Post-ruminal or intravenous infusions of carbohydrates or amino acids to dairy cows 2. Late lactation

The objectives of this study were to compare the effects of post-ruminal and intravenous infusions of wheat starch or glucose (CHO) or a mixture of amino acids (AA) on milk protein yield, nitrogen (N) utilisation, plasma metabolites and mammary extraction rate of dairy cows in late lactation. Eight cow, ruminally fistulated, was assigned to two 4 × 4 Latin squares during 14-day periods, where the last 7 days were for infusions. Infusions were: (1) starch in the abomasum (SP), (2) glucose in the blood (GB), (3) AA in the abomasum (AP), and (4) AA in the blood (AB). The experiment started 165 ± 4 days (mean ± s.e.) post partum (milk yield 22.5 ± 1.1 kg) Daily amounts of nutrients infused were 257, 283, 233, and 260 g for SP, GB, AP and AB, respectively. The cows were fed a basal diet consisting of a concentrate mixture and grass silage (55:45 on a dry-matter (DM) basis), where total dry-matter intake (DMI) was 13.3 kg/day. Milk production was affected by site of infusion within substrate, whereas infusion substrates within infusion site (CHO or AA) were of minor importance. Responses to intravenous infusions (GB or AB) were similar to those in early lactation, but more pronounced. Compared with SP infusion, GB infusion increased ( P < 0.05) milk yield, energy-corrected milk (ECM), protein and lactose yield by 1.4 and 0.9 kg, 38 and 59 g, respectively. The AB infusion had 1.4 and 1.3 kg, 51, 52 and 50 g higher ( P < 0.05) milk yield, ECM, protein, fat and lactose yields than the AP infusion, respectively. N balance data indicated higher losses of metabolic faecal nitrogen (MFN) by abomasal than by intravenous infusions, but the catabolism of AA was lower than in early lactation indicated by no difference ( P < 0.05) in urinary N excretion between treatments. Intravenous AA infusion increased plasma glucose and insulin above that of intravenous glucose infusion. The treatment effects on plasma insulin concentrations were higher in late than in early lactation, suggesting a higher sensitivity in late lactation even at similar negative energy balance. Compared with the SP infusion, GB infusion showed lower ( P < 0.05) concentrations of essential AA (EAA) and branched-chain AA (BCAA) resulting in a higher AA utilisation because of a higher milk protein production. AP infusion increased ( P < 0.05) plasma non-essential AA concentration compared with AB infusion, but infusion site of AA had no effect ( P>0.05) on plasma EAA or BCAA. It is concluded that it is the nutrient supply and not the lactation stage per se that is important for the response in milk production. Nevertheless, stage of lactation affects the N metabolism and the response in plasma hormone concentrations even when cows are in negative energy balance in both lactation stages.     

Effects of prolonged intravenous infusions of adrenaline on glucose utilization, plasma metabolites, hormones and milk production in lactating sheep

Lactating ewes received continuous intravenous infusions of adrenaline (0.05 micrograms/kg liveweight) for 4 days. Prior to, during and after adrenaline infusions, milk yield and composition were monitored. Plasma concentrations of metabolites and hormones were measured each day and glucose biokinetics were measured in non-steady state at the start and end of adrenaline infusions. During adrenaline infusion, milk yield and content of solids-not-fat decreased and milk fat content was reduced on the first day of infusion. Plasma glucose was raised throughout the period of adrenaline infusion, plasma lactate increased over the first 4 h from the start of infusion and plasma non-esterified fatty acids increased for 2 h at the start of infusion and tended to increase during the first 2-3 h after withdrawal of adrenaline. Plasma growth hormone remained relatively stable except for a marked increase at 30 min after withdrawal of adrenaline. At the start and immediately after withdrawal of adrenaline infusion plasma insulin was increased approximately twofold. Glucose production, but not utilization, increased at the start of infusions. Immediately after withdrawal of adrenaline glucose utilization increased 2.5-fold with a smaller response in glucose production. There was essentially no change in glucose clearance during adrenaline infusion but a marked increase occurred after withdrawal of adrenaline.     

