Seventy-eight lambs, 9 weeks of age, the offspring of sires of the Scottish Blackface, East Friesland, Finnish Landrace, Suffolk and Texel breeds mated to Scottish Blackface females, as a common maternal breed, were given a barley-fish meal diet containing 1-6 g magnesium and 5·9 g phosphorus per kg dry matter for 13 weeks. Urinary excretion of Mg and P was estimated from the ratio of Mg or P to creatinine in spot samples of urine. A relationship between creatinine excretion and live weight was obtained using total urine excretion from a sample of 20 lambs, two of each sex from each sire breed group. Good agreement was found between the actual and predicted urinary excretion of minerals by the 20 lambs on three occasions.

The effect of sire breed on urinary excretion of P was significant (P < 0·05) and the breed types ranked, in descending order of excretion rate, Texel, Blackface, East Friesland, Finnish Landrace and Suffolk, with a four-fold difference in excretion rate between Texel and Suffolk. This difference in urinary excretion of P was taken as evidence of breed differences in efficiency of absorption of dietary P.

Urinary excretion of Mg was correlated with the intake of Mg. The mean estimated efficiency of absorption of dietary Mg varied, over the three occasions, from 0·42 to 0·50 and from 0·39 to 0·45 for total collections and for spot samples of urine respectively. Individual variation in the estimated efficiency of absorption within sires was not significant whereas that between sires was significant (P < 0·05). Heritability was estimated to be 0·62 (s.e. 0·30).

The addition of a categorical variable to the lactation model of Wood (1967) has been shown to be useful in the explanation of seasonality of milk production using data from an experimental herd. The technique is further investigated using monthly milk-yield data from 43 commercial herds in Northern Ireland in the years 1978 to 1982. Coefficients, d, of the categorical variable were estimated for each month of calving. The maximum value of d was 0·256 for the month of October and the minimum value was 0·022 for the month of March.

Two changeover treatments were studied over a 5-week period in eight early-weaned concentrate-fed Holstein calves of initial weight 160 kg. Fresh forage was given ad libitum for one week (A) or two weeks (B); calves on the latter treatment also had 500 g daily of maize meal. All calves received 300 g/100 kg live weight of a protein supplement and had free access to sodium and phosphorus-rich minerals. A rumen inoculation was given after seven days of forage feeding, at which point a liquid molasses/urea mixture was introduced, first in small amounts and then after a further seven days ad libitum. The forage was then restricted to 3 kg/100 kg live weight. Both treatments were effective in raising rumen pH and buffering capacity to the point of allowing the establishment and maintenance of protozoa, chiefly Entodinium and Isotricha spp. Protein N as a percentage of the total N of rumen contents was about 90 with the all-concentrate diet, fell to 35 with the roughage diets and then rose again to 80–90 by the end of the experiment.

A comparison of the patterns of LH and FSH secretion was undertaken in lines of Finn sheep selected for and against high ovulation rate. Mean ovulation rate was significantly higher in the high line ewes (mean 4·1) compared with both the control (mean 2·5) and low line (mean 2·7) ewes (P <0·01). The pre-ovulatory LH peak occurred significantly earlier in the high line ewes (mean 52·1 h) compared with both the control (mean 65·0 h) and low line (mean 59·0 h) ewes (P < 0·05). While mean LH pulse frequency and overall mean LH concentrations were both significantly higher during the follicular compared with the luteal phase of the cycle (P < 0·05), there were no consistent relationships between patterns of pulsatile LH secretion and ovulation rate among the three selection lines. Plasma FSH concentrations remained significantly higher over the entire follicular phase of the oestrous cycle in the high line ewes compared with both the control and low line ewes (P < 0·05). It is suggested that the ovulation rate achieved by high line ewes may be causally related to their higher follicular phase FSH concentrations.

