The effect of calcareous marine algae, with or without marine magnesium oxide, and sodium bicarbonate on rumen pH and milk production in mid-lactation dairy cows.

Two experiments were carried out to evaluate different dietary buffers and their influence on (1) rumen pH in dairy cows and (2) milk production in dairy cows. The supplements included were calcareous marine algae (CMA; Lithothamnion calcareum), with or without marine magnesium oxide (MM; precipitated magnesia derived from seawater), and sodium bicarbonate (SB). Dietary treatments in experiment 1 consisted of the control [32.9% starch and sugar, and 19.9% neutral detergent fiber from forage per kg of dry matter (DM)] including no dietary buffer (CON); the control plus 0.45% DM CMA (CMA); the control plus 0.45% DM CMA and 0.11% DM MM (CMA+MM); the control plus 0.9% DM SB (SB). Diets were formulated to a dry matter intake (DMI) of 18 kg per cow/d. Dietary treatments in experiment 2 also consisted of CON (28.3% starch and sugar, and 23% neutral detergent fiber from forage per kg of DM), CMA, CMA+MM, and SB and were formulated to achieve identical intakes of experimental ingredients (80 g of CMA, 80 g of CMA plus 20 g MM, and 160 g of SB per cow/d) with a DMI of 22.6 kg per cow/d. Experiment 1 used 4 rumen-cannulated dairy cows in a 4 × 4 Latin square design. Rumen pH was measured over five 2-h periods, following feeding, using rumen pH probes. In experiment 2, 52 multiparous and 4 primiparous cows (62.7 ± 3.4 d in milk) were assigned to 4 experimental treatments for 80 d. Both CMA treatments maintained a greater mean rumen pH than the CON during 4 of the 5 periods following feeding and the CON had a greater number of hours below rumen pH 5.5 compared with all other treatments. Dry matter intakes tended to be higher on the SB compared with CON. The CMA treatment increased the production of milk fat and protein yield (kg/d) compared with all other treatments. Both CMA and CMA+MM increased milk fat yield compared with CON but were similar to each other and SB. Protein yield was highest in the CMA treatment compared with CON, CMA+MM, and SB. All 3 buffer treatments increased milk fat concentration compared with CON but did not differ from each other. The SB treatment reduced milk protein concentration and milk production efficiency, energy-corrected milk per kilogram of DMI. Results indicate that the addition of CMA can benefit milk fat and protein production when included in diets based on typical feedstuffs of the northern European region. The use of CMA when compared with SB, in such diets, can increase milk protein production and milk production efficiency.

Short communication: Effect of dietary manipulation of crude protein content and nonfibrous-to-fibrous-carbohydrate ratio on energy balance in early-lactation dairy cows.

Disparities between nutrient intake and demand often result in a state of negative energy balance (EB) in the early-lactation dairy cow. Reducing dietary crude protein (CP) content and providing glucogenic nutrients may overcome this issue. This study evaluates whether or not offering a diet lower in CP and higher in nonfiber carbohydrates (LP-NFC) can improve EB and the metabolic status of the early-lactation dairy cow compared with a diet higher in CP and fibrous carbohydrates (HP-FC). Twenty Holstein-Friesian dairy cows were assigned to 1 of 2 dietary treatments in a randomized block design. Diets were isoenergetic (6.57 MJ of net energy for lactation) and formulated to contain 15% CP and 6% starch (HP-FC), or 12% CP and 28% starch (LP-NFC) and were offered for the first 63 d of lactation. Intake and milk yield were determined daily, whereas milk and blood samples, weights, and body condition scores were collected weekly. Intakes (mean ± standard errors of the mean, SEM) of dry matter (17.4 ± 0.6 kg/d) and energy (113.0 ± 4.6 MJ of net energy for lactation) were not different between treatments. However, the HP-FC group had a higher milk yield (31.8 vs. 28.9 ± 1.4 kg/d) and a lower EB compared with the LP-NFC group. Blood urea N concentration (3.5 vs. 1.8 ± 0.2 mmol/L) was higher, whereas bilirubin (6.0 vs. 6.7 ± 0.2 mmol/L) and ß-hydroxybutyrate concentrations (0.7 vs. 0.8 ± 0.05 mmol/L) were lower in the HP-FC group compared with the LP-NFC group. These data suggest that EB can be improved during early lactation through the manipulation of milk output by offering a lower CP, higher NFC diet.

Effect of timing of post-partum introduction to pasture and supplementation with Saccharomyces cerevisiae on milk production, metabolic status, energy balance and some reproductive parameters in early lactation dairy cows.

