Justification
Young cows have both a growth requirement and a lactation requirement, while heifers and mature cows only have one or the other. This often makes it difficult for the young cow to become pregnant with the second or third calf. Calving in May, rather than early spring, can reduce hay feeding costs for lactating cows. However, those cows must breed later in the grazing season (August), often forcing them to be on a declining plane of range nutrition during the breeding season.
Objective
The objective of this study was to evaluate the effects of energy supplementation on body condition and pregnancy status in May-calving 2- and 3-year-old cows.
Methods
In Year 1, cows were allotted randomly to one of two treatments receiving either 1.5 lb of dried distillers grains (DDGS) or 4.5 lb of DDGS. However, some cows did not adequately consume the supplement and were evaluated as a negative control (no supplement). In Year 2, a negative control treatment was added. Cows were allowed access to supplementation in a self-feeder programmed to allow access to the proper amount of DDGS by the cow’s electronic ID tag. Supplementation began two weeks before breeding and continued through breeding. Prior to bull turn out, cows were tail bled two times, 10 days apart, to measure progesterone concentration to determine cyclicity. Cow body weight and body condition score were recorded before and after breeding and later at calving. Pregnancy status and calving date were also evaluated. Diet samples were collected with esophageally fistulated cows to determine forage quality of the range the cows were grazing.
Results
| Supplement Level, lb/d DDGS | |||
0 | 1.5 | 4.5 | |
Actual Intake, lb/d | 0.06 | 1.26 | 4.13 |
Initial BW, lb (7-8-24) | 916 | 937 | 928 |
Initial BCS | 5.5 | 5.5 | 5.5 |
Ending BW, lb (9-16-24) | 1000 | 1021 | 1039 |
Ending BCS | 5.0 | 5.0 | 6.0 |
Number Open | 2/10 | 2/29 | 1/31 |
| Supplement Level, lb/d DDGS | |||
0 | 1.5 | 4.5 | |
Actual Intake, lb/d | 0.01 | 1.34 | 4.11 |
Initial BW, lb (7-8-25) | 960 | 944 | 950 |
Initial BCS | 5.5 | 5.5 | 5.5 |
Ending BW, lb (9-15-25) | 1026 | 1033 | 1034 |
Ending BCS | 5.4 | 5.5 | 5.6 |
Number Open | 1/30 | 0/27 | 2/27 |
No differences were found in reproductive performance in two years of supplementing May calving 2- and 3-year-old cows. Year 3 is a drought year, and there will be only the low and high treatments, which will be 1 lb/d or 5 lb/d DDGS supplementation due to culling decisions.