Plane Of Nutrition Research Articles

The embryo affects day 14 uterine transcriptome depending on nutritional status in sheep. a. Metabolic adaptation to pregnancy in nourished and undernourished ewes

This study investigated the effects of undernutrition and the presence of the conceptus at the time of maternal recognition of pregnancy on the expression of uterine indicators of metabolism in ewes. Adult Rasa Aragonesa ewes were allocated to one of two planes of nutrition for 28 days: maintenance energy intake (control; 5 cyclic and 6 pregnant ewes) providing 7.8 MJ of metabolisable energy, and 0.5 maintenance intake (undernourished; 6 cyclic and 7 pregnant ewes) providing 3.9 MJ of metabolisable energy per ewe. RNA from intercaruncular uterine tissue was harvested at slaughter on Day 14 of estrous cycle or pregnancy, and hybridized to the Agilent 15K Sheep Microarray chip. Functional bioinformatics analyses were performed using PANTHER (Protein ANalysis THrough Evolutionary Relationships) Classification System. The presence of the embryo upregulated expression of genes encoding peptide and monocarboxylate transporters regardless of nutritional treatment, although the degree of gene expression was lower in undernourished ewes. Genes encoding enzymes involved in glycolysis were downregulated both in pregnant control and undernourished ewes, probably as a compensatory mechanism for the increased glucose transport to the uterus. Compared with control cyclic ewes, control pregnant ewes had greater expression of genes involved in oxidation of fatty acids, suggesting increased uterine energy demands. This was not observed in undernourished pregnant animals when compared to undernourished cyclic ewes; nevertheless, those animals had lower uterine expression of enzymes involved in fatty acid biosynthesis. The presence of the embryo upregulated genes involved in electron transport probably as a result of increased energy demands for pregnancy. Overall, the data indicate that depending on the nutritional status of ewe, pregnancy alters gene expression of metabolic pathways related to energy generation in the uterus. An impairment in nutrient transport and metabolism in the uterus of pregnant undernourished ewes may explain the greater embryo mortality associated with undernutrition.

Body composition changes of crossbred Holstein × Gyr cows and conceptus during pregnancy

This study aimed to evaluate the effects of plane of nutrition and advancing days of pregnancy (DP) on maternal body composition and fetal development. Differing planes of nutrition were established by 2 feeding regimens (FR): ad libitum (AL) or maintenance (MA). Sixty-two nonlactating multiparous Holstein × Gyr cows with average body weight of 480 ± 10.1 kg and an age of 5 ± 0.5 yr were used. Cows were divided into 3 groups: pregnant (n = 44), nonpregnant (n = 12), and baseline reference cows (n = 6). The 56 pregnant and nonpregnant cows were randomly allocated into 2 different FR: AL or MA. Cows fed at MA received 1.15% of their body weight on a dry matter (DM) basis, receiving corn silage and a concentrate-based diet at a ratio of 93:7 on a DM basis. Reference group cows were slaughtered at the beginning of the experimental period to estimate body composition and empty body weight. To evaluate the effects of DP, pregnant and nonpregnant animals were slaughtered at d 140, 200, 240, and 270 of gestation. Feeding regimen affected maternal tissue composition. Days of pregnancy affected fresh weight (FW), DM, and energy content, but no differences were observed for crude protein (CP) and ether extract (EE) because of DP. Feeding regimen affected mammary gland components (CP, EE, and energy content), but not fresh or dry weights. Days of pregnancy influenced almost all mammary gland components except energy content. Regarding the uterus, FR affected only fresh and dry weights; however, DP affected every uterus component measured. The only interaction between FR and DP in this study was observed for placental FW. Cows fed AL on d 270 presented the same placental FW as cows at MA and AL on d 200 and 240. Further, pregnant cows fed at MA on d 270 had greater placental FW than cows fed AL at this day. Days of pregnancy, but not FR, influenced the composition of fetal fluids in pregnant cows. Finally, cows fed at MA had greater FW for the fetus than cows fed AL; however, fetus composition changed over DP. The FW, DM, EE, and energy content increased until d 270, but CP decreased. In conclusion, the novelty of our data presents how changes due to FR and DP occur in maternal tissues and the conceptus.