There is a growing body of evidence to suggest direct involvement of the cytokines interleukin-1 (IL-1), interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) in the initiation of skeletal muscle catabolism and depressions in growth performance as a result of diseases, while TNF-α and IL-6 are presumably under the control of IL-1. An experiment was conducted to investigate whether an interleukin-1 receptor antagonist (IL-1ra) could reduce growth depressions in a model of subclinical disease in growing pigs. In this study, 24 crossbred barrows and gilts were randomly assigned to three treatments: (1) healthy control (HC), saline infusion; (2) sick control (SC), infection with Mycoplasma hyopneumoniae and vaccination with porcine reproductive and respiratory syndrome modified live virus (PRRSV) vaccine and saline infusion; (3) SC plus infusion with IL-1ra (SC+IL-1ra). An additional six pigs were killed at the initiation of the trial to determine initial body composition for estimation of carcass nutrient retention rates. During the 28-day experimental period, the SC pigs had growth performance similar to that of the HC pigs and the highest levels of plasma cytokines (P<0·10). The SC+IL-1ra pigs had growth performance similar to the HC pigs, but the SC+Il-1ra pigs tended to have higher growth rates than the SC pigs (P<0·10), the highest carcass protein accretion rate (P<0·10) and similar levels of plasma cytokines compared with the HC pigs. Plasma levels of insulin-like growth factor-1 (IGF-1) on day 22 tended to be higher (P<0·10) in the HC pigs compared with the SC or SC+IL-1ra pigs and treatment×sex interaction was observed on day 29; the IGF-1 levels tended to be higher in SC+IL-1ra gilts and SC barrows (P<0·10). These results indicate that infusion with IL-1ra in a model of subclinical disease helps attenuate the catabolic effects of immune system stimulation.

The management of an arable flock is more complex than that of any other livestock enterprise : it involves a more intimate crop-livestock association than exists in any other farming system, and to some extent the great decline in arable sheepfarming that has taken place during the past fifty years is due to the fact that it is a difficult way of farming ; there are of course, other reasons why the decline in arable sheep farming has taken place and I propose to deal with these very briefly.

I feel it is first necessary to point out that agricultural scientists and research workers have contributed practically nothing that would benefit the arable flock owner. Since the days of the late Professor Wrightson no eminent agriculturist has shown any interest in the fortunes of the arable sheep farmer, with the exception of the late Sir Daniel Hall, who once wrote an account of an ill-fated flock of Hampshire Downs kept on unsuitable land in Hampshire.

Estimated breeding values (EBVs) and genomic enhanced breeding values (GEBVs) for milk production of young genotyped Holstein bulls were predicted using a conventional BLUP – Animal Model, a method fitting regression coefficients for loci (RRBLUP), a method utilizing the realized genomic relationship matrix (GBLUP), by a single-step procedure (ssGBLUP) and by a one-step blending procedure. Information sources for prediction were the nation-wide database of domestic Czech production records in the first lactation combined with deregressed proofs (DRP) from Interbull files (August 2013) and domestic test-day (TD) records for the first three lactations. Data from 2627 genotyped bulls were used, of which 2189 were already proven under domestic conditions. Analyses were run that used Interbull values for genotyped bulls only or that used Interbull values for all available sires. Resultant predictions were compared with GEBV of 96 young foreign bulls evaluated abroad and whose proofs were from Interbull method GMACE (August 2013) on the Czech scale. Correlations of predictions with GMACE values of foreign bulls ranged from 0.33 to 0.75. Combining domestic data with Interbull EBVs improved prediction of both EBV and GEBV. Predictions by Animal Model (traditional EBV) using only domestic first lactation records and GMACE values were correlated by only 0.33. Combining the nation-wide domestic database with all available DRP for genotyped and un-genotyped sires from Interbull resulted in an EBV correlation of 0.60, compared with 0.47 when only Interbull data were used. In all cases, GEBVs had higher correlations than traditional EBVs, and the highest correlations were for predictions from the ssGBLUP procedure using combined data (0.75), or with all available DRP from Interbull records only (one-step blending approach, 0.69). The ssGBLUP predictions using the first three domestic lactation records in the TD model were correlated with GMACE predictions by 0.69, 0.64 and 0.61 for milk yield, protein yield and fat yield, respectively.

