Danish holsteins favor bull offspring: biased milk production as a function of fetal sex, and calving difficulty

In a previous study from 2014 it was found that US Holstein cows that gave birth to heifer calves produced more milk than cows having bull calves. We wanted to assess whether this is also true for Danish cattle. Data from 578 Danish Holstein herds were analysed with a mixed effect model and contrary to the findings in the US, we found that cows produced higher volumes of milk if they had a bull calf compared to a heifer calf. We found a significantly higher milk production of 0.28% in the first lactation period for cows giving birth to a bull calf, compared to a heifer calf. This difference was even higher when cows gave birth to another bull calf, so having two bull calves resulted in a difference of 0.52% in milk production compared to any other combination of sex of the offspring. Furthermore, we found that farmer assisted calvings were associated with a higher milk yield. Cows with no farmer assistance or with veterinary assistance during the most recent calving produced less milk. There were also indications that dams would favor a bull fetus by decreasing milk production during the second pregnancy if the calf born in the first parity was a heifer. We hypothesize that size of calves is a confounding factor for milk production. However, calving weight was not available in the present data set to test this hypothesis.

Iron deficiency screening in the first three years of life: a three-decade-long retrospective case study

A three-decade-long retrospective study of iron status in a cohort of 1250 children aged 8-36 months was carried out at the Pediatric Department at the Second University Naples. Iron status was evaluated with independent variables such as family income, weight for height, introduction of cow's milk (CM), iron supplementation and weaning. Iron deficiency (ID) is prevalent in children with low income, early introduction of CM, delayed weaning, over-weight, and in those not receiving iron supplementation (P < 0.05). The first decade (1980-1990) was marked by low family income, while early introduction of CM characterized the first two decades (1980-1990, 1990-2000) (P < 0.05). ID depends on a variety of social and dietary factors. Hematological tests should be performed early to identify children at risk for ID.

Cariogenicity of different commercially available bovine milk types in a biofilm caries model

PURPOSE

This study's purpose was to assess the cariogenicity of commercial bovine milk types in an experimental biofilm/caries model.

METHODS

Enamel and dentin slabs were used to grow biofilms of Streptococcus mutans UA159. Slabs/biofilms were exposed three times per day to commercial skim, semi-skim, whole, whole lactose-free, and whole with 10 percent sucrose-added bovine milk and to 10 percent sucrose and 0.9 percent sodium chloride as positive and negative caries-control, respectively. Biofilms were analyzed for bacterial counts, biomass, proteins, and polysaccharide production. Slab's demineralization was assessed by loss of surface microhardness and the biofilm acidogenicity by medium pH.

RESULTS

Only whole and whole lactose-free milk kept pH above the demineralization threshold, inducing the lowest demineralization in both enamel and dentin (P<.05). Skim and semi-skim milk induced similar demineralization to the sucrose control, albeit slightly lower for semi-skim milk (P<.05). Whole and whole lactose-free milk produced lower biomass and less insoluble polysaccharides than the other treatments in enamel and dentin (P<.05). Adding 10 percent sucrose to whole milk turned it as cariogenic as 10 percent sucrose solution.

CONCLUSION

Bovine whole milk seemed less cariogenic than sucrose and the other commercial milk types, but not anticariogenic. Fat content in milk seemed to reduce cariogenicity of the fluid.

An effective increase in milk production through triticale feeding

Since the first studies in Algeria in 1999, 2002 and 2005, triticale has been used in arid and semi-arid areas mainly for livestock production. Efforts have been done for the utilization of triticale as hay, silage and hole grain to feed dairy cattle and small ruminants (sheep). Studies have shown that triticale could be easily integrated in the existing crop-livestock system of northern Algeria. In spite of the good results in the yield performance and adaptation to diverse environments, decision makers are not giving the necessary attention to triticale. Dairy cattle holders that tested the crop have adopted it quickly and developed it in an informal way. Now, more than 90% of the triticale seed business is in the hands of private farmers without any help or subsidies nor a good price policy to develop strongly this crop. The utilization of triticale in Algeria is roughly as follow: human consumption 5%, forage crop (hay or silage) 60% and 30% as feed grain, the remaining 5% are kept for sowing seed. In our studies we have compared different feed sources (barley, triticale, concentrate diet and mixtures) to dairy cattle and sheep. Triticale showed highly significantly better results for meat production and gave also an amazing response for dairy and sheep milk production in Algeria. Milk production of animals fed with triticale over exceeded the other feed sources by 26% to 53%; mean weight gain exhibited the same rates.

