Impact of α‐amylase supplementation on energy balance and performance of high‐yielding dairy cows on moderate starch feeding

In dairy cows, exogenous α‐amylase is suggested to improve starch utilization and positively affect performance and health traits linked to energy balance and fertility. In a 1‐year feeding experiment, 421 cows were orally supplemented with α‐amylase (treatment: 12.5 g/kg dry matter (DM) addition rate to a concentrated feed) or non‐supplemented (control) on the basis of an ad libitum total mixed ration (TMR). Every cow was allocated to a high‐ (≥32 kg milk/day) or late‐lactation group (<32 kg milk/day), in which the TMR starch content was 220 ± 20.8 g/kg DM and 183 ± 24.8 g/kg DM, respectively. The energetic effect of α‐amylase supplementation seemed to be exclusively related to the high‐lactation stage (5–100 days in milk) in primiparous cows, where the daily milk yield was 32 ± 0.49 versus 31 ± 0.50 kg per cow in the treatment versus control group (P < 0.05). The pluriparous cows did not benefit from the supplementation that way. In neither primiparous nor pluriparous cows, was the milk composition, the fat‐to‐protein ratio, the somatic cell score, the backfat thickness, serum total bilirubin, β‐hydroxybutyrate and the fertility found to be systematically affected by α‐amylase supplementation.     

Effect of the type of silage on milk yield,intake and rumen metabolism of dairy cows grazing swards with low herbage mass

The aim of this study was to evaluate the effect of herbage allowance (HA) and type of silage supplemented (TS) on milk yield, dry matter intake (DMI) and metabolism of dairy cows in early lactation. Thirty‐six Holstein‐Friesian dairy cows were allocated to four treatments derived from an arrangement of two HA (LHA = 17 or HHA = 25 kg of DM/cow/day) and two TS (grass (GS) or maize (MS)). Herbage allowance had no effect on DMI or milk yield. Rumen pH and NH₃‐N concentration were not affected by HA. The efficiency of microbial protein synthesis in the rumen (microbial protein (MP)) was affected by HA with 21.5 and 23.9 g microbial nitrogen per kg ruminal digestible organic matter for LHA and HHA, respectively (P < 0.05). Supplementation with MS showed higher values of milk yield by 2.4 kg/cow/day (P < 0.001), milk protein content by 0.10 % (P < 0.023) and herbage DMI by 2.2 kg/cow/day, and showed lower values for milk urea compared to GS (P < 0.001). The former results suggest that TS had a greater effect on milk yield, total feed intake and energy intake than increase in herbage allowance; however, increase in HA had greater effects on MP than TS.     

Heat production, eating behavior and milk yield of lactating cows fed two rations differing in roughage content and digestibility under heat load conditions

The objective of this study was to measure the effect of feeding two total mixed rations (TMRs), differing in their roughage content and in vitro dry matter digestibility, on the respiratory rate, body temperature, eating behavior and energy balance of lactating cows. The partitioning of metabolizable energy intake (MEI) between heat production (HP) and retained energy (RE) of cows held under heat load conditions was measured. Forty-two lactating cows were divided into two similar sub-groups, each of 21 animals, and were fed either a control (CON) ration containing 18% roughage neutral detergent fiber (NDF) or an experimental (EXP) TMR that contained 12% roughage NDF and used soy hulls as partial wheat silage replacer. The in vitro DM digestibility of the CON and EXP TMRs was 75.3 and 78.6%, respectively (P < 0.05). The EXP diet reduced rectal temperature and respiratory rate of the cows while increasing their number of meals per day by 32.7% as compared with the CON fed cows, and these meals were shorter in duration and were eaten faster. The EXP diet increased total DM intake from 19.6 to 21.5 kg/cow/d, milk yield from 32.3 to 34.6 kg, and yield of energy corrected milk from 30.9 to 32.2 kg, as compared with the CON group. Cows fed the EXP TMR had increased RE in milk and body tissue, as compared with the CON group, but the diets had no effect on the measured HP that was maintained similar (121 vs. 127 MJ/cow/d) in the two groups. The measured MEI (MEI = RE + HP) and the efficiency of MEI utilization for RE production, were similar in the two dietary groups.     

