Supplementing first-calf heifers from calving through breeding
Iowa State researchers observe 2-year-old heifers from first parturition over course of a production year.
By Beth Reynolds and Erika Lundy-Woolfolk
Managing first calf heifers to get a live calf on the ground and rebreed within approximately 100 days is one of the greatest challenges for cow-calf producers. Data from North Dakota State University’s CHAPS program indicates that 2-year-olds and 3-year-olds account for a third of a cow herd’s reproductive failure. This is in part due to the high nutrient requirements leading up to the breeding season. For first calf heifers, this includes nutritional demands to recover postpartum, lactate, grow and establish a pregnancy.
Plenty of data supports a positive plane of nutrition from calving through breeding is beneficial to reproductive success, and in many cases, that involves a supplementation program. Corn and corn co-products are the Midwest standard, although it is important to understand these supplements are not the same. For instance, dry rolled corn is considered a starch-based supplement with a book value of 72% starch on a dry matter (DM) basis while dry gluten is considered a digestible fiber supplement and only contains about 17% starch DM.
Corn as a high starch supplement can have negative effects on fiber digestion due to microbial population shifts if fed in quantities as low as 0.25% BW. However, corn is a cost effective energy source and provides some protein inadvertently through boosting microbial crude protein. Gluten is generally considered a protein supplement and also provides energy through the digestible fiber components. In general, corn co-products such as gluten or distillers are considered more complementary for forage-based diets, even though in some instances corn may be more economical.
With those factors in mind, a study was designed at the ISU McNay Research Farm in southcentral Iowa to observe 2-year-old heifers from their first parturition over the course of a production year. From calving through four weeks post-AI, heifers were allocated to one of three treatment groups: an unsupplemented control, a corn supplement group (CORN), or a gluten supplement group (GLU). Supplements were delivered through a Super SmartFeed™ feeder, from C-Lock Inc., which utilizes EID tags to give a set amount of supplement to individual animals.
Approximately 15% of the cows were less enthusiastic about approaching the feeder and consuming their supplement daily, which causes some inconsistent intake and likely confounded some performance results. Supplement levels (5.56 lbs for CORN and 6.12 lbs for GLU) were based on a hay sample analysis for the first month after calving, when hay made up the base diet and were adjusted (2.38 lbs for CORN and 2.95 lbs for GLU) when pasture became the primary forage source and hay feeding ceased. For the pasture supplement level, assumptions were made on the quality of the pasture.
Variables collected included carcass ultrasound measures (rib fat, ribeye area and intramuscular fat) and body weight at five time points from about one month prior to the expected start of the 2023 calving season to about one month prior to the start of the 2024 calving season. The 2023 calf weaning weights were collected and the first two cycles of calving in 2024 were used to confirm pregnancy data.
The hypothesis was that a boost in performance, measured through calf weaning weight and the number of cows bred earlier in the breeding season would be realized by the supplemented groups compared to the unsupplemented control. As expected, the high nutritional demands of peak lactation, caused females to lose weight and condition over the 82 days (herd average) between calving to the onset of the breeding season. Numerically, the unsupplemented cows had the poorest condition at the time of synchronization, although all treatment groups had poorer body condition scores than desired.
In addition to high nutritional demands, prolonged drought conditions and lower than expected forage quality hindered performance. Cow numbers utilized in the study limited the statistical differences observed, but when observing numeric differences, supplementing first calf heifers improved conception to artificial insemination and the number of open cows after the 65-day breeding season.
Likewise, supplementation treatments averaged a 25-pound 205 adjusted weaning weight advantage compared to calves nursing unsupplemented dams.
In addition to cow and calf performance measures, cool season, unimproved fescue-based pasture samples were taken weekly during the supplementation period and analyzed for yield and quality. The results showed that pasture quality was overestimated and drought significantly restricted quantity. Because of this, all groups, including the supplemented cows experienced a negative plane of nutrition for approximately three weeks leading up to estrus synchronization, and the cows were below ideal body condition as a result.
As a general rule, cattle are more efficient with nutrients utilized for maintenance than gain, and the ending performance differences between groups were not as large as expected, limiting the number of statistical differences. However, the numerical differences still support incorporating a supplementation program for first calf heifers recovering from their first parturition.
Simple cowboy math helps us visualize the benefit of supplementation. In this study calves from supplemented cows had about a 25 lb weaning weight advantage. To limit our example to just the corn-supplemented group, the weaning weight advantage was 18 lbs/calf. If we assume a calf price of $2.50/lb, that’s about a $45 added value.
On average, each cow in the corn group consumed just shy of 5 bu of corn per cow over the 77-day supplementation period. At $5.00/bu, corn was a $25/cow investment to achieve the $45 advantage in weaning weight.
In this scenario, the economics dictated that supplementation of first calf heifers from calving to breeding paid off, even without considering the next calf crop’s advantage when the corn group had 3x the number of females take to AI than the unsupplemented control.
*This research was funded by the Iowa State Beef Checkoff. Iowa State University Extension and Outreach personnel involved in the project are Randie Culbertson, Garland Dahlke, Erika Lundy-Woolfolk, Beth Reynolds and Patrick Wall.
Reynolds is the Iowa Beef Center Program specialist and Lundy-Woolfolk is the Southwest IA Extension beef specialist, both with Iowa State University.
