The effect of feeding low-phytate barley-soybean meal diets differing in protein content to growing pigs on the excretion of phosphorus and nitrogen

¹ Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5
² Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5; Instituto de Ciencias Agrícolas, Universidad Autónoma de Baja California, Mexicali, México 21100
³ Instituto de Ciencias Agrícolas, Universidad Autónoma de Baja California, Mexicali, México 21100

^* To whom correspondence should be addressed. E-mail: miguel_cervantes{at}uabc.mx.

	Abstract

An experiment was conducted with growing pigs to determine the excretion of P and N in 4 barley-based diets formulated to contain 18 or 15% CP by using a normal barley (NB) or a low-phytate barley (LPB). The NB contained 0.31% total P and 0.19% phytate P; the LPB contained 0.32% total P and 0.01% phytate P. The diets were supplemented, when so required, with lysine, methionine, threonine, and tryptophan to meet their apparent ileal digestible supplies according to NRC (1998). The diets containing NB were supplemented with inorganic P to meet the NRC (1998) recommendation for available P (0.23%). The diets containing LPB were not supplemented with inorganic P as these contained sufficient available P (0.27%). Eight barrows, average BW of 20.9 kg, were assigned to the 4 dietary treatments according to a repeated 4 x 4 Latin square design. The diets were fed at a rate of 2.5 times the ME requirement for maintenance. The barrows were fed twice daily, at 0800 and 1500, equal amounts each meal. Water was added to the feed at a ratio of 2.5 to 1. Each experimental period consisted of a 7-d adaptation period followed by a 5-d collection of feces and urine. The substitution of NB with LPB decreased (P < 0.001) the total P excretion by 38 and 43% for the 18 and 15% CP diets, respectively. Reducing the CP content from 18 to 15% decreased (P < 0.001) the N excretion by 29 and 32% for the NB and LPB diets, respectively. With the reduction in CP content, there was a decrease (P < 0.001) in the amount of N retained. The N:P ratio in manure of pigs fed the LPB diets was higher (P < 0.001) than from pigs fed the NB diets. These data indicate that P and N excretions can be greatly reduced by substitution of NB by LPB, and by the reduction of the CP content, respectively, in diets for growing pigs.

Key Words: low-phytate barley, nitrogen, phosphorus, pigs

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