Protein nutrition of dairy cows receiving grass silage diets. Effects on silage intake and milk production of postruminal supplements of casein or soya-protein isolate and the effects of intravenous infusions of a mixture of methionine,phenylalanine and tryptophan

Milk production responses to protein supplementation of grass silage diets were investigated in two experiments with dairy cows. In Experiment 1. four cows received a basal diet of grass silage ad libitum plus a barley/soya supplement at 5 kg day^?1. The cows received the following treatments in a 4 × 4 Latin square design with 10-day periods: (1) basal diet, (2) basal diet plus 230 g casein day^?1 infused into the abomasum; (3) basal diet plus 225 g soya protein isolate (SPI) day^?1 into the abomasum; and (4) basal diet plus a dietary addition of 1.2 kg fishmeal-based product (AP) day^?1. All three supplements increased (P < 0.05) the yield of milk and milk protein relative to the basal diet, the values being 16.9. 535:18.8. 610; 19.5, 625; and 18.5 kg day^?1 and 582 g day^?1 for the basal. AP, casein and SPI treatments respectively. Responses to casein were greater (P < 0.05) than to SPI. Changes in the concentrations of amino acids in blood plasma suggested that methionine, tryptophan and phenylalanine were in shortest supply relative to demand, and their potential role as limiting amino acids was investigated in a second experiment. In Experiment 2, four dairy cows were used in a 4 × 4 Latin square design with 10-day periods. The four treatments were (1) a diet of grass silage ad libitum plus 5 kg day^?1 of a barley/soya supplement containing 176 g CP kg^?1 DM (LP); (2) LP plus an intravenous infusion of 5.0 g methionine, 9.1 g phenylalanine and 2.2 g tryptophan day^?1; (3) grass silage ad libitum plus 5 kg day^?1 of a barley/soya supplement containing 334 g CP kg^?1 DM (HP); and (4) HP plus the intravenous infusion of methionine, phenylalanine and tryptophan. The HP treatment produced a higher yield (P < 0.05) of milk protein than the LP treatment (722 vs. 667 g day^?1) but the amino acid infusion had no effect with either treatment. The elimination of methionine, phenylalanine and tryptophan (and, in previous experiments, methionine and lysine) as candidates for limiting amino acids on diets of grass silage plus soya-based supplements questions whether the differences in responses to casein and SPI can be explained in terms of their amino acid compositions. The role of factors such as peplides, producing during digestion, some of which may be biologically active, deserves investigation.     

The extent of hydrogenation of two formaldehyde-treated spray-dried mixtures of soya bean oil and casein fed to sheep

Two experiments have been carried out to determine the degree of protection of soya bean oil mixed with sodium caseinate, spray-dried and treated with formaldehyde. In experiment 1, the mixture contained two parts of oil to one part of sodium caseinate. In experiment 2, the mixture contained six parts of oil to one part of sodium caseinate. The animals also received either no added oil, or the same amount of free oil and, in experiment 2, the powder without any formaldehyde treatment. The basal diet used consisted of equal amounts of dried grass cubes and flaked maize. There were no statistically significant effects on the apparent digestibility of the dry matter, organic matter, nitrogen or total fatty acid. The amount of polyunsaturated fatty acids (18:2 and 18:3) voided in the faeces was not affected by the form of oil. The amount of 18:0 and 18:1 in the faeces was increased by all the different forms of oil. The proportion of polyunsaturated fatty acids in both the solid and the liquid parts of the rumen digesta was markedly increased when the protected powder was added to the diet. This effect was most marked in the liquid. The amount of polyunsaturated fatty acids flowing to the duodenum was markedly increased when the protected powder was given. Of the 18:2 and 18:3 fatty acids added to the food in the soya bean oil, less than 6% passed to the duodenum when either loose oil or unprotected powder was added whereas, when the protected powder was added in experiment 1, 66% of the added polyunsaturated fatty acid passed to the duodenum and the corresponding figure in experiment 2 was 40%. It is concluded that the method of protection used was reasonably effective but that the amount of casein in the second preparation was not sufficient to afford optimum protection.     

