Effects of dietary energy source on energy balance, metabolites and reproduction variables in dairy cows in early lactation

This paper summarizes three recent studies by the same authors with the objective to study the effect of dietary energy source on the energy balance (EB) and risk for metabolic and reproductive disorders in dairy cows in early lactation. The first study, a literature survey, illustrated that feeding extra glucogenic nutrients relative to lipogenic nutrients, decreased milk fat and seems to decrease plasma non-esterified fatty acid (NEFA) and beta-hydroxybutyrate (BHBA) concentration. However studies are scarce and mostly confound the effect of energy source with level of energy intake, compromising eventual effects on EB and fertility. Therefore, in the second study, 16 dairy cows were either fed a glucogenic or a lipogenic diet (isocaloric) and EB was determined in climate-controlled respiration chambers from week 2 until 9 of lactation. Glucogenic diet decreased milk fat yield and milk energy and tended to decrease body fat mobilization compared with lipogenic diet. The objective of the third study was to study the effect of dietary energy source on EB, metabolites and reproduction variables. Dairy cows (n=111) were fed glucogenic, lipogenic or mixed diet from week 3 until week 9 relative to calving. Multiparous cows fed glucogenic diet had lower milk fat yield, higher calculated EB, and lower plasma NEFA, BHBA and liver triacylglyceride concentration and tended to have fewer days to first postpartum ovulation. In conclusion, increasing the glucogenic nutrient availability improved the EB and had potential to reduce the risk for metabolic disorders and to improve reproductive performance in dairy cows.     

Follicular dynamics, plasma metabolites, hormones and insulin-like growth factor I (IGF-I) in lactating cows with positive or negative energy balance during the preovulatory period.

The effect of dietary energy balance (EB) on growth of ovarian follicles was tested. Cows (n = 9) were fed a high energy diet (HE diet; positive EB; n = 4) or switched to a low energy diet (LE diet; negative EB; n = 5) during the preovulatory period. Non-esterified fatty acids (NEFA) were greater in cows fed the LE diet. Concentrations of luteinizing hormone (LH) were similar in HE and LE cows. However, the growth of preovulatory follicles in cows fed the LE diet was 50% that of cows fed the HE diet. Insulin-like growth factor-I (IGF-I) in plasma was less in LE-fed cows compared with HE-fed cows, and plasma IGF-I was positively correlated to estrogen: progesterone ratio in follicular fluid of dominant follicles. In summary, slower follicular growth in cows fed an LE diet occurred despite normal plasma LH and coincided with reduced IGF-I and elevated NEFA in plasma.     

Effects of long-term supplementation of dairy cow diets with rumen-protected conjugated linoleic acids (CLA) on performance, metabolic parameters and fatty acid profile in milk fat

The supplementation of conjugated linoleic acids (CLA) to the rations of dairy cows represents an opportunity to reduce the content of milk fat. Therefore, CLA have the potential beneficial effect of reducing energy requirements of the early lactating cow. The present study aimed at the examination of long-term and posttreatment effects of dietary CLA intake on performance, variables of energy metabolism-like plasma levels of non esterified fatty acids (NEFA) and beta-hydroxybutyrate (BHB), and fatty acid profile in milk fat. Forty-six pregnant German Holstein cows were assigned to one of three dietary treatments: (1) 100 g/ d of control fat supplement (CON), (2) 50 g/d of control fat supplement and 50 g/ d of CLA supplement (CLA-1) and (3) 100 g/d of CLA supplement (CLA-2). The lipid-encapsulated CLA supplement consisted of approximately 10% of trans-10, cis-12 CLA and cis-9, trans-11 CLA each. The experiment started 1 d after calving and continued for about 38 weeks, divided into a supplementation (26 weeks) and a depletion period (12 weeks). Over the first 7 weeks of treatment, 11 and 16% reductions in dry matter intake compared to control were observed for the cows fed CLA-1 and CLA-2 supplements respectively. Consequently, the calculated energy balance for these two CLA groups was lower compared to the control. Plasma levels of NEFA and BHB remained unaffected. Later in lactation the highest CLA supplementation resulted in a reduction of milk fat content of 0.7%. However, no reduction in milk fat yield, and accordingly no milk fat depression (MFD), could be shown. The trans-10, cis-12 CLA in milk fat increased with increasing dietary CLA supplementation in a dose-dependent manner. The proportion of C16 in milk fat was decreased by the highest CLA supplementation. With the exception of an increase in plasma glucose level in the CLA-2 group, no post-treatment effects were observed. Overall, under the conditions of the present study no improvement in the calculated energy balance by CLA supplementation could be shown for the entire evaluation period.     

