Effect of kernel processing and particle size of whole-plant corn silage with vitreous endosperm on dairy cow performance.

Kernel processing and theoretical length of cut (TLOC) of whole-plant corn silage (WPCS) can affect feed intake, digestibility, and performance of dairy cows. The objective of this study was to evaluate for lactating dairy cows the effects of kernel processing and TLOC of WPCS with vitreous endosperm. The treatments were a pull-type forage harvester without kernel processor set for a 6-mm TLOC (PT6) and a self-propelled forage harvester with kernel processor set for a 6-mm TLOC (SP6), 12-mm TLOC (SP12), and 18-mm TLOC (SP18). Processing scores of the WPCS were 32.1% (PT6), 53.9% (SP6), 49.0% (SP12), and 40.1% (SP18). Twenty-four Holstein cows (139 ± 63 d in milk) were blocked and assigned to six 4 × 4 Latin squares with 24-d periods (18 d of adaptation). Diets were formulated to contain 48.5% WPCS, 15.5% citrus pulp, 15.0% dry ground corn, 9.5% soybean meal, 6.8% low rumen degradability soybean meal, 1.8% calcium soap of palm fatty acids (FA), 1.7% mineral and vitamin mix, and 1% urea (dry matter basis). Nutrient composition of the diets (% of dry matter) was 16.5% crude protein, 28.9% neutral detergent fiber, and 25.4% starch. Three orthogonal contrasts were used to compare treatments: effect of kernel processing (PT6 vs. SP6) and effect of TLOC (particle size; SP6 vs. SP12 and SP12 vs. SP18). Cows fed SP6 produced 1.2 kg/d greater milk yield with no changes in dry matter intake, resulting in greater feed efficiency compared with PT6. Cows fed SP6 also produced more milk protein (+36 g/d), lactose (+61 g/d), and total solids (+94 g/d) than cows fed PT6. The mechanism for increased yield of milk and milk components involved greater kernel fragmentation, starch digestibility, and glucose availability for lactose synthesis by the mammary gland. However, cows fed SP6 had lower chewing time and tended to have greater levels of serum amyloid A compared with PT6. Milk yield was similar for SP6 and SP12, but SP12 cows tended to have less serum amyloid A with greater chewing time. Cows fed SP18 had lower total-tract starch digestibility and tended to have lower plasma glucose and produce less milk compared with cows fed SP12. Compared with PT6, feeding SP6 raised linear odd-chain FA concentration in milk. Similarly, a reduction of these same FA occurred for SP12 compared with SP6. Cows fed SP6 had greater proportion of milk C14:1 and C16:1 compared with PT6 and SP12. Lesser trans C18:1 followed by greater C18:0 concentrations were observed for SP12 and PT6 compared with SP6, which is an indication of more complete biohydrogenation in the rumen. Under the conditions of this study, the use of a self-propelled forage harvester with kernel processing set for a 12-mm TLOC is recommended for WPCS from hybrids with vitreous endosperm.

Effects of addition of different sources and doses of sugars on in vitro digestibilities of dry matter, fibre and cell wall monosaccharides of corn silage in ruminants.

In ruminant diets, soluble sugar is an important factor in the digestive process. The objective of this study was to evaluate the effects of the source and dose of soluble sugars, under controlled pH conditions, on the in vitro digestibility of DM, fibre fractions (NDF and ADF) and cell wall neutral monosaccharides of corn silage. Silage was collected from several points in a silage mass from a bunker silo, oven-dried at 55°C and ground through a 1-mm screen. Sub-samples were combined with sugars to compose the treatments, in a 5 × 5 factorial arrangement, as a combination of five soluble sugar sources (glucose, fructose, arabinose, xylose and sucrose) and five sugar doses (0, 100, 200, 300 and 400 g/kg sugar in DM corn silage), respecting the following proportions of sugar : corn silage, 0 : 100, 10 : 90, 20 : 80, 30 : 70, 40 : 60 represented by the sugar doses, respectively. An in vitro test was performed to determine the true digestibility (D) of the chemical entities (DM, NDF and ADF) and cell wall monosaccharides (glucose = gluc, arabinose = arab and xylose = xyl). During the first 12 h of incubation, the pH was maintained above 6.0 by the addition of 2.5 N NaOH. The concentrations of neutral monosaccharides (arabinose, xylose and glucose) were determined by GLC. The soluble sugars decreased the digestibility of corn silage followed by pH reduction, especially at doses higher than 200 g/kg sugar. Overall, xylose, followed by sucrose, fructose and arabinose, had greater impacts on DM digestibility, whereas fibre digestibility was impaired by sucrose at all doses. Xylose and fructose had greater impacts on NDF digestibility at 300 and 400 g/kg sugar. Although xylose impaired the Dgluc in the cell wall in all doses. All doses of glucose improved the Dgluc and Dxyl in the cell wall.

