Effect of calcium soaps of fatty acids and administration of somatotropin in early lactation on productive and reproductive performance of high producing dairy cows

The effect of supplementing rumen undegradable unsaturated fatty acids on marbling in early-weaned steers

The objective of this study was to determine if supplementation with a rumen undegradable unsaturated fatty acids (FA) source improved marbling deposition in early-weaned steers. All steers (Angus, = 23; Angus × Hereford, = 24) were weaned at 150 ± 5 d of age. Steers were blocked by BW and breed and then randomly assigned to either control (CON; average 1.5 kg of corn gluten feed [CGF], = 23) or isocaloric supplementation containing a rumen undegradable fat source (RUF; 200 g of Megalac-R added to an average of 1.06 kg of CGF, = 24) offered 5 d/wk for 110 d. All steers had ad libitum access to pastures throughout treatment and received supplements individually. Steer BW and blood samples were collected at 0, 55, and 110 d of supplementation, and real-time ultrasound measurements were collected at d 110. Following treatment, steers were transported to Oklahoma State University for finishing and subsequent harvesting at a commercial plant. All data were analyzed using the PROC MIXED procedure of SAS either as repeated measures or ANOVA depending on parameters. There were no significant changes in BW from the beginning of treatment to harvest due to treatment. Ultrasound data showed that RUF steers tended ( = 0.08) to have more i.m. fat than CON at d 110. Serum concentrations of FA showed a treatment × day interaction ( < 0.02) for 16:0, 18:0, 18:1-9, 18:2, 20:4, and total FA. These specific FA concentrations slightly increased in CON steers, but there was a more pronounced increase in the concentration of these FA across the supplementation period in RUF steers. Serum triglyceride and cholesterol concentrations were increased ( < 0.01) on d 55 and 110 in RUF steers compared with those in CON steers. Serum leptin concentration in RUF steers was greater ( < 0.01) than CON steers at d 110. After harvest, RUF carcasses had greater ( = 0.01) marbling scores than those of CON carcasses. All other carcass measures were similar between treatments. The percentage of total lipids was increased ( = 0.011) in steaks from RUF compared to CON. There was a decrease ( < 0.05) in adipocyte diameter in i.m. fat depot of RUF steers compared to CON. There was also a tendency ( = 0.06) for RUF steers to have a greater percentage of 20 to 30 μm adipocytes in their i.m. depot than CON steers. This study indicates that supplementation of unsaturated FA can positively impact marbling deposition in early-weaned steers without impacting other carcass measures.

Effects of dry period length and dietary energy source on milk yield, energy balance, and metabolic status of dairy cows over 2 consecutive years: Effects in the second year

The objective of the current study was to evaluate the effect of dry period (DP) length on milk yield, energy balance (EB), and metabolic status in cows fed a lipogenic or glucogenic diet in the second year after implementation of DP and dietary treatments. Holstein-Friesian dairy cows (n=167) were assigned randomly to 1 of 3 DP lengths (0, 30, or 60d) and 1 of 2 early lactation diets (glucogenic or lipogenic) for 2 consecutive years. Results of the first year were reported previously. In the second year, 19 cows in the 0-d DP group were attributed to a new group (0→67d DP) because these cows had a milk yield of <4kg/d at least 30d before expected calving date and were dried off. Milk yield was recorded and EB was calculated from wk -8 to 9 relative to calving. Blood samples were taken weekly from wk -3 to 8 relative to calving. Liver samples were taken in wk -2, 2, and 4 relative to calving. At the onset of lactation, cows with a 0-d or 0→67-d DP had greater body condition score (BCS) than cows with a 60-d DP. During the first 9wk, cows with a 0- or 30-d DP produced 5.0 and 4.3kg less milk per day, respectively, but had similar EB compared with cows with a 60-d DP. Cows with a 0- or 30-d DP produced additional milk precalving, which could compensate milk yield losses in the first 9wk postcalving. Cows with a 0-d DP did not have milk yield losses or improve EB in the second year as much as in the first year. Cows with a 0-d DP had greater plasma insulin and insulin-like growth factor-I (IGF-I) and lower liver triacylglycerol concentrations than cows with other DP lengths. Cows with a 0→67-d DP had lower EB, and greater plasma free fatty acids (FFA) and β-hydroxybutyrate (BHB) concentrations than cows with other DP lengths. Feeding a glucogenic diet increased plasma glucose, IGF-I, and insulin concentrations, and decreased plasma FFA, BHB, and urea concentrations compared with a lipogenic diet, independent of DP length. In conclusion, omitting the DP or feeding a glucogenic diet improved metabolic status in early lactation of the second year after implementation of DP length and dietary treatments, although effects of omitting the DP were less pronounced in the second year than in the first year. The less pronounced improvement of EB in the second year was related to the high BCS at the onset of lactation and reduced milk yield losses in cows with a 0-d DP.