Effects of Allium mongolicum Regel supplementation on the digestibility,methane production,and antioxidant capacity of Simmental calves in northwest China

This study evaluated the effects of Allium mongolicum Regel (AM) supplementation on nitrogen (N) balance, ruminal fermentation, and antioxidant properties. Sixteen male calves were assigned randomly to four groups, and the four were added with 0 (CON), 200 mg/kg (body weight; BW) (Low AM; LA), 400 mg/kg (BW) (Middle AM; MA), or 800 mg/kg (BW) (High AM; HA) per day for each individual. AM was added on dry matter (DM) basis. The experiment lasted for 58 days. Supplementation of AM could significantly increase average daily gain, DM digestibility, acid detergent fiber digestibility, and retained N/Intake N. N digestibility and molar proportion of propionate in the MA and HA treatments were higher than that in the CON treatment (p < .05), respectively. AM supplementation significantly increased the molar concentration of total volatile fatty acid in the rumen fluid (p < .05). The ratio of acetate to propionate in the MA and HA groups was lower than that in the CON treatment (p < .05). Furthermore, AM supplementation significantly reduced methane (CH₄) (p < .05) emissions. AM supplementation significantly increased the activities of superoxide dismutase. The MA group could significantly increase the activities of glutathione peroxidase and decrease the content of malondialdehyde. Our results indicated that AM supplementation could affect the nutrient digestibility, CH₄ emission, and antioxidant capacity of Simmental calves.     

Influence of fibrolytic enzymes in total mixed ration containing urea-molasses-treated sugarcane bagasse on the performance of lactating Holstein–Friesian crossbred cows

The aim of this study was to determine the effect of different levels of fibrolytic enzyme on nutrient utilization and milk production in dairy cows. Four multiparous early-to-mid-lactation Holstein–Friesian crossbred cows were randomly allocated in a 4 × 4 Latin square design. Cows were fed a balanced total mixed ration (TMR) on a dry matter (DM) basis containing 0, 1.2, 2.4, and 3.6 g/kg DM of fibrolytic enzyme in TMR, where the TMR comprises 60% concentrate supplemented with a fibrolytic enzyme at 0, 2, 4, and 6 g/kg DM of concentrate, and 40% urea-molasses-treated sugarcane bagasse (UMSB) was used as a roughage source. Fibrolytic enzyme supplementation in TMR containing UMSB did not affect dry matter intake (DMI) of dairy cows (p > 0.05). There was a quadratic effect of fibrolytic enzyme levels on the digestibility of DM, organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) (p < 0.05), and the maximal response was reached at 1.2–2.4 g/kg DM of fibrolytic enzyme added in the TMR. Furthermore, 3.5% fat-corrected milk, milk fat, total volatile fatty acids, and propionic acid were greater in a cow fed with 1.2–2.4 g/kg DM of fibrolytic enzyme, resulting in a lower ratio of acetic acid to propionic acid (p < 0.05). In conclusion, adding a fibrolytic enzyme in TMR containing UMSB improved nutrient utilization, rumen fermentation, and milk production of lactating dairy cows.     

Herbage intake,milk production and sward utilization of dairy cows grazing grass/white clover swards at low,medium and high allowances

Abstract

Herbage intake (HI), milk production and sward utilization of Norwegian Red Cattle dairy cows in mid-lactation, rotationally grazing grass/white clover swards at low, medium and high allowances (HA), were examined in three experiments (I, II and III). The daily target allowances per cow were 18 and 36 kg DM in Experiment I and 12, 18, and 24 kg DM in Experiments II and III. The cows were grazing in groups of seven (Experiments II and III) to ten (I) individuals. The proportions of white clover in the swards averaged 12%, 40% and 46% in Experiments I, II and III, respectively. In addition to pasture, the cows were fed concentrate mixtures in varying amounts (0–6.8 kg) with the highest amounts offered to the highest yielding cows. HI was estimated using the n-alkane technique. No effect of HA on HI was obtained in Experiment I. In Experiment II, and for II and III combined, there was a significant positive effect of HA on HI. The average increase in HI was 0.24 kg DM per extra kg DM on offer. The utilization of the sward (measured at 3 cm above ground level) decreased from 72% at the lowest HA to 51% at the highest HA in Experiment II and III. HA did not affect milk yield or milk composition significantly (P>0.05).     