Exocrine Pancreatic Secretions in Young Pigs Fed Diets Containing Faba Beans (Vicia faba) and Peas (Pisum sativum): Nitrogen,Protein and Enzyme Secretions

Two experiments were carried out to investigate the effect of feeding diets containing faba beans and peas on pancreatic secretions in young pigs fitted with a pancreatic pouch re-entrant cannula. In Experiment 1, eight barrows, with an average initial weight of 8·5 kg, were fed one of two maize starch-based diets formulated to contain 200 g crude protein (CP) kg⁻¹ according to a completely randomised design. In one of the diets, soya bean meal was the sole protein source; in the other diet, soya bean meal and faba beans (cv Fibro; dark-flowering) each supplied 50% of the dietary CP. In Experiment 2, five barrows, with an average initial weight of 18·1 kg, were fed one of two diets according to a two-period change-over design. The diets were formulated to contain 150 g CP kg⁻¹ with peas (cv Ascona or cv Radley) as the sole protein source. In both experiments, the experimental periods consisted of 8 days: 6 days adaptation followed by a 2 day collection of pancreatic juice. The soya bean meal diet and the faba bean diet contained 0.04 and 0.21% tannins (catechin equivalents), respectively. The trypsin inhibitor activities of the Ascona and Radley pea diets were 0·76 and 3·24 mg of trypsin inhibited per gram, respectively. In both experiments, diet did not affect ( P> 0·05) the pancreatic secretions of nitrogen, protein, amylase, lipase and chymotrypsin. In Experiment 1, specific trypsin activity was higher ( P< 0·05) in pancreatic juice from pigs fed the diet containing soya bean meal and faba beans (53700 units litre⁻¹) than for those fed the soya bean meal diet (41200 units litre⁻¹). However, there was no effect ( P> 0·05) when trypsin activity was expressed as total activity (units 24 h⁻¹). It is concluded that the inclu-sion of faba beans and peas in diets for young pigs has only minor effects on exocrine pancreatic secretions.     

Genotype,environment and genotype × environment effects on trypsin inhibitor in peas

Four multiparous ruminally canulated cows and four primiparous cows without a ruminal cannula were used in a 4 × 4 Latin square experiment to study the effect of dietary fat source on milk fatty acid composition. Cows were fed a diet containing 550 g lucerne silage and 450 g concentrate kg^?1 dietary DM. The four diets were control and fat supplementation (32 g fat kg^?1 diet DM) as roasted soya beans, calcium salts of palm oil fatty acids (Megalac®). or hydrogenated tallow (Alifet®). Cows fed supplemental fat as roasted soya beans. Megalac®. or Alifet® produced 33.8, 32.6, and 32.5 kg day^?1 of 3.5% FCM. respectively, compared with 31.6 kg day^?1 with no fat supplementation. Addition of fat decreased milk protein percentage. Milk fat percentage was increased with Megalac® and decreased with Alifet® feeding. Dietary fat decreased the proportion of short- and medium-chain fatty acids (C6-C14:0) in milk and increased the proportion of long-chain fatty acids (C16 : 0 and longer). Roasted soya beans were most effective in reducing C16 : 0 and increasing C18 : 1, C18 : 2 and C18 : 3 acids in milk fat. Megalac® did not decrease milk C16 : 0 content, and neither Megalac® nor Alifet® affected C18 : 2 content.     

Accumulation and quality of storage protein in developing cowpea,mung bean and soya bean seeds

This study was carried out to compare the time course of laying down seed storage protein in three legumes viz: cowpea (Vigna unquiculata), mung bean (Phaseolus aureus) and soya bean (Glycine max) planted in two replications. Pods were harvested periodically during seed maturation and studied for changes in fresh and dry weights, total sulphur, total nitrogen and protein content. At early stages of development crude protein formed about one-third of dry weight in the legumes but decreased to about one-quarter at maturity. The total sulphur which formed a substantial amount of the sulphur amino-acids in mature seeds did not change much in mung bean and cowpea but increased by about 24% from 20 to 69 days after flowering (DAF) in soya bean. Storage protein accumulation was very rapid between 10 and 14 DAF (10.4% day^?1) in mung bean, 7 and 14 DAF (12.9% day^?1) in cowpea and between 20 and 30 DAF (9.4 day^?1) in soya bean. Thereafter, protein accumulation declined slightly and gradually approached zero at time of seed maturity. The sulphur-to-nitrogen ratios gradually increased with maximum values in the mature seeds. Although seed protein content and quality (on S/N ratio basis) were highest in soya bean, accumulation of storage protein seemed to be faster in cowpea than mung bean and soya bean during seed maturation.     

