The present study was carried out on 1243 kids (379 Black Bengal; 568 Jamunapari × Black Bengal and 296 Beetal × Black Bengal) born between 1981 and 1986. Data were analysed to study the influence of genetic group, sex, season of birth, type of birth, birth weight, dam's weight at kidding, filial generation and parity of dam (as covariate) on survivability of kids during the pre-weaning period (0 to 90 days of age). The overall survival rates during 0 to 15, 16 to 30, 31 to 60, 61 to 90 and 0 to 90 days of age were 81·68 (s.e. 2·89), 95·55 (s.e. 2·00), 90·77 (s.e. 2·33), 93·31 (s.e. 2·59) and 69·94 (s.e. 3·65) % respectively. Variation in survival rates from 0 to 15 days of age was significant due to genetic group (P < 0·01), birth weight (P < 0·01), dam's weight at kidding and parity of dams as a covariate (P < 0·05). Season of birth (P < 0·05), weight of kids (P < 0·01) and dam's weight at kidding (P < 0·01) had significant effects on survival rate during 0 to 90 days of age. Sex and type of birth had no significant effect on survival rates. The interaction effects of genetic groups with season of birth and sex on pre-weaning survival rates were not significant in all ages except the effect between genetic group and sex during 31 to 60 days of age. An improvement in survival rates during the period of study was noticed with the increase in filial generation number from Fj to F3, although the difference was not significant except from 61 to 90 days of age (P < 0·05). Birth weight of kids had a positive linear relationship with survivability during the pre-weaning period. Summer-born kids had a significantly lower survival rate than those born in the winter and monsoon periods from 16 to 30, 61 to 90 and from 0 to 90 days of age. A negative linear relationship was observed between dam's weight at kidding and survival rates of kids from 0 to 90 days of age except the 25 to 30 kg dams deviate. Heritability estimates of survival rates during pre-weaning periods were not significantly different from zero, indicating that improvement by simple selection is probably limited.

Plasma very low density lipoproteins (VLDL) of gilts were separated into two sub fractions according to their affinity for heparin. The proportion of VLDL present as subfraction 2 (higher affinity for heparin) varied, according to the genetic line of the pigs, between 0·21 and 0·78 in virgin gilts. The proportions were related to the variation in piglet survival in the same nine genetic lines by a quadratic equation, which predicted that greater than 90% survival to weaning was to be found in piglets born to gilts having between about 0·3 and 0·7 of their VLDL as subfraction 2. This observation suggests a simple measurement that could be used in the selection of sows for a breeding programme. The proportion of subfraction 2 fell throughout pregnancy in each of three genetic lines measured and only returned to pre-pregnant values after weaning: these changes did not correlate with the changes in the lipid composition of plasma VLDL measured during pregnancy and lactation. The findings suggest a role for the VLDL subfractions in controlling the nutrition of the neonatal pig.

It can be hypothesized that the body composition characteristics of different sheep breeds affect their nutritional requirements. However, no study has yet been carried out to determine the nutritional requirements for maintenance of Texel purebred lambs, despite their growing importance in sheep meat production globally. Our objective was therefore to determine the energy and protein requirements for maintenance of Texel lambs. Thirty-four Texel lambs were used, all intact males that were weaned at 50 days old, and confined in individual pens. Two experiments were conducted, as follows. In Experiment 1, a digestibility assay was performed to determine the dietary energy value, in a 3×3 double Latin square design, in which lambs were submitted to three levels of feed restriction (0%, 55% and 70% of ad libitum feed intake). In Experiment 2, the energy and protein requirements for maintenance of Texel lambs from 21 to 40 kg BW were determined using a randomized block design, in which lambs were also submitted to three levels of feed restriction (0%, 55% and 70% of ad libitum feed intake). The requirements for net energy for maintenance (NEm), metabolizable energy for maintenance (MEm), net protein for maintenance (NPm) and metabolizable protein for maintenance (MPm) were determined. The digestibility of dry matter, energy, protein and metabolizability were similar between food restriction levels, averaging 74.4%, 75.5%, 80.3% and 0.636, respectively. The NEm determined for growing Texel lambs was 263 kJ/kg of the metabolic fasting BW (FBW), the MEm was 417 kJ/kg0.75 FBW and the efficiency of use of MEm was 0.63. In addition, the NPm was 1.24 g/day per kg0.75 FBW and the MPm was 2.98 g/day per kg0.75 FBW. The energy requirements of Texel lambs are different from those reported in the literature, possibly due to differences between breeds, diets and environmental effects, whereas the protein requirements are different from literature mainly due to methodological differences; further studies are need to address these aspects that affects the nutritional requirements for raising sheep from different breeds in different environments.