Does body size of dairy cows,at constant ratio of maintenance to production requirements,affect productivity in a pasture‐based production system?

This study compared productivity of dairy cows with different body weight (BW), but a constant ratio of maintenance to production requirements in their first lactation, in a pasture-based production system with spring calving. Two herds, Herd L (13 and 14 large cows in 2003 and 2004 respectively; average BW after calving, 721 kg) and Herd S (16 small cows in both years; 606 kg) [Correction added after online publication 14 January 2011: 16 small cows in both years; 621 kg was changed to 16 small cows in both years; 606 kg], all in their second or following lactations, were each allocated 6 ha of pasture and rotationally grazed on 10 parallel paddocks with equal herbage offer and nutritional values. Winter hay, harvested from the same pastures, was offered ad libitum in the indoor periods in a tied stall barn. Each herd received, per lactation and year, approximately 2000 kg dry matter (DM) of concentrates and of fodder beets, equally distributed to every individual. Indoors, the L-cows ingested more DM than the S-cows (18.7 vs. 16.3 kg DM/cow per day; p < 0.01), but DM intake per 100 kg of metabolic BW was similar (13.0 vs. 13.1 kg DM/cow per day). Estimates based on the n-alkane technique gave similar results on pasture (17.9 vs. 15.5 kg DM/cow per day; p < 0.001). Roughage intakes per 100 kg of metabolic BW, at 13.5 kg DM/cow per day, were similar. Mean annual yield of energy-corrected milk (ECM)/ha was slightly higher for the S-herd than the L-herd (13,026 vs. 12,284 kg) but was associated with a higher stocking rate (on average +20%) for the S-herd. Feed conversion efficiency (1.2 vs. 1.3 kg ECM/kg DM intake) and overall milk production efficiency (45.3 vs. 47.3 kg ECM/kg metabolic BW) were similar in L- and S-cows. Thus, both dairy cow types were equally efficient in utilising pasture-based forage.     

Dry matter intake and milk production of grazing dairy cows supplemented with corn silage or a total mixed ration offered ad libitum in a subtropical area

This study aimed to evaluate the feeding choice, dry matter (DM) intake, and milk production of dairy cows that strip grazed on a mixed perennial species pasture receiving different supplementation strategies. The treatments were without supplementation (WS) or with supplementation of either corn silage (CS) or a total mixed ration (TMR) based on CS and concentrates, in a subtropical area. The supplements were provided ad libitum after the afternoon milking. Twelve Holstein × Jersey cows in mid-lactation (133 ± 43 days in milk) were divided into six groups (two cows/group) and distributed in accordance with a replicated 3 × 3 Latin square design, with three 21 day periods (15 adaptation days and 6 evaluation days). The total DM intake, milk production, milk fat, and milk protein production were greater in the TMR treatment than in the WS and CS treatments and were similar between the WS and CS treatments. The herbage DM intake and proportion of time spent grazing were greater in the CS treatment than in the TMR treatment. CS supplementation did not affect the total DM intake or milk production/cow, whereas TMR supplementation greatly improved the total DM intake and milk production of the dairy cows grazing on mixed perennial species.     