Processed fava bean as a substitute for rapeseed meal with or without rumen-protected methionine supplement in grass silage-based dairy cow diets

Fava bean offers a sustainable home-grown protein source for dairy cows, but fava bean protein is extensively degraded in the rumen and has low Met concentration. We studied the effects of protein supplementation and source on milk production, rumen fermentation, N use, and mammary AA utilization. The treatments were unsupplemented control diet, and isonitrogenously given rapeseed meal (RSM), processed (dehulled, flaked, and heated) fava bean without (TFB) or with rumen-protected (RP) Met (TFB+). All diets consisted of 50% grass silage and 50% cereal-based concentrate including studied protein supplement. The control diet had 15% of crude protein and protein-supplemented diets 18%. Rumen-protected Met in TFB+ corresponded to 15 g/d of Met absorbed in the small intestine. Experimental design was a replicated 4 × 4 Latin square with 3-wk periods. The experiment was conducted using 12 multiparous mid-lactation Nordic Red cows, of which 4 were rumen cannulated. Protein supplementation increased dry matter intake (DMI), and milk (31.9 vs. 30.7 kg/d) and milk component yields. Substituting RSM with TFB or TFB+ decreased DMI and AA intake but increased starch intake. There were no differences in milk yield or composition between RSM diet and TFB diets. Rumen-protected Met did not affect DMI, or milk or milk component yields but increased milk protein concentration in comparison to TFB. There were no differences in rumen fermentation except for increased ammonium-N concentration with the protein-supplemented diets. Nitrogen-use efficiency for milk production was lower for the supplemented diets versus control diet but tended to be greater for TFB and TFB+ versus RSM. Protein supplementation increased plasma essential AA concentration but there were no differences between TFB diets and RSM. Rumen-protected Met clearly increased plasma Met concentration (30.8 vs. 18.2 µmol/L) but did not affect other AA. Absence of differences between RSM and TFB in milk production together with limited effects of RP Met suggest that TFB is a potential alternative protein source for dairy cattle.     

Estimates of the efficiency of transfer of L‐histidine from blood to milk when it is the first‐limiting amino acid for secretion of milk protein in the dairy cow

The efficiency of transfer of L ‐histidine into milk protein was measured in two experiments in which L ‐histidine was infused intravenously into dairy cows eating a basal diet of grass silage and a cereal‐based supplement containing feather meal. Both experiments used Latin square designs, and infusion periods lasted 10 days. In Experiment 1, histidine was infused alone at doses of 3, 6 and 9 g day^?1. The output of milk protein increased up to the 6 g day^?1 dose but fell back to the basal level when 9 g day^?1 was infused. The efficiency of transfer was highest for the 6 g day^?1 dose, for which the value was 0.38. In Experiment 2 the same three histidine doses as in Experiment 1 were used, but this time the histidine was accompanied by 8 g L ‐methionine, 28 g L ‐lysine and 2.5 g L ‐tryptophan, to ensure that histidine remained first‐limiting over the whole dose range. The output of histidine in milk protein (Y) increased linearly with histidine dose (X) such that Y = 0.431 X + 0.070 r = 0.998; n = 4, indicating an efficiency of transfer of 0.43. © 2001 Society of Chemical Industry     

Changes in Soya Bean Lipid Profiles during Kinema Production

The influence of processing on soya bean lipids during kinema production was studied. The crude lipid (CL), free fatty acid (FFA) and phytosterol contents of raw beans were 121 g, 6·9 g and 0·8 g kg⁻¹ dry matter, respectively. After soaking and cooking the moisture content of beans increased significantly from 121 to 749 g kg⁻¹, whilst the lipid contents were unchanged. During a 2 day fermentation at 37°C, the lipid contents increased significantly as indicated by capillary column gas chromatography (GC) analysis of petroleum ether extracts of lyophilised samples of unfermented and fermented beans. The fatty acids, palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3) and arachidic (C20:0) acids were identified. The major fatty acid present in all samples was the essential fatty acid, linoleic acid. All of the aforementioned fatty acids (except arachidic) were liberated during fermentation by microbial lipases, yielding approximately the same proportion of fatty acids found in unfermented beans. The unsaponifiable soya bean lipids identified by GC were campesterol, stigmasterol and β-sitosterol (ratio 1·2:1:3·4). Levels of these increased during fermentation by 50–61%, but remained in approximately the same proportions.     