Energy Metabolites,Lipid Variables and Lactation Performance of Periparturient Murrah Buffaloes (Bubalus bubalis) Fed on Diet Supplemented with Inorganic Chromium

The aim of this study was to elucidate the effects of chromium (Cr) supplementation as inorganic Cr (CrCl₃?·?6H₂O) on energy balance, lipid peroxidation, and lactation performance in periparturient Murrah buffaloes. Twenty-four multiparous Murrah buffaloes according to lactation, parity, body mass, and expected calving date were divided equally. Experimental buffaloes were randomly assigned to four treatment diets: a control diet and three diets with an inorganic Cr supplementation at 0.5, 1.0, and 1.5 mg of Cr/kg dry matter (DM), respectively from 60 days before expected calving date until 60 days of lactation. Milk productions of buffaloes were recorded every day until 60 days in milk. Blood samples were collected at days ?60, ?45, ?30,?21, ?15, ?7, ?3, 0, 7, 15, 21, 30, 45, and 60 days relative to actual calving for determination of plasma glucose, nonesterified fatty acid (NEFA), thiobarbituric acid reactive substance (TBARS), total cholesterol, total protein, albumin, blood urea nitrogen (BUN), and minerals. Adding inorganic Cr to the diet of Murrah buffaloes increased milk yield. Percentage of fat and total solid yield increased significantly through the experiment in the Cr-supplemented group. At the day of calving, buffaloes showed a decrease in dry matter intake (DMI), plasma glucose, and zinc (Zn) and Cr concentrations. In contrast, plasma NEFA, TBARS, and copper (Cu) levels were found highest at the day of calving among all groups. Cr supplementation increased peripheral blood glucose concentration while decreased level of NEFA and TBARS was recorded in Cr-fed buffaloes. Supplemental Cr had no effect on plasma cholesterol, total protein, albumin, and BUN in periparturient period. Dietary Cr supplementation had positive effect on plasma Cr concentration, but the plasma concentration of Cu, Zn, and iron (Fe) was not affected by different dietary Cr level supplementation. The results suggest that dietary inorganic Cr supplementation improved milk yield by reducing negative energy balance and lipid peroxidation in buffaloes during periparturient period.     

Milk fatty acids as indicators of negative energy balance of dairy cows in early lactation

Most dairy cows experience negative energy balance (NEB) in early lactation because energy demand for milk synthesis is not met by energy intake. Excessive NEB may lead to metabolic disorders and impaired fertility. To optimize herd management, it is useful to detect cows in NEB in early lactation, but direct calculation of NEB is not feasible in commercial herds. Alternative methods rely on fat-to-protein ratio in milk or on concentrations of non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB) in blood. Here, we considered methods to assess energy balance (EB) of dairy cows based on the fatty acid (FA) composition in milk. Short- and medium-chain FAs (primarily, C14:0) are typically synthesized de novo in the mammary gland and their proportions in milk fat decrease during NEB. Long-chain FAs C18:0 and C18:1 cis-9 are typically released from body fat depots during NEB, and their proportions increase. In this study, these FAs were routinely determined by Fourier-transform infrared spectroscopy (FTIR) of individual milk samples. We performed an experiment on 85 dairy cows in early lactation, fed the same concentrate ration of up to 5 kg per day and forage ad libitum. Daily milk yield and feed intake were automatically recorded. During lactation weeks 2, 4, and 6 after calving, two milk samples were collected for FTIR spectroscopy, Tuesday evening and Wednesday morning, blood plasma samples were collected Thursday morning. Net energy content in feed and net energy required for maintenance and lactation were estimated to derive EB, which was used to compare alternative indicators of severe NEB. Linear univariate models for EB based on NEFA concentration (deviance explained = 0.13) and other metabolites in blood plasma were outperformed by models based on concentrations of metabolites in milk: fat (0.27), fat-to-protein ratio (0.18), BHB (0.20), and especially C18:0 (0.28) and C18:1 cis-9 (0.39). Analysis of generalized additive models (GAM) revealed that models based on milk variables performed better than those based on blood plasma (deviance explained 0.46 vs. 0.21). C18:0 and C18:1 cis-9 also performed better in severe NEB prediction for EB cut-off values ranging from −50 to 0 MJ NEL/d. Overall, concentrations of C18:0 and C18:1 cis-9 in milk, milk fat, and milk BHB were the best variables for early detection of cows in severe NEB. Thus, milk FA concentrations in whole milk can be useful to identify NEB in early-lactation cows.     

