Late Gestation Preparation

By: Rory Lewandowski, OSU Extension Educator, Agriculture and Natural Resources

The increase in nutrient requirements during the late gestation period is significant. Depending upon the mature weight of the cow, crude protein (CP) requirements increase approximately 28 to 30%, while total digestible nutrient (TDN) requirements increase approximately 15 to 17% between month 7 and month 9.

Nutrient deficiency during this period can result in weak calves that are more susceptible to environmental stresses, and cows that are slow to breed back. Failing to provide late gestation cows with a ration that meets their nutrient requirements will negatively impact the potential profitability of the cow/calf operation. Thus, the cattle manager must prepare for those increased nutrient needs. Preparation involves knowing the weight and nutritional status of the cow, knowing the diet nutrient requirements and knowing the nutrient content of the feedstuffs that are being used.

Nutrient requirements of cattle, as provided by the National Research Council (NRC) subcommittee on beef cattle, vary depending upon the mature weight of the animal, the age of the animal and the production stage of the animal. Large frame heavier animals have higher daily nutrient requirements than smaller frame, lighter animals. Pregnant replacement heifers and two year old cows all have higher nutrient requirements than mature cattle at similar production stages. Examples of CP and TDN nutrient requirements for the last 60 days of gestation (months 8-9) for mature and growing cattle are provided in the following table to illustrate this point. The nutrient density requirements are based on a dry matter intake of approximately 2% of the animal's body weight.

	Nutrient Density		Daily Nutrients		Nutrient Density		Daily Nutrients
		Month 8		Month 8		Month 9		Month 9
Cow Type	CP%	TDN%	CP (lbs)	TDN (lbs)	CP%	TDN%	CP (lbs)	TDN (lbs)
Mature 1200 lbs	7.7	52.3	1.86	12.6	8.8	56.2	2.16	13.8
Mature 1300 lbs	7.8	52.5	1.99	13.4	8.9	56.5	2.31	14.7
2-yr old, 1200 lbs	8.5	55.9	1.93	12.7	9.4	59.7	2.23	14.1
2-yr old, 1300 lbs	8.5	56.2	2.06	13.7	9.5	60.0	2.40	15.1
Pregnant heifer, 1200 lbs*	8.5	56.2	2.02	13.3	9.6	59.9	2.35	14.6
Pregnant heifer, 1300 lbs*	8.5	56.0	2.13	14.1	9.5	59.5	2.45	15.4

1996 NRC for Beef Cattle

* Projected mature weight

Several observations can be made from studying the table:

- The nutrient density requirement of the diet does not vary greatly between weight classes of similar aged animals but nutrient density requirements are higher for younger animals that are still growing. This reflects the relationship between body weight and a dry matter intake based on a percentage of body weight.

- The total amount of nutrients (lbs/day) that are required increases as animal body weight increases for both mature and growing animals.

- Both the nutrient density and the amount of nutrients (lbs/day) increase as gestation advances.

The take-home management message is that the mature weight of the cow should be known to insure adequate nutrients are being provided. Although many cattlemen think they have 1200 lb (or less) cows, there are many 1400-1500 pound cows out in the country-side. I remember hearing at a meeting a couple of years ago a speaker say that most 1200 lb cows weighed 1500 lbs and most 1000 lb round bales weighed 750 lbs. You have to measure and weight if you want to do a good job of managing.

Feeding to meet the needs of a mature cow will put the younger growing cows and heifers in a nutrient deficient state. On the other hand, feeding to meet the needs of the younger cows and heifers will mean that mature cows are being overfed. Both situations are costly. Grouping cows according to age and production stage would allow more targeted feeding and better economical use of feed resources.

In practice, particularly with smaller herds, I see farmers feeding hay free choice to the entire herd. If the hay is close to the required nutrient density, cattle will often eat more than the 2% of body weight figure. This may allow the younger growing animals to meet their daily pounds of nutrients needed, but it means the older animals are over eating.

Besides knowing your cow weights and nutrient requirements, preparation for late gestation involves knowing the nutrient content of the hay, stockpiled forage or other feedstuffs that may be used. It's very hard to economically match nutrient needs without this information.

The eye of experience and close detail to body condition can help managers make good feeding decisions. When used with knowledge of animal weights, nutrient requirements and feedstuff nutrient analysis, the combination can be increased profitability.