Metabolic blood profile of beef heifers during oestrous and non-oestrous states.

Haematological metabolic profiles in heifers could contribute to the development of proxies for oestrous detection and provide clues to further characterize biological changes during oestrus. One hundred and seven beef heifers were observed for oestrous behaviour twice daily for 124 days. Feed intake and productive performance (body weight and composition) traits were measured, and feed efficiency was determined using residual feed intake (kg DM/day). Blood plasma samples were collected when signs of oestrus were observed and every 30 ± 2 days. Heifers were considered in oestrus (n = 71) when plasma progesterone concentrations were <0.6 ng/ml. Least square means of blood metabolic parameters were compared between oestrous and non-oestrous states and within oestrous groups according to performance traits and age. Heifers in oestrus exhibited higher concentrations of alkaline phosphatase, aspartate aminotransferase (AST), beta-hydroxybutyric acid, creatine kinase (CK) and triiodothyronine (T3) than heifers in non-oestrus. Heifers in oestrus revealed lower osmolality and concentrations of calcium, sodium and total protein than during non-oestrus. Younger (and smaller) heifers had greater concentrations of CK, gamma-glutamyl transferase (GGT), glucose and sodium than the older heifers. Heifers with lower fatness had increased osmolality and concentrations of cholesterol, CK, phosphorus, sodium and reduced T3 levels. Feed efficient heifers had greater levels of AST, cholesterol and GGT than inefficient heifers. Blood plasma parameters may be complementary to oestrous detection upon further validation; effects of age, feed efficiency, body size and body composition should be considered to optimize this haematological assessment.

Effects of pasture versus confinement and marine oil supplementation on the expression of genes involved in lipid metabolism in mammary, liver, and adipose tissues of lactating dairy cows.

Research was conducted to evaluate the effects of management system (MS), marine lipid supplementation (LS), and their interaction on the relative mRNA abundance of 11 genes involved in lipid synthesis in mammary, liver, and subcutaneous adipose tissues in lactating dairy cows. These genes included those involved in FA uptake (LPL), de novo FA synthesis (ACACA, FASN), FA desaturation (SCD1, FADS1, FADS2), and transcriptional regulation of lipogenesis (SREBF1, SCAP, INSIG1, THRSP, and PPARG). Forty-eight peripartal Holstein cows were blocked by parity and predicted calving date and assigned to either a pasture (n=23) or confinement (n=25) system. Within each system, cows were allocated randomly (7-9 cows per treatment) to a control (no oil supplement) or 1 of 2 isolipidic (200 g/d) supplements, fish oil (FO) or microalgae (MA), for 125 ± 5 d starting 30 d precalving. The experiment was conducted as a split-plot design, with MS being the whole plot treatment and LS as the subplot treatment. At 100 ± 2 DIM, 4 cows from each treatment combination (24 cows in total) were euthanized and tissue samples were collected for gene expression analysis. No interactions between MS and LS were observed regarding any of the variables measured in this study. Milk production (34.0 vs. 40.1 kg/d), milk fat (1.10 vs. 1.41 kg/d), protein (0.95 vs. 1.22 kg/d), and lactose (1.56 vs. 1.86 kg/d) were lower for pasture compared with confinement. The effect of LS on milk production and milk composition (yields and contents) was significant only for milk fat content that was reduced with MA compared with FO (3.00 vs. 3.40%) and the control (3.56%). The mammary mRNA abundance of PPARG (-32%) and FASN (-29%) was lower in grazing compared with confined cows, which was accompanied by reduced (-43%) secretion of de novo synthesized fatty acids in milk. Grazing was associated with reduced expression of ACACA (-48%), FASN (-48%), and THRSP (-53%) in subcutaneous adipose tissues, which was consistent with the lower body condition score (i.e., lower net adipose tissue deposition) in grazing compared with confined cows. Feeding either FO or MA downregulated hepatic expression of FASN, SCD1, FADS2, and THRSP. The reduced secretion of de novo synthesized fatty acids in milk of grazing cows compared with confined cows might be related in part to the downregulation of genes involved in lipid synthesis, and that LS have tissue-specific effects on expression of genes involved in lipid metabolism, with liver being the most responsive tissue.

Effect of supplementation with fish oil or microalgae on fatty acid composition of milk from cows managed in confinement or pasture systems.