Growth performance, nutrient utilization and carcass characteristics of sheep fed hydroponic barley fodder

A 120 d growth study was conducted in Deccani sheep to evaluate the effect of feeding hydroponically grown barley fodder (HBF) on growth performance, nutrient utilization and carcass characteristics. Eighteen Deccani ram lambs of 3 months age (13.0±0.42 kg) were divided into three groups of six in each in a completely randomized design. Three iso-nitrogenous rations were formulated, in which the control ration (CON) was prepared by using roughage (chopped sorghum stover) and concentrate at 60:40 ratio; the other two experimental rations were formulated by replacing 50 (L-HBF) and 75 (H-HBF), per cent of CP of concentrate mixture with HBF at low and high levels, respectively. The replacement of concentrate mixture at 50% in L-HBF significantly (P<0.05) improved the ADG compared to other dietary treatments accompanying a higher (P<0.05) DM intake. The cost per kg production was significantly (P<0.05) lowered in the L-HBF group compared to CON. Digestibility of DM, CP and NFE were significantly (P<0.05) improved with replacement of concentrate mixture with HBF in L-HBF group compared to control. The N balance was significantly (P<0.05) higher in the L-HBF lambs which were found to be on a higher plane of nutrition with greater intakes of DCP and TDN. The carcass characteristics did not vary among the three groups. The results indicated that replacement of concentrate mixture with hydroponic barley fodder at 50 per cent level of CP in the ration of growing lambs improved the nutrient utilization, N balance, plane of nutrition and growth performance and reduced the production cost.

The dynamics of energy supply and demand of foaling mares managed at pasture: a deterministic modelling approach

Context. At pasture, the nutritional status of mares will change due to a dynamic association between their energy requirements and the energy supply. Change in the plane of nutrition can influence reproductive performance measures in the mares. To help optimise nutritional and operational management of mares on stud farms, the nutritional status of Thoroughbred broodmares and the factors influencing the energy supply and demand were investigated. Aims. To assess nutritional status of the Thoroughbred broodmare herds under ‘normal’ New Zealand commercial stud-farm conditions. Methods. The energy intake, energy requirement and energy balance during the last 3 months of pregnancy and the first 5 months of lactation were modelled for mares with an initial bodyweight of 450 kg, 500 kg, 550 kg and 600 kg, and foaled at 0, 15, 50, and 90 days after 1 September. Key results. For all foaling dates and bodyweights, mares were in positive energy balance during the last 3 months of pregnancy (6.1–8.5%). Energy balance decreased as pregnancy progressed, followed by a large and acute energy deficit that was initiated soon after foaling and continued during lactation. The energy deficit during lactation varied between –8.6% and –12.4%, depending on the foaling date modelled. Mares foaling later in the season (50–90 days after 1 September) had greater and longer (30–50 days) postpartum energy deficit than did mares that foaled earlier in the season, who recovered within 20 days postpartum. The modelled changes in the energy balance would be large enough to initiate mobilisation of the fat reserve (body condition), and could, therefore, explain the observation of delayed postpartum to conception interval observed with later-foaling mares on commercial farms. Conclusions. There is a large and prolonged energy deficit soon after foaling and throughout 150 days of lactation in Thoroughbred mares managed under New Zealand commercial grazing conditions. Foaling later in the season can cause a mismatch in energy supply and demand that would increase and prolong the energy deficit. Implications. These findings suggest a need for stud farms to actively manage the pasture supply and monitor the mare’s BWT and BCS changes in an attempt to optimise the mare’s nutritional status and reproductive performance.

Dynamics of gene expression of hormones involved in the growth of broiler chickens in response to the dietary protein and energy changes

The synergy between the genetic potential and the nutrient intake determines the growth performance of meat-type chicken and nutrigenomics approach helps us understand the response of candidate genes of growth in chicken to dietary manipulations. The current study aimed to assess the growth performance and expression of hepatic growth related genes in the naked neck broiler chicken in response to different dietary energy and protein levels with a hypothesis that high plane of nutrition enhances both of these positively. The results revealed that birds have shown significantly better growth performance under high protein (HP) and high energy (HE) dietary regime. The expression profiles of the genes studied revealed upregulation of IGF-1, IGF-2, and GH under dietary HP and HE regime relative to other protein and energy levels with greater upregulation at 3rd week than the 1st and 5th week of age of birds. The IGFR and GHR mRNA expression was significantly higher under HP and HE dietary regimen with an increasing and decreasing trend from 1st to 5th week of age, respectively. A consistent and significant downregulation of IGFBP-2 was observed under HP and HE regime throughout the feeding trial. The myostatin expression was higher at 3rd week of age followed by 1st week expression. The HP and HE as well as LP (Low protein) and HE diet resulted in significant upregulation of myostatin gene expression in liver. In support to the set hypothesis of this study the high protein and high energy diet resulted in better growth performance of broiler chickens with corresponding upregulation of IGF-1, IGF-2, IGFR, GH, GHR, and Myostatin gene expression and downregulation of IGFBP-2 in liver.

