Increased Milk Protein Yield Research Articles

Effect of Supply of Metabolizable Protein on Splanchnic Fluxes of Nutrients and Hormones in Lactating Dairy Cows

The effect of the supply of metabolizable protein on splanchnic fluxes of nutrients and hormones was measured in six catheterized late-lactation Holstein cows in a crossover design. Two isonitrogenous diets (16.3% CP), but differing in rumen protein degradability and estimated metabolizable protein (MP) supply (1654g/d, Lo-MP; 1930g/d, Hi-MP) were fed, each over a 35-d experimental period. On d 34 or 35, net fluxes of nutrients and hormones across the portal-drained viscera, the liver, and total splanchnic tissues were determined. Portal absorption of total, essential, nonessential, and branched-chain amino acids (AA) increased with the Hi-MP diet. Approximately 76% of the additional metabolizable protein supply was recovered as extra AA-N absorption in the portal vein. Liver removal of AA was not different between diets, and this resulted in a greater net release across the splanchnic tissues for the Hi-MP diet. This extra AA supply provided substrates for the observed increased milk protein yield for the Hi-MP diet. Fractional efficiencies of conversion of absorbed individual essential AA into milk protein ranged from 0.42 to 0.68. The corresponding efficiencies for utilization of postsplanchnic AA supply were 0.42 to 1.80. Provision of methionine, phenylalanine, and histidine beyond the liver were similar to outputs in milk protein but the other essential AA were supplied to peripheral tissues in excess of milk output, indicative of oxidative mechanisms in nonhepatic tissues. Net fluxes of glucose, NH3-N, and urea were not affected by the diets. Neither arterial concentrations of insulin, somatotropin, or IGF-1, nor net transfers across the portal-drained viscera or liver of insulin, were affected by the diets. Although portal release of glucagon was not different between the diets, a smaller proportion was removed by the liver on the Hi-MP diet. Metabolism of AA across the splanchnic tissue bed is a major determinant of the quantity and the profile of AA delivered to peripheral tissues.

Effects of Abomasal Infusions of Histidine, Glucose, and Leucine on Milk Production and Plasma Metabolites of Dairy Cows Fed Grass Silage Diets

Our previous study showed that His was the first-limiting amino acid (AA) for milk protein production in cows fed grass silage and cereal-based supplement. The aim of this study was to identify the second-limiting AA and determine whether glucose was limiting responses to His. Abomasal infusion of His (6.5 g/d), glucose (250 g/d), His (6.5 g/d) + glucose (250 g/d), His 6.5 g/d) + Leu (12 g/d) and His (6.5 g/d) + Leu (12 g/d) + glucose (250 g/d) on milk production and utilization of amino acids by mammary gland was in an incomplete 5 × 6 Latin square design with 14-d periods. The diet was based on restrictively fermented grass silage fed ad libitum and 8 kg/d of concentrate comprised of barley, oats, unmolassed sugar beet pulp, urea, and minerals. The infusions did not affect feed intake, diet digestibility, or rumen fermentation pattern. The molar proportion of propionate in rumen VFA was low (15.5%), suggesting that glucose supply from the basal diet could be limiting. Milk and milk protein yields were increased by His infusion. Infusion of His increased plasma His concentration from 19 to 52 μM but decreased extraction efficiency of His. Infusion of glucose increased plasma glucose concentration, milk lactose concentration, and yield and tended to increase milk protein yield. Responses in milk protein yield to combined infusions of His and glucose were additive, suggesting that the utilization of the first-limiting AA His was limited by glucose supply. Infusion of Leu increased plasma Leu concentration but did not produce any further milk protein yield response compared with the infusions without Leu. It was concluded that the efficiency of utilization of the first-limiting AA His could be improved by increasing the supply of glucose, when the basal diet produces a rumen fermentation pattern low in propionate. Leu was not the second-limiting AA in cows fed grass silage-based diets.