The effect of length of storage and sodium benzoate on the nutritive value of reconstituted sorghum grain silages for dairy cows.

Twenty Holstein cows at 168 ± 87 d in milk (mean ± SD) were assigned to a 4 × 4 Latin square design with a 2 × 2 factorial arrangement to evaluate the effects of 2 storage lengths (30 or 90 d) and the presence of sodium benzoate (control or 0.2% as fed) on the nutritive value of reconstituted sorghum grain silages (RSGS). For each treatment, dry ground sorghum grain was rehydrated to 35% moisture and ensiled in 200-L plastic drums. The treatments were RSGS stored for 30 d without sodium benzoate (30 CON), RSGS stored for 30 d with sodium benzoate (30 BEN), RSGS stored for 90 d without sodium benzoate (90 CON) and RSGS stored for 90 d with sodium benzoate (90 BEN). Diets contained 16.3% RSGS. Silages stored for 90 d had higher concentrations of 1,2-propanediol, soluble protein, and ammonia nitrogen than did those stored for 30 d. Sodium benzoate reduced ethanol and ethyl-ester formation. Silages stored for 90 d had higher starch (89.3 vs. 86.9%) and protein (57.1 vs. 54.0%) digestibility compared with silages stored for 30 d. The ruminal acetate-to-propionate ratio tended to be lower in RSGS stored for 90 d than in RSGS stored for 30 d (3.75 vs. 3.34). Milk yield increased from 30.0 kg/d in cows fed RSGS stored for 30 d to 31.2 kg/d in cows fed RSGS stored for 90 d, without a change in dry matter intake (23.5 kg/d on average). Hence, feed efficiency and milk N efficiency also had tendencies to increase in cows fed RSGS stored for 90 d. Sodium benzoate did not alter cow performance but slightly increased plasma glucose (65.2 vs. 63.6 mg/dL). In conclusion, increasing the storage period of RSGS from 30 to 90 d improved starch and protein digestibility, milk yield, and feed efficiency.

Silage review: Unique challenges of silages made in hot and cold regions.

Silage making can be conveniently divided into field, ensiling, storage, and feed-out phases. In all of these stages, controllable and uncontrollable components can affect silage quality. For instance, silages produced in hot or cold regions are strongly influenced by uncontrollable climate-related factors. In hot regions, crops for silage are influenced by (1) high temperatures negatively affecting corn yield (whole-crop and grain) and nutritive value, (2) butyric and alcoholic fermentations in warm-season grasses (Panicum, Brachiaria, and Pennisetum genera) and sugarcane, respectively, and (3) accelerated aerobic deterioration of silages. Ensiling expertise and economic factors that limit mechanization also impair silage production and utilization in hot environments. In cold regions, a short and cool growing season often limits the use of crops sensitive to cool temperature, such as corn. The fermentation triggered by epiphytic and inoculated microorganisms can also be functionally impaired at lower temperature. Although the use of silage inoculants has increased in Northern Europe, acid-based additives are still a good option in difficult weather conditions to ensure good fermentation quality, nutritive value, and high intake potential of silages. Acid-based additives have enhanced the quality of round bale silage, which has become a common method of forage preservation in Northern Europe. Although all abiotic factors can affect silage quality, the ambient temperature is a factor that influences all stages of silage making from production in the field to utilization at the feed bunk. This review identifies challenges and obstacles to producing silages under hot and cold conditions and discusses strategies for addressing these challenges.

