Effects of a ruminally protected B-vitamin supplement on milk yield and composition of lactating dairy cows

It is not clear if B vitamins supplied to the small intestine of dairy cows from dietary and rumen microbial sources are provided in sufficient quantity to maximize animal performance. Our objective was to determine effects of adding a ruminally protected B vitamin blend supplement, containing biotin, folic acid, pantothenic acid and pyridoxine, to the diet of high producing dairy cows on their productivity. Two dairy facilities located in California (USA) were used, one with mid lactation Holstein cows (Experiment 1) and the other with early lactation Holstein cows (Experiment 2). In each Experiment, cows were randomly assigned to treatment in a 2 × 2 crossover design with 28 d (Experiment 1) or 35 d (Experiment 2) experimental periods. In Experiment 1, milk and milk fat yield were unaffected by treatment, although milk fat proportion was lower (37.1 versus 36.3 g/kg; P<0.01), but milk protein yield was higher (1.21 versus 1.24 kg/d; P=0.02) in cows fed B vitamins. In Experiment 2, milk (39.60 versus 40.46 kg/d; P=0.02), milk fat (1.40 versus 1.47 kg/d; P<0.01) and milk protein yield (1.10 versus 1.16 kg/d; P<0.01), as well as milk energy output (113.2 versus 117.8 MJ/d; P<0.01) were all higher with B vitamin feeding. Body condition score (BCS) increased more with B vitamin feeding in Experiment 2, but was unaffected in Experiment 1. Body locomotion score (BLS) increased with B vitamin feeding in both experiments (P=0.01 and < 0.01, respectively), possibly an indication of reduced locomotory ability. Overall, productivity of high producing lactating dairy cows responded positively to feeding a mixture of ruminally protected B vitamins, although differences in the extent of the positive responses between experiments perhaps suggests that early lactation cows, with lower DM intake to milk yield ratios, may be more responsive to ruminally protected B vitamins than mid lactation cows, with higher DM intake to milk yield ratios.     

Effects of silage digestibility on intake and body reserves of dry cows and performance in the first part of the next lactation

This experiment evaluated different strategies for allocating first-cut grass silages to dry dairy cows that had low body-condition score (BCS) at drying off. A total of 48 moderately yielding Holstein-Friesian cows were used, receiving one of three dietary treatments in the dry period and a single lactation diet based on a flat-rate of concentrates and grass silage ad libitum. Throughout the dry period, one group received a low-digestibility silage (harvested 15 June 1998; LL; metabolisable energy (ME) = 10.3 MJ/kg dry matter (DM)) and a second group received a high-digestibility silage (harvested 9 May 1998, HH; ME = 11.7 MJ/kg DM). A third strategy (LH) offered the low-digestibility silage in the early dry period and the high-digestibility silage in the final 3 weeks before calving. The silages had very different crude protein concentrations (144 and 201 g/kg DM) and intakes were widely divergent (10.1 v. 13.5 kg DM/day) across the dry period. No concentrates were fed during the dry period. Silage quality had a very large effect on liveweight change, with treatment means of 0.32 and 1.75 kg/day for LL and HH, respectively. BCS changes followed a similar pattern, though no cows became over-conditioned and blood metabolites were within normal ranges. Increased silage digestibility in the late dry period led to a substantial increase in milk fat concentration and a smaller increase in milk protein concentration, the latter confined to the first full week of lactation. Depression of milk fat appears related to low blood glucose when dry cows in low body condition are fed at a low level. The LH strategy avoided the tendency for lower milk yields and fat concentration that resulted from feeding the low-digestibility silage until calving. This strategy also avoided the higher calf weights that resulted from feeding the high-digestibility silage in the early dry period.     

The potential interaction between body condition score at calving and dietary starch content on productive and reproductive performance of early-lactating dairy cows

Improving reproductive performance is one of the most important factors affecting the profitability of dairy herds. This study investigated the effect of feeding a high starch (HS) diet and body condition score (BCS) at calving on blood metabolites, fertility and ovarian function and milk production in Holstein dairy cows. One hundred seventy-four multiparous cows were fed common close-up and early lactation diets during the first 15 days in milk (DIM). Cows were randomly assigned to 1 of 2 experimental diets from 16 until 50 DIM (n = 87 per group); normal starch (228 g/kg diet DM; NS) or HS (270 g/kg diet DM; HS) diets. Each treatment group was further subdivided based on BCS at calving as normal BCS (BCS ⩽ 3.5; normal BCS (NBCS); n = 45) or high BCS (HBCS) (BCS ⩾ 3.75; HBCS; n = 42). A significant difference was detected for increased milk production (47.24 v. 44.55 kg/day) and decreased milk fat (33.93 v. 36.33 g/kg) in cows fed HS or NS, respectively. Plasma glucose and insulin concentrations were significantly higher in cows fed the HS compared to the NS diet. Diets significantly affected DIM at first artificial insemination (AI, 79.51 ± 3.83 v. 90.40 ± 3.83 days for cows fed HS and NS diets, respectively). High BCS groups had greater milk fat content and elevated plasma nonesterified fatty acids (NEFA), β hydroxybutyrate (BHB) and bilirubin concentrations. In general, feeding higher starch diets to normal BCS cows during the first 50 DIM improved productive and reproductive performance of early-lactating dairy cows.     

