Group housing of gestating sows benefits their welfare by allowing them freedom of movement and the opportunity for social interaction. However, social life could also bring disadvantages for individuals who receive direct aggression or are displaced from the feeder. The aim of this study was to investigate associations between social behaviour, body condition and live weight. Gestating sows (n=298) were investigated on a commercial farm. Sows were housed in mixed parity groups where two single space, ad libitum trough feeders served 12 animals. Sows were weighed, body condition scored and had their back fat layer measured at mixing, 4 weeks after insemination and again before farrowing. Social status was estimated based on the numbers of won and lost agonistic interactions at mixing and at the end of gestation. In addition, tear staining was scored before the farrowing and reproductive performance data were collected. With the aid of video recordings, 100 to 150 interactions per group were observed. Winning percentage at mixing and at the end of gestation were associated (P<0.05) and appeared relatively stable within individuals. Tear staining scores and litter sizes were not associated with winning percentage at the end of gestation. However, live weight, relative weight, body condition and back fat thickness were associated with winning percentage (P<0.05), giving heavier animals an advantage. Low winning percentage related to lower live weight gain, probably due to poorer success in competition for feed. Live weight within a mixed parity group could be used as a proxy measure for social status. Sows with low body condition score and submissive sows might need special attention with regard to group dynamics and housing to alleviate the effects of competition in group housing.

Pesticides can significantly harm reproduction in animals and people. Pyrethroids are often used as insecticides, and their toxicity for mammals is considered to be low. However, cypermethrin, deltamethrin and fenvalerate – as potent specific inhibitors of protein phosphatase calcineurin – can influence the meiosis of mammalian oocytes. The objective of this study was to evaluate the effects of these pyrethroids on the in vitro maturation of pig oocytes at different levels of meiotic competence. Under the tested concentrations, cypermethrin, deltamethrin and fenvalerate neither had a significant effect on the viability of oocytes nor did they induce significant degeneration of oocytes. However, these pyrethroids significantly affected meiotic maturation. The effects depended on the stage of meiotic competence of the oocytes. Maturation of growing pig oocytes with partial meiotic competence was induced. On the other hand, in fully grown pig oocytes with full meiotic competence, maturation in vitro was delayed. The specificity of these effects was further supported by the same effect of non-pyrethroidal inhibitors of calcineurin – cyclosporin A or hymenistatin I – on the maturation of oocytes with different levels of meiotic competence. However, pyrethroids, which do not inhibit calcineurin – allethrin or permethrin – had no effect on pig oocyte maturation. We demonstrated a significant effect of pyrethroids on the maturation of mammalian oocytes under in vitro conditions. This indicates that exposure to these substances could affect the fertility of people or animals.

Three concentrate mixtures were compared in a replicated 3 × 3 Latin square feeding trial with cows in early lactation to evaluate the effect of inclusion of tallow. The concentrates were based on barley and soya bean meal (223 g crude protein per kg dry matter) with either no tallow addition (control group) or with the addition of a protected tallow premix (0·75 spray-dried formaldehyde-treated tallow, 0·25 casein) or an unprotected tallow premix (0·75 spray-dried tallow, 0·25 casein), both added at 138 g/kg. Each concentrate was given at a rate of 8 kg per cow per day and silage was offered ad libitum. The inclusion of unprotected tallow in the concentrate did not significantly change milk yield, fat concentration, lactose concentration or live weight compared with those in the control group. The inclusion of the protected tallow supplement resulted in significantly higher yields of milk (22·9 kg/day), fat (0·95 kg/day) and lactose (1·05 kg/day) compared with those of the control group (21·3 kg/day, 0·79 kg/day, 0·95 kg/day), whilst milk protein concentration was significantly reduced. A digestibility trial with steers showed that, when hay was given with the diets, inclusion of tallow in the concentrate significantly increased the digestible and metabolizable energy concentration of the diets compared with the control diet, but dry matter, energy and fibre digestibility was reduced.

