One of the first questions I like to ask cow-calf producers is, “When are your cows calving?” It gives me an excellent idea as to what stage of nutrition their cow herd needs at the time, so I can recommend the best diet during their post-calving season.
To design a good post-calving diet, I often remember the dietary requirements of the cow herd increase at a modest rate at the beginning of the winter when the average beef cow is in mid-gestation and the cold weather has yet to make a big impact upon her body condition. Her diet of fair- to good-quality forages often supports her requirements for energy and protein as well as those of her small fetus. The cow’s need for essential mineral and vitamin are also nominal.
All changes overnight! This is when her need for energy, protein, minerals and vitamins dramatically increases as the average cow enters her last 45-60 days of pregnancy. They continue to skyrocket for the next couple of months after calving.
That’s because the pre-calving nutrients are used to support her accelerated fetal growth and colostrum (antibody-enriched first milk) production, while a significant amount of nutrients she consumes immediately after calving is transported to her udder to produce five to 10 kg of regular milk each day for her newborn calf. During transition, the cow’s reproductive system is also preparing itself to resume estrus for the subsequent breeding season. The cold weather could also still have a negative impact during those mid-winter calving days.
Of the four essential nutrients consumed by beef cows, energy is needed in the greatest amount during the immediate months after calving. It is expressed throughout beef science literature in two different ways, namely: TDN (total digestible nutrients) or NEm/NEp (net energy maintenance/production). Although, I have used both methods in formulation of my beef feeding programs, I still prefer to design beef diets using older TDN energy values, because I can simply envision TDN values in different feeds in absolute amounts. For example, 10 kg of medium-quality hay containing 55 per cent TDN equals 5.5 kg of TDN energy for beef cows.
TDN values also give me a clear comparison of specific energy values found in different feedstuffs; forages = 40-60 per cent TDN and energy-enriched grains equals 70-75 per cent TDN. It also gives me an idea of forage quality; low-quality forage equals 40-45 per cent TDN such as found in straw, 50-55 per cent TDN medium-quality grass hay and high-quality alfalfa equals 55-65 per cent TDN.
I can design a post-calving cow feeding program by looking up the respective TDN requirements and related information of the beef cow that will be nursing a newborn calf. So, if a mature post-partum beef cow (525 kg, BW) has a feed intake of about 13 kg (2.5 per cent of BW); according to NRC BEEF (2016) requires about 7.5 kg TDN (re: 58 per cent, dmi) to support about 10 kg of milk production and maintain an optimum 2.8-3.0 body condition score until the start of the breeding season.These dietary energy requirements can be managed by a post-calving diet made up of about 11.0 kg of a 55 per cent TDN forage and supplemented with 2.0 kg of grain/barley (75 per cent TDN). Note: My calculations are [11 x .55] + [2 x .75] = 7.5 kg TDN. If cold weather becomes a factor during the calving season and the few weeks beyond, the cows may require extra kilos of TDN and then an additional 1.0-2.0 kg of barley (75 per cent TDN) per cow could be fed to increase its energy density.
After supplying enough energy, I want my feeding program/diets to supply enough protein that meets the respective requirements (NRC BEEF, 2016) of calved-out beef cows. However, unlike energy, protein requirements are usually not impacted by cold winter, but may be challenged by forage quality.
Post-calving protein requirements for 525-kg beef cows are about 1.2-1.4 kg per day, depending on post-partum milk production. If the producer feeds 13 kg of 9.0 per cent protein greenfeed and some grain, it should meet the protein requirement of cows up to calving. However, without protein supplementation of 1.0-1.5 kg of DDGS or 0.5-1.0 kg of a 20 per cent protein low-moisture block, protein requirements may not be fully satisfied for the recent fresh cow.
I also usually recommend beef producers to feed about 70-100 g per post-partum cow per day of a well-balanced commercial beef mineral that compliments the mineral and vitamin profile of the forages and grains being fed.
On a practical basis, most producers I know often fill up mineral feeders every few days to one week’s worth at a time. So, if a producer operates a 200-cow operation and has about eight mineral feeders (one per 25 cows), they should put out a half bag of mineral per feeder per week. Calculations are: (i) 200 cows x 70 g x 7 days = 98 kg, (ii) 98/25 kg = 4 bags of mineral and (iii) 4/8 = 1/2 bag of mineral per feeder. Adjustments can be made if a significant amount of mineral is leftover or wasted.
Pulling together cattle mineral and the other essential nutrients into a comprehensive feeding program for beef cows after calving helps them nurse well-growing and healthy newborn calves. As a result, such good post-calving nutrition promotes producer financial success in one of the most important times of the year.