Dietary change, an inconsistent nutrient intake and high levels of milk production make the early post-partum period (PP) a challenging time for the lactating dairy cow. This experiment investigates the effects of two early PP nutritional management strategies (NM): abrupt introduction to pasture (AP) or a total mixed ration (TMR) for 21 days followed by a gradual introduction to pasture over 7 days (GP), with (Y) or without (C) live yeast (YS) on milk production, energy balance (EB) and selected metabolic and reproductive variables. Forty multiparous dairy cows were assigned to one of four dietary treatments in a two (AP vs. GP) by two (Y vs. C) factorial, randomized block design. The experiment was conducted from days 1 to 70 PP. Blood samples were taken on day 1, day 5 and every 10 days until day 45 to determine metabolites, whilst intake (DMI), and EB were determined during week 6 PP. Milk was sampled weekly for fat, protein and lactose. Trans-rectal scanning for reproductive variables commenced on day 10 PP. Animals in the GP group had a higher DMI (p = 0.04), higher fat yield (p = 0.08) and fewer days to first ovulation (p = 0.09) vs. those in the AP group. EB (-3.5 ± 0.67 units of energy for milk production) and body condition score loss (0.70 ± 0.09) were not affected by NM. However, non-esterified fatty acids (NEFA) (p < 0.01) were higher, and glucose (p = 0.02) was lower in the AP vs. the GP group. Supplementary YS tended to improve EB (p = 0.09) and reduced NEFA (p < 0.01) vs. non-supplemented animals. These data suggest that offering animals a nutritionally balanced TMR during the first 3 weeks PP followed by a gradual introduction to pasture can improve DMI vs. pasture-based diets. Additionally, the blood metabolic profile suggests a more favourable energy status in the GP group or where YS was supplemented during the early PP period.

The effect of body condition score at calving and supplementation with Saccharomyces cerevisiae on milk production, metabolic status, and rumen fermentation of dairy cows in early lactation.

The objective of this study was to examine the effects of live yeast (LY) supplementation and body condition score (BCS, 1-5 scale) at calving on milk production, metabolic status, and rumen physiology of postpartum (PP) dairy cows. Forty Holstein-Friesian dairy cows were randomly allocated to a 2 × 2 factorial design and blocked by yield, parity, BCS, and predicted calving date. Treatments were body condition at calving (low for BCS ≤3.5 or high for BCS ≥3.75; n=20) and supplementation with LY (2.5 and 10 g of LY/d per cow for pre- and postcalving, respectively; control, no LY supplementation; n=20). The supplement contained 10(9) cfu of Saccharomyces cerevisiae/g (Yea-Sacc(1026) TS, Alltech Inc., Nashville, TN). Daily milk yield, dry matter intake, milk composition, BCS, body weight, and backfat thickness were recorded. Blood samples were harvested for metabolite analysis on d 1, 5, 15, 25, and 35 PP. Liver samples were harvested by biopsy for triacylglycerol (TAG) and glycogen analysis on d 7 precalving, and on d 7 and 21 PP. Rumen fluid was sampled by rumenocentesis for all cows on d 7 and 21 PP. Supplementation with LY had no effect on milk yield, dry matter intake, rumen fluid pH, or blood metabolites concentration of dairy cows with high or low BCS at calving. Feeding LY increased rumen acetate proportion and protozoal population, tended to increase liver glycogen, and decreased rumen ammonia nitrogen during early lactation. Over-conditioned cows at calving had greater body reserve mobilization and milk production and lower feed intake, whereas cows with a moderate BCS at calving had greater feed intake, lower concentrations of nonesterified fatty acids and ß-hydroxybutyrate, lower liver TAG and TAG:glycogen ratio, and faster recovery from body condition loss. Additionally, the data suggest that concentrations of liver enzymes in blood might be used as an indicator for liver TAG:glycogen ratio. Results indicate that in the case of this experiment, where the control treatment was associated with an acceptable rumen pH, feeding yeast did not significantly improve indicators of energy status in dairy cows.

Effect of diet quantity and urea supplementation on oocyte and embryo quality in sheep.