Twelve 6-month-old growing female goats and sheep were used in this study. Blood samples were obtained in the morning before goats and sheep were given food and then at 2-h intervals for 24 h (part I). This procedure was repeated 2 weeks later (part II). Concentrations of osteocalcin (OC), activities of total (tAP) and bone-specific alkaline phosphatase (bAP), degradation products of C-terminal telopeptide of type-I collagen (CrossLaps™ CL), and carboxyterminal telopeptide of type-I collagen (ICTP) were measured in serum.

In both parts of the study, all bone marker concentrations were significantly higher in goats than in sheep. The OC concentrations in goats increased in the late afternoon/evening and decreased thereafter to reach values similar to those obtained at the beginning. The ICTP concentrations in goats slowly decreased until 14:00 h, increased, and decreased again. The concentrations in sheep decreased continuously but not significantly, towards the morning sampling. The CL concentrations increased in both sheep and goats during the night but at 06:00 h started to decrease to levels found at the beginning of testing. The bAP activities decreased in goats from 20:00 to 22:00 h. Changes in the concentrations of bone markers were mainly observed in goats of this study. As documented for bone resorption and formation in other species, circadian rhythms were evident for concentrations of ICTP, CL, bAP and OC. The present study indicates that growing goats may have a physiologically higher bone turn-over than growing sheep, because the bone marker concentrations were always higher.

Selection decisions in breeding schemes can involve choices between candidates evaluated to different accuracies. A Bayesian framework is put forward for choosing among candidates, and it is shown that attaching loss functions for estimation errors makes this process different from selecting upon best linear unbiased predictions alone. Examples are given using both linear and quadratic loss to show that when estimation errors are penalized, the selection process tends to select more unrelated and more accurately evaluated individuals. In a dairy cattle breeding scheme response was only slightly lower than that from selection on expected breeding values but with a much reduced coefficient of variation. However, if prediction errors are preferred, with the hope of selecting individuals whose breeding value are higher than expected, extra genetic progress could be obtained by favouring the selection of individuals with low accuracy. This requires consideration of more than a single generation.

With discrete generations and equal measurements on candidates the decision framework was shown to be equivalent to a single quadratic restriction on the selection scores of parents in the previous generation.

A framework based on Bayes decision theory could be simply applied to produce a flexible means for producers to select according to their individual risk preferences.

Three groups of 16 cattle each comprising three multiparous Jersey cross Holstein-Friesian cows, seven primiparous and six multiparous Holstein-Friesian cattle were offered, ad libitum, a silage-based complete diet with different concentrate ingredients following an initial 3-week covariate period. The relationship between these three diets and other parameters with lesions of the weight-bearing surface of the hoof was studied by scoring mobility weekly (locomotion score) and examining all the feet of all cows for visual lesions particularly those involving the horn of the foot. In addition hoof angle, hardness and growth and wear were also recorded. The mean locomotion score during the initial 3-week covariate period was a significant covariate for the subsequent locomotion score, milk yield, and live weight (P < 0·001). Furthermore weekly locomotion score also proved a significant covariate for weekly milk yield (P < 0·05). There were no significant differences between dietary treatment groups for locomotion score, overall lesion score (despite significantly fewer ulcers of the sole in one dietary group: P < 0·001) but a significant (P < 0·05) difference between cow ‘type’ and there was also a significant (P < 0·05) diet × breed interaction for locomotion score and milk yield. It was concluded first that initial mobility was an important factor in subsequent mobility of the cow and so experimental design; secondly that while nutrition and genotype interacted to influence mobility, visual lesions of the hoof and lameness, the mechanisms involved were far from clear; and thirdly that the simple lesion score used required some adjustment or correction factor(s) to ensure that more severe lesions were given a greater weight than a simple unitary increase.