Dietary manipulation of the yield and composition of milk: Effects of dietary inclusions of barley and oats in untreated or formaldehyde-treated forms on milk fatty acid composition

Eight 1st-lactation cows were given four dietary treatments in a duplicated 4×4 Latin square experiment. Diets consisted of hay and soya bean meal together with barley, formaldehyde-treated barley, oats or formaldehydetreated oats (approximately 34:12:54 on a dry matter basis). Barley diets supplied 211 g fatty acids d^?1, oats diets supplied 537 g d^?1. The fatty acid composition (g kg^?1 total fatty acids) for barley diets was: 300 (16:0); 20 (18:0); 150 (18:1); 470 (18:2); 60 (18:3). Corresponding values for oats diets were 180, 20, 390, 380 and 30 g kg^?1. Formaldehyde treatment of the cereals tended to increase milk yield and reduce milk fat content (P<0·01 for barley) but did not affect milk fatty acid composition. Feeding oats in replacement for barley significantly (P<0·05) increased milk yield and lactose yield and reduced milk fat content (P<0·05 for the untreated cereals) and protein contents (P<0·01) without significant effects on milk fat or protein yields. Oats diets led to significant (P<0·001) reductions in the content of 8:0–16:0 fatty acids in milk fat with associated increases (P<0·001) in the content of 18:0 and 18:1. Changes in milk fat content of 18:2 and 18:3 acids were small. The results show the inclusion of oats in the cow's diet to be a means of reducing the saturated fatty acid content of milk fat thereby improving the nutritional value of milk and milk products and their appeal to the health-conscious consumer.     

The effect of dietary-induced changes in milk urea levels on the heat stability of milk

Two experiments were carried out to investigate the relationship between milk urea content and the heat stability of the protein in the skim milk. In experiment 1, four cows were offered a diet of grass silage with different amounts of hay and a protein concentrate. Although there were individual differences between the cows in the relationship between coagulation time and milk pH, there was a significant correlation between milk urea content and the maximum coagulation time. In experiment 2, two groups of five cows were given a basal diet of hay with a supplement of either barley or soya bean meal. These diets were exchanged weekly over a 3 week period. A significant correlation between milk urea content and maximum coagulation time was observed, and a close relationship between milk urea content and the mean urea content of the blood found. It is concluded that, although milk urea content is not the sole determinant of coagulation time, there is considerable potential for manipulating the urea content of milk in order to increase the heat stability.     

Exocrine Pancreatic Secretions in Young Pigs Fed Diets Containing Faba Beans (Vicia faba) and Peas (Pisum sativum): Concentrations and Flows of Total,Protein-Bound and Free Amino Acids

Two experiments were carried out to investigate the effects of feeding diets containing faba beans and peas on the concentration, flow and composition of total, protein-bound and free amino acids (AA) in pancreatic juice collected from young pigs fitted with a pancreatic pouch re-entrant cannula. In Experiment 1, eight barrows, with an average initial weight of 8·5 kg, were fed one of two semi-purified diets formulated to contain 200 g kg⁻¹ crude protein (CP) according to a completely randomised design. In one of the diets, soya bean meal was the sole protein source; in the other diet, soya bean meal and faba beans (cv Fibro; dark-flowering) each supplied 50% of the dietary CP. In Experiment 2, five barrows, with an average initial weight of 18·1 kg, were fed one of two diets formulated to contain 150 g kg⁻¹ CP with peas (cv Ascona or cv Radley) as the sole protein source. There was no effect (P>0·05) of the diet, 8 h sampling period or experimental period on the concentration (mM), composition (% and g 16 g N⁻¹) and flow (mmol 24 h⁻¹) of total, protein-bound and free AA or on the percentage of protein-bound AA in pancreatic juice. The concentrations of total, protein-bound and free AA were higher in pancreatic juice collected from younger pigs in Experiment 1 than in pancreatic juice collected from older pigs in Experiment 2. However, the daily flows of total, protein-bound and free AA in pancreatic juice were similar in both experiments. The percentages of protein-bound AA in pancreatic juice were similar in both experiments. In conclusion, the concentrations, compositions and flows of total, protein-bound and free AA in pancreatic juice were not affected by diet, 8 h sampling period or experimental period.     

Protein nutrition of dairy cows receiving grass silage diets: Effects of feeding a protein supplement of unbalanced amino acid composition