Hepatic one-carbon metabolism enzyme activities and intermediate metabolites are altered by prepartum body condition score and plane of nutrition in grazing Holstein dairy cows

Precalving feeding level and body condition score (BCS) alter postcalving energy balance and oxidant status of dairy cows. We hypothesized that the reported benefits of a controlled restriction precalving depend on precalving BCS. The objective was to identify alterations in activity and intermediates of the hepatic one-carbon metabolism, transsulfuration, and tricarboxylic acid pathways. Twenty-eight pregnant and nonlactating grazing dairy cows of mixed age and breed (Friesian, Friesian × Jersey) were randomly allocated to 1 of 4 treatment groups in a 2 × 2 factorial design: 2 prepartum BCS categories [4.0 (thin, BCS4) and 5.0 (optimal, BCS5); 10-point scale], by managing cows in late lactation to achieve the 2 groups at dry-off, and 2 levels of energy intake during the 3 wk preceding calving (75 or 125% of estimated requirements), obtained via allowance (m2/cow) of fresh pasture composed of mostly perennial ryegrass and white cover. Average (± standard deviation) age was 6 ± 2, 6 ± 3, 5 ± 1, and 7 ± 3 yr for BCS4 fed 75 and 125%, and BCS5 fed 75 and 125%, respectively. Breed distribution (average ± standard deviation) for the 4 groups was 79 ± 21, 92 ± 11, 87 ± 31, and 74 ± 23% Friesian, and 17 ± 20, 8 ± 11, 13 ± 31, and 25 ± 23% Jersey. Liver tissue was collected by biopsy at -7, 7, and 28 d relative to calving. Tissue was used for 14C radio-labeling assays to measure betaine-homocysteine S-methyltransferase, 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), and cystathionine-β-synthase (CBS) activity. Liver metabolomics was undertaken using a targeted liquid chromatography with tandem mass spectrometry-based profiling approach. After initial liquid chromatography separation, mass spectra were acquired under both positive and negative ionization, whereas multiple reaction monitoring was used to measure target compound signal response (peak area count). Enzyme activity and metabolite peak area count were normalized with the homogenate protein concentration. Repeated measures analysis of variance via PROC MIXED in SAS (SAS Institute Inc., Cary, NC), with BCS, feeding, and time as fixed effects, and cow as random effect was used. All enzyme activities were affected by time, with betaine-homocysteine S-methyltransferase activity peaking at 7 d, whereas CBS and MTR activity decreased postpartum. Overall, thin cows had greater MTR activity, whereas cows fed 125% requirements had greater CBS activity. An interaction was detected between BCS and feeding for CBS activity, as thin cows fed 125% of requirements had greater overall activity. Compared with liver from BCS4 cows, BCS5 cows had overall greater betaine, glycine, butyrobetaine/acetylcholine, serine, and taurine concentrations. The same metabolites, plus choline and N-N-dimethylglycine, were overall greater in liver of cows fed 75% compared with those fed 125% of requirements. An interaction of BCS and feeding level was detected for the aforementioned metabolites plus methionine, cystathionine, cysteinesulfinate, and hypotaurine, due to greater overall concentrations in BCS5 cows fed 75% of requirements compared with other groups. Overall, differences in hepatic enzyme activity and intermediate metabolites suggest that both BCS and feeding level can alter the internal antioxidant system (e.g., glutathione and taurine) throughout the periparturient period. Further studies are needed to better understand potential mechanisms involved.

PSVII-30 Impacts of starch and fat concentrations on equine insulin sensitivity

Abstract This study assessed how substituting starch energy for fat energy affects equine insulin sensitivity. A randomized, complete block design with 5 groups of 4 horses was used to evaluate responses to isoenergetic diets containing 7.1, 9.2, 11.5, 12.8 or 14.3% starch (dry matter basis, targeting 1.0–2.2 g starch/kg body weight). Horses were fed twice daily for 21 days, housed in individual box stalls, used in regular riding lessons, and blocked by plane of nutrition (PON), targeting +1 or -1 body condition score in 30 d. On d1 and d21, a hyperglycemic clamp was performed; horses received a jugular glucose infusion to double basal blood glucose concentrations ([Glu]) in 2 h. Samples for blood glucose and insulin determination were collected every 5 m until [Glu] was held at double basal for 30 minutes. Insulin sensitivity index (ISI) and quantitative insulin sensitivity check index (QUICI) were analysed using a general linear model with fixed effects for starch percent, PON, their interaction, and a covariate for number of workouts (WN). There was no effect (P &amp;gt; 0.10) of starch percent, PON, their interaction, or WN on initial or final ISI. Change in ISI scores was significantly affected by PON (P = 0.009) with a tendency for diet and PON interaction (P = 0.091). Initial QUICI was significantly affected by WN (P = 0.030), but no other relationships (P &amp;gt; 0.10) were observed for initial or final QUICI. Change in QUICI was affected by WN (P = 0.042) with a tendency for a PON effect (P = 0.082). The QUICI and ISI scores were significantly related (P &amp;lt; 0.001; R2=0.66), and their relationship did not interact with WN (0.751), experimental period (0.348), diet (P = 0.689) or PON (P = 0.200).

