Effect of grains differing in expected ruminal fermentability on the productivity of lactating dairy cows

The objective of the study was to evaluate the effect of barley and corn grains differing in expected fermentability in the rumen on dry matter intake (DMI) and productivity of lactating dairy cows. Twenty-two multiparous and 9 primiparous lactating Holstein cows (94 ± 29 d in milk; mean ± SD) were used in a 3 × 3 Latin square design with 21-d periods. Experimental diets contained approximately 40% of dietary dry matter as steam-rolled barley, using a lot of cultivar Dillon or cultivar Xena, or a corn mixture (CM) containing 87.5% dry ground corn, 11.4% beet pulp, and 1.1% urea (dry matter basis). Starch concentration of the grain sources was 50.0, 58.7, and 60.4% and in vitro 6-h starch digestibility was 73.5, 78.0, and 71.0%, respectively, for Dillon, Xena, and CM. All diets were formulated to contain 19.4% crude protein and 25.3% forage neutral detergent fiber. Dry matter intake (23.6 vs. 21.6 kg/d) and yields of milk (40.4 vs. 37.4 kg/d), milk protein (1.20 vs. 1.12 kg/d), and milk lactose (1.85 vs. 1.74 kg/d) were higher for cows fed CM than for cows fed barley. Although DMI was similar for cows fed Xena and Dillon (21.9 vs. 21.4 kg/d), cows fed Xena had higher yields of milk (38.5 vs. 36.2 kg/d), milk protein (1.18 vs. 1.07 kg/d), and milk lactose (1.80 vs. 1.69 kg/d) than cows fed Dillon. However, milk fat concentration tended to be higher (3.47 vs. 3.23%) for cows fed Dillon than Xena. Plasma glucose and nonesterified fatty acid concentrations were not affected by treatment, but plasma insulin concentration was higher for cows fed Xena compared with those fed Dillon (8.50 vs. 5.91 μIU/mL). Greater milk production for cows fed CM can be attributed to greater DMI. Feeding barley that was lower in starch concentration and ruminal starch fermentability (Dillon) did not increase DMI compared with feeding barley that was higher in starch concentration and ruminal starch fermentability (Xena). Reducing ruminal starch degradation of barley grain may not improve the productivity of lactating dairy cows.     

Effect of feeding a reduced-starch diet with or without amylase addition on lactation performance in dairy cows

The objective of this study was to determine lactation performance responses of high-producing dairy cows to a reduced-starch diet compared with a normal-starch diet and to the addition of exogenous amylase to the reduced-starch diet. Thirty-six multiparous Holstein cows (51 ± 22 DIM and 643 ± 49 kg of body weight at trial initiation) were randomly assigned to 1 of 3 treatments in a completely randomized design: a 3-wk covariate adjustment period during which the cows were fed the normal-starch diet, followed by a 12-wk treatment period during which the cows were fed their assigned treatment diets. The normal-starch TMR did not contain exogenous amylase (NS−). The reduced-starch diets, formulated by partially replacing corn grain with soy hulls, were fed without (RS−) and with (RS+) exogenous amylase added to the TMR. Starch and NDF concentrations averaged 27.1 and 30.6%, 21.8 and 36.6%, and 20.7 and 36.6% (dry matter basis) for the NS−, RS−, and RS+ diets, respectively. Dry matter intake for cows fed the RS− diet was 2.4 and 3.2 kg/d greater than for cows fed the NS− and RS+ diets, respectively. Intake of NDF ranged from 1.19 to 1.52% of body weight among the treatments, with the RS− diet being 28% greater than the NS− diet and 13% greater than the RS+ diet. Milk yield averaged 50.4 kg/d and was unaffected by treatment. Fat-corrected milk yield was 2.9 kg/d greater for cows fed the RS− diet than for cows fed the NS− diet. Body weight and body condition score measurements were unaffected by treatment. Fat-, solids-, and energy-corrected milk feed conversions (kilograms/kilogram of DMI) were 12 to 13% greater for cows fed the RS+ diet than for cows fed the RS− diet. Dry matter and nutrient digestibilities were lowest for cows fed the NS− diet and greatest for cows fed the RS+ diet, and were greater for cows fed the RS+ diet than for cows fed the RS− diet, with the exception of starch digestibility, which was similar. Greater conversion of feed to milk for dairy cows fed reduced-starch diets that include exogenous amylase may offer potential for improving economic performance.     

Postabsorptive carbohydrate adaptations to heat stress and monensin supplementation in lactating Holstein cows

Multiparous cows (n = 34, 89 d in milk, 537 kg) housed in environmental chambers were fed a control total mixed ration or one containing monensin (450 mg/cow per day) during 2 experimental periods (P): (1) thermal neutral (TN) conditions (constant 20°C) with ad libitum intake for 9 d, and (2) heat stress (HS, n = 16) or pair-fed [PF; in TN (PFTN); n = 18] for 9 d. Heat-stress was cyclical with temperatures ranging from 29.4 to 38.9°C. Rectal temperatures and respiration rates increased in HS compared with PFTN cows (38.4 to 40.4°C, 40 to 93 breaths/min). Heat stress reduced dry matter intake (DMI, 28%), and by design, PFTN cows had similar intakes. Monensin-fed cows consumed less DMI (1.59 kg/d) independent of environment. Milk yield decreased 29% (9.1 kg) in HS and 15% (4.5 kg) in PFTN cows, indicating that reduced DMI accounted for only 50% of the decreased milk yield during HS. Monensin had no effect on milk yield in either environment. Both HS and PFTN cows entered into calculated negative energy balance (−2.7 Mcal/d), and feeding monensin increased feed efficiency (7%) regardless of environment. The glucose response to an epinephrine (EPI) challenge increased (27%) during P2 for both HS and PFTN cows, whereas the nonesterified fatty acid response to the EPI challenge was larger (56%) during P2 in the PFTN compared with the HS cows. Compared with P1, whole-body glucose rate of appearance (Ra) decreased similarly during P2 in both HS and PFTN cows (646 vs. 514 mmol/h). Although having similar rates of glucose Ra, HS cows synthesized approximately 225 g less milk lactose; therefore, on a milk yield basis, glucose Ra decreased (3.3%) in PFTN but increased (5.6%) in HS cows. Regardless of environment, monensin-fed cows had increased (10%) glucose Ra per unit of DMI. From the results we suggest that the liver remains sensitive but adipose tissue becomes refractory to catabolic signals and that glucose Ra (presumably of hepatic origin) is preferentially utilized for processes other than milk synthesis during HS.     