Effects of recombinant bovine somatotropin during the periparturient period on innate and adaptive immune responses, systemic inflammation, and metabolism of dairy cows

The aim of this experiment was to determine effects of treating peripartum dairy cows with body condition score ≥3.75 with recombinant bovine somatotropin (rbST) on immune, inflammatory, and metabolic responses. Holstein cows (253±1d of gestation) were assigned randomly to 1 of 3 treatments: untreated control (n=53), rbST87.5 (n=56; 87.5mg of rbST), and rbST125 (n=57; 125mg of rbST). Cows in the rbST87.5 and rbST125 treatments received rbST weekly from -21 to 28d relative to calving. Growth hormone, insulin-like growth factor 1, haptoglobin, tumor necrosis factor α, nonesterified fatty acids, β-hydroxybutyrate, glucose, and cortisol concentrations were determined weekly from -21 to 21d relative to calving. Blood sampled weekly from -14 to 21d relative to calving was used for hemogram and polymorphonuclear leukocyte (PMNL) expression of adhesion molecules, phagocytosis, and oxidative burst. Cows were vaccinated with ovalbumin at -21, -7, and 7d relative to calving, and blood was collected weekly from -21 to 21d relative to calving to determine IgG anti-ovalbumin concentrations. A subsample of cows had liver biopsied -21, -7, and 7d relative to calving to determine total lipids, triglycerides, and glycogen content. Growth hormone concentrations prepartum (control=11.0±1.2, rbST87.5=14.1±1.2, rbST125=15.1±1.3ng/mL) and postpartum (control=14.4±1.1, rbST87.5=17.8±1.2, rbST125=21.8±1.1ng/mL) were highest for rbST125 cows. Cows treated with rbST had higher insulin-like growth factor 1 concentrations than control cows (control=110.5±4.5, rbST87.5=126.2±4.5, rbST125=127.2±4.5ng/mL) only prepartum. Intensity of L-selectin expression was higher for rbST125 than for control and rbST87.5 cows [control=3,590±270, rbST87.5=3,279±271, rbST125=4,371±279 geometric mean fluorescence intensity (GMFI)] in the prepartum period. The PMNL intensities of phagocytosis (control=3,131±130, rbST87.5=3,391±133, rbST125=3,673±137 GMFI) and oxidative burst (control=9,588±746, rbST87.5=11,238±761, rbST125=12,724±781 GMFI) were higher for rbST125 cows than for control cows during the prepartum period. Concentrations of serum IgG anti-ovalbumin tended to be higher for rbST125 cows than for control cows (control=0.75±0.11, rbST87.5=0.94±0.10, rbST125=1.11±0.11 optical density) in the prepartum period. Haptoglobin concentration was significantly reduced 7d postpartum for rbST125 treatment compared with control and rbST87.5 treatments (control=2.74±0.28, rbST87.5=2.81±0.28, rbST125=1.87±0.28 optical density). Although treatment tended to affect postpartum β-hydroxybutyrate (control=747.5±40.2, rbST87.5=753.2±40.1, rbST125=648.8±39.7 µmol/L), it did not affect liver contents of total lipids, triglycerides, or glycogen. Incidence of metritis among rbST125 cows was reduced compared with that in control cows (control=23.1, rbST87.5=18.0, rbST125=7.8%). Treatment of dairy cows with 125mg of rbST improved innate immune responses and IgG concentration, with limited effects on metabolism.

Effect of a calcium soap of fatty acids on reproductive characteristics and lactation performance of fat-tailed sheep

Experiments were carried out to study the effect of feeding Megalac, calcium soaps of fatty acids (protected fat), on reproduction and lactation of sheep. In the first experiment, 20 Ghezel and 20 Mehraban cyclic fertile ewes (4-5 years old) were randomly allotted to 4 groups. The control group was fed with a balanced ration and the other groups received the same diet as well as a daily allowance of 40 g non-protected fat (NP), 40 g protected fat (LP), or 80 g (HP) protected fat. The ewes were fed with their respective rations for one cycle length. Blood samples were collected and analyzed for progesterone (P4), cholesterol (CHOL), High Density Lipoproteins (HDL), Low Density Lipoproteins (LDL) and triacylglycerols (TG). The ewes were slaughtered on their next estrous period and the size and number of follicles in ovaries were recorded. There were no significant effects of feeding fat on ovarian weights, cycle length and follicular numbers in each class, or on the size of the largest follicle. Serum concentrations of P4, CHOL, TG and HDL were greater for HP ewes as compared with the control ewes (p<0.05). In the second experiment, effects on lactation and lamb performance of feeding protected fat during mating, late gestation and early lactation were studied in Mehraban ewes. Milk and fat yields on day 25 of lactation were significantly increased by feeding protected fat. Protected fat resulted in lower weight loss in ewes and a higher lamb birth weight. Average daily weight gain of lambs from birth to day 60 and the weaning weight of lambs were increased by feeding protected fat (p<0.05). In conclusion, calcium soaps of fatty acids increased serum P4 between days 10 to 14 of the cycle which may be beneficial to early pregnancy maintenance. Protected fat seemed to have a beneficial effect on milk yield, fat yield, lamb daily gain, lamb birth weight and ewe weight loss.

