Thyroid hormones, blood plasma metabolites and haematological parameters in relationship to milk yield in dairy cows

Interaction of blood calcium with milk yield, energy metabolites, subclinical mastitis, and reproductive performance in crossbred dairy cows

Limited literature is available on the consequences of postpartum low blood calcium (Ca) concentration in crossbred cows. The research aimed to investigate the correlation between postpartum serum Ca levels and various parameters, including milk yield, serum energy metabolites, milk somatic cell count, and reproductive factors in crossbred cows. Following parturition, a total of 45 potential high-yielding F2 (HF × Sahiwal; Genotype: 75:25) dairy cows were enrolled . These cows were categorized based on plasma calcium concentrations into three groups: a low calcium group (Ca-L) with a calcium concentration of <5 mg/dL, a medium calcium group (Ca-M) with a calcium concentration ranging from 5 to 8.5 mg/dL, and a high calcium group (Ca-H) with a calcium concentration exceeding 8.5 mg/dL. The study parameters were measured over an 8-week period. The results indicated that overall milk yield and blood glucose were significantly higher in the Ca-H group compared to Ca-M and Ca-L (p < .01). Blood cholesterol was significantly higher in Ca-M (p < .01), while blood triglyceride was significantly lower in both Ca-M and Ca-H. Overall, blood cortisol did not show a significant change between these groups (p < .01); however, progesterone levels were higher (p < .01) in Ca-M and Ca-H cows. Furthermore, somatic cell count (SCC) significantly (p < .01) decreased in cows with Ca-H compared to Ca-L. Additionally, postpartum oestrous interval and interestrus interval decreased significantly (p < .01) in Ca-M and Ca-H compared to Ca-L. These findings suggest that cows with blood calcium levels exceeding 8.5 mg/dL exhibited significantly higher milk yield, blood metabolite levels, a lower likelihood of subclinical mastitis, and earlier reproductive activity after calving.

Effects of temperature-humidity index on blood metabolites of German dairy cows and their female calves

Heat stress (HS) impairs productivity, health, and welfare in dairy cows, and additionally causes metabolic changes. Hence, specific metabolites could be used as HS biomarkers. Consequently, the aim of the present study was to compare blood metabolite concentrations of German Holstein dairy cows and of their female calves suffering from high temperature-humidity index (THI) during late gestation (cows) or during their first week of life (calves) or not. According to the mean daily THI (mTHI) at the day before blood sampling, animals were classified into 2 groups: high mTHI ≥60 (hmTHI) and low mTHI <60 (lmTHI). To perform a standard cross-sectional 2-group study, cow groups (n = 48) and calf groups (n = 47) were compared separately. Differences in metabolite concentrations between hmTHI and lmTHI animals were inferred based on a targeted metabolomics approach. In the first step, processed metabolomics data were evaluated by multivariate data analysis techniques, and were visualized using the web-based platform MetaboAnalyst V5.0. The most important metabolites with pronounced differences between groups were further analyzed in a second step using linear mixed models. We identified 9 thermally sensitive metabolites for the cows [dodecanedioic acid; 3-indolepropionic acid; sarcosine; triglycerides (14:0_34:0), (16:0_38:7), (18:0_32:1), and (18:0_36:2); phosphatidylcholine aa C38:1; and lysophosphatidylcholine a C20:3] and for the calves [phosphatidylcholines aa C38:1, ae C38:3, ae C36:0, and ae C36:2; cholesteryl esters (17:1) and (20:3); sphingomyelins C18:0 and C18:1; and p-cresol sulfate], most of them related to lipid metabolism. Apart from 2 metabolites (3-indolepropionic acid and sarcosine) in cows, the metabolite plasma concentrations were lower in hmTHI than in lmTHI groups. In our heat-stressed dry cows, results indicate an altered lipid metabolism compared with lactating heat-stressed cows, due to the missing antilipolytic effect of HS. The results also indicate alterations in lipid metabolism of calves due to high mTHI in the first week of life. From a cross-generation perspective, high mTHI directly before calving seems to reduce colostrum quality, with detrimental effects on metabolite concentrations in offspring.

The physiological dissimilarities of Holstein dairy cows with different milk yields

BACKGROUND

Even if breed, parity, dietary and environmental management are same, dairy cows still have notable differences in milk yield that may be underpinned by physiologic differences.

OBJECTIVES

This study aimed to investigate the physiological dissimilarities of dairy cows with different milk yields.

METHODS

Thirty cows were sorted into high milk-yielding cows (group H: 58.93±2.31 kg/day), moderate milk-yielding cows (group M: 44.99±0.54 kg/day), and low milk-yielding cows (group L: 24.99±6.83 kg/day) according to milk yield. Blood was collected and serum parameters were assessed. Rumen fluid was collected for the evaluation of rumen fermentation parameters (RFPs) and bacterial community composition (BCC).

RESULTS

Serum prolactin, growth hormone, glutathione peroxidase, immunoglobulin A and non-esterified fatty acid had a significantly positive correlation with milk yield (p < 0.05), whereas serum glucagon and total antioxidant capacity had a significantly negative correlation with milk yield (p < 0.05). The concentration of valeric acid and the ratio of acetic acid to propionic acid in the rumen fluid in group H was significantly lower than that in group L (p < 0.05). The concentration of acetic acid and butyric acid in group H was significantly lower than that in groups M and L (p < 0.05). The relative abundances of Ruminococcaceae_NK4A214_group, Prevotella_1, Rikenellaceae_RC9_gut_group, Christensenellaceae_R-7_group, Muribaculaceae, and Ruminococcus_2 were negatively correlated with milk yield, whereas the relative abundance of Succinivibrionaceae_UCG-001, Lachnospiraceae_NK3A20_group, Shuttleworthia and Dialister were positively correlated with milk yield (p < 0.05).

CONCLUSIONS

This study indicates that dairy cows with different milk yields have clear divergence in serum indicators, RFPs, BCC and rumen microbial metabolism.

