Our objectives were to quantify the dimensions of a fully ‘closed’ teat canal in dry cows and to describe recovery of the teat canal between milkings in lactating cows to assess whether and when full closure is attained, since this is an important determinant of udder health. Using an ultrasound scanner, teat canal length and diameter (proximal, midpoint and distal), teat cistern width, teat end width, whole teat width and teat wall thickness in 77 dry and 39 lactating dairy cows were measured. The dry cows represented a cross section of the dry population, with days since dry off ranging from 0 to 69 (median: 27). Data from lactating cows were recorded just before milking, and every 3 h post-milking. To control for location a cross-over (parlour vs. barn) study design was used. In dry cows, teat canal length and diameter did not vary by quarter or days since dry off, but multiparous cows had significantly wider teat canals than primiparous cows. The dry cow measurements can be used as baseline for dimensions for closed teats. In lactating cows, all teat dimensions except teat end width changed significantly during the 12-h milking cycle. Location (parlour vs. barn) did not affect the measurements, except teat end width and teat wall thickness. Teat canal length increased after milking and returned to pre-milking values by 9 h. Proximal and midpoint teat canal diameters decreased slightly just after milking and then progressively increased to above the pre-milking values by 9 h. Distal teat canal diameter increased after milking, partially contracting by 9 h. We found that during the dry period the teat canal is in a steady state, but its diameter is not zero, while during the lactation, the teat canal is in a near constant state of remodelling.

We investigated the antimicrobial components in cow milk at dry off and postpartum and their contribution in preventing new high SCC at quarter level. Milk samples from 72 quarters of 19 lactating cows were collected at last milking before dry off and at 7 d after parturition. Milk yield of each cow was recorded and SCC, IgG, IgA, lactoferrin, lingual antimicrobial peptide (LAP), and S100A7 concentrations in each quarter milk sample were measured. The postpartum milk yield was significantly higher than that at dry off. The IgG, IgA and lactoferrin concentrations in milk at dry off were significantly higher than those at postpartum, whereas the LAP concentration was lower. Quarters with SCC < 300 000 cells/ml at both dry off and postpartum were classified as persistent low SCC (PL) whereas those that rose above that same threshold postpartum were classified as new high SCC (NH). At dry off, IgG and LAP concentrations in milk were significantly higher in PL than in NH. These results suggest that high LAP concentrations during the dry period may contribute toward the prevention of new high SCC.

This study aimed to evaluate the effect of shortening the dry period in high-yielding cows of different body condition scores (BCS). We report colostrum and milk quality, some serum metabolites, BCS changes, and some reproductive parameters with measurements being made over the first two months of lactation. Cows were grouped based on the length of the dry period (normal: about 50 d and short: about 28 d) and BCS (moderate: 2.75 to 3.5 and high ≥ 3.5). Short dry period decreased colostrum volume and, in combination with high BCS only, caused a decrease in milk production. Short dry period moderate BCS cows had the highest serum insulin concentration on day 14 after calving and highest glucose concentration on day 28, but neither differed significantly when measured over the whole period. By contrast, short dry period cows had significantly lower concentrations of non-esterified fatty acids and beta-hydroxybutyrate measured over the whole period. Post-partum loss of BCS was less in short and especially so in the short, moderate BCS group. Following a synchronization protocol at 35 d postpartum. The cows with a short dry period and moderate BCS had lower open days, days to first postpartum estrus and services per conception. It was concluded that short dry periods and moderate BCS had a positive influence on serum metabolites, BCS changes and reproductive parameters.

This research paper focuses on time-lagged heat stress (HS) effects from an across-generation perspective. Temperature × humidity indexes (THI) from the last 8 weeks of pregnancy were associated with subsequent female offspring performances. The offspring dataset considered 172 905 Holstein dairy cows from calving years 2002–2013 from 1,968 herds, located in the German federal state of Hesse. Production traits included milk yield (MKG), protein percentage (PRO%), fat percentage (FAT%), somatic cell score (SCS) and milk urea nitrogen (MUN) from the first official test-day in first lactation. Female fertility traits were the non-return-rate after 56 d (NRR56) in heifers and the interval from calving to first insemination (ICFI) in first parity cows. Longevity traits were the length of productive life (LPL), lifetime productivity in milk yield (LTP-MKG) and milk yield per day of life (MKG-DL). The association analyzes for 10 traits combined with meteorological data from 8 single weeks before calving implied in total 80 different runs. THI ≥50 from all single 8 weeks before calving had unfavorably significant effects on FAT%, ICFI and LPL. Heat stress in terms of THI ≥60 from the last 3 weeks before calving impaired MKG. NRR56 decreased with increasing THI, as observed for all 6 weeks before calving. LTP-MKG and MKG-DL decreased due to high THI in the last 4 weeks before calving. Heat stress (THI ≥60) during late pregnancy had no significantly unfavorable impact on PRO% and MUN. Interestingly, SCS in offspring declined with increasing THI during late pregnancy. In conclusion, for most of the primary and functional traits, unfavorable impact of HS from the dry period on time-lagged performances in offspring was identified, even on longevity. From a practical perspective, our data suggest to provide HS abatement to late gestation dams to avoid long-term adverse effects on the offspring.