Low levels of aflatoxin B1, ricin, and milk enhance recombinant protein production in mammalian cells

Gene expression in transduced mammalian cells correlates with virus titer, but high doses of vector for gene therapy leads to toxicity in humans and in animals. Changing the optimal tissue culture medium by adding low levels of environmental stressors, such as 1 µM of the fungal toxin aflatoxin B1 (AFB1), 1 ng of the castor bean protein toxin ricin, or 1% reconstituted milk, enhances transcription and increases production of proteins in transduced mammalian cells as demonstrated by production of the following three recombinant proteins: firefly luciferase, β-galactosidase, and green fluorescent protein (GFP). Higher concentrations of the stress-producing substances damage the cells beyond recovery, resulting in inhibited gene expression and cell death. We also evaluated the effect of the stressor substances on the enhanced infectivity of virus. The presented findings extend methods for large-scale transient recombinant protein production in mammalian cells and suggest that it may be possible to reduce the cytotoxicity of the adenovirus by reducing the virus titer without adversely affecting gene expression levels.

Prevalence and consequences of subacute ruminal acidosis in German dairy herds

BACKGROUND

The prevalence and the clinical consequences of subacute ruminal acidosis (SARA) in dairy cows are still poorly understood. In order to evaluate the prevalence of SARA, 26 German dairy farms were included in a field study. In each herd, between 11 and 14 lactating dairy cows were examined for their ruminal pH using rumenocentesis. Milk production data and farm management characteristics were recorded. Each farm was scored for lameness prevalence among lactating animals, and body condition score was recorded three times four to five weeks apart in all animals examined. Farms were grouped on basis of ruminal pH and compared for lameness, body condition, milk production parameters and style of management. Animals were grouped on basis of their measured ruminal pH and compared accordingly for milk production parameters and body condition score.

RESULTS

Of 315 cows examined, 63 individuals (20%) exhibited a ruminal pH of ≤ 5.5 at time of rumenocentesis. Of 26 farms examined, eleven farms had three or more of their cows experiencing a ruminal pH of ≤ 5.5 and were classified as likely experiencing subacute ruminal acidosis. These farms tended to be bigger than the others and offered less lying space to the lactating cows. There was no clear tendency regarding lameness. Among individual cows, animals with a low ruminal pH of ≤ 5.5 were found to be in significantly poorer body condition than animals with higher pH values (p < 0,05).

CONCLUSIONS

The study shows 11 out of 26 of herds likely experiencing SARA. Bigger herds tend to be at a higher risk for SARA, while individuals with low ruminal pH tend to be lower in body condition. The study points to the importance of management in preventing SARA.

Effects of different polyunsaturated fatty acid supplementations during the postpartum periods of early lactating dairy cows on milk yield, metabolic responses, and reproductive performances