Effect of exogenous fibrolytic enzymes supplementation on milk production and nutrient utilization in Murrah buffaloes

The present study was conducted to evaluate the effect of commercial exogenous fibrolytic enzyme (EFE) mixture added at 1.5 and 3.0 g (cellulase 4,000 μM glucose/g/h + xylanase 7,990 μM xylose/g/min; 50:50 w/w) per kilogram of dry matter (DM) of feed on nutrient digestibility, milk production, milk composition, and some blood constituents in lactating Murrah buffaloes. Eighteen buffaloes were allotted to three dietary treatments, on the basis of milk yield (8.48, 8.52, and 8.53 kg/day) and days in lactation (68.5, 80.33, and 82.00) for 90 days. The buffaloes were fed a total mixed ration (TMR) comprising of 45% chaffed wheat straw, 15% chopped green maize, and 40% concentrate on DM basis (control group), the same TMR plus EFE at 1.5 g/kg DM (T-1 group) and the same TMR plus EFE at 3.0 g/kg DM (T-2 group) supplemented through the concentrate mixture. There was no effect of fortifying EFE mixture on DM intake and crude protein intake (grams per day) whereas total digestible nutrients intake (kilogram per day) was higher by (P < 0.05) 12.53% in T-1 group over that of control, and there was no significant difference between T-2 and control groups. The average daily milk yield and 4% fat-corrected milk (FCM) yield was higher (P < 0.05) by 12.99% and 15.17% in T-1 group as over that of control, and there was no difference between T-2 and control groups. There was no (P > 0.05) difference in blood glucose and blood urea nitrogen concentration in different experimental groups. It is concluded that supplementation of cellulase and xylanase mixture at 1.5 g/kg of DM of TMR containing wheat straw (45%), green maize (15%), and concentrate (40%) on DM basis significantly increased (P < 0.05) the average daily milk yield and FCM yield in Murrah buffaloes due to improved dietary fiber digestion.     

The effect of maize silage type on the performances and methane emission of dairy cattle

To examine whether type of maize silage is important for milk production performances, maize silage LG30224 (LG) was compared with Falkone (FA), the latter having a 4.0% points lower rumen NDF digestibility and 19 g/kg dry matter (DM) more starch. To bridge the lower energy content of FA, a third treatment was involved by adding maize meal (MM) in a ratio of 92/8 on DM (FA+MM). Maize and grass silage were fed ad libitum in a ratio of 65/35 on DM basis. Concentrates were supplemented individually to meet energy and protein requirements. The experiment was set up as a Latin square with three groups of nine Holstein cows during three periods of 3 weeks. In the last 2 weeks of each period, DM intake (DMI) and milk performances were measured. Each group included one cannulated cow to study effects on rumen fermentation. During the last 4 days of each period, two cows from each group were placed in gas exchange chambers to measure nutrient digestibility and methane production. Total DMI was higher (p < 0.05) for FA+MM (20.8 kg/day) than for FA (20.3 kg/day), while DMI for LG was intermediate (20.6 kg/day). Treatment did not affect milk production nor composition, whereas fat–protein‐corrected milk was higher for LG (30.5 kg/day) and FA+MM (30.3 kg/day) than for FA (29.9 kg/day). The ration did not affect pH nor volatile fatty acid composition in the rumen. Further, total tract digestibility of OM, crude protein, NDF and starch did not differ among treatments. The ration with LG gave higher methane production per day and per kg NDF intake than both rations with FA, but the difference was not significant when expressed per kg DMI or FPCM. Thus, maize silage type is of little importance for milk production if energy and physical structure requirements are met.     

Effects of malic acid on feed intake, milk yield, milk components and metabolites in early lactation Holstein dairy cows