Effect of Glucogenic vs. Lipogenic Diets on Energy Balance, Blood Metabolites, and Reproduction in Primiparous and Multiparous Dairy Cows in Early Lactation

Increasing the availability of glucogenic nutrients relative to lipogenic nutrients has been hypothesized to decrease the production of milk fat, to improve the energy balance (EB), and to decrease the incidence and severity of metabolic and reproductive disorders in dairy cows in early lactation. Therefore, our objective was to evaluate the effects of a glucogenic, lipogenic, or mixed diet on EB, plasma metabolites and metabolic hormones, liver triacylglycerides (TAG), and reproductive variables in high-producing dairy cows in early lactation. Cows (n = 114) were randomly assigned to 1 of 3 diets and were fed either a mainly lipogenic diet, a mainly glucogenic diet, or a mixture of both diets (50:50 dry matter basis) from wk 3 before the expected calving date until 9 wk postpartum. Diets were isocaloric (net energy basis) and equal in intestinal digestible protein. Dry matter intake, net energy intake, milk yield, and milk protein percentage did not differ among diets. Milk lactose percentage was less for cows fed the lipogenic diet. Milk fat percentage was less for multiparous cows fed the glucogenic diet compared with cows fed the mixed or lipogenic diet (3.69 vs. 4.02 vs. 4.22 +/- 0.07%, respectively). The calculated EB was less negative for multiparous cows fed the glucogenic diet compared with cows fed the mixed or lipogenic diet [-33 vs. -125 vs. -89 +/- 21 kJ/(kg(0.75) x d), respectively]. Postpartum, the glucogenic diet decreased plasma nonesterified fatty acids, beta-hydroxybutyrate, and liver TAG concentrations and increased insulin concentration in multiparous cows. The glucogenic diet tended to decrease the number of days until first milk progesterone rise in multiparous cows compared with the mixed or lipogenic diet (20.4 vs. 24.4 vs. 26.4 +/- 2.1 d, respectively). Diet had no effect on any of the above-mentioned variables in primiparous cows, except that milk lactose percentage was greater for primiparous cows fed the glucogenic diet. We concluded that the glucogenic diet was effective in improving the calculated EB and decreasing plasma beta-hydroxybutyrate and liver TAG concentrations, suggesting a reduced risk of metabolic disorders in multiparous dairy cows fed a glucogenic diet.

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.

Role of Peripartum Dietary Propylene Glycol or Protected Fats on Metabolism and Early Postpartum Ovarian Follicles

Eighty multiparous cows were used to test the effects of feeding a supplement containing 55% dry propylene glycol (PGLY), prilled fat (PrFA) containing a low proportion of unsaturated fatty acids (FA), or calcium soaps of long-chain FA (CaLFA) containing a high proportion of unsaturated FA on energy balance (EB), blood metabolites, and early postpartum (PP) ovarian follicles. Dry cows (256 d pregnant) were divided into 6 groups and began the following dietary treatments: 1) control group, fed a dry cow diet and fed a lactating cow diet PP; 2) PGLY group, diet supplemented with 500 g/d per cow of dry PGLY prepartum through 21 d in milk; 3) PrFA:control group, diet supplemented with 230 g/d per cow of PrFA prepartum and fed the control diet PP; 4) PrFA:PrFA group, diet supplemented with 230 g/d per cow of PrFA prepartum through 21 d in milk; 5) CaLFA:control, supplemented with 215 g/d per cow of CaLFA prepartum and fed the control diet PP; 6) CaLFA:CaLFA, supplemented with 215 g/d per cow of CaLFA prepartum through 21 d in milk. Follicular fluid was aspirated from follicles > or = 6 mm on d 12 PP. The daily average calculated EB during the first 21 d in milk was lower in the PrFA:PrFA (-4.16 Mcal/d) and CaLFA:CaLFA (-3.64 Mcal/d) groups than in the control (-1.71 Mcal/d) and PGLY (-2.19 Mcal/d) groups. Postpartum plasma beta-hydroxybutyrate was higher, and insulin concentrations were lower in the PrFA:PrFA (6.2 mg/dL and 126.1 pg/mL, respectively) and CaLFA:CaLFA (7.0 mg/dL and 130.7 pg/mL) groups than in the control (4.5 mg/dL and 274.5 pg/mL) and PGLY (4.3 mg/dL and 272.6 pg/mL) groups, whereas nonesterified FA concentrations were higher only than the control group. Postpartum nonesterified FA were 21% lower and insulin plasma concentrations were 86% higher in the CaLFA:control group as compared with the PrFA:control group. The progesterone concentrations in the follicular fluid of estradiol-active follicles were higher in the CaLFA:CaLFA (200.7 ng/mL) group than in all other groups (57.3 to 92.4 ng/mL), and androstenedione and estradiol concentrations were higher (54.2 and 1,049.1 ng/mL, respectively) than in the PGLY (15.5 and 440.1 ng/mL), PrFA:control (22.6 and 314.1 ng/mL), and CaLFA:control (17.5 and 451.9 ng/mL) groups. In conclusion, supplementation of protected fat during the peripartum period negatively affected the EB status of the cows. Neither fat supplementation nor PGLY influenced the development of ovarian follicles during the early PP period, but feeding fat containing a high ratio of unsaturated FA (CaLFA) increased progesterone concentrations in estradiol-active follicles that were aspirated at 12 d in milk.