Short communication: Influence of various proteolytic sources during fermentation of reconstituted corn grain silages.

The objective of this study was to determine the contribution of corn kernel enzymes, bacteria, fungi, and fermentation end-products (main acids and ethanol) to protein solubilization during fermentation of reconstituted corn grain silage. Flint corn kernels were ground (5-mm sieve), rehydrated to 32% of moisture, and treated with no additives (control), gamma irradiation (32 kGy), gamma irradiation + fermentation end-products (1% of lactic acid, 0.3% of acetic acid, and 0.7% of ethanol, as fed), and natamycin (1% as fed). Treated grains were ensiled in nylon-polyethylene bags and stored for 90 d. Protein solubilization was calculated for each treatment and the contributions of proteolytic sources were determined. Bacterial activity was the main contributor to proteolysis (60%) followed by corn kernel enzymes (30%), whereas fungi and fermentation end-products had only minor contributions (∼5% each).

Effects of maturity at ensiling of bermudagrass and fibrolytic enzyme application on the performance of early-lactation dairy cows.

The objective of this study was to examine effects of adding fibrolytic enzymes to diets containing bermudagrass ensiled after 4 or 7wk of regrowth on the diet digestibility, ruminal fermentation and performance of lactating cows, and the interaction of the treatments. In experiment 1, 64 Holstein cows (22±4d in milk) were assigned to an experiment with a 2×2 factorial treatment arrangement and a 56-d duration. Treatments were diets containing 4 or 7wk regrowth bermudagrass silage without or with an exogenous fibrolytic enzyme cocktail. The cellulase-xylanase enzyme was applied at 2.33g/kg of total mixed ration dry matter (DM) during mixing immediately before feeding. Experiment 2 was aimed at examining treatment effects on the ruminal fermentation profile. Four ruminally cannulated cows were assigned to the 4 treatments using a 4×4 Latin square design with 14-d periods. No enzyme by maturity interaction was detected for any measurement. Regardless of forage maturity, applying the fibrolytic enzyme did not affect DM intake, milk yield, apparent digestibility, feed efficiency, energy balance, and ruminal fermentation though it tended to increase milk lactose concentration (4.88 vs. 4.81%). Feeding the 4-wk diet instead of the 7-wk diet increased DM intake (22.4 vs. 21.3kg/d), digestibility of DM, neutral detergent fiber, and acid detergent fiber, and tended to increase 3.5%-fat corrected milk yield (47.2 vs. 44.3kg/d) and milk fat yield (1.88 vs. 1.73kg/d). Therefore, daily intake of net energy and secretion of milk energy were greater for the 4-wk diet. In addition, the 4-wk diet increased the ruminal concentrations of acetate, propionate, valerate, lactate, and total volatile fatty acids, and decreased ruminal pH, without affecting the acetate:propionate ratio. Feeding fibrolytic enzymes did not improve the performance of early-lactation dairy cows, but harvesting the forage earlier tended to improve milk production.

Exchanging physically effective neutral detergent fiber does not affect chewing activity and performance of late-lactation dairy cows fed corn and sugarcane silages.