The objective of this study was to evaluate the effects of malic acid (MA) on feed intake, milk yield and composition, blood metabolites and energy balance in early lactation Holstein dairy cows from 1 to 63 day in milk (DIM). Twenty-eight multiparous Holstein dairy cows, blocked by lactation number, previous 305-d mature equivalent milk production, and expected calving date, were arranged into four groups in a randomized block design. Treatments were: control (without MA), LMA, MMA and HMA with 70, 140 and 210 g malic acid per cow per day, respectively. The supplement of food grade MA (99.8% of MA) was hand-mixed into the top one-third of the daily ration. Cows were fed ad libitum a total mixed ration consisting of equal proportion of forage and concentrate. Milk yield increased (P = 0.04), but feed intake and milk components were not affected (P > 0.05) by MA supplementation. The energy balance, expressed as the difference between energy input and output, tended to be higher (P = 0.08) for MA supplemented cows during the 63-DIM period MA and supplemented cows showed a trend (P = 0.07) toward less loss of BW during the 63-day period, especially during the first 21-day of lactation. Concentrations of plasma glucose and serum insulin were higher for cows fed LMA, MMA, and HMA relative to control and linearly (P < 0.01) increased with increasing MA supplementation. Concentrations of non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA) and urine ketones were lower for MA-supplemented cows at 7, 14 and 21 DIM of lactation and linearly (P < 0.01) decreased with increasing MA supplementation. Although feed intake was not affected, milk yield increased, MA-supplemented cows experienced higher concentrations of plasma glucose and serum insulin, lower concentrations of plasma BHBA and NEFA, and lower concentrations of urine ketones, suggesting that nutrient digestibilities and energy availability may have been improved.     

Urea treated maize straw for small-scale dairy systems in the highlands of Central Mexico

Maize straw is the main roughage for dairy herds in campesino farms in central Mexico. The objective was to evaluate feeding milking cows on maize straw treated with 40 g/kg DM of urea (A) or untreated straw (B), and 3.0 kg/d of 18% CP concentrate. Twenty-four Holsteins in late lactation from 8 farmers were sorted in two groups: sequence A-B-A or B-A-B; periods were 28 days. Mean daily milk yield for the last two weeks per period, and live-weight and body-condition score every 14 days were used for analysis. Maize straw was ad libitum. Chemical analysis and in vitro digestibility were analysed by Student’s t test, animal variables by a switch-back design. ‘A’ had 44.3 g/kg DM more CP and 106.5 g/kg DM higher in vitro digestibility than ‘B’ (710 g/kg DM ± 0.75 ‘A’ vs. 603.5 g/kg DM ± 1.44 ‘B’). Despite higher digestibility and intake, there were no differences (P > 0.05) for milk yield, live-weight or body-condition score, although there were in straw intake (P < 0.05). Cows on ‘A’ ate 1.7 kg/cow/day more straw DM than on ‘B’. Lack of response did not offset higher feeding costs although margins were high. Lack of response is attributed to short length of periods and late lactation of cows.     

Effect of silage from ryegrass intercropped with winter or common vetch for grazing dairy cows in small-scale dairy systems in Mexico

The objective was to determine the effect of including silages of annual ryegrass (Lolium multiflorum) intercropped with winter vetch (Vicia villosa) (ARG-VV) or with common vetch (Vicia sativa) (ARG-VS) compared with maize silage (MS) on milk yield and milk composition of dairy cows grazing cultivated perennial ryegrass–white clover pastures with supplemented concentrate during the dry season. Six Holstein dairy cows with a mean yield of 19.0 kg/cow/day at the beginning of the experiment were randomly assigned to a 3 × 3 repeated Latin square. Treatments were: 8 h/day intensive grazing, 3.6 kg of dry matter (DM) per cow per day of concentrate plus MS, and ARG-VV or ARG-VS ad libitum at a stocking rate of 3.0 cows/ha for three experimental periods of 3 weeks each. Milk yield (MY) and milk composition, live weight and body condition score as well as silage and concentrate intakes were recorded during the third week of each experimental period, and pasture intake was estimated indirectly from utilised metabolisable energy. Economic analysis was obtained by preparing partial budgets. There were no statistical differences (P > 0.10) in MY, milk fat or protein content nor for live weight, but there was significant difference (P < 0.10) in body condition score. There were non-statistical differences in silage DM intake (P < 0.11); however, significant differences (P < 0.10) were obtained for estimated grazed herbage intake whilst no differences for total DM intake. Slightly higher economic returns (10%) were obtained with ARG-VS over MS, and this was 7% higher than ARG-VV. It is concluded that ARG-VS could be an option for complementing grazing for small-scale dairy production systems in the dry season as it is comparable to MS in animal performance and slightly better in economic terms.     