Association between seasonal changes in fatty-acid composition, expression of VLDL receptor and bovine sperm quality

Reduced reproductive performance of dairy cows during the summer is often associated with elevated temperature. Semen collected and cryopreserved during the summer may be of low quality and might contribute to the compromised fertility of dairy cows during this season. The present study examined the association between seasonality, semen quality and its potential to survive cryopreservation. A comparison between semen collected during the summer (July to August) and that collected during the winter (November to December) revealed the summer semen to be inferior, as reflected by low motility and high mortality of sperm. Furthermore, samples that were defined as good quality had changes in lipid concentration and fatty-acid composition in both the seminal plasma and cell compartment. In particular, semen collected during the summer had reduced levels of polyunsaturated arachidonic acid (20:4; P<0.05) and decreased levels of linoleic acid (18:2; P<0.05) in the cell compartment; corresponding reductions in cholesterol (P<0.06) and fatty-acid concentrations (P<0.001) were detected in seminal plasma of semen collected during the summer. In addition, we provided the first evidence for the existence of a very-low-density lipoprotein receptor (VLDLr) in bovine sperm, suggesting a mechanism for sperm utilization of extracellular lipids. Interestingly, the expression of VLDLr was three-fold greater in samples collected during the winter than in those collected in the summer (P<0.01) and was negatively associated with saturated fatty-acid concentration (P<0.018) but not with that of cholesterol. An opposite pattern was noted for samples obtained during the summer; mRNA expression of VLDLr was negatively associated with cholesterol concentration (P<0.01) but not with that of saturated fatty acids. Such modifications associated with extracellular lipid utilization and fatty-acid composition might explain, in part, the reduced quality of summer semen.

Summer heat stress alters the mRNA expression of selective-uptake and endocytotic receptors in bovine ovarian cells

Summer heat stress (HS) is a major factor in decreased reproductive performance in high-producing dairy cattle, possibly by affecting the steroidogenic capacity of ovarian follicles and ovarian follicular dynamics. In the present study, mRNA expression of cholesterol receptors was determined in bovine ovarian cells. Two endocytotic receptors (very-low-density lipoprotein receptor (VLDLr) and low-density lipoprotein receptor (LDLr)), and two selective-uptake receptors (scavenger receptor class B type 1 receptor (SRB1) and the lipoprotein-receptor-related protein 8 (LRP8)) were evaluated. Ovarian follicles in four diameter categories were evaluated from cows under non-heat stress (NHS) and HS conditions. As follicle size increased, expression of mRNA in NHS cows increased for the selective-uptake receptors, SRB1 and LRP8, and decreased (P<0.004) for the endocytotic receptors, LDLr and VLDLr. In contrast, in HS cows, mRNA expression did not significantly change (with increasing follicle diameter) for either receptor type. With increasing follicle diameter, cholesterol and fatty acid concentrations in the follicular fluid did not change in HS cows, whereas in NHS cows, cholesterol increased (P<0.008) and fatty acid decreased (P<0.0001). These changes paralleled those in the different lipoprotein fractions in the follicular fluid. In follicles from HS cows, the altered mRNA expression patterns for the endocytotic and selective-uptake receptors caused changes in the regulation of cholesterol supply at critical stages of folliculogenesis, which may play a role in the low turnover rates of ovarian follicles during the summer.

Lipid Transport in the Developing Bovine Follicle: Messenger RNA Expression Increases for Selective Uptake Receptors and Decreases for Endocytosis Receptors

Differences in rates of steroid production and secretion will, eventually, determine the developmental rates of ovarian follicles. The major supply of cholesterol, the precursor for steroid and androgen biosynthesis, to ovarian cells is from circulating lipoproteins via membrane receptors from the low density lipoprotein receptor (LDL) superfamily. This occurs by either endocytosis, which has been described for very low density lipoprotein receptors (VLDLr), for LDL receptors (LDLr), and by the selective uptake pathway described for the scavenger receptor class B type 1 receptor (SRB1) and the recently described ovarian receptor, lipoprotein receptor-related protein 8 (LRP8). In this study, the mRNA expression of these four cholesterol receptors in bovine ovarian cells was determined at different stages of follicular development. In small antral follicles, mRNA expression of the endocytosis receptors was higher than in large antral follicles. Expression of LRP8 mRNA increased linearly with follicular size together with an increase in LDL, VLDL, and cholesterol concentrations in the follicular fluid. SRB1 mRNA expression tended to increase with follicular diameter. Because different mRNA expression patterns were found for the two types of receptor, this may imply different regulation of cholesterol supply at different stages of follicular development. Accumulation of LDL and VLDL particles in the follicular fluid of large antral follicles may enhance cholesterol availability for the intense steroidogenic activity that is essential at these stages.