Energy balance,leptin, NEFA and IGF-I plasma concentrations and resumption of post partum ovarian activity in swedish red and white breed cows

In the purpose to provide further information in respect of the relationship between metabolism and post partum (PP) ovarian activity resumption in dairy cows, the aim of the present study was to characterize the energy balance (EB) and leptin, NEFA and IGF-I plasma levels in Swedish Red and White (SRW) cows with and without ovarian activity re-initiation within 7 weeks PP. The study was conducted on 12 primiparous SRW cows fed the same diet as total mixed ration for ad libitum intake. The EB was calculated weekly from parturition until seven weeks PP. Blood samples were collected weekly from one week before until 7 weeks after calving for leptin, NEFA and IGF-I analysis. For progesterone (P4) analysis, blood samples were collected two times per week from parturition until the end of the study. P4 profile was used in addition to the clinical examination to detect cows with and without ovarian activity resumption. The clinical and ultrasonographic examination, coupled with P4 profile analysis showed the resumption of ovarian activity within 7 weeks after calving in 8 (group A) and no ovarian resumption in 4 cows (group B). No significant differences were detected in the whole period of observation in the amount of milk production between the two groups, while the mean milk protein content was significantly lower in group B at the third week PP. The calculated EB was negative in both groups in the first three weeks after calving, but more marked in group B. NEFA and Leptin plasma levels did not show significant differences between the two groups. In conclusion, the results of the present study showed that, when low milk producing primiparous cows are concerned, no significant differences in BW loss, milk yield, EB and leptin and NEFA plasma levels between the cows with and without resumption of ovarian activity within 7 weeks post partum were seen. However, significantly higher IGF-I levels in the first two weeks after calving were found in cows with post partum ovarian activity resumption, highlighting the important role of IGF-I as sensitive signal between metabolism and reproduction.     

Fluctuations in energy-related metabolites during the peri-parturition period in Lori-Bakhtiari ewes

This study describes the fluctuations in serum energy-related metabolites during a period of 2 weeks before, to 2 weeks after parturition in Lori-Bakhtiari ewes. The effect of parity was also studied. Blood profiles were determined in 60 healthy pregnant ewes with single (n = 30) and twin (n = 30) lambings. Blood was collected from each ewe on days 14 and 7 prepartum, and days 7 and 14 postpartum to determine the serum non-esterified fatty acid (NEFA), β-hydroxybutyrate (BHBA), glucose, cholesterol, blood urea nitrogen (BUN) and calcium (Ca) levels. The age of the ewes had no significant effect on the energy metabolism indicators. Serum NEFA, BHBA, glucose, BUN and calcium concentrations recorded peak levels 7 days before parturition. However, NEFA and BHBA recorded significant changes (P < 0.05) during the peri-parturition period. All metabolites changed significantly in ewes carrying twin-bearing ewes, compared to single-bearing ewes. Serum BHBA concentrations recorded positive correlations with the serum NEFA (P < 0.01) and cholesterol (P < 0.05), while blood glucose had negative correlations (P < 0.01) with NEFA, BHBA and Ca. Blood NEFA and BHBA recorded positive correlations (P < 0.05) with the BUN levels and negative correlations (P < 0.05) with Ca. The results showed that blood NEFA and BHBA levels are sensitive indicators of the energy balance during the peri-parturition period in ewes.     

Postpartum reproductive function: association with energy,metabolic and endocrine status in high yielding dairy cows

This study evaluated the effect of metabolic, endocrine and energy status on onset of ovarian cycle, days open (DO), and conception at first service in 90 multiparous Holstein cows, housed at a research farm. Dry matter intake, milk yield and body weight were measured daily from Week 2 antepartum (a.p.) to Week 20 postpartum (p.p.). Milk composition was determined four times per week and milk acetone was measured weekly. Blood samples for the determination of glucose, non-esterified fatty acids, cholesterol, creatinine, albumin, urea, beta-hydroxybutyrate, leptin, insulin, insulin-like growth factor-1, growth hormone, 3,5,3'-triiodothyronine (T(3)), and thyroxine (T(4)) were taken 2 weeks a.p., in Weeks 1-16, and 20 p.p. between 7:30 and 9:00 h. The onset of ovarian cycle was specified by weekly gynecological examination and by skim milk progesterone determination by radioimmunoassay (twice per week). Energy balance (EB) traits were calculated and expressed as accumulated negative EB from calving to EB equilibrium, EB nadir (EBN), rate of EB recovery after EBN (EBR), and time from calving to EBN and to EB equilibrium, respectively. The onset of ovarian cycle p.p. was not related to EB. However, a low degree of EBN and a fast EBR were associated with fewer DO, and EB at first service was positively related to conception. High plasma levels of T(3) and T(4) p.p. were associated with an early start of ovarian cycle, and high concentrations of glucose and cholesterol with a short calving to conception interval. Conception at first service was positively related to EB at first service and progesterone concentration 10-13 days after first service. In conclusion, thyroid hormones may play an important role in resumption of ovarian cyclicity p.p., and a good energy status enhances the chance of conception at first service and shortens DO.     