Ruminant fat is often perceived as having a negative impact on human health; however, the composition of the fat is under complex biochemical control and can be improved through strategic manipulation of the animal’s diet. There were two major objectives of this study, namely (i) to develop and validate a primary bovine intramuscular adipocyte cell line and (ii) to examine the effect of eicosapentaenoic acid (EPA) on the transcriptional regulation of Δ-9 desaturasein vitro using the novel cell line. Intramuscular adipose tissue was obtained from the Musculus longissimus thoracis of a beef heifer. Mature adipocytes were isolated and cultured, and subsequently harvested and evaluated for lipid accumulation and the expression of genes regulating key functional adipocyte protein markers at passages 10, 20 and 30. Isolated cells were shown to accumulate lipid in culture over time. Fatty acid analysis by gas chromatography was carried out at passage 30. Thirteen fatty acids ranging from tetradecanoic acid (C14:0) to the polyunsaturated fatty acid, docosahexaenoic acid (C22:6), were easily detected and measured. High-quality total RNA was isolated from adipocytes and the expression of peroxisome proliferator-activated receptor-γ, fatty acid synthase, fatty acid-binding protein-4, adipocyte lipid-binding protein, CD36, Δ-9 desaturase, sterol regulatory element-binding protein (SREBP), microsomal triglyceride transfer protein and leptin genes were identified by reverse transcriptase-PCR and sequence analysis. Expression of the negative control, liver-specific hepatocyte nuclear factor-1alpha, was not detected. Adipocytes were subsequently incubated in medium containing 0, 50 or 100 μM EPA for 24 h. Increasing the EPA concentration of the culture media led to a linear increase in adipocyte EPA concentration (P < 0.01). Expression of Δ-9 desaturase mRNA was decreased five- and seven-fold, respectively, following 50 and 100 μM EPA incubation compared to the control. Gene expression of SREBP-1c was decreased by 6- and 18-fold in cells supplemented with 50 and 100 μM EPA, respectively, compared to the control. Regression analysis showed a negative linear relationship between EPA concentration and the gene expression of both Δ-9 desaturase (P < 0.001) and SREBP-1c (P < 0.001), while a significant positive relationship was observed between Δ-9 desaturase and SREBP-1c gene expression (P < 0.001). This is the first report demonstrating that EPA treatment of bovine intramuscular adipocyte cells decreased gene expression of both Δ-9 desaturase and SREBP-1cin vitro. The bovine adipocyte cell line developed here is an important resource for future studies facilitating less-expensive, rapid screening of research hypotheses and circumventing the limitations associated with the use of experimental animals including cost, inter-animal variation, pre-experimental management and ethics.

The accurate estimation of protein requirements for beef cattle is a key factor in increasing livestock profitability and decreasing the environmental impacts of excessive N excretion due to mismatching between assumed requirements and diet formulation. A meta-analysis was conducted to evaluate and validate a new equation to predict the net protein requirements for growth (NPg) of Zebu beef cattle. For the development of the new approach, a database of 552 observations comprised of bulls, steers, and heifers of different genetic groups (Zebu, beef crossbreed, and dairy crossbreed) was assembled. The new approach was evaluated and compared to current models devised by the international nutrient requirements system committees (Agricultural Research Council, 1980; Beef Cattle Nutrient Requirements Model, 2016; BR-CORTE, 2016) to predict NPg. The model evaluation was performed through the model evaluation system (version 3.1.16) using an independent data set (n = 177 observations). An equation was considered the best estimator of NPg if the following conditions were met: (1) the intercept and slope of the regression between ordinary residues and/or predicted NPg values must have been equal to zero and one, respectively; and (2) the greatest concordance correlation coefficient (CCC) and determination coefficient (R), and lowest mean squared error of prediction (MSEP) were attained. Based on the regression models of the observed v. predicted NPg of Zebu beef cattle, both the new approach and that of the ARC (1980) correctly estimated NPg, since the intercept and slope were not different (P > 0.05) from zero and one, respectively. Additionally, the new approach’s determination coefficient was the greatest and the closest to one. The fact that the new model achieved a higher CCC and lower MSEP than the existing models indicated its superior reproducibility and accuracy. The equations proposed by BR-CORTE (2016) and the BCNRM (2016) did not correctly estimate NPg in that the intercept and slope were different (P < 0.01) from zero and one, respectively. Thus, the equations proposed by the new approach and the ARC (1980) accurately and precisely estimated NPg and are recommended for Zebu cattle. Furthermore, the inclusion of equivalent empty BW (EQEBW) in the new approach improves the estimation of NPg. We suggest the use of the following equation to calculate NPg for Zebu beef cattle: NPg = 176.01 × EBG – 0.381 × EQEBW0.75 × EBG1.035 (R = 0.80 and CCC = 0.75); where NPg = net protein requirements for growth, EBG = empty body gain, and EQEBW = equivalent empty BW.

