Effects of supplementation of dairy cattle with fish oil on silage intake, milk yield and milk composition

The effects of level of fish oil inclusion in the diet on grass silage intake, and milk yield and composition of dairy cows offered either 5 or 10 kg concentrates/d were evaluated in a ten treatment, partly balanced, changeover design experiment involving 50 cows in early lactation. Concentrates were prepared to provide 0, 150, 300 or 450 g fish oil/cow per d or 300 g fish oil/cow per d from a premix when each animal was offered 5 kg/d. The fish oil was predominantly from herring and mackerel caught in the North Atlantic while the fish oil premix was obtained from a commercial source and used palm kernel expeller as a carrier. Increasing fish oil supplementation decreased silage dry matter intake and the concentrations of milk fat and protein, and increased milk yield and diet digestibility. There were significant interactions between concentrate feed level and level of fish oil for silage intake and milk yield. Other than for the concentrations of milk fat and protein, and 20:4n-6 fatty acids, the source of fish oil did not affect forage intake or animal performance. Fish oil supplementation also decreased the concentrations of milk protein by 0.9 g/kg for each 100 g increase in fish oil supplementation, the depression being similar at each level of concentrate feeding. Supplementing the feed of dairy cows with 450 g fish oil/cow per d decreased the concentration of milk fat by 15 g/kg. This study also showed that feeding dairy cattle with fish oil is an efficient method of increasing eicosapentaenoic acid in the human diet through transfer into milk.     

Estimation of the proportion of feed protein digested in the small intestine of cattle consuming wet corn gluten feed

The objectives of this study were to expand the database and determine the intestinal digestibility of rumen undegradable protein (dRUP) of common dairy feeds and to determine the effects of feeding 37.9% wet corn gluten feed on these estimates. Two ruminally and duodenally fistulated steers were assigned randomly to a crossover design with 4-wk periods. The mobile bag technique was used to determine rumen undegradable protein (RUP), dRUP, total tract digestible protein, and total tract digestible dry matter of alfalfa hay, brome hay, alfalfa haylage, corn silage, whole cottonseed, soybean meal, soyhulls, ground corn, nonenzymatically browned soybean meal, and dried distillers grains. There was no consistent effect of diet on RUP, dRUP, total tract digestible protein, and total tract digestible dry matter. The RUP (% of crude protein) ranged from 5.97% for alfalfa haylage to 75.6% for nonenzymatically browned soybean meal. The dRUP ranged from 15.3% for alfalfa haylage to 96.5% for nonenzymatically browned soybean meal. The dRUP for alfalfa hay (33.9%), brome hay (39.1%), alfalfa haylage (15.5%), and corn silage (19.9%) were lower than National Research Council reported values. The higher dRUP of the nonenzymatically browned soybean meal is reflective of more total protein reaching the small intestine. The large range in dRUP was not reflected in total tract digestible protein (% of crude protein), with corn silage being the lowest at 85.2% and nonenzymatically browned soybean meal the highest at 97.9%. In this study, diet had little effect on intestinal digestibility of protein or dry matter.     

Addition of protected and unprotected fish oil to diets for dairy cows. I. Effects on the yield,composition and taste of milk

Thirty Holstein cows in mid-lactation (158+/-20 DIM) were given a total mixed ration based on grass silage, maize silage and rolled barley. After a preliminary period of 1 week, this diet was supplemented with nothing (control), unprotected fish oil (3.7% of dry matter, DM), or two levels of glutaraldehyde-protected microcapsules of fish oil (1.5% and 3.0% of DM, respectively). Unprotected and protected supplements contained, respectively, 74% and 58% of DM as lipids. Cows given the unprotected supplement reduced their feed intake by > 25%. Consequently, these cows lost body weight and produced less milk. DM intake, body weight, and milk yield were unaffected by protected fish oil. Fish oil reduced both milk fat and protein percentages, and decreased the proportion of short-chain fatty acids, stearic, and oleic acids in milk fat. Milk trans C18:1 fatty acids increased in cows given both unprotected and protected fish oil. Milk fat content of very-long-chain n3 polyunsaturated fatty acids, including C20:5 and C22:6, increased with fish oil in the diet. Accordingly, the peroxide index increased and a taste panel was able to detect unusual taste in milk from cows consuming the higher level of protected fish oil and disliked the milk from cows given unprotected fish oil. In conclusion, when lactating cows consumed fish oil, milk concentration of long-chain n3 fatty acids increased and mammary de novo synthesis of fatty acids decreased, but milk yield and milk protein content were reduced, and the milk was more susceptible to oxidation and its taste was adversely affected.     