Effects of Feeding Dry Glycerol to Primiparous Holstein Dairy Cows on Follicular Development,Reproductive Performance and Metabolic Parameters Related to Fertility during the Early Post‐partum Period

This study examined the effects of dry glycerol supplementation on follicular growth, post‐partum interval to first ovulation, concentration of serum metabolites and hormones related to fertility, body condition score (BCS) and body weight (BW) in primiparous Holstein dairy cows. Sixty primiparous Holstein dairy cows were randomly assigned to two groups (control: n = 30 and glycerol supplemented: n = 30). Dry glycerol (250 g/day/cow) was fed as a top dressing to the common lactating total mixed ration (TMR) from parturition to 21 days post‐partum. Ovaries were examined four times using ultrasonography on days 13, 19, 25 and 36 post‐partum to determine ovarian follicular growth. Concentration of serum metabolites and hormones was determined weekly. Body condition score was evaluated weekly from weeks 1 to 5 after parturition, and BWs were recorded three times on days 1, 11 and 21 during the experimental period. The cows fed dry glycerol had more large follicles (p < 0.0001) and corpora lutea (CL) (p = 0.02) compared with the control cows. Days to the first ovulation (p = 0.06), days to first oestrus (p = 0.05), services per conception (p = 0.06) and days open (p = 0.004) were positively affected by dry glycerol supplementation. Serum concentration of glucose and insulin was higher in dry glycerol‐supplemented cows (p = 0.1; p = 0.06, respectively). Feeding glycerol had no effect on mean serum concentrations of β‐hydroxybutyrate, non‐esterified fatty acids and IGF‐1 during the experimental period. However, significant differences were observed at concentration of BHBA and IGF‐1 (p = 0.02 and p = 0.04, respectively) between two groups on day 21 after calving. The cows in the glycerol‐fed group had higher serum progesterone concentrations on days 33 (p = 0.007) and 36 (p = 0.004) after calving. Supplemented cows had lower body condition loss during weeks 1–5 after calving compared with the control cows (0.34 vs 0.41 BCS). In week 13 post‐partum, the proportion of cycling cows was 83.3 and 69.9% for those which received supplemented or non‐supplemented diet, respectively. These results demonstrated that feeding dry glycerol as a glucogenic supply may be useful to improve negative energy balance and reproductive efficiency in young cows which calve with high requirement of energy.     

Performance and Economics of Dairy Cows Fed a Corn Silage-Based Total Mixed Ration or Grazing Annual Ryegrass During Mid to Late Lactation

Economic and performance characteristics of a low cost grazing system based on annual ryegrass vs a total mixed ration (TMR) for cows during mid through late lactation were evaluated. Cattle used in the trial (28 Holstein and 12 Jersey cows) were blocked by parity, lactation number, days in milk, projected mature equivalent milk yield, and current milk yield, and cows were assigned to two treatments in a randomized complete block design. For 10 wk (March through May 1998), cows either received a corn silage-based TMR or grazed annual ryegrass and received no supplemental concentrates. Changes in feed composition, milk yield, milk composition, BW, condition score, and income over feed costs were examined. Cows on Treatment 1 were fed the TMR twice daily and were housed together in a free-stall barn. Cows assigned to grazing were allowed ad libitum access to annual ryegrass in a rotational 12-paddock system. Loose mineral was provided for ad libitum consumption, but no supplemental concentrate was offered. Daily milk production by the TMR cows was consistent, ranging between 22.5 and 27.2 kg per cow throughout the study. By contrast, daily milk production of the grazing cows declined from 26.6 to 15.9 kg per cow as lactation progressed. Ryegrass grazing reduced milk fat content during wk 4 and 8 of the study and increased MUN content during wk 2 but had no effect on milk protein content or somatic cell count. The BW, body condition score, and estimated DMI of grazing cows were less than they were for TMR cows. Milk income for the grazing cows was less than that for the TMR cows throughout the study. However, feed cost for grazing cows was substantially lower than that for the TMR cows. Hence, income over feed cost (IOFC) was greater for grazing cows than for TMR cows in all but the last 2 wk of the study. These results indicated that annual ryegrass grazing was more profitable than feeding a TMR to cows in mid to late lactation. However, grazing cows did lose body condition, which could have a negative effect on milk production in the subsequent lactation.     

