A 100-Year Review: Metabolic modifiers in dairy cattle nutrition.

The first issue of the Journal of Dairy Science in 1917 opened with the text of the speech by Raymond A. Pearson, president of the Iowa State College of Agriculture, at the dedication of the new dairy building at the University of Nebraska (J. Dairy Sci. 1:4-18, 1917). Fittingly, this was the birth of a new research facility and more importantly, the beginning of a new journal devoted to the sciences of milk production and manufacture of products from milk. Metabolic modifiers of dairy cow metabolism enhance, change, or interfere with normal metabolic processes in the ruminant digestive tract or alter postabsorption partitioning of nutrients among body tissues. Papers on metabolic modifiers became more frequent in the journal around 1950. Dairy farming changed radically between 1955 and 1965. Changes in housing and feeding moved more cows outside, and cows and heifers in all stages of lactation, including the dry period, were fed as a single group. Rations became wetter with the shift to corn silage as the major forage in many rations. Liberal grain feeding met the requirements of high-producing cows and increased production per cow but introduced new challenges; for example, managing and feeding cows as a group. These changes led to the introduction of new strategies that identified and expanded the use of metabolic modifiers. Research was directed at characterizing the new problems for the dairy cow created by group feeding. Metabolic modifiers went beyond feeding the cow and included environmental and housing factors and additives to reduce the incidence and severity of many new conditions and pathologies. New collaborations began among dairy cattle specialties that broadened our understanding of the workings of the cow. The Journal of Dairy Science then and now plays an enormously important role in dissemination of the findings of dairy scientists worldwide that address existing and new technologies.

Monensin by fat interactions on trans fatty acids in cultures of mixed ruminal microorganisms grown in continuous fermentors fed corn or barley.

In previous studies, monensin (M) and unsaturated plant oils independently increased trans fatty acid concentrations in cultures of mixed ruminal microorganisms. This study was conducted to determine if combining M with plant oil yielded interactions on trans fatty acid concentrations in cultures of mixed ruminal microorganisms or their effects were additive. Four continuous fermentors were fed 14 g of dry feed per day (divided equally between two feedings), consisting of alfalfa hay pellets (30% of DM) and either a high corn (HC) or a high barley (BB) concentrate (70% of DM) in each of two fermentors. Within each grain type, one fermentor was supplemented with M (25 ppm), and the other fermentor was supplemented with 5% soybean oil (SBO) during d 5 to 8. Monensin and SBO were added together in all fermentors during d 9 to 12. Samples were taken at 2 h after the morning feeding on the last day of each period and analyzed for fatty acids by gas-liquid chromatography. A second run of the fermentors followed the same treatment sequence to give additional replication. Average pH across all treatments was 6.15, which was reduced by M but not affected by SBO. Monensin reduced the ratio of acetate to propionate (A:P), which averaged 2.03 across all treatments; fat decreased A:P in cultures not receiving M but increased it in the presence of M. Monensin and SBO altered the concentration of several trans fatty acids, but the only interaction was a grain x M x SBO interaction for trans-10 C18:1. The increase in trans-10 C18:1 by the M and SBO combination exceeded the sum of increases in trans-10 C18:1 for each individual feed additive, but only for KB. For the HC diet, M increased trans-10 C18:1 more than fat alone and more than the M and SBO combination. The results of this study show that M and SBO effects are additive for all trans FA except for trans-10 C18:1. In the case of trans-10 C18:1, M and SBO interacted to give higher trans-10 C18:1 concentrations in ruminal contents than would be expected simply by adding their individual effects, but only for HB. Because some trans fatty acid isomers have been associated with milk fat depression in dairy cows, these results suggest more severe depressions in milk fat content when cows are fed M along with unsaturated plant oils.

Lactation response and body composition of cows receiving somatotropin and three ratios of forage to concentrate.

Ninety multiparous Holstein cows were used to determine the effect of ration energy density and bST on lactation performance and whole body chemical composition. Seventy-eight cows, averaging 43.6 d postpartum, were assigned for 168 d to TMR with forage: concentrate ratios of 40:60, 50:50, and 60:40 (DM basis). Half of the cows on each ration received subcutaneously either 0 or 640 mg bST/28 d. Whole body chemical composition was determined by comparative slaughter in 12 cows (means = 35.9 d postpartum) prior to initiation of treatment and in 35 cows after either 84 or 168 d of treatment. Net energy intake was greater for 40:60 and 50:50 than for 60:40. Milk fat percentage was reduced in cows fed 40:60. Ration did not affect milk, 3.5% FCM, and DMI. There were no differences among rations for total body fat, protein, water, and calories. The bST increased milk and 3.5% FCM but had no effect on DM and net energy intakes. Yield of 3.5% FCM by cows receiving bST and fed 40:60 was 1.9 kg/d more and for 50:50 it was 2.7 kg/d more than for those fed 60:40. Administration of bST reduced total body fat and calories but did not affect protein and water. Partitioning of calories to milk at the expense of fat deposition is the primary mechanism for the galactopoietic action of bST.

Effect of somidobove sustained release administration on the lactation performance of dairy cows.

Lactation performance was determined on 190 multiparous Holsteins from five herds supplemented with 0, 320, 640, or 960 mg of somidobove every 28 d. The experiment consisted of 21 d of pretreatment and treatment periods of various lengths, depending upon stage of lactation of animals at first administration. Somidobove beginning in early (28 to 45 d in milk), mid (111 to 166 d in milk), or late (166 to 334 d in milk) stages of lactation consisted of 9, 6, or 3 administrations. Milk and 3.5% FCM yields were increased by each dose of somidobove in all stages. Milk composition and dry matter and energy intakes were similar among treatments within stage. Milk to DMI ratio and milk energy to net energy intake ratio were improved by somidobove. Gain was positive for all treatments, but less in somidobove-supplemented cows. Lower body weight and condition score at the completion of somidobove treatment resulted. For early cows, days to first estrus and days to first breeding were similar; however, total number of inseminations for cows receiving somidobove was twofold greater than control, resulting in a longer calving interval. Results demonstrated efficacy of somidobove administered every 28 d to lactating dairy cattle for increased milk yield.