In spite of the difficulties in delivering PUFA to ruminants, studies have generally indicated that the PUFA of the omega-6 (linoleic acid) and omega-3 [α-linolenic acid; eicosapentaenoic (EPA), C20:5 omega-3; docosahexaenoic (DHA), C22:6 omega-3] families are the most beneficial to improving reproduction in cows. The objectives were to determine if a diet enriched in α-linolenic acid (omega-3) or linoleic acid (omega-6) would influence milk production and composition, metabolic status, and reproductive performance in lactating dairy cows. High-yielding multiparous Holstein dairy cows (n = 120) with no overt clinical illnesses were blocked according to calving date and parity. Cows were assigned randomly to be fed 1) soybean whole roast (Soy, omega-6, n = 40) or 2) linseed (Lin, omega-3, n = 40) or 3) palm oil as a source of SFA (PO, n = 40) from calving until first heat after 40 d postpartum (dpp), and then half of the cows in each treatment group were switched to receive either Lin or SFA (PO) from first heat after d 40 to 120 dpp. Blood was collected from a subsample of cows. Blood was collected at 14 d intervals for 12 wk, starting on the day of calving. Results showed milk yield and DMI were not affected. Milk compositions were similar (P > 0.08) among diets, except concentration and yield of milk fat percentage, which was less in cows fed Lin (P < 0.05). Uterine involution in cows fed Soy occurred earlier (P < 0.05). Diets affected day to first estrus and day to first insemination in cows (P < 0.05). There were no differences among treatments for percent heat detection, percent pregnancy per first insemination, and percent conception per AI at estrus. Also, there is a trend of pregnancy by 120 d, which is 66.7% for the Lin group vs. 50.91% for the PO group (P < 0.08). Of the 4 pregnancy losses, 2 occurred in PO-PO group and 2 occurred in Soy-PO group, and none occurred in the other 4 treatments. In conclusion, our study showed feeding omega-6 fatty acids during 40 dpp could be a good treatment for early postpartum periods, and a shift to omega-3 fatty acids until 40 d after AI can be considered as a strategy for improving fertility in lactating dairy cows.

[Relationship between residual milk and clinical mastitis in dairy cattle]

Mastitis in cattle is an infection of the mammary gland caused by infection, toxins and/or trauma. Currently, it is assumed that there is a correlation between higher amounts of residual milk and the incidence of clinical mastitis. The amount of residual milk can be examined using different methods. Higher amounts of residual milk may result from an insufficient teat condition and individual detachment settings of milking units. To date, scientific literature has already discussed the relationship between high amounts of residual milk, undermilking and the occurrence of clinical mastitis. The present paper reviews the current status of knowledge regarding residual milk and risk of mastitis.

Microscopy imaging and quantitative phase contrast mapping in turbid microfluidic channels by digital holography

We show that sharp imaging and quantitative phase-contrast microcopy is possible in microfluidics in flowing turbid media by digital holography. In fact, in flowing liquids with suspended colloidal particles, clear vision is hindered and cannot be recovered by any other microscopic imaging technique. On the contrary, using digital holography, clear imaging is possible thanks to the Doppler frequency shift experienced by the photons scattered by the flowing colloidal particles, which do not contribute to the interference process, i.e. the recorded hologram. The method is illustrated and imaging results are demonstrated for pure phase objects, i.e. biological cells in microfluidic channels.

Sources of hepatic glycogen synthesis following a milk-containing breakfast meal in healthy subjects

During feeding, dietary galactose is a potential source of hepatic glycogen synthesis; but its contribution has not been measured to date. In the presence of deuterated water ((2)H(2)O), uridine diphosphate (UDP)-glucose derived from galactose is not enriched, whereas the remainder derived from glucose-6-phosphate (G6P) is enriched in position 2 to the same level as body water, assuming complete G6P-fructose-6-phosphate (F6P) exchange. Hence, the difference between UDP-glucose position 2 and body water enrichments reflects the contribution of galactose to glycogen synthesis relative to all other sources. In study 1, G6P-F6P exchange in 6 healthy subjects was quantified by supplementing a milk-containing breakfast meal with 10 g of [U-(2)H(7)]glucose and quantifying the depletion of position 2 enrichment in urinary menthol glucuronide. In study 2, another 6 subjects ingested (2)H(2)O and acetaminophen followed by an identical breakfast meal with 10 g of [1-(13)C]glucose to resolve direct/indirect pathways and galactose contributions to glycogen synthesis. Metabolite enrichments were determined by (2)H and (13)C nuclear magnetic resonance. In study 1, G6P-F6P exchange approached completion; therefore, the difference between position 2 and body water enrichments in study 2 (0.20% ± 0.03% vs 0.27% ± 0.03%, P < .005) was attributed to galactose glycogenesis. Dietary galactose contributed 19% ± 3% to glycogen synthesis. Of the remainder, 58% ± 5% was derived from the direct pathway and 22% ± 4% via the indirect pathway. The contribution of galactose to hepatic glycogen synthesis was resolved from that of direct and indirect pathways using a combination of (2)H(2)O and [1-(13)C]glucose tracers.