Physiological Indicators and Production Performance of Dairy Cows With Tongue Rolling Stereotyped Behavior

Non-nutritive oral behaviors, especially tongue rolling, are prevalent in the stabled cow population. These behaviors mean that the environment or management process might not suit the cows, suggesting low welfare. However, few researches have reported the physiological indicators or production performance of dairy cows with the stereotyped behavior. This study aimed to determine physical conditions, daily activity, rumen fermentation, and milk production of cows with tongue-rolling behavior. Three hundred and fifty nine Holstein cows in the same barn and lactation stage were subjected to scan sampling behavior observations 126 times for 7 days. Ten cows with high-frequency tongue-rolling behavior (TON) and 10 cows without abnormal oral behavior (CON) were selected for further study. Serum sample, ruminal fluid, milk sample, and behavior record video of TON and CON cows were collected. TON cows had more drinking behavior and more stable lying behavior than the CON cows during the daytime. The body condition score of the TON cows decreased, while the milk yield, yield of milk fat, protein, and lactose in the study period increased. The TON cows had lower ruminal fluid pH, acetate/propionate ratio, and total volatile acid. The bacterial diversity in the ruminal fluid was not different between the two groups. Compared to CON cows, the TON cows had a higher level of serum stress indicators, such as cortisol, thyroid hormone, and norepinephrine, which positively correlated to the frequency of tongue-rolling behavior. Meanwhile, the TON cows had a higher level of lactate dehydrogenase, serum glucose, total triglyceride, total cholesterol, and Interleukin 6. Overall, it means they suffer from higher levels of stress and have higher energy metabolism for a long time when cows show tongue-rolling behavior. TON cows had suffered a higher stress level and had higher energy metabolic status for a long time. The TON cows might have better heat tolerance to the thermal environment by more lying and drinking time. Our data revealed the changes in milk production, physiological stress indicators of dairy cows with high-frequency tongue rolling behavior, which will provide essential knowledge for the in-depth understanding of tongue rolling behavior in dairy cows.

Effects of parity order on performance, metabolic, and hormonal parameters of grazing beef cows during pre-calving and lactation periods

Background

Metabolic profile evaluation is a tool widely used in ruminant nutrition as metabolic cues that relate nutrition to physiology. Metabolic and hormonal traits change during pre-partum and lactation according to parity in dairy cows, but studies of beef cows under grazing are scarce. The present study aimed to evaluate how metabolic and hormonal traits change over time, their relationship to performance, and determine if these factors differ according to the parity order of grazing beef cows. Thirty-six pregnant Nellore cows (12 nulliparous, 12 primiparous, and 12 multiparous) were used. The study started at 60 d prepartum until 203 d of lactation.

Results

The initial body weight (BW) and final BW were higher for multiparous cows (P > 0.05). An interaction occurred between parity and day (P < .0001) for body condition score. Nulliparous and primiparous body condition score were reduced from − 60 prepartum to 30 postpartum, then stabilized 60 postpartum (P < 0.05), while multiparous maintained body condition score from − 60 days until 60 days postpartum (P > 0.05). Calf BW, final BW, and average daily gain did not differ between parities (P > 0.05). Effect of day (P < 0.05) was detected for non-esterified fatty acids, triglycerides, total cholesterol, LDL, VLDL, progesterone, and insulin. An interaction was observed between parity and days for glucose, HDL, β-hydroxybutyrate, creatinine and IGF-1 (P < 0.05). Parity affected serum urea nitrogen, total proteins, albumin, and globulins (P < 0.05). Parity and day relative to calving did not impact total T3 and T4 (P > 0.05).

Conclusions

Hormonal and metabolic profile is strongly influenced by the stage of lactation. Time effects (pre-partum and lactation period) were more pronounced in nulliparous since they displayed more unbalanced metabolic and hormonal traits and lowered BCS pre- and postpartum.

Genome-wide association study and functional analyses for clinical and subclinical ketosis in Holstein cattle

Ketosis is one of the most frequent metabolic diseases in high-yielding dairy cows and is characterized by high concentrations of ketone bodies in blood, urine, and milk, causing high economic losses. The search for polymorphic genes, whose alleles have different effects on resistance to developing the disease, is of extreme importance to help select less susceptible animals. The aims of this study were to identify genomic regions associated with clinical and subclinical ketosis (β-hydroxybutyrate concentration) in North American Holstein dairy cattle and to investigate these regions to identify candidate genes and metabolic pathways associated with these traits. To achieve this, a GWAS was performed for 4 traits: clinical ketosis lactation 1, clinical ketosis lactation 2 to 5, subclinical ketosis lactation 1, and subclinical ketosis lactation 2 to 5. The estimated breeding values from 77,277 cows and 7,704 bulls were deregressed and used as pseudophenotypes in the GWAS. The top-20 genomic regions explaining the largest proportion of the genetic variance were investigated for putative genes associated with the traits through functional analyses. Regions of interest were identified on chromosomes 2, 5, and 6 for clinical ketosis lactation 1; 3, 6, and 7 for clinical ketosis lactation 2 to 5; 1, 2, and 12 for subclinical ketosis lactation 1; and 20, 11, and 25 for subclinical ketosis lactation 2 to 5. The highlighted genes potentially related to clinical and subclinical ketosis included ACAT2 and IGF1. Enrichment analysis of the list of candidate genes for clinical and subclinical ketosis showed molecular functions and biological processes involved in fatty acid metabolism, lipid metabolism, and inflammatory response in dairy cattle. Several genomic regions and SNPs related to susceptibility to ketosis in dairy cattle that were previously described in other studies were confirmed. The novel genomic regions identified in this study aid to characterize the most important genes and pathways that explain the susceptibility to clinical and subclinical ketosis in dairy cattle.

The Capacity of Holstein-Friesian and Simmental Cows to Correct a Negative Energy Balance in Relation to Their Performance Parameters, Course of Lactation, and Selected Milk Components

A significant factor in improving the performance of dairy cows is their physiological ability to correct a negative energy balance (NEB). This study, using Simmental (SIM) and Holstein-Friesian (HF) cows, aimed to assess changes in NEB (non-esterified fatty acid; body condition score; and C16:0, C18:0, and C18:1) and its effect on the metabolic efficiency of the liver (β-hydroxybutyrate and urea). The effects of NEB on daily yield, production at peak lactation and its duration, and changes in selected milk components were assessed during complete lactation. Up to peak lactation, the loss of the body condition score was similar in both breeds. Subsequently, SIM cows more efficiently restored their BCS. HF cows reached peak lactation faster and with a higher milk yield, but they were less able to correct NEB. During lactation, their non-esterified fatty acid, β-hydroxybutyrate, C16:0, C18:0, C18:1, and urea levels were persistently higher, which may indicate less efficient liver function during NEB. The dynamics of NEB were linked to levels of leptin, which has anorectic effects. Its content was usually higher in HF cows and during intensive lactogenesis. An effective response to NEB may be exploited to improve the production and nutritional properties of milk. In the long term, it may extend dairy cows' productive life and increase lifetime yield.

The deleterious effect of postpartum pyometra on the reproductive indices, the metabolic profile, and oxidant/antioxidant parameters of dairy cows

Background and Aim:

Postpartum uterine infectious diseases, such as pyometra, have discrepancy with both health and, subsequently, productivity of dairy cows due to its high prevalence and the high cost of treatment. Therefore, this study investigates the influence of pyometra on the reproductive indices, the metabolic profile, and oxidant/antioxidant parameters of the pyometric animal compared to those of healthy ones.