Effects of pituitary-derived bovine growth hormone on production parameters and biokinetics of key metabolites in lactating dairy cows at peak and mid-lactation

Changes in production parameters and metabolite biokinetics induced by treatment with pituitary-derived bovine growth hormone (bGH) were monitored at peak (c. 40 days) and mid-lactation (c. 130 days) in dairy cows. During treatment with bGH milk production increased by 6 and 14% at peak and mid-lactation respectively. At peak lactation the content of milk fat tended to increase, whereas milk protein tended to decrease and milk lactose decreased significantly. Yield of milk fat increased, but there was no change in the yield of milk protein and lactose. The content of milk fat tended to increase at mid-lactation. Milk protein decreased and there was no change in milk lactose. Yields of milk fat and lactose but not protein increased. Growth hormone exerted metabolic effects which differed with stage of lactation. At peak lactation plasma glucose concentration and its irreversible loss increased, plasma urea and acetate were unchanged and their irreversible losses tended to increase. No change was measured for plasma non-esterified fatty acids (NEFA) and the irreversible loss of NEFA decreased. At mid-lactation plasma concentrations of glucose and NEFA were increased, plasma urea decreased and acetate and 3-hydroxybutyrate tended to increase. Irreversible losses of NEFA increased, urea tended to decrease and acetate and glucose remained essentially constant. The results show that exogenous pituitary bGH exerts metabolic effects which result in the supply of increased nutrients to support milk synthesis. The metabolic effects differ with the stage of lactation, reflecting differences in physiological and/or nutritional state.     

Metabolic and endocrine responses to short-term nutrient imbalances in the feed ration of mid-lactation dairy cows

Short-term imbalances of dietary nutrients occur during natural fluctuations in roughage quality (e.g. on pasture) or temporal shortages of supplementary feed components. In contrast to a deficiency, macronutrients (i.e. carbohydrates, proteins, lipids) beyond the adequate supply with other nutrients may, for instance, alter milk composition, increase BW or result in a greater excretion of nitrogen. Especially dairy cows with a moderate performance, in mid- or late lactation, or in extensive farming systems may be exposed to imbalanced rations. A better understanding of metabolic and endocrine responses depending on macronutrient supply may help to precisely feed dairy cows. The present study investigated short-term metabolic and endocrine responses to different levels of concentrates formulated to particularly provide one major macronutrient source (carbohydrates, proteins or lipids). Based on parity number, lactational stage, milk yield and BW, nine mid-lactating cows (211 ± 19 days in milk) were grouped into three blocks of three animals each. Concentrates (aminogenic: rich in CP and nitrogen sources; glucogenic: high content of carbohydrates and glucogenic precursors; lipogenic: high lipid content) were fed in addition to hay in a factorial arrangement at increasing levels from 2.5 to 7.5 kg/d during 9 d. Milk yield, BW and feed intake were recorded daily. Blood and milk were sampled every 3 d at the end of each concentrate level. Milk fat, protein, lactose and urea contents were determined. In blood, concentrations of various metabolites, endocrine factors and enzyme activities (e.g. glucose, non-esterified fatty acids (NEFAs), β-hydroxybutyrate, urea, cholesterol, triglycerides, insulin, glucagon, aspartate aminotransferase (ASAT), gamma-glutamyltransferase (GGT) and glutamate dehydrogenase activity (GLDH)) were measured. Milk yield, milk composition and BW were not affected by type and level of concentrates. Feed intake increased in cows with greater amounts of the aminogenic and lipogenic concentrate compared with the glucogenic concentrate. Milk and plasma urea concentrations were elevated in the aminogenic and to a lesser extent in the lipogenic treatment compared with the glucogenic treatment. Glucose concentrations in plasma were not affected by treatments, whereas insulin and glucagon increased, and NEFA concentrations decreased only in cows fed 7.5 kg/d aminogenic concentrate compared with the glucogenic and lipogenic treatment. Activities of ASAT, GGT and GLDH as well as the total antioxidant capacity were not affected by diets. In conclusion, immediate metabolic and endocrine responses were observed due to the short-term dietary changes. Particularly, a surplus of nitrogen supply via the aminogenic diet affected metabolic responses and stimulated insulin and glucagon secretion.     