Gentle handling seems to elicit positive states in sheep. The study investigated whether spatial distance alters sheep responses to brushing and whether spatial distance is influenced by reactivity. Twenty Romane ewes were assessed in three sessions: in Sessions 1 and 3, one grid separated the test animal from pen mates, with no distance between them, and in Session 2 two grids separated the test animal from pen mates by a distance of about 1.7 m. Ewes had been genetically selected for low (R−) or high (R+) behavioural reactivity to social isolation. Body postures, head orientation, ear postures, closed and half-closed eyes, tail wagging and feeding behaviour, in addition to heart rate (HR) and HR variability, as the root mean square of successive differences (RMSSD), standard deviation of all normal-to-normal (NN) intervals (SDNN), RMSSD/SDNN ratio and ratio between low-frequency (LF) and high-frequency (HF) powers (LF/HF) were assessed. Data were analysed using generalized linear models and linear mixed models. Session, genetic line and phase (pre-, brushing and post-brushing) were considered fixed effects. Increased distance in Session 2 might not have influenced ewes’ responses. Fewer changes in ear postures were noted in Session 3 than 1 (P<0.01), suggesting that ewes were more relaxed in Session 3. The RMSSD/SDNN ratio was higher mainly during brushing in Sessions 1 and 3 (P<0.05), indicating that ewes were more relaxed during brushing, and at no distance between pen mates. However, spatial distance influenced R− and R+ ewes’ responses; R+ ewes performed more asymmetric ear postures in Session 2 than 1 and 3 (P<0.01), and in Session 3 than 1 (P<0.01), indicating that spatial distance had a negative effect on R+ ewes. Low reactive ewes spent less time on horizontal ear postures in Session 2 than 1 and 3 (P<0.01), and R+ ewes spent more time on horizontal postures in Session 1 than 3 (P<0.01). Curiously, R− ewes spent more time eating and ruminating in Session 3 than 1 (P<0.01), and in Session 2 than 1 and 3 (P<0.01), whereas R+ ewes ate and ruminated more in Session 1 than 3 (P<0.05). Higher HR was found among R− ewes in Session 2 than 1 and 3, and in Session 3 than 1 (P<0.01). High reactive ewes showed higher HR in Session 1 than 3 (P<0.01). The findings suggest that the social context might influence sheep responses to gentle handling, and the effects depend on their reactivity traits.

To evaluate how rearing programmes could affect resources allocation and reproductive performance of primiparous rabbit females, a total of 118 rabbit females were used to evaluate the effects of five rearing feeding programmes on their performance from 1st to 2nd parturition: CAL, fed ad libitum C diet (11.0 MJ digestible energy (DE), 114 g digestible protein (DP) and 358 g NDF/kg dry matter (DM) until 1st parturition; CR, fed ad libitum with C diet until 12 weeks of age and then C diet restricted (140 g/day) until 1st parturition; F, fed ad libitum with F diet (8.7 MJ DE, 88 g DP and 476 NDF/kg DM) until 1st parturition; FC, fed with F diet ad libitum until 16 weeks of age, and C diet ad libitum until 1st parturition; FCF, fed with F diet ad libitum until 16 weeks of age, then C diet ad libitum until 20 weeks and then F diet ad libitum until 1st parturition. From 1st parturition, C diet was ad libitum offered to all the experimental groups until 2nd parturition. CAL females presented lower feed intake than females of F, FC and FCF groups in the 1st week of lactation (on av. −16.6%; P<0.05). During 1st lactation, the perirenal fat thickness change in CAL females was not different from 0 (+0.02 mm), while in the other four groups it increased (on av. +0.44 mm; P<0.05). Plasma of females fed with F diet during rearing (F, FC and FCF) had lower non-esterified fatty acids content than those exclusively fed with C diet (–0.088 and –0.072 mmol/l compared to CAL and CR, respectively; P<0.05). FCF litters had higher weight than F litters at day 21 of lactation (+247 g; P<0.05), but FCF litter had significantly lower weight than FC litters at weaning (+170 g; P<0.05). CR females had the shortest average interval between the 1st and 2nd parturition (49 days) and FCF females the longest (+ 9 days compared to CR; P<0.05). At 2nd parturition, liveborn litters of F females were larger and heavier than litters of FCF females (+2.22 kits and +138 g; P<0.05), probably due to the lower mortality at birth of F litters (–16.5 percentage points; P<0.05). In conclusion, rearing females on fibrous diets seems to increase the ability of primiparous rabbit females to obtain resources, especially at the onset of lactation.

