The influence of a formulated excess of rumen degradable protein or undegradable protein on milk production in dairy cows in early lactation

The effects of protein and energy content of compound supplements offered at low levels to October-calving dairy cows given grass silage ad libitum

Ninety-six October calving, multiparous Friesian dairy cows were given from week 2 of lactation perennial ryegrass silage ad libitum, supplemented with one of four compound foods, offered at a flat rate of 3 kg/day. The compound foods differed in crude protein (CP) concentration (210 (LP) and 350 (HP) g/kg dry matter (DM)), achieved by including fish meal at 50 and 250 kg/t respectively; and in metabolizable energy (ME) concentration (12·8 (LE) and 14·0 (HE) M/kg DM), achieved by adding protected fat (approx. 100 kg/t). There were no significant interactions between supplement type in terms of animal performance. Over an average feeding period of 152 days, milk yields were significantly increased by 0·49 kg/day per 100 g supplementary CP (P < 0·01) and 0·50 kg/day per MJ of supplementary ME (P < 0·05).

Increasing the level of supplementary CP had no effect on milk composition but significantly increased yield of milk protein (67 g/day). An increase in supplementary ME significantly reduced protein concentration in the milk (1·1 gjkg) but had no effect on protein yield. Yield of milk fat was significantly increased (76 g/day). The additional energy also significantly improved cow fertility in terms of a reduced interval from calving to both first service and conception.

The interaction between dietary fibre level and protein degradability in dairy cows

A trial was performed to investigate the interaction between energy and protein source for cows in negative energy balance. Six cows were assigned to each of four types of concentrate (metabolizable energy (ME) 12 MJ/kg dry matter (DM), crude protein (CP) 180 g/kg DM) with low or high fibre contents (LF or HF) and protein degradability (LD or HD). For groups HDLF, LDLF, HDHF and LDHF respectively, acid-detergent fibre contents (g/kg diet DM) were 69·2, 66·1, 117·5 and 113·3; protein degradability values were determined as 0·78, 0·61, 0·72 and 0·66. Low-fibre diets were given at the rate of 11 kg/day concentrates with 6 kg/day hay (ME 8 MJ/kg DM, CP 84·5 g/kg DM) and high-fibre diets at the rate of 10 kg/day concentrates with 7·5 kg/day hay from weeks 4 to 13 of lactation. Cows were given a standard diet over the first 3 weeks of lactation and performance in week 3 was used as a covariate.

Milk yield was not affected by treatment but the butterfat content of milk from cows given the high-fibre diets (44·9 g/kg) was higher than the low-fibre diets (36·4 g/kg; P < 0·01), which resulted in significant differences in fat-corrected milk yield (HDHF: 25·1, LDHF: 26·2, HDLF: 22·7, LDLF: 21·5, s.e.d. 1·5 kg/day). ME balance was lower for the LDHF group (−4·1 MJ/day) than for groups LDLF and HDLF (-15·4 and -16·8 MJ/day; P < 0·05) but was not significantly different from the HDHF group (-29·4 MJ/day). Undegradable protein (UDP) balances were 53·4, 93·8, -21·2 and 193·8 (s.e.d. 45, P < 005) g/day for groups HDLF, LDLF, HDHF and LDHF respectively. Differences from zero in ME and UDP balance were accounted for in all groups except LDHF by changes in live weight plus a systematic correction of approximately 10 MJ/day. It is considered that the cows given high-fibre diets responded to high UDP by increasing fat-corrected milk production but mobilization of body fat to support this increase was accompanied by retention of protein with associated water, resulting in very little change in live weight. It is also probable that the high UDP levels improved the digestion of fibre i n the rumen, but this is unlikely to have been sufficient to have accounted for all of the response.

Prediction of the yields of milk constituents in dairy cows offered silage ad libitum and concentrates at a flat rate

Individually recorded milk yields, yields and concentrations of milk components, food intakes and live weights of multiparous dairy cows given silage ad libitum and concentrates at a flat rate in weeks 4 to 13 of lactation and data for silage and concentrate composition from experiments conducted at four sites, were used to obtain simple correlations and multiple linear regressions of yields and concentrations of milk constituents on other variables.