Effects of dietary forage level and monensin on lactation performance, digestibility and fecal excretion of nutrients, and efficiency of feed nitrogen utilization of Holstein dairy cows

Two experiments (Exp. 1 and 2) were conducted using a 4 × 4 Latin square design with 2 replications (n = 8) to evaluate effects of feeding Holstein dairy cows a total mixed ration containing 50 or 60% of ration dry matter (DM) from forages with or without supplementation of monensin. In Exp. 1, alfalfa silage (AS) was used as the major forage (55% forage DM), and corn silage (CS; 45% forage DM) was used to make up the rest of the forage portion of diets (55AS:45CS). In Exp. 2, CS was used as the major forage (70% forage DM) and alfalfa hay (AH; 30% forage DM) was used to make up the rest of the forage portion of diets (70CS:30AH). Experimental diets were arranged in a 2 × 2 factorial with 50 or 60% ration DM from forages and monensin supplemented at 0 or 300 mg/cow daily. In Exp. 1 (55AS:45CS), feeding 60% forage diets decreased DM intake (DMI; 27.3 vs. 29.6 kg/d) but maintained the same levels of milk (45.8 vs. 47.0 kg/d) compared with 50% forage diets. The efficiency of converting feed to milk or 3.5% fat-corrected milk was greater for cows fed 60% compared with 50% forage diets (1.7 vs. 1.6 kg milk or 3.5% fat-corrected milk/kg of DMI, respectively). Increasing dietary forage level from 50 to 60% of ration DM increased milk fat percentage (3.4 to 3.5%); however, adding monensin to the 60% forage diet inhibited the increase in milk fat percentage. Feeding 60% forage diets decreased feed cost, but this decrease ($0.5/head per day) in feed cost did not affect income over feed cost. Feeding 60% forage diets decreased fecal excretion of DM (10.6 to 9.6 kg/d) and nitrogen (N; 354 to 324 g/d) and improved apparent digestibility of neutral detergent fiber from 43 to 49% and apparent efficiency of feed N utilization from 32.3 to 35.9% compared with 50% forage diets. In Exp. 2 (70CS:30AH), feeding 60% forage diets decreased DMI from 29.6 to 28.2 kg but maintained the same level of milk (41.1 vs. 40.8 kg/d) and therefore increased the efficiency of converting feed to milk (1.46 vs. 1.38 kg milk/kg DMI) compared with 50% forage diets. Daily feed cost for feeding 60% forage diets was $0.3/head lower than for the 50% forage diets. Fecal excretion of DM (10.3 vs. 11.5 kg/d) was lower and fecal excretion of N (299 vs. 328 g/d) tended to be lower for 60% compared with 50% forage diets. Results from these 2 experiments suggest that a 60% forage diet consisting of either AS or CS as the major forage can be fed to high producing Holstein dairy cows without affecting milk production while improving or maintaining the efficiency of converting feed to milk and the apparent efficiency of utilization of feed N. Cows receiving a 60% forage diet had a similar or improved digestibility of nutrients with a similar or reduced fecal excretion of nutrients. Effects of monensin under the conditions of the current experiments were minimal.     

Influence of a reduced-starch diet with or without exogenous amylase on lactation performance by dairy cows

The objective of this trial was to determine lactation performance responses in high-producing dairy cows to a reduced-starch versus a normal-starch diet and to the addition of exogenous amylase to the reduced-starch diet. Forty-five multiparous Holstein cows, 68 ± 29 d in milk and 696 ± 62 kg of body weight (BW) at trial initiation, were randomly assigned to 1 of 3 treatments in a completely randomized design; a 2-wk covariate adjustment period with cows fed the normal-starch diet was followed by a 10-wk treatment period with cows fed their assigned treatment diets. The normal-starch total mixed ration did not contain exogenous amylase (NS−). The reduced-starch diets, formulated by partially replacing corn grain and soybean meal with whole cottonseed and wheat middlings, were fed without (RS−) and with (RS+) exogenous amylase addition to the total mixed ration. All diets contained 50% forage and 19.8% forage neutral detergent fiber (dry matter basis). Starch and neutral detergent fiber concentrations averaged 27.0 and 30.9%, 22.1 and 35.0%, and 21.2 and 35.3% (dry matter basis) for the NS−, RS−, and RS+ diets, respectively. Expressed as a percentage of BW, dry matter intake was greater for cows fed RS− than for cows fed NS− or RS+. Intake of neutral detergent fiber ranged from 1.09 to 1.30% of BW among the treatments, with that of RS− being 21% greater than that of NS−. Milk yield tended to be greater for cows fed NS− compared with the RS diets. Milk fat content and yield were unaffected by treatment. Milk protein content and yield were greater for cows fed NS− compared with the RS diets. Concentrations of milk urea nitrogen were greater for cows fed RS diets compared with the NS− diet. Body weight, BW change, and body condition score were unaffected by treatment. Feed conversion (kg of milk/kg of dry matter intake) was 10% greater on average for cows fed NS− than for cows fed the RS diets, and tended to be 6% greater for cows fed RS+ compared with RS−. Feeding a reduced-starch diet formulated by partially replacing corn grain and soybean meal with a wheat middlings and whole cottonseed mixture compared with a normal-starch diet without addition of exogenous amylase to either diet reduced milk and component-corrected feed conversions. Addition of exogenous amylase to a reduced-starch diet was of minimal benefit in this study.     

