Abstract
Weaning stress affects the health and performance of calves. L-glutamine (L-Gln) is commonly used as a functional antioxidant and energy supplement in the body. However, dietary L-Gln supplementation improving weaning stress of calves is unclear. Thus, we aimed to explore the effects of L-Gln (provided by rumen-protected L-Gln) on calves during weaning. Seventy-five Holstein calves (54.0 ± 2.68 kg; 42 ± 2.1 d of age) were assigned to five groups: no supplementation and L-Gln with 1%, 2%, 3%, and 4% dry matter daily intake (DMI) supplementation groups, respectively. The experiment lasted for 28 days (42–70 d of age of calves), and the calves were weaned at 15 d of experiment. DMI and body weekly weight of all calves were recorded. Blood samples of nine healthy calves with similar body weight were collected from each group at 0, 7, 14, 16, 18, 21, and 28 d of experiment for detecting serum L-Gln, glucose, insulin, urea nitrogen, D-lactate, cortisol, haptoglobin, interleukin-8, immunoglobulin (Ig) G, IgA, IgM, total antioxidant capacity, superoxide dismutase, glutathione peroxidase, catalase, and malondialdehyde. At the end of the experiment, six healthy calves with similar body weight from each group were selected for slaughter and morphological analysis of small intestine tissue. The results showed that the L-Gln supplementation in the diets improved the negative effects of sudden weaning in calves. Furthermore, compared to the higher-level L-Gln supple-mentation (3 and 4% of DMI) groups, the dietary lower-level L-Gln supplementation (1 and 2% of DMI) had higher average daily gain, glutathione peroxidase and IgG concentration, and villus height/crypt depth of the duodenum and jejunum, as well as lower cortisol, haptoglobin, and interleukin-8 concentration of weaned calves. These results provided effective reference for relieving the negative effects of calves during weaning.
Highlights
With increasing quantity of L-Gln added to the diet, the body weight of the calves in the 4-week experimental period had a quadratically increasing tendency, whereas
We found that L-Gln supplementation significantly enhanced the DMI, and the DMI had a linear increase during the pre-weaning period and total experimental period
The results of this study provide evidence that the addition of L-Gln in the diet improved the negative effects of sudden weaning in calves
Summary
In large-scale dairy farms, calves weaning as early as possible is necessary without negative effects. Does it increase the amount of milk available for human consumption, but it improves dairy management and increases cow reproductive efficiency [1,2]. Early weaning can result in significant physical and psychological damage to calves, producing weaning stress [3]. It is well known that weaning stress can reduce feed intake and damage the small intestinal structure of calves, which affects their productive capacity in adulthood [4–6]. It is well known that weaning stress can reduce feed intake and damage the small intestinal structure of calves, which affects their productive capacity in adulthood [4–6]. 4.0/).
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