The objective of this study was to determine whether replacing the physically effective neutral detergent fiber (peNDF) of corn silage with sugarcane silage peNDF would affect performance in dairy cows. Twenty-four late-lactation Holstein cows were assigned to eight 3 × 3 Latin squares with 21-d periods. The dietary treatments were (1) 25% peNDF of corn silage, (2) 25% peNDF of sugarcane silage, and (3) 12.5% peNDF of corn silage + 12.5% peNDF of sugarcane silage. The physical effectiveness factors (pef) were assumed to be 1 for corn silage and 1.2 for sugarcane silage, as measured previously by bioassay. Thus, peNDF was calculated as neutral detergent fiber (NDF) × pef. The concentrate ingredients were finely ground corn, soybean meal, pelleted citrus pulp, and mineral-vitamin premix. Dry matter intake (22.5 ± 0.63 kg/d), 3.5% fat-corrected milk yield (28.8 ± 1.13 kg/d), milk composition (fat, protein, lactose, urea, casein, free fatty acids, and somatic cell count), and blood metabolites (glucose, insulin, and nonesterified fatty acids) were unaffected by the treatments. The time spent eating, ruminating, or chewing was also similar among the diets, as was particle-sorting behavior. By contrast, chewing per kilogram of forage NDF intake was higher for the sugarcane silage (137 min/kg) than the corn silage diet (116 min/kg), indicating the greater physical effectiveness of sugarcane fiber. Based on chewing behavior (min/d), the estimated pef of sugarcane silage NDF were 1.28 in the corn silage plus sugarcane silage diet and 1.29 in the sugarcane silage diet. Formulating dairy rations of equal peNDF content allows similar performance if corn and sugarcane silages are exchanged.

Short-term effects of silage volatile compounds on feed intake and digestion in beef cattle.

Two experiments were conducted to evaluate whether fermentation end products in silage affect intake and digestion in beef cattle. Six rumen-cannulated Nellore steers were randomly assigned to a replicated 3 × 3 Latin square design with 14-d periods. Each period consisted of 9 d for adaptation and 5 d for sample collection. Steers were housed in a tie-stall barn and individually fed once daily at 0800 h. The dietary treatments in Exp. 1 were as follows: 60% corn silage plus 40% concentrate (CON), 60% corn silage with added ethanol (2.8% on a DM basis) and 40% concentrate (ET), and 60% corn silage with added lactic acid (5.4% on a DM basis) and 40% concentrate (LA). The DMI was similar (P = 0.41) across treatments (average 11.7 kg/d); however, the LA treatment increased the ruminal pH (P = 0.01) and decreased the acetate:propionate ratio (P < 0.01). Diet digestibility decreased by 2.2 to 2.5 percentage units when the DM content was determined by oven drying (at 105°C) rather than by toluene distillation. The treatments in Exp. 2 were as follows: 75% sugarcane silage with no volatile fraction (oven dried at 60°C and rehydrated) and 25% concentrate (75D), 75% sugarcane silage (original moisture content) and 25% concentrate (75W), and 40% sugarcane silage and 60% concentrate (40W). Approximately 21% of the DM content of sugarcane silage consisted of volatile compounds. The presence of these compounds did not alter the DMI (P = 0.36) but did increase both the acetate:propionate ratio (P < 0.01) and the fractional absorption rates of valerate (P < 0.01) and ethanol (P = 0.02) in the empty reticulorumen. The 40W diet led to a greater DMI (40W = 9.79 vs. 75W = 6.19 kg/d; P < 0.01), which altered most of the measured variables traditionally associated with high-concentrate diets. As in Exp. 1, diet digestibility decreased by 1.5 to 5.4 units when the DM content was determined by oven drying at 105°C rather than by toluene distillation. In this short-term study, volatile compounds did not inhibit the DMI or the digestion process of the animals. On the contrary, volatile compounds contributed to the energy content of the silage, composing up to 10% of the energy value as determined by digestibility. Due to the short experimental periods, the results from this study should be interpreted with caution.

Performance of dairy cows fed high levels of acetic acid or ethanol.