The incidence of twin calvings and double ovulations was studied in two Milking Shorthorn herds and one Friesian herd, each with above-average annual twin calving rates (average 0·031, compared with a national rate of 0·01). The proportions of double ovulations were calculated from records comprising 1237 cow × years (cows over 2·0 years of age); means were 0·08, 0·27 and 0·50, for three groups which had previously produced 0, 1 or >1 sets of twins, respectively. All cows (whether still present or no longer in the herd) were then allocated a twin production status, to indicate the number of twin sets (0, 1 or >1) produced, or produced so far, in their lifetime. There were records from 1559 cows, with sire and dam also known. Twin production status was significantly influenced by dam group (P < 0·01), i.e. the twin production status of the cow's dam. Sires were classified into two groups, according to whether any daughters had produced two or more sets of twins. After allowing for ascertainment, sires in the two groups were found to differ (P < 0·01) by 0·06 in the probability of their daughters producing at least one set of twins in their lifetime (i.e. 0·08 to 0·14). One sire and dam combination in particular had prolific daughters with a probability of 0·39 of producing at least one set of twins in their lifetime (compared with a probability of 0-07 for the other extreme combination). The possibility of these observations being explained by the segregation of a single recessive gene was considered, but the necessary interaction between sire group and dam group was not significant.

TM-QTL is a quantitative trait locus (QTL) on ovine chromosome 18 (OAR18) known to affect loin muscling in Texel sheep. Previous work suggested that its mode of inheritance is consistent with paternal polar overdominance, but this has yet to be formally demonstrated. This study used purebred Texel sheep segregating for TM-QTL to confirm its presence in the chromosomal region in which it was first reported and to determine its pattern of inheritance. To do so, this study used the first available data from a Texel flock, which included homozygote TM-QTL carriers (TM/TM; n=34) in addition to homozygote non-carriers (+/+; n=40 and, heterozygote TM-QTL-carriers inheriting TM-QTL from their sire (TM/+; n=53) or their dam (+/TM; n=17). Phenotypes included a wide range of loin muscling, carcass composition and tissue distribution traits. The presence of a QTL affecting ultrasound muscle depth on OAR18 was confirmed with a paternal QTL effect ranging from +0.54 to +2.82 mm UMD (s.e. 0.37 to 0.57 mm) across the sires segregating for TM-QTL. Loin muscle width, depth and area, loin muscle volume and dissected M. longissimus lumborum weight were significantly greater for TM/+ than +/+ lambs (+2.9% to +7.9%; P<0.05). There was significant evidence that the effect of TM-QTL on the various loin muscling traits measured was paternally polar overdominant (P<0.05). In contrast, there was an additive effect of TM-QTL on both live weight at 20 weeks and carcass weight; TM/TM animals were significantly (P<0.05) heavier than +/+ (+11.1% and +7.3%, respectively) and +/TM animals (+11.9% and +11.7%, respectively), with TM/+ intermediate. Weights of the leg, saddle and shoulder region (corrected for carcass weight) were similar in the genotypic groups. There was a tendency for lambs inheriting TM-QTL from their sire to be less fat with slightly more muscle than non-carriers. For example, carcass muscle weight measured by live animal CT-scanning was 2.8% higher in TM/TM than +/+ lambs (P<0.05), carcass muscle weight measured by carcass CT-scanning was 1.36% higher in TM/+ than +/+ lambs (P<0.05), and weight of fat trimmed from the carcass cuts was significantly lower for TM/+ than +/+ lambs (−11.2%; P<0.05). No negative effects of TM-QTL on carcass traits were found. Optimal commercial use of TM-QTL within the sheep industry would require some consideration, due to the apparently different mode of action of the two main effects of TM-QTL (on growth and muscling).

