Dietary manipulations to improve embryonic survival in cattle

High-producing dairy cows are subfertile. Hormonal and metabolic responses associated with homeorrhetic and homeostatic regulatory responses to partition nutrients for lactation, coupled with management, contribute to the reduction in fertility. Systems of reproductive management partially restore herd reproductive performance and provide a basis to access the impact of targeted nutritional strategies to further improve postpartum health and reproduction. Increasing the number of days feeding prepartum diets with a negative dietary cation-anion difference (DCAD), combined with adequate energy, protein, amino acids, and trace/macrominerals, improves the subsequent pregnancy rate. Likewise, supplementation of organic Se in the transition period and lactation improves immune function, uterine health, and subsequent reproductive performance under conditions of Se insufficiency. A basic understanding of the regulatory processes between nutrient partitioning and reproduction has led to the development of dietary strategies that benefit both lactation and reproduction. Postpartum increases in dietary nonstructural carbohydrates (i.e., glucogenic diets) increases ovarian activity in either intensive or extensive systems. Furthermore, sequential feeding of glucogenic-lipogenic diets enhances the proportion of cows pregnant by 120 d of lactation. Fatty acids of the n-6 and n-3 families act as nutraceuticals, altering innate immune responses and subsequent gene expression within the uterus to complement the sequential processes of follicle and embryo development and survival of the embryo and fetus. Selective or sequential feeding of lipogenic diets can benefit reproductive and immunological responses of lactating dairy cows and extensively managed beef cows.     

Colostrum and milk selenium,antioxidative capacity and immune status of dairy cows fed sodium selenite or selenium yeast

Dietary selenium (Se) can be supplemented from organic or inorganic sources and this may affect Se metabolism and functional outcome such as antioxidative status and immune functions in dairy cows. A feeding trial was performed with 16 Holstein-Friesian dairy cows fed with a total mixed ration (0.18 mg Se/kg dry matter (DM)) either without Se supplement (Control, n = 5), or with Se from sodium selenite (Group SeS, n = 5) or Se yeast (Group SeY, n = 6). In Groups SeS and SeY, the Se supplementation amounted to an additional intake of 4 mg Se and 6 mg Se/d during gestation and lactation, respectively. The effect of both Se sources was characterised by milk Se and antioxidant levels, and the phenotyping and functional assessment of phagocytic activity of milk immune cells. Se yeast has been found to increase (p ≤ 0.001) the milk Se and antioxidant levels markedly compared to the control group. The experimental treatment did not affect the immune parameters of the cows. Lymphocyte subpopulations and phagocytosis activity of neutrophilic granulocytes were affected neither by the Se intake nor by the two different dietary supplements. It can be concluded that sodium selenite and Se yeast differ considerably in their effects on antioxidant status in dairy cows. However, the basal dietary Se concentration of 0.18 mg/kg DM seemed to be high enough for the measured immune variables.     

Responses to n-3 fatty acid (LCPUFA) supplementation of gestating gilts,and lactating and weaned sows

Feeding n-3 long-chain polyunsaturated fatty acids (LCPUFA) to gilts or sows has shown different responses to litter growth, pre-weaning mortality and subsequent reproductive performance of the sow. Two hypotheses were tested: (1) that feeding a marine oil-based supplement rich in protected n-3 LCPUFAs to gilts in established gestation would improve the growth performance of their litters; and (2) that continued feeding of the supplement during lactation and after weaning would offset the negative effects of lactational catabolism induced, using an established experimental model involving feed restriction of lactating primiparous sows. A total of 117 primiparous sows were pair-matched at day 60 of gestation by weight, and when possible, litter of origin, and were allocated to be either control sows (CON) fed standard gestation and lactation diets, or treated sows (LCPUFA) fed the standard diets supplemented with 84 g/day of a n-3 LCPUFA rich supplement, from day 60 of first gestation, through a 21-day lactation, and until euthanasia at day 30 of their second gestation. All sows were feed restricted during the last 7 days of lactation to induce catabolism, providing a background challenge against which to determine beneficial effects of n-3 LCPUFA supplementation on subsequent reproduction. In the absence of an effect on litter size or birth weight, n-3 LCPUFA tended to improve piglet BW gain from birth until 34 days after weaning (P = 0.06), while increasing pre-weaning mortality (P = 0.05). It did not affect energy utilization by the sow during lactation, thus not improving the catabolic state of the sows. Supplementation from weaning until day 30 of second gestation did not have an effect on embryonic weight, ovulation rate or early embryonic survival, but did increase corpora lutea (CL) weight (P = 0.001). Eicosapentaenoic acid and docosahexaenoic acid (DHA) levels were increased in sow serum and CL (P < 0.001), whereas only DHA levels increased in embryos (P < 0.01). In conclusion, feeding n-3 LCPUFA to gilts tended to improve litter growth, but did not have an effect on overall subsequent reproductive performance.     