In this research communication we used digital gene expression (DGE) analysis to identify differences in gene expression in the mammary glands of dairy cows between early lactation and the mid-dry period. A total of 741 genes were identified as being differentially expressed by DGE analysis. Compared with their expression in dry cows, 214 genes were up-regulated and 527 genes were down-regulated in lactating cow mammary glands. Gene Ontology analysis showed that lactation was supported by increased gene expression related to metabolic processes and nutrient transport and was associated with decreased gene expression related to cell proliferation. Pathway mapping using the Kyoto Encyclopedia of Genes and Genomes showed that 579 differentially expressed genes had pathway annotations related to 204 pathways. Metabolic pathway-related genes were the most significantly enriched. Genes and pathways identified by the present study provide insights into molecular events that occur in the mammary gland between early lactation and mid-dry period, which can be used to facilitate further investigation of the mechanisms underlying lactation and mammary tissue remodeling in dairy cows.

Excessive mobilization of body reserves during the transition from pregnancy to lactation imposes a risk for metabolic diseases on dairy cows. We aimed to establish an experimental model for high v. normal mobilization and herein characterized performance, metabolic and endocrine changes from 7 weeks antepartum (a.p.) to 12 weeks postpartum (p.p.). Fifteen weeks a.p., 38 pregnant multiparous Holstein cows were allocated to two groups that were fed differently to reach either high or normal body condition scores (HBCS: 7.2 NEL MJ/kg dry matter (DM); NBCS: 6.8 NEL MJ/kg DM) at dry-off. Allocation was also based on differences in body condition score (BCS) in the previous and the ongoing lactation that was further promoted by feeding to reach the targeted BCS and back fat thickness (BFT) at dry-off (HBCS: >3.75 and >1.4 cm; NBCS: <3.5 and <1.2 cm). Thereafter, both groups were fed identical diets. Blood samples were drawn weekly from 7 weeks a.p. to 12 weeks p.p. to assess the serum concentrations of metabolites and hormones. The HBCS cows had greater BCS, BFT and BW than the NBCS cows throughout the study and lost more than twice as much BFT during the first 7 weeks p.p. compared with NCBS. Milk yield and composition were not different between groups, except that lactose concentrations were greater in NBSC than in HBCS. Feed intake was also greater in NBCS, and NBCS also reached a positive energy balance earlier than HBCS. The greater reduction in body mass in HBCS was accompanied by greater concentrations of non-esterified fatty acids, and β-hydroxybutyrate in serum after calving than in NBCS, indicating increased lipomobilization and ketogenesis. The mean concentrations of insulin across all time-points were greater in HBCS than in NBCS. In both groups, insulin and IGF-1 concentrations were lower p.p than in a.p. Greater free thyroxine (fT4) concentrations and a lower free 3-3′-5-triiodothyronine (fT3)/fT4 ratio were observed in HBCS than in NBCS a.p., whereas p.p. fT3/fT4 ratio followed a reverse pattern. The variables indicative for oxidative status had characteristic time courses; group differences were limited to greater plasma ferric reducing ability values in NBSC. The results demonstrate that the combination of pre-selection according to BCS and differential feeding before dry-off to promote the difference was successful in obtaining cows that differ in the intensity of mobilizing body reserves. The HBCS cows were metabolically challenged due to intense mobilization of body fat, associated with reduced early lactation dry matter intake and compromised antioxidative capacity.

