Approach to the Diagnosis and Management of Decreased Growth and Decreased Weight Gain in Ruminants

1. Take a general history and a diet history.

a. General history

i. What is the age of the animal? When was a decrease in growth observed? How many animals in the herd are affected? What are the ages of the affected animals? Has the herd had historical problems with growth of the young?

ii.

iii. Check for signs or history of previous infectious disease in the herd.

iv. Determine the parasite control procedures for the animal or herd.

v. Examine the environment, including feed preparation areas and equipment, for possible toxic substances (e.g., zinc from galvanized buckets). Ensure cleanliness of bottles and equipment used with nursing animals.

b. Diet history

i. Obtain an accurate diet history, including diet informa­tion when milk or a milk replacer is being fed (birth to 2 or 3 months of age). Note the age and condition of the dam if patient was suckled before weaning. An accurate postweaning dietary history is essential. Suckled animals are developed ruminants at weaning, but hand-reared animals (dairy calves, bummer lambs, and dairy kids)

Targets for Growth in Dairy Heifers²⁷

• Target weight first bred = mature shrunk body weight (SBW) ? 0.55

• Target shrunk weight gain (SWG) before first pregnancy = (Target weight first bred - current SBW)∕(Target age for first pregnancy - current age)

• Target first calving weight = mature SBW ? 0.82

• Target second calving weight = mature SBW ? 0.92

• Target third calving weight = mature SBW ? 1.00

• First pregnant SWG = (Target first calving weight - Target weight first bred)∕280

Modified from National Research Council. Nutrient requirements of dairy cattle, 7th revised ed. Washington, DC, 2001, National Academies Press.

are usually not fully developed ruminants at the time they are weaned from milk.

ii. Inspect all forages and concentrates for quality, signs of spoilage, or abnormal color or odor. Has an analysis been performed on the forage or feed? Is the feed formulated appropriately for a young growing animal? Is the feed stored appropriately?

iii. Because ruminants are often fed in groups, note whether all animals have adequate space to eat simultaneously.

2. Perform a physical examination.

a. Determine the patient's age, weight, and body condition score. Is the patient growing appropriately? The growth curve depends on multiple factors including genetic and environmental factors and can be predicted using a number of different equations, each being adequate for different species or breeds.^8-10 One example is the Brody growth curve¹¹

(1) Wt = A(1 - B e^-kt)

(Wt: body weight at age t; A: mature weight; B: initial weight; k: growth rate; t: age in days)

Targets for growth in dairy heifers are shown in Box 9.5.

b. Does the animal show any signs of infectious or parasitic disease?

c. Does the animal show any signs of congenital abnormalities?

3. Examine the feces. Perform flotation, sedimentation, and Baermann's procedures to detect patent parasitic infestation. Perform a fecal occult blood test; if the result is positive or if there is evidence of diarrhea, see the section on melena or diarrhea in Chapter 7. If diarrhea is noted in neonatal calves, refer to Chapter 20 for diagnostic and therapeutic management.

4. Perform blood analysis.

a. Perform a CBC, including plasma protein and fibrinogen. Use the erythrocytic indices to document and character­ize the anemia if present. If a herd problem exists in a selenium-deficient region, measure the whole blood selenium concentration or glutathione peroxidase activity.

b. Perform a serum biochemical analysis. Serum albumin is decreased late in PCM. Albumin is normally lower in neonates (≈1 g/dL less) than in adults. The blood urea nitrogen (BUN) level is often low in ruminants as a result of urea recycling through saliva.