The objective was to investigate the effects of dietary energy and urea supplementation on oocyte and embryo quality in sheep using in vivo and in vitro experimental models. Sixty-three ewes were fed grass meal at 0.5 or 2.0 times maintenance energy requirements (MER). The diet was supplemented with feed grade urea (U) for half of the ewes on each energy treatment. Ewes were stimulated with 1000 IU eCG and either slaughtered on the day of pessary withdrawal, for in vitro embryo production, or mated and slaughtered on Day 5 for embryo recovery. Urea decreased cleavage rate (48.3 vs 39.7%) and consequently blastocyst rate (41.6 vs 36.8%) but the differences were not significant. Oocytes from animals on 2.0 MER had a lower cleavage rate (54.9 vs 36.0%) and blastocyst yield (49.3 vs 31.4%) than those on 0.5 MER. However, there was an interaction between urea and energy for cleavage (P = 0.04) and blastocyst yield (P = 0.03) indicating a variable response to urea in the presence of high energy. This was manifested by a decrease in cleavage rate in the presence of urea and high energy (22%, 8 of 36), and a reduction in blastocyst development (19%, 7 of 36). When blastocyst development rate was expressed as a proportion of cleaved oocytes there was no difference between groups; in addition, there was no difference between groups in terms of blastocyst hatching rate (overall mean 66.1%) or blastocyst cell number on Day 8 (overall mean +/- SEM, 138.4 +/- 9.0, n=61). The effect of urea on cleavage rate in vivo was more severe. Urea supplementation reduced (P<0.001) the cleavage rate (93 vs 62%). Despite this, the yield of blastocysts was unaffected. Oocytes from ewes on 0.5 MER exhibited a lower (P<0.05) cleavage rate than those on 2.0 MER (66 vs 87%). This effect was also apparent at the blastocyst stage (40.0 vs 50.9%), although the difference was no longer significant. There were no differences in hatching rate (overall mean 70.7%) or blastocyst cell numbers (overall mean +/- SEM, 166.3 +/- 15.6, n=40). Collectively, these results suggest that both high dietary energy and urea content influence subsequent embryo development in vitro, and the deleterious effects of urea are likely influenced by concomitant energy intake.

Effects of diet type on establishment of pregnancy and embryo development in beef heifers.

The objectives were to determine the effects of elevated blood urea concentrations on: (i) the response to superovulation, fertilisation rate, and early embryonic development in beef heifers, and (ii) embryo survival from days 7 to 35 of gestation. In Experiment 1, heifers (18-24 months) were allocated at random (n=20 per treatment) to one of the following diets: (i) ad libitum grass silage plus 5 kg commercial beef concentrates per day (controls); (ii) ad libitum grass silage plus 5 kg concentrates and 250 g feed grade urea per day (HE/HU); or (iii) ad libitum wheaten straw plus 250 g feed grade urea and 50 g vitamin/mineral mix per day (LE/HU). Serum urea concentrations were monitored throughout the experiment. Oestrus in heifers was synchronised using an intravaginal releasing device (CIDR(®), InterAg, New Zealand). Oestrus was detected and in vitro produced blastocysts (day 7, morphological grades 1 and 2) were transferred to the heifers 7 days later (19 days after start of treatment diets). The heifers were maintained on the dietary treatments for a further 28 days, when pregnancy status was determined by transrectal ultrasonography. Detected pregnancies were terminated using 15 mg luprostiol and recycled for Experiment 2. In Experiment 2, following a 14-day dietary rest period, the heifers were re-allocated at random to the three dietary treatments above. Heifers were treated with a CIDR for 8 days and 15 mg luprostiol was given 12h before pessary withdrawal. They received 144 mg pFSH (Folltropin(®)-V, Vetrepharm, Canada) given as 8 injections over 4 days commencing on day 6 of CIDR/dietary treatment. Heifers were artificially inseminated 48 h after progesterone pessary withdrawal using commercial semen of proven fertility by a competent inseminator. The heifers were maintained on their diets until slaughter, 3 days post insemination when corpora lutea numbers were determined and embryos were recovered and cell numbers determined visually. Serum urea concentrations were greater in heifers on LE/HU than in those on HE/HU diets, which in turn were greater than controls (7.1 ± 0.5, 4.9 ± 0.3 and 3.2 ± 0.1 mmol/L, respectively; P<0.05). There was no effect of diet type on pregnancy rate at day 35 (42%, 47% and 46%) and on the number of corpora lutea following superovulation (5.2 ± 0.8, 5.8 ± 1.5 and 6.8 ± 1.1) for heifers on control, HE/HU and LE/HU diets, respectively. The total number of embryos recovered per heifer was not different between the three groups (2.7 ± 0.6, 3.4 ± 1.1 and 4.8 ± 0.8 for heifers on control, HE/HU and LE/HU diets, respectively; P>0.05), but the number of embryos with 8 or more cells at recovery was greater in heifers on LE/HU than on control diets (3.4 ± 0.8 compared with 1.0 ± 0.3; P<0.05). However the percentage of embryos recovered with 8 or more cells was not different between groups (70.0 ± 13.3, 86.9 ± 7.2 and 76.5 ± 7.9%, for heifers on control, HE/HU and LE/HU diets respectively). Fertilisation rate, expressed as the proportion of embryos with more than one cell at recovery relative to the total number of embryos recovered, was less in the heifers on the control diet than in the other two dietary treatments (61.3 ± 11.8, 92.0 ± 3.5 and 86.8 ± 5.4% for heifers on control, HE/HU and LE/HU diets, respectively; P<0.05). Deleterious effects of urea on reproduction were not found, suggesting that adverse effects of urea are likely to take place at the early oocyte development stage prior to ovulation or fertilisation following an increase in protein intake.