Effect of Supranutritional Organic Selenium Supplementation on Postpartum Blood Micronutrients,Antioxidants, Metabolites,and Inflammation Biomarkers in Selenium-Replete Dairy Cows

Dairy cows have increased nutritional requirements for antioxidants postpartum. Supranutritional organic Se supplementation may be beneficial because selenoproteins are involved in regulating oxidative stress and inflammation. Our objective was to determine whether feeding Se-yeast above requirements to Se-replete dairy cows during late gestation affects blood micronutrients, antioxidants, metabolites, and inflammation biomarkers postpartum. During the last 8-weeks before calving, dairy cows at a commercial farm were fed either 0 (control) or 105 mg Se-yeast once weekly (supranutritional Se-yeast), in addition to Na selenite at 0.3 mg Se/kg dry matter in their rations. Concentrations of whole-blood (WB) Se and serum Se, erythrocyte glutathione (GSH), and serum albumin, cholesterol, α-tocopherol, haptoglobin, serum amyloid A (SAA), calcium, magnesium, phosphorus, non-esterified fatty acids, and β-hydroxybutyrate were measured directly after calving, at 48 h, and 14 days of lactation in 10 cows of each group. Supranutritional Se-yeast supplementation affected indicators of antioxidant status and inflammation. Cows fed a supranutritional Se-yeast supplement during the last 8-weeks of gestation had higher Se concentrations in WB (overall 52 % higher) and serum (overall 36 % higher) at all-time points, had higher SAA concentrations at 48 h (98 % higher), had higher erythrocyte GSH (38 % higher) and serum albumin concentrations (6.6 % higher) at 14 days, and had lower serum cholesterol concentrations and higher α-tocopherol/cholesterol ratios at calving and at 48 h compared with control cows. In conclusion, feeding Se-replete cows during late gestation a supranutritional Se-yeast supplement improves antioxidant status and immune responses after calving without negatively impacting other micronutrients and energy status.     

Immune and oxidative response to linseed in the diet of periparturient Holstein cows

The aim of this research was to determine the influence of dietary replacement of n-6 with n-3 polyunsaturated fatty acids on cellular immunity and oxidative stress in the transition period dairy cows. The experiment was conducted on 20 dairy Holstein cows from 3±1 weeks before parturition until the 6^th week of lactation. Both groups were fed an iso-energetic and iso-nitrogenous diet. Soybean meal from control (C) group was replaced with linseed in the experimental (LS) group. Cellular immunity and oxidative stress were measured on days −10, 1, 21 and 42 relative to parturition. During the entire experimental period, the proportion of CD45⁺ cells was lower (P<0.05) in LS group compared with the C group. The phagocytosis ability and phagocytosis index of cows fed with n-3 fatty acids were significantly reduced (P<0.05) compared with the group of cows fed with n-6 fatty acids. The most severe decrease in phagocytosis ability was on day −10 and 1 relative to parturition. The activity of superoxide dismutase (P<0.05) and plasma glutathione peroxidase (P<0.05) increased around calving, although activities were not influenced by dietary treatment. Increased malondialdehyde concentration (P<0.05) was influenced by dietary n-3 fatty acids and the time relative to parturition. The immune suppression was most pronounced during periparturient period. In that matter we can conclude that not only dietary n-3 fatty acids but also oxidative stress, which reached peak at time of parturition, contributed to the reduced cellular immunity during the periparturient period.     