The aim of this study was to highlight the relationships between decorin, tenascin-X and type XIV collagen, three minor molecules of extracellular matrix (ECM), with some structural parameters of connective tissue and its content in total collagen, its cross-links (CLs) and its proteoglycans (PGs). In addition, we have evaluated impact of these minor molecules on beef quality traits. The relative abundance of these molecules was evaluated by western blot analysis in Longissimus thoracis (LT) and Biceps femoris (BF) muscles from Aberdeen Angus and Blond d’Aquitaine beef breeds. Decorin and tenascin-X were more abundant in BF than in LT (1.8 v. 0.5 arbitrary units (AU), respectively, P<0.001, and 1.0 v. 0.6 AU, P<0.05). There was no muscle effect for collagen XIV content. Decorin and tenascin-X relative abundance were positively correlated with perimysium and endomysium areas and with collagen characteristics (total, insoluble and CLs). Decorin was negatively correlated with total PG content and positively with tenascin-X. Collagen XIV was correlated with any of parameters measured. To assess the impact of decorin, tenascin-X and collagen XIV and of their ratios to total collagen and PGs on shear force and quality traits we realized, respectively, a multiple-linear regression analysis and a Pearson’s correlation analysis. Decorin and tenascin-X relative abundance were, respectively, negatively and positively involved in juiciness. Decorin relative abundance was also negatively involved in abnormal flavour and positively in overall liking. The ratio of decorin to total collagen and PGs was negatively correlated to juiciness, together with collagen XIV ratio to total PGs. The ratios of decorin, tenascin-X and collagen XIV to total PGs were positively correlated to sensory tenderness, negatively to abnormal beef flavour and positively to overall liking. The ratio of decorin to total collagen was also negatively correlated to abnormal flavour and positively to overall liking while its ratio to total PGs was positively correlated to beef flavour and overall liking. Results of the present study highlighted for the first time the possible role of minor ECM molecules on beef quality traits. In addition, variations of meat texture and more generally of sensory qualities would depend not only to the quantity of total collagen and of its CLs, but also of components of ECM such as decorin, tenascin-X and collagen XIV and of their ratios to total collagen and PGs.

The effects on milk yield and feeding behaviour of offering ryegrass silage (r), ryegrass and white clover silage (c), or grass hay (h) supplements were examined for cows grazing a ryegrass pasture (R) or a ryegrass and white clover pasture (C). The chemical composition of the two silages was similar but the hay contained less crude protein. Cows grazing R pasture spent longer feeding on c than r silages, and those consuming the c silage spent less time grazing than those consuming r silage. The cows grazing the C pasture spent longer feeding on r than c silages, and those consuming the r silage spent less time grazing than those consuming c silage. The cows’ intake of hay dry matter (DM) was less than silage DM and it was taken into the mouth at a slower rate, masticated more ana swallowed less frequently than silage. Milk yield and composition were not affected by the type of supplementary forage or pasture type. Thus cows grazing pastures of the two sward types spent longer feeding on forages with dissimilar botanical composition if given the option. However, as this reduced the time that they spend grazing, there was no effect on milk production.

Consistent age differences at around 27 kg live weight have been found between control (C) and selection (S) line boars of the Large White breed in a coordinated breed improvement programme (89·8 v. 94·6 days, P<001). After 10 generations of index selection on feeding ad libitum, a sample of 20 boars from the programme, 10 C and 10 S, were slaughtered at 27·6 (s.e. 0·48) kg live weight for a more comprehensive examination of this finding. Physical dissection of the carcass and whole body chemical analysis were carried out. Differences between C and S boars were apparent even at this light weight: S boars were older than C (92·7 v. 83·5 days, P<0·01), contained less dissected fat (2·93 v. 3·58kg, P<005) and chemical lipid (315 v. 3·59kg, P<0·05), and had a higher lean proportion (0·477 v. 0·458, P<0·01). There was no significant difference between lines in weight of dissected lean or whole body protein. Index selection has clearly affected early growth and body composition, which questions current assumptions underlying pig testing methods.

Better understanding of how animals regulate their intake may be gained by analysis of feeding behaviour. This is often recorded in terms of feeding events, e.g. visits to feeders, which can be clustered into meals. This enables calculation of the probability of animals starting a meal in relation to time since the last meal, which is thought to give insight into food intake regulation. Starting probabilities are often calculated with pooled data but recent work suggests that pooling may strongly affect conclusions.