Simple correlations between yields and concentrations and other variables were low. Yield terms were most highly correlated with intake terms. Milk fat concentration was most highly correlated with silage fibre concentration. Milk protein concentration was most highly correlated with digestible energy intake. The best multiple regression models including time effects accounted proportionately for 0·35 of the variation in fat yield, 0·51 in protein yield, 0·55 in lactose yield, 0·39 in total milk yield, 0·19 in fat concentration, 043 in protein concentration and 0·19 in lactose concentration. Most of these models included terms for silage intake and cow live weight which are not generally available on farms. More practical models including fewer independent variates were therefore produced. These models accounted proportionately for 0·33 of the variation in fat yield, 048 in protein yield, 0·50 in lactose yield, 0·32 in total milk yield, 0·19 in fat concentration, 0·40 in protein concentration and 0·17 in lactose concentration.

Milk production in early lactation dairy cows given grass silagead libitum: Influence of concentrate energy source, crude protein content and level of concentrate allowance

There is increasing interest in how the raw material make-up of concentrates can influence the milk performance of dairy cows. Thus, over two consecutive winters, 54 dairy cows were used to investigate the effects on dry matter (DM) intake, milk yield and its composition of feeding concentrates of diverse energy source (LNDF — 131 g neutral-detergent fibre per kg DM, 492 g starch plus sugars per kg DM; HNDF — 244 g neutral-detergent fibre per kg DM, 293 g starch plus sugar per kg DM) at two formulated crude protein (CP) levels (157v.187 g/kg DM) and three levels of concentrate allowance (9, 11, 13 kg DM). The concentrates were formulated to be of equivalent metabolizable energy concentration (MJ/kg DM) and were offered with silagead libitumfor a 10-week period (weeks 4 to 13 of lactation).

Silage intakes were variable but not significantly influenced by concentrate energy source or formulated CP level, except in the 1st year where animals consuming the high CP concentrate ate more silage. Silage DM intake decreased as concentrate allowance was increased with the substitution rate (kg silage DM per kg concentrate DM) increasing as concentrate allowance was increased.

Increasing the concentrate allowance effected the expected increases in milk yield. Concentrate energy source did not influence milk yield but the higher CP levels effected a 2-kg increase in milk yield. Feeding of LNDF concentrates depressed milk fat concentration and its yield, the depression being accentuated with each increase in concentrate allowance. The depression in milk fat concentration was negatively correlated with the forage: concentrate ratio of the diet consumed. Furthermore, dietary NDF proportion was shown to account for greater than half of the variation in milk fat concentration. In contrast to the observations made for milk fat, feeding the LNDF concentrates effected an increase in milk protein concentration but only at the lower CP level of the concentrate.

Prediction of voluntary intake of grass silages by lactating cows offered concentrates at a flat rate

Data for individually recorded silage dry-matter intake (SDMI), concentrate dry-matter intake (CDMI), live weight, milk yield and milk composition of lactating dairy cows offered silage ad libitum and concentrates on a flat-rate basis, together with data for silage composition from experiments conducted at four sites, were used to obtain simple and multiple regressions of SDMI on other variables.

Simple regressions showed that the most important variables affecting SDMI were, in order of importance: silage ammonia nitrogen, fat yield, CDMI, silage digestible organic matter concentration (DOMD) and live weight. The best multiple regression for the mean SDMI over weeks 4 to 13 of lactation accounted for proportionately 0·649 of the variation. Examination of week by week data for weeks 3 to 20 of lactation showed that two models for early and mid lactation were required to give a reasonable pattern of residual variances. These models accounted for 0·627 and 0·581 of the variation respectively. It was necessary to fit time effects explicitly in early lactation. Live weight was best represented by fitting post-calving live weight and deviations from post-calving live weight separately. A number of models requiring fewer input variables were also obtained to allow for use in situations where the full range of measurements is not made.

The new models were tested using independent data from three sites. They performed better than a number of previously published models but the best model still gave a prediction error of proportionately 0·17 about the mean actual silage intake in early lactation and 015 in late lactation.

The results suggest that there is little to be gained from further refinement of the functional form of the models and that the construction of a number of models for specific food and management situations is preferable to the use of global models.