Effect of source of supplemental selenium on uterine health and embryo quality in high-producing dairy cows

Lactating Holstein cows (n = 135) were randomly assigned to one of the two sources of supplemental selenium (Se), sodium selenite (SS) or Se yeast (SY), fed at 0.3 mg/kg diet dry matter from 25 d before calving to 70 d in milk (DIM), in diets not suboptimal in basal Se concentrations. Cows were evaluated for health daily in the first 10 DIM, and uterine cytology of the previously gravid uterine horn was assessed at 30 DIM. The Ovsynch protocol was initiated at 42 DIM; ovarian responses to hormonal treatments were evaluated by ultrasonography. The uteri of cows were flushed 6 d after timed AI for collection of embryos and oocytes. Plasma concentrations of Se and progesterone were measured throughout the postpartum period and during the reproductive protocol, respectively, and plasma glutathione peroxidase activity was determined 6 d after AI. Concentrations of Se in pre- and postpartum diets ranged from 0.43 to 0.56 mg/kg of dry matter. Incidence of retained placenta, fever, ketosis, mastitis, acute puerperal metritis, clinical endometritis, and subclinical endometritis were not significantly different between treatments. There were no differences between groups in concentrations of Se and progesterone or glutathione peroxidase activity in plasma. Treatment did not influence ovarian responses to the synchronization protocol, fertilization rate, number of blastomeres and live blastomeres, or proportions of grades 1 and 2, degenerated, and degenerated-unfertilized embryos/oocytes. Odds of subclinical endometritis on Day 30 postpartum more than doubled in cows with fever of unknown origin or acute puerperal metritis in the first 10 DIM. Fertilization rate tended to be reduced in cows with subclinical endometritis. In summary, replacing SS with an organic source of Se in diets not suboptimal in basal Se concentrations did not improve Se status, uterine health, fertilization, or embryo quality in early lactation dairy cows.     

The role of omega-3 polyunsaturated fatty acids in reproduction of sheep and cattle

The positive effects of fat and energy supplementation on improvements in reproduction are well documented. However, the specific effects of omega-3 polyunsaturated fatty acids (n-3) on reproductive success in ruminants have not been examined in detail. While the link between n-3 and markers associated with reproduction, in particular, prostaglandin F(2α) (PGF(2α)) and the link between PGF(2α) and reproductive outcomes are well established, evidence of a direct effect of high n-3 diets on measurable reproductive outcomes in ruminants is lacking. Therefore, the aim of the current review was to examine the effect of n-3 on a number of reproductive markers and measurable outcomes in sheep and cattle. There is strong evidence linking consumption of diets high in n-3 with reduced circulating peripheral inflammatory markers such as PGF(2α). Inflammatory eicosanoids including PGF(2α), in particular, can significantly affect reproduction outcomes such as the onset of oestrus, embryo survival and parturition. While there is also evidence linking n-3 supplementation with longer time to oestrus and parturition associated with reduced PGF(2α), the effects of n-3 on other measurable outcomes of reproductive success, such as pregnancy rate, embryo survival and intergenerational effects on the health and production of offspring are largely unknown. Similarly, the effects of diets high in n-3 or n-6 polyunsaturated fatty acids on male fertility are also unknown.     

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.     

Reducing dietary protein in dairy cow diets: implications for nitrogen utilization,milk production,welfare and fertility