Mastitis and its impact on structure and function in the ruminant mammary gland

It is a given in biology that structure and function go hand-in-hand. At the level of the mammary alveoli, copious milk production depends on the proliferation of mammary epithelial cells and the biochemical and structural differentiation of these cells after parturition. For example, data from quantitative structural studies demonstrate that differences in milk production between beef and dairy cows correspond with a relative failure of alveolar cell differentiation in cattle not specifically selected for milk yield. It is likely, but not proven, that production differences within or between dairy breeds are also determined by differences in the capacity of alveolar cells to differentiate or to maintain an adequate state of differentiation. These observations strongly support the belief that insults from mastitis that lead to losses in mammary function are directly related to disruption of alveolar cell integrity, sloughing of cells, induced apoptosis, and increased appearance of poorly-differentiated cells. Ironically, reduced milk production in cases of subclinical mastitis, is also associated with increases in milk somatic cell count. Thus the elevated neutrophil migration evoked to fight inflammation can inadvertently rendered alveolar epithelial cells non-secretory. A challenge to future researchers will be to devise mastitis treatments and therapies that prevent and/or repair damage to alveolar structure and maximize subsequent secretory cell differentiation.

Ambient temperature shapes reproductive output during pregnancy and lactation in the common vole (Microtus arvalis): a test of the heat dissipation limit theory

The heat dissipation limit theory suggests that heat generated during metabolism limits energy intake and, thus, reproductive output. Experiments in laboratory strains of mice and rats, and also domestic livestock generally support this theory. Selection for many generations in the laboratory and in livestock has increased litter size or productivity in these animals. To test the wider validity of the heat dissipation limit theory, we studied common voles (Microtus arvalis), which have small litter sizes by comparison with mice and rats, and regular addition of wild-caught individuals of this species to our laboratory colony ensures a natural genetic background. A crossover design of ambient temperatures (21 and 30°C) during pregnancy and lactation was used. High ambient temperature during lactation decreased milk production, slowing pup growth. The effect on pup growth was amplified when ambient temperature was also high during pregnancy. Shaving fur off dams at 30°C resulted in faster growth of pups; however, no significant increase in food intake and or milk production was detected. With increasing litter size (natural and enlarged), asymptotic food intake during lactation levelled off in the largest litters at both 21 and 30°C. Interestingly, the effects of lactation temperature on pup growth where also observed at smaller litter sizes. This suggests that vole dams trade-off costs associated with hyperthermia during lactation with the yield from investment in pup growth. Moreover, pup survival was higher at 30°C, despite lower growth, probably owing to thermoregulatory benefits. It remains to be seen how the balance is established between the negative effect of high ambient temperature on maternal milk production and pup growth (and/or future reproduction of the dam) and the positive effect of high temperatures on pup survival. This balance ultimately determines the effect of different ambient temperatures on reproductive success.

Estimates of milk constituents from lactating bonnet macaque (Macaca radiata) mothers between two and seven months post-partum

BACKGROUND

The literature regarding milk composition in non-human primates collected across offspring development is limited. We assayed milk samples from bonnet macaque (Macaca radiata) mothers as part of studies characterizing development of this species.

METHODS

Milk was obtained when possible longitudinally from seven lactating bonnet macaque mothers. Samples were frozen until analysis. Individual samples were analyzed to determine the concentrations of electrolytes including sodium, potassium, calcium, chloride, and magnesium, as well as urea, protein, lipids, glucose, and lactose.

RESULTS

A trend for increased lipids as well as protein percentage was noted with increasing infant age. Chloride and calcium showed an increase with age, whereas other electrolytes remained relatively stable across development.

CONCLUSIONS

The composition of the milk of this particular macaque species was similar to other Old World primates as well as humans. These data add to the limited information available on milk constituents among mammals.

