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

J Htoo,W Sauer,Y Zhang,S Liao,M Cervantes,B Araiza

doi:10.22358/jafs/66726/2007

Abstract

Instituto de Ciencias Agricolas, Universidad Autonoma de Baja CaliforniaMexicali, Mexico 21100(Received 31 July 2006; accepted 2 February 2007)ABSTRACTAn 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 hulless barley (HB) or a low-phytate hulless barley (LPHB). The HB contained 0.27% total P and 0.14% phytate P; the LPHB contained 0.24% total P and 0.03% phytate P. The diets were supplemented with lysine, methionine, threonine, and tryptophan to meet their apparent ileal digestible supplies according to the National Research Council (NRC). All diets were supplemented with inorganic P to meet the NRC recommendation for available P (0.23%). Eight barrows, average body weight 20.4 kg, were assigned to the 4 dietary treatments according to a repeated 4 × 4 Latin square design. The diets were fed at a rate of 2.5 the ME requirement for maintenance. The barrows were fed twice daily, at 8 a.m. and 4 p.m., 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 faeces and urine. The substitution of HB with LPHB decreased (P<0.001) the total P excretion by 33.5 and 35% for the 18 and 15% CP diets, respectively. Reducing the CP content from 18 to 15% decreased (P<0.001) the N excretion by 26% for both the HB and LPHB diets. With the reduction in CP content, there was a decrease (P<0.001) in the amount of N retained. The N:P ratio in excreta of pigs fed the LPHB diets was higher (P<0.001) than of pigs fed the HB diets. The digestibility of N was higher (P<0.001) in pigs fed the LPHB compared to the HB diets. The data indicate that P and N excretions can be greatly reduced by substitution of HB by LPHB, and by the reduction of the CP content, respectively in diets for growing pigs.KEY WORDS: pigs, phosphorus, nitrogen, balance, low-phytate barley

Highlights

Barley is a commonly used feed ingredient in diets for growing and finishing pigs in western-Canada and many countries
The apparent total tract digestibility (ATTD) and retention of P were higher for pigs fed the low-phytate hulless barley (LPHB) compared to the hulless barley (HB) diets (Table 3)
The ATTD and retention of P were higher, the amount of P retained was lower for pigs fed the LPHB than the HB diets

Summary

Introduction

Barley is a commonly used feed ingredient in diets for growing and finishing pigs in western-Canada and many countries. It ranks fourth after wheat, rice and maize in world cereal production (FAO, 2002). Two thirds of phosphorus (P) in commonly used feed ingredients of plant origin, including barley, is present in the form of phytate (Ravindran et al, 1995). Most of the phytate P is excreted and can lead to environmental pollution. Phosphorus from animal manure is becoming an increasing environmental concern in many countries (Jongbloed and Lenis, 1998). There is more and more interest in nutritional strategies to minimize P excretion in manure

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