Effect of supplemental dietary slow‐release urea on growth performance and physiological status of dairy heifers |
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| Authors: | Jiaojiao Zhang Qiang Qiu Zhanhuan Shang Shujie Liu Allan Degen Shanshan Li Qi Yan Weiwei Wang Xiaoping Jing Yanfu Bai Luming Ding |
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| Affiliation: | 1. State Key Laboratory of Grassland Agro‐Ecosystem, Institute of Arid Agroecology, School of Life Sciences, Lanzhou University, Lanzhou, China;2. National Key Laboratory of Cultivating Base of Plateau Grazing Animal Nutrition and Ecology of Qinghai Province, Qinghai Academy of Animal and Veterinary Sciences, Xining, China;3. Desert Animal Adaptations and Husbandry, Wyler Department of Dryland Agriculture, Blaustein Institues for Desert Research, Ben‐Gurion University of Negev, Israel |
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| Abstract: | We examined the effect of supplemental dietary slow‐release urea on the growth performance and physiological status of 16 dairy Holstein heifers (10 months of age, 322 ± 10 kg). The heifers were offered a formulated isocaloric and isonitrogenous 70:30 roughage : concentrate ration and were assigned randomly to one of four levels of slow‐release urea supplementation (0% [U0], 1% [U1], 1.5% [U1.5] and 2% [U2] dry matter [DM]). The total study lasted 95 days, which included a 20 days adaptation period. Dry matter intake (DMI) of U2 was lower than the intakes of U0 and U1 (p < .05), while average daily gains (ADG) of U1 and U1.5 were higher than U0 and U2 (p < .05). Rumen volatile fatty acids concentration did not differ among the four treatments, while ammonia nitrogen concentration increased with an increase in urea level (p < .05). Serum blood urea nitrogen concentration was lower in U1.5 than in U0 and U2 while serum free fatty acids concentration in U2 was higher than in the other three treatments (p < .05). We concluded that the addition of urea at a level of 1.5 to 2.0% DM resulted in a reduction in DMI but the addition of 1.0%–1.5% urea resulted in the highest ADG, with no negative effects on rumen fermentation and health status of the calves. |
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| Keywords: | blood biochemical indices dairy heifer dry matter intake growth performance slow‐release urea |
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