Brody, Gompertz, Logistic, Richards and von Bertalanffy functions were compared as descriptors of growth in 319 coypus (Myocastor coypus) of Greenland and Silver varieties, from birth to 10–19 months of age. Several criteria were considered for the selection of the model: (a) bias in the asymptotic weight; (b) bias in birth weight; (c) error sum of squares; (d) error mean squares weighted by the number of animals converging in all functions; (e) determination coefficient. To adjust the curves NLIN procedure from SAS and iterative method of Marquardt were applied. A mixed model was used to analyse the parameters of the selected growth curve (asymptotic weight, A; constant of integration, B; and maturation rate, k) which included effects of farm, variety, sex, sire within farm and variety, reproductive status within sex, birth season and first order interactions. The effect of sire was considered as random. The von Bertalanffy function was selected and mean values for the parameters of this function were 8016 g and 0·008 g/g per day, for A and k respectively. There were differences in the estimated parameters between sexes; males had larger values of A and k than females.

Weights at fixed ages (birth, weaning, 6–7 months) were analysed, as well as the final recorded weight and average postweaning gain. The model of analysis was similar to the previous one. There were no differences between varieties. Significant differences between sexes for almost all studied traits were detected. With age, weight difference between males and females increased. At 6 months of age, males were 37% heavier than females. Male average daily gain was higher than that of females, sexual dimorphism being evident in all analysed traits.

Bacterial growth inhibiting effects of dipicolinic acid (DPA), which occurs in spores of probiotic Bacillus spp. strains, was studied with a range of Lactobacillus spp. (13), Enterococcus spp. (14), and E. coli strains (8) in vitro. In vivo effects were studied in a broiler chicken nutrition trial and DPA supplemented feed (10 g/kg).

In vitro studies showed that DPA inhibited growth of most Lactobacillus spp. strains to a larger extent than E. coli strains. Enterococci were generally influenced less by DPA. However, in each group of bacteria some strains were less inhibited by DPA than others. Intestinal lactic acid bacteria in the jejunum and ileum showed a trend (P[les ]0·1) for lower counts in birds fed the DPA-supplemented feed on day 14 and 21. Counts of enterobacteria were not significantly influenced by DPA. No differences in colony counts were observed in 28-day-old animals. Digesta pH was not statistically reduced, but a lower crop pH was recorded throughout the nutrition trial.

The study showed that dipicolinic acid, present in probiotic Bacillus spp. spores, is inhibitory for in vitro growth of most lactobacilli and enterobacteria, while growth of enterococci was less inhibited. Intestinal colony counts in young broiler chickens fed a DPA-supplemented diet in part mirrored in vitro results.

Glucosinolates and their hydrolysis products are of great concern because they are responsible for many of both the beneficial and harmful properties of glucosinolate-containing plants. Cabbage (Brassica oleracea L.) is a species highly consumed as a leaf vegetable in many countries showing high qualitative and quantitative differences in glucosinolate composition among cultivars. The standard analytical techniques for determining glucosinolate composition using conventional methods lead to high costs, labour input and delays, all of which affect both the availability of data and the taking of swift decisions. In contrast, near-infrared spectroscopy (NIRS) has emerged as a rapid and cost-effective technique of analysis for many agro-food products. In this work we test the potential of NIRS for screening the total glucosinolates (t-GSL), gluconapin (GNA), gluconasturtiin (GNAST) and neoglucobrassicin (NGBS) contents of cabbage leaf cultivars coming from Portugal and Spain. NIRS calibrations resulted in coefficients of determination and standard deviation to standard error of cross-validation ratio of 0·83 and 2·38 for t-GSL; 0·70 and 1·85 for GNA; 0·62 and 1·63 for GNAST; and 0·60 and 1·58 for NGBS, respectively. An examination of the loadings of the equation for t-GSL suggested that O-H groups of water, C-H combinations of the methylene group and also N-H groups of amides were the molecular associations most strongly used in modelling total glucosinolates. It was concluded that NIRS shows a high potential as an analytical method for total and individual glucosinolate routine analysis in cabbage.