Über bakteriostatische Effekte der Darmschleimhaut von Küken mit und ohne Zulage verschiedener Wachstumsstimulatoren zur Nahrung

The supplementation of conjugated linoleic acids (CLA) to the rations of dairy cows represents an opportunity to reduce the content of milk fat. Therefore, CLA have the potential beneficial effect of reducing energy requirements of the early lactating cow. The present study aimed at the examination of long-term and post-treatment effects of dietary CLA intake on performance, variables of energy metabolism-like plasma levels of non esterified fatty acids (NEFA) and ß-hydroxybutyrate (BHB), and fatty acid profile in milk fat. Forty-six pregnant German Holstein cows were assigned to one of three dietary treatments: (1) 100 g/d of control fat supplement (CON), (2) 50 g/d of control fat supplement and 50 g/d of CLA supplement (CLA-1) and (3) 100 g/d of CLA supplement (CLA-2). The lipid-encapsulated CLA supplement consisted of approximately 10% of trans-10, cis-12 CLA and cis-9, trans-11 CLA each. The experiment started 1 d after calving and continued for about 38 weeks, divided into a supplementation (26 weeks) and a depletion period (12 weeks). Over the first 7 weeks of treatment, 11 and 16% reductions in dry matter intake compared to control were observed for the cows fed CLA-1 and CLA-2 supplements respectively. Consequently, the calculated energy balance for these two CLA groups was lower compared to the control. Plasma levels of NEFA and BHB remained unaffected. Later in lactation the highest CLA supplementation resulted in a reduction of milk fat content of 0.7%. However, no reduction in milk fat yield, and accordingly no milk fat depression (MFD), could be shown. The trans-10, cis-12 CLA in milk fat increased with increasing dietary CLA supplementation in a dose-dependent manner. The proportion of C₁₆ in milk fat was decreased by the highest CLA supplementation. With the exception of an increase in plasma glucose level in the CLA-2 group, no post-treatment effects were observed. Overall, under the conditions of the present study no improvement in the calculated energy balance by CLA supplementation could be shown for the entire evaluation period.     

A comparison of energy balance and metabolic profiles of the New Zealand and North American strains of Holstein Friesian dairy cow

The milk production, energy balance (EB), endocrine and metabolite profiles of 10 New Zealand Holstein Friesian (NZ) cows and 10 North American Holstein Friesian (NA) cows were compared. The NA cows had greater peak milk yields and total lactation milk yields (7387 v. 6208 kg; s.e.d. = 359), lower milk fat and similar protein concentrations compared with the NZ cows. Body weight (BW) was greater for NA cows compared with NZ cows throughout lactation (596 v. 544 kg; s.e.d. = 15.5), while body condition score (BCS) tended to be lower. The NA strain tended to have greater dry matter intake (DMI) (17.2 v. 15.7 kg/day; s.e.d. = 0.78) for week 1 to 20 of lactation, though DMI as a proportion of metabolic BW was similar for both strains. No differences were observed between the strains in the timing and magnitude of the EB nadir, interval to neutral EB, or mean daily EB for week 1 to 20 of lactation. Plasma concentrations of glucose and insulin were greater for NA cows during the transition period (day 14 pre partum to day 28 post partum). Plasma IGF-I concentrations were similar for the strains at this time, but NZ cows had greater plasma IGF-I concentration from day 29 to day 100 of lactation, despite similar calculated EB. In conclusion, the results of this study do not support the premise that the NZ strain has a more favourable metabolic status during the transition period. The results, however, indicate that NZ cows begin to partition nutrients towards body reserves during mid-lactation, whereas NA cows continue to partition nutrients to milk production.     

