Studies of the skeleton of the sheep. III. The relationship between phosphorous intake and resorption and repair of the skeleton in pregnancy and lactation

Abstract

With Plates 1, 2 and 3 and Two Text-figures)In Part II of this series an experiment was described in which the amounts of mineral matter withdrawn from the skeleton during pregnancy and lactation and the proportion recovered during a subsequent dry period were determined (Benzie, Boyne, Dalgarno, Duckworth, Hill & Walker, 1956). Radiological observations of the skeletons were made, and these, together with the results of bone analyses were compared with changes in serum calcium values. The experiment reported here was similar to that reported in Part II except for the basal diet which was designed to provide a low-phosphorus intake instead of the low-calcium intake of Part II. METHODSThe plan of this experiment is set out in Table 1. The basal ration was designed to provide between 1-0 and 1-5 g. of phosphorus daily. This was converted to a ration of moderate phosphorus content by adding 3-0 g. of phosphorus (as disodium hydrogen phosphate) daily. The two contrasting types of ration are referred to below as ' low -phosphorus' and 'moderate-phosphorus' rations, respectively.Sixty Cheviot ewes, of 3£ years of age, were randomized according to live weight and date of tupping into six groups, each of ten ewes. Cast ewes were not used, and care was taken to ensure that all animals had sound mouths at the beginning of the experiment to permit observation of the effect of resorption of mandibular bone on the mobility of the incisors.The basal diet for most of the experimental period was 100 g. daily of chopped oat straw and 800-1400 g. daily of concentrates. The concentrate mixture fed during the first part of the experiment consisted of 79 % dried sugar-beet pulp, 10 % maize gluten meal, 8 % maize meal, 1 % blood meal, 1 % meat meal and 1 % common salt. Two ml. of codliver oil were poured on to the daily concentrate ration of each ewe. Because of the low energy value and rather poor palatability of this mixture, certain modifications in the diet were necessary. During late gestation, ewes that began to refuse food were given a small amount of chopped turnip (1-2 lb. daily) until appetite improved. These quantities were very small when calculated as a daily intake of air-dry material over the whole experiment. In early lactation the concentrate mixture was modified slightly, maize meal being replaced by a larger amount of flaked maize, maize gluten meal being increased and dried sugar-beet pulp being reduced by a corresponding amount. The new mixture was 70 % dried sugar-beet pulp, 12 % maize gluten meal, 15 % flaked maize, 1 % blood meal, 1 % meat meal and 1 % common salt. Also in early lactation fresh potatoes were introduced, 600 g. being fed daily for about 10 weeks. All feedingstuffs were analysed for calcium and phosphorus content.

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

“…This contrasts to the work by Benzie et al (1959) with lactating sheep, in which up to proportionally 0.4 of skeletal ash reserves were resorbed by mid-lactation with P-deficient diets. This study was not specificially designed to monitor changes in bone mineral content with stage of lactation, with the majority of bone samples removed from cows in late lactation.…”

Influence of the Stage of Dairy Cow Reproduction Cycle on Some Clinico-biochemical Parameter

“…These results that could be regarded as changes induced the the lactation stage are in accordance with the findings of Duckworth and Hill (1953), Benzie et al (1956Benzie et al ( ,1959, IIlek et al (1977). It can be concluded from the presented observations that the onset oflactation or its late stage induces the increased demineralization of the skeleton.…”

Factors affecting the faecal P status of lactating beef cattle in Northern Australia

“…It has been suggested that these animals had depleted body reserves to their full extent and so accommodated the shortage of dietary P by reducing P in milk (Dixon and Coates, 2010). The amount of P that can be mobilised from bones is estimated to be up to 30% (Benzie et al, 1959;Little, 1983) of an animal that has undergone full P-repletion. A 400kg animal would be expected to have about 2.5-3kg P in bone reserves (Dixon and Coates, 2010) a 30% mobilisation would therefore be 750-900g P. In northern Australia, beef breeding females are normally required to lactate for 4 to 6 months.…”

“…P h i l . -W h i t n e y D o l l e m o r e -4 1 0 1 4 8 8 6 The repletion of bones occurs when nutritional demand is lowered or quality is improved as demonstrated by Benzie et al (1959) using differences in ash content in sheep bones. Bortolussi et al (1999) found steers given high P diets deposited 7-17g P/day into body reserves even though the ME content of the diet was only sufficient for small amounts of growth.…”

“…long-term before slaughter and directly measure the amount of P and Ca in the bone and soft tissues (Benzie et al, 1959). Due to excessive cost, the practice was limited to the measurement of selected bones post-slaughter (Williams et al, 1990;Williams et al, 1991;Pfeffer et al, 1995;Erickson et al, 2002).…”