In this study we analysed feeding behaviour of cows to investigate how previous conclusions about feeding behaviour may have been affected by pooling. Using parameters derived from experimental data, we constructed simulation models to further explore under what circumstances pooling, either across day and night or across individuals, could affect the interpretation of starting probabilities. Data were simulated to explore the consequences of pooling as either the proportion of meals occurring during the day or the individual variation in their mean number of meals per 24 h changed. Simulation allowed us to extend the analysis of the consequences of pooling for the interpretation of starting probabilities.

Analysis of experimental data, collected with 16 dairy cows, showed that they ate a mean of six meals per 24 h. Individual variation resulted in a proportional CV of the individual mean number of meals per 24 h of 0·14. Cows ate a mean proportion of 0·59 of their meals during the day. Analysis of experimental data suggested that pooling, conducted in previous studies, has probably led to a quantitative underestimation of the increase in starting probability with time since the last meal but not a qualitative misinterpretation of the direction of change in the starting probability.

Simulation studies showed that pooling had no serious consequences when the mean number of meals per 24 h, or the variation about this mean, was low. However, as the number of meals per 24 h and variation increased, pooling led to conclusions that may wholly misrepresent both magnitude and direction of the change in starting probabilities calculated separately for the individuals or for day and night. This may explain why the results of some published studies seem not to agree with biological principles of food intake regulation.

Spineless cactus is a useful feed for various animal species in arid and semiarid regions due to its adaptability to dry and harsh soil, high efficiency of water use and carbohydrates storage. This meta-analysis was carried out to assess the effect of spineless cactus on animal performance, and develop and evaluate equations to predict dry matter intake (DMI) and average daily gain (ADG) in meat lambs. Equations for predicting DMI and ADG as a function of animal and diet characteristics were developed using data from eight experiments. The dataset was comprised of 40 treatment means from 289 meat lambs, in which cactus was included from 0 to 75% of the diet dry matter (DM). Accuracy and precision were evaluated by cross-validation using the mean square error of prediction (MSEP), which was decomposed into mean bias, systematic bias and random error; concordance correlation coefficient, which was decomposed into accuracy (Cb) and precision (ρ); and coefficient of determination (R2). In addition, the data set was used to evaluate the predicting accuracy and precision of the main lamb feeding systems (Agricultural and Food Research Council, Small Ruminant Nutritional System, National Research Council and Institut National de la Recherche Agronomique) and also two Brazilian studies. The DMI, CP intake (CPI), metabolizable energy (ME) intake and ADG increased when cactus was included up to 499 g/kg DM (P<0.001). In contrast, animals fed high levels of cactus (>500 g/kg DM) had a decreased DMI, CPI and NDF intake, but increased feed efficiency (P<0.001) and similar ADG compared with those without cactus addition. The DMI was positively correlated with initial BW, final BW, concentrate and ADG, while it was negatively correlated with cactus inclusion and ME of the diet. On other hand, ADG was positively correlated with DMI, initial and mean BW and concentrate, and it was negatively correlated with cactus inclusion. The two developed equations had high accuracy (Cb of 0.95 for DMI and 0.94 for ADG) and the random error of MSEP was 99% for both equations. The precision of both equations was moderate, with R2 values of 0.53 and 0.50 and ρ values of 0.73 and 0.71 for DMI and ADG, respectively. In conclusion, the developed equation to predict DMI had moderate precision and high accuracy, nonetheless, it was more efficient than those reported in the literature. The proposed equations can be a useful alternative to estimate intake and performance of lambs fed cactus.

The pattern of follicle activity and fibre growth on the neck, mid side and rear leg of 12 Scottish Cashmere (SC) and nine Siberian (S) goat kids was examined from birth to 255 days of age. In both genotypes maximum secondary to primary follicle (S/P) ratio was reached earliest on the neck (P < 0·05) but was proportionately 0·21 and 0·28 (P < 0·001) lower than that on the rear leg and mid side respectively. Secondary follicle activity ceased earlier on the rear leg than the mid side or neck (P < 0·001) and this was associated with lower staple lengths and patch weights of undercoat. Fibre weight and diameter were compared on six body parts: neck, front leg, mid side, rear leg, rump and belly at 255 days of age. Patch undercoat weights and diameter were greatest on the neck, front leg and rump and lowest on the belly.

