R.R. Grummer

Nutritional and management strategies for the prevention of fatty liver in dairy cattle

Fatty liver occurs in dairy cattle during periods of elevated blood non-esterified fatty acids (NEFAs). Elevated blood NEFAs are associated with hormonal changes at parturition and negative energy balance. Approaches for preventing fatty liver include inhibition of fatty acid mobilization from adipose tissues and altering hepatic metabolism to enhance fatty acid oxidation or export as a constituent of very low-density lipoproteins (VLDL). Nutritional and management strategies to implement these approaches have been examined. Increasing energy density of diet, either by increasing non-fiber carbohydrate or fat, has failed to prevent fatty liver. Two nutritional supplements, ruminally-protected choline and propylene glycol, have proven effective at preventing fatty liver. Choline probably enhances hepatic VLDL secretion. Propylene glycol most likely reduces fatty acid mobilization from adipose tissue. Shortening or eliminating the dry period is a management strategy that reduces the magnitude of negative energy balance after calving and triglyceride accumulation in the liver.

Effects of Dry Period Length on Milk Production and Health of Dairy Cattle

Holstein cows (n = 781) in a commercial dairy herd were used in a randomized design to evaluate 2 dry period (DP) management strategies on milk production, milk components, milk quality, colostrum quality, and incidence of metabolic disorders. Cows were randomly assigned to a traditional 55 d (T) or shortened 34 d (S) DP. Cows assigned to T were fed a low-energy diet until 34 d before expected calving at which time all cows were fed a moderate-energy transition diet until calving. Postpartum, cows assigned to T produced more milk and tended to produce more solids-corrected milk than cows on S. Treatment differences in milk and solids-corrected milk yield were accounted for by cows in their second lactation. Milk fat percentage did not differ between treatments, but milk protein percentage was greater for cows assigned to S. Colostrum quality measured as IgG concentration did not differ between management strategies. Somatic cell score and cases of mastitis were not affected by management strategy. There was a tendency for prepartum nonesterified fatty acid (NEFA) to be lower for cows assigned to T compared with S. However, postpartum, cows assigned to S had significantly lower NEFA concentrations than those assigned to T. The incidences of ketosis, retained placenta, displaced abomasum, and metritis did not differ between treatments. Postpartum energy balance, as indicated by plasma NEFA, may have been improved for cows assigned to S; there was no detectable effect on animal health.

Effect of dry period length on reproduction during the subsequent lactation

Days dry may influence reproductive measures such as days to first postpartum ovulation, days open, and pregnancy per artificial insemination (AI). Holstein cows (n = 781) from an approximately 3,000-cow commercial dairy operation were randomly assigned to 1 of 2 treatments with different targeted dry period (DP) lengths. Treatments were 1) a traditional DP of 55 d (T) or 2) a shortened DP of 34 d (S). All dry cows on T were fed a low-energy diet until 35 d before expected calving, and then at 34 d before expected calving, cows on T and S were fed a moderate energy diet until parturition. After parturition, all cows consumed the same diets that included a postcalving diet followed by a lactation diet. Actual days dry for each treatment were close to expected values, 34 and 56 d for S and T, respectively. Median days until first postpartum ovulation occurred sooner for S compared with T (35 vs. 43 d). The percentage of cows that were classified anovular by 70 d in milk (DIM) was more than 2-fold greater for cows on T than S (18 vs. 8%). Cows received AI after standing estrus starting at d 45, and the percentage of cows pregnant at 70 DIM tended to be greater for S than T; younger cows were similar (20.2 vs. 18.8%), but there was a difference between S and T in older cows (20.3 vs. 10.6%). Similarly, median days open tended to be fewer for cows on S than T. At 300 DIM, 85% of cows in both treatments were pregnant. Combining data from first and second service, pregnancies per AI were greater in older cows on S than T (32 vs. 24%). Thus, shortening the DP appeared to increase reproductive efficiency in older cows by shortening time to first ovulation, reducing numbers of anovular cows, and improving fertility. Future studies at more locations with varying reproductive management strategies are needed to confirm and provide the mechanistic basis for these results.

