Effect of scraping frequency in a freestall barn on volatile nitrogen loss from dairy manure.

The objective of this investigation was to evaluate the effect of scraping frequency (2x vs. 6x daily) on N volatilization from manure on the floor of a dairy free-stall barn. Three trials (crossover design) were conducted in the summers of 2001 and 2002, and in the winter of 2003. Nitrogen volatilization was estimated from the change in the N:P ratio in excreta at the time of excretion to the time when manure was scraped from the barn. Total N loss was considered a maximum estimate of NH3-N loss, because small amounts of nonammonia N may be volatilized. Nitrogen was determined after manure subsamples were lyophilized; P content was measured by direct current emission spectroscopy of ashed subsamples of manure. Lactating dairy cows were fed high-protein (18.5 to 19.3% crude protein), alfalfa-based diets. Average milk yield was 31.9 (SD = 7.4) kg/d. Scraping frequency had no effect on N loss in summer 2001. An average of 41% of excreted N, or 238 +/- 19.0 g of N/d per cow, was volatilized. For the trial in summer 2002, nitrogen volatilization was reduced from 50% of the excreted N with 2x to 46.7% with 6x, equivalent to 265 and 248 g of N lost/d per cow, respectively. Scraping had no effect on N volatilization during the winter trial. An average of 17.7% of excreted N was volatilized during the winter, equivalent to 109 +/- 11.0 g of N lost/d per cow. Scraping frequency of manure had little or no effect on N loss from manure in a freestall barn. Nitrogen loss during the winter was less than half of the loss during the summer.

Relationship between level of milk production and multiple ovulations in lactating dairy cows.

Our objective was to evaluate factors associated with spontaneous multiple ovulations in lactating dairy cows. Ovaries of cows [n = 267; >50 days in milk (DIM)] were evaluated weekly using ultrasound to determine spontaneous (i.e., no hormonal treatment) ovulation rate starting at 50 DIM and continuing until pregnancy diagnosis. Cows were fitted with a transmitter to record standing activity during estrus, and serum progesterone concentration was assessed weekly starting at wk 1 postpartum for all cows. Overall, 76 (28.5%) cows were anovular and 191 (71.5%) were ovular by 71 DIM. Incidence of anovulation was not associated with level of milk production but was associated with lower body condition. For anovular cows (n = 41) that spontaneously recovered, the multiple ovulation rate at first ovulation was 46.3%. For second and subsequent ovulations (n = 463), the level of milk production for 14 d preceding estrus was associated with increased ovulation rate. To illustrate, incidence of multiple ovulations was 1.6% (2/128), 16.9% (32/189), and 47.9% (70/146) for ovulations when cows were producing <35, 35 to <45, and >or=45 kg/d, respectively. Among cows for which estrous behavior was recorded, those with multiple ovulations (n = 48) had shorter duration of estrus (4.3 +/- 0.7 vs. 9.9 +/- 0.5 h) and higher production (47.2 +/- 0.9 vs. 38.1 +/- 0.5 kg/d) than cows with single ovulations (n = 237). Circulating concentrations of estradiol were lower (5.5 +/- 0.3; n = 15 vs. 7.8 +/- 0.4 pg/mL; n = 71) during periods of estrus with multiple ovulations despite a greater preovulatory follicular volume (4136 +/- 123 vs. 3085 +/- 110 mm(3)). Similarly, serum progesterone concentration 7 d after estrus was lower for cows with multiple than single ovulations (2.5 +/- 0.3 vs. 3.2 +/- 0.1 ng/mL) despite a greater luteal volume (8291 +/- 516 vs. 6405 +/- 158 mm(3)). In summary, the first spontaneous ovulation in anovular cows and a higher level of milk production for 14 d preceding estrus were associated with increased multiple ovulation rate. Additionally, cows with multiple ovulations had lower estradiol at estrus, a shorter duration of estrus, and lower progesterone at 7 d after estrus than cows with single ovulations.