PSX-40 Effects of nutritional plane before breeding on performance of hair sheep

Abstract The objective of the study was to determine effects of the nutritional plane before breeding on performance of different hair sheep breeds. Twenty-five Dorper, 27 Katahdin, and 32 St. Croix ewes with initial BW of 65.6, 65.7, and 54.3 kg (SEM=1.95) and body condition score (BCS; 1–5) of 3.35, 3.29, and 3.09, respectively, consumed wheat straw ad libitum for 11 wk before breeding. Ewes of each breed were divided into four groups, with two groups per nutritional plane (NP). Ewes on a low NP (Low-NP) were supplemented with 0.16% BW (DM) of soybean meal (SBM) and ewes on the high NP (High-NP) received 0.8% BW (DM basis) of 0.25% soybean meal and 0.75% ground corn. Ewes were divided into two groups for estrus synchronization. Four rams of each breed were used, two for the first 17 d of breeding and the other two from d 17 to 34. Conception and embryo mortality were determined by ultrasound imaging at 25 and approximately 40 d post-breeding. Average daily gain and BCS change were similar among breeds, but both were greater for High-NP vs. Low-NP (ADG: 57 vs. -4 g, SEM=8.1; BCS change: 0.22 vs. -0.02, SEM=0.041). Wheat straw DMI was greater (P = 0.01) for Low-NP than for High-NP (2.02 and 1.58% BW, respectively; SEM=0.042) and for St. Croix than for Dorper and Katahdin (P = 0.04; 1.96, 1.68, and 1.74% BW, respectively, SEM=0.060). There were no differences in the number of services or conception (P &amp;gt; 0.05), and no embryo mortality was noted. In conclusion, NP did not influence reproductive performance assessed early after breeding despite differences in ADG and BCS change. This may be due to moderate initial BCS and increased straw intake by Low-NP ewes.

165 Effect of late lactation nutrition on milk production and composition in prolific sheep on an accelerated lambing system

Abstract Late lactation nutrition is important in prolific sheep to ensure adequate lamb growth and in the context of accelerated production, to potentially improve reproductive outcomes. Therefore, the effect of plane of energy nutrition was evaluated in 24 (Dorset x Polypay) multiparous ewes randomly assigned to diets providing either 100% (C), 70% (Low) or 150% (High) of NRC energy requirements during the last 28 days of lactation (n = 4 single- and n = 4 twin-rearing ewes/group). Milk volume (MILK) was measured by hand milking following oxytocin treatment (20 I.U.) prior to and after 3 hours of removal from lambs with samples taken for composition analysis just prior and after 2 and 4 weeks of treatment. Body weight (BW) and body condition score (BCS) were followed throughout. A mixed statistical model accounting for rearing status and stage of lactation revealed that High ewes gained 4.0kg and 0.28BCS units and Low ewes lost 4.9kg and 0.21BCS units (P &amp;lt; 0.05, High vs. Low for both), but these outcomes did not differ by rearing status. C ewes maintained BCS, but lost 3.7kg relative to High ewes (P &amp;lt; 0.05). Ewes rearing twins produced greater MILK than singles (1.85L for singles vs. 2.32L for twins, P &amp;lt; 0.01). However, MILK in C ewes remained unchanged regardless of rearing status over the study period. MILK response to treatment differed according to rearing status (P &amp;lt; 0.01) with twin but not single-rearing ewes responding. After two weeks, twin-rearing High ewes increased MILK ~50% relative to pre-treatment measures (P &amp;lt; 0.01) and remained elevated until week 4, while C or Low ewes showed no treatment response. Milk fat percent increased over lactation in all ewes (P &amp;lt; 0.01). These data indicate that only twin-rearing ewes were able to respond in milk synthesis to increased energy intake demonstrating that current feeding standards for twin-rearing ewes limit milk production.

Effects of nutrition plane on productive performances of Ossimi ewes and their offspring during pregnancy and lactation periods

Feeding ewes diets with higher energy and crud protein during gestation and lactation affects the performance of lambs at weaning. The objective of this study was to determine the nutrition plane supplementation during pregnancy and lactation period affects ewes and their offspring performance. from birth to weaning. Twenty four Ossimi ewes with average weight 55.67 kg and aged 2-4 years old and their offspring (n=30) were used in completely randomized design consisting of three supplementation level (high,125%ME; standrd,100% ME and low, 60% ME) of predicated metabolizable energy requirements according to NRC, 1985. The ewes were weighted and the body weights of lambs were recorded from birth to weaning. Colostrum production was recorded during the first week after parturition, the amount of milk production was estimated after that weekly until weaning. Blood samples were also collected from the ewes and analyzed to determine blood components. There was no effect of nutrition plane on live body weight of ewes during pregnancy and lactation period. Ewes were had significantly (P≤0.01) higher colostrum and milk yield compared with ewes offered medium ME or low group. The values of TMY, ADMY and colostrum yield were significantly (P≤0.01) higher in ewes fed high ME diet compared with ewes fed on medium or low ME diet. All blood constituents were not affected by nutrition plane during pregnancy except for cholesterol and glucose levels were affected significantly (P≤0.05), Likewise, during the lactation period, with the exception of cholesterol levels, which were significantly (P≤0.05) affected. There was a significant (P≤0.05 or P≤0.01) increase in body weight and daily gain for lambs resulting from ewes offered high ME diet compared ewes offered medium ME or low ME diet. In conclusion it can be said that, nutrition plane is every important of ewes during pregnancy and lactation period and feeding the ewes at high ME can improve the performance of growth and milk production without any negative effect on the blood components.