Body condition score and live-weight effects on milk production in Irish Holstein-Friesian dairy cows

The objective of the present study was to quantify the relationships among body condition score (BCS; scale 1 to 5), live weight (WT) and milk production in Irish Holstein-Friesian spring calving dairy cows. Data were from 66 commercial dairy herds during the years 1999 and 2000. The data consisted of up to 9886 lactations with records for BCS or WT at least once pre-calving, or at calving, nadir or 60 days post-calving. Change in BCS and WT was also calculated between time periods. Mixed models with cow included as a random effect were used to quantify the effect of BCS and WT, as well as change in each trait, on milk yield, milk fat concentration and milk protein concentration. Significant and sometimes curvilinear associations were observed among BCS at calving or nadir and milk production. Total 305-day milk yield was greatest in cows calving at a BCS of 4.25 units. However, cows calving at a BCS of 3.50 units produced only 68 kg less milk than cows calving at a BCS of 4.25 units while cows calving at 3.25 or 3.00 BCS units produced a further 50 and 114 kg less, respectively. Cows that lost more condition in early lactation produced more milk of greater fat and protein concentration, although the trend reversed in cows that lost large amounts of condition post-calving. Milk yield increased with WT although the marginal effect decreased as cows got heavier. Milk fat and protein concentration in early lactation also increased with WT pre-calving, calving and nadir, although WT did not significantly affect average lactation milk fat concentration.     

Variation in the Composition of Milk of Asian Elephants (Elephas maximus) Throughout Lactation

We investigated milk nutrient composition from three Asian elephant cows over the first 3 years of lactation, including two consecutive lactations in one cow. Body mass gain is presented for three calves during the first year. Milk samples (n = 74) were analyzed for dry matter (DM), fat, crude protein (CP), sugar, ash, calcium (Ca), phosphorus (P), and potassium (K); gross energy (GE) was calculated. Concentrations of most nutrients changed over lactation: DM, fat, CP, Ca, P, and GE were positively correlated to calf age; sugar was negatively correlated to calf age. GE doubled between birth (1 kcal/g) and 2 years of age (2 kcal/g). After accounting for calf age, GE, fat, Ca, and P concentrations differed among the cows. Milk composition also differed between two lactations from the same cow. When milk nutrients were expressed on a mg per kcal basis, the pattern changes: CP, Ca, and P remained relatively constant over lactation on a per energy basis. Calf mass quadrupled over the first year of life; mass gain was linear at 0.9 kg/day. Asian elephant milk composition is variable, both across lactations and between cows, complicating efforts to determine representative values for comparative studies and for the formulation of elephant milk formulas. The fact that CP, Ca, and P were all relatively constant when expressed on a per energy basis may be of biological significance. The increase in nutrient density over lactation undoubtedly limits maternal water loss, reducing the volume of milk necessary to support the calf. Zoo Biol 32:291–298, 2013. © 2012 Wiley Periodicals, Inc.     

Effects of soybean oil supplementation on performance,digestion and metabolism of early lactation dairy cows fed sugarcane-based diets

Sugarcane is an important forage source for dairy cows in tropical countries. However, it provides limited digestible fiber and energy intake, and fat supplementation can be a way to increase energy density and decrease dietary, non-fiber carbohydrates concentrations. We aimed to evaluate the performance, digestion and metabolism of dairy cows in early lactation fed different concentrations of soybean oil (SBO) in sugarcane-based diets. Fourteen primiparous (545±17.2 kg of BW) and eight multiparous (629±26.7 kg BW) Holstein dairy cows were used according to a randomized block design. After calving, diets were randomly assigned to cows within the two parity groups. Diets were formulated with increasing concentrations of SBO (g/kg dry matter (DM)): control (0), low (LSBO; 15.7), medium (MSBO; 44.3) and high (HSBO; 73.4). The study was performed from calving until 84 days in milk, divided into three periods of 28 days each. Dry matter intake (DMI) was affected quadratically in response to SBO addition with the greatest and lowest values of 19.0 and 16.0 kg/day for LSBO and HSBO diets, respectively. The digestibility of potentially digestible NDF was quadratically affected by SBO with the greatest value of 623 g/kg for LSBO diet. Both milk and energy-corrected milk (ECM) production were quadratically affected by SBO inclusion, with greatest ECM values of 27.9 and 27.3 for LSBO and MSBO, respectively. Soybean oil inclusion linearly decreased milk fat concentration by 13.2% from control to HSBO. The CLA t10,c12-18:2 was observed in milk fat only for MSBO and HSBO diets. Soybean oil inclusion did not affect plasma glucose or serum concentrations of total proteins, globulins, albumin, urea nitrogen, beta-hydroxybutyrate, non-esterified fatty acids or insulin. Serum concentrations of total cholesterol, triglycerides and low-density lipoprotein increased with SBO supplementation. Soybean oil inclusion in sugarcane-based diets for early lactation dairy cows from 15.7 to 44.3 g/kg DM can improve energy intake and performance; however, at 44.3 g/kg DM milk fat concentration and ECM decreased. Soybean oil inclusion at 73.4 g/kg DM adversely affected energy intake, fiber digestion and performance of early lactation dairy cows and is not recommended.     