Rumen volatile fatty acids and milk composition from cows fed hay, haylage, or urea-treated corn silage.

Alfalfa-brome hay, haylage, .5% urea-treated corn silage, or .5% urea plus 1% dried whey-treated corn silage was fed as the only forage to one of four groups of 10 lactating cows per group for a lactation trial of 10 wk. Rumen samples were collected via stomach tube 3 to 4 h after the morning feeding. The pH of the rumen samples from cows fed hay was higher than for cows fed haylage, urea-treated corn silage, and urea-whey corn silage, 6.69 versus 6.36, 6.40, and 6.50. Total volatile fatty acids and propionate were highest from cows fed urea-whey corn silage and were higher on all three fermented forages than cows fed hay. Acetate/propionate ratio was highest from cows fed hay and lowest from cows fed corn silages. Butyrate was highest from cows fed haylage or hay. Milk protein composition was not affected by ration although nonprotein nitrogen of milk was highest from cows fed the urea-treated corn silages. Oleic acid and total unsaturated fatty acids were lowest in milk fat from cows fed hay while palmitic acid was highest from cows fed hay and haylage. These results suggest that type of forage fed may cause small changes in rumen fermentation and in milk composition. The importance of these changes is unknown but may affect properties of dairy products produced from this milk.     

Evaluation of whisky distillery by-products III.—Effect of calcium supplements on the digestibility and intake of ruminant diets containing malt distiller's grains

Digestibility and intake data have been obtained from sheep fed on rations consisting of fresh and ensiled malt distiller's grains (MDG) fed alone and with hay and silage. The effects of calcium supplements have been measured with all rations, and calcium lactate has been compared with calcium carbonate. The results of digestibility trials with cattle have been included; in these the effect of additional calcium has been estimated with rations of barley straw + MDG. When MDG was fed alone the intakes of fresh and ensiled forms were similar and there was a significant decrease in intake with duration of feeding. Fresh MDG had a significantly higher digestibility, and additional calcium increased the digestibilities of fresh and ensiled samples. The intakes of rations containing hay + MDG and silage + MDG were positively correlated with digestibilities of the whole ration. Additional calcium resulted in higher intakes of hay and MDG but silage intakes were unaffected. The effect of added calcium was greater with hay + fresh MDG than with other combinations of constituents. Calcium carbonate and calcium lactate were equally effective in increasing intake. The addition of NaCl during the ensilage of MDG reduced the retention of magnesium by sheep given grains with hay and silage. Addition of calcium to cattle rations of barley straw and MDG produced an increase in the intake but digestibility of the diet was not affected. The rations with calcium provided 0·75 × maintenance requirements of the cattle for metabolisable energy and about twice the maintenance requirements for digestible crude protein.     

Blood amino acids and milk composition from cows fed soybean meal, fish meal, or both

