A study was conducted to evaluate the effects of tannin (0, 5, 15, 20 and 25 g kg −1 diet) and a microbial enzyme supplement (MES) on the feed consumption, body growth and digestive physiology of broiler chickens between hatch and 22 days of age. Feed intake, body weight and body weight gain declined (p < 0.001) with an increase in dietary tannin content. Feed conversion efficiency was increased (p < 0.001) in line with dietary tannin level, up to 15 g kg −1 diet. There were no significant effects of dietary treatment on the protein content of pancreatic tissue or activities of pancreatic and jejunal enzymes. The ileal digestibilities of energy, protein, arginine, alanine and leucine were reduced (p < 0.001) as dietary tannin level rose to 20 g kg −1 diet and beyond. The digestibilities of methionine and phenylalanine were also negatively affected (p < 0.01) at the highest level of dietary tannins, while phosphorus digestion was improved (p < 0.05) on diets containing tannin. Apart from an increase (p < 0.01) in the protein content of the jejunal mucosa of birds on the diet with 20 g tannin kg −1 diet, there were no significant effects of the MES on most of the variables assessed. The results demonstrate the negative effects of tannin, especially at high levels of inclusion in the diet. However, neither tannins nor MES influenced the activities of digestive enzymes assessed, suggesting that a wider range of factors may be involved in regulating the effects of tannins on poultry.

-A study was conducted to evaluate the effects of varying drying temperature (Fresh, 85, 95 or 105 o C) on the nutritive value of maize and response of broiler chickens to diets based on such grain, and supplemented with a microbial enzyme (Avizyme 1500). The chemical composition of the grain was affected by drying temperature. Starch and amylopectin contents were increased while there was a reduction in amylose content. These changes were expected to underlie the response of chicks to the diets. Total feed intake over 28 days was increased (P < 0.05) as a result of heat-treating the maize up to 95 o C. The final body weight of chicks on the diet based on fresh maize was improved (P < 0.05) by the microbial enzyme supplement (MES). There was no effect of the enzyme supplement on body weight when assessed at earlier ages. Over the entire feeding period, feed conversion efficiency (FCE) declined (P < 0.001) with increasing oven temperature, regardless of the supplementation with the microbial enzyme. Body weight was influenced (P < 0.05) by the microbial enzyme only when assessed over the entire trial period. The weight of visceral organs, protein content and activities of pancreatic and jejunal digestive enzymes were unaffected by grain heat treatment or MES. The ileal digestibility of calcium was reduced (P < 0.001) on diets based on fresh maize and maize that was oven-dried at 105 o C. Heat-treatment also improved (P < 0.05) the ileal digestibility of phosphorus in chicks on the diets without MES. There were no effects of grain heat treatment or MES on the ileal digestibility of energy, protein, Ca and amino acids. The results indicate some variations in grain quality as a result of heat treatment but the differences were not significant enough to stimulate major responses to the MES. Further studies should examine samples from commercial drying processes or samples obtained from a closer simulation of commercial conditions, to arrive at more practical conclusions.body growth / broiler chicks / digestibility / digestive enzymes / drying temperature / grain quality / maize Reprod. Nutr. Dev. 43 (2003) 77-90 77

The milk production of 63 5-year-old Merino ewes was measured over a 16-week period after lambing. The purpose was to find a suitable mathematical model to represent the lactation curve of Merino sheep and to estimate the parameters of the model for an individual ewe from a single data point in early lactation. Three models were considered, the three-parameter Wood model, yn = nb exp(a + en), the four-parameter Morant model, yn = exp(a + bn + en2 + d/n and the six-parameter Grossman model, yn = a1b1 - [tanh2 (b1n - c1))] + a2b2[1 – tanh2 (b2(n -c2,))].The Grossman model was found to be inappropriate for the available data, while there seems to be little difference in the suitability of the other two models. The Wood and Morant models both seem adequate to represent the lactation curve. A pattern in the estimated residuals suggests possible autocorrelations in the errors, but this is inconclusive due to the limited number of data points per animal.The correlation between the estimated parameters of the model and the daily yield measured during the 1st week of lactation enabled us to use linear regression to estimate the lactation curve of an individual animal based on the 1st week's yield. Confidence and prediction intervals for the yield during the rest of the lactation period may then also be constructed. This makes it possible to extend incomplete milk records for use in genetic evaluation, formulation of rations and economic evaluations.

No abstract

Bayesian theory is applied to compare the characteristics of the estimated lactation curves of two groups of 5-year-old Merino ewes. The diets of the two groups were supplemented respectively by DL-methionine and maleyl-DLmethionine. The purpose is to illustrate the Bayesian approach when analysing for the effect of supplement on the lactation pattern of the sheep. Using Wood's model, the posterior distributions of the model parameters are determined for the two groups. This is achieved by assuming a hierarchical Bayes model and applying the Gibbs sampler, a sampling based computer intensive algorithm that is very efficient in obtaining marginal distributions of functions of parameters. The Gibbs sampler enables us to obtain marginal posterior distribution of characteristics of the lactation curve such as peak yield, time of peak yield, persistency and total milk yield. The results are notable differences in the marginal posterior distributions of mean peak milk yield and mean total yield. The posterior probability that the mean peak milk yield of the group supplemented by maleyl-DL-methionine is higher than that of the group with DL-methionine supplement is 0·98, while the same probability for mean total yield is 0·83.