Effect of several doses of zeolite A on feed intake,energy metabolism and on mineral metabolism in dairy cows around calving

The object of the present study was to determine the influence of different zeolite A doses on dry matter intake (DMI) and mineral metabolism, and to evaluate an optimum dosage for preventing hypocalcaemia. Eighty pregnant dry cows were assigned to four groups (I–IV). They were fed a total mixed ration (TMR) ad libitum. Groups II, III and IV received an average daily dose of 12, 23 and 43 g zeolite A/kg DM for the last 2 weeks prepartum. Individually DMI was recorded daily. Blood and urine samples were taken before, during and after zeolite A supplementation. Serum was analysed for Ca, Mg, P_i, K, non‐esterified fatty acids and β‐hydroxybutyrate (BHB). Urine was analysed for Ca, Mg, P_i, K and net acid‐base excretion (NABE). After calving, milk yield (fat corrected milk) and milk composition were determined. During zeolite A supplementation, mean DMI of Group IV (7.3 ± 1.3 kg/cow/day) was significantly lower compared to Groups I–III (10.1, 10.9, 9.5 kg/cow/day). The reduced feed intake of Group IV resulted in significantly increased BHB as well as decreased NABE after calving. Zeolite A supplementation in higher doses (III and IV) had a stabilizing effect on Ca metabolism around calving for older cows, whereas cows in Groups I and II showed a subclinical hypocalcaemia. The mean serum Mg concentration decreased significantly in older cows in Group IV at calving. The mean P_i concentration in cows of Group IV decreased into ranges of hypophosphataemia already 1 week after beginning of zeolite A feeding. The mean DMI postpartum as well as the milk yield was not affected by zeolite A supplementation. Feeding of 23 g zeolite A/kg DM TMR prepartum proved to be an adequate dosage for reducing subclinical hypocalcaemia frequency without significant effects on feed intake and P_i concentration in serum.     

Effects of body condition score at calving and feeding various types of concentrate supplements to grazing dairy cows on early lactation performance

The objective of the experiment reported here was to establish the effect of canola meal supplements of different protein degradability on the performance of grazing dairy cows with different body condition scores (BCS) in early lactation, and to compare this with feeding a cereal grain supplement instead. The experiment included a total of 72 cows in six treatments in a 2 ^* 3 factorial design, incorporating two BCS at calving (4.1 and 5.6 units on an 8-point scale), and three early lactation pelleted supplements. The three pelleted supplements were 100% wheat (wheat supplement), 50% wheat and 50% untreated mechanically extracted canola meal (a rumen degradable protein supplement), and 50% wheat and 50% canola meal that had been subjected to additional heat and pressure (a rumen undegradable protein supplement). It was hypothesised that fat cows would perform best with the treated canola meal supplement, which provided most rumen undegradable protein, whereas the type of protein would not be important for thin cows, and neither would the type of supplemental energy. Cows grazed pasture after calving at a daily pasture allowance of 35–40 kg DM/cow and were offered 6 kg concentrates each day. Cows were fed these diets for 92 days on average, from calving until three weeks into the mating period. Both canola meal-based supplements resulted in higher (P < 0.05) daily milk production than the wheat supplement (33.3 and 34.0 v. 30.5 kg/cow) in both thin and fat cows. Body condition score at calving positively (P < 0.05) affected average milk yield (31.6 v. 33.7 kg/cow), however, there was a time × BCS × supplement interaction whereby the fatter cows benefited from the use of either of the canola meal supplements for a longer period than did the thin cows. Average milk fat concentrations were greater (P < 0.05) where the canola meal supplements were fed (39.3 and 39.6 v. 35.6 g/kg), and in fat cows relative to thin cows (40.0 v. 36.3 g/kg). Serum urea concentrations were significantly (P < 0.05) lower in cows fed wheat than in those fed either of the canola meal supplements (3.1 v. 4.3 and 4.2 mmol/L). Serum β-hydroxybutyrate concentrations were lowest (P < 0.05) where wheat pellets were fed, and highest (P < 0.05) where treated canola meal pellets were fed, and plasma glucose concentrations were highest with wheat and lowest with the treated canola meal pellets. Thus, the hypothesis was not supported by the results of this experiment.     