5. Analyze the diet and improve the feeding program. Compare nutrient intake with the requirements for maintenance and growth of the various ruminant species (Tables 9.5 to 9.11). If the neonate is being fed a milk diet, evaluate the quality of the product and ensure that the animal's intake meets the dietary requirements (see Tables 9.5 and 9.6). Requirements for other breeds and life stages can be found in the nutrient requirement textbooks for dairy cattle, beef cattle, and small ruminants. Ensure that the milk replacer is mixed properly. If the ruminant is consuming a grain mix or forage, ensure that the quantity and quality of the feed are adequate to allow sufficient intake in devel­oped ruminants. Equations to predict dry matter intake are available; some examples are listed in Table 9.12. Forage sampling instructions are listed in Box 9.3. If anorexia is present, look for more specific signs of a primary disease process. If the diet supplies adequate nutrients for maintenance and growth, consider decreased growth and decreased weight gain to be caused by a primary disease condition.

■ TABLE 9.5

Daily Energy and Protein Requirements of Young Dairy Replacement Calves Fed Only Milk or Milk Replacer

^aDry matter intake necessary to meet ME requirements for calves fed milk replacer composed primarily of milk proteins and containing ME at 4.75 Mcal/kg of dry matter.

ADP, Apparent digestible protein, g/d); CP (crude protein), ADP/0.93; DE (Mcal), ME/0.96; ME (Mcal), 0.1 LW⁰'⁷⁵ ? (0.84 LW⁰.³⁵⁵ ? LWG¹'²), where LW and LWG are in kilograms; NEg (Mcal), (0.84 LW⁰.³⁵⁵ ? LWG¹.²) ? 0.69, where LW and LWG (live weight gain) are in kilograms; NEm (Mcal), 0.08δ LW⁰.⁷⁵, where LW is live weight in kilograms. The digestibility of undenatured milk proteins is assumed to be 93%; Vitamin A (IU), 110 IU∕kg of LW

Modified from National Research Council. Nutrient requirements of dairy cattle, ed 7. Washington, D.C., 2001, National Academies Press.

■ TABLE 9.6

Net Energy Requirements of Young Lambs on Milk-Replacer Diets^a

Body Weight in Kilograms (Pounds)

From Chiou PWS, Jordan RM.

■ TABLE 9.7

Net Energy Requirements for Growth of Beef Cattle (Mcal/day)

Shrunk Body Weight (kg); (NE_m Required)

Body Weight (kg); (NE_m Required)

Modified from National Research Council.

■ TABLE 9.8

Protein Requirements for Growth of Beef Cattle^a

Shrunk Body Weight (kg); (MP Required)

Body Weight (kg); (MP Required)

Modified from National Research Council. Nutrient requirements of beef cattle, ed 8. Washington, D.C., 2016, National Academy Press. ^aMetabolizable protein g/day.

■ TABLE 9.9

Calcium (Ca) and Phosphorus (P) Requirements for Growth of Beef Cattle (g/day)

Shrunk Body Weight (kg) (Ca and P Required)

Body Weight (kg) (Ca and P Required)

Modified from National Research Council. Nutrient requirements of beef cattle, ed 8. Washington, D.C., 2016, National Academy Press.

■ TABLE 9.10

Daily Nutrient Requirements of Sheep (Growing Lambs, Growing Rams, and Yearlings)

■ TABLE 9.10

Daily Nutrient Requirements of Sheep (Growing Lambs, Growing Rams, and Yearlings)-cont'd

Modified from National Research Council. Nutrient requirements of small ruminants. Washington, D.C., 2007, National Academies Press

■ TABLE 9.11

Daily Nutrient Requirements of Goats (Growing Goat Kids)

Modified from National Research Council. Nutrient requirements of small ruminants. Washington, D.C., 2007, National Academies Press.

■ TABLE 9.12

Examples of Equations for Predicting Dry Matter Intake (DMI) in Different Kinds of Cattle

^aModified from National Research Council. Nutrient requirements of dairy cattle, 7th revised ed. Washington, DC, 2001, National Academies Press.

^bNational Academies of Sciences EM, Studies DEL, Resources BAN, Cattle CNRB. Nutrient requirements of beef cattle: ed 8. Washington, D.C., 2016, National Academies Press.