Production performance and milk composition of dairy cows fed whole or ground flaxseed with or without monensin

Eight multiparous Holstein cows averaging 570 ± 43 kg of body weight and 60 ± 20 d in milk were used in a double Latin square design with four 21-d experimental periods to determine the effects of feeding ground or whole flaxseed with or without monensin supplementation (0.02% on a dry matter basis) on milk production and composition, feed intake, digestion, blood composition, and fatty acid profile of milk. Intake of dry matter was similar among treatments. Cows fed whole flaxseed had higher digestibility of acid detergent fiber but lower digestibilities of crude protein and ether extract than those fed ground flaxseed; monensin had no effect on digestibility. Milk production tended to be greater for cows fed ground flaxseed (22.8 kg/d) compared with those fed whole flaxseed (21.4 kg/d). Processing of flaxseed had no effect on 4% fat-corrected milk yield and milk protein and lactose concentrations. Monensin supplementation had no effect on milk production but decreased 4% fat-corrected milk yield as a result of a decrease in milk fat concentration. Feeding ground compared with whole flaxseed decreased concentrations of 16:0, 17:0, and cis6-20:4 and increased those of cis6-18:2, cis9, trans11-18:2, and cis3-18:3 in milk fat. As a result, there was a decrease in concentrations of medium-chain and saturated fatty acids and a trend for higher concentrations of long-chain fatty acids in milk fat when feeding ground compared with whole flaxseed. Monensin supplementation increased concentrations of cis9 and trans11-18:2 and decreased concentrations of saturated fatty acids in milk fat. There was an interaction between flaxseed processing and monensin supplementation, with higher milk fat concentration of trans11-18:1 for cows fed ground flaxseed with monensin than for those fed the other diets. Flaxseed processing and monensin supplementation successfully modified the fatty acid composition of milk fat that might favor nutritional value for consumers.     

Effect of prepartum anionic supplementation on periparturient feed intake, health, and milk production

Our objectives were to determine if dietary cation-anion difference (DCAD) and source of anions influence periparturient feed intake and milk production of dairy cattle during the transition period. Diets differed in DCAD (cationic or anionic) and anionic supplement. The 4 diets used prepartum were (1) control [DCAD +20 mEq/100 g of dry matter (DM)], (2) Bio-Chlor (DCAD −12 mEq/100 g of DM; Church & Dwight Co. Inc., Princeton, NJ), (3) Fermenten (DCAD −10 mEq/100 g of DM; Church & Dwight Co. Inc.), and (4) salts (DCAD −10 mEq/100 g of DM). Urine pH was lower for cows that consumed an anionic diet prepartum compared with control. Prepartum diet had no effect on prepartum dry matter intake (DMI) of multiparous or primiparous cows. Postpartum DMI and milk yield for multiparous cows fed anionic diets prepartum were greater compared with those fed the control diet. Postpartum DMI and milk yield of primiparous cows were similar for prepartum diets. Feeding prepartum anionic diets did not affect plasma Ca at or near calving. However, cows fed anionic diets began their decline in plasma Ca later than control cows. Postpartum β-hydroxybutyrate and nonesterified fatty acids were lower for primiparous cows fed prepartum anionic diets compared with those fed the control diet. Prepartum and postpartum plasma glucose concentrations were not affected by prepartum diet for all cows. Liver triglyceride differed for parity by day. Parities were similar at 21 d prepartum, but at 0 d and 21 d postpartum, levels were greater for multiparous cows. Results indicate that decreasing the DCAD of the diet during the prepartum period can increase postpartum DMI and milk production of multiparous cows without negatively affecting performance of primiparous cows.     

Evaluation of rumen-protected lysine supplementation to lactating dairy cows consuming increasing amounts of distillers dried grains with solubles