Ruminal epithelial insulin‐like growth factor‐binding proteins 2, 3, and 6 are associated with epithelial cell proliferation

The aim of this study was to identify factors that regulate ruminal epithelial insulin‐like growth factor‐binding protein (IGFBP) expression and determine its role in rumen epithelial cell proliferation. Primary bovine rumen epithelial cells (BREC) were incubated with short‐chain fatty acids (SCFAs) at pH 7.4 or 5.6, lactate, lipopolysaccharide (LPS), insulin‐like growth factor‐I (IGF‐I), ‐II (IGF‐II), or recombinant bovine IGFBP2 (rbIGFBP2). The mRNA expression levels of IGFBP in BREC were analyzed using quantitative real‐time polymerase chain reaction (qRT‐PCR). The proliferation rate of BREC was analyzed using a WST‐1 assay. IGFBP2 gene expression tended to be lower with SCFA treatment (p < .1), and IGFBP6 gene expression was significantly lower with SCFA treatment (p < .05). IGFBP3 and IGFBP6 gene expression tended to be higher with d ‐Lactate treatment (p < .1). IGFBP3 gene expression was significantly higher (p < .05) with LPS treatment. BREC treated with IGF‐I grew more rapidly than vehicle control‐treated cells (p < .01); however, recombinant bovine rbIGFBP2 inhibited IGF‐I‐induced proliferation. IGF‐II and/or rbIGFBP2 did not affect BREC proliferation. Taken together, SCFA treatment decreased IGFBP2 and IGFBP6 expression in rumen epithelial cells, and lower expression of these IGFBP might promote rumen epithelial cell proliferation by facilitating IGF‐I.     

Effect of genistein on IGF‐1 and IGFBP‐1 in young and aged female rat ovary

The objective of this study was to assess the effects of genistein (GEN) on expression of insulin‐like growth factor 1 (IGF‐1) and insulin‐like growth factor binding protein 1 (IGFBP‐1) in young and aged rat ovary. Forty young female Sprague Dawley (SD) rats (200 ± 20 g) and forty aged female SD rats (490 ± 20 g) were selected and according to weight, they were divided into the following five groups with eight animals in each: negative control group (NC), low‐dose group (L), middle‐dose group (M), high‐dose group (H) and positive control group (PC). GEN group received GEN of 15, 30, 60 mg/kg respectively. It lasted 30 days. Concentrations of serum hormones, IGF‐1 and IGFBP‐1 were determined by enzyme‐linked immunosorbent assay (ELISA). Gene and protein expressions of IGF‐1 and IGFBP‐1 were determined by real‐time PCR and Western blot respectively. Compared with NC, GEN significantly increased oestradiol‐17β(E₂) level in aged rat, reduced luteinizing hormone (LH) level in young and aged rat. Serum levels of IGFBP‐1 in young rats were significantly higher in GEN groups (p < 0.05). mRNA and protein expression levels of IGF‐1 and IGFBP‐1 were positively correlated with GEN dose. GEN could significantly reduce the ratio of IGF‐1/IGFBP‐1 of aged rats. Multivariate Cox regression analysis result showed IGF‐1 and IGFBP‐1 levels significantly correlated with GEN dose. We speculate that there is an association between the addition of GEN and expression of IGF‐1 and IGFBP‐1, and the relationship between them is different in young and aged rat.