The present study was designed to assess progesterone profiles at the secreted (caudal vena cava) and circulating levels (jugular vein) and luteinizing hormone (LH) secretion pattern in lactating and non-lactating cows with reference to feeding. Four lactating and four non-lactating cycling Holstein cows were examined. Blood samples were collected simultaneously from the caudal vena cava (via a...

1. Four parameters of insulin metabolism were compared in catheterized lactating and non-lactating Friesian x Ayrshire dairy cows. 2. The four parameters, i.e. arterial and portal-venous concentrations of insulin, and pancreatic output and hepatic uptake of insulin, were approx. 2-, 3-, 3- and 5-fold higher respectively in the non-lactating cows than in the lactating cows in the normal fed sta...

Data of 42 balance measurements from dry and lactating Holstein cows and blood and urine samples from 24 Japanese Black cows were collected to evaluate the potential for predicting urinary nitrogen (N) excretion from plasma urea nitrogen (PUN). Similar positive correlations were obtained between N intake and apparent N absorption in dry and lactating cows. The regression equations of N intake o...

Insulin responsiveness to glucose and tissue responsiveness to insulin, using the hyperglycemic clamp and the hyperinsulinemic euglycemic clamp techniques, were measured in lactating, late pregnant, and nonpregnant, nonlactating (NPNL) beef cows. The glucose infusion rate (GIR) in the hyperglycemic clamp technique was higher (P less than .05). in lactating cows than in NPNL cows. The plateau in...

A number of reproductive parameters are altered in lactating dairy cows including: twinning rate, expression of estrus, conception rate, pregnancy loss, and incidence of anovulation. We hypothesized that the high feed consumption associated with lactation has fundamentally altered reproductive physiology due to increased metabolism of steroids. We evaluated liver blood flow and steroid metaboli...

Methane emission factors are lacking from different livestock species in various production states fed varying diets. The objectives of the present study were to measure effects of physiological state, silage type, and supplemental NDF on DMI, DM digestibility (DMD), and methane emissions of lactating and dry dairy cows using two 4 × 4 Latin squares (5-wk periods) with four lactating (114 DIM ±...

Six non-pregnant cows were allocated into 3 groups. Group 1 comprised a pair of lactating cows, whereas groups 2 and 3 each comprised a pair of non-lactating cows. The cows in groups 1 and 2 were dosed intraruminally by stomach tube with zinc oxide at 120 mg Zn per kg of bodyweight at weekly intervals for a period of 33 days. Each cow received a total of 4 doses of zinc oxide. Group 3 served as...

Compared with other nutrients, starch was the most under evaluated research topic in dairy nutrition for many years. Consequently, starch requirements for dairy cows were never established by the NRC (2001). Recently, improvements in the use of starch by lactating dairy cows garnered much interest by dairy farmers and their nutritionists, particularly over the past decade with the two-fold rise...

a field study was conducted around pb slag contaminated sites in ibadan, nigeria to assess theintake of trace metals by cows reared around the contaminated sites as indication of heavy metals contamination.levels of pb, cd, cu and zn in blood, milk and faeces were determined in 20 cows exposed to the sites and 20reference cows from uncontaminated areas. chemical analysis of pasture grasses and ...

There are approximately 2.5 million dairy cows in California. Emission inventories list dairy cows and their manure as the major source of regional air pollutants, but data on their actual emissions remain sparse, particularly for smog-forming volatile organic compounds (VOCs) and greenhouse gases (GHGs). We report measurements of alcohols, volatile fatty acids, phenols, and methane (CH4) emitt...