Responses of primiparous and multiparous Holstein cows to additional energy from fat or concentrate during summer.

Supplemental fat has been advocated for use during hot weather and often increases milk yield of cows past peak production when energy intake should not be limiting. Relative responses of primiparous and multiparous cows to supplemental fat or isocaloric addition of concentrates under hot weather conditions have not been determined. Nine multiparous and nine primiparous Holstein cows (154 and 167 d in milk, respectively) were used in a replicated 3 x 3 Latin square design with 28-d periods. Diets were 1) control (35% alfalfa silage, 25% corn silage, and 40% concentrate, dry matter [DM] basis); 2) control plus 3% fat (HF); and 3) high concentrate ([HC] 15% alfalfa silage, 25% corn silage, and 60% concentrate). Diets were isonitrogenous; diets HF and HC were isocaloric (1.60 Mcal of net energy for lactation [NE(L)] per kilogram DM) and higher energy than the control (1.52 Mcal/kg). No parity x diet interactions approached significance. DM intake (DMI) was greater when cows were fed HC than when they were fed HF (21.0, 20.1, and 21.3 kg/d for control, HF, and HC, respectively); intake of NE(L) tended to be increased only for HC. Milk yield was increased by higher-energy diets, but milk fat content was decreased. Milk total protein content was decreased by HF and increased by HC. Yield of solids-corrected milk (SCM) was not different among diets. Efficiency of milk production, expressed either as total milk solids yield per kilogram of DMI or as kilograms of SCM per megacalorie of NE(L) intake, was greater for HF than for HC. Plasma glucose was higher after feeding for cows fed HC; plasma nonesterified fatty acids were greater for HF. Respiration rate and rectal temperature were greater for HC than for HF. Regardless of parity, increased energy density from either fat or concentrate increased milk yield in midlactation cows, but diets caused energy to be partitioned differently among milk components and body storage. Supplemental rumen-active fat had modest advantages over additional starch-based concentrate during summer heat conditions.

Ruminal and total tract digestibilities in steers fed diets containing liquefied or prilled saturated fatty acids.

We studied the effects of the addition of liquefied vs prilled mostly saturated fatty acids (FA) to the concentrate portion of total mixed diets on ruminal and total tract digestibilities. Four Holstein steers (270 +/- 23 kg) fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square design with 21-d periods. Diets contained (DM basis) 30.0% corn silage, 22.2% chopped alfalfa hay, 25.0% ground shelled corn, 12.5% soybean meal, and 5% of one of the following fat sources: 1) prilled FA (PFA), 2) choice white grease (triglycerides) added in liquid form (LTG), 3) 2.5% PFA + 2.5% LTG, or 4) 2.5% liquefied PFA (LFA) + 2.5% LTG. Ad libitum OM intake was not different (P > .10) among diets (mean 7.8 kg/d). Ruminal digestibilities of OM (35.7, 39.9, 42.2, and 37.3% for Diets 1 to 4, respectively) were greatest (P < .10) for the combination of PFA + LTG and lowest for PFA alone. Ruminal digestibilities of NDF, ADF, and starch did not differ (P > .10) among diets. Total tract digestibilities of OM, NDF, and ADF were greater (P < .10) for the diet containing LTG alone than for the diet containing LFA + LTG because of trends for greater postruminal digestibilities. The LFA + LTG diet resulted in a greater proportion of acetate and lower proportion of propionate in ruminal fluid than PFA alone (P < .10). The acetate:propionate ratio (3.53, 2.96, 3.10, and 2.89 for Diets 1 to 4, respectively) was lower (P < .05) for LFA + LTG or LTG alone than for PFA alone. Postruminal and total tract digestibilities of total FA (66.0, 76.0, 71.2, and 68.9% for Diets 1 to 4, respectively) were lower (P < .05) for PFA than for other diets. Addition of saturated FA in liquid form resulted in digestibilities and ruminal effects similar to the same saturated FA added in prilled form.

Supplemental fat and nicotinic acid for Holstein cows during an entire lactation.