Twelve multiparous Holstein cows at 48 +/- 8 d in milk were used in a 4 x 4 Latin square with 21-d periods to determine the effect on feed intake, milk yield, milk composition, and blood amino acids when soybean meal was replaced with fish meal. Fish meal substituted for soybean meal on an isonitrogenous basis at 0, 25, 50, and 100% of supplemental protein. Total mixed diets were (dry matter basis) 25% corn silage, 25% alfalfa hay, and 50% concentrate mix. Intake of dry matter (27.9, 27.8, 26.1, and 25.8 kg/d for diets 1 to 4, respectively) was similar for all diets. Milk yield (37.5, 37.8, 37.2, and 37.7 kg/d) was not affected by diets. Milk protein percentages (3.23, 3.24, 3.31, and 3.35) increased with 100% fish meal supplementation and tended to be higher, with 50% fish meal supplementation compared with 100% soybean meal diet. Milk fat percentages (3.18, 2.99, 3.04, and 2.87) and yields were lower with the 100% fish meal than with the 100% soybean meal diet. Molar proportions of ruminal volatile fatty acids and ammonia were not greatly affected by diet. Fish meal supplementation slightly improved Met status, as shown when blood amino acid data were evaluated. Both extraction efficiency and transfer efficiency of amino acids from the blood by the mammary gland indicated that Met, Lys, and Phe were the most limiting amino acids in all diets. Replacing as much as 50 or 100% of dietary soybean meal with fish meal may improve the amino acid balance and increase the protein content in milk; however, feeding 100% fish meal will likely decrease milk fat percentages.     

Influence of buffering early lactation rations with sodium bicarbonate and magnesium oxide and subsequent withdrawal or addition effects

Eighty animals (16 first lactation) were assigned alternately at calving to one of four treatments: A) corn silage, B) corn silage + 1.5% sodium bicarbonate and .5% magnesium oxide in the grain mix, C) 50% hay crop silage and 50% corn silage, and D) 50% hay crop silage and corn silage plus 1.5% sodium bicarbonate and .5% magnesium oxide. All rations contained 50% forage and 50% concentrate (dry) fed as a total mixed ration. During the first 8 wk of lactation no differences were detected in mean performance or in weekly patterns for forage programs alone or buffer treatments alone on average daily intake of dry matter, body weight loss, milk yield, or composition. Addition of buffers to hay crop silage and corn silage rations resulted in a milk yield profile with a smaller increase beyond wk 3 postpartum. Cows fed all corn silage rations yielded more milk on the average than cows on hay crop silage and corn silage, regardless of buffer treatments. From wk 9 through 12 of lactation, buffers either were added or withdrawn. Addition or withdrawal of buffers did not alter significantly patterns of milk yield or composition.     

Alfalfa Silage or Hay Versus Corn Silage as the Sole Forage for Lactating Dairy Cows

In Trial 1, three rations were fed to 21 cows in a 3 × 3 Latin square: 60% alfalfa silage, 60% corn silage, and 79% corn silage (dry matter basis) with the balance from corn and soybean meal. Acid detergent fiber measures indicated alfalfa and corn silage were of excellent quality. Milk production was similar on 60% forage rations but lower on 79% corn silage. Milk fat was reduced on 60% corn silage. In Trial 2, four rations were fed to 16 cows in a 4 × 4 Latin square: 63% alfalfa silage, 60% alfalfa hay, 60% corn silage, and 76% corn silage. Alfalfa forages were higher in acid detergent fiber but corn silage was similar to Trial 1. Dry matter digestibility was highest on 60% corn silage, intermediate on 63% alfalfa silage and 76% corn silage, and lowest on 60% alfalfa hay. Milk production was similar on the diets containing 60 and 63% forage and lower on 76% corn silage. Milk protein concentration was reduced on the alfalfa diets. Highest protein secretion and feed conversion was supported by 60% corn silage. In both trials, potentially digestible neutral detergent fiber from alfalfa was more digestible than that from corn silage, and concentrations of urea in milk and blood were highly correlated. Results indicate high quality alfalfa silage is comparable to corn silage for milk production.     