Effect of nutrition plane on meat quail kept in thermoneutral environment: performance and carcass characteristics

AbstractThe objective of this work was to evaluate the effect of protein reduction, with or without the supplementation of limiting amino acids, on the performance and carcass characteristics of meat quails from 22 to 42 days of age in a thermoneutral environment. A total of 324 European quails were randomly allocated into nine diets. The diets were formulated based on the recommended requirement (control) and were differentiated according to crude protein (CP) reduction levels into moderate reduction (10%) and severe reduction (20%). The diets were supplemented or not with limiting amino acids. The diets with severe and moderate protein reduction meeting the methionine + cystine, lysine and threonine requirements led to weight gain equivalent to that of the control quails. The diet with a moderate reduction in CP, with or without meeting the methionine + cystine requirement or meeting the methionine + cystine and lysine requirement, led to the greatest carcass yield and a greater leg weight and were similar to the control treatment. It is observed that supplementation with the crystalline sources of the amino acids is able to improve the performance of the quails, in addition, the attendance of methionine + cystine requirement important factor when the CP levels are reduced. In our studies, diets with 17.5% CP and supplemented with methionine + cystine, lysine and threonine meet the requirements of quails, thus generating a limiting amino acid requirement, so they are recommended for meat quails from 22 to 42 days old housed in thermoneutral environment.

Age at puberty and pregnancy rate in beef heifer genotypes with contrasting nutritional intake from 8 to 13 months of age

The aim of this study was to examine the effect of plane of nutrition between 8 and 13 months of age on reproductive performance of heifers of early (EM; n = 154) or late (LM; n = 155) maturing beef breeds and with dairy (dairy-bred, n = 154) or beef (beef-bred, n = 155) dams. Heifers were fed to have an average daily gain (ADG) of 0.50 kg (MOD) or >1.00 kg (HI) for a 141- and 150-day indoor winter period. Subsequently, heifers grazed pasture, and a 12 week breeding programme was implemented. Compared to heifers fed the MOD intake diet, heifers fed the HI intake diet were younger (P < 0.001) and had greater bodyweights (P < 0.001) at puberty but did not have a greater 6- (P = 0.41) or 12- (P = 0.32) week pregnancy rate. Dairy-bred heifers were of a similar age (P = 0.55) but had a lesser bodyweight (P < 0.001) at puberty and had a greater 6- (P < 0.05) and 12- (P < 0.01) week pregnancy rate compared to beef-bred heifers. Compared to LM heifers, EM heifers were younger (P < 0.001), had a lesser bodyweight (P < 0.01) at puberty and had a greater 6-week (P < 0.01) but not 12-week (P = 0.96) pregnancy rate. Enhanced nutrition resulted in a younger age at puberty but had no effect on 12-week pregnancy rate. Dam but not sire breed affected 12-week pregnancy rate.

Prepubertal nutrition alters Leydig cell functional capacity and timing of puberty.

Leydig cell functional capacity reflects the numbers and differentiation status of the steroidogenic Leydig cells in the testes and becomes more or less fixed in early adulthood with the final establishment of the hypothalamo-pituitary-gonadal (HPG) axis after puberty. Factors influencing Leydig cell functional capacity and its role in puberty are poorly understood. Using a bovine model of dairy bulls fed four different nutritional regimes from 1 month to 12 months, and applying circulating Insulin-like peptide 3 (INSL3) as an accurate biomarker of Leydig cell functional capacity, showed that a high plane of nutrition in the first 6 months of life, but not later, significantly increased INSL3 in young adulthood. Moreover, INSL3 concentration at 4 months indicated a marked differential in early feeding regime and correlated well (negatively) with the timing of puberty, as reflected by the age in days for the first production of an ejaculate with >50 million sperm and >10% forward motility, as well as with testis size at 18 months. Reversing the diet at 6 months was unable to rectify the trend in either parameter, unlike for other parameters such as testosterone, body weight, and scrotal circumference. This study has shown that early prepubertal nutrition is a key factor in the development of Leydig cell functional capacity in early adulthood and appears to be a key driver in the dynamic progression of puberty.