Low Doses of Bovine Somatotropin During the Transition Period and Early Lactation Improves Milk Yield, Efficiency of Production, and Other Physiological Responses of Holstein Cows

The objectives of this experiment were to determine whether low doses of bovine somatotropin (bST) during the transition period and early lactation period improved dry matter intake (DMI), body weight (BW), or body condition score (BCS); provoked positive changes in concentrations of somatotropin, insulin, insulin-like growth factor-I (IGF-I), glucose, nonesterified fatty acids, and Ca; or improved milk yield (MY) response without obvious adverse effects on health status. Eighty-four multiparous Holstein cows completed treatments arranged in a 2 x 3 x 2 factorial design that included prepartum and postpartum bST, dry period (30 d dry, 30 d dry + estradiol cypionate, and 60 d dry), and prepartum anionic or cationic diets. Biweekly injections of bST began at 21 +/- 3 d before expected calving date through 42 +/- 2 d postpartum (control = 0 vs. bST = 10.2 mg of bST/d; POSILAC). At 56 +/- 2 d in milk, all cows were injected with a full dose of bST (500 mg of bST/14 d; POSILAC). During the prepartum period and during the first 28 d postpartum, no differences in mean BW, BCS, or DMI were detected between the bST treatment group and the control group. During the first 10 wk of lactation, cows in the bST treatment group had greater mean MY and 3.5% fat-corrected milk yield and lower SCC than did cows in the control group. When cows received a full dose of bST, an increase in milk production through wk 21 was maintained better by cows in the bST group. Mean concentrations of somatotropin, IGF-I, and insulin differed during the overall prepartum period (d -21 to -1). During the postpartum period (d 1 to 28), cows in the bST group had greater mean concentrations of somatotropin and IGF-I in plasma. Concentrations of Ca around calving did not differ because of bST treatment. Results suggest that changes in concentrations of blood measures provoked by injections of bST during the transition period and early lactation period resulted in improved metabolic status and production of the cows without apparent positive or negative effects on calving or health.

Number of oocytes obtained from cows by OPU in early, but not late lactation increased with plasma insulin and estradiol concentrations and expression of mRNA of the FSH receptor in granulosa cells

The effects of lactation stage and hormonal profile on the quality and quantity of oocytes and the gonadotrophic sensitivity of granulosa cells (GC) from small antral follicles obtained by sequential aspirations from ovaries of high producing dairy cows were examined. Cows in late lactation (263(+/- 60) days postpartum) and 98(+/- 16) days pregnant in positive energy balance (EB) showed no significant changes in plasma concentrations of estradiol, progesterone, insulin, IGF1 or expression of mRNA of the FSH receptor in GC from small antral follicles during the 49 days experimental period. There were no changes in the number and quality of oocytes obtained from each aspiration. In cows in early lactation (72.8 +/- 6 days postpartum), plasma insulin concentrations increased and were positively correlated with plasma estradiol concentration. Due to the sequential aspirations progesterone blood concentrations were low in early lactation cows. Expression of mRNA of the FSH receptor increased in GC from small antral follicles of early lactation cows together with the number of oocytes obtained with aspiration sessions. No differences were found in morphological quality or function between oocytes obtained from small antral follicles from cows in early or late lactation. In early, but not late lactation, the number of oocytes was correlated with both insulin and E2 plasma concentrations. Improved EB and sensitivity of GC to FSH may be involved in oocyte recruitment in early lactation.

Effect of offering rumen-protected fat supplements on fertility and performance in spring-calving Holstein-Friesian cows

The objective of this study was to evaluate the effect of two different rumen-protected fat supplements, on reproductive performance and milk production, in grass-based spring calving cows. Two hundred and one Holstein-Friesian cows with an average lactation number of 3.6 (20% first lactation, 16% second lactation and 64% third lactation or greater) were grouped into blocks of three on the basis of calving date, lactation number and previous lactation milk yield for cows of second lactation or greater and on the basis of calving date for first lactation animals. From within-blocks individual animals were assigned at random, within 10 days post-calving, to one of the following three treatments: (1) Megalac Plus 3% (MP; 0.4kg/day, containing Ca salt of palm fatty acids and Ca salt of methionine hydroxy analogue), (2) Megapro Gold (MPG; 1.5kg/day, containing Ca salt of palm fatty acids, extracted rapeseed meal and whey permeate), and (3) Control (C; unsupplemented). Cows were supplemented for on average 103 days (range 54-134 days). The average milk yield over the first 12 weeks of lactation was higher (P<0.05) for both fat supplements compared to C and was higher for MP compared to C over the full lactation. Both supplements reduced (P<0.05) milk protein concentration over the first 6 weeks of lactation. MPG increased (P<0.05) conception rate to first service compared to C. Conception rate to first service was similar (P=0.14) on MP compared to C. For pregnancy to second service, C had a higher (P<0.05) conception rate than MP. There were no significant differences between treatments in overall pregnancy rate, services per conception, number of cows served in the first 3 weeks of the breeding season or the 6-weeks in-calf rate. Comparing the combined fat treatments to C resulted in a higher (P<0.05) conception rate to first service for the fat treatments but no significant difference in overall pregnancy rate. In conclusion, fat supplements increased conception rate to first service but did not significantly affect the proportion of cows pregnant at the end of the breeding season.