Eight cows were used in a replicated 4 × 4 latin square design experiment with period lengths of 3 weeks to investigate the effects of protein supplementation of a grass silage diet on silage intake and milk production. The four treatments were (i) the basal diet, consisting of grass silage ad libitum plus 2 kg day^?1 of molassed sugar beet pulp; (ii) basal diet plus 1 kg day^?1 of fish meal (F): (iii) basal diet plus 0.8 kg day^?1 of feather meal 1 (FE1); and (iv) basal diet plus 0.8 kg day^?1 of feather meal 2 (FE2). Silage intake was significantly (P < 0.01) increased by the F supplement but was not affected by the FE supplements; values were 9.9, 10.6, 9.6 and 9.6 kg DM day^?1 for basal, F, FE1 and FE2, respectively. Relative to the basal treatment, F increased (P < 0.001) the yield of milk and milk protein but, again, these were unaffected by FE; values were, for milk yield, 13.6, 16.3, 13.7 and 13.1 kg day^?1; and, for milk protein yield, 420, 545, 429 and 414 g day^?1 for basal, F, FE1 and FE2, respectively. However, supplementation with FE produced increases in the concentration (P < 0.001) and yield (P < 0.05) of milk fat; values were 42.8, 39.9, 46.6 and 47.8 g kg^?1 and 575, 646, 628 and 618 g day^?1 respectively, for the basal, F, FE1 and FE2 treatments. The profile of amino acids in blood plasma was characterised by markedly lower (at least P < 0.01) concentrations of methionine, lysine, tryptophan and histidine for the diets containing FE compared with F. The results show pronounced effects of the amino acid composition of the undegraded protein component of the supplement on both silage intake and milk production but also draw attention to a possible relationship between amino balance and the secretion of milk fat.     

Urea on Flaked Soybean Hulls as a Protein Replacement for Dairy Cows

In Experiment I a Latin square design was used to study the utilization of urea nitrogen adsorbed on flaked soybean hulls in normal rations of high producing dairy cows. Concentrates containing urea, urea with supplemental minerals, or soybean meal as the protein supplement were fed with corn silage and alfalfa in a total ration of approximately 17% crude protein. Both urea concentrates contained 2.7% urea. Animals fed urea and soybean had similar milk yields (28.7 and 27.9 kg/day), milk protein, and digestible dry matter intakes. Urea with mineral produced lower milk yield (25.3 kg/day), milk protein, and dry matter intakes, probably because of excessive mineral content. Urea nitrogen of plasma was similar for all three diets. Essential amino acids of plasma were lower for urea than for soybean while for urea mineral the essential amino acids were midway between the other two. In Experiment 2 a switchback design was used to compare the urea-soybean hull concentrate diet of Experiment 1 (17% crude protein) to a negative control diet consisting of its basal components without urea adjusted to 12% protein with wheat bran. Milk yield was 1.2 kg/day higher when the urea diet was fed. Perhaps due to improved urea distribution in the rumen, flaked soybean hulls with urea were effective in maintaining the feed intake necessary for high milk production.     

The yield,fatty acid composition and physical properties of milk fat obtained by feeding soya oil to dairy cows

The presence in the bovine mammary gland of a desaturase specific for the conversion of stearic to oleic acid allows the manipulation of the physical properties of milk fat by varying the dietary intake of C₁₆ and C₁₈ fatty acids. In particular, feeding the dairy cow an oil with a high C₁₈: C₁₆ ratio should allow the proportion of milk fat that is liquid at 5°C to be increased, with a consequent improvement in the low-temperature spreadability of butter. In this paper, the effect of feeding concentrate rations containing (a) soya oil as the free oil and as cracked soya beans; (b) various levels of soya oil, the ration being offered twice or 24-times daily, on the thermal properties of the milk fat and on the yield of milk constituents is examined in detail. Feeding ratios containing free soya oil greatly increased the proportion of milk fat liquid at 5°C, whereas cracked soya oil gave only slight increases. Proportion and yield of milk fat were decreased by feeding soya oil twice daily but were increased by continuous feeding.     

Effects of replacement of barley with oats on milk fatty acid composition in dairy cows fed grass silage-based diets