1. British Friesian (F) and Hereford × British Friesian (H × F) male calves were raised from about 3 days to 8 weeks of age at air temperatures of 5, 10 or 15°C. They were given a milk replacer diet supplying 950 kJ metabolizable energy/kg M0·75.24 h.

2. There was no effect of environmental temperature on weight gain in calves of either type.

3. Total heat loss measured in a direct calorimeter, increased by about 5 kJ/kg M0·75.24 h per °C fall in air temperature. It was the same whether calves were penned singly or in pairs. Heat loss from F calves was slightly, but not significantly, greater at all temperatures than from H × F calves.

4. The proportion of heat lost by evaporation (a measure of environmental warmth) increased with increasing air temperature and was greater for H × F than for F calves at 15°C.

5. Tissue insulation and external insulation values were similar for H × F and F calves. The calculated lower critical temperatures of the F and H × F calves were 10 and 8°C respectively.

6. The results are discussed in relation to the housing requirements of young calves.

In two experiments over 2 years, 113 North Country Cheviot and 132 South Country Cheviot hill ewes were differentially group-fed over a 10-week period to achieve either good or moderate body con- dition. Ewes were maintained in these levels of condition over the 5 weeks prior to mating. After mating, ewes were killed either on return to service or between days 23 and 85 for counts of corpora lutea and viable embryos.

Ovulation rate in each breed was positively related to body condition at mating. Embryo mortality, as ova loss, was not influenced overall by breed, type of ovulation, year of recording, or body condition. Although comparisons of loss were partly confounded by a differen- tial distribution in the number of ova shed in each breed and body condition group, there was an apparent breed difference in loss of single- and multiple-shed ova. Potential lambing rate therefore showed greater response to improved body condition at mating in the North Country Cheviot breed than it did in the South Country Cheviot.

The generation of profit in dairy production can be approximated by a generalized profit equation, which is a function of the genotype of the animals used. In the absence of legislated quotas on production, the economic weights for traits contributing to profit, for use in a selection index, have been shown to be simple functions of the partial derivatives of profit with respect to output of the traits. These functions reflect the fact that output in most agricultural industries will already be maximized, either because of saturated markets or limitations on total inputs. When a single quota applies, different functions result, which reflect the downward rescaling of enterprise size as output per animal of a trait under quota is increased. Difficulties arise when multiple non-independent quotas apply, such as in the United Kingdom (UK) milk market where quotas are triggered by both milk volume and fat concentration. The functions describing the economic weights are then dependent on the form of the dependency between the quota criteria and on the genetic change resulting from the applied selection index. Economic weights for milk volume, fat, protein and lactose yield applicable to Holstein'Friesian cattle in the UK were found to be –1·6 p/1, 76·6 p/kg, 170·0 p/kg and 7·0 p/kg, scaled to 1986 prices. These weights would not change much if the quota were changed to fat yield only. Use of appropriate selection indexes should result in genetic increases of milk volume, fat, protein and lactose yield, with gradual increases in fat and protein concentrations and the fat to protein ratio. In most situations, selecting on the combined evaluation for fat plus protein yield would be a simple procedure with high efficiency (0·995 of maximum efficiency).

The influence of breed and sex on relative growth patterns of muscle, bone and fat in beef cattle has been investigated. Comparisons were made of growth coefficients estimated using Huxley's (1932) allometric equation relating muscle, bone or fat to muscle plus bone using data from the dissection of half carcasses of 63 young bulls, 106 steers and 22 heifers representing a number of breed groups. Growth coefficients for muscle and for bone were found to be similar among different breed groups of bulls, steers and heifers. The proportion of muscle increased and that of bone decreased as the size of animal, measured by muscle plus bone, increased. Muscle and bone weights adjusted to common muscle plus bone weights were significantly different among breed groups within sex. Differences in amount of muscle relative to bone were therefore established at earlier stages of growth and maintained over the period represented in the present study.

Growth coefficients for fat were significantly different among breed groups within sexes.