Twenty multiparous Holstein cows were used in four 5 × 5 Latin squares to determine the effects of feeding increasing amounts of distillers dried grains with solubles (DDGS) in diets with or without the supplementation (60 g/d) of a rumen-protected Lys (RPL) product (AminoShure-L, 38% l-Lys; Balchem Encapsulates, New Hampton, NY) on milk yield and composition and plasma concentration of AA. Dietary treatments were (1) control (CON; no DDGS), (2) 10% DDGS (10DG), (3) 20% DDGS (20DG), (4) 10% DDGS plus RPL (10DGRPL), and (5) 20% DDGS plus RPL (20DGRPL). Diets were formulated using the Cornell-Penn-Miner Dairy model (CPM v3.0; http://cahpwww.vet.upenn.edu/node/77) to provide a predicted decreasing supply of Lys (117, 99, and 91% of requirements) for the CON, 10DG, and 20DG diets, respectively. Addition of RPL to the 10DG and 20DG diets (unsupplemented diets) resulted in 2 additional treatments, 10DGRPL and 20DGRPL diets, respectively. The 10DGRPL and 20DGRPL diets met 110 and 100% of the Lys requirements, respectively. Periods lasted 21 d, with the last 3 d for data collection. Compared with cows fed the CON diet, cows fed diets with DDGS had a similar dry matter intake (DMI; 25.4 ± 0.88 kg/d), milk yield (30.7 ± 1.67 kg/d), and composition, except for protein percentage, which was higher (3.15 vs. 3.21 ± 0.05%) and resulted in higher (0.94 vs. 1.00 ± 0.05 kg/d) protein yield by cows fed diets containing 20% DDGS. Unexpectedly, despite diets being formulated based on predicted DMI of 23.3 kg/d and milk yield of 38.5 kg/d, cows had a greater DMI and lower milk yield across all treatments, which resulted in diets that were predicted by CPM Dairy to supply sufficient amounts of Lys (140, 118, and 104% of requirement for the CON, 10DG, and 20DG diet, respectively) and consequently, supplementation with RPL did not have an effect on milk production or composition. Plasma concentration of Lys decreased (11.8%) as DDGS inclusion increased. For other essential AA, plasma concentrations of cows fed diets with DDGS were lower for Arg, His, and Val and greater for Leu and Met compared with cows fed the CON diet. Supplementation with RPL failed to decrease the plasma concentration of other essential AA, which provides support that Lys was not limiting.     

Nutrient demand interacts with forage family to affect intake and digestion responses in dairy cows

The effect of feed intake in the preliminary period on responses to diets containing alfalfa silage or orchardgrass silage was evaluated using 8 ruminally and duodenally cannulated Holstein cows in a crossover design experiment with a 14-d preliminary period and two 15-d treatment periods. Responses measured were DMI, rates of fiber digestion and passage, and milk production. Cows were 139 ± 83 (mean ± SD) d in milk at the beginning of the preliminary period. During the preliminary period, 3.5% fat-corrected milk yield ranged from 23.9 to 47.6 kg/d (mean = 36.9 kg/d) and preliminary voluntary DMI (pVDMI) ranged from 14.2 to 21.3 kg/d (mean = 18.6 kg/d). The 2 treatments were a diet containing alfalfa silage as the sole forage (AL) and a diet containing orchardgrass silage as the sole forage (OG). Alfalfa silage contained 43% neutral detergent fiber (NDF; dry-matter basis) and orchardgrass silage contained 48% NDF; diets contained ∼23% forage NDF and 27% total NDF, so forage-to-concentrate ratio was 53:47 for AL and 48:52 for OG. Digestibility of NDF was lower for AL in the rumen and whole tract compared with OG, and milk fat concentration tended to be greater for OG than for AL. Mean 3.5% fat-corrected milk yield and DMI were not different between AL and OG. Response of DMI to forage family depended on pVDMI, as indicated by a significant interaction between treatment and pVDMI in predicting DMI. As pVDMI increased, DMI increased when cows were fed AL but not when they were fed OG. That is, as appetite increased, intake was more restricted for the more physically filling OG than for the less physically filling AL. This more positive DMI response to AL over OG among high-pVDMI cows is corroborated by interactions between treatments and pVDMI for both ruminal NDF turnover rate and indigestible NDF passage rate response. Therefore, the effects of alfalfa and orchardgrass forages on intake and fiber digestion depended on the extent to which fill limited feed intake of an individual cow.     

Effect of the ratio of zinc amino acid complex to zinc sulfate on the performance of Holstein cows

Multiparous (n = 70) and primiparous (n = 66) Holstein cows were balanced by 305-d previous mature-equivalent milk yield and parity and assigned to 1 of 3 dietary treatments to evaluate the ratio of zinc sulfate to zinc amino acid complex (CZ) in pre- and postpartum Holstein cows fed diets containing 75 mg of added zinc/kg. Treatments were (1) 75 mg of supplemental zinc/kg of dry matter (DM) provided entirely as zinc sulfate (0-CZ); (2) 0-CZ diet, except 33.3 mg of zinc sulfate/kg of DM in the prepartum and 15.5 mg of zinc sulfate/kg of DM in the postpartum diet were replaced by CZ from Availa-Zn (16-CZ; Zinpro Corp., Eden Prairie MN); and (3) 0-CZ diet, except 66.6 mg of zinc sulfate/kg of DM in the prepartum and 40.0 mg of zinc sulfate/kg of DM in the postpartum diet was replaced by Availa-Zn (40-CZ). Cows were housed at the Iowa State University Dairy Farm and were individually offered a total mixed ration containing dietary treatments beginning at 28 ± 15 d before expected calving date until 250 d in milk. Relative to 0-CZ, multiparous cows (but not primiparous) fed CZ (16-CZ or 40-CZ) had increased (20%) colostrum IgG concentrations. Prepartum DM intake (DMI) was decreased with CZ supplementation. Postpartum DMI was decreased in cows fed CZ, whereas milk yield (MY) was increased in the 40-CZ-fed cows relative to those fed both 0-CZ and 16-CZ. Feed efficiency increased linearly when measured as MY/DMI, 3.5% fat-corrected MY/DMI, and solids-corrected MY/DMI. Regardless of level, feeding CZ decreased services per conception. Feeding 16-CZ decreased milk fat concentration and feeding CZ linearly increased milk urea nitrogen concentration. In summary, supplementing zinc as a mixture of CZ and zinc sulfate, as opposed to supplementing only zinc sulfate, has beneficial effects on production parameters in dairy cows, with those benefits becoming more apparent as the ratio of CZ to zinc sulfate increases.     