This study consists of milk fatty acid (FA) data collected during 2 in vivo experiments. For this study, 8 cows from each experiment were included in a replicated 4 × 4 Latin square design. At the start of experiment 1 (Exp1) cows were at (mean ± standard deviation) 87 ± 34.6 d in milk, 625 ± 85.0 kg of body weight, and 32.1 ± 4.17 kg/d milk yield and at the start of experiment 2 (Exp2) cows were at 74 ± 18.2 d in milk, 629 ± 87.0 kg of body weight, and 37.0 ± 3.2 kg/d milk yield. In Exp1, we examined the effects of gradual replacement of barley with hulled oats (oats with hulls) on milk FA composition. The basal diet was grass silage and rapeseed meal (58 and 10% of diet DM, respectively), and the 4 grain supplements were formulated so that barley was gradually replaced by hulled oats at levels of 0, 33, 67, and 100% on dry matter basis. In Exp2, we examined (1) the effects of replacing barley with both hulled and dehulled oats (oats without hulls) and (2) the effects of gradual replacement of hulled oats with dehulled oats on milk FA composition. The basal diet was grass silage and rapeseed meal (60 and 10% of diet DM, respectively), and the 4 pelleted experimental concentrates were barley, hulled oats, a 50:50 mixture of hulled and dehulled oats, and dehulled oats on dry matter basis. In Exp1, gradual replacement of barley with hulled oats decreased relative proportions of 14:0, 16:0, and total saturated FA (SFA) in milk fat linearly, whereas proportions of 18:0, 18:1, total monounsaturated FA, and total cis unsaturated FA increased linearly. Transfer efficiency of total C18 decreased linearly when barley was replaced by hulled oats in Exp1. In Exp2, relative proportions of 14:0, 16:0, and total SFA were lower, whereas proportions of 18:0, 18:1, monounsaturated FA, and cis unsaturated FA were higher in milk from cows fed the oat diets than in milk from cows fed the barley diet. Moreover, in Exp2, gradual replacement of hulled oats with dehulled oats slightly decreased the relative proportion of 14:0 in milk fat but did not affect the proportions of 16:0, 18:0, 18:1, total SFA, monounsaturated FA, trans FA, or polyunsaturated FA. In Exp2, transfer efficiency of total C18 was lower when cows were fed the oat diets than when fed the barley diet and decreased linearly when hulled oats were replaced with dehulled oats. Predictions of daily CH₄ emissions (g/d) using the on-farm available variables energy-corrected milk yield and body weight were not markedly improved by including milk concentrations of individual milk FA in prediction equations. In conclusion, replacement of barley with oats as a concentrate supplement for dairy cows fed a grass silage-based diet could offer a practical strategy to change the FA composition of milk to be more in accordance with international dietary guidelines regarding consumption of SFA.     

Effects of forage type, forage to concentrate ratio, and crushed linseed supplementation on milk fatty acid profile in lactating dairy cows

The effects of an increasing proportion of crushed linseed (CL) in combination with varying forage type (grass or corn silage) and forage to concentrate ratio (F:C), and their interactions on milk fatty acid (FA) profile of high-producing dairy cows was studied using a 3-factor Box-Behnken design. Sixteen Holstein and 20 Swedish Red cows were blocked according to breed, parity, and milk yield, and randomly assigned to 4 groups. Groups were fed different treatment diets formulated from combinations of the 3 main factors each containing 3 levels. Forage type (fraction of total forage dry matter, DM) included 20, 50, and 80% grass silage, with the remainder being corn silage. The F:C (DM basis) were 35:65, 50:50, and 65:35, and CL was supplied at 1, 3, and 5% of diet DM. Starch and neutral detergent fiber content (DM basis) of the treatment diets ranged from 117 to 209 g/kg and 311 to 388 g/kg, respectively. Thirteen treatment diets were formulated according to the Box-Behnken design. During 4 experimental periods of 21 d each, all treatment diets were fed, including a repetition of the center point treatment (50% grass silage, 50:50 F:C, 3% CL) during every period. Intake, production performance, and milk FA profile were measured, and response surface equations were derived for these variables. Shifting from 80% grass silage to 80% corn silage in the diet linearly increased dry matter intake (DMI), net energy for lactation (NE_L) intake, cis-9,cis-12-C18:2 (C18:2n-6) intake, and milk yield, and linearly decreased cis-9,cis-12,cis-15-C18:3 (C18:3n-3) intake and milk fat content. Shifting from a high forage to a high concentrate diet linearly increased DMI, NE_L intake, C18:2n-6 intake, and milk yield, and decreased milk fat content. Supplementation of CL linearly increased C18:3n-3 intake, but had no effect on DMI, NE_L intake, milk yield, or milk fat content. Shifting from 80% grass silage to 80% corn silage linearly increased proportions of trans-10-C18:1 and C18:2n-6 in milk fat, whereas the proportions of trans-11,cis-15-C18:2 and C18:3n-3 linearly decreased. Significant interactions between CL supplementation and F:C were found for proportions of trans-10-C18:1, trans-15-C18:1, cis-15-C18:1, trans-11,cis-15-C18:2, and C18:3n-3 in milk fat, with the highest levels achieved when the diet contained 5% CL and a 35:65 F:C ratio. The effect of supplementing CL on several milk FA proportions, including C18:2n-6 and C18:3n-3, depends significantly on the F:C ratio and forage type in the basal diet.     

