Urine Calcium But Not Plasma Calcium or Urine Hydroxyproline Is Increased by a Systemic Acidosis in the Dairy Cow

Eight non-lactating, pregnant Holstein-Friesian cows were allocated to two treatments and individually offered diets differing in dietary cation-anion difference. Decreasing the dietary cation-anion difference reduced the urine pH within hours of anionic salt supplementation. Plasma calcium concentration was unaffected by dietary cation-anion difference but urine calcium concentration was significantly increased within 10 days of including anionic salts in the diet. Faecal calcium concentration was significantly reduced, indicating increased calcium absorption. Dietary calcium concentration or dietary cationanion difference did not significantly affect urinary hydroxyproline

Dry Matter Intake of Periparturient Cows on a Fresh Pasture/Pasture-Hay Diet

Reports of the depression in dry matter intake in the periparturient period have been inconsistent and little dry matter intake data is available for an all-forage diet prior to calving. Data to examine intake depression prior to calving was obtained from two experiments. In experiment 1, sixteen non-lactating, periparturient cows ate 1.3% of pre-calving body weight of grass-hay and freshly cut grass for two weeks pre-calving (restricted). Experiment 2 comprised thiry-six cows that ate 1.6% of pre-calving body weight of grass-hay and freshly cut grass for the final two weeks of pregnancy (ad libitum). Individual dry matter intakes were recorded for 14 days pre-calving. Intake pre-calving was not depressed, irrespective of feeding level, until two days pre-calving. This suggests that when an all-forage diet is fed pre-calving, increasing the energy density of the diet to compensate for a depression in dry matter intake may not be necessary

A COMPARATIVE STUDY OF OVARIAN FOLLICLE DYNAMICS AND IGF-I CONCENTRATION DURING AN OESTRUS CYCLE IN TWO GENOTYPES OF LACTATING HOLSTEIN-FRIESIAN COWS OFFERED PASTURE OR A TOTAL MIXED RATION

SUMMARY The objective was to characterize ovarian follicle dynamics and changes in systemic concentration of IGF-I during an oestrous cycle. The four treatment groups were New Zealand Holstein-Friesian (NZHF) Pasture (n=6) and TMR (n=10) and Overseas Holstein-Friesian (OSHF) Pasture (n=7) and TMR (n=6). From Day 17 following a synchronised oestrus, blood samples were collected and ovarian structures were monitored by ultrasound until the end of the subsequent cycle (ovulation). Every cow in the study had two waves of follicle development. NZHF cows had shorter (P<0.05) oestrous cycles than OSHF cows. Genotype or feeding system had no effect on emergence, selection, growth rate, maximum diameter or duration of dominance of the anovulatory or ovulatory follicles. Mean (±se) plasma IGF-I concentrations were higher (57.5±3.3 v 37.1±3.9 ng/mL; P<0.01) for cows offered TMR compared to pasture and also for NZHF compared to OSHF cows (56.3±3.6 v 38.3±3.6 ng/mL; P<0.01). In conclusion, this study has identified substantial differences in circulating IGF-I concentrations between dairy cow genotypes and between the feeding systems under which such cows are managed