In this Research Communication we assessed factors affecting colostrum quality of dairy Lacaune ewes using the Brix-refractometer. Colostrum from 536 lambings from one commercial intensive dairy Lacaune farm were analysed for the following factors with potential influence in colostrum quality: (1) ewe parity (n = 84–132), (2) length of previous dry period (PDP) (n = 23–214), (3) age at first lambing (AFL) of primiparous ewes (n = 9–88), (4) lambing season (n = 192 or 344), and (5) year (2011–2013, n = 142–203). Parity significantly affected colostrum quality, with primiparous ewes showing the highest Brix refractometer values (22·6 ± 5·6%, P < 0·0001), though values were similar among multiparous ewes. PDP length also significantly affected colostrum quality: ewes with the shortest PDP showed the worst quality (16·8 ± 4·2%, P < 0·0001), with quality gradually rising with PDP length. Colostrum quality was significantly higher in 2011 (21·0 ± 5·2%) than in 2012 or 2013 (P < 0·0001); this likely reflects the several-fold greater proportion of animals with long PDP in 2011. In contrast, neither AFL nor lambing season significantly affected colostrum quality. These results suggest that parity and PDP length can substantially affect ovine colostrum quality of dairy ewes under intensive management conditions and they further show the usefulness of the Brix refractometer for providing a rough estimation of colostrum quality on-farm. However, further studies are needed to determine a validated cut-off Brix value for identifying good-quality colostra in ovine species.

We reconstructed Holocene water-level and vegetation dynamics based on pollen and plant macrofossils from a coastal lake in Upper Michigan. Our primary objective was to test the hypothesis that major fluctuations in Great Lakes water levels resulted in part from climatic changes. We also used our data to provide temporal constraints to the mid-Holocene dry period in Upper Michigan. From 9600 to 8600 cal yr B.P. a shallow, lacustrine environment characterized the Mud Lake basin. A Sphagnum-dominated wetland occupied the basin during the mid-Holocene dry period (∼8600 to 6600 cal yr B.P.). The basin flooded at 6600 cal yr B.P. as a result of rising water levels associated with the onset of the Nipissing I phase of ancestral Lake Superior. This flooding event occurred contemporaneously with a well-documented regional expansion of Tsuga. Betula pollen increased during the Nipissing II phase (4500 cal yr B.P.). Macrofossil evidence from Mud Lake suggests that Betula alleghaniensis expansion was primarily responsible for the rising Betula pollen percentages. Major regional and local vegetational changes were associated with all the major Holocene highstands of the western Great Lakes (Nipissing I, Nipissing II, and Algoma). Traditional interpretations of Great Lakes water-level history should be revised to include a major role of climate.

The purpose of the study reported in this Research Communication was to evaluate alterations in concentration of total antioxidant capacity (TAC) of plasma, plasma total thiols as markers of oxidative protein damage and malondialdehyde (as a final product of lipid peroxidation) in samples obtained at different stages of the lactation cycle and dry period of dairy cows. We found that TAC was significantly lower in the primiparous cows compared to multiparous cows. This study clearly demonstrates a need for monitoring primiparous cows during the production cycle, especially when they are faced with severe metabolic conditions. Furthermore, TAC may be a sensitive, reliable and useful indicator for measurement of cumulative effects of antioxidants as an addition to metabolic profile tests, which are currently used to analyse dairy cattle health.

Healthy calves are fundamental to any profitable dairy enterprise. Research to-date, has focused on year-round calving systems which experience many different challenges compared to spring-calving systems. The objective of the present study was to determine the on-farm dry cow, calving, and colostrum management practices of spring-calving dairy production systems, and quantify their associations with herd size and herd expansion status (i.e. expanding or not expanding). Information on these management practices was available from a survey of 262 Irish spring-calving dairy farmers, representative of the Irish national population. Herd expansion in the 2 years before, and the year that the survey was conducted was not associated with any of the management practices investigated. Fifty-three percent of respondents had an average calving season length of 10 to14 weeks with 35% of herds having a longer calving season. Previous research in cattle has documented that both colostrum source and feeding management are associated with the transmission of infectious disease from cow to calf. In the present study 60% of respondents fed calves colostrum from their own dam; however, 66% of those respondents allowed the calf to suckle the dam, 23% of survey respondents fed calves pooled colostrum. Larger herds were more likely (P<0.01) to use pooled colostrum supplies, while smaller herds were more likely (P<0.05) to allow the calf to suckle the dam. The majority (86%) of respondents had stored supplies of colostrum; average-sized herds had the greatest likelihood of storing colostrum (P<0.05), compared to other herd sizes; larger sized herds had a lesser likelihood (P<0.05) of storing colostrum in a freezer, compared to other herd sizes. Although freezing colostrum was the most common method used to store colostrum (54% of respondents), 17% of respondents stored colostrum at room temperature, 29% of which stored it at room temperature for greater than 4 days. The results from the present study indicate that a particular focus needs to be placed on calving and colostrum management because this study has highlighted a number of areas which are below international standards, and may have repercussions for calf health. Furthermore, management practices on larger farms could be improved and, as these represent the future of dairy farming, a focus needs to be placed on them. Expanding herds are not a particular concern as herd expansion, independent of herd size, does not seem to be associated with calving and colostrum management practices on Irish spring-calving dairy herds.

