Influence of an Escherichia coli-derived phytase on nutrient utilization in broiler starters fed diets containing varying concentrations of phytic acid.

The influence of an Escherichia coli-derived phytase, on nutrient utilization was investigated in broilers fed starter diets containing different concentrations of phytate. The study was conducted as a 3 x 4 factorial arrangement of treatments with 3 concentrations of phytic acid (10.4, 11.8, and 13.6 g/kg; equivalent to 2.8, 3.3, and 3.8 g of phytate P/kg) and phytase (0, 500, 750, and 1,000 FTU/kg). One unit of phytase (FTU) is defined as the quantity of enzyme that releases 1 micromol of inorganic phosphorus/min from 0.00015 mol/L of sodium phytate at pH 5.5 at 37 degrees C. The dietary phytic acid concentrations were manipulated by the inclusion of rice bran. Increasing dietary concentrations of phytic acid resulted in reductions (P < 0.01) in AME. Phytase additions tended to increase AME (P = 0.07), regardless of dietary phytate concentrations. Apparent ileal digestibility coefficients of protein and most amino acids were influenced by phytate (P < 0.05 to 0.001) and phytase (P < 0.001). Phytase improved ileal protein and amino acid digestibility at all phytate concentrations, but the trend in responses to increasing phytase additions was different at different phytate concentrations as shown by significant phytate x phytase interactions (P < 0.01 to 0.001). At the lowest phytate concentration, the ileal digestibility coefficients increased with increasing phytase supplementation. At the medium and high phytate concentrations, the greatest responses were observed at 500 FTU/kg of phytase, with little improvement attributable to further additions. Ileal digestibility of P was lowered (P < 0.01) by increasing phytate concentrations and increased (P < 0.001) with increasing additions of phytase. A significant phytate x phytase interaction (P < 0.05) was also observed, where the improvements in P absorption with added phytase were found to be greater at high phytate concentrations. These data demonstrate the anti-nutritive effects of phytic acid and the potential of microbial phytase to improve energy utilization and the availability of P and amino acids in broilers fed starter diets.

Effects of naloxone, metaclopramide and domperidone on plasma levels of prolactin and LH following suckling in the female rabbit.

Saline, naloxone, domperidone or metaclopramide was injected into lactating rabbits immediately before suckling. Blood samples were taken prior to injection (0 minutes) and then at 15, 30, 45 and 60 minutes after the start of suckling, after which the samples were assayed for plasma prolactin and LH concentrations. In all the does there was a significant increase in prolactin concentration, which was highest 15 minutes after the start of suckling, and which declined exponentially thereafter to levels significantly higher than before suckling. The increase in prolactin concentration was similar in does given saline and naloxone, but it was significantly enhanced in does given metaclopramide; with domperidone the increase was intermediate and not significantly different from that following treatment with saline. In does given saline, domperidone, and metaclopramide plasma LH concentrations declined slowly during the hour after suckling but the concentration was increased significantly in does given naloxone. The inverse correlations between prolactin and LH were low weak and were not significant.

Effects of reducing the remating interval after parturition on the fertility and plasma concentrations of luteinizing hormone, prolactin, oestradiol-17 beta and progesterone in lactating domestic rabbits.