Effects of feeding supplemental palmitic acid (C16:0) on performance and milk fatty acid profile of lactating dairy cows under summer heat

The objective was to determine performance and milk fatty acid changes of high producing dairy cows in early lactation, under summer heat, by adding a supplemental rumen inert fat in the form of a saturated free fatty acid (856 g/kg C16:0/kg of total fatty acids) to the total mixed ration (TMR). Early lactation multiparous Holstein cows in two similar pens of 99 and 115 cows were used in a 2 × 2 Latin Square design experiment with 35 d periods during a period when daily high and low temperatures averaged 34.3 and 15.9 °C, the relative humidity averaged 51% and there were no rain events. The TMR was the same for both groups, consisting of approximately 435 g/kg forage and 565 g/kg concentrate, except that the vitamin/mineral premix had no added fat (control, C) or added fat (C16:0) at a level designed to deliver approximately 450 g/cow/d of supplemental fat if cows consumed 26.5 kg/d of dry matter (DM). The two TMR averaged 905 g/kg organic matter (OM), 318 g/kg neutral detergent fiber (aNDF), and 186 g/kg crude protein (CP). The ‘C’ TMR had 58 g/kg total fatty acids with an estimated net energy for lactation (NE_l) of 7.3 MJ/kg (DM), while the C16:0 TMR had 72 g/kg total fatty acids and 7.5 MJ/kg NE_l (DM). Whole tract digestibility of DM, OM, aNDF and CP tended (P<0.10) to increase, and that of fatty acids increased substantially (P<0.01), with C16:0 feeding, whereas, DM intake was not affected. Milk fat content decreased (P<0.01) with C16:0 feeding (37.5 versus 36.0 g/kg), whereas, true protein content tended (P=0.09) to increase. There was a tendency (P=0.07) for increased milk yield (36.69 versus 38.04 kg/d), while milk protein yield increased (P=0.03) with C16:0 supplementation (1.08 versus 1.13 kg/d). Milk fat yield was unaffected by treatment. Concentrations of short and medium chain milk fatty acids (C6:0–C15:0), decreased, or tended to decrease, with C16:0 addition (C13:0 and C15:0, P<0.10; all others, P≤0.05). The concentration of C16:0 increased (P<0.001) in milk triglycerides from cows fed C16:0 (27.10 versus 31.57 g/kg), the longer chain saturated fatty acids C17:0 and C18:0 decreased (P≤0.05) and other long chain unsaturated fatty acids were unaffected. Benefits of C16:0 feeding on cow productivity must be balanced against negative effects on the nutritive value of the milk (i.e., increased C16:0 in milk fatty acids) produced for human consumption. However, relatively low amounts of supplemental C16:0 (27.10 versus 31.57 g/kg in milk triglycerides for C and C16:0 supplemented cows, respectively) were actually secreted in milk, in spite of them being essentially fully digested in the digestive tract. Strategies to divide cows into production groups based on milk yield and/or milk fat proportions could further limit C16:0 secretion in milk. Supplemental dietary C16:0 may have positive effects on milk production that outweigh the negative health effects of the increased C16:0 content in the milk fat.     

Effects of dietary crude protein concentration on animal performance and nitrogen utilisation efficiency at different stages of lactation in Holstein-Friesian dairy cows

