Lecture 21- Beef Cattle Nutrition 1

What are the three major beef production systems?

Cow‑calf → Stocker/Backgrounding → Finishing.

What is the goal of cow‑calf operations?

Produce healthy weaned calves.

What is the goal of stocker/backgrounding systems?

Lean growth and frame development (not fat).

What is the goal of finishing/feedlot systems?

Maximize carcass value on high‑grain diets.

How do beef cows differ from dairy cows nutritionally?

Beef cows are "scavengers" relying on forage + body reserves; dairy cows are "factories" requiring maximal nutrient throughput.

What are the main goals of cow‑calf operations?

Maximize calves weaned, maintain reproductive efficiency, minimize morbidity/mortality, minimize overwintering cost, produce marketable calves.

How does technology use vary by herd size?

Increases with herd size (AI, palpation, ultrasound, estrus sync more common in large herds).

What is the target calf crop percentage?

>90%.

What is the target calving interval?

365 days.

What is the target pregnancy rate?

90-95%.

What is the target weaning weight?

45-50% of cow's BW.

What is the acceptable dystocia rate?

<5% of cows.

What is typical weaning age?

~180 days.

What is typical cow longevity?

7-8 years.

What is typical culling rate?

5-10%.

What are typical beef cattle weights?

Birth 65-100 lb; Weaning ~500 lb; Finished 1000-1300 lb.

What is the dressing percentage?

~63% (59-64%).

What is the goal of backgrounding/stocker programs?

Grow calves to ~700-800 lb with lean gain; prioritize protein + moderate energy.

What are the four major nutrient categories?

Energy, protein, minerals, vitamins.

What is Net Energy for Maintenance (NEm)?

Energy for basal metabolism + environmental adjustments.

What is Net Energy for Gain (NEg)?

Energy for weight gain, lean vs fat deposition, fetal growth, milk production.

What is the hierarchy of energy losses?

Gross → Fecal → Urinary → Gaseous → Heat → Net Energy.

What is crude protein composed of?

DIP (RDP) + UIP (RUP).

What is DIP/RDP used for?

Rumen microbes; requires energy for microbial protein synthesis.

What is UIP/RUP?

Protein escaping rumen degradation.

What is metabolizable protein (MP)?

MCP + UIP; the protein the animal actually uses.

What drives protein requirements?

Average daily gain (ADG); growing animals have higher MP needs.

Which feed type is high in calcium?

Forages.

Which feed type is high in phosphorus?

Grains and corn by‑products.

What imbalance causes urinary calculi?

Low Ca:P ratio.

Which mineral deficiency causes grass tetany?

Magnesium (low in spring grass).

Which mineral always requires supplementation?

Sodium.

Which mineral is high in forages?

Potassium.

Which mineral can cause toxicity?

Sulfur.

Which trace minerals must be supplemented?

Co, Cu, I, Fe, Mn, Se, Zn.

Which vitamins must be supplemented?

A, D, E.

Which vitamins are synthesized in the rumen?

B vitamins and vitamin K.

What factors affect nutrient requirements?

Stage of production, environment, body condition, breed/size.

Which production stage has the highest nutrient demand?

Lactation.

How long is forage deficient in energy post‑calving?

~6 months.

How long is forage deficient in crude protein post‑calving?

3-4 months.

How does cold stress affect requirements?

Increases energy requirement.

How does heat stress affect intake?

Decreases intake (especially on grain diets).

What is the thermoneutral zone for cattle?

32-77°F.

What factors affect thermoregulation?

BCS, haircoat, wet/muddy conditions.

What is the key summary of beef nutrition?

Production system determines strategy; energy + protein drive performance; minerals prevent disease; requirements are dynamic.

Which component of protein is associated with energy requirements?

DIP (RDP).

What should beef calf weaning weight be?

50% of cow's BW.