Feeds and nutrition of dairy goats

An overview of the nutritional needs and requirements of dairy goat

Introduction

Feeding goats involves combining various feedstuffs into an acceptable and palatable ration to meet nutrient requirements. These requirements vary depending on the stage of lactation, gestation, growth and the season of the year. Since goats are ruminants, like cows, sheep, and deer, they have a unique ability to digest roughages containing a great deal of fiber. Fiber is broken down by microorganisms and provides a source of energy to a ruminant. In essence, the goat (a ruminant) is a host to the microorganisms ("bugs"); the host provides the necessary materials to the microorganisms to digest, who, upon digesting these materials produce end products that can utilized by the host. The nutrients considered in diet formulation are energy, protein, minerals, vitamins and water. The balance of nutrients will determine the performance, health and financial outlook of a dairy goat.

The Digestive System

A ruminant's digestive system consists of a four compartment stomach (rumen, reticulum, omasum and abomasum) and the small intestine. The rumen is the largest of compartments and contains many of the “bugs” (bacteria, protozoa, and fungi) that digest the feed. The bugs produce enzymes that aid in the breakdown of fiber.

The breakdown of fiber or cellulose converts to volatile fatty acids which are absorbed through the rumen wall and provide up to 75% of the goat's energy. Protein is produced by the bugs from nitrogen in the feed. Vitamin K and the B vitamins are also manufactured by the microorganisms. The reticulum (honeycomb structure) is the second area and is just below the opening of the esophagus. The omasum is a small round area which contains hanging layers of tissue. The large surface area of these folds allows for the absorption of moisture and volatile fatty acids from feed. The abomasum is considered the "true stomach". It functions like a simple stomach in a monogastric animals and contains hydrochloric acid and enzymes that breakdown feeds to be absorbed by the intestines (Figure 1). The intestines absorb amino acids, sugars, minerals, fats and other nutrients from digested feed.

Feed Nutrients

Energy is the most limiting nutrient to dairy goats. Sources of energy are grass, alfalfa, cereal grains such as corn, oats, wheat and barley and bypass fats. Energy limitations may result from inadequate feed intake, too much low quality feed, incorrect roughage to concentrate ratios. Insufficient energy can lead to weight loss, infertility and reduced production.

Protein is made up of amino acids. Amino acids are vital to all body processes. The term "crude protein" is used to measure the amount of nitrogenous compounds in feed. High quality protein feeds can be found in soybean meal or high quality legume hay.

Minerals are essential to body functions of an animal. Macrominerals are the minerals most nutritionists balance for in a ration because they are usually deficient without supplementation. Calcium, phosphorus, magnesium, and sodium chloride(salt) would be considered macrominerals. The microminerals or trace minerals would be copper, zinc, cobalt, iodine, selenium, iron and manganese.

Vitamins can be divided into two major groups: fat soluble and water soluble. The fat soluble vitamins are stored in the fat or lipid portion of feed and include vitamins A, D, E and K. The water soluble vitamins are usually met by feedstuffs, rumen synthesis and tissue synthesis.

Water is the most overlooked nutrient. It assists in digestion, assimilation of nutrients, excretion of waste products, control of body temperature, growth of young animals and milk production. Access to clean water is very important in dairy goat production.

FEEDING THE MILKING DOE

Initiation and maintenance of a successful lactation is a result of proper dry doe management. If the dry doe was maintained properly, the metabolic adaptations which occur after parturition should be fairly easy on the doe. After parturition, the doe has a high nutrient demand to support milk production. Several things occur to meet this demand. There is an increase in nutrient absorption by the udder tissue and increased mobilization of minerals (like Ca, P and Mg). The size of the gut and the absorptive capacity increases to allow for greater absorption of nutrients. To meet a high calcium demand, increased intestinal calcium absorption and mobilization of bone occurs. With proper management in the dry period, this calcium demand can be met without causing problems like milk fever.

Energy demands as the doe reaches peak lactation follow a similar course. Figure 2 illustrates the relationship between feed intake, bodyweight and milk production. Depending upon the age of doe, peak lactation generally occurs between week 6 and 9 after kidding. Feed intake does not peak until week 12 to 16 postpartum. Therefore, body reserves are used to meet the energy and protein demands for milk production in early lactation. Approximately half of the 305 day milk is produced during the first sixteen weeks of lactation. The doe's nutrient intake will not meet her demands until milk has decreased to 60 to 80% of peak.