Responses of Holstein Cows to a Low Dose of Somatotropin (bST) Prepartum and Postpartum

Objectives were to evaluate the effects of a low dose of bovine somatotropin (bST) injected prepartum and postpartum on body condition score (BCS), body weight (BW), and milk yield (MY) in cows as well as somatotropin insulin, insulin-like growth factor-I (IGF-I), glucose, and nonesterified fatty acids (NEFA) in plasma. Holstein cows nearing second or later parities were assigned randomly to control (CON = 98) or bST-treated (TRT = 95) groups. Biweekly injections of bST began 21 +/- 3 d before expected calving and continued through 42 d postpartum (CON vs. TRT; 0 vs. 10.2 mg of bST/ d). From 42 to 100 d postpartum, no cows received bST. During yr 1, somatotropin, IGF-I, insulin, NEFA, and glucose were measured in plasma samples from 82 cows. During yr 2, effects of bST on BCS and BW of 111 cows were evaluated, but no blood samples were collected. Milk yields through 100 d of all 193 cows were analyzed. Prepartum treatment with bST resulted in greater prepartum plasma concentrations of somatotropin, insulin, and numerically greater NEFA but did not affect glucose or IGF-I. Postpartum bST increased mean plasma concentrations of somatotropin and NEFA, but not INS, IGF-I, or glucose. Mean BCS of cows did not differ prepartum, around parturition, or postpartum. Although mean BW did not differ prepartum or around calving, cows receiving bST maintained greater BW postpartum. Cows receiving bST tended to have higher MY (6.6%) in the first 60 d of lactation, but differences did not persist through 100 d, including approximately 40 d when no cows received bST. Number of cows that were culled due to health (CON = 3 vs. TRT = 2) or died (CON = 3 vs. TRT = 1) were not affected by treatment. Low doses of bST in the transition period resulted in higher postpartum BW, quicker recovery of body condition during lactation, and significantly more milk during treatment.

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.

Effect of polyunsaturated fatty acid supplementation on biophysical parameters and chilling sensitivity of ewe oocytes

Fat supplementation in the diet influences reproductive performance of lactating ruminants. Changes in the fat supply alter fatty acid composition and this can affect physical properties of cell membranes. This study examined the effect of rumen bypass polyunsaturated fatty acid (PUFA) supplementation on oocyte quality, chilling sensitivity, and lipid phase transition in oocytes of the sheep. Ewes were fed a diet supplemented with calcium soaps of fish oil for 13 weeks. More follicles and oocytes were found in the ovaries of ewes supplemented with PUFA than in control ewes. The number of high-quality oocytes was higher in ewes fed PUFA than in control ewes (74.3 and 57.0%, P < 0.05, respectively). Evaluation of phospholipid fatty acid composition indicated that PUFA were present in small proportions in oocytes, and eicosapentaenoic acid and docosahexaenoic acid were absent. Supplementation with PUFA increased the proportion of long chain unsaturated fatty acid in the plasma and cumulus cells phospholipids by 7.4 and 12.7%, respectively (P < 0.05). Integrity of oocyte membranes following chilling (16 degrees C, 15 min) was improved by PUFA supplementation increasing from 62.5 to 90.0% (P < 0.05). Due to changes in the oocyte's fatty acid profile, physical properties of the membrane were changed and the midpoint temperature of lipid transition reduced by 11 degrees C. These results suggest that supplementation of rumen bypass PUFA to ruminant diets can change fatty acid composition of follicle components and influence parameters such as number and quality of oocytes and their chilling resistance.

Preovulatory follicular status and diet affect the insulin and glucose content of follicles in high-yielding dairy cows