In light of increasing global protein prices and with the need to reduce environmental impact of contemporary systems of milk production, the current review seeks to assess the feasibility of reducing levels of dietary CP in dairy cow diets. At CP levels between 140 and 220 g/kg DM there is a strong positive relationship between CP concentration and dry matter intake (DMI). However, such effects are modest and reductions in DMI when dietary CP is below 180 g/kg DM can be at least partially offset by improving the digestibility and amino acid profile of the undegradable protein (UDP) component of the diet or by increasing rumen fermentable energy. Level and balance of intestinally absorbable amino acids, in particular methionine and lysine, may become limiting at lower CP concentrations. In general the amino acid composition of microbial protein is superior to that of UDP, so that dietary strategies that aim to promote microbial protein synthesis in the rumen may go some way to correcting for amino acid imbalances in low CP diets. For example, reducing the level of NDF, while increasing the proportion of starch, can lead to improvements in nitrogen (N) utilisation as great as that achieved by reducing dietary CP to below 150 g/kg. A systematic review and meta-analysis of responses to rumen protected forms of methionine and lysine was conducted for early/mid lactation cows fed diets containing ⩽150 g CP/kg DM. This analysis revealed a small but significant (P=0.002) increase in milk protein yield when cows were supplemented with these rumen protected amino acids. Variation in milk and milk protein yield responses between studies was not random but due to differences in diet composition between studies. Cows fed low CP diets can respond to supplemental methionine and lysine so long as DMI is not limiting, metabolisable protein (MP) is not grossly deficient and other amino acids such as histidine and leucine do not become rate limiting. Whereas excess dietary protein can impair reproduction and can contribute to lameness, there is no evidence to indicate that reducing dietary CP levels to around 140 to 150 g CP/kg DM will have any detrimental effect on either cow fertility or health. Contemporary models that estimate MP requirements of dairy cows may require refinement and further validation in order to predict responses with low CP diets.     

Effect of different feeding strategies on lactation performance of Holstein and Normande dairy cows

The dairy farming systems of Western Europe are based on a simple feeding system composed of grazed and preserved grass, maize silage and concentrates in variable proportions. There is, nevertheless, a great diversity of feeding strategies between dairy farms. Over 5 years, we studied the direct and delayed effects of four feeding strategies on the lactation and reproduction performances of Holstein and Normande dairy cows. The four feeding strategies (denoted Hh, Hl, Lh and Ll) correspond to two total mixed rations applied in winter from calving to turnout (maize silage with 30% concentrate or grass silage with 15% concentrate), which were subsequently crossed with two levels of concentrate supplementation at grazing to 210 days. Each year, 72 dairy cows managed in grouped winter calving were assigned to the four strategies. Finally, the results of 325 lactations and 295 inseminated cows were analysed. The four strategies resulted in considerable variation in nutrient intake and, in particular, in differences in concentrates consumed, with values of 1407, 1026, 773 and 392 kg dry matter per cow for strategies Hh, Lh, Hl and Ll, respectively. Total milk production (7567, 7015, 6720 and 6238 kg per cow for treatments Hh, Lh, Hl and Ll, respectively), milk fat content (39.0, 37.1, 40.3 and 38.5 g/kg, respectively), milk protein content (33.0, 31.8, 33.1 and 31.6 g/kg, respectively), and the character of the lactation and body condition curves were all highly sensitive to the strategies applied. While no significant interaction was detected on total lactation yield, the Holstein cows reacted more dramatically to each dietary change at each period, compared with the Normande cows. Winter feeding did not affect the production of milk at pasture whereas, at pasture, the milk from the cows of the H groups in winter was higher in milk fat and protein content. Reproduction performance was unaffected by feeding strategy. The Holstein cows, well fed and producing the most milk (Hh and Hb), had the lowest rate of success at first artificial inseminations (21.5%). The dual-purpose Normande cows had a pregnancy rate 10 points higher than Holstein cows. This comparison of strongly contrasting feeding strategies confirms the immediate reactivity of dairy cows (in terms of milk performance and body condition) to variations of nutritive intake throughout lactation, with a weak carryover effect from feeding levels early in lactation. In contrast, reproduction performance was less sensitive to variation in nutrient supply.     

Plasma Vitamin E and Blood Selenium Concentrations in Norwegian Dairy Cows: Regional Differences and Relations to Feeding and Health

Plasma α-tocopherol (vit E) and blood selenium (Se) concentrations in February were determined in samples from 314 dairy cows in Norway, selected to provide a representative subset of the Norwegian dairy cow population. Each sample was followed by a questionnaire with information about feeding of the cow at the time of sampling. The results were correlated to herd data and to calving and health data for each cow from the Norwegian Dairy Herd Recording System and the Norwegian Cattle Health Recording System. The mean concentrations were 6.9 μg vit E per ml plasma and 0.16 μg Se per g blood. Both levels were highest in mid lactation. Plasma vit E varied with the amount of silage fed to the cow, while blood Se varied with the amount of concentrates and mineral supplements, and with geographical region. No differences in vit E or Se levels were found between cows with recorded treatments for mastitis, parturient paresis or reproductive disorders in the lactation during or immediately prior to sampling, and those without such treatments. For ketosis, a small difference in blood Se was found between the groups with or without recorded treatments. It is concluded that winter-fed lactating cows in Norway had an adequate plasma level of vit E and a marginal-to-adequate level of Se.     