The objective of the study was to determine the in vivo relationship between the long-term administration of recombinant bovine somatotropin (rbST), circulating levels of IGF-I and insulin, mammary blood flow and other variables relevant to milk synthesis, in crossbred, Holstein cattle. Ten first-lactation, non-pregnant, crossbred, Holstein dairy cattle were divided into two groups of five animals each; an experimental group and a control group. Animals in each group were fed with rice straw, treated with 5 kg urea dissolved in 100 litres water per 100 kg dry rice straw as the source of roughage. Four consecutive study periods were carried out in each group. These consisted of a pretreatment period (45 days postpartum before lactation peak) and three treatment periods during early lactation (105 days postpartum), mid-lactation (165 days postpartum) and late lactation (225 days postpartum). During the treatment periods, animals that had completed 60 days of lactation were injected subcutaneously at fortnightly intervals with 500 mg of recombinant bovine somatotropin (rbST) (POSILAC, Monsanto, USA) in the experimental group, while animals in the control group were injected subcutaneously at fortnightly intervals with 800 mg of sterile sesame oil, without rbST, as a placebo. During the pretreatment period, there were no significant differences in plasma concentrations of IGF-I, insulin and other parameters between the control group and the experimental group. During the treatment periods, the increase in the concentration of plasma IGF-I in rbST treated animals was significantly higher than in the control animals throughout the lactation period. Plasma glucose, protein and triglyceride concentrations in each group remained stable throughout the study. The total daily dry matter intakes were not significantly different between the groups. Milk yield increased by 20% with rbST treatment and it was 22% greater than that of the control animals receiving placebo in early lactation. Milk yield of rbST treated animals rose to a peak in early lactation and then gradually declined. In late lactation, milk yield of rbST-treated animals decreased by 19% as compared with early lactation. Udder plasma flow and udder blood flow markedly increased with rbST treatment and there were no significant changes in the control animals. The ratio of udder blood flow to the rate of milk production increased in mid- and late lactation in controls and the rbST treated animals. These findings suggest that the short persistency of lactation in rbST treated animals was similar to that in the control animals receiving placebo. Changes in milk production during the progress of lactation in rbST treated animals might not be controlled systemically only but also locally within the mammary gland. The lack of effect of higher plasma IGF-I levels on persistency of lactation in rbST treated animals, may be due to changes in the pattern of IGF-I binding proteins and paracrine production inhibiting IGF-I action.

Two flocks of 42 multiparous (M) and 27 primiparous (P) Nilotic ewes (Southern Sudan) were used in an experiment conducted at the Animal Production Research Centre, Khartoum N., Sudan, to study the effect of age and diet on reproductive performance. Each age group (M and P) was subdivided into two diet groups, fed either a sorghum (So) or a molasses (Mo)-based diet. The two diets were approximately isoenergetic (12·2 and 11·4 MJ ME/kg DM for So and Mo diets, respectively) and isonitrogenous (217 g CP/kg). These diets were formulated from sorghum and groundnut cake or molasses and urea as main sources of energy and protein, respectively. Each of the four diet groups of ewes was further divided into 6 subgroups (replicates) of similar body weights housed and fed together for two successive gestation periods. The results showed that the diet treatments had no significant effect on age and weights at first oestrous (210, 238 days and 22, 20 kg) and at first lambing (407, 418 days and 30, 28 kg) of the PSo and PMo groups, respectively. Age of the ewes and the diet treatments had no significant effects (P>0·05) on feed intake, conception weight, litter size, lamb birth weight, gestation period, postpartum anoestrous period, lambing interval, sex ratio of offspring as well as conception, fertility, abortion and lambing proportions. Primiparous ewes (P) had significantly (P<0·05) higher pre-weaning lamb mortality proportion, whereas the sorghum-based diet groups had higher (P<0·05) gestation body gain and lambing weights.