Insulin and glucose may be limiting factors for ovarian function in dairy cows genetically selected for high milk yield. The effects of nutrition on the intrafollicular content of insulin and glucose were investigated in Israeli Holstein dairy cattle fed a basic total mixed ration and producing 34-39kg of milk daily. In experiment 1, carried out in 11 oestrus-synchronised cows, little variation in insulin concentration was found in plasma sampled during the luteal phase, but high variation was found in plasma sampled during the follicular phase. Therefore, in order to prevent confounding the effects of diet and of phase in cycle in the following experiments, experimental diets were fed during the luteal phase of synchronised oestrus cycles. In experiment 2, designed as Latin-Square, six cows received sequentially diets containing 17.1 (control) or 19.7% of crude protein, using two sources of supplementary protein, i.e. soyabean meal (SBM) and corn gluten meal (CGM), differing in ruminal degradability and leucine content. When dry matter intake was used as covariant, plasma insulin on day 16 was 29.5 and 26.4% higher in cows fed diets containing SBM and CGM than in the control (P<0.05). In experiment 3, 17 cows were individually fed the basic diet and then switched to isoenergetic diets containing SBM (n=5), CGM (n=6) or corn grain (CG, n=6) given from day 10 to 16 of the synchronised oestrus cycle. On the eve of day 16, and in the morning of day 17, they were administered PGF(2alpha) and the content of 26 largest follicles was aspirated by using the transvaginal ovum pick-up technique. Follicles were sorted into two classes (preovulatory and subordinate) according to oestradiol concentration and the progesterone:oestradiol ratio in follicular fluid (FF). Higher concentrations of insulin (0.282 versus 0.127ng/ml, P<0.0001) and of glucose (0.614 versus 0.386g/l, P<0.002), were found in FF from preovulatory follicles. The insulin concentration in the FF of cows fed the CG diet was 26% higher than in their counterparts fed CGM (P<0.04), SBM being intermediate. Dietary effects did not reach significance in subordinate follicles. The finding that preovulatory follicular status is associated with increased intrafollicular insulin and glucose suggests that insulin is involved in follicular maturation. The nutritional effect on intrafollicular glucose and insulin may have practical implications to optimise feeding in dairy cows during phases of the oestrus cycle.

Induction of ovarian cystic follicles in sheep

Cystic follicles are a significant cause of infertility in women, dairy cattle and sheep. Sheep were used as a model to identify factors that may elicit formation of cystic follicles. Insulin resistance and elevated LH activity were tested in overweight ewes because of associations among these factors and the formation of cystic follicles. Sheep were synchronized using a progesterone-releasing pessary and insulin resistance was induced during the synchronization period through administration of bovine somatotropin. Following removal of pessaries follicular growth was stimulated by treatment with eCG or eCG and hCG (PG-600). Follicular growth was monitored via daily transrectal ultrasonography and blood samples were collected for hormonal analyses. Six of 18 ewes had a subnormal or absent preovulatory gonadotropin surge and developed cystic follicles. Neither insulin resistance nor elevated LH activity were associated with formation of cystic follicles. Ewes that developed cystic follicles were heavier (93 +/- 4 kg) than ewes that ovulated (81 +/- 3 kg; P = 0.02). Furthermore, following pessary removal and initiation of daily ultrasonography, ewes that developed cystic follicles lost body weight (-3 +/- 1%), while ovulatory ewes continued to gain body weight (1 +/- 1%; P = 0.005). It is speculated that in heavy ewes metabolic factors associated with acute body weight loss inhibit the positive feedback of estradiol and thereby suppress the preovulatory gonadotropin surge leading to formation of cystic follicles.

Effects of somatotropin and dietary calcium soaps of fatty acids in early lactation on milk production, dry matter intake, and energy balance of high-yielding dairy cows

We allocated 39 high-yielding individually fed cows to three treatments: control, calcium soaps of fatty acids (CSFA) fed at 2.2% dry matter, and 500 mg of Zn-sometribove (bST) injected every 14 d from 10 to 150 d in milk (DIM). Production of fat corrected milk was increased by 3.0 kg/d in the CSFA group and by 5.4 kg/d in the bST group. Energy balance was negative during the first 28 to 34 DIM in control and CSFA cows and during 59 DIM in bST-treated cows; minimum body weight, minimum body condition score, and DMI peak were reached 25-28 d later in the bST group. Dry matter intake (DMI) was significantly increased by bST, and during the first 3 wk of treatment the increase in DMI of the bST cows was 46% more than that of the controls. DMI was significantly correlated throughout the experimental periods with calculated energy expenditure in the control and CSFA groups, but only during 54 DIM in the bST group. Furthermore, commencement of the DMI decrease was correlated with the beginning of the decrease in milk production. Gross feed efficiency was significantly higher in the bST group than in the other groups. We concluded that treating high-yielding cows with bST early in lactation increased milk production at the expense of an extensive period of negative energy balance and body weight and body condition decreases despite an increase in DMI after bST treatment.

Effects of grain processing and bovine somatotropin on metabolism and ovarian activity of dairy cows during early lactation

This study compared the effects of exogenous bovine somatotropin (bST) on the metabolism and ovarian activity of cows fed diets differing in ruminally degradable starch. Twenty-four multiparous and eight primiparous Holstein cows in early lactation were divided into four groups and fed diets containing 39% grain as steam-flaked sorghum or steam-rolled corn with or without bST for 90 d in a 2 x 2 factorial design. Flaked sorghum improved energy status of cows during early lactation, tending to increase plasma glucose and insulin. Administration of bST decreased plasma urea nitrogen and increased nonesterified fatty acids (NEFA). Plasma levels of beta-hydroxybutyrate (BHBA) and hepatic concentrations of triglycerides were not altered by treatments. Temporal changes in plasma glucose, urea nitrogen, NEFA, and BHBA were detected in a quadratic manner and insulin increased linearly with time, but treatments did not affect postpartum changes in these metabolites. There were greater decreases in body weight and net energy balance in cows on bST during the first 7 wk of treatment. Cows receiving bST took longer to reach the nadir of negative energy balance, and bST tended to delay the period to reach a positive energy balance. Follicular populations and incidence of cystic ovaries were not affected by treatments, but cows receiving bST had fewer double ovulations. Flaked sorghum increased plasma progesterone during the early luteal phase of the first two postpartum estrous cycles. Feeding more ruminally degradable starch improved the energy status and luteal activity of cows in early lactation.