Impacts of the source and amount of crude protein on the intestinal supply of nitrogen fractions and performance of dairy cows

The objective of this article was to review and summarize the significance of the amount and source of dietary crude protein supplements on the supply of nitrogen fractions passing to the small intestine and the performance of lactating dairy cows. A meta-analysis was used to evaluate 2 data sets, one for nitrogen flow to the small intestine and one for performance of cows. The response of dairy cows to rumen-undegradable protein supplements is variable. A portion of this variable response from research trials is explained by the source of crude protein in the control diet, the proportion and source of rumen-undegradable protein in the experimental diet, the effect of rumen-undegradable protein on microbial protein outflow from the rumen, the degradability and amino acid content of the rumen-undegradable protein, and the crude protein percentage of the diet. Compared with soybean meal, the mean milk production responses to feeding rumen-undegradable protein supplements ranged from -2.5 to +2.75%. Because of the large variation and small magnitude of response when rumen-undegradable protein supplements are fed compared with soybean meal, efficiency of nitrogen utilization and the cost to benefit ratio for these crude protein supplements may determine the source and amount of crude protein to feed to dairy cows in the future.

Heat- and Lignosulfonate-Treated Canola Meal as a Source of Ruminal Undegradable Protein for Lactating Dairy Cows

This experiment used 18 lactating Holstein cows in a 3 x 3 Latin square replicated 6 times to determine the effectiveness of processing with moist heat or moist heat combined with lignosulfonate (LSO3) for increasing the ruminal undegradable fraction of canola meal for use as a protein supplement for lactating dairy cows. Diets were formulated to be isonitrogenous and contained one of 3 forms of canola meal; untreated canola meal (UCM), heat-treated canola meal (HTCM) or heat-and LSO3-treated canola meal (LSO3CM). Total collection of urine and feces was taken from each cow during the last 5 d of each 42-d experimental period. Milk production was greater for cows fed the LSO3CM diet (36.6 kg/d) than for cows fed the UCM diet (34.8 kg/d) but did not differ from cows fed the HTCM diet (35.3 kg/d). Digestibility of crude protein was lower for cows supplemented with LSO3CM and they had reduced concentrations of ruminal ammonia N, blood urea N, and milk urea N compared with cows supplemented with UCM or HTCM. Dry matter intake and apparent digestibilities of neutral and acid detergent fiber were increased in cows fed the LSO3CM diet. Urinary N excretion (as % of N intake) was reduced in cows fed the LSO3CM diet. These results indicate that moist heat combined with LSO3 treatment of canola meal was effective in increasing the proportion of crude protein digested in the lower digestive tract of lactating cows and was therefore used more effectively as a source of protein than UCM or HTCM.

Effect of protein source on amino acid supply, milk production, and metabolism of plasma nutrients in dairy cows fed grass silage

This study conducted according to a 4 x 4 Latin square with 28 d periods and four ruminally cannulated Finnish Ayrshire cows investigated the effect of protein supplements differing in amino acid (AA) profile and rumen undegradable protein content on postruminal AA supply and milk production. Mammary metabolism of plasma AA and other nutrients were also studied. The basal diet (Control; 13.4% crude protein) consisted of grass silage and barley in a ratio of 55:45 on a dry matter basis. The other three isonitrogenous diets (17.0% crude protein) were control + fishmeal (FM), control + soybean meal (SBM), and control + corn gluten meal (CGM). The protein supplements replaced portions of dry matter of the control diet maintaining the silage to barley ratio constant for all diets. Dry matter intake was limited to 95% of the preexperimental ad libitum intake and was similar (mean 19.8 kg/d dry matter) across the diets. Protein supplements increased milk, lactose, and protein yields but did not affect yields of energy-corrected milk or milk fat. Milk protein yield response was numerically lowest for diet SBM. Protein supplements increased milk protein concentration but decreased milk fat and lactose concentrations. Microbial protein synthesis and rumen fermentation parameters were similar across the diets, except for an increased rumen ammonia concentration for diets supplemented with protein feeds. Protein supplements increased N intake, ruminal organic matter and N, and total tract organic matter, N, and neutral detergent fiber digestibilities. Protein supplements also increased N and AA flows into the omasum, with SBM giving the lowest and CGM the highest flows. This was associated with an unchanged microbial N flow and a higher undegraded dietary N flow. The omasal flows of individual AA reflected differences in total N flow and AA profile of the experimental diets. Differences in AA flows did not always reflect plasma AA concentrations. The results indicated that AA supply of dairy cows fed a grass silage-cereal diet can be manipulated using protein supplements differing in ruminal protein degradability and AA profile. Lower milk production response to SBM than that to FM and CGM appeared to be related mainly to lower N and AA supplies arising from a high ruminal protein degradability of SBM. Histidine appeared to be the first limiting AA for milk protein synthesis on the control diet. Mammary gland may regulate AA uptake according to requirements.