The objectives of this experiment were to determine long-term responses to supplemental fat (from whole soybeans and liquid animal fat) and to determine whether the supplementation of nicotinic acid would enhance milk protein content or yield. From wk 4 through 43 postpartum, 44 multiparous Holstein cows (10 to 12 per treatment) were assigned to one of four dietary treatments: 1) control, 2) control plus 12 g/d of nicotinic acid, 3) supplemental fat, and 4) supplemental fat plus 12 g/d of nicotinic acid. The dry matter intake of cows did not differ among dietary treatments. Yields of milk, solids-corrected milk, and 3.5% fat-corrected milk were increased by nicotinic acid; the yield of fat-corrected milk during wk 4 to 25 was increased by supplemental fat. Contents of crude protein (CP) and true protein in milk were less for cows fed diets supplemented with fat or nicotinic acid; casein content was decreased by nicotinic acid. Intake of net energy for lactation was greater for cows fed supplemental fat; energy balance was greater during wk 4 to 25 for cows fed diets supplemented with fat. Body condition score and body weight were less when nicotinic acid was added to the control diet than when it was added to the diet supplemented with fat. Supplemental fat increased the concentration of nonesterified fatty acids (NEFA) in plasma; nicotinic acid increased NEFA when it was added to the control diet but decreased NEFA when it was added to the diet supplemented with fat. Nicotinic acid did not prevent the decrease in milk CP content that was induced by dietary fat, but it did increase milk yield and tended to increase the yield of milk CP.

Nutrition during the dry period and hepatic lipid metabolism of periparturient dairy cows.

From dry-off until 7 d before expected parturition date, 30 Holstein cows were fed a low energy diet (control) to maintain body condition or high energy diets (high fat or isocaloric high grain) to attempt to increase body condition. After parturition, all cows were fed a common lactation diet. Body condition was unchanged for cows fed control or high grain diets, but was decreased for cows fed the high fat diet because DMI was decreased. Cows fed the high fat diet during the dry period had decreased triglyceride accumulation in the liver at 1 d postpartum, which was accompanied by lowered plasma NEFA, increased peroxisomal beta-oxidation of palmitate by liver homogenates, and decreased esterification of palmitate by liver slices. During the last 3 wk prepartum, cows fed the high fat diet had lower glycogen and higher acid-soluble carnitine in liver, higher concentrations of NEFA and bST in plasma, higher ratio of triiodothyronine to thyroxine in plasma, and lower concentrations of insulin and thyroxine in plasma than did cows fed the high grain diet. After parturition, cows fed the high fat diet during the dry period had decreased percentage and production of milk fat; differences among treatments were not significant for DMI, body condition, milk production, or milk protein. Periparturient lipid metabolism was altered significantly in cows fed a high fat diet during the dry period, although diet composition and nutrient intakes were confounded.

Dose response of dairy cows to abomasal administration of four amounts of L-carnitine.

Four Holstein cows were used in a 4 x 4 Latin square design with 21-d periods to determine the response to increasing amounts of L-carnitine infused into the abomasum. During d 1 to 7 of each period, cows were abomasally infused with 4 L/d of water; during the remainder of each period, 0, 3, 6, or 12 g/d of carnitine dissolved in 4 L of water were infused continuously into the abomasum. The DMI, milk yield, and milk composition were not affected by carnitine infusion. Apparent digestibilities of DM, OM, CP, ADF, NDF, and energy decreased linearly, and fatty acid digestibility tended to decrease linearly, when up to 12 g/d of carnitine were infused. Balances of energy and N generally were unaffected by carnitine infusion. The concentrations of carnitine in plasma and urine increased linearly, and that in milk increased quadratically, as the amount of infused carnitine increased; the concentrations of carnitine in plasma and milk appeared to be maximized when 6 g/d of carnitine were infused. Total carnitine excreted and carnitine excretion above basal excretion increased linearly as amounts of infused carnitine increased; however, < or = 23% of the daily carnitine dosage was excreted above basal carnitine excretion. Infusion of up to 12 g/d of carnitine into the abomasum did not improve milk yield or nutrient digestibilities.

Evaluation of a ruminally protected methionine product for lactating dairy cows.

In Experiment 1, three ruminally and duodenally cannulated cows were used to assess the extent of ruminal protection and postruminal release of Met from ruminally protected Met using a polyester bag technique. The ruminally protected Met contained 85.1% DL-Met (wt/wt). Ruminal disappearance of Met averaged 5.8, 8.1, 21.8, 37.5, and 87.5% after 3, 6, 12, 24, and 96 h of incubation, respectively. Postruminal disappearance of Met from bags inserted in the duodenum after treatment with pepsin-HCl averaged 63.4, 62.6, 51.6, 43.6, and 8.8% for bags incubated in the rumen for 3, 6, 12, 24, and 96 h, respectively. In Experiment 2, 12 cows were fed either 0 or 20 g/d of ruminally protected Met from 7 to 10 d prepartum until 18 wk postcalving. Cows were fed the same total mixed diet. The DMI; yields of milk, CP, and SNF; and percentages of fat, CP, and SNF in milk were not affected by treatment. However, yields of fat and 3.5% FCM increased when ruminally protected Met was fed. Milk N components were not affected by treatment. Concentrations of Met increased in plasma when ruminally protected Met was fed. The mechanism for the increased production of milk fat and 3.5% FCM when ruminally protected Met was fed is unknown.