Intramammary Infusion of Insulin or Long R3 Insulin-like Growth Factor-I did not Increase Milk Protein Yield in Dairy Cows

Two experiments investigated the regulation of milk protein synthesis in well-fed cows (n = 4) using 1) a hyperinsulinemic-euglycemic clamp and 2) intramammary infusion of insulin or long R3 insulin-like growth factor-I plus supplementary amino acids. In experiment 1, insulin was infused at 1.0µg · kg BW–1 · h–1 to increase circulating levels fourfold, and euglycemia was maintained by infusion of glucose. An insulin clamp increased the yields of casein and whey protein both with and without supplementary amino acids. Plasma concentrations of insulin-like growth factor-I were increased and insulin-like growth factor binding protein-2 decreased during insulin clamp, while both insulin and insulin-like growth factor-I in milk were elevated by this treatment. Milk concentrations of insulin peaked on day 4, but insulin-like growth factor-I concentrations in milk peaked on day 1 of the insulin clamp. In experiment 2, intramammary infusion of insulin had no effects on any measured variables, while yields of milk, protein, and fat were slightly lower following long R3 insulin-like growth factor-I treatment. This could be associated with an increase in somatic cell count, which occurred following long R3 insulin-like growth factor-I treatment. Results from experiment 1 suggest insulin and insulin-like growth factor-I are likely candidates responsible for the increased milk protein yields during the insulin clamp. However, in experiment 2 neither hormone enhanced milk protein yield when administered using an intramammary technique.

Effects of Insulin and Postruminal Supply of Protein on Use of Amino Acids by the Mammary Gland for Milk Protein Synthesis

We examined the relationships between amino acid supply, net utilization of amino acid by the mammary gland, and milk protein yield, in investigations that utilized a hyperinsulinemic-euglycemic clamp. A two-way crossed factorial design was employed. There were two 12-d periods involving abomasal infusions of either water or a mixture of casein (500 g/d) plus branched-chain amino acids (88 g/d), with a hyperinsulinemic-euglycemic clamp during the last 4 d of each period. During the clamp, insulin was infused at 1.0μg·kg BW–1 ·h–1 to increase circulating levels fourfold, and euglycemia was maintained by infusion of glucose. The insulin clamp treatments increased milk protein yield by 15 and 25% during abomasal infusion of water or casein plus branched-chain amino acids, respectively. Circulating concentrations of essential amino acids were reduced (33%) during insulin clamp treatments, especially branched-chain amino acids (41%). Arteriovenous difference of essential amino acids across the mammary gland was linearly related to their arterial concentrations. However, milk protein yield was not related to either arterial concentration or arteriovenous difference, for any of the essential amino acids. During insulin clamp treatments, the mammary gland was able to support the increased milk protein yields by increasing extraction efficiency of essential amino acids, mammary blood flow, and glucose uptake. Furthermore, a positive mammary balance of total amino nitrogen and carbon was maintained for all treatments. These adaptations demonstrate the unique ability of the mammary gland to adjust local conditions to allow for an adequate nutrient supply.

Supply of nutrients and productive responses in dairy cows given diets based on restrictively fermented silage

The objective of this paper is to review research which has evaluated the feeding of dairy cows with diets containing large proportions of grass silage. In Finland, milk production systems evolved are based on the use of restrictively fermented silages. Higher potential yields, smaller production risks than with cereal grains, short grazing period and high digestibility of grasses grown in northern latitudes have facilitated this development. Factors affecting nutrient supply from these diets are discussed. Digestibility is determined mainly by the stage of maturity at harvesting and it is not markedly affected by the level of energy and protein supplementation. Intake of grass silage is influenced both by digestibility and fermentation characteristics. Efficiency of microbial synthesis is high in animals given diets based on restrictively fermented silage but rumen fermentation pattern is characterised by low molar proportions of propionate. Production responses to additional concentrate are relatively small, especially when the amount of concentrate exceeds 10 kg day-1. High substitution of silage dry matter (DM), negative associative effects on digestion and partitioning of energy towards body tissues account for small production responses. Protein supplementation has consistently increased milk protein yield but responses do not appear to be related to the level of milk production, silage crude protein content, amount of concentrate or stage of lactation. The new protein evaluation system provides an accurate prediction of protein yield with the typical Finnish dairy cow diets. The high slopes (ca. 0.5) between protein supply and milk protein yield within experiments suggest that protein supply is suboptimal and protein supplements are used with a high efficiency.

