement of seven percent, around nine percent CP during late gestation and 11 percent CP during early lactation.
To increase one condition score, a cow needs to gain about 75 pounds, which equates to approximately 6.5 pounds of corn on a dry pregnant cow for a 75-day period, in addition to about 25 pounds of hay per day.
A cow with a BCS of four 60 days from calving needs to gain about 1.25 pounds per day to reach a BCS of five at calving.
Supplementing cows grazing on deficient forages with protein and energy will benefit producers in increased calf health, weaning weights and generational nutrition for retained heifers and bulls and will also increase profitability in sold calves.
Sara Fleenor is the UW Extension agriculture and natural resources educator serving Crook County. She can be reached at sfleenor@uwyo.edu or 307-283-1192.