The effect of including full-fat Colombian rice polishings, at 250 or 500 g/kg dry matter (DM) or defatted Colombian rice polishings (at 500 g/kg DM) on the fermentation of a basal diet of dried grass and medium-quality hay, in the rumen simulation technique (Rusitec), was investigated. With diets which contained 0, 0·25, 0·50 full-fat or 0·50 defatted, proportions of rice polishing, values for pH were depressed (7·22, 7·19, 7·11, 7·06 (s.e.d. 0·05)) and total volatile fatty acid concentrations were increased (52·8, 52·5, 75·5, 754 (s.e.d. 2·1) mmol/l) at the high levels of inclusion of rice polishings. Concentrations of ammonia (130, 140, 228, 209 (s.e, d. 64) mg/l) and total bacterial numbers (2·32, 2·70, 3·55, 442 (s.e.d. 0·82) × 108 per ml) were elevated by rice polishings inclusion. Numbers of cellulolytic bacteria (2·52, 1·74, 1·84, 2·10 (s.e.d. 0·60) × 106 per ml) and protozoa (19·8, 16·2, 15·8, 22·2 (s.e.d. 1·51) × 103 per ml were depressed (the latter significantly P < 0·01) by the inclusion offull-fat, but not by defatted, rice polishings.

Two feeding trails were made and in both all the diets given contained about 11 MJ metabolizable energy (ME) per kg dry matter (DM).

In trial 1, diets containing three concentrations of crude protein (CP) were given to a total of 84 Friesian bulls in each of three stages of growth. They were, in stage 1 (150 to 250 kg live weight) 130, 145 and 160 g CP per kg dietary DM; in stage 2 (250 to 350 kg live weight) 110, 130 and 145 g CP per kg dietary DM; in stage 3 (350 kg to slaughter) 95, 110 and 130 g CP per kg dietary DM. In stages 2 and 3, the source of supplementary nitrogen at each CP concentration was either soya-bean meal or non-protein nitrogen (NPN) giving six combinations of concentration and source of dietary CP. Live-weight gains in stage 1 were 1·52, 1·60 and 1·58 kg/day respectively (P > 0·05). In the stages involving both concentrations and source of nitrogen (soya-bean meal in parentheses), the mean daily live-weight gains were (1·40), 1·38, (1·32), 1·34 (1·34) and 1·31 kg for stage 2 (F > 0·05) and (1·14), 1·14, (1.24), 1·16, (1·06) and 1·08 kg for stage 3 (P < 0·05), for the diets of 130, 145 and 160 g CP per kg diet respectively.

Trial 2 consisted of six stages of growth, the first five of 45 days duration and the sixth of varying length up to a predicted slaughter weight, and seven dietary treatments. Treatment 1 was a negative control (NC) with a dietary CP concentration of 90 g/kg DM. For the other six treatments two concentrations of dietary CP were given; 120 g/kg and 140 g/kg in stages 1 and 2 and 100 g/kg or 120 g/kg in stages 3 to 6. Dietary CP concentration was increased by the addition of NPN, fish meal or soya-bean meal. A total of 98 Friesian bulls were used with an initial average live weight of 185 kg. Daily gain of the NC group in the six stages of the trial was 0·86, 0·97, 101, 1·13, 1·07 and 1·00 kg for stages 1 to 6 respectively. From the results it was concluded that feeding NPN is not efficient at live weights lower than 250 kg and that there is no advantage to feeding fish meal over soya-bean meal in diets of medium energy concentration at live weights heavier than 250 kg.