It was concluded that Nilotic ewes, compared with the other African sheep breeds reviewed, reach sexual maturity at an earlier age and are highly prolific due to their short postpartum anoestrous period. The results also highlight the importance of molasses and urea as efficient and good substitutes for sorghum grains and oil cakes, respectively, in the diets of ewes.

Chemical-mutagen treatment of Ethiopian mustard (Brassica carinata A. Braun) line C-101 seeds (which contained about 441 g/kg C22[ratio ]1) led to isolation of a mutant, L-935, which contained about 190 g/kg erucic acid (intermediate C22[ratio ]1) in the seed oil. The objective was to determine the inheritance of the intermediate C22[ratio ]1 level in this mutant. The mutant L-935 was reciprocally crossed to C-101 and to the mutant line L-2890 (which contained 112 g/kg C22[ratio ]1; low). The F1, F2 and BC1F1 generations were obtained. Cytoplasmic effects were not observed in any of the crosses. The analysis of the fatty acid composition in the F2 populations from the crosses of L-935 with C-101 revealed a segregation pattern fitting a ratio 1[ratio ]2[ratio ]1 for intermediate, high and very high C22[ratio ]1 content. The segregation patterns fitted a one-locus (designated M2) model with two alleles (M2 and mi) and with partial dominance of high over intermediate C22[ratio ]1 content. The segregating generations of the crosses L-935×L-2890 showed a strong transgressive segregation with C22[ratio ]1 values ranged from 1·3–406·5 g/kg. The analyses of the F2, BC1F1 and F3 generations indicated that the combination of alleles at two loci, M1 and M2 controlled the transgressive segregation for C22[ratio ]1 content. The proposed genotypes (C22[ratio ]1 content) for each parent were as follows: L-935 (190 g/kg 22[ratio ]1)=MMmimiEEEE; L-2890 (112 g/kg C22[ratio ]1)=mmmmEEEE; and C-101 (441 g/kg C22[ratio ]1)=MMMMEEEE.

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The thirty-seventh meeting of the group, chaired by J. Craigon of The University of Nottingham, was held in the Kohn Centre at the Royal Society, 6 Carlton House Terrace, London on Friday, 8 April 2005 when the following papers were read.

Diets for broiler chickens (n=90) were supplemented with chromium (CrCl3, 6H2O), either alone (0·2 mg/kg diet) or in a combination with ascorbic acid (0·2 mg Cr and 50 mg ascorbic acid/kg diet). The objectives of the study were to ascertain if ascorbic acid had any additive effect on the actions of chromium and whether chromium supplementation could alleviate the nutritional stress in the birds imposed by a reduced energy intake. The birds were fed at the recommended (Bureau of Indian Standards 1992) and at a lower plane of energy. Live-weight gain and diet utilization were higher (P<0·01) when the normal energy diet supplemented with chromium was fed. Food intake (35 days) was higher (P<0·001) in the birds fed with the low energy diet. There was an increase (P<0·01) in metabolizability due to the supplementation of chromium. The metabolizability of crude protein and total carbohydrate increased (P<0·05) when chromium and ascorbic acid were supplemented together. Chromium intake was higher (P<0·001) in the supplemented birds, especially in those fed with the low energy diet (P<0·05), though its retention was higher (P<0·05) when the normal energy diet was given. Chromium in combination with ascorbic acid also enhanced (P<0·01) chromium retention. Blood glucose (P<0·001) and plasma cholesterol (P<0·05) were lower in the supplemented birds and blood glucose was reduced further when ascorbic acid was supplemented together with chromium (P<0·01). Plasma protein increased (P<0·05) in the supplemented chickens. However, variation in the dietary energy concentration did not exert any significant effect on these blood parameters. Plasma chromium was higher (P<0·05) in the supplemented birds, though chromium had little effect in this regard with ascorbic acid. Plasma copper increased (P<0·05) when chromium was supplemented alone and increased further (P<0·05) when chromium and ascorbic acid were supplemented together. Deposition of chromium in the breast and thighs increased (P<0·05) due to supplementation. Protein content and total accretion of protein in the carcass were higher (P<0·05) when chromium was supplemented alone and with ascorbic acid. The supplemented birds had less (P<0·01) fat per 100 g of carcass irrespective of the dietary energy concentration. Weight of the hot carcass increased (P<0·05) due to chromium supplementation although dietary energy concentration did not affect this particular parameter. It was concluded that inorganic chromium supplementation (0·2 mg chromium/kg diet) might effectively enhance the growth performance, diet utilization and carcass characteristics in broiler chickens. Addition of ascorbic acid might also be beneficial in this regard. However, dietary energy concentration was more critical and to yield the maximum benefit of Cr supplementation in broiler chickens, an optimum level was essential.