The effect of diets on milk production and composition, and on lactation curves in pastured dairy goats.

A 2-yr study investigated effects of different levels of concentrate supplementation on milk production, composition, and lactation curves in pastured dairy goats. For both years, 44 Alpine goats (Capra hircus; 55 +/- 11 kg body weight) were randomly allocated to 4 groups. Animals were supplemented with 0.66 (treatments A and B), 0.33 (treatment C), or 0 kg of concentrate (treatment D) per kg of milk over 1.5 kg/d. Mixed vegetative forages were rotationally grazed by the goats (treatments B, C, and D), except that treatment A was confined and fed alfalfa hay. Individual milk production was recorded daily, and milk samples were collected once every 2 wk for the 7-mo period (March to September) and analyzed for fat, protein, lactose, urea-N, nonesterified fatty acids, and allantoin (second year only). Milk yield and composition varied among dietary treatments, with some measures affected by year. Average daily milk yield was lowest for treatment D. The increased level of concentrate supplementation in treatment A led to 22% greater milk yield compared with treatment D. Milk production increased by 1.7 and 0.9 kg for each additional kilogram of concentrate fed per day during the first and second years, respectively. Average peak yield, time of peak yield, and persistency were lower for treatment D than for other treatments. The percentage of milk fat was lower for treatment D than for other treatments. Concentration of milk protein was greater for treatments A and B during the first year, and was higher for treatment C than for other treatments during the second year. Average milk lactose concentration was higher for treatments B and C than for other treatments. However, milk urea-N concentration in treatment A was higher than other treatments. Milk allantoin, used to estimate microbial proteins synthesis, was 20 to 25% greater for treatment A than for other treatments. Averaged across year, plasma urea-N and nonesterified fatty acids concentration were lowest for treatment B. Average organic matter intake was similar among treatments during both years. Ratios of acetate and propionate concentrations for treatment A were lowest among treatments. In conclusion, milk production and composition were affected by the feeding treatment and year. Increased level of nutrition lead to an increase in daily milk yield, peak yield, time of peak yield, and persistency compared with treatment D. Alpine dairy goats grazing on fresh forages without concentrate supplementation can produce milk inexpensively, and response to concentrate supplementation is greater for low quality pasture.

Relationship between level of milk production and estrous behavior of lactating dairy cows.

The objective of this study was to determine if there is an association between level of milk production and duration of estrus as determined by standing activity recorded by a radiotelemetry system. Holstein cows (n = 267; 50 DIM) were fitted with a transmitter that allowed continuous recording of standing activity. Cows were housed in a free-stall barn and milked twice daily. Ovulation was confirmed for all estruses (n = 380). Average milk production for the 10 days before the day of estrus was used to classify cows as lower (< 39.5 kg/day) or higher (>/= 39.5 kg/day) producers at the time of estrous expression. Follicle size and serum estradiol (E(2)) concentrations were determined in a subset of cows (n = 71) on the day of estrus. Duration (6.2 +/- 0.5 h versus 10.9 +/- 0.7 h; P < 0.0001), standing events (6.3 +/- 0.4 versus 8.8 +/- 0.6; P = 0.001), and standing time (21.7 +/- 1.3 s versus 28.2 +/- 1.9 s; P = 0.007) were shorter for estruses from higher (46.4 +/- 0.4 kg/day; n = 146) than lower producers (33.5 +/- 0.3 kg/day; n = 177). Milk production was correlated with the duration of estrus (r = -0.51; P < 0.0001; n = 323). Higher producers had lower E(2) concentrations than lower producers (6.8 +/- 0.5; n = 31 versus 8.6 +/- 0.5 pg/ml; n = 40; P = 0.01) in spite of larger pre-ovulatory follicle diameter (18.6 +/- 0.3; n = 31 versus 17.4 +/- 0.2 mm; n = 40; P 0.004). Interestingly, E(2) concentrations were not correlated with diameter of the pre-ovulatory follicle (r = -0.17; P = 0.15) but milk production was correlated with both E(2) concentrations (r = -0.57; P < 0.0001) and diameter of the pre-ovulatory follicle (r = 0.45; P < 0.0001). Thus, high milk production decreases duration of estrus probably due to decreased circulating concentrations of E(2).