Characterization of gluconeogenesis in hepatocytes isolated from the American eel,Anguilla rostrata LeSueur,

Summary Isolated hepatocyte preparations from fed immature American eels,Anguilla rostrata Le Sueur, were used to study gluconeogenic, lipogenic, glycogenic and oxidative rates of radioactively labelled lactate, glycerol, alanine and aspartate. Eel hepatocytes maintain membrane integrity and energy charge during a 2 h incubation period and are considered a viable preparation for studying fish liver metabolism.Incubating eel hepatocytes with 10 mM substrates, the following results were obtained: glycerol, alanine and lactate, in that order, were effective gluconeogenic substrates; these three substrates reduced glucose release from glycogen stores, while aspartate had no such effect; lactate, alanine and aspartate led to high rates of glycerol production, with subsequent incorporation into lipid; incorporation into glycogen was low from all substrates; and, alanine oxidation was seven times higher than that observed with other substrates.When eel hepatocytes were incubated with low or physiological substrate concentrations gluconeogenic rates from lactate were twice those from alanine; rates from aspartate were very low. Glucagon stimulated lactate gluconeogenesis, but not amino acid gluconeogenesis, and had no significant effect on glycogenolysis. Cortisol increased gluconeogenic rates from 1 mM lactate.Thus, in the presence of adequate substrate, eel liver gluconeogenesis is preferentially stimulated relative to glycogenolysis to produce plasma glucose. These data support three important roles for gluconeogenesis: the recycling of muscle lactate, the synthesis of glucose from dietary amino acids to supplement glucose levels, and the production of glycerol for lipogenesis.This work was supported from operating grants to TWM from the National Research Council of Canada (A6944)     

Effects of propylene glycol drenching on energy balance, plasma glucose, plasma insulin, ovarian function and conception in dairy cows

We postulated that daily drenching of propylene glycol to cows in early lactation would increase plasma glucose and insulin concentrations and improve fertility in postpartum cows. Thirty-six Holstein cows were assigned to treatment or control groups. Each treatment cow was given 500 ml of propylene glycol by drenching daily from 7 to 42 days of lactation. Blood samples for glucose, insulin, nonesterified fatty acids (NEFA), and plasma urea N were collected at 0, 30, and 90 min postdrenching once weekly during 1-6 weeks. Blood samples were collected for progesterone analysis and cows were palpated three times per week until 11 weeks to assess ovarian status. Propylene glycol did not affect dry matter intake (DMI), milk yield or energy balance in treatment cows. After drenching, propylene glycol increased (P<0.01) plasma glucose and insulin and decreased (P<0.01) NEFA; plasma urea N of the treatment group tended (P=0.07) to be higher than that of the control group through 90 min. Days to first service, days open, and services per conception were not different between groups. Conception rates to first insemination were 33% in the control group and 57% in treated cows, but these were not significantly different. First ovulation of treatment cows occurred earlier than that of control cows (32.3 versus 44.5 days, P=0.06) and the length of the first luteal phase was longer in treated cows (13.1 versus 7.3 days, P<0.05). These data are consistent with the hypothesis that insulin is important for normal ovarian function. During negative energy balance, treatment with propylene glycol, which induced small increases in plasma concentrations of insulin, prevented the short luteal phase characteristic of the first estrous cycle in control cows.     

Effects of live weight adjusted feeding strategy on plasma indicators of energy balance in Holstein cows managed for extended lactation

In early lactation, most of the dairy cows are in negative energy balance; the extent and duration depend in part on the feeding strategy. Previous studies showed an increased lactation milk yield by use of a live weight (LW) adjusted feeding strategy with a high energy diet before and a reduced energy diet after LW nadir compared with a standard diet throughout lactation. The objective of the present study was to examine how such an individualized feeding strategy affects plasma indicators of energy status. It was hypothesized that an energy-enriched diet until LW nadir will reduce the severity of the negative energy balance, and that the reduction in diet energy concentration from LW nadir will extend the negative energy balance period further. Sixty-two Holstein cows (30% first parity) were managed for 16 months extended lactation and randomly allocated to one of two feeding strategies at calving. Two partially mixed rations were used, one with a high energy density (HD) and a 50 : 50 forage : concentrate ratio, and one with a lower energy density (LD, control diet) and a 60 : 40 forage : concentrate ratio. Half of the cows were offered the HD diet until they reached at least 42 days in milk and a LW gain⩾0 kg/day based on a 5-days LW average, and were then shifted to the LD diet (strategy HD-LD). The other half of the cows were offered the LD diet throughout lactation (control strategy LD-LD). Weekly blood samples were drawn for analysis of plasma metabolites and hormones. Before the shift in diet, the HD-LD cows had higher glucose and lower beta-hydroxybutyrate and non-esterified fatty acids (NEFA) concentrations than the LD-LD cows. After the shift until 36 weeks after calving, plasma NEFA was higher in HD-LD than LD-LD cows. Insulin and insulin-like growth factor-1 were not affected by the feeding strategy. To conclude, in early lactation, the energy-enriched diet reduced the negative energy balance. Plasma NEFA was higher in HD-LD than LD-LD cows from diet shift until 36 weeks after calving, indicating a carry-over effect of the early lactation HD diet to late lactation metabolism.     