Milk production and ruminal metabolites from cows offered two pasture diets supplemented with non‐structural carbohydrate

The effects on milk solids production, ruminal metabolites, and microbial protein synthesis of four pasture‐based diets were investigated. Two pastures (high or low nitrogen content (HN, LN) each with and without non‐structural carbohydrate supplementation (+NSC, ‐NSC, at 10% of metabolisable energy intake) were offered to eight stall held, rumen‐fistulated Friesian cows during four 14‐day periods in early to mid lactation in a Latin square design. HN and LN pastures contained 2.8 and 2.1% N, respectively. Total daily dry matter intakes averaged 15.6, 14.5, 15.3, and 14.3 kg on HN+NSC, HN‐NSC, LN+NSC, and LN‐NSC, respectively. NSC supplementation had no effect on milk and milk fat yields but increased milk protein yield by 0.04 kg/ day on HN pasture. Yields of milk, fat, and protein were higher on HN than LN pasture but microbial protein synthesis (MPS, g N/day) was not affected by type of pasture. MPS and efficiency of MPS (g N/kg digestible organic matter intake) were increased by NSC supplementation on HN pasture but not on LN pasture. Ruminal ammonia concentration and total tract N digestibility were reduced by NSC supplementation on both pastures and were lower on LN compared with HN pasture. The results indicated that pasture type affected response to NSC supplementation and that on HN but not LN pasture NSC supplementation improved N utilisation in the rumen and increased milk protein output.

The Role of Insulin in the Regulation of Milk Protein Synthesis in Dairy Cows1,2

We Examined the role of insulin in milk protein synthesis using the hyperinsulinemic-euglycemic clamp approach in combination with abomasal infusion of casein. The two experimental periods consisted of abomasal infusion of water or 0.5 kg/d of casein. An insulin clamp was conducted over the last 4 d of each period. During the insulin clamp, circulating insulin was elevated fourfold, and euglycemia was maintained by the infusion of exogenous glucose. Casein infusion increased milk yield so that milk protein yield was 10% greater than baseline values. Use of the insulin clamp combined with casein infusion increased milk protein yield by 230 g/d (28% greater than baseline values). Milk protein composition was not altered, but content was increased from 3.13% during the baseline period to 3.44% by d 4 of the clamp; calcium concentration in milk increased about 10% to 1.2 g/kg. During the clamp, circulating concentrations of essential amino acids were dramatically reduced. The most pronounced effects were noted for branched-chain amino acids (64% reduction from baseline values). The insulin clamp resulted in alterations in circulating insulin-like growth factor (IGF)-I concentrations (increase) as well as IGF-II and IGF-binding protein-2 concentrations (decreases). Overall, results indicated that the ability of the mammary gland to synthesize milk protein does not function at maximum capacity, and there is a previously unrecognized potential to enhance milk protein percentage and yield.

Effects of Supplementation of Energy or Ruminally Undegraded Protein to Lactating Cows Fed Alfalfa Hay or Silage

Alfalfa was harvested as silage or hay and fed in two 12-wk trials with a 4×4 Latin square design that used 12 (trial 1) or 24 (trial 2) multiparous lactating cows (4 ruminally cannulated cows per trial). Diets contained (dry matter basis) 75 or 50% alfalfa plus 24 or 40% high moisture corn (trial 1) or 50% alfalfa, 44 or 41% high moisture corn, with (3%) or without fish meal (trial 2). Experiments were conducted to evaluate the responses of cows fed alfalfa hay or alfalfa silage diets to an increase in protein supply from microbial protein synthesis (trial 1) or from the supplementation of ruminally undegraded protein (RUP) (trial 2). In trial 1, the increase in high moisture corn in the diet increased both milk protein and microbial crude protein yields (estimated from the excretion of purine derivatives) to a greater extent for the cows fed the alfalfa silage diets (170 and 337 g/d, respectively) than for the cows fed the alfalfa hay diets (100 and 100 g/d, respectively). In trial 2, RUP supplementation (as fish meal) increased milk protein yield 100 g/d for cows fed alfalfa silage diets and 20 g/d for cows fed alfalfa hay diets. These results indicated that protein status was poorer and, thus, more responsive to absorbable protein from microbial protein (trial 1) or RUP (trial 2) for cows that consumed alfalfa conserved as silage versus those that consumed alfalfa conserved as hay.