Invited Review: Nutritional regulation of gut function in dairy calves: From colostrum to weaning

PurposePublished literature regarding calf nutrition was reviewed to create an information base for the implementation of proper nutritional management to maximize health and productivity.SourcesThe main source of data and information for this review was peer-reviewed literature.SynthesisFeeding a sufficient volume of colostrum during the first hours of life is crucial to calf health and survival; however, less is known about transition milk feeding and the potential benefits of the myriad of bioactive compounds it contains. After feeding colostrum and transition milk, calves are susceptible to diarrhea when moved onto high amounts of milk, and antibiotic use is often necessary to decrease disease. Feeding an elevated plane of milk nutrition results in increased ADG and, in some studies, increased future milk production. Thus, this nutritional strategy is recommended; however, weaning calves from high volumes of milk represents massive changes in the structure and microbiology of the gastrointestinal tract.Conclusions and ApplicationsColostrum and transition milk contain an abundance of bioactive molecules that can positively affect gut development and microbiota. There is significant potential for the use of novel feeding strategies and microbial-based products as alternatives to antibiotics. Calves fed an elevated plane of nutrition in the first month of life have greater productivity and growth. However, weaning should take place later in life. Moreover, applying a proper step-down feeding protocol is recommended, as it allows calves to intake and digest sufficient solid feed for growth and minimize distress at weaning.

Carryover effects of pre- and postweaning planes of nutrition on reproductive tract development and estrous cycle characteristics in Holstein heifers

The objectives of this study were to investigate the carryover effects of differing pre- and postweaning planes of nutrition on prepubertal reproductive tract development and postpubertal estrous cycle characteristics in Holstein heifers. Heifer calves (n = 36) were randomly assigned to receive either a low or a high (5 or 10 L of whole milk/d, respectively) preweaning diet from 1 to 7 wk of age and either a low or a high (70 or 85% of concentrate dry total mixed ration, respectively) postweaning diet from 11 to 25 wk of age. Starting at wk 26 of age, heifers were subjected to weekly transrectal ultrasonography until wk 33 or until first ovulation to assess endometrial thickness and ovarian follicular count and size in the prepubertal phase. In a subset of heifers (n = 28), ovarian ultrasonography continued weekly until at least the second ovulation was confirmed; thereafter, ovarian dynamics (through ultrasonography) and blood progesterone (P4) were assessed every 2 d throughout 1 complete estrous cycle in the postpubertal phase. In the prepubertal phase, endometrial thickness (12.0 ± 0.4 vs. 10.8 ± 0.3 mm) and largest follicle size (11.8 ± 0.3 vs. 10.9 ± 0.2 mm) were greater in heifers fed the high postweaning diet than in those fed the low postweaning diet. Furthermore, the number of class 2 (6-9 mm) follicles was greater in heifers fed the high preweaning diet than in those fed the low preweaning diet (1.6 ± 0.1 vs. 1.1 ± 0.1), whereas the number of class 3 (>9 mm) follicles was greater in heifers fed the high postweaning diet than in those fed the low postweaning diet (1.2 ± 0.1 vs. 1.0 ± 0.1). In the postpubertal phase, overall corpus luteum and P4 dynamics did not differ among pre- or postweaning treatments; however, P4 at 4 d preceding luteolysis was lesser in heifers fed the high postweaning diet than in those fed the low postweaning diet (6.1 ± 0.4 vs. 7.7 ± 0.4 ng/mL). In addition, compared with heifers fed the low postweaning diet, those fed the high postweaning diet had a greater number of antral follicles (31.4 ± 2.2 vs. 21.4 ± 2.3) and tended to have more class 3 follicles (3.6 ± 0.3 vs. 2.7 ± 0.3). Results indicate positive carryover effects of increasing the preweaning plane of nutrition from 5 to 10 L of whole milk/d on prepubertal follicular growth in Holstein heifers. Furthermore, an increased postweaning plane of nutrition (85 vs. 70% of concentrate dry total mixed ration) advanced reproductive development through greater endometrial thickness and follicular growth in the prepubertal phase and increased the population of antral follicles in the postpubertal estrous cycle.

Follicle-stimulating hormone receptors expression in ovine corpora lutea during luteal phase: effect of nutritional plane and follicle-stimulating hormone treatment