In a stochastic simulation study the effect of simultaneously changing the model for prediction of breeding values and changing the breeding goal was studied. A population of 100 000 cows with registrations on seven traits was simulated in two steps. In the first step of 15 years the population was selected for production and mastitis occurrence using a univariate model for prediction of breeding values for production and a trivariate model using information on mastitis treatments, udder depth and somatic cell score for prediction of breeding values for mastitis occurrence. In the second step six different scenarios were set up and simulated for 15 years combining two different breeding goals and three different models for prediction of breeding values in 20 replicates. Breeding goal 1 had relative economic value per genetic standard deviation on production (19.4) and mastitis occurrence ( − 50) whereas breeding goal 2 had a economic value on production (19.4), udder depth (4.2), mastitis occurrence ( − 50), non return rate (13.0) and days open ( − 16.75). Model 1 was a model similar to the one used in the first 15 years. Model 2 was an approximate multitrait model where solutions for fixed effects from a model corresponding to model 1 were subtracted from the phenotypes and a multitrait model with an overall mean, a year effect, an additive genetic and a residual effect were applied. Model 3 was a full multitrait model. Average genetic trends for total merit and each individual trait over 20 replicates were compared for each scenario. With the number of replicates the genetic responses using model 2 and 3 were not significant different. With a broad breeding goal using, model 2 or model 3 gave a significantly higher response in total merit than using model 1. Using a narrow breeding goal there was no significant difference between models used for prediction of breeding values. Results showed that with a breeding goal with a lot of emphasis on low heritable traits with a high economic value using a multitrait methodology for prediction of breeding values will redistribute the genetic progress in the total merit index. More gain will come from the low heritable traits in the breeding goal and less from traits with higher heritability. With a broad breeding goal and exploiting the available information in the data the inbreeding coefficient increased though not significantly.

Cellular mitochondrial function has been suggested to contribute to variation in feed efficiency (FE) among animals. The objective of this study was to determine mitochondrial abundance and activities of various mitochondrial respiratory chain complexes (complex I (CI) to complex IV (CIV)) in liver and muscle tissue from beef cattle phenotypically divergent for residual feed intake (RFI), a measure of FE. Individual DM intake (DMI) and growth were measured in purebred Simmental heifers (n = 24) and bulls (n = 28) with an initial mean BW (SD) of 372 kg (39.6) and 387 kg (50.6), respectively. All animals were offered concentrates ad libitum and 3 kg of grass silage daily, and feed intake was recorded for 70 days. Residuals of the regression of DMI on average daily gain (ADG), mid-test BW0.75 and backfat (BF), using all animals, were used to compute individual RFI coefficients. Animals were ranked within sex, by RFI into high (inefficient; top third of the population), medium (middle third of population) and low (efficient; bottom third of the population) terciles. Statistical analysis was carried out using the MIXED procedure of SAS v 9.3. Overall mean ADG (SD) and daily DMI (SD) for heifers were 1.2 (0.4) and 9.1 (0.5) kg, respectively, and for bulls were 1.8 (0.3) and 9.5 (1.02) kg, respectively. Heifers and bulls ranked as high RFI consumed 10% and 15% more (P < 0.05), respectively, than their low RFI counterparts. There was no effect of RFI on mitochondrial abundance in either liver or muscle (P > 0.05). An RFI × sex interaction was apparent for CI activity in muscle. High RFI animals had an increased activity (P < 0.05) of CIV in liver tissue compared to their low RFI counterparts; however, the relevance of that observation is not clear. Our data provide no clear evidence that cellular mitochondrial function within either skeletal muscle or hepatic tissue has an appreciable contributory role to overall variation in FE among beef cattle.

Combinations of two high-energy forage finishing diets and two initial body condition scores (BCSs) in a 2 × 2 factorial experimental design were evaluated on cull Holstein–Friesian (HF) cows to improve animal performance and carcass characteristics, aimed at achieving proper fatness and conformation scores (a minimum of ‘4’ and ‘O’, respectively) required for the marketing of high-value loin steaks. The two finishing diets were (i) conventional maize silage complemented with concentrate diet and (ii) wet maize ear silage (pastone) complemented with dry-herbage diet. The two initial body condition levels were (i) low BCS < 5 (LBCS) and (ii) high BCS > 5 (HBCS). The HBCS animals had the greatest potential to respond to the finishing diets. They needed a smaller total feed intake (TFI) and a shorter finishing period (FP) to meet the marketing requirements. The average feed budgets necessary to finish cull dairy cows and to achieve the minimum scores ‘4’ and ‘O’ of carcass classification were 2.31 and 3.61 t of dry matter (DM)/cow for HBCS and LBCS animals, respectively, while the FP lasted an average of 143 and 224 days for HBCS and LBCS animals, respectively. With regard to the two feeding diets, we found no differences for TFI, carcass characteristics and loin muscle features, such as weight, diameter and intramuscular fat.