Effect of a high cornstarch diet on hepatic cytochrome P450 2C and 3A activity and progesterone half-life in dairy cows

In the cow, inadequate concentrations of progesterone during gestation may lead to an abrupt termination of pregnancy. The primary organ involved in progesterone catabolism is the liver, which contains an abundance of cytochrome P450 isozymes (EC 1.14.14.1; mixed-function monooxygenases). The objectives of the current experiment were to determine the effect of feeding 2 isoenergetic and isonitrogenous diets, formulated to cause divergent insulin secretion, on hepatic cytochrome P450 2C (CYP2C) and 3A (CYP3A) activity as well as the resulting biological half-life of progesterone. Twenty-two Holstein cows averaging 80 ± 7 d in milk were randomly assigned to either a high cornstarch diet or a high fiber diet in a crossover experimental design consisting of two 14-d periods. Dry matter intake, milk yield, milk lactose yield, and milk lactose percentage were similar between the 2 diets. Milk fat yield and milk fat percentage were higher in cows fed the high fiber diet, whereas milk protein yield tended to be higher and milk protein percentage was higher in cows fed the high cornstarch diet. Energy balance tended to be improved by 57% in cows consuming the high cornstarch diet. Insulin concentrations at the time of liver biopsy (3.16 ± 0.04 h post-feeding) were increased by 44% in cows consuming the high cornstarch diet compared with cows consuming the high fiber diet. Cytochrome P450 2C activity was decreased by 45%, whereas CYP3A activity tended to be lowered by 34% in cows consuming the high cornstarch diet. Cytochrome P450 2C mRNA expression tended to be decreased by 21% in cows fed the high cornstarch diet, whereas CYP3A mRNA expression was not different between the dietary treatments. The fractional rate constant of progesterone decay was not different between the 2 diets; however, the half-life of progesterone tended to be longer in cows fed the high cornstarch diet compared with cows fed the high fiber diet (85 vs. 64 min, respectively). In summary, cows consuming the high cornstarch diet had increased insulin concentrations and lower hepatic CYP2C and CYP3A activity and tended to have a longer progesterone half-life compared with cows consuming the high fiber diet. Feeding diets that stimulate insulin secretion could alter progesterone clearance during lactation, when dairy cows have increased rates of progesterone inactivation because of high energy demands and increased DMI.     

Effects of prepartum dietary carbohydrate source and monensin on periparturient metabolism and lactation in multiparous cows

Eighty-five multiparous Holstein cows were used in a completely randomized design with restrictions to evaluate the effects of prepartum carbohydrate (CHO) source and monensin on periparturient dry matter intake (DMI), blood parameters, and lactation performance of dairy cows. Dietary treatments were arranged in a 2 × 2 factorial arrangement with a conventional (CONV) dry cow diet and a nonforage fiber source (NFFS) dry cow diet not supplemented (−) or supplemented (+) with 330 mg/cow per d of monensin as a top dressing. The CONV diet contained 70% forage and the NFFS diet contained nonforage fiber sources such that 28% of the forage was replaced with cottonseed hulls and soyhulls. The experimental diets (CONV and NFFS) were fed throughout the entire dry period (for 60 d before parturition). Monensin was top dressed once daily starting 28 d (27 ± 1.8 SD) before the expected calving date and continued until parturition. After parturition, all cows received the same lactating cow diet. During the last 28 d of gestation, cows receiving the NFFS diets prepartum had greater DMI (15.8 vs. 11.9 kg/d), DMI as a percentage of body weight (2.1 vs. 1.6% of body weight), plasma glucose (67.4 vs. 64.6 mg/dL), and serum insulin concentrations (0.59 vs. 0.45 ng/mL), and lower plasma nonesterified fatty acid concentrations (185 vs. 245 μEq/L) compared with cows receiving the CONV diets prepartum. Average milk production or composition during the first 56 d of lactation was not significantly affected by prepartum source of CHO, monensin, or their combination; however, there was a trend for the prepartum CHO source to affect milk production over time. Supplementation of monensin as a top dressing for 28 d prepartum had no effect on periparturient measurements. The prepartum diet did not affect postpartum DMI, blood glucose, nonesterified fatty acids, insulin concentrations, or liver triglyceride content. Results from this research demonstrated that partly replacing conventional dietary carbohydrate sources with NFFS, cottonseed hulls and soyhulls, in the dry cow diet improved or maintained the prepartum DMI and therefore enhanced the prepartum metabolic status, as indicated by key blood metabolite concentrations. This greater prepartum DMI may potentially increase milk production during early lactation.     