Effect of feeding oilseed supplements to dairy cows on ruminal and milk fatty acid composition

The objective of this study was to compare the effects of oilseed‐based supplements, rapeseed and linseed, against a barley‐based control, on the fatty acid composition, and subsequent solid fat ratio, of the milk fat from dairy cows. In addition, as a means of understanding the digestive processes which influence the milk fat composition, ruminal extracts were collected from the cows and analysed for fatty acid composition. Four lactating dairy cows each fitted with a rumen fistula were provided with silage and one of four concentrate diets. The main constituent of the concentrate supplements was either rapeseed (ground or unground), linseed (unground) or a barley control. The diets were offered in accordance with a 4 × 4 Latin square arrangement. The oilseed‐supplemented concentrates provided the cows with 620–640 g fatty acids day^?1. Experimental treatments were provided to the cows for 2 weeks, after which ruminal extracts were collected over a 24 h period and a milk sample was taken. All extracts were analysed for fatty acid composition. The diets fed influenced the long‐chain fatty acid composition of the ruminal extracts and milk fat. The proportion of C18:1n‐9 in the ruminal extracts increased from 202–224 to 282–321 g kg^?1 of the total fatty acids when the cows were provided with the rapeseed‐based diets. The linseed‐based diet increased the C18:1n‐9 proportion of the ruminal extracts from 164 to 218 g kg^?1 of the total fatty acids. Both rapeseed‐based diets also resulted in a higher proportion of C18:0 in the ruminal extract, possibly owing to biohydrogenation of the dietary fatty acids. This proportion of C18:0 in the ruminal extract was lowest immediately after feeding, increasing to a maximum 4–6 h later. Both rapeseed‐based concentrates increased the proportion of C18:1n‐9 in the milk fat to approximately 300 g kg^?1 of the total fatty acids as compared with 214 g kg^?1 for the control. The proportion of C18:1n‐9 in the milk fat from the cows offered the linseed‐based concentrate was 246 g kg^?1 of the total fatty acids. There were also significant decreases in the proportions of C16:0 in the milk fat from the cows offered all oilseed‐based concentrates. There was no difference between the fatty acid compositions of the milk fats from the cows fed the ground or unground rapeseed‐based supplements. The oilseed‐based supplements also resulted in significant decreases in the solid fat content of the milk fat at temperatures ranging from 0 to 35 °C, which would be indicative of a softer, more spreadable butter. © 2002 Society of Chemical Industry     

Effects of grass silage and soybean meal supplementation on milk production and milk fatty acid profiles of grazing dairy cows

The effects of supplementation with grass silage and replacement of some corn in the concentrate with soybean meal (SBM) on milk production, and milk fatty acid (FA) profiles were evaluated in a replicated 4 × 4 Latin square study using 16 dairy cows grazing pasture composed of ryegrass, Kentucky bluegrass, and white clover. Each experimental period lasted for 3 wk. The 4 dietary treatments were PC, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn-based concentrate mixture (96% corn; C); PCSB, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn- and SBM-based concentrate mixture (78% corn and 18% SBM; CSB); SC, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of C concentrate; and SCSB, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of CSB concentrate. The concentrate mixtures were offered twice each day in the milking parlor and were consumed completely. Grass silage supplementation reduced dietary crude protein and concentration of total sugars, and dietary SBM inclusion increased dietary crude protein concentration and decreased dietary starch concentration. Milk yield and energy-corrected milk were increased by SBM supplementation of cows with access to grass silage. Milk protein concentration was lower in cows offered grass silage, regardless of whether SBM was fed. Dietary SBM inclusion tended to increase milk fat concentration. Plasma urea N was reduced by silage feeding and increased by SBM supplementation. Supplementation with grass silage overnight could represent a useful strategy for periods of lower pasture availability. Dietary inclusion of SBM in solely grazing cows had no effects on milk production and composition, exacerbated the inefficient capture of dietary N, and increased diet cost. Grass silage supplementation affected milk FA profiles, increasing both the FA derived from de novo synthesis and those derived from rumen microbial biomass, and decreasing the sum of C18 FA (mostly derived from diet or from mobilization of adipose tissue reserves). Milk fat concentrations of conjugated linoleic acid cis-9, trans-11, vaccenic acid (18:1 trans-11), and linolenic acid (18:3n-3) were unaffected by grass silage supplementation, suggesting that partial replacement of pasture by unwilted grass silage does not compromise the dietary quality of milk fat for humans.     