The objective of this study was to examine the interaction between lipid supplement (LS) and management system (MS) on fatty acid (FA) composition of milk that could affect its healthfulness as a human food. Forty-eight prepartal Holstein cows were blocked by parity and predicted calving date and deployed across pasture (PAS; n=23) or confinement (CONF; n=25) systems. Cows within each system were assigned randomly to a control (no marine oil supplement) or to 1 of 2 isolipidic (200 g/d) marine oil supplements: fish oil (FO) or microalgae (MA) for 125 ± 5 d starting 30 d precalving. The experiment was conducted as a split-plot design, with MS being the whole-plot treatment and LS as the subplot treatment. Cows were housed in a tie-stall barn from -30 until 28 ± 10 d in milk (DIM) and were fed total mixed rations with similar formulations. The PAS group was then adapted to pasture and rotationally grazed on a perennial sward until the end of the experiment (95 ± 5 DIM). Milk samples were collected at 60 and 90 DIM for major components and FA analyses. Milk yield (kg/d) was lower in PAS (34.0) compared with CONF (40.1) cows. Milk fat percentage was reduced with MA compared with FO (3.00 vs. 3.40) and the control (3.56) cows. However, milk fat yield (kg/d) was not affected by lipid supplements. Compared with CONF, PAS cows produced milk fat with a lower content of 12:0 (-38%), 14:0 (-28%), and 16:0 (-17%), and more cis-9 18:1 (+32%), 18:3 n-3 (+30%), conjugated linoleic acid (CLA; +70%) and trans 18:1 (+34%). Both supplements, regardless of MS, reduced similarly the milk fat content of 16:0 (-12%) and increased CLA (+28%) and n-3 long-chain polyunsaturated FA (n-3 LC-PUFA; +150%). Milk fat content of trans 18:1 (trans-6 to trans-16) was increased with FO or MA, although the effect was greater with MA (+81%) than with FO (+42%). The interaction between MS and LS was significant only for trans-11 18:1 (vaccenic acid, VA) and cis-9,trans-11 CLA (rumenic acid). In contrast to CONF, feeding FO or MA to PAS cows did not increase milk fat content of VA and rumenic acid. We concluded that compared with CONF, milk from PAS cows had a more healthful FA composition. Feeding either FO or MA improved n-3 long-chain polyunsaturated FA and reduced levels of 16:0 in milk fat, regardless of MS, but concurrently increased the trans 18:1 isomers other than VA, at the expense of VA, particularly in grazing cows.

Effect of feeding fresh forage and marine algae on the fatty acid composition and oxidation of milk and butter.

This study evaluated the effects of feeding fresh forage either as pasture plus a concentrate (PAS) or as a silage-based total mixed ration (TMR), combined with either a ruminally inert lipid supplement high in saturated fatty acids (-) or a ruminally protected microalgae containing 22 g of docosahexaenoic acid (DHA)/100 g of fatty acids (+) on the fatty acid (FA) composition and oxidation of milk and butter. For the 8 mid-lactation Holstein cows in this study, milk yield was not significantly affected by treatment, averaging 32.3 ± 1.28 kg/d. Milk fat content was higher for PAS⁻, averaging 5.05 compared with 4.10 ± 0.17% for the mean of other treatments, and was significantly depressed with microalgae supplementation (3.97 vs. 4.69 ± 0.17%). The saturated fatty acid level in the milk of cows fed TMR⁻ was significantly higher than that of the other treatments (66.9 vs. 61.2 g/100 g of FA). The level of monounsaturated FA was lowered by feeding TMR⁻ (27.4 vs. 32.0 g/100 g of FA), whereas levels of polyunsaturated FA were elevated by feeding PAS+ compared with the mean of the other treatments (6.54 vs. 5.07 g/100 g of FA). Feeding the rumen-protected microalgae increased the DHA content of milk more than 4-fold (0.06 to 0.26 g/100g of FA) with the PAS treatment. The conjugated linoleic acid content of milk was highest for PAS+ compared with the other treatments (4.18 vs. 3.41 g/100g of FA). In general, the fatty acid composition of butter followed that of milk. Overall, feeding the TMR supplemented with the rumen-protected microalgae increased the levels of volatile products of oxidation in milk and butter. No effect of forage type or microalgae supplementation was observed on the oxidative stability or antioxidant capacity of milk, although the oxidative stability of butter exposed to UV was reduced with microalgae supplementation, particularly with TMR, as assessed by using the ferric reducing ability of plasma assay.