Variability of ovarian structures and plasma progesterone profiles in dairy cows with ovarian cysts

Weekly reproductive health examinations were performed on 46 multiparous Holstein cows from 14 to 100 d post partum. Sixteen cows developed 19 nonsimultaneous ovarian cysts, with a mean day of first detection at 34.3 +/- 4.5 d post partum and a mean duration of 31.0 +/- 4.3 d after first detection. Coccygeal blood was collected three times weekly, and plasma progesterone concentrations were determined by radioimmunoassay. Cysts were diagnosed by palpation per rectum or by ultrasonography and classified as follicular or luteal cysts; the cows were not treated. Cows with a mean plasma progesterone concentration of < 1 ng/ml from the first day of detection (Day 1) of a cyst until Day 10 were classified as having a follicular cyst, and those with a mean plasma progesterone concentration of >or= 1 ng/ml from Day 1 to Day 10 were classified as having a luteal cyst. According to this classification, 58% of the cysts were follicular and 42% were luteal. There was an overall 47% agreement between classification by palpation and by ultrasonography on Day 1 with progesterone concentration during Days 1 to 10 after detection of the cyst. Detailed graphs of progesterone concentrations and area of largest follicles or cysts and corpora lutea demonstrate the variability of ovarian structures and progesterone profiles in cystic cows. Detection of a cyst at any one time accompanied by simultaneous measurement of progesterone can lead to different diagnoses of cyst type depending on the method of classification, the presence and age of luteinized tissue in the cyst and undetected corpora lutea.

Relationships between fertility and postpartum changes in body condition and body weight in lactating dairy cows

The relationship between energy status and fertility in dairy cattle was retrospectively analyzed by comparing fertility with body condition score (BCS) near artificial insemination (AI; experiment 1), early postpartum changes in BCS (experiment 2), and postpartum changes in body weight (BW; experiment 3). To reduce the effect of cyclicity status, all cows were synchronized with Double-Ovsynch protocol before timed AI. In experiment 1, BCS of lactating dairy cows (n = 1,103) was evaluated near AI. Most cows (93%) were cycling at initiation of the breeding Ovsynch protocol (first GnRH injection). A lower percentage pregnant to AI (P/AI) was found in cows with lower (≤ 2.50) versus higher (≥ 2.75) BCS (40.4 vs. 49.2%). In experiment 2, lactating dairy cows on 2 commercial dairies (n = 1,887) were divided by BCS change from calving until the third week postpartum. Overall, P/AI at 70-d pregnancy diagnosis differed dramatically by BCS change and was least for cows that lost BCS, intermediate for cows that maintained BCS, and greatest for cows that gained BCS [22.8% (180/789), 36.0% (243/675), and 78.3% (331/423), respectively]. Surprisingly, a difference existed between farms with BCS change dramatically affecting P/AI on one farm and no effect on the other farm. In experiment 3, lactating dairy cows (n = 71) had BW measured weekly from the first to ninth week postpartum and then had superovulation induced using a modified Double-Ovsynch protocol. Cows were divided into quartiles (Q) by percentage of BW change (Q1 = least change; Q4 = most change) from calving until the third week postpartum. No effect was detected of quartile on number of ovulations, total embryos collected, or percentage of oocytes that were fertilized; however, the percentage of fertilized oocytes that were transferable embryos was greater for cows in Q1, Q2, and Q3 than Q4 (83.8, 75.2, 82.6, and 53.2%, respectively). In addition, percentage of degenerated embryos was least for cows in Q1, Q2, and Q3 and greatest for Q4 (9.6, 14.5, 12.6, and 35.2% respectively). In conclusion, for cows synchronized with a Double-Ovsynch protocol, an effect of low BCS (≤ 2.50) near AI on fertility was detected, but change in BCS during the first 3 wk postpartum had a more profound effect on P/AI to first timed AI. This effect could be partially explained by the reduction in embryo quality and increase in degenerate embryos byd 7 after AI in cows that lost more BW from the first to third week postpartum.

Effect of rumen-protected niacin on lipid metabolism, oxidative stress, and performance of transition dairy cows

The objective of this study was to evaluate the effect of a rumen-protected niacin product (RPN; 65% nicotinic acid; NiaShure, Balchem Corp., New Hampton, NY) on lipid metabolism, oxidative stress, and performance of transition dairy cows. Thirty nonlactating multiparous Holstein cows in late gestation were paired according to expected calving date and randomly assigned to 12 g/cow per day of RPN product or to an unsupplemented control (CON) diet. Treatment diets were fed from 21 d before expected calving through 21 d after parturition. Blood samples were taken on d -21, -14, -7, 1, 7, 14, and 21 relative to calving for plasma nonesterified fatty acid (NEFA), β-hydroxybutyrate (BHBA), glucose, and superoxide dismutase (SOD) analyses. Liver samples were taken by biopsy on d 1 and 21 relative to calving for triglyceride (TG) analysis. Data were analyzed for a randomized complete block design with repeated measures. Pre- and postpartum dry matter intake, milk yield, and protein were unaffected by treatment. Milk fat percentage (5.08 vs. 4.44%) and somatic cell score (3.93 vs. 2.48) were reduced for RPN. Treatment × time interactions were observed for energy-corrected milk (ECM) and fat-corrected milk (FCM) yields; RPN reduced ECM and FCM yields by 8.5 and 8.9 kg/cow per day, respectively, in the first week of lactation. Although body weight and condition score decreased during the experimental period, no differences due to treatment were observed. However, calculated postpartum energy balance tended to be improved for RPN because of the reduction in ECM yield. Time and treatment × time effects were observed for plasma NEFA. On d 1 postpartum, NEFA reached 1,138±80 μEq/L for CON compared with 698±80 μEq/L for RPN. Cows supplemented with RPN tended to have lower plasma NEFA concentrations than CON cows on d 7 and 14 postpartum. Plasma BHBA, glucose, and SOD and liver TG concentrations were unaffected by treatment. In conclusion, supplementation with 12 g/cow per day of the RPN product provided a bioavailable source of niacin that modified lipid metabolism but did not affect milk yield over the first 3 wk of lactation or oxidative stress of transition dairy cows.