Ethanol and acetic acid are common end products from silages. The main objective of this study was to determine whether high concentrations of ethanol or acetic acid in total mixed ration would affect performance in dairy cows. Thirty mid-lactation Holstein cows were grouped in 10 blocks and fed one of the following diets for 7 wk: (1) control (33% Bermuda hay + 67% concentrates), (2) ethanol [control diet + 5% ethanol, dry matter (DM) basis], or (3) acetic acid (control diet + 5% acetic acid, DM basis). Ethanol and acetic acid were diluted in water (1:2) and sprayed onto total mixed rations twice daily before feeding. An equal amount of water was mixed with the control ration. To adapt animals to these treatments, cows were fed only half of the treatment dose during the first week of study. Cows fed ethanol yielded more milk (37.9 kg/d) than those fed the control (35.8 kg/d) or acetic acid (35.3 kg/d) diets, mainly due to the higher DM intake (DMI; 23.7, 22.2, and 21.6 kg/d, respectively). The significant diet × week interaction for DMI, mainly during wk 2 and 3 (when acetic acid reached the full dose), was related to the decrease in DMI observed for the acetic acid treatment. There was a diet × week interaction in excretion of milk energy per DMI during wk 2 and 3, due to cows fed acetic acid sustained milk yield despite lower DMI. Energy efficiency was similar across diets. Blood metabolites (glucose, insulin, nonesterified fatty acids, ethanol, and γ-glutamyl transferase activity) and sensory characteristics of milk were not affected by these treatments. Animal performance suggested similar energy value for the diet containing ethanol compared with other diets. Rumen conversion of ethanol to acetate and a concomitant increase in methane production might be a plausible explanation for the deviation of the predicted energy value based on the heat of combustion. Therefore, the loss of volatile compounds during the drying process in the laboratory should be considered when calculating energy content of fermented feedstuffs.

Short communication: An evaluation of the effectiveness of Lactobacillus buchneri 40788 to alter fermentation and improve the aerobic stability of corn silage in farm silos.

The objective of this study was to determine if the effects of inoculation with Lactobacillus buchneri 40788 were detectable when applied to whole-plant corn stored in farm silos. Corn silage was randomly sampled from farms in Wisconsin, Minnesota, and Pennsylvania, and was untreated (n = 15) or treated with an inoculant (n = 16) containing L. buchneri 40788 alone or this organism combined with Pediococcus pentosaceus during May and June 2007. Corn silage that was removed from the silo face during the morning feeding was sampled, vacuum-packed, and heat sealed in polyethylene bags and shipped immediately to the University of Delaware for analyses. Silage samples were analyzed for dry matter (DM), nutrient composition, fermentation end-products, aerobic stability, and microbial populations. The population of L. buchneri in silages was determined using a real-time quantitative PCR method. Aerobic stability was measured as the time after exposure to air that it took for a 2 degrees C increase above an ambient temperature. The DM and concentrations of lactic and acetic acids were 35.6 and 34.5, 4.17 and 4.85, and 2.24 and 2.41%, respectively, for untreated and inoculated silages and were not different between treatments. The concentration of 1,2-propanediol was greater in inoculated silages (1.26 vs. 0.29%). Numbers of lactic acid bacteria determined on selective agar were not different between treatments. However, the numbers of L. buchneri based on measurements using real-time quantitative PCR analysis were greater and averaged 6.46 log cfu-equivalents/g compared with 4.89 log cfu-equivalent for inoculated silages. There were fewer yeasts and aerobic stability was greater in inoculated silages (4.75 log cfu/g and 74 h of stability) than in untreated silages (5.55 log cfu/g and 46 h of stability). This study supports the effectiveness of L. buchneri 40788 on dairy farms.

Desempenho, parâmetros da carcaça e comportamento ingestivo de cordeiros alimentados com cana-de-açúcar ensilada ou in natura / Performance, carcass characteristics and ingestive behavior of feedlot lambs fed fresh or ensiled sugar cane

Trinta cordeiros da raça Santa Inês, 26,2±0,6kg e 151±1,7 dias de idade, foram confinados para avaliar os efeitos da utilização de silagens de cana-de-açúcar sobre o desempenho, as características da carcaça e o comportamento ingestivo. As rações experimentais foram compostas de 50 por cento de volumoso e 50 por cento de concentrado, diferindo quanto ao tipo do volumoso utilizado: cana-de-açúcar in natura, silagem de cana-de-açúcar sem aditivo e silagem de cana-de-açúcar aditivada com Lactobacillus buchneri (5x10(4) UFC/g de MV). Não houve diferença (P>0,05) para o consumo de MS, ganho de peso vivo, conversão alimentar e parâmetros de carcaça entre os tratamentos. O tempo de ingestão (min/g FDN) e a eficiência de ruminação (g MS/h) foram menores (P<0,05) para os tratamentos contendo silagem de cana-de-açúcar. Silagens de cana-de-açúcar não alteraram o desempenho e as características da carcaça dos cordeiros em relação à cana de açúcar in natura. A utilização do aditivo microbiano contendo o L. buchneri na ensilagem da cana-de-açúcar não alterou as variáveis avaliadas.