Effects of rumen-undegradable protein on dairy cow performance: a 12-year literature review

In order to integrate and analyze knowledge on the use of protein supplements and protein nutrition of lactating dairy cows, we compiled a review of 108 studies published throughout the world, but principally in the Journal of Dairy Science between 1985 and 1997. In 29 comparisons from 15 metabolism trials, soybean meal was replaced by high amounts of rumen undegradable protein (RUP) as a supplement; the benefits were not consistently observed for flow to the duodenum, essential amino acids, or lysine and methionine. High RUP diets resulted in decreased microbial protein synthesis in 76% of the comparisons. However, fish meal provided a good balance of lysine and methionine when calculated as a percentage of total essential amino acids. In 127 comparisons from 88 lactation trials that were published from 1985 to 1997, researchers studied the effects of replacing soybean meal with high RUP sources, such as heated and chemically treated soybean meal, corn gluten meal, distillers grains, brewers grains, blood meal, meat and bone meal, feather meal, or blends of these sources; milk yield was significantly higher in only 17% of the comparisons. Fish meal and treated soybean meal accounted for most of the positive effects on milk yield from RUP; corn gluten meal resulted in mostly negative results. The percentage of fat in milk was depressed more by fish meal than by other RUP sources. Protein percentage was decreased in 28 comparisons and increased in only 6 comparisons, probably reflecting the decrease in microbial protein synthesis, as was observed for diets high in RUP. The data strongly suggest that increased RUP per se in dairy cow diets, which often results in a decrease in RDP and a change in absorbed AA profiles, does not consistently improve lactational performance.

Effects of rumen-undegradable protein and feed intake on nitrogen balance and milk protein production in dairy cows

An experiment was designed to determine the response of milk protein production and N utilization in dairy cows to supplementation of a predominantly rumen-undegradable protein (RUP) mixture with a fixed amino acid (AA) pattern and the response to the amount of feed intake. The experiment was designed as a 6 x 6 Latin square with a 3 x 2 factorial arrangement of treatments. The factors were three concentrations of RUP supplement (4.5, 14.9, and 29.1% of dry matter intake) and two levels of feed intake restriction (10 and 20%) of the basal diet. The supplement was designed to approximate a postruminal AA pattern that was similar to bovine caseins for Met, Lys, Phe, His, and Thr. Measurements were made during the last 5 d of each 21-d period. Milk protein production responded linearly as the concentration of RUP supplement in the treatment diet increased within the given range. The difference in feed intake restriction did not affect milk protein production. Efficiency of N utilization for milk production exceeded 30% for cows fed the lowest RUP supplement. Results indicated that there is an opportunity to increase milk protein production by using RUP formulations that are balanced for AA while minimizing waste N excretion.

Effect of ruminant grade Menhaden fish meal on reproductive and productive performance of lactating dairy cows

Menhaden fish meal, fed at 0.7 kg/d [2.7% of dietary dry matter (DM)], replaced blood meal and meat and bone meal (2.0% of dietary DM) in the diet fed at dairy A (n = 341) and replaced blood, meat and bone, and corn gluten meals (3.2% of dietary DM) in the diet fed at dairy B (n = 300). Cows consumed the experimental total mixed diets from approximately 24 to 109 d postpartum. Cows were synchronized for estrus using injections of GnRH agonist at 51 d postpartum. PGF2 alpha 7 d later, and artificial insemination at detected estrus. Resynchronization occurred using the same program if estrus was not detected. Diet failed to alter reproductive responses at synchronized artificial insemination. Pregnancy rate at 120 d postpartum was not altered by diet at dairy A (65.4% vs. 60.2%) but was improved by dietary fish meal at dairy B (31.9% vs. 41.3%; interaction of dairy and diet). The dynamics of corpus luteum regression were altered in cows fed fish meal at dairy B. Dietary fish meal did not influence milk production of cows at dairy A but increased production of milk (2.3 kg/d) and protein (0.1 kg/d) of second parity cows at dairy B. When dietary fish meal was fed to cows at dairy B, production of milk fat and 4% FCM was higher for cows in parity 5 or greater than that for cows in fourth parity.