The active germplasm Bank of the Integrated Unit (Facultad de Ciencias Agrarias, Unversidad Nacional de Mar del Plata and the Experimental Station of INTA) at Balcarce, keeps both in vivo (live herd) and in vitro Criollo Cattle (samples of semen and embryos cryogenically), with the aim of preserving genetic variability for potential future use. Parameters based on probable origin of genes, on population size and on the estimation of components of (co)variances for birth and weaning weights were estimated to evaluate the genetic variability of the material contained in the Bank. The information available came from 667 individuals, of which 84 had unknown parents, and 142 half-founders (only one parent known), having a mean number of births per year of 24 calves from four different sires. AI was performed during the mating season almost every year. The evolution of effective number of founders (fe), effective number of ancestors (fa), effective number of founder genomes (Ng) and the ratio fe/fa over different periods from the creation of the Bank, were analysed. Annual increase of inbreeding coefficient (F) was 0·2% and the effective population size (Ne) was estimated as 23, 14 and 25 individuals for the periods defined by years 1978–82, 1983–87 and 1993–97, respectively. The ratio fe/fa was higher in the years where the ratio number of sires/number of dams was lower, indicating that the impact of the effective number of sires is more important than the effective number of females in generating genetic bottlenecks. When the reference population was taken for the period 1989–97, 16·45 out of the 85·63 founders of the population made contributions not explained by other ancestors, but if possible losses of genomes due to genetic drift are considered, the number of genomes still present was reduced to 9·09 indicating a possible narrow genetic bottleneck in the last period. The Ng/fe ratio was 0·11, 0·10 and 0·11 for the reference populations defined by years 1989–92, 1993–97 and 1989–97, respectively. The main objective in germplasm conservation programmes should be the maintenance of genetic variability. Thus, matings in the population under conservation should be designed in order to mate those animals that maximize the effective number of genome founders (Ng) to avoid losses due to genetic drift.

A model of sugarcane digestion was applied to indicate the suitability of various locally available supplements for enhancing milk production of Indian crossbred dairy cattle. Milk production was calculated according to simulated energy, lipogenic, glucogenic and aminogenic substrate availability. The model identified the most limiting substrate for milk production from different sugarcane-based diets. For sugarcane tops/urea fed alone, milk production was most limited by amino acid followed by long chain fatty acid availability. Among the protein-rich oil cake supplements at 100, 200 and 300 g supplement/kg total DM, cottonseed oil cake proved superior with a milk yield of 5·5, 7·3 and 8·3 kg/day, respectively. This was followed by mustard oil cake with 5·1, 6·5 and 7·6 kg/day, respectively. In the case of a protein-rich supplement (fish meal), milk yield was limited to 6·6 kg/day due to a shortage of long chain fatty acids. However, at 300 g of supplementation, energy became limiting, with a milk yield of 6·7 kg/day. Supplementation with rice bran and rice polishings at 100, 200 and 300 g restricted milk yield to 4·3, 4·9 and 5·5 and 4·5, 5·3 and 6·1 kg/day, respectively, and amino acids became the factor limiting milk production. The diet comprising basal sugarcane tops supplemented by leguminous fodder, dry fodder (e.g. rice or wheat straw) and concentrates at levels of 100, 200 and 300 g supplements/kg total diet DM proved to be the most balanced with a milk yield of 5·1, 6·7 and 9·0 kg/day, respectively.