Recently it has been demonstrated that there are differences between sheep and goats in respect to adaptation to a calcium-restricted diet. It was the aim of the present study to evaluate whether species-specific peculiarities also occur when calcium homoeostasis is challenged by lactation. Therefore, we investigated the time courses of plasma parameters related to calcium homoeostasis (calcium, phosphate, calcitriol, the bone resorption marker CrossLaps® and the bone formation marker osteocalcin) during the transition period in multiparous animals of both species and compared the results to data from a former study carried out with dairy cows. As in cows, plasma calcium and the ratio of bone formation to bone resorption decreased at parturition in goats while plasma calcitriol increased. On day 10 post partum the bone parameters of goats reached prepartum values again, which was not the case in cows. Sheep were found to experience a challenge of calcium homoeostasis already 10 d before parturition, reflected by a very low ratio of bone formation to bone resorption, which was not accompanied by an increase in plasma calcitriol. Additionally, sheep and goats which had been in milk for 3 months were sampled, dried-off and sampled again 6 weeks later. In dried-off animals there were no detectable differences in parameters of bone metabolism. In conclusion we could show that the contribution of bone mobilisation to the compensation for the enhanced calcium demand due to lactation differs between the three ruminant species.

The internal teat sealant OrbeSeal® (Zoetis, Berlin, Germany) is intended to prevent new intramammary infection (IMI) throughout the dry period. The aim of this field study was to determine new infection rates in udder quarters applied exclusively with the sealant at dry-off and untreated ones (control group). For that, the new infection rate of udder quarters treated with the sealant was evaluated in a split-udder design (front right and rear left udder quarters treated, the other ones untreated) in 128 cows from nine dairy farms in North Germany that were healthy in all four udder quarters (i.e. <100 000 cells/ml, bacteriologically negative). After calving, duplicate quarter milk samples were collected twice at DIM (days in milk) 5–12 and 7 d later for culture. The new infection rates for treated and untreated groups were 3·4 and 10·5%, respectively. The results showed that applying a standardised study design with very few confounders under field conditions, using internal teat sealants reduced the new infection rate on quarter level to a third of that of the control group. Thus, internal teat sealants represent a viable option for dry-off treatment of udder-healthy cows.

A study was conducted to evaluate the effects of pre partum (PRE) and post partum (POST) dietary energy and nutrient supply (E) and their interactions on feed intake, performance and energy status in dairy cows of three breeds. In this experiment, the effects of three energy and nutrient supply levels (low (L), medium (M), high (H)), both pre-calving and post-calving, were investigated, using a 3×3 factorial arrangement of treatments. In both phases (84 days pre- and 105 days post-calving) E levels applied to a total of 81 multiparous cows of breeds Simmental (SI), Brown Swiss (BS) and Holstein–Friesian (HF; n=27 for each breed), were 75%, 100% and 125% of recommendations of the German Society of Nutrition Physiology (GfE). Dry matter intake (DMI) was restricted, if energy intake exceeded target values. Pre partum DMI and energy intake were different as designed, liveweight and body condition score (BCS) of SI cows were higher, but EB was lower, compared to BS and HF cows. Milk yield and composition were influenced by all three main experimental factors (EPRE, EPOST, breed). Energy-corrected milk yield was 25.6, 28.6 and 30.1 kg/day for LPRE, MPRE and HPRE as well as 21.5, 30.1 and 32.6 kg/day for LPOST, MPOST and HPOST, respectively. Numerically, only for milk protein content the interactions EPRE×EPOST and EPRE×breed reached significance. Impact of energy supply pre-calving was more pronounced when cows had lower energy supply post-calving and vice versa. On the other hand, milk yield response of cows to energy supply above requirements was greater for cows that were fed on a low energy level pre partum. Impact of energy level pre partum was higher for HF cows, showing that their milk production relies to a greater extent on mobilization of body reserves. Increasing energy supply pre partum led to a more negative energy balance post partum, mainly by increasing milk yield and content, whereas feed intake was slightly reduced. Increasing energy supply post partum enhanced milk yield as well as milk protein and lactose content. Calculated energy balance corresponded well with liveweight and BCS change. Response of milk yield to increasing energy supply followed the principle of diminishing returns, since energy was increasingly partitioned to body retention. Increasing energy supply pre partum enhances milk yield and content post partum, but exacerbates negative energy balance and its consequences.