Comparison of conventional linted cottonseed and mechanically delinted cottonseed in diets for dairy cows.

Performance of lactating dairy cows fed diets containing either mechanically delinted whole cottonseed (DWCS; 3.7% lint) or linted whole cottonseed (LWCS; 11.7% lint) was measured. Forty primiparous (86 +/- 39 d in milk) and 40 multiparous (88 +/- 30 d in milk) cows were fed a total mixed ration containing 13% (dry matter basis) DWCS or LWCS in two blocks of 112 d (n = 53 and 27, respectively). Other total mixed ration ingredients (dry matter basis) were corn silage (28.1%), alfalfa silage (23%), high moisture shelled corn (27.8%), soybean meal (1.8%), expeller soybean meal (1.8%), blood meal (2%), and mineral-vitamin supplements (2.5%). Dry matter intake and milk yield were measured daily and milk composition every other week. Fecal grab samples were taken during wk 3 and 13 of each block to estimate excretion of intact whole cottonseeds. Milk yield, 3.5% fat-corrected milk, energy-corrected milk, milk composition and dry matter intake were not affected by whole cottonseed source. Body condition score tended to increase more with DWCS (0.22 vs. 0.11) for primiparous cows, although this was not reflected in body weight change. Dry matter digestibilities, based on indigestible ADF, were 63.5 and 64.8% for the DWCS and LWCS diets. It was calculated that 2.5 and 1.5% of the consumed seeds were excreted as whole cottonseeds in feces with the DWCS and LWCS diets, respectively. Although statistically significant, treatment differences in the proportion of intact seeds in the fecal DM would have little nutritional consequence. Mechanically delinted WCS performed as well as LWCS for all of the cow performance and milk composition variables measured.

Reproductive performance of dairy cows fed two concentrations of phosphorus.

The objective of this study was to determine the effect of dietary P concentrations of 0.37 (recommended) or 0.57% (excess; dry matter basis) on reproductive performance. At calving, Holstein cows were randomly assigned to 1 of 2 dietary treatments (n = 134 for 0.37% P and n = 133 for 0.57% P). Cows were fitted with a radiotelemetric transmitter (50 d in milk [DIM]) to record mounting activity during estrus and bred to natural estrus from 50 to 100 DIM, then to synchronized estrus (Ovsynch protocol) after 100 DIM. Weekly ultrasonography was performed from 50 DIM until pregnancy was diagnosed (-30 d after artificial insemination). Pregnancy was confirmed approximately 60 d after artificial insemination (artificial insemination). Weekly blood samples were analyzed for progesterone concentrations. Days to first increase (>1 ng/ml) in progesterone, days to first estrus detected by radiotelemetry, days to first service detected by herd personnel, and conception rate at first service did not differ between the recommended and excess P groups, respectively. Similarly, conception rate at 30 d, days open, pregnancies lost from 30 to 60 d, multiple ovulation rate, and the incidence of anovulatory condition at 71 DIM did not differ between these groups. The mean duration of estrus was 8.7 +/- 0.5 and 8.7 +/- 0.7 h, and the average number of mounts per estrus was 7.4 +/- 0.5 and 7.8 +/- 0.5 for a total mounting time during estrus of 25.8 +/- 1.8 and 24.5 +/- 1.6 s for cows fed the recommended and excess P diet, respectively. Phosphorus treatment had no detectable effect on reproductive performance.

Effect of dietary phosphorus on performance of lactating dairy cows: milk production and cow health.

