Published in Scientific Papers. Series D. Animal Science, Vol. LXI, Issue 1
Written by Roxana-Mariana IGNĂTESCU (ȚÎMPĂU), Ana-Maria GOANȚĂ, A. MIHAI, L. IONIȚĂ
During the first months of life, the calf needs to adapt physiologically to three challenges: extra-uterine life, maintaining the prolonged pre-ruminant stage and weaning. This paper aims to detail the newborn calf’s adaptation to extra-uterine life, namely changes occurring at the digestive level, and less at the endocrine or immunological levels, knowing that the calf is born hypo- or a-gammaglobulemic. At birth, the digestive system of the calf is structurally complete (rumen, reticulum, omasum and abomasum), but functionally incomplete, as the abomasum is the only active compartment in the digestion of the pre-ruminant calf. From this moment and up to two weeks of life, the calf can be considered monogastric, as a result of the existence of an anatomical structure that ensures the passage of the colostrum/milk replacer to the abomasum. The transition from intrauterine life to extra-uterine life is very demanding for the calf, as immediately after birth it has to adapt to new environmental and nutritional conditions. At birth, the young ruminant becomes dependent to the extrauterine environment regarding food intake. Concerning the environment, the greatest adaptation efforts are related to thermoregulation, as the calf transitions from 38.8°C in utero to below 20°C in the shelter. After birth, changes in the newborn’s energy metabolism determine the production of endogenous glucose and the use of fats to compensate for the continued loss of glucose. In the meat industry, young calves are generally fed by their mother and are weaned progressively. Instead, calves coming from dairy cows are separated from their mother immediately after birth and receive colostrum during the first two days of life and then milk or milk replacer for the next weeks. Ingestion of colostrum is essential for the morphological and functional development of calves. Maintaining the calves in a prolonged pre-ruminant phase (up to 3-5 months or more) is done in some European countries producing approximately 750 000 tons of veal, consumed annually in the European Union. Some dairy calves are maintained in a precursor stage for about a month and then weaned over a two-week period. At present, artificial colostration, due to the establishment of colostrum banks, is gaining more and more ground, thus giving up the direct contact of the calf with the mother.
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