Nitrogen (N) excretion from livestock production systems is of significant environmental concern; however, few studies have investigated the effect of dietary CP concentration on N utilisation efficiency at different stages of lactation, and the interaction between dietary CP levels and stages of lactation on N utilisation. Holstein-Friesian dairy cows (12 primiparous and 12 multiparous) used in the present study were selected from a larger group of cows involved in a whole-lactation study designed to examine the effect of dietary CP concentration on milk production and N excretion rates at different stages of lactation. The total diet CP concentrations evaluated were 114 (low CP), 144 (medium CP) and 173 (high CP) g/kg DM, with diets containing (g/kg DM) 550 concentrates, 270 grass silage and 180 maize silage. During early (70–80 days), mid- (150–160 days) and late (230–240 days) lactation, the same 24 animals were transferred from the main cow house to metabolism units for measurements of feed intake, milk production and faeces and urine outputs. Diet had no effect on BW, body condition score, or milk fat, protein or lactose concentration, but DM intake, milk yield and digestibilities of DM, energy and N increased with increasing diet CP concentration. The effect of diet on milk yield was largely due to differences between the low and medium CP diets. Increasing dietary CP concentration significantly increased urine N/N intake and urine N/manure N, and decreased faecal N/N intake, milk N/N intake and manure N/N intake. Although increasing dietary CP level significantly increased urine N/milk yield and manure N/milk yield, differences in these two variables between low and medium CP diets were not significant. There was no significant interaction between CP level and stage of lactation on any N utilisation variable, indicating that the effects of CP concentration on these variables were similar between stages of lactation. These results demonstrated that a decrease in dietary CP concentration from high (173 g/kg DM) to medium level (144 g/kg DM) may be appropriate for Holstein-Friesian dairy cow to maintain milk production efficiency, whilst reducing both urine N and manure N as a proportion of N intake or milk production.     

e-Cow: an animal model that predicts herbage intake, milk yield and live weight change in dairy cows grazing temperate pastures, with and without supplementary feeding

This animal simulation model, named e-Cow, represents a single dairy cow at grazing. The model integrates algorithms from three previously published models: a model that predicts herbage dry matter (DM) intake by grazing dairy cows, a mammary gland model that predicts potential milk yield and a body lipid model that predicts genetically driven live weight (LW) and body condition score (BCS). Both nutritional and genetic drives are accounted for in the prediction of energy intake and its partitioning. The main inputs are herbage allowance (HA; kg DM offered/cow per day), metabolisable energy and NDF concentrations in herbage and supplements, supplements offered (kg DM/cow per day), type of pasture (ryegrass or lucerne), days in milk, days pregnant, lactation number, BCS and LW at calving, breed or strain of cow and genetic merit, that is, potential yields of milk, fat and protein. Separate equations are used to predict herbage intake, depending on the cutting heights at which HA is expressed. The e-Cow model is written in Visual Basic programming language within Microsoft Excel^R. The model predicts whole-lactation performance of dairy cows on a daily basis, and the main outputs are the daily and annual DM intake, milk yield and changes in BCS and LW. In the e-Cow model, neither herbage DM intake nor milk yield or LW change are needed as inputs; instead, they are predicted by the e-Cow model. The e-Cow model was validated against experimental data for Holstein–Friesian cows with both North American (NA) and New Zealand (NZ) genetics grazing ryegrass-based pastures, with or without supplementary feeding and for three complete lactations, divided into weekly periods. The model was able to predict animal performance with satisfactory accuracy, with concordance correlation coefficients of 0.81, 0.76 and 0.62 for herbage DM intake, milk yield and LW change, respectively. Simulations performed with the model showed that it is sensitive to genotype by feeding environment interactions. The e-Cow model tended to overestimate the milk yield of NA genotype cows at low milk yields, while it underestimated the milk yield of NZ genotype cows at high milk yields. The approach used to define the potential milk yield of the cow and equations used to predict herbage DM intake make the model applicable for predictions in countries with temperate pastures.     

Effects of isobutyrate on rumen fermentation, lactation performance and plasma characteristics in dairy cows

The objective of this study was to evaluate effects of isobutyrate supplementation on rumen fermentation, lactation performance and plasma characteristics of dairy cows. Twenty multiparous second filial generation (F2) cows of a cross between Chinese Jinnan Yellow and Holstein cows at 148 ± 4.5 days in milk and 22.3 ± 0.81 kg milk production were used in a replicated 4 × 4 Latin square experiment. The treatments were: control (without isobutyrate), low (LIB), medium (MIB) and high (HIB) isobutyrate supplementation of 20, 40 and 60 g per cow per day, respectively. Experimental periods were 30 days with 15 d of adaptation and 15 d of data collection. Dry matter (DM) intake was not affected by increasing isobutyrate supplementation, but milk yields were highest for the 40 g/d isobutyrate supplementation level, where proportion of milk fat, true protein and lactose were minimized. Ruminal pH (6.38–6.24) and ammonia N (13.8–11.1 mg/100 ml) were linearly (P<0.01) decreased, whereas total VFA concentration (124–131 mM) increased at a decreasing rate with increasing isobutyrate supplementation. The ratio of acetate to propionate increased linearly (P<0.01) from 2.77 to 4.43 as isobutyrate supplementation increased due to the increase in acetate production and decrease in propionate production. Digestibilities of OM in the total tract increased linearly (P<0.01) as isobutyrate supplementation increased, digestibilities of DM and EE were highest for the 40 g/d isobutyrate supplementation level, digestibilities of CP, aNDF and ADF increased at a decreasing rate with increasing isobutyrate supplementation. Plasma concentrations of glucose and growth hormone linearly (P<0.03) increased, whereas concentrations of non-esterified fatty acids linearly (P<0.01) decreased. Results indicate that supplementation of this diet with isobutyrate changed the rumen fermentation pattern towards acetate production, improved digestion and modified plasma concentrations of glucose and growth hormone. This suggests that isobutyrate stimulated digestive microorganisms or enzymes in a dose-dependent manner with the optimum isobutyrate dose at about 40 g per cow per day in terms of improved digestion.     