Response of Lactating Cows to Methionine or Methionine Plus Lysine Added to High Protein Diets Based on Alfalfa and Heated Soybeans

Lactation diets based on wilted alfalfa silage and heated whole soybeans are common in the mid-western US. We examined the milk production response of multiparous Holstein cows to the addition of ruminally protected methionine at two percentages to a basal total mixed ration. An additional total mixed ration included both methionine and lysine supplementation. Sixteen Holstein cows in early lactation were used in a replicated 4 x 4 Latin square design with 21-d periods. Milk production, milk composition, and dry matter intake were determined for the last 5 d of each period. Milk production (41.5 kg/d), dry matter intake (25.9 kg/d), and milk fat concentration (3.26%) were unaffected by the supplementation of amino acids. The addition of methionine increased milk protein concentration and yield linearly. Each gram of methionine increased milk protein yield by 4g, and milk protein concentration increased from 2.89 to 2.99% with the addition of 10.5 g/d of methionine. The proportion of casein N in total milk N was unaffected by treatment. The addition of lysine did not elicit a response. Total mixed rations based on alfalfa haylage, heated soybeans, and animal proteins were clearly limited by their methionine content but were adequate in their lysine content.

Influence of Particle Size on the Effectiveness of Beet Pulp Fiber

Sixteen Holstein cows in midlactation were used in a design based on a replicated 4×4 Latin square with the last period removed to determine the influence of particle size of beet pulp neutral detergent fiber (NDF) on its effectiveness as a replacement for alfalfa NDF. Diets were a low forage, low fiber diet [12.1g of alfalfa NDF/100g of dry matter (DM)], a normal forage diet (low forage plus 7.8g of additional alfalfa NDF/100g of DM), and two low forage diets with 5.3g of NDF/100g of DM from either whole or finely ground dried sugar beet pulp. Replacement of alfalfa fiber with beet pulp fiber increased milk protein yield because of the tendencies toward increased milk yield and protein concentration. However, milk fat concentration and yield were unaffected. The addition of beet pulp fiber, either whole or ground, to the basal low forage, low fiber diet did not affect yields of milk, protein, or fat, but milk protein concentration tended to be lower for cows fed the beet pulp diets than for cows fed the basal diet. Reducing the particle size of beet pulp increased DM intake but did not affect any of the milk yield measurements. Particle size reduction of beet pulp did not reduce its effectiveness as a fiber source as measured by changes in milk fat content.

Alternative nutritional strategies to increase milk yield in dairy cows: a modelling approach

When the ratio between Metabolisable Protein (MP) and Metabolisable Energy (ME) is optimal for a given level of milk output (not constrained by genotype, management or other nutritional factors), further increases in milk output can be obtained by two strategies: Strategy 1. Increased supply of ME and MP (maintaining optimal MP:ME), orStrategy 2. Oversupply of MP (ie MP:ME > optimum)Possible mechanisms underlying Strategy 2 include use of amino acids for gluconeogenesis or oxidation (Oldham, 1994), mobilisation of body energy reserves or, where forage is available ad libitum, increased forage intake (Newbold, 1994). For the purpose of this study, supply of MP above the theoretical optimum was assumed to increase milk protein yield only via the mechanism of increased forage intake.The objective of this study was to evaluate the economic (cost of ration) and environmental (overall efficiency of N use) consequences of increasing milk yield by these two strategies.

Alternative nutritional strategies to increase milk yield in dairy cows: a modelling approach

When the ratio between Metabolisable Protein (MP) and Metabolisable Energy (ME) is optimal for a given level of milk output (not constrained by genotype, management or other nutritional factors), further increases in milk output can be obtained by two strategies: Strategy 1. Increased supply of ME and MP (maintaining optimal MP:ME), orStrategy 2. Oversupply of MP (ie MP:ME > optimum)Possible mechanisms underlying Strategy 2 include use of amino acids for gluconeogenesis or oxidation (Oldham, 1994), mobilisation of body energy reserves or, where forage is available ad libitum, increased forage intake (Newbold, 1994). For the purpose of this study, supply of MP above the theoretical optimum was assumed to increase milk protein yield only via the mechanism of increased forage intake.The objective of this study was to evaluate the economic (cost of ration) and environmental (overall efficiency of N use) consequences of increasing milk yield by these two strategies.