Effect of Organic Selenium Supplementation on Selenium Status,Oxidative Stress,and Antioxidant Status in Selenium-Adequate Dairy Cows During the Periparturient Period

The periparturient period represents a stressful time for dairy cows as they transition from late gestation to early lactation. Oxidation stress occurs during this period owing to the increased metabolic activity. Antioxidants supplementation slightly above the suggested requirements may be beneficial in relieving this kind of stress. The objective of this study was to determine whether supplementing selenium (Se) yeast to diets with adequate Se concentrations affects Se status, oxidative stress, and antioxidant status in dairy cows during the periparturient period. Twenty multiparous Holstein cows were randomly divided into two groups with ten replicates in each group. During the last 4 weeks before calving, cows were fed Se-yeast at 0 (control) or 0.3 mg Se/kg dry matter (Se-yeast supplementation), in addition to Na selenite at 0.3 mg Se/kg dry matter in their rations. The concentrations of Se, reactive oxygen species (ROS), hydrogen peroxide (H₂O₂), hydroxyl radical, malonaldehyde (MDA), α-tocopherol and glutathione (GSH), the activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT), and the total antioxidant capacity (T-AOC) in plasma or erythrocyte of dairy cows were measured at 21 and 7 days prepartum, and at 7 and 21 days postpartum. Cows fed Se-yeast supplement during the last 4 weeks of gestation had higher plasma Se and lower MDA concentrations at 7 days prepartum, and at 7 and 21 days postpartum, and had higher whole blood Se and lower plasma ROS and H₂O₂ concentrations at 7 and 21 days postpartum compared with control cows. Se-yeast supplementation increased plasma and erythrocyte GSH-Px activities and erythrocyte GSH concentration at 7 days postpartum as compared to Se-adequate control cows. Compared with control cows, the enhanced SOD and CAT activities, increased α-tocopherol and GSH concentrations, and improved T-AOC in plasma at 7 and 21 days postpartum in Se-yeast-supplemented cows were also observed in this study. The results indicate that feeding Se-adequate cows a Se-yeast supplement during late gestation increases plasma Se status, improves antioxidant function, and relieves effectively oxidative stress occurred in early lactation.     

Concentration of the mammalian lignans enterolactone and enterodiol in milk of cows fed diets containing different concentrations of whole flaxseed

A total of 32 lactating Holstein cows with mean body weight of 622 kg (s.e. = 24) were allotted, at week 25 of lactation, to eight groups of four cows blocked for similar days in milk. The objective of the experiment was to determine the effect of feeding four dietary concentrations (0, 50, 100 or 150 g/kg of dry matter) of whole flaxseed, which contains the plant lignan precursor secoisolariciresinol diglucoside (SDG), on concentrations of two mammalian lignans (enterodiol and enterolactone) in milk. The effects of the four diets on feed intake, milk production, milk composition and digestion were also studied. Cows within each block were assigned to one of the four isonitrogenous and isoenergetic total mixed diets and the experiment was carried out from week 25 to 29 of lactation. Diets were fed for ad libitum intake. Enterolactone was the mammalian lignan, of the two metabolites studied, detected in the milk of cows and its concentration in milk tended (P = 0.08) to increase linearly with higher intake of SDG in the diet. Feed intake, milk yield and milk composition were similar among diets. Milk fatty acid profile was slightly improved by feeding flaxseed, as shown by higher concentrations of fatty acids (e.g. n-3) recognized as being beneficial for human health. Those results suggest that feeding of whole flaxseed may result in changes in milk fatty acid composition and enterolactone content, which offer benefits for consumers.     