Sex within breed group had no statistically significant influence on growth coefficients for muscle or for bone. Muscle and bone weights adjusted to a common muscle plus bone weight were similar for sex groups within all breed group comparisons. Sex did not have a marked effect on rate of fattening since differences between growth coefficients for fat (between sexes, within breeds) were not statistically significant—although in all comparisons growth coefficients for fat were lowest for bulls, intermediate for steers and highest for heifers. Sexes differed in weight of fat adjusted to common muscle plus bone weight, heifers being fatter than steers and steers fatter than bulls, a difference probably resulting more from early onset of the fattening phase in heifers, followed by steers, rather than relative rate of fattening.

In order to evaluate the effect of exercise training and spontaneous physical activity on growth performance, carcass composition, and locomotory ability 48 female and 48 entire male pigs were subjected to one of three treatments: individual housing in pens of 2-5 m2 (confined; C), individual housing and treadmill training for 15 minlday at a speed of 4 km/h, 5 days/week for a period of 70 days (trained; T) and group-housing equal to 0·9 m2 per animal (free; F). Pigs in treatment C and T did not differ with regard to daily gain, food intake, kg food per kg gain and carcass lean content. Training did, however, induce significant cardiac hypertrophy (by a proportion of 0·06). In treatment F (i.e. large pens), daily gain was 135 g lower than in treatment C. Dissection of the carcasses showed that treatment F increased the weight of m. psoas major (by 30 g) and the total carcass bone mass (by 130 g) when compared with treatment C. Proportions of carcass lean and intramuscular fat were unaffected by treatment F. Likewise, leg weakness and osteochondrosis did not differ between treatments, whereas the locomotory ability was positively affected by rearing in large pens (treatment F) but not by treadmill training (treatment T). Thus, physical activity in large pens induced various adaptations throughout the body.

Commercially farmed animals are frequently housed in conditions that impose a number of concurrent environmental stressors. For pigs housed indoors, elevated levels of mechanical noise, atmospheric ammonia and low light intensities are commonplace. This experiment examined the effects on growing pigs of chronic exposure to combinations of commercially relevant levels of these potential stressors. Four-week-old hybrid female pigs (n = 224) were housed under experimentally manipulated conditions of nominally either <5 or 20 ppm atmospheric concentration of ammonia (24 h), a light intensity of 40 lux or 200 lux (12 h) and mechanical noise at either ⩽60 or 80 dB(A) (24 h) for 15 weeks in a fully factorial arrangement (23) of treatments. The response of pigs to these environmental factors was assessed using a suite of physiological, production and behavioural measures. These included indicators of hypothalamic–pituitary–adrenal (HPA) axis activation such as salivary cortisol and adrenal morphometry, as well as body weight, food conversion efficiency and general health scores. Play behaviour was recorded as it is thought to be inversely related to stress. Chronic exposure to ammonia produced the strongest effect, shown by lower concentrations of salivary cortisol and larger adrenal cortices in the pigs reared under 20 ppm ammonia, which may have been indicative of a period of HPA activation leading to a downregulation of cortisol production. The pigs in the ammoniated rooms also performed less play behaviour than pigs in non-ammoniated rooms. There was evidence for an interaction between high noise and ammonia on the health scores of pigs and for brighter light to ameliorate the effect of ammonia on salivary cortisol. However, there was no measurable impact of these potential stressors on the productivity of the pigs or any of the other physiological parameters measured. We conclude that there should be little concern in terms of performance about the physical stressors tested here, within current European Union legal limits. However, 20 ppm ammonia may have had an adverse influence on the well-being of growing pigs. In this study, all other aspects of the pigs’ husbandry were optimal; therefore, it is possible that under less favourable conditions, more pronounced effects of ammonia, noise and dim light would be observed.