Effects of partial substitution of concentrates with maize silage in organic dairy cow rations on performance and feed efficiency

BACKGROUND: The general goal of organic dairy farming is to minimize purchased concentrate use and focus on milk production from forages. The aim of the present paper is to examine the influence of a partial substitution of purchased concentrates with home‐grown maize silage on feed intake, milk production and feed efficiency in rations for organic dairy cows. In the experimental treatment group (E), two‐thirds of average herd concentrate intake was replaced with 2.7 kg maize silage on a dry matter (DM) basis. RESULTS: In treatment E, total DM, energy and protein intake were significantly reduced compared to the control treatment group (C). Daily milk yield decreased in E by 11% and milk urea content was significantly lower. Calculated milk production from forage was significantly higher (91 versus 71%) in treatment E. Efficiency of dietary nitrogen (N) utilization (calculated as milk N as a percentage of N intake) was slightly improved in E and protein and energy balance (calculated as intake as a percentage of requirements) were closer to zero than in C. CONCLUSION: The present study indicates a potential to reduce levels of concentrates and substitute them with maize silage in organic dairy cow rations at least in the second half of lactation. Copyright © 2007 Society of Chemical Industry     

Corn silage versus corn silage:alfalfa hay mixtures for dairy cows: effects of dietary potassium, calcium, and cation-anion difference

Corn silage (CS) has replaced alfalfa hay (AH) and haylage as the major forage fed to lactating dairy cows, yet many dairy producers believe that inclusion of small amounts of alfalfa hay or haylage improves feed intake and milk production. Alfalfa contains greater concentrations of K and Ca than corn silage and has an inherently higher dietary cation-anion difference (DCAD). Supplemental dietary buffers such as NaHCO₃ and K₂CO₃ increase DCAD and summaries of studies with these buffers showed improved performance in CS-based diets but not in AH-based diets. We speculated that improvements in performance with AH addition to CS-based diets could be due to differences in mineral and DCAD concentrations between the 2 forages. The objective of this experiment was to test the effects of forage (CS vs. AH) and mineral supplementation on production responses using 45 lactating Holstein cows during the first 20 wk postpartum. Dietary treatments included (1) 50:50 mixture of AH and CS as the forage (AHCS); (2) CS as the sole forage; and (3) CS fortified with mineral supplements (CaCO₃ and K₂CO₃) to match the Ca and K content of the AHCS diet (CS-DCAD). Feed intake and milk production were equivalent or greater for cows fed the CS and CS-DCAD diets compared with those fed the AHCS diet. Fat percentage was greater in cows fed the CS compared with the AHCS diet. Fat-corrected milk (FCM; 3.5%) tended to be greater in cows fed the CS and CS-DCAD diets compared with the AHCS diet. Feed efficiencies measured as FCM/dry matter intake were 1.76, 1.80, and 1.94 for the AHCS, CS, and CS-DCAD diets, respectively. The combined effects of reduced feed intake and increased FCM contributed to increased feed efficiency with the CS-DCAD diet, which contained 1.41% K compared with 1.18% K in the CS diet, and we speculate that this might be the result of added dietary K and DCAD effects on digestive efficiency. These results indicate no advantage to including AH in CS-based diets, but suggest that improving mineral supplementation in CS-based diets may increase feed efficiency.     

Effect of varying protein and energy densities in complete rations fed to cows in first lactation

Sixty-three Holstein cows in first lactation were allotted randomly at 28 days postpartum to receive one of nine rations in a 3 X 3 factorial design. Rations had crude protein 12, 15, or 18% in each of three energy densities from ratios of forage:concentrate of 75:25, 55:45, and 35:65. Corn silage and hay crop silage were combined in a ratio of 2:1 (dry basis) in each case, and diets were offered for ad libitum intake as complete feeds for an 11-wk experimental period plus 2 wk for a digestion trial. In regression analysis as energy density increased, feed intake, milk yield, milk protein, and lactose yields increased linearly, urea nitrogen in blood plasma decreased linearly, and milk fat percent and yield decreased curvilinearly. As dietary protein increased, feed intake, fat-corrected milk, milk fat yield, and plasma urea nitrogen increased linearly, and yields of milk, solids-corrected milk, milk protein, and lactose increased curvilinearly. Actual milk yield adjusted for dry matter intake increased with greater energy density but not with higher protein concentration. Increases of energy and protein each resulted in linear increases of digestibility of dry matter, crude protein, and energy of diets. There were no interactions of energy X protein for these measurements. Cows in first lactation will increase milk production in response to increasing protein over a range of energy densities when feed intake is increased.     

