New nutritional supplement does not harm calves during nursing

The alternative is made with less expensive products such as citrus pulp, molasses and corn syrup.

By Noêmia Lopes

Agência FAPESP – When they are born, calves do not yet have complete control over the rumen, the first of four compartments that form a structure similar to the stomach in ruminants. The development of the organ depends on the ingestion of solid food, which is fermented by bacteria and yields a final product that is absorbed and metabolized by the internal walls of the rumen.

For this reason—and to reduce the cost of maintaining calves on a liquid diet, which decreases the amount of milk available for sale—the diet of calves in the nursing stage is typically supplemented with corn-based concentrate, a food with high energetic value, and protein sources based on soymeal. However, researchers from the Zootechny Department at Universidade de São Paulo’s Luiz de Queiroz Agricultural School (Esalq/USP) in Piracicaba (SP) have sought a superior supplement.

“We are seeking alternatives that help to reduce the production cost and regularize food consumption for calves. Consumption of supplements is sometimes uneven, with days of peaks followed by days without feeding, possibly due to ruminal acidosis. This is a metabolic disturbance caused by a high level of starch (found in corn), which ends up compromising the consumption of solid foods, delaying the development of the rumen,” said Carla Maris Machado Bittar, professor at Esalq/USP, who conducted a research project on the subject with the support of FAPESP.

Bittar and her team’s first objective—to find economically interesting substitutes without prejudicing the development and future performance of the calf—has been reached. “We established safe levels of replacement of corn with citrus pulp (50% or 100%), crude glycerin (up to 10%) or corn syrup (5%),” she said.

The four alternatives are industrial by-products automatically generated during the production of other foods (citrus pulp, for example, is left over from orange juice production). Citrus pulp is also readily available in the Southeast because processing industries are located there, and it is already used in the diets of adult animals in the region.

Furthermore, according to Bittar, these ingredients have the potential to support the health of the rumen. “Citrus pulp contains pectin (a carbohydrate, considered soluble fiber, that is completely used by ruminal bacteria) and may help to reduce diarrhea, the main cause of death among calves 14 days old and younger,” she said.

“Molasses improves the palatability of the concentrates, and, after being fermented, produces butyric acid, which stimulates ruminal development. Later studies could investigate these and other characteristics of by-products,” said Bittar.

Showing that the concentrate favors a reduction in ruminal acidosis and possibly the regulation of food consumption will also require new studies. Bittar explained, “Our objective was to evaluate animals up until the eighth week of life, but there are probably benefits after weaning, when consumption of the concentrate increases.”

One of the factors that suggest possible gains in adult animals is the enhanced development of the rumen observed after inclusion of citrus pulp in the concentrates. The reason for such gains is that developing the rumen earlier may result in greater food consumption, which in turn contributes to more efficient production, particularly in dairy cows.

Conducting experiments

The Esalq/USP project was conducted in rounds of experiments with similar procedures and with differences that involved the type of ingredient used in the concentrates to replace corn (citrus pulp, glycerin, molasses and corn syrup). In the second stage, 10 Dutch calves, approximately 5 days old, were housed in individual shelters at the university’s Experimental Calf Nursery.

The animals received four liters of milk substitute (powdered milk) daily, two liters in the morning and two in the afternoon. This quantity was randomly selected.

“Today, there are two feeding systems for calves, with distinct objectives,” Bittar explained. “One of them is focused on early weaning. It guarantees that the animals gain a reasonable weight at a lower cost since a liquid diet contributes to production costs.”

The second system, by contrast, aims to increase weight gain using more liters of milk or milk substitute (6, 8 and even 12 liters daily), with possible benefits in the potential production of milk in the future.

The animals in the study also received as much water and concentrate as they desired. For one group of the calves, the scientists altered the percentages of test ingredients in the composition of the concentrates. For the others—the control group—the main source of energy in the concentrates was 100% corn, as usual.

“It is important to remember that there were small quantities of other by-products in the formula to adjust it to the necessary levels of fiber. That was the case for soy husks and/or wheat meal,” Bittar said.

Consumption was monitored daily, and the body weight of each animal was recorded once a week. During the second week of life, the team also used blood samples to determine the blood parameters involved in metabolism, such as glucose concentration.

The investigators also collected samples of ruminal fluid with a probe in the fourth, sixth and eighth weeks of life to determine the pH, the concentration of fatty acids (produced by bacteria through fermentation in the rumen) and the level of ammonium nitrogen (nitrogen in the form of ammonia, which can be utilized by bacteria for protein synthesis).

At the end of the eighth week of life, the animals were weighed and then slaughtered to evaluate the weight and volume of the compartments of the digestive tract as well as the upper digestive tract, in addition to counting and measuring the ruminal papillae, structures that coat the internal walls of the rumen. “The greater the number of papillae per unit area, the greater the height and width of these papilla, the greater the capacity to absorb final fermentation products,” said Bittar.

Developments

Bittar coordinated a team with six graduate students in Animal Science and Pastures (two doctoral students and four master’s students, three of whom were FAPESP fellows), four undergraduate students in Agronomical Engineering, two students in the Scientific Mentorship Program under USP’s Dean of Graduate Studies, and a lab technician at the Bromatology Laboratory at the Department of Zootechny.

According to Bittar, “Originally, we would have had a dissertation and thesis linked to the project. But a new FAPESP research grant allowed us to conduct an investigation of the health and metabolism of animals affected by diarrhea in the experiments with citrus pulp and molasses, which resulted in one more dissertation.”

Four studies were presented at national congresses and three at international congresses. “We are now preparing articles for publication in journals,” she noted.