Thirty Santa Ines ram lambs, 26.2±0.6kg and 151±1.7 day-old, were penned to evaluate the effects of feeding sugar cane silages on performance, carcass characteristics and ingestive behavior. Lambs were fed a 50:50 (concentrate:roughage ratio) TMR. Experimental treatments were: fresh sugar cane, sugar cane silage without additive and sugar cane silage treated with Lactobacillus buchneri (5x10(4) cfu/g wet basis). No differences (P>0.05) on dry matter intake, average daily gain, feed conversion and carcass characteristics were observed among treatments. Eating time (min/g NDF) and rumination efficiency (g DM/h) were lower (P<0.05) for silage diets. Sugar cane silage had no detrimental effect on lamb performance and carcass characteristics compared to fresh sugar cane. Adding L. buchneri to sugar cane silage did not change the evaluated characteristics.

Effects of grain processing and bovine somatotropin on metabolism and ovarian activity of dairy cows during early lactation.

This study compared the effects of exogenous bovine somatotropin (bST) on the metabolism and ovarian activity of cows fed diets differing in ruminally degradable starch. Twenty-four multiparous and eight primiparous Holstein cows in early lactation were divided into four groups and fed diets containing 39% grain as steam-flaked sorghum or steam-rolled corn with or without bST for 90 d in a 2 x 2 factorial design. Flaked sorghum improved energy status of cows during early lactation, tending to increase plasma glucose and insulin. Administration of bST decreased plasma urea nitrogen and increased nonesterified fatty acids (NEFA). Plasma levels of beta-hydroxybutyrate (BHBA) and hepatic concentrations of triglycerides were not altered by treatments. Temporal changes in plasma glucose, urea nitrogen, NEFA, and BHBA were detected in a quadratic manner and insulin increased linearly with time, but treatments did not affect postpartum changes in these metabolites. There were greater decreases in body weight and net energy balance in cows on bST during the first 7 wk of treatment. Cows receiving bST took longer to reach the nadir of negative energy balance, and bST tended to delay the period to reach a positive energy balance. Follicular populations and incidence of cystic ovaries were not affected by treatments, but cows receiving bST had fewer double ovulations. Flaked sorghum increased plasma progesterone during the early luteal phase of the first two postpartum estrous cycles. Feeding more ruminally degradable starch improved the energy status and luteal activity of cows in early lactation.

Effects of bovine somatotropin on milk yield and composition in Holstein cows in advanced lactation fed low- or high-energy diets.

The objective of this study was to evaluate the response of Holstein cows to bovine somatotropin (bST) during advanced lactation and its relationship to energy intake. Twenty-four lactating Holstein cows averaging 21 kg of milk/d, and 292 d in milk were assigned to one of three treatment groups in a randomized block design. Blocks were based on the 14 d of pretreatment milk production, and treatment groups were balanced for days in milk. Treatment 1 was a low-energy diet (1.49 Mcal/kg of dry matter) without bST injection; treatment 2 was the low-energy diet plus injection of 500 mg of bST every 14 d; and treatment 3 was a high-energy diet (1.71 Mcal/kg of dry matter) with bST injections as in treatment 2. Treatment was divided into two periods (1 to 49 and 50 to 98 d) to determine if response to bST and energy changed with time on treatment. Results showed that bST significantly (P < 0.05) increased milk, fat-corrected milk, and fat and protein yields; and feed efficiency (fat-corrected milk per dry matter intake) for both periods. Milk yield responses to bST were greater for cows fed the low-than the high-energy diet in both periods. These data show that bST injections for cows in advanced lactation increased performance, but excessive energy diminished the bST response.

Response of lactating dairy cows to steam-flaked sorghum, steam-flaked corn, or steam-rolled corn and protein sources of differing degradability.