Influence of dietary fish oil on conjugated linoleic acid and other fatty acids in milk fat from lactating dairy cows

Lactating cows were fed menhaden fish oil to elevate concentrations of conjugated linoleic acid, transvaccenic acid, and n-3 fatty acids in milk. Twelve multiparous Holstein cows at 48+/-11 DIM were assigned randomly to a replicated 4 x 4 Latin square. Each treatment period was 35 d in length, with data collected d 15 to 35 of each period. On a dry matter (DM) basis, diets contained 25% corn silage, 25% alfalfa hay, and 50% of the respective concentrate mix. Fish oil was supplemented at 0, 1, 2, and 3% of ration DM. Linear decreases were observed for DM intake (28.8, 28.5, 23.4, and 20.4 kg/d) and milk fat (2.99, 2.79, 2.37, and 2.30%) for 0 to 3% dietary fish oil, respectively. Milk yield (31.7, 34.2, 32.3, and 27.4 kg/d) increased as dietary fish oil increased from 0 to 1% but decreased linearly from 1 to 3% dietary fish oil. Milk protein percentages (3.17, 3.19, 3.21, and 3.17) were similar for all treatments. When the 2% fish oil diet was fed, concentrations of conjugated linoleic acid and transvaccenic acid in milk fat increased to 356% (to 2.2 g/ 100 g of total fatty acids) and 502% (to 6.1 g/100 g), respectively, of amounts when 0% fish oil was fed. There were no additional increases in these fatty acids when cows were fed 3% fish oil. The n-3 fatty acids increased from a trace to over 1 g/100 g of milk fatty acids, when the 3% fish oil diet was fed. Fish oil supplementation to diets of dairy cows increased the conjugated linoleic acid, transvaccenic acid, and n-3 fatty acids in milk.     

Sensory quality of marinated frozen stored chicken thighs as affected by dietary fish fat and vitamin E

The effects of diets containing fish meal (0 or 4%), fish silage (0 or 4%) and vitamin E (60 or 200 mg kg^–1) and the processing effect of marinating with sodium citrate (0.24 or 0.48%) or ascorbate (0.31 or 0.62%) have been studied to test the hypothesis that oxidative stability of frozen stored chicken thighs can be improved by such treatments. A trained sensory panel assessed the samples after storage at –25 °C for 1 week, 3 and 6 months. Feed with 4% fish meal resulted in increased fish flavour and odour of the thighs while 4% fish silage had a smaller effect on these attributes. Fish meal and fish silage added together into the feed by an amount of 4% each, caused strong fish flavour and odour in the product and accelerated the rancidity process. High concentration of vitamin E (200 mg kg^–1) in the feed reduced rancidity when 4% fish products had been added to the feed, but no effect was noted when 4% fish meal plus 4% fish silage had been added together. High concentration of ascorbate in the brine (0.62%) decreased sensory score for rancidity attributes (hay, grass, soap and paint), while high concentration of citrate (0.48%) increased these parameters in frozen stored chicken thighs.     