The estimated annual production of undercoat, calculated from patch weights and skin area measurements on the six parts of the body at 255 days of age was 138 (range 42 to 260) g for SC kids and 525 (range 377 to 661) g for S kids (s.e.d. = 39·4, P < 0·001). Mean undercoat diameter was 16·15 (range 15·32 to 17·51) and 18·94 (range 17·25 to 19·89) μm for SC and S kids respectively (s.e.d. = 0·376, P < 0·001).

Correlation coefficients between fibre traits, measured at approximately monthly intervals and estimates of annual production and undercoat diameter at 255 days were calculated. For SC kids mid-side patch undercoat weight was consistently and strongly related to estimated annual production (mean correlation coefficient, 0·85, s.e. 0·036). For S kids the only variable to show a consistently strong relationship with estimated annual production was mid-side undercoat staple length × diameter2 (mean correlation coefficient 0·66, s.e. 0·067). Thus the best fibre traits for ranking annual production differed between genotypes. In both cases the accuracy of the ranking increased with age. Undercoat fibre diameter measured from 4 to 5 months of age was closely related to estimated undercoat diameter at 255 days of age in both SC and S genotypes (mean correlation coefficient 0·92, s.e. 0·009). Prior to 4 months of age the mean correlation coefficient for SC and S genotypes was 0·53 (s.e. 0·20).

It is concluded that goat kids can be ranked for annual production and diameter of the undercoat, prior to first harvesting, based on fibre traits measured on samples of the fleece.

The efficiency of oestrus detection is probably the most important factor determining the profitability of the dairy farming enterprise. With current trends towards larqer herds and fewer stockmen, achieving a 365 day calving interval has become increasingly difficult, with each oestrus missed representing considerable economic loss (Esslemont and Bryant, 1976). This highlights the need for an accurate method of oestrus detection

An experiment was undertaken to evaluate the use of milk temperature as a method of oestrus detection.

The errors of the slaughter and tritiated water techniques of estimating energy retention were compared in a group of grazing sheep deprived of feed and water for 48 hr. It was calculated that the mean energy retention of the experimental animals would have had a standard error of 3·64 Mcal if estimated by the slaughter technique, and 1·56 Mcal if estimated by the tritiated water technique. It was concluded that in other experimental groups the precision of the relationship between energy content and live weight is likely to be the most important determinant of the relative precision of the two methods. In neither method would worthwhile gains in precision result from knowledge of the weight of the contents of the alimentary tract.

The present study investigated the effect of hydrothermic maize processing and supplementation of amino acids (AA) in two experiments. In total, 60 barrows and 384 broilers were fed four diets including either unprocessed (T1), or hydrothermically processed maize, that is short- (T2), or long-term conditioned (LC) (T3), and subsequently expanded maize of the same batch. Assuming a higher metabolizable energy (ME) content after processing, the fourth diet (T4) contains maize processed as treatment T3, but AA were supplemented to maintain the ideal protein value. Performance, digestibility and product quality in both species were assessed. Results show that in pigs receiving T4 the average daily feed intake was lower compared with the other treatments, whereas no difference was observed in broilers. The T3 improved the feed conversion rate compared with T1 (P<0.10) for both species. In contrast, average daily gain (ADG) (1277 g/day for T2 and 1267 g/day for T3 v. 971 g/day for T1) was only altered in pigs. The hydrothermic maize processing increased the apparent total tract digestibility (ATTD) of dry matter, starch and ether extract after acid hydrolysis. This may be a consequence of higher ATTD of gross energy in the finishing phase for both animal species, suggesting a higher ME content in diets with processed maize. The higher ME content of diets with processed maize is supported also by measurements of product quality. Supplementation of AA in T4 enhanced the loin depth in pigs as well as the amount of breast meat in broilers. Further effects of processing maize on meat quality were the reduced yellowness and antioxidative capacity (P<0.10) for broilers, likely due to the heat damage of xanthophylls and tocopherols. Processing also increased springiness and chewiness (P<0.10) of the broilers breast meat, whereas the loin meat of pigs showed a decreased lightness and yellowness (P<0.10) in meat when hydrothermic processed maize was used (for T2, T3 and T4). LC processed maize (T3) showed the lowest springiness in pork, however the supplementation of AA in T4 did not show differences between the treatments. Shown results demonstrated positive effects of hydrothermic processing of maize on animal performance and digestibility in both species. However, effects on carcass characteristics and product quality differed. The negative effects on product quality could be partly compensated with the AA supplementation, whereas a change in meat colour and reduced antioxidative capacity was observed in all groups fed hydrothermic maize processing.