Productivity of grazing Holstein cows in Atlantic Canada.

The feasibility and profitability of management-intensive grazing (MIG) in Atlantic Canada was studied. Productivity of MIG plus concentrate (1 kg:3 kg of milk) was compared with that of confinement feeding (Confined) using haylage (1996) or corn silage (1997) as 50% of dry matter (DM) in a total mixed ration (TMR). Each year, two groups of 10 Holsteins were used. In 1996, pasture CP content increased from 15.2 to 18.0% of DM, while those of acid detergent fiber (ADF) and neutral detergent fiber (NDF) decreased (33.6 to 23.8%, and 55.6 to 35.4%, respectively) between July 10 and August 28. In 1997, pasture crude protein (CP) content decreased from 30.0 to 15.7%, while ADF and NDF increased (24.9 to 35.8% and 53.5 to 67.4%, respectively) from June 16 to July 14. Because pasture biomass was reduced by winter-kill followed by drought in 1997, MIG cows were supplemented with TMR. Estimated pasture DM intakes ranged from 14.2 to 18.1 kg/d per cow. Milk yields averaged 29.5 and 30.4 +/- 0.43 kg/d in 1996 and 32.5 and 31.8 +/- 0.61 kg/d in 1997 for Confined and MIG cows, respectively. In 1996, the dietary treatment x time interaction was significant. Cows in MIG had higher yields than those in Confined later in the trial, while fat and CP concentrations were usually lower in milk from MIG cows. Lower body weights resulted with MIG. Few differences between production systems were significant in 1997. Milk revenue (Canadian $/d) from Confined cows was higher (14.03 vs. 13.77 in 1996 and 16.10 vs. 15.39 in 1997), but partial profitability of the MIG system was marginally greater in both years.

Ruminally protected lysine and methionine for lactating dairy cows fed a diet designed to meet requirements for microbial and postruminal protein.

Dairy cows, 20 at each of two sites, were used to determine responses to ruminally protected Lys and Met in a full lactation study. Cows were fed corn silage twice daily for ad libitum intake and a concentrate four times daily in proportion to milk production. At Truro, cows were fed 2.7 kg/d of alfalfa and timothy hay DM at 0600 and at 1500 h. At Fredericton, cows were fed 2.7 kg of timothy silage DM at 0600 h and 2.7 kg of alfalfa hay DM at 1500 h. Diets were designed to meet, but not to exceed, recommendations for ruminally degradable CP and intestinally digestible protein. Ten cows at each site were fed ruminally protected L-Lys.HCl (19 g/d) and DL-Met (6.5 g/d). Cows fed AA at each site produced more milk, lactose, protein, and fat; milk protein and fat percentages were also higher. No time x treatment interactions occurred for any production parameter. In spite of similar production responses between sites, cows fed AA consumed more DM at Truro, but those at Fredericton did not. Thus, gross efficiency of utilization of dietary N for milk N was increased with AA at Fredericton but not at Truro. However, considering the increased intake of CP by cows fed AA at Truro, an event that would have been expected to depress efficiency of utilization of dietary N, the lack of difference at Truro between treatments can be interpreted as an improvement, relative to expectations, because of AA feeding. High producing dairy cows fed a diet that was adequate in CP responded to ruminally protected Lys and Met primarily with increased production of milk protein and fat throughout the full lactation.

Characterization of acid-base disturbances and effects on calcium and phosphorus balances of dietary fixed ions in pregnant or lactating does.

Effects of fixed cation-anion balance on acid-base status and calcium and phosphorus balances were examined. Pregnant and lactating goats were fed a diet of alfalfa hay, concentrate and minerals to vary the cation-anion balance [meq sodium (Na) + meq potassium (K)-meq chloride (Cl)]/100 g diet dry matter (DM) over the range found in ruminant feeds. Small but significant effects on ruminal pH, fermentation and dilution rate were observed. Metabolic acid-base status of pregnant and lactating goats was normal when (Na + K - Cl) balance was 40 to 50 meq/100 g DM. The other treatments drastically altered plasma electrolyte concentrations, causing metabolic acid-base disturbances and profound changes in calcium and phosphorus metabolism. Subclinical hypernatremic, hypochloremic metabolic alkalosis was induced by a dietary fixed cation excess (Na + K - Cl) of greater than 85 meq/100 g DM (typical of buffered, alfalfa diets) and caused hypocalciuria, diminished calcium and phosphorus absorption, and possibly diminished dietary calcium absorption and resorption of calcium from bone. Subclinical hyperchloremic, hyponatremic metabolic acidosis from a diminished dietary fixed cation-anion balance (Na + K - Cl) of less than 10 meq/100 g DM (typical of nonbuffered corn silage or grain diets) caused hypercalciuria, enhanced calcium and phosphorus absorption and apparently enhanced calcium resorption from bone. Apparent effects on absorption and resorption depended on calcium and phosphorus intakes. Alterations in goats performance were not demonstrable. Dietary excesses of fixed cations over anions (meq Na + K - Cl/100 g diet DM greater than 50) cause metabolic alkalosis in ruminants, whereas fixed anion excesses (meq Na + K - Cl/100 g diet DM less than 40) cause metabolic acidosis. Content of electrolytes in diets should be reported in all nutrition trials with ruminants for assessment of metabolic acid-base status.