Anti-methanogenic effects of monensin in dairy and beef cattle: A meta-analysis

Monensin is a widely used feed additive with the potential to minimize methane (CH₄) emissions from cattle. Several studies have investigated the effects of monensin on CH₄, but findings have been inconsistent. The objective of the present study was to conduct meta-analyses to quantitatively summarize the effect of monensin on CH₄ production (g/d) and the percentage of dietary gross energy lost as CH₄ (Y_m) in dairy cows and beef steers. Data from 22 controlled studies were used. Heterogeneity of the monensin effects were estimated using random effect models. Due to significant heterogeneity (>68%) in both dairy and beef studies, the random effect models were then extended to mixed effect models by including fixed effects of DMI, dietary nutrient contents, monensin dose, and length of monensin treatment period. Monensin reduced Y_m from 5.97 to 5.43% and diets with greater neutral detergent fiber contents (g/kg of dry matter) tended to enhance the monensin effect on CH₄ in beef steers. When adjusted for the neutral detergent fiber effect, monensin supplementation [average 32 mg/kg of dry matter intake (DMI)] reduced CH₄ emissions from beef steers by 19 ± 4 g/d. Dietary ether extract content and DMI had a positive and a negative effect on monensin in dairy cows, respectively. When adjusted for these 2 effects in the final mixed-effect model, monensin feeding (average 21 mg/kg of DMI) was associated with a 6 ± 3 g/d reduction in CH₄ emissions in dairy cows. When analyzed across dairy and beef cattle studies, DMI or monensin dose (mg/kg of DMI) tended to decrease or increase the effect of monensin in reducing methane emissions, respectively. Methane mitigation effects of monensin in dairy cows (–12 ± 6 g/d) and beef steers (–14 ± 6 g/d) became similar when adjusted for the monensin dose differences between dairy cow and beef steer studies. When adjusted for DMI differences, monensin reduced Y_m in dairy cows (–0.23 ± 0.14) and beef steers (–0.33 ± 0.16). Monensin treatment period length did not significantly modify the monensin effects in dairy cow or beef steer studies. Overall, monensin had stronger antimethanogenic effects in beef steers than dairy cows, but the effects in dairy cows could potentially be improved by dietary composition modifications and increasing the monensin dose.     

Effects of supplemental chromium propionate and rumen-protected amino acids on productivity,diet digestibility,and energy balance of peak-lactation dairy cattle

Chromium (Cr) feeding in early lactation increased milk production in some studies, but responses to dietary Cr during peak lactation have not been evaluated. Furthermore, interactions of essential amino acids (AA) and Cr have not been explored. Our objective was to evaluate responses to CrPr (KemTRACE chromium propionate 0.04%, Kemin Industries Inc., Des Moines, IA) and rumen-protected Lys (LysiPEARL, Kemin Industries Inc.) and Met (MetiPEARL, Kemin Industries Inc.) and their interaction in peak-lactation cows. Forty-eight individually fed Holstein cows (21 primiparous, 27 multiparous, 38 ± 15 d in milk) were stratified by calving date in 12 blocks and randomly assigned to 1 of 4 treatments within block. Treatments were control, CrPr (8 mg/d of Cr), RPLM (10 g/d of Lys and 5 g/d of Met, intestinally available), or CrPr plus RPLM. Treatments were premixed with ground corn and top-dressed at 200 g/d for 35 d. Diets consisted of corn silage, alfalfa hay, and concentrates, providing approximately 17% crude protein, 31% neutral detergent fiber, and 40% nonfiber carbohydrates. Dry matter intake (DMI) significantly increased with the inclusion of CrPr (22.2 vs. 20.8 ± 0.67 kg/d), and energy-corrected milk (ECM) yield tended to increase. In addition, CrPr increased milk protein yield and tended to increase DMI in primiparous cows but not in multiparous cows. A CrPr × week interaction was detected for milk lactose content, which was increased by CrPr during wk 1 only (4.99 vs. 4.88 ± 0.036%). As a proportion of plasma AA, lysine increased and methionine tended to increase in response to RPLM, but the inclusion of RPLM decreased N efficiency (milk protein N:N intake). Digestible energy intake, gross energy digestibility, and energy balance were not affected by treatments. We observed no treatment effects on feed efficiency or changes in body weight or body condition score. In summary, feeding CrPr increased DMI and tended to increase ECM in cows fed for 5 wk near peak lactation, with primiparous cows showing greater responses in DMI and milk protein yield than multiparous cows.     

Influence of corn silage hybrid type on lactation performance by Holstein dairy cows

The primary objective of this study was to determine lactation performance by dairy cows fed nutridense (ND), dual-purpose (DP), or brown midrib (BM) corn silage hybrids at the same concentration in the diets. A secondary objective was to determine lactation performance by dairy cows fed NutriDense corn silage at a higher concentration in the diet. One hundred twenty-eight Holstein and Holstein × Jersey cows (105 ± 38 d in milk) were stratified by breed and parity and randomly assigned to 16 pens of 8 cows each. Pens were then randomly assigned to 1 of 4 treatments. Three treatment total mixed rations (TMR; DP40, BM40, and ND40) contained 40% of dry matter (DM) from the respective corn silage hybrid and 20% of DM from alfalfa silage. The fourth treatment TMR had ND corn silage as the sole forage at 65% of DM (ND65). A 2-wk covariate adjustment period preceded the treatment period, with all pens receiving a TMR with equal proportions of DP40, BM40, and ND40. Following the covariate period, cows were fed their assigned treatment diets for 11 wk. nutridense corn silage had greater starch and lower neutral detergent fiber (NDF) content than DP or BM, resulting in ND40 having greater energy content (73.2% of total digestible nutrients, TDN) than DP40 or BM40 (71.9 and 71.4% TDN, respectively). Cows fed BM40 had greater milk yield than DP40, whereas ND40 tended to have greater milk yield and had greater protein and lactose yields compared with DP40. No differences in intake, component-corrected milk yields, or feed efficiency were detected between DP40, BM40, and ND40. Milk yield differences may be due to increased starch intake for ND40 and increased digestible NDF intake for BM40 compared with DP40. Intake and milk yield and composition were similar for ND40 compared with BM40, possibly due to counteracting effects of higher starch intake for ND40 and higher digestible NDF intake for BM40. Feeding ND65 reduced intake, and thus milk and component yields, compared with ND40 due to either increased ruminal starch digestibility or increased rumen fill for ND65. Nutridense corn silage was a viable alternative to both DP and BM at 40% of diet DM; however, lactation performance was reduced when nutridense corn silage was fed at 65% of DM.     

