Beef cows after calving require a higher plane of nutrition compared to previous months of gestation. Much of this heightened nutrition is geared to drive milk production, help first-time mothers grow and prepare the entire cow herd to cycle and get rebred within 80-90 days, postpartum. Therefore it is important to feed them well-balanced diets made up of the best feed after calving, so essential nutrient requirements are met.
According to National Research Council (NRC) estimates, most post-calving beef cows, which maintain a desired body condition of 2.5 – 3.0 (1 = emaciated and 5 = obese) and are nursing a newborn calf need about 50 per cent more dietary energy and 10-15 per cent more protein over gestation for about 30-45 days after calving.
This means postpartum beef cows must consume about 60 – 62 per cent TDN (total digestible nutrients) and about 11 – 12 per cent crude protein in their daily diet when they are milking at their highest levels (re: 10 litres per day). First-calf cows do not eat and do not milk as well as older cows, but their dietary requirements are almost identical, due to extra nutrients needed for growth. It is also important to remember all cows calving out in early February to April may need 20-30 per cent more dietary energy just to keep warm. This is added to their most basic maintenance needs and supersedes nutrients required for milk production and reproduction.
Essential cattle minerals (and A, D and E vitamins) should also be provided in postpartum cow diets, such as calcium, phosphorus and other essential macrominerals. They need to complement whatever mineral levels often found lacking in postpartum forages and other supplemented feeds. In a similar fashion, trace mineral requirements nearly double since the start of the winter season, and respective bio-available sources of copper, zinc, manganese, iodine, cobalt, and selenium should be fed.
Demands are obvious
It’s easy to see the “how and why” of such elevated postpartum cow nutrition. It’s another thing to actually feed economical and practical beef diets usually comprised of up to 85 — 90 per cent home-grown forages supplemented with energy-enriched grains and high protein feedstuffs. Case-in-point: straw, prairie grass, corn stalks, crop residues and other low-quality forage that fit easily into early to mid-gestation diets simply will simply not work in most postpartum beef cow diets. So it is crucial producers switch to higher quality forage and balance essential nutrients, accordingly.
There are several hundred post-calving diets that could be fed to the typical beef cow herd after calving, some of these either; pass by meeting their nutrient requirements or fail for one reason or another. Consider the following six postpartum beef cow diet examples:
From the above table, we might agree that appropriate energy, protein and mineral supplementation of the homegrown forages yield a passing grade for cow diets; No. 1, No. 3, No. 4 and No. 6, which should meet the overall nutrient requirements of postpartum beef cows. Straw-based diet No. 2 yield a failing grade, because its protein content was marginal (nine per cent) and its dietary TDN energy value (55 per cent) did not achieve the dietary energy required by beef cows after calving. Nearly identical to passed diet No. 4, diet No. 5 failed because a nominal trace mineral salt block (no vitamins) was provided, rather than a well-fortified commercial cattle mineral (with vitamins).
Important for rebreeding
Postpartum diets with a passing grade help beef cows produce lots of milk for their calves (and additional growth in first-calf cows), but also help cows retain optimum body condition (BCS = 2.5-3.0) from calving to the upcoming breeding season. A good BCS is needed to return beef cows after calving to strong estrus heats in order to get re-bred and conceive early in the breeding season. These ‘next year’ calves tend to be born earlier in a shortened calving season, which also results in higher autumn weaning weights.
As proof, Oklahoma State University (OSU) spearheaded a number of excellent studies, which illustrate this clear relationship between good nutrition, body condition score and fertility. In a two-year field trial (1987), their data proved the importance of adequate postpartum BCS in nursing beef cows, namely. Those experimental cows that were fed well to maintain an optimum BCS of 2.7 until breeding, averaged 94 per cent pregnant compared to penmates (which calved in similar body condition) that were fed to lose one-point of BCS, averaged a 73 per cent rebreeding rate.
In addition, sound beef cow nutrition to maintain or build optimum BCS/fertility in beef cows is the most effective when nutritious feeding programs are implemented and fed at the start of the cows’ late-gestation stage. Therefore, producers should start increasing the plane of cow nutrition about 90 days before calving and subsequent postpartum diets should dovetail afterwards to retain precious BCS from the day of calving until beginning of the breeding season. Thin cows (BCS below 2.5) and first-calf cows that are struggling to maintain body condition after calving might be segregated and fed separately.
Whether beef cows are segregated after calving or not, those producers that segregate and save better-quality forage to be formulated into well-balanced diets for the postpartum cow herd have taken one of the best steps forward. These producers are more likely to meet universal post-calving goals: good milk production by all nursing cows, growth on first-calf cows, the cows’ quick return to strong estrus cycles and a cow herd prepared to conceive during the upcoming breeding season. Ultimately, meeting these goals leads to this year’s crop of good growing calves and later-on more pregnant cows.