Corpus luteum (CL), a transient endocrine gland critical for reproductive cyclicity and pregnancy maintenance, is controlled by numerous regulatory factors. Although LH is widely recognized as the major regulator, other factors may also affect luteal functions. It has been demonstrated that FSH receptors (FSHR) are expressed not only in ovarian follicles but also in other tissues within the reproductive tract, including the CL. To evaluate FSHR expression in nontreated (nonsuperovulated; experiment 1) or FSH-treated (superovulated; experiment 2) sheep fed a control (C; maintenance), excess (O; 2 × C), or restricted (U; 0.6 × C) diet, CL were collected at the early, mid and/or late luteal phases (n = 5–7 per group). Protein and messenger RNA (mRNA) expression of FSHR were detected in the CL from all groups using immunohistochemistry followed by image analysis and quantitative RT-PCR, respectively. Follicle-stimulating hormone receptor was immunolocalized to steroidogenic small and large and nonsteroidogenic luteal cells. In both experiments, FSHR protein expression was not affected by stage of luteal development or diet. In experiment 1, expression of mRNA for all FSHR variants was greater (P <0.02 to 0.0003) at the late phase than mid or early luteal phase, and in experiment 2, it was greater (P < 0.001) at the mid than early luteal phase. Plane of nutrition did not affect FSHR mRNA expression. Comparison of FSH-treated with nontreated ewes demonstrated that FSH increased FSHR protein expression by 1.5- to 2-fold (P < 0.0001) in all groups, and mRNA expression by 7- to 30-fold (P < 0.001) for (1) FSHR-1 in all groups except U at the early luteal phase, (2) FSHR-2 in C, O, and U at the mid-phase, but not early luteal phase, and (3) FSHR-3 in U at the mid-luteal phase. Our data demonstrate that (1) FSHRs are expressed in ovine CL at several stages of luteal development, (2) FSHR protein expression does not change during the luteal phase and is not affected by diet, (3) FSHR mRNA expression not only depends on the stage of the estrous cycle but also not affected by diet in nonsuperovulated or superovulated ewes, and (4) in vivo FSH treatment enhanced FSHR protein and/or mRNA expression in the CL depending on diet and phase of the estrous cycle. Presence of FSHR in the CL indicates a regulatory role of FSH in luteal function in sheep. As very little is known about the possible role of FSH and FSHR in luteal functions, further studies should be undertaken to elucidate the endocrine, molecular, and cellular mechanisms of FSH effects on the CL.

Pre-weaning plane of nutrition and Mannheimia haemolytica dose influence inflammatory responses to a bovine herpesvirus-1 and Mannheimia haemolytica challenge in post-weaning Holstein calves

The objectives of this study were to determine whether plane of nutrition (PON) of milk replacer previously provided to calves, and dosage level of Mannheimia haemolytica (MH), influenced inflammatory responses to a combined viral-bacterial respiratory challenge. Holstein calves (1 d of age; n = 30) were assigned to treatments in a 2 × 3 factorial with pre-weaning PON and MH dose as main effects (n = 5 per treatment). Calves were fed either a low (LPN; n = 15) or a high PON (HPN; n = 15) from birth through weaning. Calves fed LPN were fed 436 g of dry matter (DM) per day of milk replacer until weaning, and HPN calves were fed 797 g of DM per day of milk replacer from d 1 to 10 and 1,080 g of DM per day from d 11 until weaning. Calf starter and water were offered ad libitum. Calves were step-down weaned beginning at d 54 and moved into an enclosed barn at d 70. Indwelling rectal temperature (RT) recording devices and jugular catheters were inserted at d 80. Calves were challenged with 1.5 × 108 plaque-forming units (pfu) per mL of bovine herpesvirus-1 (BHV-1) in each nostril at d 81 and with either 106, 107, or 108 cfu of MH at d 84. Blood samples were collected at varying intervals relative to BHV-1 and MH challenges. Four LPN calves either died or were euthanized soon after the 144-h observation period, whereas all HPN calves survived the entire observation period. As dosage of MH administered increased, acute and systemic inflammatory responses increased. Higher doses of MH resulted in increased leukocyte, neutrophil, and haptoglobin concentrations in infected calves. Data from the current study suggest that the highest dose, 108 cfu, triggered weaned calves' acute disease response, whereas the lower doses, 106 and 107 cfu, caused more moderate inflammation and disease. The effects of PON on inflammation responses to the disease challenge indicated that calves previously fed the LPN diet had more severe pathophysiological responses. Calves fed LPN showed higher peripheral neutrophil and leukocyte counts and serum haptoglobin concentrations following the BHV-1 challenge. Additionally, following the MH challenge, LPN calves had higher peripheral neutrophil counts, neutrophil-to-lymphocyte ratios, and serum tumor necrosis factor-α concentrations. These data demonstrate that higher doses of MH increase the acute inflammatory response and prolong inflammation, and that calves previously fed LPN responded more severely to the combined viral-bacterial respiratory challenge.