Functional morphology of unguiculiform papillae of the reticular groove in the ruminant stomach

The arrangement of the ruminant stomach in four gastric compartments with specialized mucosal papillae along the gastric groove (GG) has been previously described. However, a debate remains about functional implications of these morphological pecularities. This study was aimed to elucidate the relation between the papillar morphology and its putative functions. The GG was obtained from adult bovine stomachs (n=10) and subdivided into (1) proximal, (2) middle, (3) distal portion of the reticular groove (RG) and (4) the area of the reticulo-omasal sphincter (ROS). The specimens were processed for scanning electron microscopy and stereomicroscopy to analyze the density, shape and location of the papillae. Whereas the proximal portion of the RG was characterized by small (1.5mm), conically shaped, smooth papillae, the middle portion exhibited larger papillae (4mm) with sharp borders covered by keratin. Towards the ROS the papillae further increased in size (3-11mm) and showed compound or single processes resembling the shape of arrows, twisted hooks or thorns (unguiculliform papillae). At the ROS the unguiculliform papillae were distributed in clusters groups and along the border of the sphincter. Due to their peculiar morphological features it is suggested that unguiculliform papillae functions as a filter barrier preventing the passage of large-sized food particles into the omasum and avoiding subsequent obstruction of both the RG and the ROS. The data give further evidence that unguiculliform papillae are actively involved in the complex mechanisms of food processing taking place within the ruminant pluricavity stomach.

Correlates of language impairment in children with galactosaemia

PURPOSE

This study describes risk factors associated with language impairment in children with classic galactosaemia.

METHOD

Thirty-three 4-16-year-old participants with classic galactosaemia and a history of speech sound disorders completed a battery of cognitive and language measures and their parents completed a family history questionnaire.

RESULTS

Nine of the sixteen (56%) participants with typical cognitive development and 15 of the 17 (88%) with borderline-low cognitive development had language impairments. Participants with typical cognitive development more often had an expressive language disorder, whereas those with borderline-low cognitive development more often had a mixed receptive-expressive language disorder. Participants with Q188R/Q188R genotypes had increased risk for both cognitive and language impairments. The IQs of younger siblings who did not consume milk postnatally were 10-56 points higher than the IQs of their older siblings with galactosaemia who had consumed milk postnatally. However, 4 of 5 younger siblings who were lactose-restricted from birth had language impairments. Typically-reported risk factors for language disorder, including parental history of speech/learning problems and low parental education level, were not significantly associated with cognitive or language impairments in the present sample of children with galactosaemia.

CONCLUSIONS

Children with galactosaemia and speech disorders have a 4-6 times greater risk for language impairment than children with early speech disorders of unknown origin. Early dietary lactose may increase the risk for cognitive and language impairments; however, the lack of significant associations of language impairment with days of milk consumption, and other familial and educational risk factors, is consistent with prenatal causation.

Changes in the body and its organs during lactation: nutritional implications

Lactation makes considerably greater demands on the mother's body than pregnancy does in species where the young are helpless at birth and depend on mother's milk for a comparatively long time. These species include many rodents and carnivores and also man. The requirements for the production of milk are met partly from within, by the mobilization of the mother's body tissues, and partly from without, by an increased food intake. Both ways lead to alterations in the composition of the mother's body which may or may not be permanent. Fat laid down in the body during pregnancy is used and there may also be losses of calcium from the skeleton, especially if the calcium intake is low. Whether extra protein is deposited during human pregnancy and lost again during lactation still remains an open question. In rats, the answer depends partly on the intake of protein and energy. The increase in food intake during lactation in some species is so great that the gastrointestinal tract grows considerably to deal with it. In the rat, the small intestine more than doubles its weight. The intestinal wall dilates and the area of mucosa almost doubles. The liver also increases considerably in size owing to an increase in both number and size of cells. After lactation, the liver becomes smaller again, and so does the amount of protein in it, but there is no loss of cells, so that rats that have reared litters have more cellular livers than those that have not. There is no indication whether similar changes occur in women.