The objective of this study was to measure cow response to feeding of two dietary concentrations of P, one of which was close to recent National Research Council requirements, and the other of which was well in excess of the requirement. Diets containing 0.37 or 0.57% P (dry basis) were fed to Holstein cows for the first 165 d of lactation, and occasionally longer until cows were confirmed pregnant approximately 60 d after insemination. At calving, cows were randomly assigned to experimental diets. The number of cows completing a minimum of 165 d of lactation was 123 for the 0.37 and 124 for the 0.57% P groups. Cows were housed in a stanchion barn and fed one of two transition diets, each formulated to contain one of the P treatments for the first 3 wk of lactation, and then cows were moved to a free-stall barn where the experimental diets were group fed. Milk production, milk fat, and milk protein averaged 35.1 kg/d, 3.92%, and 2.90% for the 0.37% P diet, and 34.9 kg/d, 3.98%, and 2.91% for the 0.57% P diet. None of these measures were different between treatments. Blood serum P concentrations on d 50 and 100 of lactation averaged 6.1 and 6.2 mg/dL for the 0.37% P diet, and 6.8 and 6.9 mg/dL for the 0.57% P diet. No treatment differences were detected in milk production, cow health, or body condition score.

Effect of dietary phosphorus concentration on estrous behavior of lactating dairy cows.

The objective of this study was to determine the effect of dietary phosphorus (P) concentrations of 0.38 (adequate) or 0.48% (excess) of the total mixed ration (TMR) (dry matter basis) on estrous behavior of lactating cows as measured by a radiotelemetric system (HeatWatch; De Forest, WI, USA). At calving, 42 Holstein cows (n=21 per treatment) were randomly assigned to one of two dietary P treatments. Cows were milked twice daily and milk weights were recorded. Cows were housed in a free-stall barn and were fitted with a radiotelemetric transmitter 40 days postpartum to record estrous mounting activity. The total number of estruses recorded for the 42 cows were 72 (37 and 35 for cows in the adequate and excess P groups, respectively). The mean duration of estrous cycles was 22 +/- 0.6 days and 21 +/- 0.4 days for cows fed the adequate and excess P diets, respectively (P=0.14). The mean duration of estrus was 8.9 +/- 1.1 h and 8.6 +/- 1.2 h (P=0.86), the average number of mounts during estrus was 7.0 +/- 1.2 and 8.2 +/- 1.7 (P=0.57), and the total mounting time was 27.1 +/- 4.3 s and 30.8 +/- 6.5 s (P=0.64) for cows fed the adequate and excess P diets, respectively. Phosphorus treatment had no significant effect on intensity or duration of estrus.

Produçäo de leite de vacas alimentadas com alta proporçäo de forragem em dietas / Feeding high forage diets to lactating dairy cows

Vinte e duas vacas primíparas e 26 multíparas da raça Holandesa foram distribuídas em três tratamentos em um delineamento inteiramente ao acaso. As dietas testadas consistiram de duas proporçöes forragem:concentrado, 55:45 (RCS) e 75:25 (RCSH), para silagem de milho comum, e 75:25 (BMR) para outra dieta baseada no híbrido bm3. Näo houve interaçäo entre tratamentos e ordem de lactaçäo. A proporçäo silagem de alfafa:silagem de milho na porçäo forrageira da dieta foi de 47,7:53,3. A ingestäo (kg/dia) de matéria seca e de proteína bruta foi superior para BMR e RCS (19,5 e 19,5; 3,41 e 3,42, respectivamente) em relaçäo à ingestäo para RCSH (17,6 e 3,14), enquanto que a de fibra em detergente neutro foi maior para BMR (6,61) e menor para RCSH e RCS (6,08 e 5,40, respectivamente). O consumo de fibra em detergente ácido (kg/dia) foi maior para BMR e RCSH (4,88 e 4,73) e menor para RCS (4,02). A produçäo de leite foi superior para o tratamento com maior proporçäo de concentrados (35,7kg/vaca/dia), seguida pelo tratamento BMR (34,1kg/vaca/dia) e finalmente por RCSH, com a menor produçäo (32,1kg/vaca/dia). O teor de gordura no leite foi superior nos tratamentos com alto conteúdo de forragem na dieta, enquanto que a porcentagem de proteína seguiu padräo oposto. O híbrido bm3, em dieta contendo alta proporçäo de forragem, foi eficiente em manter o nível de desempenho de vacas de alta produçäo em comparaçäo à dietas com relaçöes forragem:concentrado normal ou alta e baseadas em híbridos contendo diferente genética de milho

