Effect of energy and protein supplementation on phosphorus utilization in lactating dairy cows

Abstract

Two experiments were undertaken in which grass silage was used in conjunction with a series of different concentrate types designed to examine the effect of carbohydrate source, protein level and degradability on total dietary phosphorus (P) utilization with emphasis on P pollution. Twelve Holstein-Friesian dairy cows in early to mid-lactation were used in an incomplete changeover design with four periods consisting of 4 weeks each. Phosphorus intake ranged from 54 to 80 g/day and faecal P represented the principal route by which ingested P was disposed of by cows, with insignificant amounts being voided in urine. A positive linear relationship between faecal P and P intake was established. In Experiment 1, P utilization was affected by dietary carbohydrate type, with an associated output of 3.3 g faecal P/g milk P produced for all treatments except those utilizing low degradable starch and low protein supplements, where a mean value of 2.8 g faecal P/g milk P was observed. In Experiment 2, where two protein levels and three protein degradabilities were examined, the efficiency of P utilization for milk P production was not affected by either level or degradability of crude protein (CP) but a significant reduction in faecal P excretion due to lower protein and P intake was observed. In general, P utilization in Experiment 2 was substantially improved compared to the Experiment 1, with an associated output of 1.8 g faecal P/g milk P produced. The improved utilization of P in Experiment 2 could be due to lower P content of the diets offered and higher dry matter (DM) intake. For dairy cows weighing 600 kg, consuming 17-18 kg DM/day and producing about 25 kg milk, P excretion in faeces and hence P pollution to the environment might be minimized without compromising lactational performance by formulating diets to supply about 68 g P/day, which is close to recent published recommended requirements for P.

Meta-analysis of factors that affect the utilization efficiency of phosphorus in lactating dairy cows

“…This database subset comprised data from lactating dairy cows from 25 studies (Martz et al, 1990;Morse et al, 1992;Spiekers et al, 1993;Delaquis and Block, 1995;Khorasani et al, 1997;Knowlton et al, 2001Wu et al, 2001Wu et al, , 2003Knowlton and Herbein, 2002;Guyton et al, 2003;Kebreab et al, 2005;Kincaid et al, 2005;Shore et al, 2005;Wu, 2005;Ekelund et al, 2006;Kamiya et al, 2006a;Knowlton et al, 2007;Dann et al, 2008;Moreira et al, 2009;Myers and Beede, 2009;Taylor et al, 2009;Van Straalen et al, 2009;Herrera et al, 2010;Puggaard et al, 2011) and included 130 treatment means. The response variable of interest was P excretion in the feces, both in grams per day and as a fraction of P intake.…”

“…High dietary NDF levels also likely coincide with low levels of dietary starch and, in general, may be associated with a lower availability of fermentable substrate for microbes in the rumen, thus reducing P uptake by the ruminal microbes. Kebreab et al (2005) showed that type and density of energy in the feed have a significant effect on P excretion in cattle. In comparing 2 experiments with high and low energy intakes, they found that P efficiency improved significantly in cows fed a higher energy diet (consuming at least an extra 30 MJ/d).…”

“…The negative relationship between DM digestibility and P excretion in feces reported by Weiss and Wyatt (2004) support our data in this respect. However, not the absolute amount, but rather the digestive characteristics of starch may affect the efficiency of utilization of P in terms of total P excretion (g/d) and P excretion per gram of milk P produced (Guyton et al, 2003;Kebreab et al, 2005). Guyton et al (2003) studied the effect of 2 dietary P levels and 2 starch sources on fecal P excretion.…”

“…Research has shown that a positive relationship exists between P intake and fecal P excretion (Morse et al, 1992;Ekelund et al, 2005;Kebreab et al, 2005), and several short-and long-term studies with dairy cattle indicate that feeding less P can reduce fecal P excretion into the environment Wu et al, 2000;Ferris et al, 2010). However, effects of nutritional factors other than P intake on efficiency of P use are less evident from the literature and warrant further investigation.…”

Feed management practices to reduce manure phosphorus excretion in dairy cattle

“…Energy status of the animal Kebreab et al (2005a) conducted two experiments in which grass silage was used in conjunction with a series of different concentrate types designed to examine the effect of carbohydrate source, protein level and degradability on total dietary P utilization with emphasis on P pollution. The authors reported that dairy cattle excreted up to 15% less P when fed slow degradable starch sources compared with feed with high degradable starch content (Figure 1).…”