Physiological adaptations and ovarian cyclicity of Holstein and Montbéliarde cows under two low-input production systems

The objective was to study milk production, body reserve mobilization, metabolic and hormonal profiles, and ovarian cyclicity of Holstein-Friesian (HOLS) and Montbéliarde (MONT) cows under two low-input dairy production systems with seasonal spring calving: an extensive (EXT; 12 HOLS and 12 MONT) based on permanent diversified grasslands and zero concentrate, and a semi-extensive (SEMI; 12 HOLS and 10 MONT) based on established temporary grasslands and up to 4 kg/day of concentrate. Individual measurements were performed between −4 and 12 weeks of lactation. Cows in EXT secreted less milk (22.1 v. 24.4 kg/day), protein (660 v. 755 g/day) and energy (67.7 v. 74.4 MJ/day), had greater plasma β-hydroxybutyrate (BHBA) (0.97 v. 0.69 mM), lower glucose (59.0 v. 62.0 mg/dl) and IGF-1 (62 v. 71 ng/ml), lower milk fat concentration in fatty acids originating from de novo synthesis (e.g. ∑ 10:0 to 15:0) and greater concentration of those derived in part from mobilization of fat reserves (e.g. 18:0 and ∑>C16), and showed greater frequency of abnormal ovarian cycles compared with SEMI. Across production systems, HOLS produced more milk (24.7 v. 21.8 kg/day), protein (738 v. 674 g/day) and fat (939 v. 819 g/day), secreted more energy (75.1 v. 67.0 MJ/day), lost more body condition score (BCS) (1.41 v. 1.03) and reached a lower BCS nadir (1.12 v. 1.43), had greater plasma BHBA (0.91 v. 0.75 mM), lower insulin (15.9 v. 17.2 µIU/ml) and tended to have lower glucose (59.6 v. 61.4 mg/dl), had lower milk fat concentration in ∑ 10:0 to 15:0, tended to have higher ∑>C16 and tended to show more abnormal estrous cycles compared with MONT. Ultrasound measurements did not differentiate fat mobilization and were confounded by breed differences of skin thickness. The greater nutrient allowance in SEMI improved indicators of physiological status and ovarian function during early lactation compared with EXT, but did not attenuate body reserve mobilization because cows prioritized milk secretion. HOLS secreted more nutrients than MONT but lost more BCS, which negatively affected nutritional balance and tended to affect ovarian cyclicity during early lactation. Breed by system interactions were not observed except for a few variables.     

Effects of inclusion of neutral detergent soluble fibre sources in diets varying in forage particle size on feed intake, digestive processes, and performance of mid-lactation Holstein cows

The aim of this study was to evaluate effects of partial replacement of neutral detergent soluble fibre (NDSF) for starch in diets varying in particle size (PS) of alfalfa hay on chewing activities, ruminal fermentation, nutrient digestibility and performance in mid-lactation dairy cows. Eight multiparous Holstein cows (146 ± 6.0 d in milk; 36.7 ± 2.57 kg milk/d) were used in a replicated 4 × 4 Latin square design with four 21 d periods with the last 7 d for data collection. The experiment was a 2 × 2 factorial arrangement with 2 levels of NDSF (low = 85 g/kg or high = 130 g/kg diet dry matter) each combined with 2 PS (short = 20 mm or long = 40 mm) of alfalfa hay. Results show that forage PS alone, or in combination with NDSF inclusion, had no effect on dry matter (DM) intake. Although total chewing, eating and ruminating times were not affected by treatments, eating time per kg of neutral detergent fibre (NDF) ingested was higher in long versus short alfalfa hay-based diets (P<0.05). Feeding long forage PS increased sorting of the diet against particles >19 mm, and in favor of those <8 mm (P<0.05). Feeding diets high in NDSF lowered DM intake (P<0.05), but increased apparent digestibility of all nutrients including NDF (P<0.05) independent of forage PS. Ruminal pH and concentrations of total volatile fatty acids were unaffected by dietary treatments, however the proportion of butyrate was higher in ruminal fluid of cows fed high NDSF diets (P<0.05). Changes in milk composition included lower milk crude protein content in high NDSF diets and higher lactose content for short hay-based diets (P<0.05). That milk yield and milk energy output were similar in low versus high NDSF diets suggests that high NDSF-fed cows had higher energy efficiency due to lower DM intake. Results suggest that, independent of forage PS, NDSF sources can be successfully included to partly replace starchy grains in diets exceeding minimum fibre recommendations.     

