Feeding to Maximize Reproductive Performance of Your Cows and Heifers (Nutrition Update, Volume 13)

Providing adequate nutrition to your breeding herd saves on feed costs and maximizes reproductive performance. It's important to correlate optimum body condition scores (BCS) with the four main feeding stages in a cow's yearly production cycle.

Stage 1
This is the period of early pregnancy. This may correspond with weaning, if you calve in the spring and perhaps the start of your winter feeding program. Here the beef cow is at her lowest level in terms of nutritional requirements and an animal in good body condition can be fed to maintain condition. Generally, fall pastures or medium quality hay (supplying approximately 50-53% TDN & 7% CP) is sufficient for animals in good condition. Cows and heifers should be at a minimum of 3.0. In this condition they will have several advantages over thinner animals such as improved insulation against the cold and a reserve to draw on during times of low energy in the feed. Thin animals will need to gain weight because poor nutrition at this stage can impact placental development and subsequent transfer of nutrients to the fetus.

Stage 2
Stage 2 is the beginning of the 'critical period', 6-8 weeks prior to calving. Here 90% of the fetus growth is occurring, as well as udder development and colostrum synthesis. Energy requirements increase (approximately 58% TDN & 9% CP is required) and generally good quality hay and 2 lbs. of barley are adequate. Suggested nutrient and feed levels will vary according to animal size, condition and environment. Larger framed animals have the capacity to eat more and therefore will have a higher nutrient requirement. Animals in poor body condition need a more energy dense ration in order to gain weight. On average, forage intake will increase by about 30% during periods of low temperatures. At calving the optimum BCS for mature cows and first calf heifers is 3.0 and 3.5 respectively. Cows and heifers that are losing weight during this period may have problems returning to estrus. The quality of colostrum can be significantly reduced if cows do not receive adequate energy pre-calving and subsequent calf performance can be impacted.

Stage 3
Stage 3 is the lactation phase and the second half of the 'critical period'. Nutrient requirements are at their highest level (approximately 60-63% TDN for mature cows, 65% for first calf heifers, & 11-12% CP) since the cow has to provide a high quality and quantity product to her calf, and her body is repairing itself to ensuring rebreeding. One month prior to breeding the cows and heifers should be at a minimum BCS of 2.5. If the cow or heifer is in an extremely poor condition (1.5 or less) she probably will not be able to gain enough weight prior to the breeding season, in order to cycle properly.

Stage 4
The last stage is the breeding to weaning period. Once again the requirement levels are low, since milk production at this stage is decreasing and calves are eating more grass. If the animals are already in good condition they only have to maintain themselves. Generally, well managed, non-drought stressed pastures are adequate. If the feed availability is not adequate and cows are in poor condition, subsequent calf weaning weights can be reduced. Under these circumstances you may want to consider creep feeding the calving and/or weaning early.

Cows and heifers in good condition tend to come into heat earlier than animals in poor condition, and they are more likely to conceive within the first 20 days of breeding. This means cows and heifers in good condition prior to breeding will wean a calf at a higher weaning weight than cows and heifers in poor condition. If you ensure adequate nutrition, particularly during the 'critical period', you will improve your calf crop next year, with a higher percentage of your cows calving early and producing healthy and vigorous calves.

Prepared By:  Melinda German, M.Sc.

Nutrition Update
Volume 13 No.3, February 2003