Production and feeding strategies for phosphorus management on dairy farms.

Long-term accumulation of soil phosphorus (P) is becoming a concern on some watersheds heavily populated with animal feeding facilities, including dairy farms. Management changes in crop production and feeding may help reduce the accumulation of excess P, but farm profitability must be maintained or improved to assure adoption of such changes. Whole-farm simulation was used to evaluate the long-term effects of changes in feeding, cropping, and other production strategies on P loading and the economics of 100-cow and 800-cow dairy farms in southeastern New York. Simulated farms maintained a long-term P balance if the following occurred: 1) animals were fed to meet recommended minimum amounts of dietary P, 2) the cropping strategy and land base supplied all of the forage needed, 3) all animals were fed a high forage diet, and 4) replacement heifers were produced on the farm to utilize more forage. The most easily implemented change was to reduce the supplemental mineral P fed to that required to meet current NRC recommended amounts, and this provided an annual increase in farm profit of about $22/cow. Intensifying the use of grassland and improving grazing practices increased profit along with a small reduction in excess P. Conversion from dairy production to heifer raising or expansion from 100 cows to a 250-cow "state-of-the-art" confinement facility (with a 70% increase in land area) were also profitable options. These options provided a long-term P balance for the farm as long as the production and use of forage was maximized and minimum dietary P amounts were those recommended by the NRC. Thus, management changes can be made to prevent the long-term accumulation of soil P on dairy farms while improving farm profitability.

Cracked dry or finely ground high moisture shelled corn as a supplement for grazing cows.

Feeding shelled corn as the primary supplement in cracked dry form or ground high moisture form to grazing cows was studied in an experiment using 32 cows in late lactation. Each of the two forms of corn accounted for 74.7% of the concentrate supplement, which was fed at 9 kg/d (DM). The experiment was 13 wk, during which cows grazed permanent native pasture containing mostly grasses and some clover. Milk yield was 2.4 kg/d higher for cows fed ground high moisture shelled corn than for those fed dry cracked shelled corn. Milk fat content was lower (3.28 vs. 3.67%), but protein content was higher (3.26 vs. 3.15%) for the high moisture corn supplement. Results suggest that high moisture corn can serve as a better supplement for grazing cows than dry corn, likely by providing more metabolizable energy and microbial protein due to more fermentable and digestible starch.

Milk production, estimated phosphorus excretion, and bone characteristics of dairy cows fed different amounts of phosphorus for two or three years.

Diets containing 0.31, 0.39, or 0.47% P on a DM basis were fed to 10, 14, and 13 multiparous Holstein cows, respectively, for a full lactation. Most of the cows (33) were fed similar amounts of P in the previous one or two lactations. The objective was to obtain information on bone integrity after prolonged feeding of different amounts of P. At the end of the experiment, a section (-20 cm) of the 12th rib was surgically removed. The bone was tested for strength and analyzed for ash and P content. The shear strength and the energy required to deform the bone to the point of fracture did not differ among treatments. Bone specific gravities were 1.50, 1.57, and 1.55 for the three treatments. Ash and P content of the bone, measured in wet weight, dry weight, and wet bone volume, were similar for the 0.39 and 0.47% P treatments, but tended to be lower with the 0.31% P treatment. Milk production of cows in all groups was high, averaging >11,900 kg for the 308-d lactation. Feeding P at 0.31% of dietary DM over two to three lactations appeared to decrease P concentration of bone, but the decrease was not severe enough to affect bone strength. Dietary P at 0.39% did not affect bone P content or strength. Dietary P content of 0.31% appears to be borderline deficient for cows producing >11,900 kg/308 d.