The objective of the study was to evaluate the effect of screen size (1, 2 and 3 mm) and microbial phytase (0 and 1000 FTU/kg as-fed) on phytate degradation in maize (100% maize), soybean meal (100% SBM) and maize–SBM (75% maize and 25% SBM) incubated in water for 0, 2, 4, 8 and 24 h at 38°C. Samples were analysed for pH, dry matter and phytate phosphorus (P). Particle size distribution (PSD) and average particle size (APS) of samples were measured by the Laser Diffraction and Bygholm method. PSD differed between the two methods, whereas APS was similar. Decreasing screen size from 3 to 1 mm reduced APS by 48% in maize, 30% in SBM and 26% in maize–SBM. No interaction between screen size and microbial phytase on phytate degradation was observed, but the interaction between microbial phytase and incubation time was significant (P<0.001). This was because microbial phytase reduced phytate P by 88% in maize, 84% in maize–SBM and 75% in SBM after 2 h of incubation (P<0.05), whereas the reduction of phytate P was limited (<50%) in the feeds, even after 24 h when no microbial phytase was added. The exponential decay model was fitted to the feeds with microbial phytase to analyse the effect of screen size and feed on microbial phytase efficacy on phytate degradation. The interaction between screen size and feed affected the relative phytate degradation rate (R d ) of microbial phytase as well as the time to decrease 50% of the phytate P (t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ ) (P<0.001). Thus, changing from 3 to 1 mm screen size increased R d by 22 and 10%/h and shortened t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ by 0.4 and 0.2 h in maize and maize–SBM, respectively (P<0.05), but not in SBM. Moreover, the screen size effect was more pronounced in maize and maize–SBM compared with SBM as a higher phytate degradation rate constant (K d ) and R d , and a shorter t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ was observed in maize compared with SBM in all screen sizes (P<0.05). However, a higher amount of degraded phytate was achieved in SBM than in maize because of the higher initial phytate P content in SBM. In conclusion, reducing screen size from 3 to 1 mm increased K d and R d and decreased t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ in maize and maize–SBM with microbial phytase. The positive effect of grinding on improving microbial phytase efficacy, which was expressed as K d , R d and t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ , was greater in maize than in SBM.

In 1979/80, 390 cows of black and white breeds produced more than 750 kg fat plus protein in a 305-day lactation, compared with a mean of 390 kg for all recorded black and white cows. The cows were distributed in 207 herds and were the daughters of 177 sires whose breeding values (with population means in brackets) were +220 kg milk ( + 100), +8 kg fat (+5) and +6 kg protein (+2). The farms on which they were kept were not markedly different from average holdings in England and Wales. Management was characterized by high labour input, with high intakes of diets containing a high energy and protein concentration, and care was taken to ensure that food was on offer at all times. Grassland management tended towards conservation by silage rather than hay. Calving intervals were slightly longer than average (393 days v. 386 days for all recorded cows of a similar age).

The most obvious characteristic of management was the close attention given to ways of persuading the animals to eat enough food to satisfy their nutritional requirements.