The dry period is required to facilitate cell turnover in the bovine mammary gland in order to optimize milk yield in the next lactation. Traditionally, an 8-week dry period has been a standard management practice for dairy cows based on retrospective analyses of milk yields following various dry period lengths. However, as milk production per cow has increased, transitioning cows from the nonlactating state to peak milk yield has grown more problematic. This has prompted new studies on dry period requirements for dairy cows. These studies indicate a clear parity effect on dry period requirement. First parity animals require a 60-day dry period, whereas lactations following later parities demonstrate no negative impact with 30-day dry period or even eliminating the dry period when somatotropin (ST) is also used to maintain milk yields. Shortened dry periods in first parity animals were associated with reduced mammary cell turnover during the dry period and early lactation and increased numbers of senescent cells and reduced functionality of lactating alveolar mammary cells postpartum. Use of ST and increased milking frequency postpartum reduced the impact of shortened dry periods. The majority of new intramammary infections occur during the dry period and persist into the following lactation. There is therefore the possibility of altering mastitis incidence by modifying or eliminating the dry period in older parity animals. As the composition of mammary secretions including immunoglobulins may be reduced when the dry period is reduced or eliminated, there is the possibility that the immune status of cows during the peripartum period is influenced by the length of the dry period.

This experiment evaluated different strategies for allocating first-cut grass silages to dry dairy cows that had low body-condition score (BCS) at drying off. A total of 48 moderately yielding Holstein-Friesian cows were used, receiving one of three dietary treatments in the dry period and a single lactation diet based on a flat-rate of concentrates and grass silage ad libitum. Throughout the dry period, one group received a low-digestibility silage (harvested 15 June 1998; LL; metabolisable energy (ME) = 10.3 MJ/kg dry matter (DM)) and a second group received a high-digestibility silage (harvested 9 May 1998, HH; ME = 11.7 MJ/kg DM). A third strategy (LH) offered the low-digestibility silage in the early dry period and the high-digestibility silage in the final 3 weeks before calving. The silages had very different crude protein concentrations (144 and 201 g/kg DM) and intakes were widely divergent (10.1 v. 13.5 kg DM/day) across the dry period. No concentrates were fed during the dry period. Silage quality had a very large effect on liveweight change, with treatment means of 0.32 and 1.75 kg/day for LL and HH, respectively. BCS changes followed a similar pattern, though no cows became over-conditioned and blood metabolites were within normal ranges. Increased silage digestibility in the late dry period led to a substantial increase in milk fat concentration and a smaller increase in milk protein concentration, the latter confined to the first full week of lactation. Depression of milk fat appears related to low blood glucose when dry cows in low body condition are fed at a low level. The LH strategy avoided the tendency for lower milk yields and fat concentration that resulted from feeding the low-digestibility silage until calving. This strategy also avoided the higher calf weights that resulted from feeding the high-digestibility silage in the early dry period.

ATP-binding cassette (ABC) transporters play a pivotal role in human physiology, and mutations in these genes often result in severe hereditary diseases. ABC transporters are expressed in the bovine mammary gland but their physiological role in this organ remains elusive. Based on findings in the context of human disorders we speculated that candidate ABC transporters are implicated in lipid and cholesterol transport in the mammary gland. Therefore we investigated the expression pattern of selected genes that are associated with sterol transport in lactating and nonlactating mammary glands of dairy cows. mRNA levels from mammary gland biopsies taken during lactation and in the first and second week of the dry period were analysed using quantitative PCR. Five ABC transporter genes, namely ABCA1, ABCA7, ABCG1, ABCG2 and ABCG5, their regulating genes LXRα, PPARγ, SREBP1 and the milk proteins lactoferrin and α-lactalbumin were assessed. A significantly enhanced expression in the dry period was observed for ABCA1 while a significant decrease of expression in this period was detected for ABCA7, ABCG2, SREBP1 and α-lactalbumin. ABCG1, ABCG5, LXRα, PPARγ and lactoferrin expression was not altered between lactation and dry period. These results indicate that candidate ABC transporters involved in lipid and cholesterol transport show differential mRNA expression between lactation and the dry period. This may be due to physiological changes in the mammary gland such as immigration of macrophages or the accumulation of fat due to the loss of liquid in the involuting mammary gland. The current mRNA expression analysis of transporters in the mammary gland is the prerequisite for elucidating novel molecular mechanisms underlying cholesterol and lipid transfer into milk.

