[MUSIC] Hello, this is Gabriella Varga. And today we will talk about calf nutrition management from the time the calf is born to being weaned off of milk. Calf health, growth, and productivity rely heavily on nutrition and management practices. Every heifer calf born on a dairy farm represents an opportunity to maintain or increase herd size, to improve the herd genetically, or to improve economic returns to the farm. The objectives of raising the newborn calf to weaning age are optimizing growth and minimizing health problems. In this video, we will discuss the development of the calf's digestive system, learn how important colostrum is for the immune system, and the nutrients the calf needs to be healthy and grow well. From birth to about two weeks of age, the calf is a monogastric, or a simple-stomached animal. The abomasum is the only stomach compartment actively involved in digestion, and milk or milk replacer provides the main nutrients for the calf. Let's first get acquainted with the calf's anatomy. At birth, the calf's stomach contains the same four compartments found in adult ruminants. However, the calves reticulum, rumen, and omasum are inactive and undeveloped. The newborn's functional stomach, the abomasum is similar to a human stomach. The objective of calf nutrition is to promote rumen development early in life so that the calf becomes efficient in the absorption of nutrients and has a much smoother transition at weaning. So let's start at the beginning of the the calf's life, and talk about how the calf can digest nutrients, such as those that are in milk. At birth, the rumen has little tissue development and lacks a population of microorganisms. The calf depends mainly on its digestive enzymes, released primarily from the abomasum and small intestine, that help bring down the fats, non-fiber carbohydrates and protein. In the young calf, some liquids can bypass the rumen, and flow directly to the abomasum through the esophageal groove. Calves are initially fed colostrum, their mother's first milk after calving, for about three days after birth. Within ten minutes, a liquid forms a clot in the abomasum due to enzymes and hydrochloric acid acting on casein and fat in the milk. Clotting binds much of the casein and fat into a clump, or a curd, to be digested slowly by stomach enzymes over a period of 12 to 18 hours. Curd development allows for limited meal feeding of calves, compared to other continuous nursing species. The fraction of milk that does not form a curd is called whey. Whey is composed of water, minerals, lactose, and other proteins, specifically, immunoglobulins. Whey passes directly into the small intestine for absorption and/or digestion within ten minutes after feeding. From the small intestine, immunoglobulins can be absorbed into the calf's bloodstream. We will discuss the importance of immunoglobulins for the calf in more detail later. The lining of the rumen wall in an adult cow has very pronounced covering of papillae. These papillae are finger-like projections that greatly increase the rumen surface area, the area through which nutrients can be absorbed. Within a few days of birth, the calf's rumen becomes populated with microbes from feed, the environment in a cow. The papillae development is stimulated by the end products of microbial fermentation. Specifically butyric acid and to a lesser extent propionic acid. There are two separate components to rumen development. The first is the physical size of the organ. By four weeks of age, if the calf is fed only milk, or milk replacer, the rumen will be quite small. As milk, or milk replacer, is fed in increasing amounts, the abomasum grows in size, but the rumen remains proportionally small and grows only moderately. The longer a calf is fed large amounts of liquid feed, the greater the restriction on rumen growth relative to the size of the calf. Lack of rumen development causes a slump in growth rates after weaning. The second aspect of rumen development is the elongation of those rumen papillae and the thickening of rumen walls. Feeding management can drastically affect their development. A calf fed grain, in addition to milk, shows a great deal more papillae development and a much thicker, darker, and a more vascularized rumen wall. Now, compare a third calf fed milk and good quality hay from three days of age. Despite eating moderate amounts of hay, the papillae are not developed at all and the rumen wall is quite thin. This is because the digestion end-products of hay include more acetic acid, which rumen walls do not use for papillae growth and development. Calves with access to large amounts of roughage will have a considerable increase on rumen size. However, this is due largely to stretching, not real growth of the rumen tissue. Feeding calves the correct amount of high-quality colostrum immediately after birth, plays a critical role in the health of the calf. Colostrum, defined as milk removed from the mammary gland in the first 24 hours after birth, contains immunoglobulins that, when absorbed by the calf's gut, helps the calf to resist disease challenges. Calves that receive adequate amounts and quality of colostrum, grow better and are much healthier. The immunoglobulins found in colostrum are large proteins. Calves have openings in the small intestine to accommodate the proteins absorptions, but these openings close shortly after birth. Three types of immunoglobulins can be found in colostrum. Immunoglobulin G makes up 70 to 80% of the immunoglobulins, and helps identify and destroy invading pathogens. Immunoglobulin M comprises 10 to 15% of immunoglobulins, and serves as the first line of defense against infection. And then finally, immunoglobulin A comprises the remaining 15% of immunoglobulins in colostrum, and protects the mucosal surfaces, such as the intestine, from invasive pathogenic bacteria. Colostrum also contains vitamins, minerals, energy, and proteins needed for calf metabolism, growth, and for additional stimulation of the calf's immune system. To make sure that the calf receives immunity from the dam, colostrum management should focus on three factors immediately after birth. How soon, how much, and the quality of the colostrum. Colostrum should be fed within one hour after birth. Approximately 35% of ingested immunoglobulins can be absorbed when calves are fed colostrum immediately after birth. But this declines to less than 5% absorption of immunoglobulins when calves are fed 20 hours after birth. Feed Colostrum at a rate of 12 to 15% of the calf's body weight. Large breed calves, such as Holsteins weighing more than 90 pounds at birth, can be fed four quarts at birth. Feed calves weighing between 50 and 90 pounds, such as Jerseys, three quarts at birth. If possible, feed an additional two quarts to all calves 12 hours after birth. Do not allow calves to suckle the dam to obtain colostrum. Although, suckling does enhance absorption, research has demonstrated that 25 to 40% of calves left with the dam will not ingest enough colostrum to attain adequate levels of passive immunity. Use high-quality colostrum. Colostrum should have more than 50 grams per liter of immunoglobulins, this equates to the green reading on a colostrometer. A colostrometer measures the specific gravity of colostrum prior to feeding. The quality of colostrum is determined by the amount. If a cow produces more than 18 pounds of colostrum, the odds are less than 50% that it will contain sufficient immunoglobulins. Dry period length. If a cow has a dry period of less than 45 days, often have poor quality colostrum, as well as those animals that experienced poor nutrition or heat stress during the dry period. The breed. Holsteins have poorer quality colostrum than other breeds. Colostrum from Holsteins typically are lower in immunoglobulins than colostrum from Jersey cows. And then, the age of the cow. Older cows tend to have more immunoglobulins than first calf heifers, as they have been exposed to a greater number of pathogens.