The effect of dietary forage to concentrate ratio and forage type on milk fatty acid composition and milk fat globule size of lactating cows

We examined the effects of 2 grass silage-based diets differing in forage:concentrate (FC) ratio and those of a red clover silage-based diet on intake, milk production, ruminal fatty acid (FA) biohydrogenation, milk FA composition, and milk fat globule (MFG) size distribution. Ten multiparous Nordic Red cows received the following treatments: grass silage-based diets containing high (70:30, HG) or low (30:70, LG) FC ratio or a red clover silage-based diet with an FC ratio of 50:50 (RC) on a dry matter basis. Determinations of MFG were performed from fresh milk samples without addition of EDTA so the results of fat globules >1 µm in diameter are emphasized instead of the entire globule population. Lower FC ratio in grass silage-based diets increased milk production with no effect on daily fat yield, leading to 13% lower milk fat concentration. The effect of FC ratio on MFG size was moderate. It did not affect the volume-weighted diameter in grass silage-based diets, although LG lowered the volume-surface diameter of MFG in the size class >1 µm compared with HG. Compared with HG, feeding LG moderately decreased the biohydrogenation of 18:2n-6, leading to a higher level of polyunsaturated fatty acids in milk fat. Feeding RC lowered milk fat concentration and daily milk fat yield compared with grass silage-based diets. The volume-weighted diameter of MFG in the size class >1 µm was smaller in RC milk compared with grass silage-based diets. Feeding RC increased the flow of 18:3n-3 at the omasum by 2.4-fold and decreased the apparent ruminal 18:3n-3 biohydrogenation compared with grass silage-based diets despite similar intake of 18:3n-3. It also resulted in the lowest amount of saturated FA and the highest amounts of cis-9 18:1, 18:3n-3, and polyunsaturated FA in milk. In conclusion, LG decreased milk fat content and induced minor changes in MFG size distribution compared with HG, whereas RC lowered milk fat production, altered milk FA composition to nutritionally more beneficial direction, and led to smaller MFG compared with grass silage-based diets.     

Effect of level of oil inclusion in the diet of dairy cows at pasture on animal performance and milk composition and properties

The effect of including additional oil, incorporated as whole rapeseeds, in the diet of 64 Holstein–Friesian dairy cows (32 mid‐ and 32 late‐lactation) at pasture on animal performance and milk fat composition and properties was followed over a continuous trial of 20 weeks duration. Within two stages of lactation (mid, 130 ± 16.2 days, or late, 231 ± 58.9 days), cows were allocated to concentrate treatments representing four levels of rapeseed oil inclusion, 0 (control), 200, 400 and 600 g oil day^?1. Oil inclusion had little effect on milk yield but decreased milk fat content significantly (P < 0.01), with a mean depression of 0.40% at the highest level of oil inclusion. The content of milk protein also decreased with increasing addition of oil, but the decrease was smaller than the milk fat depression and was not statistically significant. Increasing the level of rapeseed oil in the diet to 600 g oil day^?1 resulted in linear changes in milk fat and protein concentrations which were described by regression equations. For each 100 g of rapeseed oil added to the diet, milk fat content decreased by 0.068% in mid‐lactation cows and 0.061% in late‐lactation cows, while protein content decreased by 0.026% in mid‐lactation cows and 0.028% in late‐lactation cows. Total unsaturated fatty acid content of milk fat also increased in a linear fashion with increased level of oil addition, from 345.7 g kg^?1 total fatty acids in control milk fat to 459.3 g kg^?1 total fatty acids at 600 g oil day^?1, while total saturated fatty acids decreased in the same milk fats from 640.7 to 522.2 g kg^?1 total fatty acids. These changes were reflected in lower solid fat contents (SFC) in the milk fat at the lower temperatures of measurement, eg 41% SFC at 5 °C at the highest level of oil inclusion compared with 52% in the control milk fat. However, SFC at 20 °C showed little difference with increasing level of dietary oil addition, an important factor in maintaining product integrity at room temperatures. The relatively high content of the monounsaturated fatty acid C18:1 (345.5 g kg^?1 total fatty acids at 600 g oil day^?1) and low content of polyunsaturated fatty acids (total C18:2 and C18:3 <40 g kg^?1 total fatty acids at 600 g oil day^?1) ensured that the oxidative stability of the treatment and control milk fats did not differ significantly. Stage of lactation had an unexplained effect of consistent magnitude on milk fat composition throughout the trial period, with late‐lactation animals producing milk fats containing a significantly (P < 0.001) higher proportion of unsaturated fatty acids than the mid‐lactation animals. Changes in the proportions of unsaturated fatty acids in milk fat, as reflected by changes in iodine value, were established within 2 weeks of the trial commencing and persisted over the 20 weeks of the trial duration. No adverse effect on animal health from this type of dietary manipulation was identified. Copyright © 2004 Society of Chemical Industry