Omitting the dry-off period negatively affects colostrum and milk yield in dairy goats

Seventeen pregnant multiparous Murciano-Granadina dairy goats, kept in a semi-intensive exploitation system with once daily milking throughout lactation and 1 kidding per year (milk yield, 577 L/300 d), were used to study the effects of dry-off period length on performance during the subsequent lactation. Goats were mated at wk 29 of lactation and were assigned to 2 experimental groups according to dry-off treatment: goats that were dried off 56 d before expected kidding (D56; n = 9) and goats without dry-off (D0; n = 8). After parturition, kids were removed from their mothers and weighed before suckling. Goats were hand milked to obtain colostrum and were machine milked thereafter. Colostrum was sampled for composition and IgG analysis. Milk yield was recorded weekly during the preceding and subsequent lactations. Udders were biopsied in a sample of goats at d -65 (late lactation), d -49 (during dry-off), and d 48 (early lactation) to kidding (d 0). Apoptotic and proliferating cells in mammary tissues were detected immunohistochemically. Five goats (63%) in the D0 group dried off spontaneously at 27 +/- 4 d before kidding and were considered separately (D27). The rest of the D0 goats yielded 0.86 L/d from d -56 to kidding. Goats kidded 2.25 kids/goat, but the D0 kids had smaller birth weights (1.7 kg) than the D27 (2.2 kg) and D56 (2.1 kg) kids. Colostrum of the D0 goats contained less IgG (5.6 mg/mL) than the D27 (32.9 mg/mL) and the D56 (42.4 mg/mL) goats. In the subsequent lactation (210 d), the D0 goats produced less milk (1.78 L/d) than the D27 (2.51 L/d) and D56 (2.24 L/d) goats, with no detectable difference between the D27 and D56 goats. Apoptosis and proliferation indices increased from 0.51 and 2.09%, at d -65, to 1.75 and 7.12% at d -49 (d 7 of dry-off) in D56 goats. Despite differences in daily milk yield during early lactation (d 48) between the D0, D27, and D56 treatments (1.73, 2.68, and 2.53 L/d, respectively), no differences in apoptosis or proliferation indices were detected (D0: 0.65 and 2.48%; D27: 0.68 and 1.37%; and D56: 0.71 and 2.95%), indicating that duration of the dry period did not affect mammary cell turnover during the subsequent lactation. Omitting the dry period between lactations reduced the quality of colostrum and had negative effects on milk yield in dairy goats. Goats dried off spontaneously for 27 d were as productive as goats dried off for 56 d, indicating that less than 2 mo of dry-off may be sufficient in practice.

Effects of dairy cow diet forage proportion on duodenal nutrient supply and urinary purine derivative excretion

Four mature Holstein-Friesian dairy cows were used in a 4 x 4 Latin square change-over design experiment made up of four 4-wk periods to investigate the relationship between microbial protein flow to the duodenum and excretion of purine derivatives (PD) in the urine. Four dietary treatments based on ad libitum access to ryegrass silage were offered, with a standard dairy concentrate included at different forage:concentrate (F:C) ratios, calculated on a dry matter basis: 80:20, 65:35, 50:50, and 35:65. Feed intakes increased as the proportion of concentrate in the diet increased, despite a concurrent decrease in silage intake. Increased feed intake led to increased nutrient flow to the duodenum. Milk yields increased as the diet F:C ratio decreased, with cows offered the 35:65 diet yielding nearly 8 kg/d more milk than cows offered the 80:20 diet; the concentrations of milk fat decreased and milk protein increased with a decreasing F:C ratio. Purine derivative excretion in the urine increased with an increasing proportion of concentrate in the diet, and there was a strong linear relationship between total PD excretion (allantoin and uric acid) and microbial N flow to the duodenum: microbial N (g/d) = 19.9 + 0.689 x total PD (mmol/d); R = 0.887. This strengthens the case for using PD excretion as a noninvasive marker of microbial protein flow from the rumen in dairy cows.

The CUPDAY Study: prebiotic-probiotic milk product in 1-3-year-old children attending childcare centres

AIM

The aim of the study was to evaluate the efficacy of a milk product containing probiotics and prebiotics (CUPDAY Milk) on the incidence of diarrhoea in children attending daycare centres.

METHODS

The study was undertaken in a randomized controlled trial with 496 children aged 1-3 years attending 29 childcare centres in Perth, Australia. The endpoint for the study was the number of days in which children were recorded as having four or more stools. The diarrhoeal rates were analyzed by Poisson regression using 'intention to treat' (all children) and 'reduced' (children enrolled for more than 10 days) data sets.