This study aimed at investigating risk factors for new intramammary infections (IMI) during the dry period in untreated cows from herds using selective dry cow antibiotic therapy (DCT). A total of 980 uninfected quarters in 347 untreated cows from 28 herds using selective DCT were included in a prospective survey. A herd-level questionnaire and an individual cow-level recording sheet were implemented to collect data on putative risk factors. Quarter milk samples were taken at drying-off and on day 3 after calving to assess the occurrence of new IMI during the dry period. A multivariate model including a herd effect as random and a cow effect as repeated was run at the quarter level. Interactions between risk factors and the cow infection status at drying-off (cow infected in at least one quarter v. uninfected) were checked. Three risk factors were found significantly associated with the risk for new IMI without interaction (P < 0.05): cows infected in at least one quarter at drying-off (v. uninfected cows) (relative risks (RR) = 1.58); long preceding lactation (>355 days v. shorter length) (RR = 1.62); long dry period (>65 days v. shorter length) (RR = 1.46). One risk factor acted only in interaction with the cow infection status at drying-off: in cows uninfected at drying-off, the risk for new IMI was significantly higher in cows with short teats (RR = 1.21) when compared with cows with long or normal teats, while the reverse relationship was observed in cows infected at drying-off. Risk factors can be translated in recommendations, for instance to have dry periods not longer than 2 months. Moreover, as suggested by our results, the efficacy of selective DCT towards the prevention of new IMI would be improved if all infected cows were detected and treated. Criteria to accurately identify these infected cows should be therefore further investigated.

The aim was to investigate the interdependence of udder quarters within cow towards the incidence of intramammary infections during the dry period in herds under selective dry-cow antibiotic therapy. A total of 368 cows among 28 herds were included in a survey. Quarter milk samples collected at the last milking before drying-off and on day 3 after calving were submitted to microbiological procedures. An expected distribution of cows according to their number of newly infected quarters was calculated based on a binomial probability distribution from the overall quarter incidence (or from the quarter incidence in each herd) and compared with the observed distribution. Incidence of newly infected quarters ranged from 0·0 to 39·3%, depending on the herd (median: 17·7%). Interdependence of quarters towards new infection during the dry period was observed whatever the pathogen type, for both treated and untreated cows. Calculation of an expected distribution of cows according to their number of newly infected quarters using the quarter incidence in each herd (instead of the overall quarter incidence) reduced the distance to the observed distribution, but interdependence was still observed. Our results support the application of selective antibiotic therapy at the cow level rather than at the quarter level.

Effects of feeding a protein supplement to dairy cows during the dry period on performance during the following lactation were investigated in two experiments. Holstein-Friesian cows were paired towards the end of lactation, and, after drying off, one of each pair received a typical dry cow management regime of ad libitum grass silage (experiment 1), or a mix of grass silage and distillers' grains or pressed beet pulp (experiment 2). The other cows were offered restricted access to the same basal diet, together with ad libitum access to barley straw and 0·5 kg/day high protein maize gluten meal. During the following lactation, animals from both groups were treated without reference to dry period treatment, and were offered equal access to the same lactation diet. Data were analysed by analysis of variance of experiment means and by parallel curve analysis using sample means. In experiment 1, milk yields were similar (27·2 v. 27·9 (s.e.d. 2·12) kg/day for control and supplemented animals respectively) but milk protein yields, and hence concentrations, were significantly higher (P < 0·001) from supplemented animals (28·9 v. 31·8 (s.e.d. 0·58) g/kg). In experiment 2, milk yields were significantly higher (P < 0·001) from supplemented animals (mean 33·3 v. 35·4 (s.e.d. 1·66) kg/day; however, milk protein yields were also significantly increased (P < 0·001) and the change in milk protein concentration was small. No difference in dry-matter intake was recorded in a subset of animals during early lactation in experiment 2. It is hypothesized that the maternal labile body protein pool was maintained or replenished during the dry period by the provision of the protein supplement, and that this had a significant effect on subsequent lactation performance.