Protein and Fat Metabolism in Cows Given Somavubove Before Parturition

Forty-one Holstein cows were injected with 0, 5, or 14 mg/d of bST for the last 46±6 d before parturition. Compared with data for controls, the 5- and 14-mg doses of bST increased apparent protein synthesis about 16% before parturition. Exogenous bST before parturition increased apparent protein degradation 30% during wk 1 after parturition. During wk 1 of lactation, 14mg of bST also increased milk protein yield 33%. No treatment differences were present in concentration of serum NEFA, body condition score, or thickness of subcutaneous fat. Therefore, administration of bST before parturition did not alter metabolism of subcutaneous fat. Prepartum treatment with 5 and 14mg of bST increased and maintained serum somatotropin at 6.5 and 22.7ng/ml, respectively, compared with 1.6ng/ml in controls. Concentrations of serum IGF-I were initially increased but were not maintained as parturition approached. On d –23, IGF binding protein 3 was increased 65% but was not different among groups by d –7. For groups administered the 5 and 14 mg/d of bST, IGF binding protein 2 was decreased 40%. Administration of bST before parturition increased protein reserves and stimulated milk protein yield for 1 wk but did not alter metabolism of subcutaneous fat. Furthermore, energy balance appeared to be a major regulator of concentrations of IGF binding protein 3 and responsiveness of IGF-I to exogenous somatotropin before parturition.

Effects of feeding fodder beet and concentrates with different protein contents on dairy cows offered silage ad libitum

AbstractIn two changeover design experiments, fifteen early‐ and sixteen late‐lactation cows were used to investigate the effects of offering food beet with ad libitum grass silage and concentrates with different CP content on milk yield and quality. In Experiment 1 (early lactation) cows were offered no fodder beet (0) or 4 kg DM d−1 (4) in conjunction with one of three concentrates containing 159, 191 or 244g CP kg−1 DM (L.M.H.). Treatments were therefore 1L/0, 1L/4, 1M/0, 1M/4, 1H/0 and 1H/4. In Experiment 2 (late lactation) cows were offered the same level of fodder beet in conjunction with two concentrates containing 129 and 229 (L,H) g CP kg−1 DM. Treatments were therefore 2L/0, 2L/4, 2H/0 and 2H/4.In both experiments feeding fodder beet reduced silage DM intakes (P < 0·001) and increased total DM intake (P < 0·05 to P < 0·001). The substitution rate (r) ranged from 0·46 to 0·59kg of silage DM (kg−1 fodder beet DM).In Experiment 1, fodder beet tended to increase milk yield, composition and yield of constituents, but the effect was statistically significant for milk protein content only (P < 0·01). In Experiment 2, milk yields for 2L/0, 2L/4, 2H/0 and 2H/4 were 11·3, 12·1, 11·7 and 12·5 kg d−1 respectively (s.e.d. 0·43, non‐significant), fat contents were 44·4, 47·3, 44·3 and 46·8g fat kg−1 respectively (s.e.d. 0·73, P < 0·001), protein contents were 34·3, 35·6, 35·3 and 36·2 g protein kg−1 respectively (s.e.d. 0·28, P < 0·001), fat yields were 494, 574, 512 and 579 g fat d−1 respectively (s.e.d. 20, P < 0·001) and protein yields were 385, 426, 407 and 442 g protein d−1 (s.e.d. 13, P < 0·01) respectively.Increasing CP in the concentrate significantly increased milk yield in Experiment 1 (23·9, 22·5, 23·5, 23·8, 26·2, 26·5kg d−1 for 1L/0, 1L/4, 1M/0, 1M/4, 1H/0 and 1H/4 respectively, P < 0·05). Higher CP in concentrate also resulted in significantly increased milk protein yield in early‐lactation (P < 0·001) and milk protein content in late‐lactation (P < 0·01) cows. There was a significant interaction between fodder beet and concentrate CP content for milk protein yield (P < 0·001) in Experiment 1.