Two experiments were conducted to determine the effects of feeding equal quantities of milk during the pre-weaning period through different milk-feeding regimes on calf growth, starter intake and selected blood metabolites. In experiment 1, 44 female Holstein calves (3 days of age and 39.2±4.3 kg of BW) were distributed randomly to one of two milk-feeding programs (1 calf per pen; 22 pens per treatment group): (1) consistent (CONS; 6 l/day of milk from days 3 to 60 and 3 l/day from days 61 to 65 of age) or (2) step-up/step-down (SUSD; 5 l/day of milk from days 3 to 15, 8 l/day from days 16 to 40, 6 l/day from days 41 to 50, 3 l/day from days 51 to 60 and then 2 l/day from days 61 to 65 of age). No difference between treatments was observed in starter consumption, feed efficiency, hip width and heart girth. However, pre-weaning average daily gain (ADG) tended to be greater in CONS than in SUSD calves (0.78 v. 0.70 kg/day; P=0.07). Blood β-hydroxybutyrate at day 45 (pre-weaning) was lower in SUSD than in CONS calves (0.14 v. 0.21±0.013 mmol/l). In experiment 2, 26 male Holstein calves (3 days of age and 39.4±4.1 kg of BW) were assigned at random to one of two milk-feeding protocols (1 calf per pen; 13 pens per treatment group): (1) consistent (CONS; (7 l/day of milk from days 3 to 40 and 2 l/day from days 41 to 45 of age) or (2) step-down (STD; 8 l/day of milk from days 3 to 30, 4 l/day from days 31 to 40 and 2 l/day from days 41 to 45 of age). The milk-feeding program had no effect on the performance measurements, with the exception that ADG (days 15 to 30), starter intake (days 30 to 45) and heart girth (day 45) were greater in STD than in CONS calves. In conclusion, it appears that if the total amount of milk intake is held constant over the course of milk-feeding period, the method of milk feeding would have negligible effects on calf performance.

Over a 40-day period nine rabbits were each given one of nine isocaloric diets with progressively reduced amounts of crude protein (159 to 97 g/kg) but a fixed level of lysine; the latter was slightly below the higher of the National Research Council (NRC, 1977) and Societe de Chime Organique et Biologique (AEC, 1978) recommendations. The proportion of each other essential amino acid in the diet of highest crude protein concentration was close to a balance derived from the higher of each independently determined amino acid requirement given by NRC (1977) and AEC (1978), while the proportions in the two diets of lowest crude protein level were below those in a theoretical amino acid balance based on rabbit whole-body tissue composition. When an intersecting linear regression line model was fitted to growth performance data over the period, performance was found to be similar on the first six diets (159 to 123 g crude protein per kg) but further reductions in dietary protein were accompanied by a decline in growth rate and concomitant increase in food conversion ratio. Fitting of an asymptotic model to the data showed that growth performance first declined markedly between diets four and five (130 to 120 g crude protein per kg). These findings suggest that if a balance of essential amino acids relative to lysine, based on current amino acid recommendations, is adhered to in diet formulation for the growing rabbit, several of these amino acids will be in excess of requirement

Grass silage with a dry-matter content of 20·7%, and containing 18·9% crude protein and 67·0% digestible organic matter in the dry matter was self-fed to 20 lactating dairy cows for 18 weeks. In addition, 9 kg of brewers' grains with a dry-matter content of 28·8% was offered to each cow daily. The two supplement treatments were a barley mix and a groundnut cube containing 11·9 and 33·5% crude protein in the dry matter respectively. The barley was given at the rate of 4 kg/10 kg milk, and the groundnut at 1·5 kg/10 kg milk. The mean daily yields of milk were 18·9 and 19·4 kg/cow on the barley and groundnut treatments respectively and did not differ significantly.

Two groups of 12 Belgian Blue double-muscled cull females were used successively in a 2-year repeated experiment and divided into three groups according to age, allowing four animals per group each year. The aim of the trial was to relate, during the finishing period, the metabolic and endocrine parameters with age. Females were fattened with a diet based on maize silage and were blood sampled on several occasions. The average daily gain (ADG) decreased with the age of the cows. Plasma glucose and triglycerides decreased also with age while the youngest females showed lower concentrations of urea than those older. The composition of plasma non-esterified fatty acids also differed considerably between groups. The hormones that best related with ADG were IGF-1 and insulin. Plasma concentrations of thyroid hormones were lower in the oldest animals. No difference between groups was found for GH. Heifers presented lower concentrations of GH and IGF-1 than those reported elsewhere in fattening bulls of the same breed. It may be concluded that in Belgian Blue double-muscled females, glucose, IGF-1 and insulin are good indicators of the growth potential. Young adult cows presented intermediate characteristics of metabolic and endocrine status that were close either to younger or to older cows.