Effect of peripartum dietary energy supplementation of dairy cows on metabolites, liver function and reproductive variables

Multiparous Holstein cows (n=58) were used to study the effects of peripartum dietary supplementation on metabolic status, liver function and reproduction variables. Diets for cows were as follows: (a) no supplementation (CTL), (b) prilled fatty acids as 1.9% of DM (PrFA), (c) calcium salts of long chain n-6 fatty acids as 2.24% of DM (CaLFA) or (d) daily topdressing with 769 g of 65% propylene glycol (PGLY). Supplements were fed during the last 21 days before expected calving except for PGLY that continued until 21 days after parturition. Ovarian activity was monitored by transrectal ultrasonography and days to first ovulation were recorded. Liver biopsies were obtained on day 8 and 21 postpartum and analyzed for triglyceride content and mRNA expression of pyruvate carboxylase, cytosolic phosphoenolpyruvate carboxykinase, carnitine palmytoyltransferase 1A, and peroxisome proliferator-activated receptor-alpha. At 71 days following parturition, stage of ovarian cycles was synchronized and at day15 of the cycle oxytocin was injected i.v., blood samples were obtained at frequent intervals, and analyzed for 13,14 dihydro, 15-keto PGF(2alpha) (PGFM). Milk production and milk components were not different among treatment groups. Cows in PGLY gained body condition score (BCS) prepartum and net energy balance prepartum tended to be greater, but was not different postpartum from other groups. PGLY supplementation increased plasma insulin concentration prepartum, but not during the postpartum period. No significant differences were observed in plasma concentrations of glucose, NEFA, and insulin-like growth factor or hepatic triglyceride content, but all supplements tended to decrease beta hydroxybutyrate postpartum compared to CTL cows. Abundance of mRNA of gluconeogenic and lipid oxidation genes was not different among treatment groups. Days to first ovulation and uterine PGF(2alpha) production in response to an oxytocin treatment were not significantly different among treatment groups. Peripartum supplementation did not result in the substantial improvement of metabolic profile in early lactation nor significantly affect days to first ovulation and PGFM response to an oxytocin treatment.     

Body Condition,Energy Balance and Immune Status of Periparturient Murrah Buffaloes (Bubalus bubalis) Supplemented with Inorganic Chromium

Periparturient Murrah buffaloes were used to determine whether body condition, energy balance and immune status are affected by inorganic Cr supplementation. Twenty-four Murrah buffaloes were blocked into four groups having six animals in each group and fed for 60 days pre-partum to 150 days post-partum. Feeding regimen was same in all the groups except that these were supplemented with 0.0, 0.5, 1.0 and 1.5 of Cr per kilogram of dry matter (DM) in the four respective groups. Buffaloes were weighed at fortnightly intervals. Blood samples were collected from the jugular vein at days ?60, ?30, ?15, ?7, 0, 7, 15, 30, 60, 90, 120 and 150 of experimental feeding for the estimation of non-esterified fatty acid (NEFA), beta-hydroxybutyric acid (BHBA), Cr level, lymphocyte proliferation, neutrophil phagocytic activity, plasma total immunoglobulin (TIg), immunoglobulin G (IgG) and cortisol levels. Results revealed that with approaching parturition, dry matter intake (DMI), immune response and plasma Cr level decreased (P?NEFA and BHBA concentrations showed increasing (P?P?NEFA and BHBA concentrations. The results of present findings indicated that dietary inorganic Cr supplementation reduced lipid mobilization and improved immune response in periparturient buffaloes.     