Soyhulls as a Replacement for Forage Fiber in Diets for Lactating Dairy Cows

Thirty Holstein cows in early and midlactation were fed one of five TMR for 12 wk in which soyhulls replaced 25 or 42% of the forage (alfalfa:corn silages, 1:1, wt/wt, dry basis). Within each amount of soyhull replacement, 33% of the silage was replaced with coarsely chopped alfalfa hay. All diets were isocaloric compared with the control diet, which contained 60% silage and no soyhulls. The high amounts of soyhulls fed with coarsely chopped hay improved DMI, and NDF intake and milk yield by 14, 33, and 9%, respectively, compared with the control diet. Addition of soyhulls at low or high amounts reduced milk fat yield and increased milk protein yield, but addition of hay to the high soyhull diet maintained milk fat yield similar to the control diet. The high soyhull diets increased DM digestibility by 7% compared with the control diet. Rumination time and acetate to propionate ratios were reduced by 43 and 24%, respectively, when high amounts of soyhulls were fed compared with the control diet. Soyhulls can successfully replace 42% of dietary forage when fed in combination with coarsely chopped hay in place of 33% of the dietary silage.

Food intake, milk yield and live-weight gain of dairy cows given increased amounts of calcium-saponified fatty acids of palm acid oil

ABSTRACTA long-term experiment (first 24 weeks of lactation) with Danish Black and White cows and a short-term experiment with Jersey cows (experiment periods of 6 weeks) were carried out. In the long-term experiment, the effect of supplementing a normal dairy ration with 0·5 kg calcium (Ca) soap, 10 kg Ca-soap or 2 kg rolled barley was investigated in two herds, where silage was given ad libitum. The daily intakes of fatty acids in the diets were approximately 625, 1000, 1400 or 650 g respectively. Energy intake increased markedly by the supplementation, but not differently between soap or barley supplementation. The effect on milk production was not consistent in the two herds. In one herd, the soap supplement tended to increase milk fat yield (80 g/day) but not more than the barley supplementation which, in contrast to the fat supplementation, also increased milk protein yield. The effect of the fat was consistent over the first 6 months of lactation. In the other herd, only small differences in milk production were obtained with either supplements. In the short-term experiment carried out in mid lactation, a supplement of 0·8 kg Ca-soap increased daily intake of fatty acids from 730 to 1280 g per cow daily. Total food intake, milk and milk fat yield were not affected by the supplement but milk protein yield and live-weight gain were significantly reduced.

Effects of intrammary arterial infusion of essential amino acids in the lactating goat.

SummaryExperiments were performed on 3 lactating goats, in which mammary arterial plasma amino-acid concentrations were elevated by the infusion of a solution of essential amino-acids into the carotid artery supplying a transplanted mammary gland. In 2 experiments there were marked elevations in the arterial concentrations of most essential amino acids, but in one case only did this result in significantly increased uptake of amino acids by the gland, the arterio-venous difference being significantly correlated with arterial concentration for all except one amino acid. In the experiment in which increased amino-acid uptake was observed, infusion also resulted in a significantly increased milk yield and increased milk protein yield. The results are discussed in relation to data from other laboratories and lead to the suggestion that milk protein synthesis may be limited by the availability of either methionine or tryptophan.

Effects of intrammary arterial infusion of non-essential amino acids and glucose in the lactating goat.

SummaryThree experiments were carried out on 2 lactating goats, in which mammary arterial plasma amino-acid concentrations were elevated by the infusion of a solution of non-essential amino acids into a carotid artery supplying a transplanted mammary gland. In a fourth experiment a solution of glucose was similarly infused. In some cases the increased arterial concentrations of amino acids resulted in their increased mammary uptake, and in a depression of glucose uptake. However, infusions of neither amino acids nor glucose resulted in increased milk protein yield. Infusion of [U-14C]glutamic acid in one experiment demonstrated gluconeogenesis from glutamate carbon within the mammary gland. The results are discussed in relation to data obtained in another laboratory, from which it has been claimed that non-essential amino acid supply may limit milk protein synthesis. The present results provide no confirmation for the claim.