Milk production of fall-calving dairy cows during summer grazing of grass or grass-clover pasture.

Milk production of fall-calving dairy cows during subsequent summer grazing was evaluated in two consecutive years using a total of 80 mid- to late-lactation Holsteins. Cows calved during September and October and grazed from April to August in the following year. In yr 1, 27 cows grazed a native grass pasture and 13 cows grazed a native grass-clover mixed pasture containing 26% red clover and white clover. In yr 2, 40 cows grazed native grass pasture as one group. Also, cows in yr 2 were administered bovine somatotropin, whereas in yr 1, no bST was used. Grazing cows also were fed concentrate supplements at 6.2 kg/d of dry matter (DM) in yr 1 and 7.9 kg/d of DM in yr 2 to provide 35 to 40% of total intake. Average daily milk during the grazing period decreased 3.6 kg in yr 1 and 7.7 kg in yr 2 when compared with milk yield extrapolated from the lactation curve established 10 wk before being turned out to pasture. Estimated DM intake during grazing was also less than what would have been expected had cows continued on a total mixed ration in confinement. Cows grazing the mixed pasture of grass and clover yielded 1.3 kg/d more milk than those grazing the grass pasture in yr 1. A decrease in milk resulting from the change from total mixed ration fed in confinement to grazing supplemented with concentrates was not avoided with these mid- to late-lactation cows, but the cumulative loss over the lactation was less than with early lactation cows in a companion study. Clover enhances the grazing value of pasture when grown with grasses.

Effects of corn particle size and source on performance of lactating cows fed direct-cut grass-legume forage.

We conducted two experiments to evaluate the effects of corn supplementation, source of corn, and corn particle size on performance and nutrient utilization of lactating dairy cows. In experiment 1, treatments were 1) direct-cut grass-legume forage without supplement, 2) direct-cut forage plus 10 kg DM of ground dry shelled corn-based concentrate, and 3) direct-cut forage plus 10 kg DM of coarsely ground high moisture ear corn-based concentrate. In experiment 2, treatments were 1) direct-cut grass-legume forage plus 10 kg DM of ground dry shelled corn-based concentrate, 2) direct-cut forage plus 10 kg DM of coarsely ground high moisture ear corn-based concentrate, and 3) direct-cut forage plus 10 kg of DM finely ground high moisture ear corn-based concentrate. Both experiments were designed as 3 x 3 Latin squares replicated three times. In experiment 1, yields of milk and milk protein increased with concentrate supplementation, but were not affected by source of corn. Solids-corrected milk yield tended to increase with grain supplementation. Dry matter intake increased with concentrate supplementation, but was not affected by source of corn or corn particle size. Corn supplements decreased ruminal pH and acetate to propionate ratio and increased ruminal propionate concentration. Grain supplements reduced ruminal ammonia concentration, increased concentration of urine allantoin, and increased the urinary allantoin to creatinine ratio. In the second study, fine grinding of high moisture corn reduced fecal starch plus free glucose levels and tended to increase its apparent digestibility. In both experiments, starch plus free glucose intake was higher on the diets with dry corn, but its utilization was not affected by source of corn.

Influence of mechanical processing on utilization of corn silage by lactating dairy cows.