Effects of alfalfa hay particle size in high-concentrate diets supplemented with unsaturated fat: Chewing behavior,total-tract digestibility,and milk production of dairy cows

This study evaluated the effects of increasing the physically effective neutral detergent fiber (peNDF) intake of lactating dairy cows fed high-concentrate diets supplemented with unsaturated fat on intake, eating behavior, diet sorting, chewing activity, total-tract digestibility, and milk production and composition. Diets contained 24% alfalfa hay (AH), 16% corn silage, 58% concentrate, and 2% yellow grease [dry matter (DM) basis], and dietary peNDF content was increased by varying the particle size (PS) of the AH. Nine multiparous cows averaging 87.8 ± 14.8 d in milk and weighing 653 ± 53 kg were randomly assigned to a triplicate 3 × 3 Latin square. During each 21-d period, cows were offered 1 of 3 total mixed rations that varied in PS of AH: fine, medium, and long, with a geometric mean particle length of 3.00, 3.57 and 3.87 mm, respectively. Increasing PS quadratically affected DM intake (DMI; 24.7, 25.4, and 23.7 kg/d, for fine, medium, and long, respectively), but cumulative DMI at 2, 4, and 6 h after feeding was similar across treatments, averaging 23.4, 35.6 and 46.4% of total DMI for the 3 time points, respectively. Increased peNDF intake did not affect feed sorting, but increased daily eating time, and eating and total chewing time per kilogram of DMI. Daily rumination time exhibited a quadratic response, with highest rumination time for the medium diet. Dietary PS had no effects on digestibility in the total tract, but we observed, for fine, medium, and long diets, quadratic responses in milk production (41.5, 43.3, and 40.4 kg/d), 4% fat-corrected milk production, and milk protein yield. Milk fat content decreased linearly with increasing PS, but milk fat content and fat:protein ratio were low for all treatments, likely due to adding unsaturated fat to a diet containing a high level of nonfiber carbohydrates (42.2% of DM). The composition, degree of saturation, and total conjugated linoleic acid content of fatty acids in milk fat were not affected by the change in peNDF content of the diet. The study indicates that a moderate increase in the PS of AH in diets containing unsaturated fat elevates peNDF intake and increases chewing activity, DMI, milk yield and milk fat production. However, the effects of dietary PS were quadratic, with maximum DMI and milk production observed with diets supplying 24% dietary peNDF (measured as the proportion of the ration retained on sieves >1.18 mm multiplied by dietary neutral detergent fiber content; DM basis).     

Effect of frequency of feed delivery on the behavior and productivity of lactating dairy cows

The objective of this study was to determine the effect of feed delivery frequency on the behavioral patterns and productivity of lactating dairy cows. Twelve freestall-housed, lactating Holstein dairy cows, including 6 primiparous (PP) and 6 multiparous (MP), milked 3×/d (at 1400, 2200, and 0600h), were exposed to each of 3 treatments (over 21-d periods) in a replicated Latin square design. Treatments included feed delivery frequency of (1) 1×/d (at 1400 h), (2) 2×/d (at 1400 and 2200 h), and (3) 3×/d (at 1400, 2200, and 0600 h). Milk production as well as feeding, lying, and rumination behaviors were electronically monitored for each animal for the last 7 d of each treatment period. Milk samples were collected for the last 3 d of each period for milk component analysis. Dry matter intake (DMI) varied with feed delivery frequency, with greatest DMI observed in cows fed 3×/d (27.8 kg/d) compared with those fed 2×/d (27.0 kg/d) or 1×/d (27.4 kg/d). Treatment had no effect on milk yield (41.3 kg/d) or efficiency of production (1.54 kg of milk/kg of DMI). Cows that did not receive delivery of feed following the 2200 h milking (treatment 1) and 0600 h milking (treatments 1 and 2) had lower DMI during the first hour after milking than those that received feed at all milkings (treatment 3). Total feeding time and meal frequency, size, and duration did not vary by treatment, but PP cows consumed smaller meals at a slower rate, resulting in lower DMI compared with MP cows. Primiparous cows consumed 50.1% and 26.1% less dry matter than MP cows during the first meal following the first and second milkings, respectively. Lying time did not vary by treatment, but PP cows spent more time lying (10.3 vs. 8.3 h/d) than MP cows. Under 3×/d milking schedules, greater feed delivery frequency resulted in greater DMI as a function of increased DMI following the return from milking and the delivery of feed.     

Performance of dairy cows fed diets formulated at 2 starch concentrations with either canola meal or soybean meal as the protein supplement

This study was designed to evaluate the effects of substituting corn grain with nonforage fiber sources in diets containing soybean meal (SBM) or canola meal (CM) as the primary protein source. Sixteen Holstein cows were assigned to a replicated 4 × 4 Latin square design with 4 periods of 28 d each. Treatments were arranged as a 2 × 2 factorial with 2 protein sources (SBM and CM) and 2 dietary starch concentrations (21 and 27% dry matter, DM). Diets were formulated to contain 16.5% CP, and the 21% starch diets were obtained by replacing corn grain with soybean hulls and beet pulp. Protein source × starch interactions were observed for DM intake (DMI), milk fat and protein concentrations, milk protein yield, milk urea nitrogen, and feed efficiency. Cows fed CM diets had a higher DMI when dietary starch concentration was 27% compared with 21%, but those cows had DMI similar to that of cows on SBM diets regardless of the starch concentration. Milk fat percentage was decreased in cows fed CM with 27% starch compared with cows fed CM with 21% starch and cows fed SBM with 27% starch. Milk protein percentage and yield and milk lactose percentage were least in cows fed CM with 21% starch compared with the other 3 diets, but feed efficiency was greater for cows fed CM with 21% starch. Milk urea nitrogen was least in cows fed CM with 27% starch compared with the other 3 diets. Cows fed diets with 27% starch produced 2.5 kg/d more milk and 1.9 kg/d more energy-corrected milk compared with cows fed 21% starch. Digestibility of DM and organic matter was higher in cows fed SBM diets than in cows on CM diets, and cows fed 27% starch showed greater DM and organic matter digestibility than cows on 21% starch. Digestibility of neutral detergent fiber and acid detergent fiber was greater in diets with SBM than in those with CM. Molar proportion of acetate was the lowest for cows fed CM with 21% starch compared with cows fed SBM with 21% starch, with the remaining cows fed being intermediate and similar. However, propionate was highest for cows fed CM with 21% starch than for cows fed SBM with 21% starch, but the remaining treatments were intermediate and similar. Isobutyrate was greater for cows fed CM with 21% starch, which resulted in the lowest acetate:propionate ratio compared with cows fed the remaining treatments. Overall, we confirmed that the interaction of protein with starch in CM diets can sustain similar cow performance as with the SBM diets. Those making decisions about starch concentration and protein source should consider feed price when SBM or CM and different starch levels are being formulated in diets for lactating dairy cows.     