Nonspecific immune response of rainbow trout (Oncorhynchus mykiss Walbaum) in relation to different status of vitamin E and highly unsaturated fatty acids

This study was designed to examine the effects of dietary vitamin E (VE) on modulation of immune responses when supplied with two levels of n-3 highly unsaturated fatty acids (n-3 HUFA) in rainbow trout, Oncorhynchus mykiss. Six semipurified diets were prepared containing three levels of dietary VE (0, 100 or 1000 mg alpha-tocopheryl acetate kg(-1) diet) and n-3 HUFA either at 20 or 48% of dietary lipid provided from fish oil or docosahexaenoic acid (DHA) concentrated fish oil respectively. The diets were fed to rainbow trout (100 g initial mean weight) for 15 weeks. The VE, vitamin C (VC) content in plasma and tissues and the nonspecific immune responses, both humoral (alternative complement activity, total immunoglobulin) and cellular (phagocytosis, nonspecific cytotoxicity) were examined. VE contents in the kidney reflected the dietary input but were lower in fish fed 48% n-3 HUFA diets, and could have impaired some of immune responses compared to fish fed 20% n-3 HUFA. VC contents in kidney followed the same pattern as VE. Both humoral and cellular immune functions deteriorated in fish fed VE deficient diets whereas improvement in most of the parameters corresponded to its supplementation. However, the higher dose of dietary VE did not substantially enhance the responses assayed compared to the 100 mg dose. Besides clearly indicating the role of VE in maintaining the immune functions in fish in relation to dietary n-3 HUFA, this study has revealed that optimum health benefits could be achieved when VE is maintained slightly above the levels generally recommended for normal growth.     

The potential interaction between body condition score at calving and dietary starch content on productive and reproductive performance of early-lactating dairy cows

Improving reproductive performance is one of the most important factors affecting the profitability of dairy herds. This study investigated the effect of feeding a high starch (HS) diet and body condition score (BCS) at calving on blood metabolites, fertility and ovarian function and milk production in Holstein dairy cows. One hundred seventy-four multiparous cows were fed common close-up and early lactation diets during the first 15 days in milk (DIM). Cows were randomly assigned to 1 of 2 experimental diets from 16 until 50 DIM (n = 87 per group); normal starch (228 g/kg diet DM; NS) or HS (270 g/kg diet DM; HS) diets. Each treatment group was further subdivided based on BCS at calving as normal BCS (BCS ⩽ 3.5; normal BCS (NBCS); n = 45) or high BCS (HBCS) (BCS ⩾ 3.75; HBCS; n = 42). A significant difference was detected for increased milk production (47.24 v. 44.55 kg/day) and decreased milk fat (33.93 v. 36.33 g/kg) in cows fed HS or NS, respectively. Plasma glucose and insulin concentrations were significantly higher in cows fed the HS compared to the NS diet. Diets significantly affected DIM at first artificial insemination (AI, 79.51 ± 3.83 v. 90.40 ± 3.83 days for cows fed HS and NS diets, respectively). High BCS groups had greater milk fat content and elevated plasma nonesterified fatty acids (NEFA), β hydroxybutyrate (BHB) and bilirubin concentrations. In general, feeding higher starch diets to normal BCS cows during the first 50 DIM improved productive and reproductive performance of early-lactating dairy cows.     

Effect of supplementation with different fat sources on the mechanisms involved in reproductive performance in lactating dairy cattle