We conducted three experiments to determine the influence of mechanical processing on corn silage utilization by lactating dairy cows. Total mixed rations contained either unprocessed or processed corn silage harvested between 1/4 and 3/4 milk line. In trial 1, 12 multiparous Holstein cows were used in a replicated double switchback design with 21-d periods. Intake of dry matter (DM) was increased 1.2 kg/d by processing, but milk yield was unaffected. Processing did not affect apparent total-tract DM digestibility, but processing tended to lower starch and corn excretion in feces and reduced concentration of sieved corn kernel particles in feces. In trial 2, 42 Holstein cows were used in an 18-wk randomized complete-block design. Intake of DM and milk yield were unaffected by processing, but milk fat percent was increased 0.35 percentage units by processing. Processing tended to increase total-tract digestibility of starch, but reduced organic matter, crude protein, and neutral detergent fiber digestibilities. In trial 3, 30 Holstein cows were used in a 15-wk randomized complete block design. There was no influence of mechanical processing on intake or lactation performance in this trial. Despite indications of increased starch digestion in two trials and increased DM intake in one trial, effects of processing corn silage on lactation performance were minimal with corn silage at the maturity and moisture contents used in these trials.

Milk production, reproductive performance, and fecal excretion of phosphorus by dairy cows fed three amounts of phosphorus.

Milk production was measured and phosphorus (P) excretion in feces was estimated in dairy cows fed three amounts of P. A basal diet was formulated to contain 0.31% P (DM basis). Sodium monophosphate replaced corn in the basal diet to give two additional diets containing 0.40 and 0.49% P. The diets were fed to eight, nine, and nine multiparous Holsteins from the beginning to the end of lactation. Milk yields for the 308-d lactation were 10,790, 11,226, and 11,134 kg for the three treatments, respectively. The lowest milk yield resulted from decreased milk production during late lactation with the 0.31% P group. Reproductive performance of the cows was not related to dietary P content. Fecal P concentration, determined in wk 2, 4, 6, 8, 23, and 40 of lactation, increased as dietary P intake was increased. Cows fed the lowest P diet conserved P by minimizing P excretion in feces and urine, whereas cows in the other two treatments excreted more P through these routes. A reduction in dietary P from 0.49 to 0.40% reduced fecal P excretion by 23%. Apparent P digestibilities of less than 40% are indicative of surplus dietary P. Feeding 0.40% P appeared sufficient to maintain P balance and the level of milk production achieved in this experiment. An example is given which illustrates the relationship between dietary and fecal P.

Conjugated linoleic acid (CLA) content of milk from cows offered diets rich in linoleic and linolenic acid.

Two experiments were conducted to determine the conjugated linoleic acid (CLA) content of milk from cows offered diets rich in linoleic and linolenic acid. In experiment 1, 36 cows were assigned to a control and five treatment groups. Cows in the control group received a diet containing 51% forage and 49% grain on a dry matter basis. In the treatment group, grain was partly replaced by either 18% raw cracked soybeans, 18% roasted cracked soybeans, 3.6% soybean oil, 2.2% linseed oil, or 4.4% linseed oil. Experimental diets were fed for 5 wk. Average CLA contents in milk fat from wk 2 through 5 were 0.39% in control and 0.37, 0.77, 2.10, 1.58, and 1.63% of total fatty acids in the raw soybean, roasted soybeans, soybean oil, 2.2% linseed oil, and 4.4% linseed oil treatments, respectively. In experiment 2, 36 cows were assigned to a control and 5 treatment groups. Cows in the control group received a diet containing 55% forage and 45% grain. In the treatment groups, grain was partly replaced by soybean oil at 0.5, 1.0, 2.0, 4.0, or by linseed oil at 1.0% of the dietary dry matter. Experimental diets were fed for 5 wk. Average CLA contents in milk fat from wk 2 through 5 were 0.50% in control and 0.75, 0.76, 1.45, 2.08, and 0.73% of total fatty acids in 0.5, 1.0, 2.0, 4.0 soybean oil and 1.0% linseed oil treatments, respectively. Diets rich in linoleic or linolenic acid can increase CLA content of milk when dietary oil is accessible to the rumen microorganisms.

Milk production during the complete lactation of dairy cows fed diets containing different amounts of protein.