Early Lactation

For does, early lactation ranges from 0 to 90 days milking. Adaptation from the dry to the milking doe ration should occur over a 7 to 10 day period. This is a critical time for does because they need to be challenged, but dry matter intake lags behind the milk demand. Challenge or lead feeding is necessary to determine the genetic potential of a doe. As a doe freshens, feed a grain mix containing 14 to 18% crude protein (CP) and 74 to 78% energy (TDN) along with ad libitum good quality hay or forage. The ration fed will vary with the quality of forage available. The complete diet should contain at least 17.5% crude fiber to maintain a healthy rumen fermentation. As milk increases, increase feed by 1 pound of grain for every additional 2 pounds of milk. In challenging the doe, feed an additional 1/2 to 1 pound of grain. If the doe does not respond to the additional grain, she may have reached her genetic potential for milk production.

Mid to Late Lactation

Peak dry matter intake is reached in mid lactation and is approximately equal to nutrient requirements for milk production. In late lactation, grain feeding should be equal to milk production. The grain ration should contain 13 to 16% crude protein and about 74% TDN and be fed along with ad libitum good quality hay or forage. Milkers may need to gain extra weight to replenish body stores for the next lactation. It is more efficient to add extra weight to does in late lactation than in the dry period.

Dry Period

The first 0 to 100 days of the dry period may be part of late lactation or the start of the dry period. Proper nutrition is critical during this time because mistakes can adversely affect the subsequent lactation. If the doe has a body condition score of 3.5 to 4.0, it will be easy to maintain her during this time. Feed the forage available, preferably a good quality mixed grass hay and/or a high fiber pellet. Grain can be fed during this time according to the body condition of the doe and according to the forage quality but limit grain feeding to no greater than one percent of body weight. The last 50 days of gestation is important to fetus growth. Make sure energy, protein, mineral and vitamin requirements are met in the diet. During the last 2 to 3 weeks of gestation, incorporate a little of the milk doe ration gradually. This will give the "bugs" time to adapt and aid in the transitional period from dry to milking. Grain could be fed at 1/2 to 1 pound a day.

Doelings or Replacements

An 18% CP lamb or calf pellet along with a good quality mixed grass/alfalfa hay would be adequate. Ionophores may be utilized as growth promoters and for coccidiosis control. A coccidiostat may be fed if a growth promoter is not desired. Doelings can be bred at approximately 70 pounds and 7 months of age. Managing weight gains to meet this goal can improve profitability.

Bucks

Bucks can be fed the dry doe ration if necessary. At least 4 to 6 weeks prior to breeding, bucks should be condition scored. This is the time when additional feed is necessary. Increase the energy of the ration, and feed the bucks according to condition. When breeding season arrives, the bucks will be ready and feed intake may change due to activity. Some research has found additional zinc can increase sperm counts and motility. The macro minerals like calcium, phosphorus and magnesium must be balanced properly in order to avoid urinary calculi.

Sample Grain Rations

Level of Protein in Finishe Mix

1

3 4 5

Ingredients

12%

14% 

16%  18% 20%

Cracked or Rolled Corn

1100 1000 80 775 675

Rolled or Crimped Oats or Barley

300 300 350 375 400

Wheat Bran or Beet Pulp

300 300 300 300 300

Soybean Meal(44%CP)

115  220 320 420

Soy Hulls, Cottonseed Hulls or Wheat Midds

145 125 100 80 50

Molasses 

125 125 125 125 125

Trace Mineralized Salt  

12 10 10 10 10
Dicalcium Phosphate —   10 10 10 10
Monosodium Phosphate   12 10

Magnesium Oxide  

5 / 2000 5 / 2000 5 / 2000 5 / 2000 5 / 2000

When using a grain ration, be sure to match the % CP of the ration to the quality of hay available. One should always check with a nutritionist before making any changes in their feeding programs.

Related Links:

National Goat Handbook from the University of Maryland

Maryland Small Ruminant Page