Standard feeds are imbalanced in term of n-6/n-3 polyunsaturated fatty acids (PUFA) ratio, with a low proportion of the latter. The reproductive system appears to be strongly affected by administration of n-3 PUFA, and ingredients rich in α-linolenic acid (ALA; i.e. vegetable sources) or EPA and DHA acids (i.e. fish oil) can be included in animal diets to balance PUFA intake. The aim of this study was to evaluate the effect of dietary supplementation with flaxseed (ALA) or fish oil (EPA and DHA) on PUFA metabolism in rabbit does. A total of 60 New Zealand White female rabbits were assigned to three experimental groups: control group, FLAX group fed 10% extruded flaxseed and FISH group fed 3% fish oil. Blood, milk, liver and ovaries were collected from the does to assess the lipid composition; furthermore, FADS2 gene expression was assessed in liver and ovary tissues. Reproductive performance of does was also recorded. The fertility rate and number of weaned rabbits improved with n-3 dietary supplementation: does at first parity showed the lowest reproductive results, but the administration of n-3 reduced the gap between primiparous and multiparous does. Feed consumption and milk production were not affected by the feeding regime. The fatty acid composition of milk, plasma, liver and ovaries were widely influenced by diet, showing higher concentrations of n-3 long-chain PUFA (LCP) in does fed with n-3 enriched diets. FISH diet resulted in the highest n-3 LCP enrichment, whereas in the FLAX group, this increase was lower. Blood and milk showed low levels of LCP, whereas liver and ovaries were the main sites of n-3 LCP synthesis and accumulation. Accordingly, although the liver is the main metabolic centre for LCP synthesis, ovaries also have a prominent role in LCP generation. FADS2 expression in liver and ovary tissue was downregulated by FISH administration. In conclusion, the enrichment of diets with n-3 PUFA could be an effective strategy for improving the reproductive performance of does.

Primary bovine mammary epithelial cells (BMEC) were cultured in media containing varying concentrations of glucose, to determine the effects of glucose availability on glucose transport and its mechanism in bovine mammary gland. The BMEC incubated with 10 and 20 mM glucose had twofold greater glucose uptake than that with 2.5 mM glucose (P < 0.05). Increased glucose availability enhanced the cell proliferation (P < 0.05). As the glucose uptake is mediated by facilitative glucose transporters (GLUTs), the expression of GLUT mRNA was investigated. Compared with the control (2.5 mM), 5 and 10 mM glucose did not influence the abundance of GLUT1 mRNA (P < 0.05), whereas 20 mM glucose decreased the GLUT1 mRNA expression in the BMEC (P < 0.05). The expression of GLUT8 mRNA was not affected by any concentration of glucose (P > 0.05). As GLUTs are coupled with hexokinases (HKs) in regulating glucose uptake, the expression of HKs and their activities were also studied. The HK activity was greater in 5, 10 and 20 mM glucose than that in 2.5 mM glucose (P < 0.05). The expression of HK2 mRNA rather than HK1 mRNA was detected in the BMEC; however, the abundance of HK2 mRNA was not elevated by any concentrations of glucose compared with control (P > 0.05). Furthermore, addition of 3-bromopyruvate (30, 50 or 70 μM), an inhibitor of HK2, resulted in the decrease of glucose uptake and cell proliferation at both 2.5 and 10 mM glucose (P < 0.05). Therefore, the glucose concentrations may affect glucose uptake partly by altering the activity of HKs, and HK2 may play an important role in the regulation of glucose uptake in the BMEC.