Milk production response to four different amounts of protein supplementation was measured in a complete lactation study utilizing 58 multiparous Holstein cows treated with bovine somatotropin. The four treatments were as follows (the first number is the dietary crude protein content (% of dry matter) during the first 16 wk of lactation and the second number is the protein content for wk 17 to 44 of lactation): 15.4-16.0, 17.4-16.0, 17.4-17.9, and 19.3-17.9. Diets were formulated to maximize the supply of amino acids to the intestine. High moisture ear corn was finely ground to promote ruminal fermentation and microbial protein synthesis, and roasted soybeans and expeller processed soybean meal were used as the protein supplements to provide relatively high amounts of rumen-undegradable protein. Alfalfa silage and corn silage (3:2) provided the forage. Milk production for the 308-d lactation for each of the treatment groups was 10,056, 10,831, 11,095, and 11,132 kg. Cows of this production level fed diets similar to those used in this experiment benefit from dietary protein of approximately 17.5% during the first 30 wk of lactation. A reduction in dietary protein to 16% can be made around wk 30 of lactation. This amount of dietary protein should, with prevailing feed prices, be compatible with maximum profit and a moderate amount of nitrogen excretion to the environment.

Milk production and reproductive performance of dairy cows fed two concentrations of phosphorus for two years.

The performance of lactating Holstein cows in response to P supplementation was determined in a 2-yr study. Each year included confinement feeding for approximately the first two-thirds of lactation and grazing for the remaining one-third of lactation. In yr 1, 42 cows were assigned at calving to a low or high P diet within parity. Fourteen cows from the low P group and 16 cows from the high P group continued with their treatments for a second year. Also in the second year, 12 new cows were included in the low P group and 11 in the high P group. Thus, a total of 95 lactations with 65 cows were used in the trial, and 30 of the cows were used in both years. The dietary P was 0.38 and 0.48% during confinement feeding and approximately 0.31 and 0.44% during grazing for the low and high P treatments (dry basis). When all cows were used to obtain treatment means, milk yield for 308 d of lactation was 9131 and 8860 kg in yr 1, and 9864 and 9898 kg in yr 2 for the low P and high P groups, respectively. Blood serum inorganic P tended to be slightly lower for the low P than for the high P group during most of lactation; all concentrations (5.6 to 7.4 mg/dl) were within normal ranges. Reproductive measures were similar between groups in both years. When just the cows completing two lactations (N = 30) were evaluated, milk yield was 9072 and 8780 kg in yr 1 and 11,457 and 11,358 kg in yr 2 for the low P and high P treatments, respectively. Reducing dietary P from 0.48 to 0.38% for 2 yr did not impair milk production or reproductive performance.

Effect of coarse or fine grinding on utilization of dry or ensiled corn by lactating dairy cows.

This study evaluated the effect of coarse or fine grinding of three forms of corn on the performance of lactating cows. Six diets, fed as total mixed rations, were identical except for the corn portion of the diet. Corn treatments were dry shelled corn, high moisture ensiled ear corn, and high moisture ensiled shelled corn, either coarsely or finely ground. The experimental design was a 6 x 6 Latin square with 36 cows. Eighteen cows were assigned to the six different treatments and were fed once daily. Within this group of 18 cows, six had a ruminal cannula and were used to evaluate nutrient digestibilities and ruminal fermentation. The remaining 18 cows, six of which were ruminally cannulated, were similarly assigned, except they were fed twice daily. In the group fed once daily, milk production and composition were not affected by treatment. Starch digestibility was greater with the high moisture and with the finely ground corn treatments. In addition, the high moisture ensiled corn treatments had reduced ruminal ammonia concentrations. In the group that was fed twice daily, milk production and protein yield were greatest for the finely ground high moisture ensiled shelled corn treatment. Starch utilization was improved by fine grinding. Lower ruminal ammonia concentrations were obtained with the high moisture ensiled corn treatments, and there was a tendency for reduced ammonia concentration with fine grinding. Results indicate that high moisture ensiled corn as well as fine grinding improved nitrogen and starch utilization.