Nutritional implications of bovine somatotropin for the lactating dairy cow.

Historians of animal production will remember the 1980s in part for the application of recombinant DNA technology, which permits large-scale production of an almost infinite number of proteins. Bovine somatotropin represents the first such protein for animal agriculture. Since its introduction in 1981, extensive research demonstrated the galactopoietic actions in dairy cattle under diverse feeding, management, and environmental conditions. Milk production increases from cows receiving bST range from 0 to 11 kg/d. Magnitude of improvement is related to factors associated with rations, animals, and environment. Quantity, quality, and density of nutrients, especially energy and protein, are ration determinants for efficacy of bST. Factors such as parity, nutritional history, body condition, and stage of lactation also influence the response. High temperature or humidity, which affects feed intake, appears to reduce the magnitude of response to somatotropin. Relationships among factors affecting galactopoiesis by somatotropin are discussed. Recent studies describing body composition changes provide insight into the mechanism of action of bST in lactating cows. Nutritional guidelines for use in the lactating cow must emphasize current concepts for high production. Management of the cow when she is not receiving bST (dry period, early lactation) will be as critical for success as during bST administration.

Lactation response of dairy cows receiving bovine somatotropin and fed rations varying in crude protein and undegradable intake protein.

Our experiment evaluated lactation and metabolic responses of Holstein cows injected with somidobove (recombinant bST) and fed one of four isocaloric rations containing either 14 (low) or 17% (high) CP and undegradable intake protein of 33 (low) or 40% (high) of CP. Multiparous cows (n = 37) in early lactation, averaging 37 kg/d of milk, received somidobove (640 mg per injection) at 28-d intervals for 112 d and one of four protein rations: low-low, low-high, high-low, and high-high. Nine other multiparous controls were fed low-low ration with no somidobove. On the low-low ration, somidobove significantly increased milk yield by 2.3 kg/d, but not 3.5% FCM (1.7 kg/d), intakes of DM or CP, or milk composition. Milk and 3.5% FCM increased by 1.7 and 2.1 kg/d in cows fed high undegradable intake protein but there was no effect on milk composition, BW, or DM intake. Ration CP had no effect on production variables in cows receiving somidobove. Serum urea was higher in cows fed high CP rations; undegradable intake protein was without effect. Plasma leucine was higher in cows fed high undegradable intake protein. Administration of somidobove to cows fed low-low rations reduced plasma methionine, serum albumin, hemoglobin, and albumin:globulin ratio. Milk production of high producing dairy cows receiving somidobove may be limited by the amount of protein available at the small intestine.

Lactation response of dairy cows receiving bovine somatotropin via daily injections or in a sustained-release vehicle.

Three experiments were conducted to characterize metabolic and milk production responses of dairy cows receiving recombinantly derived bovine somatotropin administered either by daily injection or in a sustained-release vehicle. In Experiment 1, somatotropin (25 mg/d) purified by two methods was given by daily injection for 14 d and resulted in 3.5 and 3.8 kg/d more milk than controls. Percentages of fat and total solids in milk were also increased by somatotropin. Eleven hematology indices and 12 metabolites, minerals, and enzyme activities in serum were unaffected by somatotropin. In Experiments 2 and 3, somatotropin was administered in a sustained-release vehicle during an 84-d treatment period. In Experiment 2, administration of 960 mg of somatotropin at 28-d intervals increased milk and SCM yields by 4.1 and 3.3 kg/d compared with yields of controls. There were no significant differences in other production parameters. In Experiment 3, 320, 640, and 960 mg somatotropin were each administered in the sustained-release vehicle at intervals of 14, 21, and 28 d. An uninjected group served as control. Cows receiving somatotropin averaged 3.5 to 5.9 kg/d more milk than controls across all injection intervals. Among doses, milk yield was greater at 960 mg than at 320 or 640 mg. There were no significant differences in milk or SCM among injection groups. These experiments demonstrate the comparable efficacy of somatotropin when given by daily injections or in a sustained-release vehicle.

Feeding value of a high oil variety of sunflowers as silage to lactating dairy cows.

Whole-plant sunflowers (oilseed) were chopped and stored as silage and compared to corn silage as the sole forage to 20 lactating Holsteins in a switch-back design of three 5-wk periods. Cows fed sunflower silage produced less milk (22.4 vs. 20.5 kg/day) but similar amounts of 4% fat-corrected milk. Cows fed sunflower silage had greater fat, less protein, and less total solids in milk. Cows consumed 4.0 kg/day less dry matter from sunflower silage than from corn silage. Oleic and linolenic increased, and myristic and palmitic fatty acids decreased in milk fat from cows fed sunflower silage. Cholesterol in serum (mg/dl) was 321 and 160 for cows fed sunflower silage and corn silage. Cows fed sunflower silage had higher molar percentage of acetate, isobutyrate, isovalerate, and a wider acetate propionate ratio with concomitant lower molar percentage of propionate, butyrate, valerate, and less total acids in rumen fluid than cows fed corn silage. Rumen fluid pH was 6.98 and 6.83 for cows fed sunflower silage and corn silage. Acceptable quality silage can be made from whole oilseed sunflowers. For maximum milk production, sunflower silage should not be fed as the only forage to dairy cows.