Ruminal degradation and dose response of dairy cows to dietary L-carnitine.

In Experiment 1, in vitro degradation of L-carnitine was measured in ruminal fluid obtained either from a cow that was fed a 75% concentrate diet or from a cow fed a control (50% forage and 3% fat) diet. Carnitine degradation was greater in ruminal fluid from the cow fed the control diet than in ruminal fluid from the cow fed the 75% concentrate diet and was more rapid in ruminal fluid obtained after 2 wk of adaptation to dietary carnitine supplementation (7 g/d). In Experiment 2, 20 multiparous Holstein cows were used in a replicated 5 x 5 Latin square design to determine the effects of increasing the amount of dietary L-carnitine (0, 0.875, 1.75, 3.5, or 7.0 g/d) that was fed to lactating dairy cows. All cows received the same diet, which contained 3% added fat. Carnitine concentration in milk and plasma increased linearly with carnitine supplementation. The DMI, milk yield, and milk composition were unaffected by carnitine. Apparent total tract digestibilities of NDF and fatty acids decreased quadratically as the amount of supplemented carnitine increased; generally, means were lowest when cows were fed 1.75 g/d of carnitine. The concentration of total VFA and molar percentages of individual VFA in ruminal fluid were unaffected by the amount of carnitine fed. Concentrations of glucose, NEFA, and urea N in plasma were unaffected by the amount of dietary carnitine; however, plasma cholesterol concentration decreased linearly as carnitine increased. Supplementation of < or = 7.0 g/d of dietary carnitine did not benefit DMI, milk yield, milk composition, or digestive measurements in this experiment.

High oil corn as silage or grain for dairy cows during an entire lactation.

Forty-five multiparous Holstein cows were used to compare the effects of diets that contained high oil corn grain, high oil corn silage, or a combination of both. At wk 4 after calving, cows were assigned to one of four treatment in a 2 (silage type) x 2 (grain type) factorial arrangement: 1) control silage and control grain, 2) high oil silage and control grain, 3) control silage and high oil grain, or 4) high oil silage and high oil grain. Diets contained haylage, corn silage, and concentrate (25:25:50, DM basis); corn grain was 27% of dietary DM. Data were analyzed for wk 4 to 17 and wk 4 to 43 of lactation and adjusted for covariate measurements made during wk 3. During wk 4 to 43, DMI increased when high oil grain was included in the diet, but was unaffected by type of silage. During wk 4 to 43 of lactation, yields of milk, CP, and fat; percentages and yields of N components in milk; body condition score; BW; and concentrations of NEFA, glucose, BHBA, and urea N in plasma were not affected by type of silage or corn grain fed. Results were similar for wk 4 to 17, except that milk yield tended to be higher for cows fed the high oil grain, and CP content of milk was lower when high oil corn silage was in the diet. Compared with corn grain from typical hybrids, high oil grain may improve DMI and milk yield of dairy cows during early lactation.

Responses of dairy cows during early lactation to ruminal or abomasal administration of L-carnitine.

Six multiparous Holstein cows were used in a replicated Latin square to investigate the effects of carnitine administration into the rumen or abomasum. Treatments were 1) control, 2) twice daily ruminal administration of carnitine, and 3) continuous abomasal infusion of carnitine. Cows not receiving abomasal carnitine were infused continuously with an equal volume of water. Carnitine dosage was constant for both treatments (226 mg/kg of DMI; ca. 6 g/d). The diet fed to all cows contained 3% added fat. Carnitine concentrations in plasma and liver increased when carnitine was administered into either the rumen or abomasum, indicating that both sites of administration were equally effective at increasing carnitine concentrations in tissue. Milk yield, milk composition, and DMI were unaffected by carnitine supplementation, except for increased SNF content. Apparent digestibilities of lipid, energy, and total fatty acids increased with carnitine administration at either site. The concentration of VFA in ruminal fluid tended to increase with ruminal carnitine, and the percentage of propionate increased when carnitine was administered at either site. Retained N tended to increase when carnitine was administered, primarily because of greater retained N when carnitine was administered ruminally. Excretion of carnitine in milk and urine increased when carnitine was administered at either site. Carnitine supplementation increased concentrations of carnitine in plasma and liver and improved lipid digestibility.