Supplementary fat positively influences reproductive performance in dairy cattle, although the mechanisms involved are not clearly defined. Our objective was to determine the effects of four different fat supplements on follicle development, plasma steroid hormone concentrations and prostaglandin (PG) synthesis in lactating dairy cattle. Forty-eight early lactation Holstein-Friesian cows (21 primiparous, 27 multiparous) were used in a completely randomized block design. Cows were fed the same basal TMR diet and received one of four fat supplements: (i) palmitic acid (18:0 fatty acid; Control), (ii) flaxseed (rich in 18:3 n-3 fatty acid; Flax), (iii) conjugated linoleic acid (a mixture of cis-9, trans-11 and trans-10, cis-12 isomers; CLA), and (iv) fish oil (rich in 20:5 and 22:6 n-3 fatty acids; FO). All lipid supplements were formulated to be isolipidic; palmitic acid was added as necessary to provide a total lipid supplement intake of 500 g/day. Cows were synchronized to be in estrus on Day 15 of dietary treatment. All antral follicles were counted, and dominant follicles, subordinate follicles and corpora lutea were measured daily via transrectal ovarian ultrasonography for one complete estrous cycle. Blood samples were collected daily, and selected samples were analyzed for progesterone, estradiol, insulin-like growth factor-1, insulin, cholesterol and non-esterified fatty acids. Estrus was synchronized a second time, and liver and endometrial biopsies were collected on Day 7 of the estrous cycle. Gene expression was evaluated for a number of genes involved in prostaglandin synthesis (endometrium) and fatty acid uptake and utilization (liver). Fat supplementation had little effect on follicle development. Cows receiving supplementary n-3 fatty acids had lesser plasma progesterone (P4) and smaller corpora lutea than cows receiving the CLA or Control supplements. Effects of fat supplementation on the endometrial expression of genes involved in PG synthesis were minor. Hepatic expression of SREBF1, ASCL1 and FABP1 was reduced by FO supplementation. Reduced plasma P4 in n-3 supplemented cows may lead to a suboptimal uterine environment for embryo development and hence reduced fertility compared to cows receiving the control or CLA supplements.     

Influence of feeding whole sunflower seed and extruded linseed on production of dairy cows, rumen and plasma constituents, and fatty acid composition of milk

Holstein cows were fed total mixed rations (TMR) supplemented with protected palm fat (PPF), whole sunflower seed (WSS) or extruded linseed (ELS) for 100 days. Percentage of dietary crude fat was 5.3, 5.1 and 5.1, respectively. Diet had no (p > 0.05) effect on feed intake, milk yield or milk protein content. Percentage of milk fat and yield of fat--corrected milk were significantly increased when diets were supplemented with WSS and ELS. Feeding PPF resulted in the lowest (p < 0.05) ruminal concentration of volatile fatty acids. No significant dietary effect on plasma characteristics was observed. Concentration of polyunsaturated fatty acids (PUFA) was higher (p < 0.05), and PUFA n-6/n-3 ratio lower (p < 0.05), in the milk fat from cows fed ELS compared to WSS. Supplementation of TMR with oilseeds compared to PPF increased the content of CLA in milk fat (p < 0.005) and decreased its atherogenicity, primarily due to a significant reduction of palmitic acid concentration. Both oilseeds significantly improved the spreadability index of manufactured butter. ELS, but not WSS, increased the susceptibility of milk fat to oxidation (p < 0.05). It can be concluded that feeding of oilseeds to dairy cows improved nutritional quality of milk fat, with supplementation with ELS producing an even more desirable milk fatty acid profile than WSS supplementation.     

Risk factors associated with detailed reproductive phenotypes in dairy and beef cows

The objective of this study was to identify detailed fertility traits in dairy and beef cattle from transrectal ultrasonography records and quantify the associated risk factors. Data were available on 148 947 ultrasound observations of the reproductive tract from 75 949 cows in 843 Irish dairy and beef herds between March 2008 and October 2012. Traits generated included (1) cycling at time of examination, (2) cystic structures, (3) early ovulation, (4) embryo death and (5) uterine score; the latter was measured on a scale of 1 (good) to 4 (poor) characterising the tone of the uterine wall and fluid present in the uterus. After editing, 72 773 records from 44 415 dairy and beef cows in 643 herds remained. Factors associated with the logit of the probability of a positive outcome for each of the binary fertility traits were determined using generalised estimating equations; linear mixed model analysis was used for the analysis of uterine score. The prevalence of cycling, cystic structures, early ovulation and embryo death was 84.75%, 3.87%, 7.47% and 3.84%, respectively. The occurrence of the uterine heath score of 1, 2, 3 and 4 was 70.63%, 19.75%, 8.36% and 1.26%, respectively. Cows in beef herds had a 0.51 odds (95% CI=0.41 to 0.63, P<0.001) of cycling at the time of examination compared with cows in dairy herds; stage of lactation at the time of examination was the same in both herd types. Furthermore, cows in dairy herds had an inferior uterine score (indicating poorer tone and a greater quantity of uterine fluid present) compared with cows in beef herds. The likelihood of cycling at the time of examination increased with parity and stage of lactation, but was reduced in cows that had experienced dystocia in the previous calving. The presence of cystic structures on the ovaries increased with parity and stage of lactation. The likelihood of embryo/foetal death increased with parity and stage of lactation. Dystocia was not associated with the presence of cystic structures or embryo death. Uterine score improved with parity and stage of lactation, while cows that experienced dystocia in the previous calving had an inferior uterine score. Heterosis was the only factor associated with increased likelihood of early ovulation. The fertility traits identified, and the associated risk factors, provide useful information on the reproductive status of dairy and beef cows.     