Materials and Methods:

The study included 30 cows. The animals were differentiated into two groups of 15 cows each: A group of pyometra and a control group. All pyometric cows were subjected to breeding soundness examination after the end of pyometra and were compared to the control group. Blood samples were obtained to assess the levels of glucose, non-esterified fatty acids (NEFA), triglycerides (TGs), cholesterol, albumin, total protein, alanine aminotransferase, aspartate aminotransferase (AST), alkaline phosphatase (ALP), blood urea nitrogen (BUN), creatinine, calcium (Ca), phosphorus, sodium, potassium, progesterone hormone (P4), malondialdehyde (MDA), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and superoxide dismutase.

Results:

Results revealed significant prolonged duration of first estrus, the days open, and the required number of services due to pyometra. The pyometra group yielded increased levels of NEFA, TGs, ALP, BUN, creatinine, MDA, and progesterone hormone. In addition, significant decrease in the levels of glucose, cholesterol, albumin, Ca, phosphorus, sodium, TAC, GPx, and superoxide dismutase was observed in the pyometra group. Finally, no difference in the concentrations of total protein, ALT, AST, and potassium was observed in the pyometra group.

Conclusion:

The reproductive indices was adversely influenced in cows with postpartum pyometra, and metabolic profile, involving energy balance signals and liver function indicators, revealed differences between the two groups. Increased levels of oxidative stress parameters and decrease levels of antioxidant levels were also found, suggesting that pyometra is an incentive for oxidative stress. Overall, checking the energy balance, metabolic imbalances, and oxidant/antioxidant profile, accompanied with pre-emptive procedures during the postpartum period, is essential and can reduce the chances of such diseases and possible noxious results in highly productive cows.

Energy Balance Indicators during the Transition Period and Early Lactation of Purebred Holstein and Simmental Cows and Their Crosses

Simple Summary

Dairy cows undergo a very challenging time between the weeks immediately before calving and the start of lactation after calving. In particular, high yielding dairy cows, such as purebred Holstein cows, have to cope with a severe negative energy balance. In comparison to the feed (energy) intake, they produce a great surplus of milk energy. The energy deficit is supposed to be smaller in dual-purpose breeds, such as (German) Simmental. Therefore, crossbreeding of both breeds, with the aim of using the advantageous characteristics of both breeds, and the expected advantage of crossbred cows, might reduce the negative effects of the metabolic and physiologic challenges by improving the production efficiency of dairy herds. After calving, Simmental cows and cows with greater Simmental proportions decreased less in the body condition score, had lower concentrations of ketone bodies, and nonesterified fatty acids in the blood, which are common indicators of metabolic disorders during the transition period. In particular, first generation (F1) crossbred cows produced more energy corrected milk (ECM) than purebred Holstein cows, while the other crossbred generations still showed positive heterosis effects for ECM. That means, they produced more ECM than the average of both parental breeds.

Abstract

Crossbreeding in dairy cattle has been used to improve functional traits, milk composition, and efficiency of Holstein herds. The objective of the study was to compare indicators of the metabolic energy balance, nonesterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), glucose, body condition score (BCS) back fat thickness (BFT), as well as milk yield and milk composition of Holstein and Simmental cows, and their crosses from the prepartum period until the 100th day of lactation at the Livestock Center of the Ludwig Maximilians University (Munich, Germany). In total, 164 cows formed five genetic groups according to their theoretic proportion of Holstein and Simmental genes as follows: Holstein (100% Holstein; n = 9), R1-Hol (51–99% Holstein; n = 30), first generation (F1) crossbreds (50% Holstein, 50% Simmental; n = 17), R1-Sim (1–49% Holstein; n = 81) and Simmental (100% Simmental; n = 27). The study took place between April 2018 and August 2019. BCS, BFT blood parameters, such as BHBA, glucose, and NEFA were recorded weekly. A mixed model analysis with fixed effects breed, week (relative to calving), the interaction of breed and week, parity, calving year, calving season, milking season, and the repeated measure effect of cow was used. BCS increased with the Simmental proportion. All genetic groups lost BCS and BFT after calving. Simmental cows showed lower NEFA values. BHBA and glucose did not differ among genetic groups, but they differed depending on the week relative to calving. Simmental and R1-Sim cows showed a smaller effect than the other genetic groups regarding changes in body weight, BCS, or back fat thickness after a period of a negative energy balance after calving. There was no significant difference for milk yield among genetic groups, although Simmental cows showed a lower milk yield after the third week after calving. Generally, Simmental and R1-Simmental cows seemed to deal better with a negative energy balance after calving than purebred Holstein and the other crossbred lines. Based on a positive heterosis effect of 10.06% for energy corrected milk (ECM), the F1, however, was the most efficient crossbred line.

Gene Networks Driving Genetic Variation in Milk and Cheese-Making Traits of Spanish Assaf Sheep

Most of the milk produced by sheep is used for the production of high-quality cheese. Consequently, traits related to milk coagulation properties and cheese yield are economically important to the Spanish dairy industry. The present study aims to identify candidate genes and their regulators related to 14 milk and cheese-making traits and to develop a low-density panel of markers that could be used to predict an individual's genetic potential for cheese-making efficiency. In this study, we performed a combination of the classical genome-wide association study (GWAS) with a stepwise regression method and a pleiotropy analysis to determine the best combination of the variants located within the confidence intervals of the potential candidate genes that may explain the greatest genetic variance for milk and cheese-making traits. Two gene networks related to milk and cheese-making traits were created using the genomic relationship matrices built through a stepwise multiple regression approach. Several co-associated genes in these networks are involved in biological processes previously found to be associated with milk synthesis and cheese-making efficiency. The methodology applied in this study enabled the selection of a co-association network comprised of 374 variants located in the surrounding of genes showing a potential influence on milk synthesis and cheese-making efficiency.