Effect of prepartum diet on postpartum ovarian activity in Holstein cows in a pasture-based dairy system

The hypothesis was that supplementation during the late prepartum period will differentially affect reproductive and productive variables according to parity. Primiparous (n=22) and multiparous (n=22) pregnant autumn calving Holstein cows were stratified in two groups according to parity (primiparous or multiparous) and within each group were randomly assigned to two treatments: (a) low supplemented (LS) or (b) high supplemented (HS) prepartum diet. The LS group was offered 5.2 kg/cow/day (DM basis) of wheat silage, and the HS group 4.7 kg cow/day (DM basis)/of corn silage and 3.6 kg (DM basis) of wheat bran+12 g of urea. Both groups grazed on natural pastures. After calving, all cows received the same diet. The experimental period was from 3 weeks before calving to 7 weeks postpartum (PP); body condition score (BCS) and blood samples for hormonal analyses were obtained weekly and ovarian ultrasonography was conducted three times per week. The loss in BCS around calving was less pronounced in HS cows, but only multiparous supplemented cows maintained BCS throughout the study. Non-esterified fatty acids (NEFA) increased during the prepartum period in the LS but not in the HS cows, with peak values occurring on day 14 PP in all groups. During the remainder of the experiment NEFA was greater in LS than in HS cows. Prepartum treatment did not affect the proportion of cows that had ovulations from the first dominant follicle postpartum, but decreased the interval to first ovulation in multiparous cows (22.9 compared with 38.2 days; P<0.05). This was associated with greater plasma IGF-I concentrations at the time the dominant follicle of the first follicular wave reached its maximum diameter (8.0 compared with 3.6 nmol/L; P<0.05). However, prepartum treatment had no effect on onset of ovarian activity in primiparous cows. Supplementation had no effect on milk production or milk protein percentage but increased milk fat percentage. We conclude that feeding a high-supplemented prepartum diet to multiparous cows allowed them to maintain BCS around calving, and this was associated with greater concentrations of IGF-I and an earlier onset of estrous cycles after calving.     

Effects of flaxseed,raw soybeans and calcium salts of fatty acids on apparent total tract digestibility,energy balance and milk fatty acid profile of transition cows

Oilseeds offer some protection to the access of ruminal microorganisms and may be an alternative to calcium salts of fatty acids (FA), which are not fully inert in the ruminal environment. This study aimed to evaluate the effects of different sources of FA supplementation on apparent total tract nutrient digestibility, milk yield and composition, and energy balance (EB) of cows during the transition period and early lactation. We compared diets rich in C18:2 and C18:3 FA. Multiparous Holstein cows were randomly assigned to receive one of the four diets: control (n=11); whole flaxseed (WF, n=10), 60 and 80 g/kg (diet dry matter (DM) basis) of WF during the prepartum and postpartum periods, respectively; whole raw soybeans (WS, n=10), 120 and 160 g/kg (diet DM basis) of WS during the prepartum and postpartum periods, respectively; and calcium salts of unsaturated fatty acids (CSFA, n=11), 24 and 32 g/kg (diet DM basis) of CSFA during the prepartum and postpartum periods, respectively. Dry cows fed WF had higher DM and net energy of lactation (NE_L) intake than those fed WS or CSFA. The FA supplementation did not alter DM and NDF apparent total tract digestibility, dry cows fed WF exhibited greater NDF total tract digestion than cows fed WS or CSFA. Feeding WS instead of CSFA did not alter NE_L intake and total tract digestion of nutrients, but increased milk fat yield and concentration. Calculated efficiency of milk yield was not altered by diets. FA supplementation increased EB during the postpartum period. Experimental diets increased long-chain FA (saturated and unsaturated FA) in milk. In addition, cows fed WS and CSFA had higher C18:1 trans-11 FA and C18:2 cis, and lower C18:3 FA in milk than those fed WF. Furthermore, cows fed CSFA had higher C18:1 trans-11 and cis-9, trans-11 FA than cows fed WS. Although supplemental C18:2 and C18:3 FA did not influence the milk yield of cows, they positively affected EB and increased unsaturated long-chain FA in milk fat.     

