Nutrition for Pregnant Beef Cows

February, 2019
Dr. Philipe Moriel, UF/IFAS Range Cattle Research & Ecuation Center, Ona


Body condition score (BCS) at calving is the most important factor that influences overall pregnancy rate and calving distribution of beef cows. Also, poor nutrition during gestation can alter fetal organ formation and decrease offspring’s future performance (fetal-programming). In 2016, our group obtained funds from The Florida Beef Enhancement Board to evaluate different supplementation strategies for pregnant beef females and its impacts on performance of cows and calves. In this article, we will provide a draft summary of the results currently available for both studies.

  STUDY #1 – Does year-round supplementation of cows pay off?

We believed that year-round supplementation of molasses or range cubes would increase cow BCS throughout gestation and at calving. Also, year-round supplementation of molasses and range cubes would improve calf development during pregnancy, and then, calf growth after birth. In June 2017, mature Brangus cows were allocated to bahiagrass pastures. Treatments consisted of control cows supplemented with molasses from calving until end of breeding season (November to April; MOL-Fall/Winter), or cows receiving year-round supplementation of molasses (MOL-Year-round) or range cubes (CUB-Year-round). The total annual amount of supplement was similar among all treatments (600 lb/cow; Table 1). Trace mineral/vitamin supplementation is being provided during the entire year in a loose meal form for MOL-Fall/Winter cows, or mixed into the molasses or range cubes for cows assigned to year-round supplementation (MOL-Year-round and CUB-Year-round cows).

Table 1

As expected, molasses and range cubes supplementation increased cow BCS at calving (November) compared to cows receiving no supplementation (Figure 1). Although cows assigned to year-round supplementation of molasses and range cubes lost more BCS from calving until the start of the breeding season (Table 2), both treatments maintained greater BCS at the start of breeding season compared to control cow (MOL-Fall/Winter cows). However, no differences were detected for pregnancy rates among treatments (Table 2), which was unexpected, but can be explained by the fact that the control cows (MOL-Fall/Winter) calved in an acceptable BCS (despite the lack of supplementation before calving) and had minimal BCS loss after calving. It is important to highlight that our group has only 1 year of data collection up to this moment. We are repeating this study for a second year to confirm such results. Despite the greater nutritional status of cows during late gestation (indicated by the greater BCS at calving compared to MOL-Fall/Winter cows), calf body weight at birth and weaning did not differ among treatments.

Figure 1.

Table 2. 

STUDY 2 – Supplementing cows during late-gestation

This study: (1) evaluated if dry distillers grains (DDG) supplementation of cows during the entire late-gestation (2.25 lb/day for 12 weeks = 189 lb per cow; August to November) would increase cow reproductive success and calf performance after birth, and (2) investigated if concentrating cow DDG supplementation during the period of lowest nutrient demand (first 6 weeks after weaning) would be more cost-effective than cows supplemented during the entire late-gestation. First, we believed that cows supplemented before calving, regardless of length of supplementation, would have greater reproductive performance than non-supplemented cows. Second, we believed that supplementing 4.50 lb/day for 6 weeks after weaning would reduce feed costs while maintaining cow reproduction success, but it would not cause fetal-programming effects (due to the shorter supplementation period). In contrast, supplementing 2.25 lb/day for 12 weeks would increase feed costs (due to increased labor), but enhance calf growth after birth.  The main question is: is the best nutritional management for the cows also going to result in the best impact on future offspring performance?

At the time of calving (November), cows that received supplementation for 6 weeks or 12 weeks had similar BCS (Figure 2). This response indicates that a 6-week period of supplementation was more cost effective than a 12-week supplementation period, because cows supplemented for 6 weeks achieved the same BCS at calving and had half of the feeding labor costs compared to cows supplemented for 12 weeks. Also, cows supplemented for 6 weeks or 12 weeks had greater BCS at the time of calving AND at start of the breeding season compared to control cows that did not receive supplementation before calving. However, no differences were observed for cow reproductive performance during the 2018 breeding season. As observed in STUDY 1, control cows (NoSUP) calved in an acceptable BCS and had minimal BCS loss after calving, which likely benefited their subsequent reproductive performance. This study is being repeated for an additional year to confirm such results.

Contrary to STUDY 1 described above, we observed differences in calf pre-weaning performance in STUDY 2. Calves born from cows that received supplementation for longer periods (SUP 12 weeks) were 26 lb heavier at weaning compared to remaining treatments. These results (if confirmed after the second year of data collection) indicates that in terms of calf performance, longer periods of supplementation (with smaller daily supplement amount) was required to increase calf weaning weights, and that decreasing the length of cow supplementation period prevented increments on calf weaning weights. If we assume that labor costs in this study was approximately $5 per cow for those assigned to 12 weeks of supplementation, then labor costs for cows assigned to 6 weeks of supplementation would be $2.50 per cow. A savings of $2.50 only. However, the additional calf weaning weights of 26 lb would generate $39 (calf additional value = 26 lb x $1.50 per pound). This additional calf weaning was not observed in cows supplemented for only 6 weeks. Hence, by trying to save $2.50 in cow labor costs, we would not harvest $39 of additional calf weaning value. The major conclusion for this study provides evidence that the best nutritional management for cows sometimes does not result in the best outcome to offspring performance. As mentioned before, this study is being replicated once more to confirm these results.

Figure 2.

Table 3 

Online training - Body Condition Scoring (BCS): Our group, in collaboration with the South Florida Beef and Forage Program, developed an online BCS training tool to educate and improve the accuracy of BCS among stakeholders. It is unique, free and can be taken multiple times!
To access this training, please visit:



Return to top