Antilipolytic and lipolytic effects of administering free or ruminally protected nicotinic acid to feed-restricted Holstein cows

The objectives were to determine effects of 12 hourly infusions of different quantities of nicotinic acid (NA) on plasma nonesterified fatty acid (NEFA; experiment 1) and whether longer (108 h) continuous infusions of NA could induce sustained reductions of plasma NEFA (experiment 2) in nonlactating, nongestating Holstein cows that were feed restricted. Experiment 1 was a 5×5 Latin square with 6-d periods and 9 recovery days between each period. Each period consisted of 5 d of partial feed restriction to increase plasma NEFA concentration. Treatments were abomasal infusions of 0, 0.25, 0.5, 1, or 3 mg of NA/h per kilogram of body weight (BW), infused as hourly boluses for 12 h, starting 4 d after initiation of partial feed restriction. Plasma NEFA was decreased for the highest dose: from 448 μEq/L to 138±75 μEq/L at 1 h after the first bolus of 3mg of NA/h per kilogram of BW. This initial reduction in plasma NEFA concentration was followed by an increase in concentration at 2, 3, and 4 h relative to initiation of infusions. Plasma NEFA then decreased to 243 μEq/L 6h after initiation of treatments and remained low until termination of infusions. A rebound in plasma NEFA concentration occurred at 3 and 4 h after termination of infusion for cows that received 3 mg of NA/h per kilogram of BW. Experiment 2 was a 5×5 Latin square with 7-d periods and 9 recovery days between each period. Each period consisted of 5 d of partial feed restriction to increase plasma NEFA concentration. Treatments were continuous abomasal infusion of 0, 0.5, 1, or 3 mg of free NA/h per kilogram of BW for 4.5 d starting at feed restriction or 0.5 mg of NA/h per kilogram of BW infused directly into the rumen in a form protected from microbial degradation. The ruminal administration of protected NA was initiated 2 d before abomasal infusions and initiation of feed restriction to establish steady postruminal delivery of NA by start of abomasal infusions. Plasma NEFA was approximately 70 μEq/L before initiation of feed restriction and increased to 509, 587, 442, 850, and 108 μEq/L at 4.5 d for cows that received 0, 0.5 (protected NA), 0.5 (free NA), 1, and 3 mg of NA/h per kilogram of BW, respectively. An antilipolytic response was achieved with the highest abomasal dose, which maintained plasma NEFA concentration lower than the control group. An increase in plasma NEFA concentration was observed after termination of infusions for cows that received 1 and 3 mg of NA/h per kilogram of BW. Plasma NEFA was 1,900 μEq/L at 4h after termination of infusion for cows receiving 1 mg of NA/h per kilogram of BW and 1,360 μEq/L at 5h after termination of infusion for cows receiving 3 mg of NA/h per kilogram of BW. In nongestating, nonlactating cows it is unlikely that a dose of NA exists that will reduce plasma NEFA concentration and prevent the rebound that occurs following termination of NA administration.

Effects of Abomasal Infusion of Linseed Oil on Responses to Glucose and Insulin in Holstein Cows