RESULTS

There was no difference in demographic characteristics between the case and control groups. In the 'intention to treat' analysis, a total of 41 745 child-days were included in the study. The adjusted risk ratio for those consuming the 'Cupday' milk drink was 0.82 (95% CI 0.73-0.94) for the intention to treat sample (n = 496) and 0.80 (95% CI 0.70-0.91) for the reduced sample (n = 315). The children consuming the 'Cupday' drink had a 20% reduction in the number of days experiencing four or more stools per day.

CONCLUSION

A milk containing probiotics and prebiotics reduced the number of days children attending child care who had four or more stools by 20%.

Suitability of simplified methods for monthly and twice-monthly milk recording, and new prediction factors for the alternate a.m./p.m. method in dairy ewes under a low-input production system

Sicilo-Sarde dairy flock test-day data were analysed (1) to check predicting ability of ten milk recording procedures, based on information from a single monthly or bimonthly milking and (2) to look for the best pair of factors for predicting daily milk yield from either morning or afternoon milkings for the alternate testing method (AT). Prior to analyses, data were adjusted for variation factors with known significant effect. Number of test-day observations was 4755 from 458 lactations of 288 ewes. Losses of precision associated with simplified methods were evaluated by comparing estimated lactation yields with those observed both in a reference plan, where the two daily milkings were recorded at 2-weekly intervals and in the official A4 milk recording (monthly recording of the two daily milkings). Ranking of simplified plans based on their accuracy was still the same under either monthly or twice-monthly frequency. Estimates of lactation yields showed more lack of precision when the usual monthly designs were compared with twice-monthly sampling of both a.m. and p.m. milkings. Losses of precision ranged from 5.1%, for the A4 plan, to 14.6%. Thus, milk production should be estimated from both mikings when their measurement is economically feasible. When only one milking is weighed, designs based on-or beginning with-the a.m. milking were more accurate. There was no evidence of improvement in sampling accuracy by adjustment for milking interval or production level. For practical and economic reasons, the design alternating a.m. and p.m. milkings, without adjustment, is suggested for ovine milk recording. In such a case, new factors for estimating daily production from the measured milking (1.7, 2.3) should be used rather than the factors currently in use (2, 2) because they improved the loss of precision by more than 13% in a monthly recording system.

Milk as an effective post-exercise rehydration drink

The effectiveness of low-fat milk, alone and with an additional 20 mmol/l NaCl, at restoring fluid balance after exercise-induced hypohydration was compared to a sports drink and water. After losing 1.8 (sd 0.1) % of their body mass during intermittent exercise in a warm environment, eleven subjects consumed a drink volume equivalent to 150 % of their sweat loss. Urine samples were collected before and for 5 h after exercise to assess fluid balance. Urine excretion over the recovery period did not change during the milk trials whereas there was a marked increase in output between 1 and 2 h after drinking water and the sports drink. Cumulative urine output was less after the milk drinks were consumed (611 (sd 207) and 550 (sd 141) ml for milk and milk with added sodium, respectively, compared to 1184 (sd 321) and 1205 (sd 142) ml for the water and sports drink; P < 0.001). Subjects remained in net positive fluid balance or euhydrated throughout the recovery period after drinking the milk drinks but returned to net negative fluid balance 1 h after drinking the other drinks. The results of the present study suggest that milk can be an effective post-exercise rehydration drink and can be considered for use after exercise by everyone except those individuals who have lactose intolerance.

Lactation induction as a predictor of post-parturition transgene expression in bovine milk