Secretion of oleic acid in milk fat in response to abomasal infusions of canola or high oleic sunflower fatty acids.

The feasibility of dietary strategies to increase oleic acid content of milk fat is unclear. Four Holstein cows were infused abomasally with free long-chain fatty acids from canola (62.5% C18:1) or high oleic sunflowers (86% C18:1). Each fatty acid mixture was infused for 3 d at 0, 133, 267, 400, 267, 133, and 0 g/d for a total of 21 d; cows then were changed to the opposite fatty acid mixture, and the infusion sequence was repeated. The DMI and percentages of casein and whey N in milk were decreased by infusion of fatty acids, but milk yield and percentages of fat and NPN in milk were increased. Contents of short- and medium-chain fatty acids and C16:0 in milk fat decreased, and contents of C18:1, C18:2, and C18:3 increased, as fatty acid infusion increased. Contents of C16:0 and C18:0 in plasma triglyceride were decreased, and content of C18:1 was increased, by increasing infusion of fatty acids. All changes reversed when the amount of fatty acid infused was decreased. Within the range of amounts of fatty acids infused, the relationship between yield of C18:1 in milk fat and the amount of C18:1 infused into the abomasum was linear, and transfer efficiency was 54.1%. Increased concentration and yield of C18:1 in milk were attributable mostly to the increased exogenous supply of C18:1.

Infusion of four long-chain fatty acid mixtures into the abomasum of lactating dairy cows.

Five Holstein cows were utilized in a Latin square design to determine the effects of postruminal profile of fatty acids on DMI, milk yield and composition, nutrient digestibilities, and metabolites in blood. Treatments were abomasal infusions of 1) control, 169 to 180 g/d of meat solubles; 2) control plus 450 g/d of mostly saturated fatty acids; 3) canola fatty acids; 4) soybean fatty acids; or 5) sunflower fatty acids. Infusion of fatty acids decreased intakes of DM, CP, and gross energy; yields of milk, FCM, SNF, total solids, CP, NPN, true protein, whey protein, and casein; and percentages of SNF, CP, NPN, true protein, and casein in milk. Cows infused with mostly saturated fatty acids consumed more CP and digestible energy; yielded more milk, FCM, fat, SNF, total solids, CP, true protein, and casein; and had greater percentages of SNF and total solids in milk than cows infused with unsaturated fatty acids. Milk fatty acids reflected the profile of the infused fatty acid mixture. Ruminal characteristics and apparent digestibilities of DM, NDF, energy, and fatty acids generally were not different among treatments. The profile of fatty acids reaching the small intestine may influence responses when supplemental fats are fed to lactating dairy cows.

Estrogen induction of fatty liver in dairy cattle.

Two trials were conducted to determine if estrogen contributes to development of fatty liver in dairy cattle. During trial 1, eight late lactation, nonpregnant cows were assigned to 0 or 15 mg estradiol-17 beta benzoate/d treatment. Days 1 to 3 of the trial were for baseline measurements, and treatments were given from d 4 to 21; on d 20 and 21 animals were fasted. Short-term feed deprivation resulted in increased plasma FFA concentrations and rapid accumulation of triglyceride into liver tissue obtained by biopsy. During starvation, plasma FFA concentration and liver triglyceride content were lower for cows receiving the estradiol-17 beta treatment relative to cows receiving control treatment. Very low density lipoprotein concentration in blood increased dramatically in three of four animals during estradiol-17 beta administration. Because of the decrease in milk production during estradiol-17 beta treatment, it was not known whether this represented a decrease in very low density lipoprotein clearance from blood or reflected a lipotropic response to estradiol-17 beta. Therefore, a second trial was conducted employing nonlactating cows, and control and estradiol-17 beta-treated animals were pair fed. The trial was 33 d with d 1 to 3 for baseline measurements, and treatments were administered from d 4 to 33. All animals were starved from d 19 to 23. Estradiol-17 beta increased hepatic lipid and triglyceride accumulation and plasma very low density lipoprotein concentration during starvation. Plasma FFA concentration was also increased by estradiol-17 beta during this time; therefore, a direct or indirect effect of estrogen on hepatic lipid metabolism could not be delineated.