Banding or Burdizzo castration and carprofen administration on peripheral leukocyte inflammatory cytokine transcripts.

The objective was to investigate if Banding or Burdizzo castration of bulls would alter the gene expression profile of a range of peripheral leukocyte inflammatory cytokines (IL-1, IL-6, IL-8, IL-10, interferon-γ and tumor necrosis factor-α) and to determine if the administration of carprofen (C) before castration would affect the expression of these genes. Thirty Holstein-Friesian bulls (5.5 months; Mean 191±(SEM) 3.7 kg) were blocked by weight and randomly assigned to one of five treatments: (1) untreated control (CON); (2) Banding castration at 0 min (BAND); (3) BAND following an i.v. injection of 1.4 mg/kg BW of carprofen (C) at -20 min (BAND+C); (4) Burdizzo castration at 0 min (BURD); or (5) BURD following 1.4 mg/kg BW of carprofen at -20 min (BURD+C). Blood samples were collected at 1 h before castration and 6, 24 and 48 h post-castration for routine hematology and quantitative real-time PCR analysis of cytokine gene expression analysis. Generally, there were no differences (P>0.05) among treatment groups in hematological variables following castration. Cortisol concentrations were unchanged throughout the experimental period in CON bulls. BURD animals had greater cortisol concentrations than BAND and CON animals at 6 h post treatment. Transitory effects were observed only in the expression of IL-6 and TNF-α. The relative expression of IL-6 was greater in the BURD than in the BAND treatment (P<0.05) at 24 h post-castration and was greater in the BURD+C group than in the BURD group (P<0.05) at 48 h. The relative expression of TNF-α was greater in BAND than in the BURD group (P<0.05) at 48 h. In conclusion, these findings indicate that Banding or Burdizzo castration did not have any major effect on peripheral leukocyte inflammatory cytokine gene expression; Banding castration caused a greater pro-inflammatory cytokine gene expression reaction than Burdizzo castration and carprofen administration can affect IL-6 gene expression levels in BURD castrated animals.

Effects of banding or burdizzo castration of bulls on neutrophil phagocytosis and respiratory burst, CD62-L expression, and serum interleukin-8 concentration.

The objective was to investigate measures of neutrophil function in response to banding or burdizzo castration of bulls. Thirty-two Holstein-Friesian bulls (14 mo old, 505 +/- 7.8 kg of BW) were assigned to 1 of 4 treatment groups: 1) sham-handled control (CON); 2) banding castration alone (BAND); 3) burdizzo castration alone (BURD); or 4) cortisol infusion (CORT) as a further control group. For each group on d -14, 8 animals (2 animals/treatment) were tied up in tie stalls (day of treatment = d 0). At -2, 2, 6, 12, 24, 48, 72, and 144 h relative to treatment time, blood samples were collected for analyses of neutrophil phagocytosis and respiratory burst, neutrophil CD62-L expression, and serum IL-8 concentration. Leukocyte counts, phagocytosis activity, and CD62-L expression were similar (P > 0.05) among the 4 treatment groups. The BURD castrates had greater burst activity compared with BAND castrates (P = 0.048) and CON (P = 0.01) at 72 h posttreatment. The BURD castrates had a greater percentage of granulocyte positive leukocytes (Gr%; P < 0.01) at 2 h posttreatment compared with CON and CORT bulls. The BURD castrates had greater (P < 0.05) Gr% compared with BAND, CON, and CORT animals at 24, 48, and 72 h posttreatment. The BURD and BAND castrates had greater Gr% (P < 0.05) compared with CORT bulls at 144 h posttreatment. In general, BAND, BURD, and CORT did not affect serum IL-8 concentration. Banding castration, BURD, and CORT did not induce leukocytosis, whereas BURD induced a modest neutrophilia. Neutrophil functioning in terms of phagocytosis and respiratory burst and serum IL-8 concentration were not compromised by BAND, BURD, and CORT. These findings indicate nonsurgical castration is unlikely to induce a severe acute systemic inflammatory response in terms of neutrophil function.