The effect of additive containing an organic form of iodine on the physiological-biochemical parameters of the body of cows

Iodine deficiency in soil and water in many countries leads to its low content in plants and animal feed produced from them. The limited intake of this element in animals can lead to endemic diseases. The lack of iodine in animal feeding is most often compensated for by the use of additives with an inorganic form of iodine, which can be poorly absorbed by the body. Feed products with an organic form of iodine have a great biological effect. A study on the effect of iodine-containing additives on the physiological and biochemical parameters of the animal organism was carried out on two groups of 15 cows. The experimental group was fed an organic form of iodine as part of the additive, the control group received an inorganic form of iodine. For all animals during the experiment the biochemical parameters of blood, milk productivity and reproductive ability were studied. During the experiment, an increase in metabolic and redox processes in the body was noted in the experimental group. An increase in mineral metabolism, including iodine content, was found. Due to the sufficient intake of organic iodine in the animals of the experimental group, there was an increase in the activity of the main hepatic enzymes AST and ALT. An increase in the process of gluconeogenesis due to an increase in the glucose content in the blood of experimental cows was revealed. An increase in milk production and reproductive function of animals of the experimental group was established. Within 30 days after the termination of feeding the supplement with the organic form of iodine in the experimental group, a prolonging effect was observed, consisting in higher values of blood biochemical parameters, improved reproductive function and milk productivity relative to equivalent animals in the control. As a result, it was concluded that the use of an additive with an organic form of iodine in the amount of 1.5 g in feeding cows for 60 days increases the iodine content in the blood serum of animals and increases the performance of all types of metabolism, which may indicate the best stimulating effect of the organic form of iodine on thyroid activity glands. This in turn helps to improve the productive and reproductive qualities of animals. To recommend the studied drug as a means to replenish iodine deficiency in animals and to more accurately analyze its effect on the hormone-forming function of the thyroid gland, it is necessary to study the level of thyroid hormones in the blood.

Influence of elevated protein and tannin-rich peanut skin supplementation on growth performance, blood metabolites, carcass traits and immune-related gene expression of grazing meat goats

The aim of the present study was to define whether elevated rumen-undegradable protein (RUP) and tannin-rich peanut skin (PS) supplementation would affect animal growth performance, average daily gain (ADG), blood metabolites, carcass traits associated with lipogenic and immune-related gene expressions in meat goats grazing winter wheat (WW). Thirty-six Kiko-crossbreed male goats at approximately 6 months of age were blocked by body weight (BW; 25.6 ± 1.1 kg) and randomly assigned to one of the four treatments with two replicates based on a 2 × 2 factorial design. Diets contained PS replacing alfalfa meal (ALM), without or with RUP supplementation. Both PS and ALM were incorporated into grain mix portion of the diet and pelletized, with remaining diets fed ad libitum of WW forage for a period of 51 days. Lipogenic genes examined included SCD, ACLY, YWHAZ, PPIA and FABP4, while immune-related genes examined included ACTB (as a control gene), H3F3A, PPIA, IRF3, STAT2, HERC3 and IFIT3 antibody genes. The meat goats on PS-pellet-supplemented group with or without RUP supplementation grew 38.5% faster ADG (p < .001) when compared to control-supplemented group. When goats received PS diet, empty body weight, hot carcass, cold carcass, shoulder, hind shank, rack, loin and fat thickness were greater (p < .05) than control diet. Animals on PS-pellet had higher ACLY, YWHAZ, PPIA and FABP4 gene expression (p < .05) when compared to ALM-pellet control, with RUP by PS-pellet interactions (p < .01). Goats receiving additional RUP supplementation had increased (p < .05) STAT2 gene expression, whereas goats receiving PS-pellet supplementation showed increased STAT2 (p < .05) and a tendency to increase IRF3 (p = .07) gene expressions. In conclusion, the addition of PS-pellet or RUP supplementation has the potential to improve ADG and altered selected lipogenic and immune-related gene expressions.

Changes in the blood routine, biochemical indexes and the pro-inflammatory cytokine expressions of peripheral leukocytes in postpartum dairy cows with metritis

BACKGROUND

The aim of the present study was to clarify the changes in complete blood count, blood biochemistry, and the gene expressions of pro-inflammatory cytokines of peripheral white blood cells in postpartum dairy cows with metritis.

RESULTS

The cows were assigned to the control group (n = 28) or the metritis group (n = 28), retrospectively. Blood samples were taken 7 days before the estimated parturition (- 7 d), on the day of parturition (0 d), and 7 and 30 d after parturition. There was no difference in blood indexes between the control group and the metritis group at - 7 d. The WBC, granulocytes and monocytes were generally higher at 7 and 30 d in the metritis group than the control. In comparison with the controls, all liver function parameters and triglyceride levels at 0, 7 and 30 d, and the creatinine level at 7 and 30 d were higher in cows with metritis. The concentrations of Ca and P at 0, 7 and 30 d, and of glucose at 0 d were lower for cows in the metritis group compared with cows in the control group. Among these parameters, the WBC at 30 d, the aspartate aminotransferase activity (AST) at 7 d exceeded normal ranges (WBC: 5.0 ~ 16.0 × 10⁹/L; AST: 42.5 ~ 98 U/L), whereas the concentrations of glucose and Ca from 0 to 30 d were below normal ranges (glucose: 2.5 ~ 4.5 mmol/L; Ca: 2.2 ~ 2.5 mmol/L) in the metritis group. The gene expressions of pro-inflammatory cytokines in the metritis group were higher than those in the control group, including the IL-1α at 7d, the IL-1β at - 7, 0 and 7 d, the IL-6 at - 7, 0, 7 and 30 d, the IL-8 at 0, 7 and 30 d, and the TNF-α at 7 and 30 d.

CONCLUSION

The cows with metritis experienced systemic inflammation for 4 weeks after calving, the impaired hepatic function, and the altered metabolic status with increased triglyceride level and decreased concentrations of glucose, Ca and P.

Days-in-Milk and Parity Affected Serum Biochemical Parameters and Hormone Profiles in Mid-Lactation Holstein Cows

It is well known that serum biochemical parameters and hormones contribute greatly to the physiological and metabolic status of dairy cows. However, few studies have focused on the variation of these serum parameters in multiparous mid-lactation cows without the interference of diet and management. A total of 287 Holstein dairy cows fed the same diet and maintained under the same management regime were selected from a commercial dairy farm to evaluate the effects of days-in-milk (DIM) and parity on serum biochemical parameters and hormone profiles. Milk yield and milk protein content were affected by DIM and parity (p < 0.05). Milk protein yield showed a numerically decreasing trend with parity, and it was relatively constant in cows with parities between 2 and 4 but lower in cows with parity 6 (p = 0.020). Ten and five serum biochemical parameters related to protein status, energy metabolism, liver and kidney function, and oxidative stress were affected by DIM and parity, respectively (p < 0.05). Glucagon, insulin-like growth factor 1 concentration, and the revised quantitative insulin sensitivity check index were significantly different (p < 0.05) among cows with different DIM. Parity had no effect on hormone concentrations. An interaction between DIM and parity effect was only detected for glucagon concentration (p = 0.015), which showed a significantly increasing trend with DIM and overall decreasing trend with parity. In summary, DIM and parity played an important role in affecting the serum biochemical parameters and/or hormones of dairy cows, with serum parameters affected more by DIM than parity.

