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Abstract: The aim of this study was to investigate the effect of an abrupt or a gradual introduction to pasture after calving and supplementation with live yeast culture (YC) on ruminal pH and fermentation in early lactation dairy cows. Eight multiparous rumen-cannulated Holstein/Friesian dairy cows were randomly allocated to a 2×2 factorial arrangement of treatments prior to calving. Treatments were: nutritional management (NM), abrupt introduction to pasture on the day of calving (AP) or gradual introduction to pasture after the transition period had passed (GP); and supplementation with YC (2.5×109 colony forming units, cfu, of Saccharomyces cerevisiae 1026) (Y) or control (C). Ruminal fluid was harvested on d 8–10 and 22–24 post-partum (PP) to assess pH, volatile fatty acid (VFA), lactate, NH3–N and protozoal count. Ruminal pH in the first measuring period (d 8–10 PP) was not affected by YC supplementation while feeding management had an effect with higher (P<0.01) pH in GP than AP groups averaging 6.15 vs 5.96±0.03, respectively. During the second measuring period (d 22–24 PP) ruminal pH was greater in Y than C groups averaging 6.10 vs 5.95±0.04, respectively, and in GP than AP groups averaging 6.11 vs 5.94±0.04, respectively. Consistently, rumen lactic acid concentration was higher (P<0.01) in the AP than the GP group during both measuring periods. Rumen lactic acid concentration was lower in the second period for cows in the Y treatment, with no effect of YC feeding in period one. Cows in AP and C groups were at a greater risk of developing ruminal acidosis than GP and Y groups because the hours spent at ruminal pH below 5.8 was greater in AP than GP groups during both measuring periods and greater in C than Y groups during the second measuring period. Total volatile fatty acid (tVFA) concentration was greater in Y than C groups during both measuring periods. Protozoal count was greater in the GP than the AP group during the first measuring period with no effect in the second measuring period. Results suggest that dietary supplementation with YC during early lactation increased the ruminal pH and tVFA and reduced lactic acid while the abrupt introduction to pasture after calving reduced the ruminal pH and increased lactic acid concentration with no effect on rumen volatile fatty acids. [Copyright &y& Elsevier]

Abstract: 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 5kg commercial beef concentrates per day (controls); (ii) ad libitum grass silage plus 5kg concentrates and 250g feed grade urea per day (HE/HU); or (iii) ad libitum wheaten straw plus 250g feed grade urea and 50g 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 15mg 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 15mg luprostiol was given 12h before pessary withdrawal. They received 144mg pFSH (Folltropin®-V, Vetrepharm, Canada) given as 8 injections over 4 days commencing on day 6 of CIDR/dietary treatment. Heifers were artificially inseminated 48h 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±0.1mmol/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. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]