Phosphorus studies in pigs. 2. Assessing phosphorus availability for pigs and rats.

Experiments were conducted with pigs and rats to determine the availability of P in feeds. Initially, the availability of P in a soya-bean meal and field peas (Pisum sativum cultivar Early Dun) was assessed using a slope-ratio assay for grower pigs. Three different levels of either monosodium phosphate (MSP), soya-bean meal or field peas were added to a basal sucrose-soya-bean meal diet (2.5 g/kg P) to give three levels of P (3.0, 3.5 and 4 g/kg) for each source. The diets were offered for 35 d at three times maintenance energy requirements to female pigs initially weighing 20 kg live weight. Several bone variables and the ash and P concentration and retention levels in the empty body were used as criteria of availability. The responses to MSP were linear for all variables. However, responses to P in the test proteins, particularly soya-bean meal, were mostly non-linear, except for ash and P concentrations and retentions in the empty body. The estimates of P availability in the soya-bean meal and in the field peas were dependent on the criteria used to assess availability. Using bone variables as the criterion, the availabilities of P in soya-bean meal and field peas were approximately 0.17 and 0.38 respectively. Using ash or P concentrations or retentions in the empty body as the response criterion, the availabilities of P in soya-bean meal and field peas were 0.61 and 0.38 respectively. The mean retention values for P from MSP, soya-bean meal and field peas were 0.74, 0.33 and 0.21 respectively. Experiments were then conducted to define the conditions necessary for a slope-ratio assay for P availability with growing rats to determine if they could be used as a model to assess P availability for pigs. These experiments examined level of P in the diet, the effect of Ca:P ratio and criteria for assessing response (growth rate, feed intake, feed conversion ratio, bone ash and bone bending moment). The results indicated that a suitable range of dietary P for a slope-ratio assay in rats was 1.8-3.5 g/kg, with Ca:P ratio of between 1.3 and 6.2, and that ash content or bone bending moment of the femur bone were suitable criteria of response. However, using bone bending moment as the criterion of response, the availability of P in soya-bean meal was 0.81, which was considerably higher than the estimate with pigs.(ABSTRACT TRUNCATED AT 400 WORDS)

Phosphorus studies in pigs. 3. Effect of phytase supplementation on the digestibility and availability of phosphorus in soya-bean meal for grower pigs.

Two experiments were conducted (1) to determine the effects of phytase (EC 3.1.3.26) on the digestibility and availability of P in soya-bean meal for growing pigs and (2) to compare growth v. digestibility variables for assessing the availability of P. In the first experiment the effect of phytase on P availability was assessed in a growth assay using a slope-ratio design of treatments. Two different levels of either monosodium phosphate (MSP) or soya-bean meal were added to a basal sugar-soya-bean-meal diet (2.5 g P/kg) to give two levels of P (g/kg): 3.25 and 4.0 for each source. An additional five diets were supplemented with phytase. The ten diets were offered ad lib. for 35 d to female pigs initially weighing 20 kg live weight. In addition, the relative effectiveness of different variables for assessing P availability were compared: bone bending moment, ash in various bones, and ash and P in the empty body. The addition of phytase increased growth rate (g/d) (741 v. 835; P < 0.05), lowered the food conversion ratio (2.37 v. 2.16; P < 0.01), and increased protein deposition (g/d) (108 v. 123; P < 0.05), protein retention (kg/kg) (0.33 v. 0.36; P < 0.05), energy retention (MJ gross energy/MJ digestible energy) (0.36 v. 0.38; P < 0.05) and the availability of P in soya-bean meal from 0.11 to 0.69 when bone bending moment was the criterion of availability. All other criteria for assessing availability were unsuitable. In the second experiment the availability of (P) in soya-bean meal was assessed in a digestibility experiment with grower pigs using diets 1-5 as for Expt 1 arranged in a slope-ratio design of treatments. In addition, the effects of phytase supplementation on the apparent digestibility of P, dry matter, crude protein (N x 6.25) and energy were determined. The diets were offered at three times maintenance energy requirements to male pigs initially weighing approximately 30 kg live weight and total collection of faeces was conducted over a 10 d period. The availability of P in the soya-bean meal was 0.66 using digestible P intake as the criterion of response. The apparent digestibility of P in soya-bean meal was 0.42. Phytase supplementation increased the apparent digestibility of soya-bean meal P to 0.69 (P < 0.01) but had no effect on the faecal digestibility of dry matter or crude protein.(ABSTRACT TRUNCATED AT 400 WORDS)

Production responses to internal parasite control in dairy cattle.

A significant increase in milk production, averaging 164 litres per cow per lactation (a 4.8% increase), was seen after cows infected with gastrointestinal nematodes, paramphistomes and Fasciola hepatica were treated with broad-spectrum anthelmintics. Three hundred and ninety pairs of cows from eight herds with year-round calving were studied. One cow in each matched pair was given 7.5 mg/kg fenbendazole, 7.5 mg/kg levamisole hydrochloride and 15 mg/kg oxyclozanide in March, May and August of one year; the other cow in the pair received no anthelmintic. The number of nematode and trematode eggs was significantly decreased in the faeces of treated cows.

The New South Wales mastitis control program. 3. The effect on production and economics.

A mastitis control program carried out in 35 commercial dairy heards over three years increased the milk produced by 343 kg per cow per year and the amount of butterfat by 15.8 kg per cow per year, giving a net benefit of $16.10 per cow per year by the end of the third year. The net benefit is considerably understated since benefits other than the increase in milk production were not quantified. The overall disposal rate of 33 herds showed a drop from 19.3% in year 1 to 13.6% in year 3. An analysis of culling records showed that as the severity of mastitis increased so did cow age.