Protein sources with different degradabilities were fed to 48 lactating Holstein cows receiving 37 or 39% of dietary dry matter as steam-flaked sorghum (360 g/L), steam-flaked corn (360 g/L), or steam-rolled corn (490 g/L) in a 3 x 2 factorial arrangement of treatments. Cows were fed an alfalfa-based diet with 7% soybean meal or 5% of an animal-marine protein blend and 37 or 39% grain. Although not significant, cows fed flaked grain yielded a mean of 1.5 kg/d more milk than did those fed rolled grain. Gross feed efficiency was not affected by grain processing or protein source, but diets with the animal-marine protein blend had 9% higher estimated net energy for lactation than did diets with soybean meal. The greater gains in body weight and increased digestibility of the diets with the animal-marine protein blend verify the higher energy concentration of those diets. Yield of milk protein was increased by flaked grain or the animal-marine protein blend, and flaked grain increased percentages of lactose and solids nonfat. Increasing the ratio of rumen-degradable starch to rumen-degradable protein increased milk protein content and yield linearly and increased contents of lactose and solids nonfat. A linear response of dry matter, organic matter, crude protein, and starch digestibilities was observed as the ratio of rumen-degradable starch to rumen-degradable protein increased. These data show improved performance of dairy cows fed a high rumen-undegradable protein source with diets high in rumen-degradable starch from steam-processed grains.

Performance and nutrient digestibility by dairy cows treated with bovine somatotropin and fed diets with steam-flaked sorghum or steam-rolled corn during early lactation.

This study compared effects of exogenous bovine somatotropin (bST) on the performance of early lactation cows fed diets differing in ruminally degradable starch. Thirty-two Holstein cows (24 multiparous) in early lactation (5 d in milk) were divided into four groups and fed diets containing 39% grain as steam-flaked sorghum or steam-rolled corn with or without exogenous bST for 90 d. Grain processing did not affect dry matter intake as a percentage of body weight or yields of milk, but steam-rolled corn improved efficiency of feed utilization during the first 45 d of the study. Cows receiving bST had lower dry matter intake during the first 45 d of treatment. Milk yield and efficiency of feed utilization were increased by bST treatment, and milk yield response was greater during the first half than during the second half of the study. Milk composition and yield of milk components did not differ among treatments. Flaked sorghum increased in vitro starch hydrolysis and digestibilities of dry matter, organic matter, and starch, but neither method of grain processing nor bST affected digestibilities of crude protein, acid detergent fiber, or neutral detergent fiber. Grain type did not affect milk yield, and responses to bST were lower from 7 to 13 wk than from 1 to 6 wk prepartum.

Effect of steam-flaked or steam-rolled corn with or without Aspergillus oryzae in the diet on performance of dairy cows fed during hot weather.

The objective of this study was to determine the effects of steam-rolled versus steam-flaked corn in the diet with or without the addition of a culture of Aspergillus oryzae on the performance of high producing dairy cows during hot summer weather. Thirty-two Holstein cows averaging 92 (+/- 60) d in milk were fed a pretreatment diet for 21 d followed by a 70-d experimental period in a completely randomized block design with a 2 x 2 factorial arrangement of treatments. Diets were 1) steam-flaked corn plus 3 g/d of A. oryzae, 2) steam-flaked corn, 3) steam-rolled corn plus 3 g/d of A. oryzae, and 4) steam-rolled corn. Intake was not affected significantly by grain processing or addition of A. oryzae. Compared with effects from steam-rolled corn in the diet, steam-flaked corn increased milk production; percentage of milk protein; yields of milk protein, lactose, and SNF; and the efficiency of conversion of dry matter to fat-corrected milk. Addition of A. oryzae tended to increase protein percentage and increased the percentage of SNF. Changes in body weight and body condition score tended to be higher, and somatic cell count tended to be lower, for cows fed the flaked corn than for cows fed the rolled corn. No interactions were significant. Treatments did not affect rectal temperatures or respiration rates; however, high mean values measured at 1400 h once weekly indicated thermal stress. These data show improved milk production from cows fed steam-flaked corn but not from those fed diets supplemented with A. oryzae.