Chromium concentrations in ruminant feed ingredients

Chromium (Cr), in the form of Cr propionate, has been permitted for supplementation to cattle diets in the United States at levels up to 0.50 mg of Cr/kg of DM since 2009. Little is known regarding Cr concentrations naturally present in practical feed ingredients. The present study was conducted to determine Cr concentrations in feed ingredients commonly fed to ruminants. Feed ingredients were collected from dairy farms, feed mills, grain bins, and university research farms. Mean Cr concentrations in whole cereal grains ranged from 0.025 mg/kg of DM for oats to 0.041 mg/kg of DM for wheat. Grinding whole samples of corn, soybeans, and wheat through a stainless steel Wiley mill screen greatly increased analyzed Cr concentrations. Harvested forages had greater Cr concentrations than concentrates, and alfalfa hay or haylage had greater Cr concentrations than grass hay or corn silage. Chromium in alfalfa hay or haylage (n = 13) averaged 0.522 mg/kg of DM, with a range of 0.199 to 0.889 mg/kg of DM. Corn silage (n = 21) averaged 0.220 mg of Cr/kg of DM with a range of 0.105 to 0.441 mg of Cr/kg of DM. By-product feeds ranged from 0.040 mg of Cr/kg of DM for cottonseed hulls to 1.222 mg of Cr/kg of DM for beet pulp. Of the feed ingredients analyzed, feed grade phosphate sources had the greatest Cr concentration (135.0 mg/kg). Most ruminant feedstuffs and feed ingredients had less than 0.50 mg of Cr/kg of DM. Much of the analyzed total Cr in feed ingredients appears to be due to Cr contamination from soil or metal contact during harvesting, processing, or both.     

Effects of fish meal protein supplementation on milk yield and composition and blood constituents of dairy cows

Ten holstein and 10 Ayrshire cows were fed diets containing undegradable intake protein from either fish meal or corn gluten meal. Cows were introduced to diets 10 d before projected calving date and individually fed blended rations until 60 d postpartum. Diets were balanced for NE1, CP, and degradable and undegradable protein. Source of undegradable protein did not affect total or FCM yields, DM intake, or milk protein percentage. Cows on fish meal diets tended to lose less BW than those on the corn gluten meal supplement (5.3 vs. 10.3% loss of initial BW). Fish meal supplementation resulted in decreased milk fat and SNF percentage (3.2 vs. 4.2% and 8.37 vs. 8.65%, respectively), but diet did not affect total milk fat, protein, or SNF yield. Plasma nonesterified fatty acids decreased and serum insulin increased with increasing weeks postpartum but were not affected by diet. In this study, no significant advantage was found to using fish meal as a source of undegradable intake protein and feed cost was higher when it was used.     

Conjugated linoleic acid content of milk from cows fed different diets.

Conjugated linoleic acid in milk was determined from cows fed different diets. In Experiment 1, cows were fed either normal or high oil corn and corn silage. Conjugated linoleic acid was 3.8 and 3.9 mg/g of milk fatty acids in normal and high oil treatments, respectively. In Experiment 2, cows consumed one-third, two-thirds, or their entire feed from a permanent pasture. Alfalfa hay and concentrates supplied the balance of feed for the one-third and two-third pasture treatments. Conjugated linoleic acid was 8.9, 14.3, and 22.1 mg/g of milk fatty acids in the one-third, two-third, and all pasture treatments, respectively. Cows grazing pasture and receiving no supplemental feed had 500% more conjugated linoleic acid in milk fat than cows fed typical dairy diets (Experiment 1). In Experiment 3, cows were fed either a control diet containing 55% alfalfa silage and 45% grain, or similar diets supplemented with 3% fish meal, or 250 g of monensin/cow/per day, or fish meal and monensin together. Conjugated linoleic acid was 5.3, 8.6, 6.8, and 8.9 mg/g of milk fatty acids in the control, fish meal, monensin, and fish meal plus monensin treatments, respectively. In Experiment 4, cows were fed either finely chopped alfalfa hay (Treatment 1), or coarsely chopped alfalfa hay (Treatment 2) in a 50% forage and 50% grain diet, or 66.6% grass hay and 33.4% grain (Treatment 3), or 98.2% grass hay (Treatment 4). Conjugated linoleic acid was 7.3, 8.3, 9.0, and 7.9 mg/g of milk fatty acids in treatments 1 through 4, respectively.     

Measuring feed intake patterns and meal size of lactating dairy cows

Length, size, and interval between eating bouts were determined for four forages with two lactating dairy cows. The forages were low dry matter alfalfa haylage, high dry matter alfalfa haylage, alfalfa hay, and alfalfa pellets. Recordings were made for 96-h periods, and nibbling bouts were separated from meals according to the time and weight of eating bouts. Meal data were analyzed by a stepwise least squares analysis to determine the best model for characterizing feed intake data for lactating dairy cows. Initial meal size and lengths were not different; however, interval following the initial meal was longer on the alfalfa pellet diet. Spontaneous meals were similar in number and size for all diets; however, meal length was increased on the alfalfa hay diet. Total daily dry matter intakes were not different for the four diets. It is important to distinguish between nibbling and meals for effective analysis of intake, feeding behavior, and meal patterns.     