1. Two-thousand and sixty serum samples from indigenous cattle in Central Africa were examined for serum transferrin type. The breeds studied were Manguni, Mashona, Tuli, Angoni and Afrikander.

2. The variation in gene frequencies from breed to breed is presented. With the exception of one Angoni herd, the remaining herds fall into distinct breed groups.

3. The Mendelian hypothesis was tested on eight herds including at least one herd of each breed. With two exceptions good agreement with this hypothesis was obtained. The two exceptions were traced to two bulls, a Mashona (TfB/TfD) and a Tuli (TfD/TfF), both of which contributed TfD to their progeny at a rate in excess of Mendelian expectation.

4. The Hardy-Weinberg equilibrium hypothesis was tested for thirteen herds and good agreement was obtained in all cases.

5. In Angoni cattle no evidence was found to reject the hypothesis of independent segregation at the haemoglobin and transferrin loci.

Two in vitro experiments were conducted in order to determine if microbial fermentation of Eragrostis curvula hay is depressed by high levels of added tallow. Two levels of tallow, to reach 0.06 (T6) and 0.12 (T12) of the ether extract (organic matter basis) in food were compared with a control (T0, 25 g ether extract per kg). The first experiment studied the pattern of gas production. From 24 h onwards, gas volume for T0 was higher (P < 0.05) than for T6 and T12. However, lag time was shorter with tallow, probably because of utilization of the released glycerol. Fermentation of a similar amount of fat included in T6 and T12 as the only substrate (fat-6 and fat-12) depressed gas production compared with the blank, irrespective of fat level. In a second experiment, characteristics of microbial fermentation were studied, including volatile fatty acid (VFA) production, bacterial adhesion to fibrous particles (measured according to purine bases concentration) and polysaccharidase and glycosidase activities, at 6, 12, 24 and 48 h incubation. Total VFA was higher (P < 0.05) in T0 compared with T6 but not with T12. Acetate: propionate ratio diminished with tallow in the food. Higher total xylosidase (P > 0⋅05) and glycosidase (P < 0⋅001) activities were observed for T0 than for T6 and T12 and similar responses were observed regarding specific activities. Bacterial adhesion was not different between T0 and T6 but it was smaller in T12. The inhibition of microbial fermentation by tallow addition is more related to specific polysaccharidase and glycosidase activities, rather than to a depressed bacterial adhesion.

The birth weight and growth rate of sucking calves reared by three groups of cows grazing on veld and receiving different amounts of concentrates during winter and the first 8 weeks of lactation were studied over four successive calving seasons. Calves were weaned at either 150 or 240 days. The efficiency of use of concentrates for weaned calf production was calculated.

Calves from cows given most concentrates were heavier (P<0·01) than othei calves at birth, 150 days and 240 days. Milk consumption during the first 98 days of life accounted for most of the variation in pre-weaning growth. Time of weaning had little effect (P<0·05) on birth weight of the next year's calf and although cows in the early- weaning groups produced calves which were the heaviest at 150 days (P>0·05) these calves weighed less than other calves at 240 days (P<0·001). Simple and multiple regression analyses were used to show that birth weight was affected significantly by cow-weight change during winter and these differences were in part independent of treatment and year. Calf birth weight increased as age of dam increased but this was due to increase in weight of cow with age. Within classes, calf birth weight had a significant and positive effect on weight gain after accounting for milk consumption and this was shown to be an effect of sex. Cows given concentrates produced more weight of 240-days-old weaned calf per year than those given none (P<0·01), and late weaning led to the production of more weaned calf per annum than early weaning (P< 0·001) even when allowance was made for differences in concentrate consumption.

In formulating a genetic index for use in cow and sire evaluation, there is a need to account for all environmental factors which influence an animal's yield. To this end, milk production records are currently adjusted for, amongst other things, age at calving and month of calving. In Norway, Sweden and West Germany, records are corrected for calving interval, i.e. the number of days between subsequent calvings (Philipsson, Dommerholt, Fimland, Gaillard, Gjøl-Christensen, Lederer, McClintock and Mocquot, 1978), but in Britain no account is taken of calving interval or days dry. Analysis has shown (McClintock, 1982) that both these factors have a significant effect on yield, and hence further investigation into the value and methods of adjusting for these factors was required.