Hormonal correlates of energetic condition in mantled howler monkeys

Hormones have a key role in energy allocation, so their study allows understanding individual metabolic strategies. Because different hormones convey different information on the responses of individuals to energetic demands, a simultaneous analysis of variation in multiple hormones may offer a more reliable picture of metabolic strategies than single hormone assessments. In this study we focused on determining which factors were related to variation in fecal glucocorticoid and thyroid hormone metabolites in wild mantled howler monkeys (Alouatta palliata). Over 12months, we determined fecal glucocorticoid and thyroid hormone metabolite levels of 11 adults belonging to two groups, and examined the relationship between hormone metabolites and a variety of behavioral, physiological, and ecological factors (e.g., food intake, sex/reproductive state, activity, participation in agonistic interactions). We found that glucocorticoids were elevated in gestating and lactating females compared to males and cycling females, and were also higher when individuals were more active and participated in agonistic interactions. Thyroid hormone levels were also related to sex/reproductive state and activity, but were additionally positively related to fruit intake and negatively related to young leaf intake. Our study demonstrates that the non-invasive measurement of glucocorticoid and thyroid hormones of howler monkeys allows assessing different underlying physiological processes. By combining different biomarkers, which has seldom been done with wildlife, we could also parse the influence of psychological vs. metabolic challenges for individual energetic condition, which may be instrumental for deciding which factors should be accounted for when studying different hormone-behavior interactions.

Variation in blood serum proteins and association with somatic cell count in dairy cattle from multi-breed herds

Blood serum proteins are significant indicators of animal health. Nevertheless, several factors should be considered to appropriately interpret their concentrations in blood. Therefore, the objectives of this study were (1) to assess the effect of herd productivity, breed, age and stage of lactation on serum proteins and (2) to investigate association between serum proteins and somatic cell count (SCC) in dairy cattle. Milk and blood samples were collected from 1508 cows of six different breeds (Holstein Friesian, Brown Swiss, Jersey, Simmental, Rendena and Alpine Grey) that were housed in 41 multi-breed herds. Milk samples were analyzed for composition and SCC, while blood samples were analyzed for serum proteins (i.e. total protein, albumin, globulin and albumin-to-globulin ratio (A : G)). Herds were classified as low or high production, according to the cow's average daily milk energy yield adjusted for breed, days in milk (DIM) and parity. Data were analyzed using a linear mixed model that included the fixed effects of DIM, parity, SCS, breed, herd productivity and the random effect of the Herd-test date within productivity level. Cows in high producing herds (characterized also by greater use of concentrates in the diet) had greater serum albumin concentrations. Breed differences were reported for all traits, highlighting a possible genetic mechanism. The specialized breed Jersey and the two dual-purpose local breeds (Alpine Grey and Rendena) had the lowest globulin concentration and greatest A : G. Changes in serum proteins were observed through lactation. Total protein reached the highest concentration during the 4th month of lactation. Blood albumin increased with DIM following a quadratic pattern, while globulin decreased linearly. As a consequence, A : G increased linearly during lactation. Older cows had greater total protein and globulin concentrations, while albumin concentration seemed to be not particularly affected by age. A linear relationship between serum proteins and SCS was observed. High milk SCS was associated with greater total protein and globulin concentrations in blood. The rise in globulin concentration, together with a decrease in albumin concentrations, resulted in a decline in A : G as SCS of milk increased. In conclusion, such non-genetic factors must be considered to appropriately interpret serum proteins as potential animal welfare indicator and their evaluation represents an important first-step for future analysis based on the integration of metabolomics, genetic and genomic information for improving the robustness of dairy cows.

Chromium Supplements in the Feed for Lactating Murrah Buffaloes (Bubalus bubalis): Influence on Nutrient Utilization, Lactation Performance, and Metabolic Responses

This study was conducted to evaluate the effect of different levels of inorganic chromium (Cr) on nutrient intake, nutrient utilization, milk mineral contents, and blood biochemical in lactating Murrah buffaloes. Twenty-four multifarious Murrah buffaloes were blocked into four groups having six animals in each group and fed for 150 days post-partum. Feeding regimen was same in all the groups except that treatment groups were supplemented with 0.0, 0.5, 1.0, and 1.5 mg inorganic Cr/kg dry matter (DM) in the four respective groups. Group fed on basal diet supplemented with 0.0 mg Cr/kg DM served as a control. Adding inorganic Cr to the diet of lactating buffaloes increased feed intake, milk yield, and nutrient digestibility. Nitrogen (N) and Cr balance were significantly increased (P<0.05) by adding Cr. Milk and plasma Cr concentration could be increased by adding Cr (P<0.001), while no significant differences were found between the four treatments in milk and plasma concentration of calcium (Ca), copper (Cu), and zinc (Zn). Feeding of diet supplemented with inorganic Cr decreased plasma insulin concentration (P=0.016). Concentration of blood glucose and the ratio of blood glucose to insulin were increased by adding Cr (P=0.037 and P=0.011, respectively). Adding Cr to the diet of lactating buffaloes did not show any effect on blood hemoglobin (Hb), while plasma concentration of progesterone and antioxidant status was increased (P<0.05). It could be concluded that adding Cr to the diet of lactating buffaloes improved nutrient intake, nutrient utilization, and lactation performance.

Effects of prolonged consumption of water with elevated nitrate levels on certain metabolic parameters of dairy cattle and use of clinoptilolite for their amelioration

Elevated levels of nitrates in feed and water can pose a significant risk for dairy cattle, due to their cumulative action. The effect of prolonged consumption of water naturally contaminated with nitrates on some metabolic parameters in dairy cows was investigated at the present study. Concurrently, whether in-feed inclusion of clinoptilolite, a natural zeolite with high selectivity for ammonia cations, could ameliorate nitrate consumption consequences was examined. Two experiments were run simultaneously in two farms each. In both, farms were assigned into two groups according to nitrate levels in borehole water (NG > 40 ppm; CG < 40 ppm). Furthermore, in experiment 2, the incorporation of clinoptilolite in the ration was taken into account (NC-clinoptilolite feeding; CNC-controls). In experiment 1, blood urea nitrogen (BUN) and beta-hydroxybutyrate (BHBA) concentrations appeared to be affected by nitrate consumption and were significantly higher in NG animals. In experiment 2, BUN concentration was significantly lower in the NC group. The prolonged consumption of water with increased nitrate levels seemed, to some degree, to impair protein metabolism and glucose utilization, while the dietary administration of clinoptilolite could alleviate the nitrates' effects.