Response of early lactation cows to ruminally undegradable protein in the diet

The objective of this study was to determine the response of dairy cows in early lactation to diets based on the recommendations of the Agricultural Research Council or the NRC for sustaining milk yield. Diets were formulated to satisfy the nutrient requirements of Holstein cows weighing 600 kg and yielding 35 kg of 3.5% fat milk/d according to either Agricultural Research Council recommendations or NRC recommendations for RUP. A third diet was a 1:1 (wt/wt) mixture of the Agricultural Research Council and the NRC diets. The same forage was fed in all diets at a forage to concentrate ratio of 40:60, and the RUP supply was altered by substituting fish and corn gluten meal for canola meal. The calculated effective degradabilities of CP for the TMR were 70.1, 66.1, and 62.1% for the Agricultural Research Council diet, the mixture of Agricultural Research Council and NRC diets, and the NRC diet, respectively. Milk composition was similar for the three dietary treatments. Multiparous cows showed a linear yield response (30.4, 31.6, and 33.7 kg/d) to increasing inclusion of the NRC concentrate in the diet. No response to additional RUP was observed for first lactation heifers. Agricultural Research Council recommendations for dietary RUP underestimated the requirements for multiparous cows in early lactation yielding > 25 kg of milk/d.

Effects of ruminal versus duodenal dosing of fish meal on ruminal fermentation and milk composition

Three midlactation Holstein cows with ruminal and duodenal cannulas were used in a 3 x 3 Latin square design to determine whether ruminal or postruminal alterations in metabolism were responsible for the changes in milk composition that frequently are associated with dietary fish meal. Cows were offered a diet of 60:40 forage to concentrate (aliquots at 6-h intervals) that was supplemented with isonitrogenous amounts of soybean meal (1.3 kg of DM/d) dosed into the rumen or fish meal (1.0 kg DM/d) dosed either into the rumen or into the duodenum. The DMI, ruminal NDF digestion, and flows of total N and microbial N to the duodenum decreased for cows receiving fish meal. Dietary N flow increased when fish meal was dosed into the rumen. Total concentration of ruminal VFA was greater for cows receiving the soybean meal treatment; however, treatment had no effect on the ratio of ruminal acetate plus butyrate to propionate. Milk and FCM yields were unaffected by treatment, but milk fat content decreased, and milk protein content increased when cows were supplemented with fish meal. The difference in mammary arteriovenous glucose difference decreased when cows were dosed with fish meal. Changes in plasma NEFA and triglycerides were small and inconsistent. Results from this experiment suggest that effects of fish meal on milk composition are due to postruminal alterations in metabolism.

Fecal consistency as related to dietary composition in lactating Holstein cows

A trial was designed to study the relationships of dietary fiber and protein percentage and source to fecal consistency in lactating cattle. Thirty Holstein cows were assigned randomly to one of six TMR through four 21-d periods. The TMR were formulated to contain 17 or 25% ADF and CP of 15 or 22% with soybean meal supplementation or 22% with a combination of corn gluten and soybean meals. Two forage combinations were corn silage with or without alfalfa. Fecal consistency was evaluated using a four-point visual observation scale. Lower dietary fiber reduced fecal pH, score, NDF, and ADF but increased fecal DM and starch. A higher percentage of soybean meal lowered fecal DM and fecal score. Forage source affected fecal DM, NDF, ADF, and starch, but not pH or score. Prediction of fecal score from dietary components and cow parameters resulted in dietary DM percentage and 4% FCM as the most related variables. Accurate prediction of fecal consistency score from dietary and cow parameters was not possible.

Effects of feeding fish meal to cows on digestibility, milk production, and milk composition

Holstein cows in early lactation, producing about 30 kg/d of milk, were fed high energy diets containing 5% Megalac. Three protein treatments, soybean meal diet (16% CP), fish meal diet (16% CP), and soybean meal-fish meal diet (20% CP) were compared in a change-over design. Digestibilities of DM, gross energy, CP, and ADF were not affected significantly by protein treatments. The fish meal diet decreased DMI but increased milk and SCM production compared with the soybean meal diet. Daily production of milk, SCM, and milk components (fat, protein, and lactose) were highest and BW gain lowest for the high protein soybean meal-fish meal diet. The fish meal and soybean meal-fish meal diets increased fat percentage but decreased lactose percentage of milk compared with soybean meal diet. This suggests that, for each diet, the energy supply was adequate, and the observed changes were the effects of protein (i.e., AA) supply to the cows. Thus, there seems to be good reason to feed a good quality undegradable protein like fish meal to cows producing more than 30 kg/d of milk.