Effects of acid-base disturbances caused by differences in dietary fixed ion balance on kinetics of calcium metabolism in ruminants with high calcium demand.

Effects of subclinical metabolic acid-base disturbances, caused by dietary fixed ion imbalances on kinetics of calcium (Ca) metabolism were examined in eucalcemic caprine does (period 1) and does during simulated lactational Ca loss (period 2). In both experiments, Ca balance data and serial blood, fecal and urine samples were collected after an iv injection of 45Ca. In period 2, lactational Ca loss was simulated by continuous infusion of ethylene glycol-bis (beta-amino ethyl ether)N,N,N'N'-tetraacetic acid (EGTA) to standardize the loss of Ca among goats. The data were fit to a four-compartment model of Ca metabolism. In period 1, fixed anion excess, [sodium + potassium - chloride] = -2 meq/100 g diet dry matter (ANEX) increased urinary Ca excretion relative to fixed cation excess, [sodium + potassium - chloride] = 71 meq/100 g diet dry matter (CATEX). Consequently, rates of Ca absorption and resorption were elevated in goats made acidotic by dietary fixed anion excess. During period 2 (EGTA infusion), urinary Ca loss was elevated to similar levels in goats fed ANEX and CATEX, but Ca absorption remained higher in goats fed ANEX. Consequently, size of the exchangeable Ca pool, accretion rate and balance across bone were higher in these goats. Fixed anion excesses (found in corn silage and grains) cause subclinical metabolic acidosis, which elevates rates of Ca absorption but does not affect size of the exchangeable Ca pool. Fixed cation excesses (associated with diets containing alfalfa and buffers) cause subclinical metabolic alkalosis, which diminishes Ca absorption and urinary Ca excretion. Acidosis-induced hypercalciuria is the metabolic cost of maintaining high prepartum Ca absorption rates and high flux of Ca through the exchangeable Ca pool that may aid in adjustment to sudden Ca losses at parturition.

Effect of sodium bicarbonate addition to alfalfa hay-based diets on digestibility of dietary fractions and rumen characteristics.

Three trials were to evaluate effects of sodium bicarbonate in alfalfa hay-based diets. In Experiment 1, four Jersey cows were fed diets of 40:60 chopped alfalfa hay:grain with either 0, .25, .5, and .75% sodium bicarbonate in a 4 X 4 Latin square digestion trial. Dry matter and fiber digestion were unaffected. Volatile fatty acids of ruminal fluid and milk fatty acids were not different. In Experiment 2, two rumen fistulated cattle were fed diets of Experiment 1 for changes of ruminal fluid characteristics at -1, 2, 4, and 8 h postfeeding. Volatile fatty acids of ruminal fluid and hydrogen ion concentration were not different across time with sodium bicarbonate. In Experiment 3, four Holstein cows with rumen cannulae were fed diets of 30:70 chopped alfalfa hay:grain with 0, .4, .8, and 1.2% sodium bicarbonate in a 4 X 4 Latin square. Dry matter and fiber digestion were unaffected. Ruminal fluid samples were collected at -1, 3, 6, and 9 h postfeeding. Volatile fatty acids were different only at 6 h with 0 and 1.2% sodium bicarbonate diets displaying lower concentrations. Rate of increase of hydrogen ion concentration was greater for diets containing 0 and .4% compared with .8 and 1.2% sodium bicarbonate between -1 and 6 h. Milk fatty acid composition, ruminal liquid dilution rate, and dry matter disappearance from nylon bags suspended in the rumen were not affected by sodium bicarbonate.