An experiment (complete randomised design) was conducted to investigate the effects of supplementing different molecular weights (MW) of chitooligosaccharide (COS) on pig performance, selected microbial populations and nutrient digestibility post-weaning. A total of 396 weaned piglets (24 days of age, 7.3 kg ± (s.d.) 1.7 kg live weight) were assigned to one of six dietary treatments (22 replicates/treatment) for a 33-day experimental period. The dietary treatments were as follows (1) control diet (0 ppm COS), (2) control diet plus <1 kDa COS, (3) control diet plus 3 to 5 kDa COS, (4) control diet plus 5 to 10 kDa COS, (5) control diet plus 10 to 50 kDa COS and (6) control diet plus 50 to 100 kDa COS. The COS were included at 250 ppm in the diets. There was no significant effect of dietary treatment on piglet performance during the starter period (days 0 to 18; P > 0.05). However, there were quadratic responses in both daily gain (P < 0.05) and gain to feed ratio (P < 0.05) to the increased MW of COS inclusion during the weaner period (days 18 to 33) with all COS-supplemented treatments improving daily gain and gain to feed ratio compared with the control. There was a quadratic response in faecal scoring to the increased MW of COS inclusion from days 0 to 7 (P < 0.001), days 7 to 14 (P < 0.001) and during the overall experimental period (P < 0.01) with all the COS-supplemented treatments having an improved faecal score compared with the control. During the weaner period, there was a cubic response in lactic acid bacteria and Escherichia coli populations as the MW of COS increased (P < 0.05). The 5 to 10 kDa and 10 to 50 kDa COS increased lactic acid bacteria populations compared with the control, whereas lactic acid bacteria populations decreased at 50 to 100 kDa. The 5 to 10 kDa, 10 to 50 kDa and 50 to 100 kDa COS decreased E. coli populations compared with the control. There was a cubic response in the apparent total tract digestibility of dry matter (DM; P < 0.01), organic matter (OM; P < 0.01), ash (P < 0.01), nitrogen (N; P < 0.01) and gross energy (GE; P < 0.01) to the increased MW of COS inclusion during the weaner period. The 5 to 10 kDa COS had a higher apparent total tract digestibility of DM, OM, ash, N and GE in comparison to the control, whereas the apparent total tract nutrient digestibility of these nutrients decreased at 10 to 50 kDa. The current results indicate that the MW ranges of 5 to 10 kDa and 10 to 50 kDa COS decreased E. coli numbers while increasing nutrient digestibility of the diets.

This in vitro study aimed at understanding how abiotic, that is chemical and electrochemical potentials, and biotic factors combine to impact the outputs of rumen volatile fatty acid (VFA). Using a 48-run design optimized by means of an exchange algorithm, the curvilinear effects of pH, Eh and partial pressure of dihydrogen (H2) on fermentation yields were investigated in 6-h batch cultures of mixed rumen microbes, fed on glucose so as to bypass the enzymatic hydrolysis and conversion steps preceding the glycolytic pathway. The role played by rumen microbiota in the expression of these effects was explored by testing three inocula grown on feeds supplying a microflora adapted to fibre, slowly degradable or readily degradable starch as the dominant dietary polysaccharide. Data were fitted to 2nd-order polynomial models. In fibre-adapted cultures, the yields of major VFA were mainly influenced by pH and H2 partial pressure, in opposite ways. In wheat grain-adapted cultures, the VFA yields underwent the opposite influences of pH, in a curvilinear way for propionate, and Eh since acetate production yield was not significantly modified by any factor. In maize grain-adapted cultures, acetate production yield was not modified by any factor but H2 in a quadratic way when the production yields of higher VFA underwent opposite influences of pH and Eh. In conclusion, the effects of environmental factors were dependent on the nature of the inoculum, a major source of variation, and more particularly on its adaptation to high- or low-fibre diets. These effects were loosely interrelated, the pH being the most active factor before the Eh and H2 partial pressure.