Influence of exogenous enzymes on nutrient digestibility, extent of ruminal fermentation as well as milk production and composition in dairy cows

This experiment studied effects of a mixture of exogenous enzymes (ZADO^®) from anaerobic bacteria on ruminal fermentation, feed intake, digestibility, as well as milk production and composition in cows fed total mixed rations (TMRs; 0.7 corn silage and 0.3 of a concentrate mixture). Twenty lactating multiparous Brown Swiss cows (500 ± 12.4 kg live weight) were randomly assigned into two experimental groups of 10 immediately after calving and fed a TMR with or without (CTRL) addition of 40 g/cow/d of enzymes for 12 weeks. Addition of enzymes increased (P<0.05) rumen microbial N synthesis. Intake of dry matter (DM) and organic matter (OM) was positively influenced (P<0.05) by supplementation, and digestibility of all nutrients was higher (P<0.05) in the total tract of supplemented cows, although the magnitude of the improvement varied among nutrients, with the highest improvement in aNDFom and ADFom (418–584 and 401–532 g/kg respectively; P<0.05) than the other nutrients. Supplementation of enzymes also increased (P<0.05) rumen ammonia N and total short chain fatty acid (SCFA) concentrations, and individual SCFA proportions were also altered with an increase in acetate (61.0–64.8 mol/100 mol; P=0.05) before feeding, and acetate and propionate increased 3 h post-feeding (60.0–64.0 and 18.3–20.8 mol/100 mol respectively; P<0.05). Milk and milk protein production was higher (12.8–15.7 and 0.45–0.57 kg/d respectively; P<0.05) for cows fed the ZADO^® supplemented diet. This exogenous enzyme product, supplemented daily to the TMR of cows in early lactation, increased milk production due to positive effects on nutrient intake and digestibility, extent of ruminal fermentation and microbial protein synthesis.     

Dietary supplementation with maize distillers dried grains with solubles during late gestation and lactation: Effects on sow and litter performance,and on colostrum and milk composition

The objectives of this study were to determine the effects of maize distillers dried grains with solubles (DDGS) during late gestation and lactation on sow and piglet performance, and on colostrum and milk composition. Thirty-six second- and third-parity (2.43 parity) sows (Yorkshire) were allotted to 1 of 3 groups and fed diets containing 0 (control), 200 or 400 g DDGS/kg during the last 20 d of gestation and throughout a 21 d of lactation. Experimental diets contained 12.9 MJ metabolizable energy/kg and 9.7 g lysine/kg. The colostrum and milk samples were obtained on d 0 (farrowing) and d 21 (weaning). There were no differences (P>0.05) in the sows’ average gestation lengths, weaning-to-estrus interval, average daily feed intake, and the lactation backfat and body weight change between dietary treatments. There were no dietary effects (P>0.05) of DDGS on the numbers of total, born alive piglets, average birth weights, piglets per litter at weaning or piglets average daily gain during lactation. No differences (P>0.05) were observed in total solids, protein, fat and lactose among the sows fed the DDGS diets compared with the control. The composition of total solids and protein of sows colostrum and milk were higher at farrowing (d 0) than at weaning (d 21) (P<0.001). However, the fat and lactose content of sows colostrum and milk were increased (P<0.001) from d 0 (farrowing) to d 21 (weaning). In conclusion, the results suggest that 400 g DDGS/kg (87 g lysine/kg) supplemented with 5.2 g lysine/kg included in late gestation and lactation diets is sufficient to replace all the dietary soybean meal without significantly affecting sow and litter performance or colostrum and milk composition.     

Effects of branched-chain volatile fatty acids on lactation performance and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows

Branched-chain volatile fatty acids (BCVFA) supplements could promote lactation performance and milk quality by improving ruminal fermentation and milk fatty acid synthesis. This study was conducted to evaluate the effects of BCVFA supplementation on milk performance, ruminal fermentation, nutrient digestibility and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows. A total of 36 multiparous Chinese Holstein cows averaging 606±4.7 kg of BW, 65±5.2 day in milk (DIM) with daily milk production of 30.6±0.72 kg were assigned to one of four groups blocked by lactation number, milk yield and DIM. The treatments were control, low-BCVFA (LBCVFA), medium-BCVFA (MBCVFA) and high-BCVFA (HBCVFA) with 0, 30, 60 and 90 g BCVFA per cow per day, respectively. Experimental periods were 105 days with 15 days of adaptation and 90 days of data collection. Dry matter (DM) intake tended to increase, but BW changes were similar among treatments. Yields of actual milk, 4% fat corrected milk, milk fat and true protein linearly increased, but feed conversion ratio (FCR) linearly decreased with increasing BCVFA supplementation. Milk fat content linearly increased, but true protein content tended to increase. Contents of C4:0, C6:0, C8:0, C10:0, C12:0, C14:0 and C15:0 fatty acids in milk fat linearly increased, whereas other fatty acids were not affected with increasing BCVFA supplementation. Ruminal pH, ammonia N concentration and propionate molar proportion linearly decreased, but total VFA production and molar proportions of acetate and butyrate linearly increased with increasing BCVFA supplementation. Consequently, acetate to propionate ratios linearly increased. Digestibilities of DM, organic matter, CP, NDF and ADF also linearly increased. In addition, mRNA expressions of peroxisome proliferator-activated receptor γ, sterol regulatory element-binding factor 1 and fatty acid-binding protein 3 linearly increased, mRNA expressions of acetyl-coenzyme A carboxylase-α, fatty acid synthase and stearoyl-CoA desaturase quadratically increased. However, lipoprotein lipase mRNA expression was not affected by treatments. The results indicated that lactation performance and milk fat synthesis increased with BCVFA supplementation by improving ruminal fermentation, nutrient digestibility and mRNA expressions of genes related to milk fat synthesis.     