Primiparous crossbred does were remated on Day 1 (n = 15) or 14 (n = 25) post partum and killed on Day 10 post coitum to assess their fertility. Blood samples were taken during the pre- (0-12 h post coitum) and post- (1-10 days post coitum) ovulatory periods and plasma was assayed for luteinizing hormone (LH), prolactin, oestradiol-17 beta and progesterone. Ovulation response was significantly greater (P less than 0.01) and ovulation rate significantly lower (P less than 0.001) in does mated on Day 1 than in those mated on Day 14 post partum. Does failing to ovulate on Day 14 post partum exhibited no preovulatory LH surge and had significantly lower (P less than 0.05) premating concentrations of oestradiol-17 beta and prolactin than those ovulating at this time. No significant differences in hormone concentrations were observed during the preovulatory period between does ovulating on Days 1 and 14 post partum, with the exception of oestradiol-17 beta. Concentrations of this hormone were significantly lower (P less than 0.01) in does mated on Day 1, at 1 h post coitum. We conclude that (i) fertility was affected by the remating interval after parturition, (ii) ovulation failure was associated with an absence of the preovulatory LH surge and a reduction in premating concentrations of oestradiol-17 beta and prolactin and (iii) the lower ovulation rate in early lactation was apparently caused by a reduction in ovarian competence to respond to the gonadotrophic stimulus.

Cassava root meal in diets for growing rabbits.

The effects of substituting imported cassava root meal for barley meal in rations for growing rabbits were examined. Four diets were used. Diet 1 contained 500 g/kg barley meal, the remainder of the diet consisted of soya bean meal, barley straw, vitamins and minerals. Diets 2, 3 and 4 contained increasing amounts of cassava root meal in place of barley meal at 165, 335 and 500 g/kg respectively with L-lysine and DL methionine supplements. A growth trial was carried out using 48 individually caged rabbits from 0.8 kg to 2.0 kg and the digestibilities of the diets were determined in balance trials. Growth rates were similar on all treatments (41.6, 43.1, 40.6 and 41.0 g/d respectively, s.e.d. 2.39), as were dry matter food conversion ratios (2.27:1 overall). The cassava meal appeared to have a digestible energy approximately 1.6 MJ/kg DM higher than that of the barley meal. There appeared to be no adverse effects of feeding diets containing 500 g/kg cassava root meal on animal health. The intrinsic variability in chemical composition of cassava root products is discussed.

Fertility of the early postpartum, lactating domestic rabbit.

Sixty-four crossbred primiparous lactating does each suckling six pups were allocated at random into four groups and were mated on either Day 1, 2, 3, or 4 post partum (where Day 0 = the day of parturition). They were subsequently killed on Day 10 post coitum (where Day 0 = the day of mating) to assess fertility. There were no significant differences between treatment groups in their mating response (97% overall), ovulation response (77% overall), implantation response (83% overall), implantation rate (8.7 overall), or preimplantation mortality rate (24% overall). Ovulation rate was significantly increased in does mated on Days 3 and 4 (13.3 and 13.1, respectively), compared with those mated on Day 1 (10.2, P<0.05) and Day 2 (9.6, P<0.01) post partum. From these results we conclude that fertility is high throughout the early postpartum period in the lactating rabbit.

Energy and nitrogen metabolism of rabbits during pregnancy, lactation, and concurrent pregnancy and lactation.

1. In an experiment twenty-four cross-bred does were used, six in each of four physiological states: non-pregnant (NP), pregnant (P), lactating (L) or concurrently pregnant and lactating (CPL). They were offered a diet of high nutrient density (crude protein (nitrogen x 6.25) 272 g/kg dry matter (DM), metabolizable energy 15.5 MJ/kg DM) at one of two intakes on a scale based on metabolic body-weight (kg body-weight 0.75). The study lasted for 24 d and was divided into three consecutive 8 d periods: 'early', 'mid-' and 'late' pregnancy or lactation, or concurrent pregnancy and lactation. 2. Around the mid-point of each period the does were placed for 24 h in a gradient-layer calorimeter, and measurements of energy exchange were made. N balance was also measured throughout each period of the study. 3. Milk output in L and CPL does was measured by weighing the does immediately before and after suckling once each day. Milk samples were taken from a parallel group of does and the estimates of milk composition applied to the experimental group. 4. Milk yields and composition were similar for L and CPL does in early and mid-lactation, but in late lactation the milk output from CPL does declined rapidly. This was the period of maximal fetal growth rates. Energy and N retention increased in P and CPL does in late pregnancy. 5. Regression analysis was carried out to summarize the relations between metabolizable energy intake (MEI) and energy retention (ER; MEI-heat loss) in each physiological state. The equations were: NP: ER = 0.67 (SE 0.057) MEI-208, P: ER = 0.67 (SE 0.095) MEI-224, L: ER = 0.90 (SE 0.022) MEI-441, CPL: ER = 0.85 (SE 0.036) MEI-387, where all variables are expressed in kJ/kg body-weight 0.75 per d.