The bovine's long generation interval results in a delay of several years when evaluating mammary specific transgenes in genetically engineered animals. This experiment was conducted to evaluate the feasibility of reducing that waiting period. Lactation was induced in prepubertal bull and heifer calves as a means of predicting transgene behaviour during subsequent post-parturient lactations in the heifers themselves, and in daughters sired by the bulls. The animals carry a lactation-specific transgene encoding lysostaphin, an antimicrobial protein that kills Staphlococcus aureus, a mastitis-causing pathogen. Oestrogen, progesterone and dexamethasone were administered as previously described (Ball et al. 2000) to nine heifers (five transgenics) ranging in weight from 80 to 145 kg. Eight bull calves (seven transgenics) weighing 81-178 kg received additional oestrogen and progesterone injection prior to dexamethasone treatment. All nine heifers responded to the milk induction scheme yielding between 19 ml and 4.5 l over 5 d. Milk volume from the four responding males (30 microl to 2.5 ml) was significantly less than that harvested from females (P=0.025). Only bull calves >117 kg had a positive response. Lysostaphin was detected in all transgenic prepubertal heifers and in two transgenic prepubertal bull calves induced. A positive relationship was observed between lysostaphin's stapholytic activity in the two types of lactations (r2=0.907, P<0.001) thus providing a useful means of predicting subsequent lysostaphin production in post-partum milk.

Effects of dietary zinc supplement during lactation on longitudinal changes in plasma and milk zinc concentration

Effects of dietary zinc supplement during lactation on maternal zinc plasma and milk zinc concentration through 5 months of lactation were examined. One hundred and thirty eight healthy lactating mothers received a weekly 100 mg elemental zinc supplement (ZS, n = 67) or placebo (PG, n = 71) starting one week postpartum in a double blind, randomized design. Milk and plasma zinc concentrations were determined by atomic absorption spectrophotometer. During the course of study, there was not a significantly difference between ZG and PG groups in dietary zinc and energy intake. The mean plasma zinc concentration at 1st week and 5th month were 134 +/- 49.1 and 115.6 +/- 23 microg dL(-1) (PV = 0.005) for PG group, respectively; that of the ZG group these figures were 124.9 +/- 52.8 and 121 +/- 27.1 microg dL(-1) (PV = 0.38), respectively. The mean serum alkaline phosphatase concentration at 1st week and 5th month were 94.8 +/- 37 and 92.6 +/- 29.9 iu L(-1) for PG group, respectively; that of the ZG group these fissures were 90.5 +/- 36 and 90 +/- 29 iu L(-1) (PV = 0.21), respectively. Milk zinc concentration declined significantly over the course of study for two groups, with the sharpest decline occurring during the first 2 months. The mean monthly zinc concentration of ZG group declined from 310 +/- 138 at 1st week to 118 +/- 64 microg dL(-1) at 5th month (declined by 52%). Corresponding means for PG group were 322 +/- 161 and 109 +/- 70 microg dL(-1) (declined by 60%), respectively. Milk zinc concentration significantly different between two groups at 3 and 4 months. A similar study, however, with different zinc dose and administration manner, in zinc marginal deficient lactating mothers is needed to assess the impact of zinc supplementation on milk zinc concentrations.

Humoral defence improvement and haematopoiesis stimulation in sows and offspring by oral supply of shark-liver oil to mothers during gestation and lactation

Shark-liver oil (SLO) contains two bioactive lipids: alkylglycerols andn-3 PUFA. Alkylglycerols have immunostimulating and haematopoietic properties, whilen-3 PUFA are essential for optimal neonatal development. We investigated the beneficial effects of dietary supplementation with 32g SLO/d to twelve pregnant and then lactating sows (from day 80 of pregnancy to weaning) on the growth and immune status of their offspring, compared with a control group. Sows were vaccinated against Aujeszky's disease 21d before term. Blood samples were collected from sows before treatment, on delivery and 14d later, and from five piglets per litter on days 2, 21 and 36 after birth; colostrum and milk samples were collected 12h, 14 and 28d postpartum. Compared with controls, supplemented sows had higher levels of both erythrocytes and Hb in their blood, and higher concentrations of IgG, alkylglycerols andn-3 PUFA in their mammary secretions. In piglets from supplemented sows, leucocytes and IgG were higher. Supplementation with SLO resulted in an increase in Aujeszky antibodies in both blood and colostrum of sows after vaccination, together with an increase in Aujeszky antibodies in piglet blood. Our findings demonstrate that improvement of both passive and active immune status in piglets is related to the consumption of alkylglycerols associated withn-3 PUFA in the sow diet. The overall improvement in offspring health status by SLO supplementation to the mother could be of interest for optimisation of the lipid diet during and after pregnancy.