The effects of time of disease occurrence, milk yield, and body condition on fertility of dairy cows

The associations between occurrence of diseases, milk yield, and body condition score on conception risk after first artificial insemination (AI) were analyzed in an observational study on a convenience sample of 43 farms participating in a herd health program. Data were taken from 9369 lactations, from 4382 cows inseminated between 20 and 180 d in milk from 1990 to 1996. Two logistic regression models, one containing data from all lactations and a subset containing data from 1762 lactations with body condition scoring, were used to determine pregnancy risk at first AI. The effects of herd deviation in test-day milk yield, body condition score loss, and milk fat to protein ratio changes in early lactation were significant predictors of pregnancy risk, independent of disease; days in milk; farm; and seasonal factors. Three different methods of disease parameterization (incidence rates, binomial classes dependent on the interval in days since last occurrence with respect to AI, and a linear variable weighted for this interval) produced similar results. Metritis, cystic ovarian disease, lameness, and mastitis gave odds ratios for pregnancy risk ranging from 0.35 to 1.15, largely dependent on the interval in days from final disease occurrence to first AI. Displaced abomasum, milk fever, and retained fetal membranes resulted in odds ratios for pregnancy risk of 0.25, 0.85, and 0.55, respectively. These diseases showed little relationship between fertility and the number of days since last occurrence. Results of this study confirm the negative effects of milk yield, body score condition loss, and disease on dairy cow fertility. The effects of some diseases on first service conception were strongly dependent on the interval since last disease occurrence. This was especially valid for clinical mastitis, which has an extremely weak effect on conception if occurring prior to AI and is associated with > 50% reduction in pregnancy risk if occurring in the 3 wk directly after AI.

Effect of calcium soaps of fatty acids and administration of somatotropin on milk production, preovulatory follicular development, and plasma and follicular fluid lipid composition in high yielding dairy cows

The effect of fat and bovine somatotropin (bST) on preovulatory follicular hormones and lipids was evaluated by feeding cows for 150 d from parturition a control diet, a control diet plus 0.55 kg/d of calcium soaps of fatty acids, or a control diet with 500 mg of bST injected every 14 d. Fourteen days after a synchronized or natural estrus, cows were injected with a PGF2 alpha analogue; 48 h later, follicular fluid from all ovarian follicles > 8 mm was aspirated. Cows fed fat or injected with bST produced more milk and milk solids than did control cows, and cows on the bST treatment lost more body condition after calving than did cows on the other treatments. Both treatments changed the proportion of estradiol-active follicles (> 400 ng of estradiol/ml of follicular fluid) and the correlation between follicular fluid estradiol concentration and the total number large follicles per cow. In follicles aspirated between 60 and 90 DIM the percentage of estradiol-active follicles was 67, 40, and 0 for cows on the control, calcium soaps of fatty acids, and bST treatments, respectively. After 90 DIM, no differences existed between treatments in the percentage of estradiol-active follicles. Estradiol concentration in follicular fluid was correlated with DIM at follicle aspiration (r = 0.51). The proportion of oleic acid in free fatty acids in plasma at 50 DIM was lower in control cows and was lower in follicular fluid of estradiol-active follicles. Both calcium soaps of fatty acids and bST had a considerable effect on follicular development and activity and the composition of fatty acids in follicles.

Use of AI technician scores for body condition, uterine tone and uterine discharge in a model with disease and milk production parameters to predict pregnancy risk at first AI in Holstein dairy cows

Technicians recorded body condition score (BCS) and several parameters related to estrus and/or metritis for 1694 first insemination cows on 23 farms. Additional variables for modeling the adjusted odds ratios (OR) for pregnancy were data on disease prior to or within 21 days of AI and test day milk yields. Significant predictors for pregnancy were farm, year and season, BCS, uterine tone, contaminated insemination gun after AI, fat-protein corrected kilograms milk (FPCM), days in milk (DIM), and diseases. Vaginal mucus, ease of cervical passage, and lameness were not significant predictors for pregnancy. Pregnancy risk at AI increased with increasing DIM, reaching a near optimum after 82 days. Lack of uterine tone was associated with a lowered pregnancy risk (OR = 0.69) as was contaminated insemination gun (OR = 0.67), first-parity lactation, FPCM >33 kg (OR = 0.71), BCS 2.5 at AI (OR = 0.65), clinical mastitis (OR = 0.53), cystic ovarian disease (OR = 0.53), and metritis (OR = 0.74). It was concluded that data on BCS and uterine findings, as collected by AI technicians, are significant predictors of AI outcome. Dairy producers and veterinarians should jointly examine the potential costs and value of such AI technician-based data to improve herd fertility.