Shredded beet pulp substituted for corn silage in diets fed to dairy cows under ambient heat stress: Feed intake, total-tract digestibility, plasma metabolites, and milk production.
The effects of substituting increasing concentrations of dried, shredded beet pulp for corn silage on dry matter intake, nutrient digestibility, rumen fermentation, blood metabolites, and milk production of lactating dairy cows was evaluated under conditions of ambient heat stress. Four multiparous (126±13d in milk) and 4 primiparous (121±11d in milk) Holstein cows were used in a 4×4 Latin square design experiment with 4 periods of 21d. Each period had 14d of adaptation and 7d of sampling, and parity was the square. Dietary treatments were (dry matter basis): 16% of dietary dry matter as corn silage without BP (0BP, control diet); 8% corn silage and 8% beet pulp (8BP); 4% corn silage and 12% beet pulp (12BP); and 0% corn silage and 16% beet pulp (16BP). Alfalfa hay was included in all diets (24% dietary dry matter). Dietary concentrations of forage neutral detergent fiber and nonfiber carbohydrates were 21.3 and 39.2% (0BP), 16.5 and 40.9% (8BP), 14.1 and 42.2% (12BP), and 11.7 and 43.4% (16BP), respectively (dry matter basis). The ambient temperature-humidity index indicated that the cows were in heat stress for almost the entire duration of the study. Dry matter intake and nutrient digestibilities were similar across treatments and between multi- and primiparous cows. Mean rumen pH tended to decrease with increasing proportions of beet pulp in the diet. Also, increasing proportions of beet pulp in the diet linearly decreased acetate and butyrate concentrations in the rumen and increased propionate concentrations, leading to a linear decrease in acetate:propionate ratio. Milk yield linearly increased (38.5, 39.3, 40.9, and 39.6kg/d for 0BP, 8BP, 12BP, and 16BP, respectively), but fat content linearly decreased (3.46, 3.47, 3.27, and 2.99), such that we observed no effect on fat-corrected milk. Substituting beet pulp for corn silage increased the neutral detergent insoluble crude protein content of the diet, leading to a decrease in rumen concentration of ammonia-nitrogen and milk concentration of urea, corresponding to an increase in percentage of protein in milk. Compared with multiparous cows, primiparous cows had greater rumen pH, metabolite concentrations in plasma (glucose, cholesterol, urea nitrogen, total protein, and globulins), milk production, and concentrations of milk components. Substituting beet pulp for corn silage at up to 12% of dietary dry matter can be beneficial during heat stress conditions.
Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran.
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Naderi
Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran.
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Ghorbani
Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran.
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Sadeghi-Sefidmazgi
Department of Animal Sciences, College of Agriculture, Tehran University, Karaj, PO Box 3158711167-4111, Iran. Electronic address: smnasrolahi@gmail.com.
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Nasrollahi
Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada T1J 4B1.
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Beauchemin
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D027461:Beta vulgaris; D002417:Cattle; D004032:Diet / Q000662:veterinary; D004043:Dietary Fiber / Q000378:metabolism; D004063:Digestion; D005260:Female; D005285:Fermentation; D006358:Hot Temperature; D007774:Lactation / Q000187:drug effects; D008892:Milk / Q000737:chemistry; D012417:Rumen / Q000378:metabolism; D012820:Silage; D003313:Zea mays / Q000378:metabolism*
beet pulp; corn silage; dairy cow; heat stress