Divergence for residual feed intake of Holstein-Friesian cattle during growth did not affect production and reproduction during lactation

Residual feed intake (RFI) is the difference between actual and predicted dry matter intake (DMI) of individual animals. Recent studies with Holstein-Friesian calves have identified an ~20% difference in RFI during growth (calf RFI) and these groups remained divergent in RFI during lactation. The objective of the experiment described here was to determine if cows selected for divergent RFI as calves differed in milk production, reproduction or in the profiles of BW and body condition score (BCS) change during lactation, when grazing pasture. The cows used in the experiment (n=126) had an RFI of −0.88 and +0.75 kg DM intake/day for growth as calves (efficient and inefficient calf RFI groups, respectively) and were intensively grazed at four stocking rates (SR) of 2.2, 2.6, 3.1 and 3.6 cows/ha on self-contained farmlets, over 3 years. Each SR treatment had equal number of cows identified as low and high calf RFI, with 24, 28, 34 and 40/11 ha farmlet. The cows divergent for calf RFI were randomly allocated to each SR. Although SR affected production, calf RFI group (low or high) did not affect milk production, reproduction, BW, BCS or changes in these parameters throughout lactation. The most efficient animals (low calf RFI) lost similar BW and BCS as the least efficient (high calf RFI) immediately post-calving, and regained similar BW and BCS before their next calving. These results indicate that selection for RFI as calves to increase efficiency of feed utilisation did not negatively affect farm productivity variables (milk production, BCS, BW and reproduction) as adults when managed under an intensive pastoral grazing system.     

Effect of Zinc Methionine or Zinc Sulfate Supplementation on Milk Production and Composition of Milk in Lactating Dairy Cows

Eighteen lactating dairy cows were used to compare the effects of organic and inorganic Zn supplements on milk production and chemical composition of milk. Animals received three diets in a randomized block design: basal diet with no supplemental Zn (control, 42 mg Zn/kg), basal diet plus 500 mg Zn/kg of dry matter (DM) as zinc sulfate monohydrate (ZnS) and basal diet plus 500 mg Zn/kg of DM as zinc methionine (ZnM). Results showed that milk and fat-corrected milk yield in dairy cows were not significantly affected by Zn source although a numerical increase was observed. The percentages of protein, lactose, fat, solid nonfat, total solid, and density of milk were not significantly different between treatments. However, dairy cows that received ZnM tended to produce more milk and fat-corrected milk with a lower somatic cell count as compared to controls. The zinc concentration in milk in the ZnM and ZnS groups was higher (P < 0.05) than in milk from the control group, but there were no significant differences between ZnS and ZnM groups.     

A comparison of energy balance and metabolic profiles of the New Zealand and North American strains of Holstein Friesian dairy cow

The milk production, energy balance (EB), endocrine and metabolite profiles of 10 New Zealand Holstein Friesian (NZ) cows and 10 North American Holstein Friesian (NA) cows were compared. The NA cows had greater peak milk yields and total lactation milk yields (7387 v. 6208 kg; s.e.d. = 359), lower milk fat and similar protein concentrations compared with the NZ cows. Body weight (BW) was greater for NA cows compared with NZ cows throughout lactation (596 v. 544 kg; s.e.d. = 15.5), while body condition score (BCS) tended to be lower. The NA strain tended to have greater dry matter intake (DMI) (17.2 v. 15.7 kg/day; s.e.d. = 0.78) for week 1 to 20 of lactation, though DMI as a proportion of metabolic BW was similar for both strains. No differences were observed between the strains in the timing and magnitude of the EB nadir, interval to neutral EB, or mean daily EB for week 1 to 20 of lactation. Plasma concentrations of glucose and insulin were greater for NA cows during the transition period (day 14 pre partum to day 28 post partum). Plasma IGF-I concentrations were similar for the strains at this time, but NZ cows had greater plasma IGF-I concentration from day 29 to day 100 of lactation, despite similar calculated EB. In conclusion, the results of this study do not support the premise that the NZ strain has a more favourable metabolic status during the transition period. The results, however, indicate that NZ cows begin to partition nutrients towards body reserves during mid-lactation, whereas NA cows continue to partition nutrients to milk production.