Effect of offering dairy cows diets differing in phosphorus concentration over four successive lactations: 2. Health, fertility, bone phosphorus reserves and nutrient utilisation

Abstract

This experiment examined the long-term effects of offering diets containing low levels of dietary phosphorus (P) on dairy cow health, fertility and bone composition, and the effect of dietary P level on nutrient utilisation. One hundred winter-calving Holstein-Friesian dairy cows were offered diets containing either 'high' or 'low' levels of dietary P over a 4-year period. Rations offered during the winter included grass silage, maize silage (70 : 30 dry matter (DM) basis, approximately) and concentrates (10.0 to 12.0 kg/cow per day). During the summer periods in years 1 and 2, half of the cows grazed both day and night, while the remaining cows grazed by day, and were housed by night and offered grass silage. During years 3 and 4, all cows grazed both day and night during the summer period. Concentrate feed levels during the summer periods were 3.0 to 4.0 kg/cow per day. Different dietary P levels were achieved by offering concentrates containing either high or low P levels during the winter period (approximately 7.0 or 4.4 g P/kg DM, respectively) and during the summer period (approximately 6.8 or 3.6 g P/kg DM, respectively). Total ration P levels averaged 4.9 and 3.6 g P/kg DM for the high and low P winter diets, respectively, and 4.2 and 3.6 g P/kg DM for the high and low P summer diets, respectively. A total of 95, 70, 50 and 22 cows completed each of lactations from 1 to 4, respectively. Neither the incidence of lameness or mastitis, or milk somatic cell count, were affected by dietary P level (P . 0.05), while none of the fertility parameters recorded in any of lactations from 1 to 4 was affected by the dietary P level (P . 0.05). Dietary P level had no effect on the specific gravity, ash or calcium content of rib cortical bone cores (n 5 78 cows), while the P content of cortical bone (g/kg fresh, g/kg DM and mg/ml fresh bone) was lower with cows offered low P diets (P , 0.05). Dietary P level had no significant effect on the digestibility of either the DM, nitrogen, energy or acid detergent fibre fraction of the diet (P . 0.05), while faecal P excretions were reduced by a mean of 27 g/cow per day with cows offered the low P diets during the winter period. The results of this study indicate that dietary P levels can be reduced to proportionately 0.8 (approximately) of current UK feeding standards (Agricultural and Food Research Council, 1991), with no detrimental effect on dairy cow health or fertility, while having only minor effects on bone composition.Keywords: dairy cows, phosphorus, fertility, bone, nutrient utilisation ImplicationsThis study examined the impact of offering reduced phosphorus diets over a 4-year period on cow fertility and bone phosphorus status. Within this long-term study, no detrimental effects on either parameter was observed when a diet containing approximately 20% less phosphorus than recommended within the current UK feeding standards was offered. Offering a low phosphorus diet significantly reduced the quantity of phosphorus excreted in faeces.

The effect of dietary crude protein and phosphorus on grass-fed dairy cow production, nutrient status, and milk heat stability

“…In the present study, daily fecal P excretion was significantly lower in the LPrLP treatment compared with the other 3 treatments. This agrees with Valk et al (2002) and Ferris et al (2010), who also found that daily fecal P excretion was reduced when a lower dietary P concentration was offered.…”

“…Urine only becomes a significant excretory route for P when diets contain excessively high concentrations of P (Ferris et al, 2010), which was not the case in the present study. Therefore, the lack of an effect of treatment on urinary P excretion in the present study is not surprising.…”

“…The 0.24% DM P treatment had a significantly lower milk yield than the 0.28 and 0.33% DM P treatments. Ferris et al (2010) conducted a study in which dietary P concentrations of 0.49% DM and 0.36% DM were offered to dairy cows over 4 successive lactations. No difference between treatments was observed in milk yield 529 or composition.…”

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

“…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.…”

A rapid and multi-element method for the analysis of major nutrients in grass (Lolium perenne) using energy-dispersive X-ray fluorescence spectroscopy

“…Dairy cows have a high dietary requirement for P, approximately 0.36% dry matter (DM) and P deficiencies such as aphosphorosis are likely if P values in feed fall below 0.20% DM (Coulter and Lalor, 2008;Ferris et al, 2010;Reid et al, 2015). As an essential nutrient for plant nutrition, Mg levels in grass can be indicative of animal intake as poor absorption of Mg by cows (only 20-25% of intake is ingested) requires a minimum requirement of 0.20% DM to prevent Mg deficiency known as grass tetany (NRC, 2001).…”