The objective was to study the effects of abomasal infusion of linseed oil, a source rich in n-3 C18:3, on whole-body response to insulin (experiment 1) and on insulin antilipolytic effects during feed restriction (experiment 2). In experiment 1, eight nonlactating, non-gestating cows were assigned to a crossover design, fed to meet maintenance requirements, and infused abomasally with either linseed oil (LIN) or tallow (TAL) at a rate of 0.54 g/kg of body weight per d for 5.5 d. Infusions were performed every 8 h during the first 3 d of each period and every 4 h thereafter. Intravenous glucose tolerance tests (IVGTT) were performed on d 5 of each period, followed by i.v. insulin challenges (IC) 12 h later. In experiment 2, six nonlactating, nongestating cows were assigned to a replicated 3 x 3 Latin square design. The experimental protocol included a water (WTR) treatment and feeding was suspended on d 3, leading to 50 and 62 h of feed restriction before IVGTT and IC, respectively. Clearance of glucose during IVGTT and IC was not affected by treatments in either experiment. However, LIN had an insulin sensitizing effect in experiment 1, because a lower insulin concentration led to the same clearance of glucose as TAL. In experiment 1, plasma nonesterified fatty acid (NEFA) concentration was low, reflecting a postprandial state, but NEFA was greater for LIN than TAL during IVGTT (108 vs. 88 +/- 4 microEq/L) and IC (133 vs. 83 +/- 9 microEq/L). In experiment 2, insulin concentrations during IVGTT did not differ across treatments. Basal plasma NEFA concentration before IVGTT tended to be greater for LIN than for TAL (612 vs. 508 microEq/L). Plasma NEFA clearance rate during IVGTT was greater for LIN than for TAL (2.8 vs. 2.5%/min), leading to a shorter time to reach half NEFA concentration (25 vs. 29 min) and greater absolute value of NEFA response area under the curve [AUC; -64,150 vs. -46,402 (microEq/L) x 180 min]. Data suggest that LIN enhanced the antilipolytic effects of insulin. Yet, other factors could have been involved because plasma NEFA concentration before IVGTT was 104 muEq/L greater for LIN than TAL for unknown reasons.

Apolipoprotein composition of bovine lipoproteins isolated by gel filtration chromatography

1. Bovine lipoproteins were isolated from plasma by gel filtration and apolipoprotein composition determined by SDS-polyacrylamide gel electrophoresis. 2. Bovine triglyceride-rich lipoproteins contained a novel low mol. wt protein Mr = 22,000 and low mol. wt proteins that may be analogous to non-ruminant apolipoproteins A-I, A-IV, and E. 3. Apolipoprotein C appeared to be a minor constituent of bovine triglyceride-rich lipoproteins. 4. Triglyceride-rich lipoproteins contained two high mol. wt proteins of approx. Mr = 220,000 and 290,000. 5. The predominant bovine low density lipoprotein apolipoprotein was approx. Mr = 290,000, however, greater then 25 proteins were often observed between Mr = 110,000 and 370,000. 6. Bovine high density lipoprotein contained proteins analogous to apolipoprotein A-I and C apolipoproteins. 7. Differences in apolipoprotein profiles between non-lactating and lactating cows were not apparent.

In vitro and in vivo analysis of fatty acid effects on metabolism of 17β-estradiol and progesterone in dairy cows.

Some studies have reported improved reproductive performance with dietary fat supplementation. This study examined effects of fatty acids with different lengths, or desaturation, or both, on metabolism of estradiol (E2) and progesterone (P4) in bovine liver slice incubations (experiments 1 and 2) and in vivo (experiment 3). In experiment 1, effects of fatty acids C16:0 (palmitic acid), C16:1 (palmitoleic acid), C18:1 (oleic acid), and C18:3 (linolenic acid) were evaluated at 30, 100, and 300 microM on P4 and E2 metabolism in vitro. In experiment 2, stearic acid (C18:0) and C18:3 were evaluated in the same incubation conditions. In experiment 1, all of the fatty acids had some significant inhibitory effect on metabolism of P4, E2, or both (300 microM C16:0 on E2; 100 microM C16:1 on E2; 300 microM C16:1 on both P4 and E2; 300 microM C18:1 on P4; and 100 and 300 microM C18:3 on both P4 and E2). In experiment 2, C18:3 (100 and 300 microM) but not C18:0 decreased P4 and E2 metabolism. Overall, the most profound increase (approximately 60%) in half-life of P4 and E2 was observed with incubations of 300 microM C18:3 in both in vitro experiments. Based on these in vitro results, in experiment 3 linseed oil (rich in C18:3) was supplemented into the abomasum and acute effects on metabolism of E2 and P4 were evaluated. Cows (n=4) had endogenous E2 and P4 minimized (corpus luteum regressed, follicles aspirated) before receiving continuous intravenous infusion of E2 and P4 to analyze metabolic clearance rate for these hormones during abomasal infusion of saline (control) or 70 mL of linseed oil every 4h for 28h. Linseed oil infusion increased C18:3 in plasma by 46%; however, metabolic clearance rate for E2 and P4 were similar for control cows compared with linseed-treated cows. Thus, in vitro experiments indicated that E2 and P4 metabolism can be inhibited by high concentrations of C18:3. Nevertheless, in vivo, linseed oil did not acutely inhibit E2 and P4 metabolism, perhaps because insufficient C18:3 concentrations (increased to approximately 8 microM) were achieved. Further research is needed to determine the mechanism(s) of fatty acid inhibition of P4 and E2 metabolism and to discover practical methods to mimic this effect in vivo.