Few methods exist for estimating quantitatively the diet composition of free-ranging herbivores. The current study examined whether long-chain fatty alcohols (alcohols) or long-chain fatty acids (acids) could be used along with n-alkanes to allow reliable diet composition estimates to be made in herbivores consuming complex diets. Twelve Scottish Blackface wether sheep housed in metabolism crates were fed four different mixtures of three plant species (three animals per mixture) for a seven-period experiment. Concentrations of cuticular wax n-alkanes, alcohols and acids were estimated in samples of individual plant species, and the faeces from animals that consumed mixtures of these species. These concentrations were then used to calculate the dietary proportions of each species by a least-squares optimization procedure. To explore the differences between the estimation methods (individual markers and their combinations), the mean squares of errors (EMS) between the actual and predicted proportions of plant species were calculated.

In three out of the four mixtures, alcohols had the lowest discrepancies (lowest EMS values), followed by n-alkanes and then acids. Acids yielded the lowest discrepancy in one mixture and the highest in the others.

It is concluded that, for this particular set of mixtures, alcohols had great potential to estimate composition of complex diets. However, the estimation using acids was less good and n-alkanes were of intermediate potential. Estimation from the combination of the three marker classes was always better than using the poorest individual marker.

An experiment was conducted at the University of KwaZulu–Natal to assess the effect of constant photoperiods on sexual maturity and egg-laying performance in broiler breeders given two levels of control-feeding during the rearing phase. Cobb broiler breeder females were grown to reach 2·1 kg body weight at 17 or 21 weeks, and maintained on 10, 11, 12, 13, 14 or 16-h photoperiods from 2 days to 68 weeks of age. There were no significant interactions between photoperiod and growth rate for any production parameter. The time required reaching 2·1 kg increased proportionally with photoperiod but, because of delayed sexual development, birds on longer photoperiods consumed more feed to, and were heavier at, sexual maturity than shorter daylengths. The longer-photoperiod birds also had inferior rates of lay in the first half of the cycle, but superior in the second, which, together with the photoperiodic effects on maturity, resulted in birds on 11, 13 or 14 h producing most eggs to 68 weeks, and those on 16 h fewest. It is possible that the pattern of egg production was due to some of the birds on [ges ]13-h photoperiods becoming photorefractory, having a mid-cycle pause, and then spontaneously resuming egg production in the latter half of the cycle. However, a hinge-analysis of current and other data to the more usual depletion age of 60 weeks showed that the combined effects of photoperiod on sexual maturity and egg production resulted in constant 10-h birds producing the highest number of eggs, with numbers decreasing by 3·6 eggs/h of photoperiod above the hinge and 7·8 eggs/h of photoperiod below it. Mean egg weight increased by 0·4 g/h of photoperiod, but the proportion of abnormally large and floor eggs and the incidence of mortality were unaffected by daylength. For each photoperiod, accelerated growth resulted in body weights being heavier than controls at sexual maturity, despite the mean age at maturity being 10 days earlier for the faster-growing birds. Body weights for the two growth groups were not significantly different at 68 weeks. Faster-growth birds consumed 1 kg less feed to 2·1 kg body weight, but 1·3 kg more feed to sexual maturity and 2·7 kg more to 68 weeks, and produced 6 more eggs than, but had similar patterns of egg production to, the conventionally managed controls. Mean egg weight, the proportion of floor eggs and the incidence of mortality were similar for both groups. Notwithstanding that the overall production of abnormally large eggs was low (1·1 eggs per bird); the faster-growing birds produced significantly more than the controls. Egg weight was positively influenced by age at sexual maturity, body weight at sexual maturity and photoperiod, but was unaffected by rate of growth to 2·1 kg per se.

These findings show that there are differences between broiler breeders and egg-type pullets in their response to constant photoperiods. It is likely that the factors responsible for these differences, particularly in terms of sexual development, are the exhibition of photorefractoriness by, and the retardational effects of controlled feeding on, broiler breeders.