This work was conducted to evaluate the effect of tannins, contained in a by-product derived from olive oil extraction (two-stage olive cake), on nutrient digestibility, nitrogen (N) losses and liver and kidney functions in goats and wethers. Six Segureña wethers and six Granadina goats were fed three experimental diets: alfalfa hay (AH); alfalfa hay and a concentrate (formulated with two-stage olive cake, barley and a mineral-vitamin mixture) without (AHCO) or with polyethylene glycol (PEG) addition (AHCOP). The inclusion of two-stage olive cake increased condensed tannins content of the diet and led to a decrease ( P < 0.001) in dry matter, organic matter, neutral-detergent fibre, acid-detergent fibre and crude protein (CP) digestibility. PEG supply increased ( P < 0.001) CP digestibility and N losses in urine and faeces only in wethers. Concentrations of creatinine and alkaline phosphatase activity, measured in the serum of animals, were not modified either by olive cake inclusion or by PEG supply. Results from this work indicate a higher sensitivity of sheep to diets containing condensed tannins, compared with goats, and reveal no toxic effect of tannins from two-stage olive cake at the concentration used in the experimental diets.

Poultry meat is a valuable source of nutrients and the enrichment with health-promoting substances such as polyunsaturated fatty acids (n-3 PUFA) is an important factor for consumers’ choice. Camelina meal (Camelina sativa) is an animal feedstuff used to achieve this goal, but the administration of n-3 PUFA-enriched diets in broiler nutrition can accelerate the oxidative processes in meat leading to a decreased quality of final product. The aim of this study was to investigate the effect of the organic Cr as chromium picolinate (CrPic) on meat quality, fatty acid profile of fat and oxidative stability of meat from broilers fed supplemented dietary Camelina meal. An experiment was conducted on 240 Ross 308 broiler chicken aged 14 days which were assigned to 6 dietary treatments in a randomized complete block design with a 2 × 3 factorial arrangement. Within the treatment arrangement two concentrations of Camelina meal (0% and 3%) and three concentrations of Cr3+ (0, 200 and 400 μg/kg) were used. Dietary treatments were: (1) Control diet (C) containing a corn–soybean diet with no added Camelina meal or Cr3+; (2) a C diet containing an additional 200 μg/kg of Cr3+ as CrPic; (3) a C diet containing an additional 400 μg/kg of Cr3+ as CrPic; (4) a C diet containing an additional 3% Camelina meal; (5) diet 2 containing an additional 3% Camelina meal; (6) diet 3 containing an additional 3% Camelina meal. Chromium supplementation significantly (P<0.05) increased the CP concentrations and significantly (P<0.05) decreased the crude fat concentrations in breast samples. The Camelina meal groups presented higher values of unsaturated fatty acids, particularly n-3 fatty acids (P<0.05). In CrPic groups, increased retention of Zn and Fe (P < 0.05) was observed in breast samples, compared to control group, and thiobarbituric acid reactive substances values were significantly (P<0.05) smaller. Myoglobin fraction (metmyoglobin and oximyoglobin) concentrations differ significantly (P<0.05) from the control group, under the influence of Cr3+ supplements. This study found that broilers fed with CrPic supplements showed improved mineral composition and oxidative stability of breast meat, proving an effective protection of lipid molecules from oxidation in PUFA-enriched meat.

The extent of the genetic differences existing among a sample of the dairy herds of New Zealand was assessed by a direct experimental approach. In part one of the experiment, 240 young calves were taken from 40 herds of markedly different production levels and reared and milked as a uniformly treated herd of cattle at Ruakura. In part two of the experiment 120 sets of identical twin calves were divided amongst these 40 high- and low-producing herds.

Results indicated that in general there were no obvious genetic differences between the cattle in the high and low herds in body size, fertility, milk production or days in lactation. There were, however, genetic differences between the high and low herds in milk composition; approximately 50% of the differences between herds in butterfat and protein content and 25% of the SNF content were due to genetic differences between herds.

Genetic differences between herds in yield were found within the high group of herds but not in the low.

Evidence was obtained indicating that interactions between herd environment and the genotype of individual animals provided an appreciable source of variation.

The production level of a herd in which an animal was reared was without effect upon its subsequent production potential for milk yield.

It has been estimated (Mason, 1963) that about 70% of beef stores bred in Britain are out of dairy cows. Some 30–40% of them are by beef bulls, so that about 40–50% of animals slaughtered for beef are of pure dairy breeding.