Effect of grain level and protein source on ruminal fermentation, degradability, and digestion in milking cows fed silage

Five primiparous Holstein cows (483 kg BW) of low productivity were used in a 4 x 5 incomplete Latin square design to study the effects of feeding two levels of grain containing soybean meal and one level of grain containing fish meal on feed intake, milk production, digestibility, and rumen fermentation. Animals all were fed alfalfa silage for ad libitum intake. Collection of data was between wk 11 and 24 of lactation. The four treatments were an all silage diet (control), silage and medium concentrate fed at 1.8% BW containing soybean meal, and silage and low concentrate fed at 1.3% BW containing either soybean meal or fish meal. Treatments other than control were designed to give similar CP intake from the concentrate, which was based on high moisture corn and cob meal. Milk production and composition were similar among treatments except for fat percentage, which was significantly lower for low grain soybean meal. Intake of DM was higher on medium grain soybean meal compared with the other treatments. Average BW and change in BW (.11 kg/d) were not affected by treatments. Digestibility of DM was higher for cows fed grain (68 to 73%) than for those fed the control diet (60%). Generally, feeding concentrate at 1.3 or 1.8% BW and supplementing with soybean meal or fish meal resulted in pH and concentrations of NH3 N and VFA similar to those observed on the all silage diet. Feeding concentrate at 1.3 or 1.8% BW and supplying fish meal or soybean meal did not change feed utilization enough to increase milk production in low producing cows compared with an all silage diet.

Effects of grain level and protein source on yield, feed intake, and blood traits of lactating cows fed alfalfa silage

Multiparous Holstein cows (n = 27) averaging 590 kg BW were allotted at 3 wk postpartum to nine trios blocked on the basis of similar calving date. Animals were fed alfalfa silage for ad libitum intake and remained in the experiment until wk 11 of lactation. Cows within each trio were assigned randomly to either a medium level of concentrate fed at 1.8% BW containing soybean meal or a low level of concentrate fed at 1.3% BW containing either soybean meal or fish meal. The three treatments were designed to give similar CP intake as percentage of BW from the concentrate. Intake of DM and milk yield were measured daily, and BW and milk composition were recorded weekly. Blood was sampled during wk 7 of lactation. Total DMI was higher for cows fed concentrate at 1.8% BW than for those fed at 1.3% BW. Silage DMI was similar across treatments and averaged 2.17% BW. Milk production, 32.0 kg/d, and milk composition, 3.95% fat, 2.90% protein, and 5.07% lactose, were similar for all treatments. Cows fed at 1.8% BW gained 11.0 kg, whereas those fed at 1.3% BW lost 8.4 and 7.4 kg, respectively, when given soybean meal or fish meal, but these differences were not significant. Prefeeding plasma concentrations of NEFA were higher for cows fed fish meal, which was related to their greater weight lost at wk 7 of lactation compared with those fed soybean meal. Level of concentrate and protein of low or high rumen degradability resulted in similar milk production for cows averaging 32.0 kg/d during early lactation.

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.

Effects of fish meals on rumen bacterial fermentation in continuous culture

Effects of various forms of fish meal on microbial metabolism were investigated in continuous cultures of rumen contents. Five diets were formulated to contain 12% ruminally degradable protein and 47 to 48% nonstructural carbohydrate. Soybean meal was the major protein source in the control diet, whereas in the other four diets, various fish meals were substituted for 6% of total diet DM. Fish meals were: fish meal containing 34.4% FFA, fish meal containing 34.4% FFA with CaCl2 added, fish meal containing 65.6% FFA, and fish meal defatted using 1:1 ethanol:ether extraction. The five treatments were fermented with pH either held constant at 6.2 or not controlled. When pH was maintained at 6.2, the inclusion of any fish meal except defatted fish meal reduced the acetate:propionate ratio, decreased protein digestion, and reduced microbial N produced/per kilogram DM digested when compared with the soybean control. When not controlled, pH decreased after feeding to 6.0 or lower. Under these conditions, the soybean control had a lower acetate:propionate ratio and lower NDF digestion than all diets containing fish meal. In this study, oil-containing fish meal affected microbial metabolism more negatively when the fermentation pH was held at 6.2 than when the pH was 6.0 or lower.