Mike Jarosz, Ph.D.
As spring calving approaches, questions often come up in regards to how nutrition can influence calving difficulty primarily through increased birth weight. Looking at it another way, can the nutrition of the dam be altered to decrease potential calving issues. Hook, 2001 suggested 60% of calving difficulty is due to calf birth weight. In a group of Simmental females delivering calves with an average birth weight of 81.1 lb. the calves were born normal without any issues, but as the birth weight increased the level of calving assistance also increased, (Table 1).
| Table 1. Birth weight and calving difficulty (adapted form Houghton & Corah, 1989) | ||||
| Normal Birth | Hand Pulled | Mechanical Puller | Caesarean | |
| Females, number | 68 | 34 | 16 | 2 |
| % of total | 56.7 | 28.3 | 13.3 | 1.7 |
| Birth weight, lb. | 81.1 | 88.3 | 100.3 | 121.0 |
With such a strong relationship of birth weight to calving difficulty, it is important to consider the strongest factors influencing birth weight, those being genetics and nutrition. Genetics play the strongest role in birth weight with an estimated heritability of 48%, suggesting a producer can select for smaller birth weight calves to help diminish calving difficulty (Houghton & Corah, 1989).
Nutrition can play a role in calving difficulty, with protein and energy being the primary nutrients with the greatest potential for influencing calving difficulty.
Protein: Feeding too much protein has been blamed for increasing the birth weight of calves resulting in calving difficulties. Bolze et al., 1985 fed 2-year old heifers crude protein (CP), levels below, at, or above National Resource Council (NRC) requirements and found no difference in the birth weight of the calves with no statistical influence on calving difficulty (Table 2). It wasn’t significantly different, but numerically they measured a 33% and 24% reduction in calving difficulty for feeding NRC levels or 150% NRC protein levels, respectively. Suggesting to help decrease calving difficulty, feed protein at NRC levels or higher is more beneficial than feeding below requirements.
Table 2. Influence of feeding different levels of Crude Protein 112 days before calving on calving difficulty (Bolze et al., 1985).
| 75% of NRC CP requirement | 100% of NRC CP requirement | 150% of NRC CP requirement | |
| CP, lb/hd/d | 1.7 | 2.3 | 3.4 |
| TDN, lb/hd/d | 13.8 | 13.8 | 13.8 |
| Initial wt | 1214 | 1227 | 1213 |
| Calving weight | 1277 | 1350 | 1368 |
| Initial BCS | 5.4 | 5.4 | 4.9 |
| Calving BCS | 4.5 | 4.7 | 5.1 |
| Birth Weight | 89.4 | 87.2 | 89.2 |
| Calving difficulty, % | 48.3 | 32.1 | 36.7 |
Energy: We commonly think of feeding extra energy to cattle results in extra gain as one would think of a similar influence on birth weight of calves if the pregnant female is fed increasing levels of energy. Another way to consider, if energy is limited, the calf birth weight would be less resulting in fewer calving issues (Bellows & Short, 1978). Angus 4-year old cows were fed two different levels of energy, above or below NRC requirements. Females fed the low energy diet lost weight and BCS, whereas the females fed the high energy diet gained weight and BCS. Although, the higher energy fed cows gained more weight and the low energy cows lost weight, the birth weights of the two groups ended up similar with no change in calving difficulty (Table 3). Feeding extra energy at the levels in this study didn’t result in increased calving difficulty. In this study, the cows gained condition, but possibly didn’t gain too much condition where they deposited too much fat around the pelvic area restricting the birth canal, which may increase calving difficulty.
Table 3. Influence of Energy Level 90 days prior to calving on calving difficulty (Bellows & Short, 1978).
| Low Energy | High Energy | |
| TDN, lb/hd/day | 7.04 | 14.08 |
| Initial wt | 913 | 908.6 |
| Calving weight | 895.4 | 937.2 |
| Initial BCS | 4.7 | 4.95 |
| Calving BCS | 3.55 | 6.75 |
| Birth weight | 68.8 | 67.3 |
| Calving difficulty, % | 0 | 0 |
In general, feeding reproducing females at a moderate level of protein and energy so they at least maintain a moderate condition to slightly higher, will can help minimize the potential nutritional influences on calving difficulties. Using NRC requirements is a strong resource for nutrient targets and your QLF representative can help balance rations for your females to help maintain adequate growth and/or condition.
Bellows, R. A. and R. E. Short. Effects of precalving feed level on birth weight, calving difficulty and subsequent fertility. J. Animal Science.
Bolze, R. P., L. R. Corah, G. M. Fink, and L. Hoover. 1985. Effect of prepartum protein level on calf birth weight, calving difficulty, and reproductive parameters of first calf heifers and mature beef cows. Kansas State University. 1985.
Anthony, R. V., R. A. Bellows, R.E. Short, R. B. Staigmiller, C. C. Kaltenbach, and T. G. Dunn. Fetal growth of beef calves. I. Effect of prepartum dietary crude protein on birth weight, blood metabolites, and steroid hormone concentrations. J. Animal Science. 1986.
Hook, T. Birth weight versus calving ease. Beef. 2001.
Houghton, P. L. and L. R. Corah. Calving difficulty in beef cattle. Kansas State University. December 1989.