Improving Productive and Reproductive Performance of Holstein Dairy Cows through Dry Period Management

To determine the effects of dry period (DP) length on milk yield, milk composition, some blood metabolites, complete blood count (CBC), body weight and score and follicular status, twenty five primiparous and multiparous Holstein cows were assigned to a completely randomized design with DP-60 (n = 13) and DP-20 (n = 12) dry period lengths. Cows in the DP-60 produced more milk, protein, SNF, serum non-esterified fatty acids (NEFA) and beta hydroxyl butyrate acid (BHBA) compared with cows in DP-20 (p≤0.05). Serum glucose, blood urea nitrogen (BUN), urea, and glutamic oxaloacetic transaminase (GOT) were all similar among the treatments. Body Condition Score (BCS), body weight (BW), complete blood count (CBC) and health problems were similar between the treatments. Diameter of the first dominant follicle and diameter of the dominant follicle on d 14 were different among the treatments. Thus, results of this study showed that reducing the dry period length to DP-20 had a negative effect on milk production, milk composition and reproductive performance in Holstein dairy cows.

Influence of fresh forage-based diets and αs₁-casein (CSN1S1) genotype on nutrient intake and productive, metabolic, and hormonal responses in milking goats

Polymorphism at the αS1-casein locus (CSN1S1) in goats influences several milk production traits. Milk from goats carrying strong alleles, which are associated with high αS1-casein (αS1-CN) synthesis, has higher fat and casein contents, longer coagulation time and higher curd firmness than milk from goats with weak alleles linked to low αS1-CN content. Nutrition also affects these milk properties; therefore, it is important to better understand the interaction between dietary characteristics and the CSN1S1 genotype in goats. This study aimed to investigate the effect of fresh forage based diet or energy supplement on feeding behavior, milk production, and metabolic and hormonal parameters of Girgentana goats with different genotypes at CSN1S1 loci. From a group of goats genotyped by PCR at the DNA level, 12 were selected because they had the same genotype for αS2-CN, β-CN, and κ-CN but a different genotype for αS1-CN: 6 were homozygous for strong alleles at the CSN1S1 loci (AA) and 6 were heterozygous for a weak allele (AF). Goats of each genotype were allocated to 3 subgroups and fed 3 diets ad libitum in a 3×3 Latin square design. The diets were sulla (Hedysarum coronarium L.) fresh forage, sulla fresh forage plus 800 g/d of barley meal (SFB), and mixed hay plus 800 g/d of barley meal (MHB). Diet had a stronger effect than CSN1S1 genotype. The SFB diet led to the highest energy intake, dry matter (DM) digestibility, and milk yield. The fresh forage diets (SFF and SFB) increased DM and crude protein (CP) intake, CP digestibility, and milk CN compared with the MHB diet. The diets supplemented with energy (SFB, MHB) reduced milk fat and urea, improved CP utilization for casein synthesis, and limited body fat mobilization, in accordance with a lower level of nonesterified fatty acids and higher levels of glucose and IGF-1. With regard to CSN1S1 genotype, AA goats showed higher CP digestibility and lower free thyroxine hormone and cholesterol levels than AF goats. Significant diet × genotype interactions indicated how AA goats, compared with AF goats, showed higher DM digestibility and milk yield when fed the SFB diet, which had more energy. A reduction in free triiodothyronine hormone occurred in AF goats fed the MHB diet, whereas no differences were observed in AA goats. These results demonstrate how goats with a higher capacity for αS1-CN synthesis exhibit more efficient energy and protein utilization, evident at the digestive level, and better productive responses to high-nutrition diets.

Effect of long-term feed restriction on the health status and welfare of a robust horse breed, the Shetland pony (Equus ferus caballus)

Outdoor group housing is increasingly recognized as an appropriate housing system for domesticated horses. The objective of this study was therefore to investigate the effect of potential feed shortage in semi-natural horse keeping systems in winter on animal health and welfare. In 10 female Shetland ponies blood concentrations (NEFA, total protein (TP), total bilirubin (TB), beta-hydroxybutyrate (BHB) and thyroxine (T4)), body mass and the body condition score (BCS) were monitored for 7 months including a 4 months period of feed restriction in five of the 10 ponies. Restrictively fed animals lost 18.4±2.99% of their body mass and the BCS decreased by 2.2±0.8 points (BCS scale: 0=emaciated, 5=obese). Feed restriction led to a continuous increase in TB (P<0.001) and NEFA (P<0.01) concentrations compared to control ponies. The TP and BHB values only differed at the end of the trial with lower concentrations in restricted fed mares (P<0.05). Feed restriction had no effect on thyroxine concentrations. TB concentrations in the feed restricted group were out of the reference range during the entire feeding trial. The increased NEFA concentrations in feed restricted compared to control ponies suggest that fat was mobilized. The BCS, as well as plasma NEFA and TB concentrations were good indicators for a rapid detection of possible health problems caused by undernourishment in horses when kept under semi-natural conditions. In contrast, blood parameters of the control animals were within the reference ranges, suggesting that a year round outdoor housing with additional feed supply is an adequate housing system for a robust horse breed like the Shetland pony.

Effects of pine bark supplementation on performance, rumen fermentation, and carcass characteristics of Kiko crossbred male goats

Twenty-two Kiko crossbred male goats (Capra hircus; initial BW = 27.5 ± 1.04 kg) were used in a randomized complete block design to determine the effects of feeding pine bark (PB; Pinus taeda L.) on animal performance, rumen fermentation, blood parameters, fecal egg counts (FEC), and carcass characteristics in goats. Experimental treatments included the control diet [0% PB plus 30% wheat straw (WS)], 15% PB plus 15% WS, and 30% PB plus 0% WS (on as-fed basis), where PB replaced WS. Freshly air-dried PB and WS were finely (1.5 to 3.0 mm) ground and incorporated in the grain mixes. Experimental diets provided a total of 1.9, 16.3, and 32 g of condense tannins (CT)/kg DM in 0%, 15%, and 30% PB diets, respectively. The grain mixes were fed daily at 85% of the feed offered, with remaining 15% consisting of Bermuda grass hay (Cynodon dactylon). Animals were fed once a day at 0800 h, and feed offered and refused was monitored for an 83-d performance period. Rumen and blood samples were collected at d 0, 50, and 80 of the study. Carcass traits were assessed after slaughter at the end of performance period. There was no difference in initial BW, hay, and total NDF intake among treatments; however, final BW (P = 0.06), ADG (P < 0.01), grain mix intake (P < 0.001), total DMI (P < 0.001), and G:F (P < 0.04) increased linearly as the PB increased in the diets. Rumen ammonia N, acetate, isovalerate and acetate-to-propionate ratio were reduced linearly (P < 0.05). There was no difference in carcass traits except cold carcass weight (P = 0.06), which tended to increase linearly in goats fed 15% and 30% PB. Breast, sirloin, trim trait, liver, and hide weight increased (linear; P < 0.01) with addition of PB. Blood basophils, alanine transaminase, aspartate aminotransferase, albumin, Na, and Cl concentrations decreased (linear; P < 0.02 to 0.01) as PB supplementation increased. Supplementation of PB reduced (linear; P < 0.01) average FEC. Addition of PB in the diets improved performance, reduced FEC, and favorably modified rumen fermentation.