Relationships among milk progesterone,concentrate allocation,energy balance,milk yield and conception rate in Norwegian cattle

Relationships among milk progesterone, concentrate allocation, energy balance (EB), milk yield and conception rate were studied in 146 lactations in 94 moderate yielding cows. All animals were of the dual purpose breed Norwegian cattle, and were monitored through their first and second lactations. The cows were assigned three different concentrate allocations and had free access to grass silage. Energy balance was estimated by subtracting energy required for maintenance and lactation from energy intake. Milk progesterone concentration was determined three times weekly from calving until pregnancy. The cumulative progesterone concentration was calculated as area under the progesterone curve for the first three luteal phases postpartum. The conception rate increased linearly by rising milk progesterone for values of cumulative progesterone in the lowest third of the range, whereas the likelihood of conception did not differ between milk progesterone concentrations within the upper two-thirds. This implies that the progesterone values were below a threshold value for optimal reproductive success in one-third of the services performed in this study. Milk progesterone concentrations during the third luteal phase postpartum were low when the high-energy diet was fed. Negative EB was associated with reduced values for milk progesterone during the third luteal phase in second parity cows. Likewise, milk yield was inversely related to progesterone levels during both the first and third luteal phases postpartum in second parity cows. Energy balance was higher and milk yield lower during peak lactation among second parity cows that conceived compared to cows that remained open after the first artificial insemination. The present study have demonstrated an association between likelihood of conception and the energy coverage in Norwegian cattle. This relationship is possibly mediated through progesterone deficiency.     

Non-esterified long-chain fatty acid metabolism in fed sheep at rest and during exercise

The role of circulating, non-esterified, long-chain fatty acids (NEFA) as a source of energy for the whole animal and skeletal muscle was investigated in fed non-pregnant sheep at rest and during exercise. Infusion of tracer quantities of [1-14C]oleic or [1-14C]stearic acid was combined with the use of arteriovenous difference studies on fed sheep at rest or during a 2 h period of exercise on a belt treadmill moving at 4.5 km h-1. At rest all parameters of NEFA metabolism indicated a minimal role for oxidation. Thus the concentration in plasma (0.07 +/- 0.01 mmol l-1), entry rate (0.08 +/- 0.02 mmol h-1 kg-1 body wt), contribution to whole animal oxidation (1.2 +/- 0.3%) and utilization of NEFA by skeletal muscle (0.046 +/- 0.008 mmol h-1 kg-1 muscle) were all low. Exercise prompted a shift to lipolysis and accordingly the above parameters increased markedly some 13-24-fold. The circulating concentration of ketone bodies showed only a small increase during exercise and consequently the role of ketone bodies as an energy source during exercise was minimal. Glucose utilization by skeletal muscle was considerable in animals at rest and it represented the most significant potential fuel of skeletal muscle. Exercise resulted in a sustained increase of 3-4-fold in the utilization of glucose by skeletal muscle. Thus the traditional view that NEFA and not glucose is a predominant fuel of skeletal muscle of fed sheep should be appraised.     

A study relating the composition of follicular fluid and blood plasma from individual Holstein dairy cows to the in vitro developmental competence of pooled abattoir-derived oocytes

The fertility of high-performance (high milk yield) dairy breeds such as the Holstein within the Australian dairy herd has been on the decline for the past two decades. The 12-month calving interval for pasture-based farming practices results in oocyte maturation coinciding with peak lactation, periods of negative energy balance, and energy partitioning for lactation, causing energy deficiency in some organ systems, including the reproductive system. Oocyte developmental competence (the ability to undergo successful fertilization, embryo development, and establishment of pregnancy) is intrinsically linked with the composition of follicular fluid (FF). The aim of this study was to determine if there was a relationship between the fat and carbohydrate levels in plasma and FF and the ability to support in vitro oocyte maturation (IVM). Plasma and FF were collected in vivo from eight Holstein cows between 52 and 151 days post-partum. Plasma glucose trended (P = 0.072) higher and triglyceride levels were significantly higher than in FF (P < 0.05), but there were no relationships between FF and plasma composition. Glucose FF concentration was negatively related to follicular lactate and nonesterified fatty acid (NEFA) levels and days post-partum. Conversely, FF triglyceride concentrations were positively related to FF NEFA levels and negatively related to milk fat and protein composition. Abattoir-derived cumulus–oocyte complexes were cultured in either 50% FF (FF-IVM) or 50% plasma (plasma-IVM), with on-time embryo development then assessed. Although there were no differences between animals, the blastocyst rates after FF-IVM were negatively related to plasma glucose and days post-partum and positively related to body condition score and plasma NEFA levels. In comparison to the previous studies, total NEFA levels in FF were not related to animal parameters and did not influence oocyte developmental competence in vitro. Results from this study suggest that days post-partum and body condition score influence carbohydrate metabolism within the follicular environment, and this may be attributed to the pasture-based feed system applied in the Australian dairy industry.