211 Young Scholar Presentation: Developing and validating a heat stress model in dairy cows

Abstract Heat stress (HS) negatively impacts production parameters, including milk yield and composition, growth and reproduction. Precisely studying HS typically requires expensive climate-controlled facilities, resources often inaccessible to most scientists. Therefore, we evaluated the efficacy of using an electric heat blanket (EHB) as an alternative and cost-effective method to study HS and determine whether EHB-induced hyperthermia affects physiological and production parameters similar to natural HS. This was the first proof of concept study examining this model. Results indicated increased body temperature indices (i.e., rectal temperature and respiration rate) and reduced DMI and milk yield, as well as altered milk composition similar to natural and climate-controlled HS studies. In experiment 2, we examined the EHB model in combination with a pair-feeding (PF) design. By employing the PF design, we clearly illustrated that a lowered nutritional plane explains only approximately 50% of the decreased milk yield in HS cows, with the remaining portion due to changes in post-absorptive changes in nutritional physiology. In addition, the EHB blunted adipose tissue mobilization and increased plasma biomarkers of muscle catabolism. Results from this study validated that the EHB is a valid model to study HS; therefore, experiment 3 was designed to assess nutritional HS mitigation strategies using the EHB model. Dietary electrolyte, osmolyte, and energetic compounds (EOEC) were evaluated as re-hydration therapy on body temperature indices in HS lactating Holstein cows. Skin temperature was increased in EOEC-supplemented cows relative to controls which suggests that EOEC increased heat dissipation. In addition, EOEC-supplemented cows had increased glucose and insulin levels compared with controls which is due to the energetic compounds (i.e., dextrose) present in the EOEC supplement. Collectively, employing EHB model provides an excellent new platform for discovery research and evaluating pragmatic HS mitigation strategies.

Early lactation performance in Holstein heifers first calving at 36 months and managed for high or low weight gain during mid- and late gestation.

The effect of weight gain during mid- and late gestation in dairy heifers on performance at the start of first lactation was studied. In this experiment, 47 Holstein heifers with first calving at 36 months of age were used. The plane of nutrition aimed to have a high (900 g/d, H; n = 23) and low (500, L; n = 24) average daily gain (ADG) from the 4th month of gestation until 3 weeks before the expected day of calving, achieved by ad libitum intake of high quality pasture (H) or controlled intake of a total mixed ration (L). Body weight (BW), body condition score (BCS), milking, and reproductive performances were recorded. Concentrations of plasma non-esterified fatty acids (NEFA), glucose, beta-hydroxybutyric acid (BHBA), and urea were characterised at weeks 2, 4, 6 and 8 of lactation. Milk fatty acid composition was determined at weeks 3 and 6. A total of 39 heifers successfully calved and completed first lactation. During feeding treatment the required ADG were achieved. BW and BCS were higher in H heifers at calving compared to L heifers: 707 vs. 640 kg, and 3.91 vs. 3.01 respectively. H heifers lost more weight, BCS and had lower feed intake during the beginning of first lactation (-0.8 kg DM/d/heifer over the first 4 weeks of lactation). Per day of lactation, H heifers produced significantly more milk (29.2 vs. 26.2 kg), fat (1.27 vs. 1.07 kg) and protein (0.84 vs. 0.477 kg) from 0 to 8 weeks of lactation. Concentrations of NEFA, glucose and BHBA were higher in H heifers compared to L heifers, but urea concentration was not affected. Concentration of preformed fatty acids in the milk (C16 and more) was higher. As a result, the calculated daily net energy balance during the first 8 weeks of lactation was -1.53 and -5.95 MJ for L and H heifers, respectively.

Influence of weaning date and late gestation supplementation on beef system productivity I: animal performance.

A 4-yr experiment examined how weaning date and prepartum nutrition affected productivity in a spring (March and April) calving system. Crossbred beef cows (479 ± 59 kg, n = 144) were used in a completely randomized design with a 2 × 4 factorial treatment arrangement: 1) cows were weaned in early October or early December; and 2) during late gestation cows were fed on a dry matter basis a 32% crude protein supplement at 0, 0.41, or 0.82 kg/cow/d on dormant upland range or grazed corn residue without supplement. Cow body condition score (BCS) was affected (P ≤ 0.01) by treatment prior to parturition and breeding but was similar (P > 0.27) among all treatments in October. Dams on a higher nutritional plane during winter treatment had greater (P < 0.01) BCS and body weight (BW) prior to parturition and breeding. Subsequent pregnancy rates (88% to 97%) were not influenced (P > 0.76) by weaning date, but tended (P = 0.10) to be lower for cows grazing winter range without supplement. Calves born to dams grazing winter range without supplement had lower (P < 0.01) BW in October and adjusted weaning BW. Pre-breeding BW of heifers weaned in December born to cows grazing winter range without supplement was lower (P < 0.01) than contemporaries born to cows in all other treatment combinations. However, postweaning (0.48 kg/d) and postbreeding (0.42 kg/d) average daily gain, percentage cycling before breeding (33%), and pregnancy rate (81%) was similar (P > 0.12). Within weaning date, steers born to cows grazing winter range without supplement had lower (P < 0.05) hot carcass weight (HCW) than contemporaries born to cows grazing corn residue. Cows weaned in December had decreased BW and BCS but similar pregnancy rates as cows weaned in October. Weaning date and dam maternal nutrition had minimal impact on heifer progeny pregnancy rate. Steer progeny born to dams on a higher nutritional plane had similar HCW at slaughter when adjusted to equal fat thickness.