Energy and nitrogen metabolism of lactating rabbits.

Twelve crossbred does (New Zealand White x California) were offered a diet of high protein and metabolizable energy content (249 g/kg dry matter (DM) and 13.6 MJ/kg DM respectively) throughout a 32 d lactation at one of four feeding levels (240, 280, 320 or 360 g/d). Each feeding level was replicated three times. Milk output was measured by weighing the does before and after their one daily suckling period. The lactation was divided into four consecutive 8-d periods. Each doe was placed in a direct calorimeter for 48 h around the mid-point of each of these periods and measurements of energy exchange were made. Nitrogen balance was also measured throughout the study period. Milk samples were taken from a parallel group of animals and the estimates of milk composition were applied to the main group of does. From the second period of lactation onwards nearly all does mobilized body tissue to support milk energy secretion, although there was no loss of weight. Multiple regression analyses were used to examine the apparent efficiency with which metabolizable energy and body-tissue energy were utilized for milk production. Overall, the relationship was described by the equation: (formula; see text) where Milk E is the milk energy output, ME intake is the metabolizable energy intake and Body ER is the body energy retention, all expressed in kJ/kg body-weight0.75 per d. All does appeared to be in positive N balance throughout lactation on this high-protein diet.

Vitamin K deficiency syndromes in warfarin-resistant brown rats (Rattus norvegicus).

Resistance to the anticoagulant rodenticide warfarin and an increased vitamin K requirement appear to be pleiotropic effects of the gene Rw2. A comparison of pup mortality in F2 (Rw1Rw2 x Rw1Rw2) and backcross (Rw1Rw2 x Rw1Rw1 or reciprocal) matings of wild brown rats in the laboratory revealed significantly greater losses in the F2 litters at 4-8 weeks of age. Some deaths could be attributed directly to haemorrhage resulting from vitamin K deficiency. A newborn warfarin-resistant rat from an F2 litter showed bleeding from the umbilicus and the anus, and died from internal haemorrhage at 18 weeks of age. Another warfarin-resistant male rat dying at the same age had a grossly enlarged skull.

Relative fitness of genotypes in a population of Rattus norvegicus polymorphic for warfarin resistance.

Resistance to warfarin and an increased vitamin K requirement appear to be pleiotropic effects of the same allele (Rw2). In a natural population containing resistant individuals where the use of warfarin is discouraged the change in the frequency of resistance should reflect the relative fitnesses of the three possible genotypes. A large polymorphic population of rats was extensively poisoned with warfarin and the level of resistance monitored regularly for a period of 18 months after withdrawal of the poison. During this period the proportion of resistant animals in live-capture samples decreased significantly from approximately 80 per cent to 33 per cent. This decline is consistent with a hypothesis of reduced fitness of both Rw2Rw2 and Rw1Rw2 genotypes relative to Rw1Rw1 under natural conditions. The relative fitnesses of these genotypes were calculated using an optimisation method based on least squares analysis. These estimates were: Rw2Rw2 (0.46), Rw1Rw2 (0.77) and Rw1Rw1 (1.00). Homozygous resistant individuals were found in some of the samples, confirming that the Rw2 allele does not act as a recessive lethal, although it must be extremely disadvantageous. Some heterogeneity was observed in the proportion of resistant animals in samples taken from different areas of the farm building complex. This could reflect stochastic processes influencing the Rw2 allele frequency in small peripheral populations.