Interactions of monensin with dietary fat and carbohydrate components on ruminal fermentation and production responses by dairy cows

Variation in milk fat percentage resulting from monensin supplementation to lactating dairy cows could be due to altered ruminal fermentation with interactions of monensin with ruminal biohydrogenation of fat and ruminal carbohydrate availability. The objective of the study was to determine the effects of feeding monensin as Rumensin (R) in diets differing in starch availability (ground or steam-flaked corn), effective fiber (long or short alfalfa hay, LAH or SAH), and 4% fat (F) from distillers grains, roasted soybeans, and an animal-vegetable blend on ruminal fermentation characteristics and milk production in lactating dairy cows. Six ruminally cannulated lactating Holstein cows were used in a balanced 6 × 6 Latin square design with 21-d periods. The cows were fed 6 diets: (1) C = control diet with ground corn and LAH, (2) CR = C plus R, (3) CRFL = CR plus F, (4) CRFS = ground corn, R, F, and SAH, (5) SRFL = steam-flaked corn, R, F, and LAH, and (6) SRFS = steam-flaked corn, R, F, and SAH. Mean particle size of LAH was 5.00 mm and 1.36 mm for SAH. All diets were formulated to have 21% forage NDF and 40% NFC. The R tended to decrease DMI, decreased milk fat yield, and numerically lowered milk fat percentage (3.41 vs. 2.98%). Addition of F to R diets did not affect milk fat percentage. By feeding diets containing R and F, SAH tended to increase milk fat percentage for the ground-corn diet, but SAH tended to decrease milk fat percentage with steam-flaked corn (CRFL + SRFS vs. CRFS + SRFL). The steam-flaked corn increased total-tract NDF digestibility (CRFL + CRFS vs. SRFL + SRFS; 51.1 vs. 56%). Addition of F with R decreased total VFA concentration and increased rumen pH. Fat addition with R decreased rumen NH₃N and MUN (12.8 vs. 13.9 mg/dL), and SFC decreased NH₃N concentration compared with ground corn. Although R caused milk fat depression, addition of F did not further exacerbate milk fat depression. Fatty acid analysis did not implicate any particular biohydrogenation intermediate as the causative factor for the milk fat depression.     

Effect of water addition to a total mixed ration on feed temperature, feed intake, sorting behavior, and milk production of dairy cows

The objective of this study was to determine the effects of water addition to a high-moisture total mixed ration (TMR) on feed temperature, feed intake, feed sorting behavior, and milk production of dairy cows. Twelve lactating Holstein cows (155.8 ± 60.1 DIM), individually fed once daily at 1000 h, were exposed to 3 diets in a Latin square design with 28-d treatment periods. Diets had the same ingredient composition [30.9% corn silage, 30.3% alfalfa haylage, 21.2% high-moisture corn, and 17.6% protein supplement; dry matter (DM) basis] and differed only in DM concentration, which was reduced by the addition of water. Treatment diets averaged 56.3, 50.8, and 44.1% DM. The study was conducted between May and August when environmental temperature was 18.2 ± 3.6°C and ambient temperature in the barn was 24.4 ± 3.3°C. Dry matter intake (DMI) was monitored for each animal for the last 14 d of each treatment period. For the final 7 d of each period, milk production was monitored, feed temperature and ambient temperature and humidity were recorded (daily at 1000, 1300, and 1600 h), and fresh feed and orts were sampled for determination of sorting. For the final 4 d of each period, milk samples were taken for composition analysis. Samples taken for determining sorting were separated using a Penn State Particle Separator that had 3 screens (19, 8, and 1.18 mm) and a bottom pan, resulting in 4 fractions (long, medium, short, and fine). Sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. Greater amounts of water added to the TMR resulted in greater increases in feed temperature in the hours after feed delivery, greater sorting against long particles, and decreased DMI, reducing the overall intake of starch and neutral detergent fiber. Milk production and composition were not affected by the addition of water to the TMR. Efficiency of production of milk was, however, increased with greater amounts of water added to the TMR. The increases in feed temperature in the hours after feed delivery were enhanced by higher ambient temperatures; this may be indicative of feed spoilage and thus may have contributed to the reduced DMI observed. Overall, these results suggest that the addition of water to high-moisture TMR (less than 60% DM) containing primarily haylage and silage forage sources will not always discourage cows from sorting, but rather may increase this behavior and limit the nutrient consumption of cows, particularly when ambient temperature is high.