Metabolism of grazed vs. zero-grazed dairy cows throughout the vegetation period: hepatic and blood plasma parameters

Grass may have a differential impact on the metabolism of the dairy cow, depending on the grazing system applied. In this study, the hypothesis was tested that metabolism of grazed vs. zero-grazed dairy cows is differently regulated throughout the vegetation period. The study included three experimental periods (p1, p2 and p3) of 14 days each, and two treatments [grazing from pasture, PASTURE, n = 9; or zero-grazing in a free-stall barn (BARN, n = 9)]. Blood and liver samples were collected at the end of each period when the cows were on average 64, 120 and 197 DIM. Concentrations of metabolites and hormones, and activities of various enzymes were determined in plasma. Liver samples were measured for mRNA abundance of genes encoding enzymes and nuclear receptors involved in metabolic pathways. PASTURE cows had higher plasma concentrations of T(3), BHB, and total protein than BARN cows across periods (p < 0.05). BARN cows had higher concentrations of NEFA (in p1) and urea (in p1 and p2) in relation PASTURE cows (p < 0.05), and had higher mRNA abundance of liver-X-receptor-α and glycerol-3-phosphate-acyltransferase across periods (p < 0.05). The results confirm the hypothesis that metabolism is different between BARN and PASTURE cows throughout the vegetation period, and show that the observed differences are mainly reflected in parameters of lipid metabolism.

Postcalving factors affecting conception risk in Holstein dairy cows in tropical and sub-tropical conditions

The objective was to identify postpartum risk factors between nutritional imbalance and health disorders affecting first-service conception risk (FSCR) in 21 commercial Holstein herds in Reunion Island. Multivariate logistic-regression models including herd as a random effect were used to analyze the relationship between FSCR and energy status, nitrogen status, hepatic function, mineral deficiencies, and postpartum health disorders. Two models (A and B) were built on two subsets of data (n=446 and n=863) with risk indicators measured during the first month of lactation and around time of first service, respectively, adjusted for season, breed, parity, origin, milk yield, calving to first service interval (CS1), and type of estrus (spontaneous vs. induced). The averaged conception risk was 0.266+/-0.015 (n=913) (mean+/-S.E.M.). In both models, FSCR was decreased by CS1 < or = 60 d and induced estrus. In model A, FSCR was decreased (p<0.05) for cows with mean cumulative 100 d daily milk yield < or =23 kg/d and >27 kg/d, with losses of body condition score >1.5, and with retained placenta. In model B, FSCR was decreased (p<0.05) for cows inseminated during wet season, previously raised out of the farm as nulliparous, with blood magnesium concentration < or =0.9 mmol/L, and for high-yielding cows (100 d milk yield > 27 kg/d) with glutamate deshydrogenase>17 UI/L. Hence, high-body-lipid mobilization during the first month of lactation was a strong nutritional predictor of low FSCR together with liver damage in high-yielding cows. Interestingly, our models revealed that infertility is better related to nutritional factors than to postpartum health disorders occurrence.

Effects of parity and body condition at parturition on endocrine and reproductive parameters of the cow

The effect of parity (multiparous vs primiparous) and body condition score (BCS; <3.0 or ≥3.0, lean vs fat) at parturition on metabolic and endocrine profiles from 1 month before to 2 months after parturition were studied in 42 Holstein cows grazing on improved pastures. BCS and milk production were determined every 2 weeks. Non-esterified fatty acids (NEFA), β-hydroxy-butyrate (BHB), insulin, IGF-I, leptin, thyroxine (T4) and 3,3′,5-tri-iodothyroinine (T3) were determined in plasma every 10 days. Progesterone was determined three times per week after parturition. Primiparous cows had a lower BCS during the early postpartum period and produced less milk than multiparous animals. Primiparous cows had higher NEFA concentrations and they presented more samples with BHB concentrations of >1 mmol/l than multiparous cows. Multiparous cows had higher T3, T4 and IGF-I concentrations, while fat cows had higher leptin and IGF-I concentrations. All hormone concentrations were diminished in the first week postpartum. Primiparous cows and fat cows presented a steeper decay of IGF-I and leptin around parturition than multiparous cows and lean cows. While thyroid hormones and IGF-I showed increasing concentrations from approximately day 30, leptin concentrations remained low until the end of the experimental period. The initiation of ovarian cyclicity was delayed in primiparous cows and especially in primiparous lean cows, consistent with longer intervals from parturition to first service and to conception. The endocrine signals most likely to inform the reproductive axis regarding a negative energy balance were IGF-I and leptin.

Time empty and ketone body status in the early postpartum period of dairy cows

This study aimed to assess the effect of ketone body status early postpartum on time empty in 74 multiparous dairy cows under field conditions. Animals were equally distributed across eight farms and were controlled by the same herd-fertility-monitoring programme. Cows were visited twice antepartum and six times postpartum at weekly intervals between 0530 and 0830 a.m. On these occasions, body condition scores and milk yields were measured, blood and milk samples were taken, cows were gynaecologically examined, and parameters of reproduction were recorded. Cows with a time empty of less or more than 80 days were classified as early and late conceiving cows (EC and LC, respectively). A time empty of 80 days results in calving-to-calving intervals of 1 year and classification based on this threshold value resulted in groups of equal size and equal distribution of EC and LC within farms. Ketone bodies measured were beta-hydroxybutyrate in blood and acetoacetate and acetone in blood and milk. Blood and milk ketone body concentrations, as well as the ratios of acetoacetate and acetone to beta-hydroxybutyrate, over the first 6 weeks postpartum were higher in LC than in EC, whereas plasma glucose and non-esterified fatty acids and milk fat, protein and urea concentrations did not exhibit clear differences between groups. Ketone body concentrations were as good predictors of time empty as ketone body ratios and might have practical impact in herd-fertility-monitoring programmes.

Body condition scores in dairy cows: associations with metabolic and endocrine changes in healthy dairy cows

Relationships between body condition scores (BCS), metabolic profiles and endocrine traits were investigated in 53 healthy Red Holstein cows. Cows were categorized into groups based on BCS ante-partum (a.p.: >3.25 or < 3.25) and on BCS losses during the first 8 weeks after calving (ABCS8 > 0.75 or < or = 0.75). Blood samples were collected 1 week before calving and every 2 weeks post-partum (p.p.). Cows with BCS a.p. >3.25 and deltaBCS < or = 0.75 were oldest and cows with BCS a.p. < or = 3.25 and deltaBCS < or = 0.75 were youngest. Cows with BCS > 3.25 a.p. and that lost > 0.75 BCS in the first 2 months of lactation exhibited signs of subclinical ketosis. If statistically adjusted for the effect of lactation number, average milk yield within the first 8 weeks p.p. and milk fat concentrations were similar between BCS groups, whereas milk protein concentrations differed significantly between BCS groups. Significant differences between groups were observed for blood plasma glucose, bilirubin, beta-hydroxybutyrate, non-esterified fatty acids and insulin concentrations. No differences were seen for albumin, urea, insulin-like growth factor-1, and 3.5.3'-triiodothyronine concentrations and for plasma activities of glutamate-oxalacetate transaminase, gamma-glutamyltransferase and glutamate dehydrogenase. There was a good agreement between BCS and profiles of metabolites and hormones related to energy metabolism in clinically healthy cows. Cows in good body condition a.p. had greater risks of metabolic problems because of excessive mobilization of body reserves. However, the metabolic status was best in cows with a BCS > 3.25 a.p.. if they did not lose much body condition p.p.