A dietary dairy/yeast prebiotic and flaxseed oil enhance growth,hematological and immunological parameters in channel catfish at a suboptimal temperature (15°C)

Channel catfish raised in the southern United States require two growing seasons to reach market size. Growing seasons are separated by a cool period of about 3 months when feed intake and growth are greatly reduced. A cool-weather feeding strategy to improve feed intake, growth or health of catfish might improve survival and reduce the time needed to achieve market size. We conducted a feeding trial with channel catfish at a suboptimal temperature (15°C) to determine the effects of supplementing diets with either a dairy/yeast prebiotic or flaxseed oil (high in 18:3n-3) compared with a control with soybean oil (high in 18:2n-6). The trial was conducted in recirculating systems with 1140-l tanks containing 100 fish each (mean initial weight 61.4 g±0.43 s.e.m.). A 28%-protein basal diet was supplemented with 20 g/kg cellulose and 20 g/kg soybean oil (SBO, control), 20 g/kg cellulose and 20 g/kg flaxseed oil (FLAX) or 20 g/kg of a dairy/yeast prebiotic and 20 g/kg soybean oil (PREB). Fish were fed once daily to satiation and weighed every 3 weeks to track growth. Hematology, non-specific immune responses, proximate and fatty acid composition of muscle were determined to assess diet effects. Catfish-fed FLAX or PREB had higher weight gain, feed consumption and lysozyme activity than fish fed SBO. Total n-3 fatty acids in muscle were higher in fish fed SBO or FLAX than those fed PREB. Total n-6 long-chain polyunsaturated acids were higher in muscle of fish fed PREB than those fed SBO. Fatty acids in the PREB and SBO diets were similar, so the PREB appeared to increase elongation and desaturation of n-6 fatty acids in muscle. Flaxseed oil and the dairy/yeast prebiotic both have potential to increase catfish performance at a low temperature.     

Strategies for improving fertility in the modern dairy cow

The high producing dairy cow of the 21st century is subfertile during lactation. Our objectives are to characterize physiological periods limiting reproductive performance and to describe integrated management strategies to improve pregnancy rates. Ovarian recrudescence with normal re-occurring estrous cycles and restoration of fertility to first service are associated with a reduced occurrence of periparturient metabolic and reproductive disorders. Marked negative changes in energy balance and reduced immunocompetence influence gonadotropic and metabolic hormones. Induced ovarian inactivity was associated with enhanced uterine involution. Post-partum health and reproductive performance were improved when by-pass lipids enriched in polyunsaturated fatty acids were fed in the pre- and post-partum periods. Pharmaceutical control of follicle, CL, and uterine function with PGF, GnRH and intravaginal progesterone releasing inserts, has permitted development of more optimal timed-insemination programs for first service. Likewise, resynchronization of nonpregnant cows coupled with the use of ultrasound for early pregnancy diagnosis provides the opportunity for a second timed-insemination within 3 days of a nonpregnant diagnosis. Bovine somatotropin (bST) increases embryo development and embryo survival when coupled with a timed-insemination program or cows detected in estrus. Presence of a conceptus alters endometrial expression of genes and proteins in response to bST and nutraceuticals (i.e., unsaturated fatty acids such as eicosapentaenoic and docosahexaenoic acid in by-pass lipids) to improve pregnancy rates. Postovulatory increases in progesterone may enhance pregnancy rates in targeted populations of lactating dairy cows, but timing and magnitude of the progesterone increases are pharmaceutically dependent.