Effects of differences in starch content of diets with whole cottonseed or rice bran on milk casein

Forty lactating Holstein cows in early to midlactation were used in a randomized complete block design to measure the effects of the following diets on milk casein. Treatments were four complete rations fed for ad libitum intake consisting of 1) 60% concentrate, 10% alfalfa hay, and 30% corn silage; 2) 45% concentrate, 10% alfalfa hay, 30% corn silage, and 15% whole cottonseed; 3) 60% concentrate, 5% alfalfa hay, 20% corn silage, and 15% whole cottonseed; and 4) 45% concentrate, 10% alfalfa hay, 30% corn silage, and 15% rice bran. Least squares means for daily DM intake all were significantly different and were 3.51, 3.90, 3.28, and 3.74% BW, respectively. Cows fed diet 3 had higher arterial glucose and insulin and venous insulin. Least squares means were significantly different for milk yield, 30.1, 31.4, 28.4, and 31.6 kg/d; for milk protein, 3.30, 3.13, 3.48, and 3.12%; and for casein N, .376, .358, 3.73, and .330, respectively. However, milk protein and casein N yields were similar for all cows. The diet that contained the highest percentage of starch did not result in a significantly higher percentage of casein N in the milk but had the lowest milk production. Both whole cottonseed and rice bran, substituted for concentrate, depressed milk protein percentage.     

Possibilities for the utilisation of marine by‐products

Fish industry by‐products can account for up to 75% of the catch depending on postharvest or industrial preparation processes. Different terms such as ‘fish waste’, ‘by‐product’ and ‘rest raw materials’ have been used. The review gives an overview of value‐added processes that provide an alternative to low‐profit uses such as silage, fish meal and mince. The preparation of different by‐product fractions such as fish blood, marine lipids, omega‐3 fatty acids, fish protein fractions and bioactive components with nutraceutical potential, i.e. antioxidants and bioactive peptides, is considered. There are several future opportunities for the preparation of high‐value by‐products such as enzymes, minerals and other bioactive substances including hydroxyapatite, phosphorus, taurine and creatine. Both regulatory status and future market potential need to be considered. In addition, there is a need for technologies that maintain good quality by‐products and ‘simple’ processes to produce bulk products for further refining.     

Supplementation of dairy cow diets with ammonium salts of volatile fatty acids

The objective was to determine the efficacy of a blend of ammonium salts of the volatile fatty acids, isobutyric, 2-methylbutyric, isovaleric, and valeric as a supplement to diets for dairy cows. Treatments of 0 (control) or 120 (supplemented) g/cow of the blend were fed daily from approximately 3 wk prepartum through a complete lactation. Five trials were conducted concurrently with a total of 116 multiparous Holstein cows. Dietary ingredients or combinations of ingredients differed in each of the trials. Diets contained either 1) corn gluten meal and urea, 2) soybean meal, or 3) cottonseed meal as the primary grain source of crude protein. The forage portion of the diets contained corn silage in combination with one or more of the following: alfalfa hay, alfalfa haylage, or wheat silage. Cows fed the supplement produced more milk and fat-corrected milk than the control cows for the 305-d lactation on four of the five diets, resulting in an average increase of 1.7 kg/d or 7%. Feed intake of cows on the supplemented diet was generally similar or lower than intake of the control cows throughout lactation, indicating that increased milk yield was associated with improved feed utilization. Percent milk fat was similar for cows on the supplemented diet, but fat yield was higher. Percent milk protein was lower for supplemented cows, but protein yield was about the same for both treatments because of higher milk yield. Health and reproduction were similar for all cows.