Metabolic, enzymatic and endocrine status in high-yielding dairy cows--Part 2

Pairs of 29 high-yielding (HC) dairy cows (> or = 45 kg/day reached at least once during lactation) and 29 corresponding control (CC) cows (with milk yields representing the average yield of the herds) were studied in 29 Swiss farms from March 1995 to September 1996. The hypothesis tested was that there are differences in metabolic, enzymatic and endocrine status between HC and CC cows. Cows were studied 2 weeks before and at 5, 9, 13, 17 and 40 weeks post-partum. Concentrations of metabolites, minerals and hormones and enzyme activities were in the normal range in both HC and CC cows. Changes in metabolic and endocrine traits in early lactation expressed insufficient energy intake, but were similar in both HC and CC cows. Homeorhetic and homeostatic control of metabolism in HC cows was thus adequate to adjust to and allow high milk yields. Under adequate husbandry, management and feeding conditions, metabolic disease problems in HC cows [10,500 kg energy-corrected milk (ECM)/lactation, peak yields of > or = 45 kg ECM/day] can be avoided.

Twenty-four-hour patterns of hormones and metabolites in week 9 and 19 of lactation in high-yielding dairy cows fed triglycerides and free fatty acids

Effects of feeding crystalline triglycerides (TGA), free fatty acids (FFA), and a starch-rich ration (STA) on metabolite and hormone concentrations in blood plasma were studied in high-yielding dairy cows over a 24-h period in week 9 and 19 of lactating. Energy-corrected milk production in the three groups was similar, but was lower in week 19 than in week 9. Energy and protein intakes were greater in week 9 than in week 19, but energy and protein balances in the three groups and in weeks 9 and 19 were similar. Plasma glucose and triglyceride concentrations were lower in week 9 than in week 19. In cows fed FFA, glucose concentrations were highest in week 9. Plasma triglyceride, phospholipid and cholesterol concentrations were highest, whereas beta-hydroxybutyrate concentrations were lowest in FFA-fed cows in weeks 9 and 19. Concentrations of insulin-like growth factor-I in week 19 were lower in cows fed TGA and FFA than in those fed the starch-rich ration. Post-prandial responses were usually greater following morning than afternoon meals. Fructosamine, albumin, urea, growth hormone, thyroxine, and 3,5,3'-triiodothyronine concentrations were similar in weeks 9 and 19 and were not influenced by dietary treatment or feeding times. In conclusion, there were distinct metabolic and endocrine effects of feeding TGA and FFA compared with STA and the concentrations as well as the 24-h changes of various metabolic and endocrine traits in weeks 9 and 19 of lactation were also different.

Longissimus dorsi muscle diameter, backfat thickness, body condition scores and skinfold values related to metabolic and endocrine traits in lactating dairy cows fed crystalline fat or free fatty acids

An experiment was performed using 18 dairy cows with > or = 2 lactations from parturition until week 20 of lactation to investigate the effects of feeding rumen-protected crystalline fat (group A) or free fatty acids (group B) compared with a control group not fed supplemental fat or fatty acids (group C). The feeding effects studied were those on milk yield and composition, body weight (BW), body conditions scores (BCS), skinfold values (a measure of subcutaneous fat tissue thickness), backfat thickness and longissimus dorsi muscle diameter (measured by ultrasound), as well as on blood plasma metabolic and endocrine traits. Fat and fatty-acid feeding reduced roughage intake. Net energy and protein balances during the first week of lactation were negative. Milk yield was similar in all groups, but concentrations of milk fat were reduced in group B and of milk protein in groups A and B. BW, BCS, skinfold value, backfat thickness and longissimus dorsi muscle diameter similarly decreased in all groups until weeks 8-12. Concentrations of glucose and fructosamine decreased transiently during early lactation, whereas levels of beta-hydroxybutyrate, urea, total protein and albumin increased reversibly and similarly in all groups. Concentrations of creatinine decreased similarly in all groups until week 4 and those of nonesterified fatty acids until week 12. Triglyceride concentrations increased continuously until week 18, whereas concentrations of phospholipid and cholesterol increased until week 10 and then remained elevated. Triglyceride, phospholipid and cholesterol concentrations were higher in group B than in groups A and C throughout the experiment. Concentrations of insulin, insulin-like growth factor-1, thyroxine and 3,5,3'-triiodothyronine started to increase after the first 6-8 weeks of lactation, while those of growth hormone were transiently low in week 16. None of the hormones exhibited group differences. In this study rumen-protected fat or fatty-acid supplementation failed to improve the energy and protein balances during early lactation and did not affect milk yield, likely due to decreased roughage intake. BCS, skinfold values and backfat ultrasound measurements of subcutaneous adipose tissue mass and of longissimus dorsi muscle diameter indicated mobilization of fat tissue and protein mobilization in early lactation and were mirrored by typical changes of metabolic and endocrine traits.

Changes of blood metabolites and hormones in breeding calves associated with weaning

Changes of blood metabolites and hormones were studied in female breeding calves before, during and after weaning from 4 to 18 weeks of age. Calves were initially fed increasing amounts of whole milk (up to 7 kg/day in week 8 of life). Milk intake was then gradually decreased up to the age of 16 weeks, when calves were completely weaned and only fed hay and concentrates. Average daily gain was 0.85 kg. Postprandial concentrations of glucose, insulin, insulin-like growth factor-I and 3.5.3'-triiodothyronine concentrations gradually decreased (P < 0.05) with age, while those of beta-hydroxybutyrate, protein, albumin, haemoglobin and iron increased (P < 0.05). Concentrations of cholesterol transiently increased, whereas those of urea reversibly decreased. Non-esterified fatty acids, triglycerides and growth hormone did not consistently change during the duration of the study. In conclusion, changes of glucose, beta-hydroxybutyrate, haemoglobin, iron, insulin, insulin-like growth factor-I and 3.5.3'-triiodothyronine were markedly different from those usually seen in veal calves of the same age.