Added dietary cobalt or vitamin B12, or injecting vitamin B12 does not improve performance or indicators of ketosis in pre- and post-partum Holstein-Friesian dairy cows

Vitamin B₁₂ is synthesised in the rumen from cobalt (Co) and has a major role in metabolism in the peri-paturient period, although few studies have evaluated the effect of the dietary inclusion of Co, vitamin B₁₂ or injecting vitamin B₁₂ on the metabolism, health and performance of high yielding dairy cows. A total of 56 Holstein-Friesian dairy cows received one of four treatments from 8 weeks before calving to 8 weeks post-calving: C, no added Co; DC, additional 0.2 mg Co/kg dry matter (DM); DB, additional 0.68 mg vitamin B₁₂/kg DM; IB, intra-muscular injection of vitamin B₁₂ to supply 0.71 mg/cow per day prepartum and 1.42 mg/cow per day post-partum. The basal and lactation rations both contained 0.21 mg Co/kg DM. Cows were weighed and condition scored at drying off, 4 weeks before calving, within 24 h of calving and at 2, 4 and 8 weeks post-calving, with blood samples collected at drying off, 2 weeks pre-calving, calving and 2, 4 and 8 weeks post-calving. Liver biopsy samples were collected from all animals at drying off and 4 weeks post-calving. Live weight changed with time, but there was no effect of treatment (P>0.05), whereas cows receiving IB had the lowest mean body condition score and DB the highest (P<0.05). There was no effect of treatment on post-partum DM intake, milk yield or milk fat concentration (P>0.05) with mean values of 21.6 kg/day, 39.6 kg/day and 40.4 g/kg, respectively. Cows receiving IB had a higher plasma vitamin B₁₂ concentration than those receiving any of the other treatments (P<0.001), but there was no effect (P>0.05) of treatment on homocysteine or succinate concentrations, although mean plasma methylmalonic acid concentrations were lower (P=0.019) for cows receiving IB than for Control cows. Plasma β-hydroxybutyrate concentrations increased sharply at calving followed by a decline, but there was no effect of treatment. Similarly, there was no effect (P>0.05) of treatment on plasma non-esterified fatty acids or glucose. Whole tract digestibility of DM and fibre measured at week 7 of lactation were similar between treatments, and there was little effect of treatment on the milk fatty acid profile except for C15:0, which was lower in cows receiving DC than IB (P<0.05). It is concluded that a basal dietary concentration of 0.21 mg Co/kg DM is sufficient to meet the requirements of high yielding dairy cows during the transition period, and there is little benefit from additional Co or vitamin B₁₂.     

Effect of rate of substitution of processed, urea-treated whole-crop wheat for grass silage on the intake, milk production and diet digestibility in dairy cows and ruminal metabolism in vitro

The effect of rate of substitution of processed, urea-treated whole-crop wheat (pWCW) for grass silage on intake, performance and whole-tract digestibility was evaluated using 44 dairy cows. Cows received 10.5 kg of concentrates per day and one of the following forage mixtures (dry matter (DM) basis): grass silage alone (W-0); 0.75 grass silage, 0.25 pWCW (W-25); 0.5 grass silage, 0.5 pWCW (W-50) or 0.25 grass silage, 0.75 pWCW (W-75). Forage DM intake increased linearly with inclusion rate of pWCW from 9.7 kg DM per day in cows fed W-0 to 14.6 kg DM per day in W-75. By contrast, milk and protein yield (kg/day) were higher (P < 0.05) in cows receiving W-25 compared with W-0, but there was no effect (P>0.05) of treatment on fat yield (kg/day). From week 11 of the experiment onwards, body condition score increased with rate of inclusion of pWCW (P < 0.05). Whole-tract apparent digestibility of organic matter (OM) and fibre (kg/kg), decreased linearly with rate of inclusion of pWCW. Assuming a constant digestibility of starch in the other diet components, the apparent digestibility of starch in pWCW was 0.95 kg/kg and was not affected by rate of inclusion (P>0.05). Four continuous culture vessels were used to determine the effect of rate of inclusion of pWCW on ruminal metabolism in four periods, each of 14 d duration with sampling conducted on days 9 to 14. Vessel ammonia concentration increased linearly (P < 0.05) with rate of inclusion of pWCW whilst mean pH tended (P = 0.06) to decrease. The ratio of acetate to propionate increased from 2.5 in vessels receiving W-0 to 3.2 in those receiving W-75 (P < 0.001). There was no effect (P>0.05) of treatment on digestibility (g/g) of OM, fibre or starch or microbial protein flow (g/day). It is concluded that forage DM intake increased linearly with rate of inclusion of pWCW, but there was no further improvement in milk yield from inclusion rates above 0.25 of the forage DM, with body condition score increasing instead. Increasing the inclusion rate of pWCW resulted in a more ketogenic volatile fatty acid profile but did not affect the efficiency of microbial protein synthesis when determined in vitro.     

High- and low-purity glycerine supplementation to dairy cows in early lactation: effects on silage intake,milk production and metabolism

This study evaluated the effects of supplemental low- and high-purity glycerine on silage intake, milk yield and composition, plasma metabolites and body condition score (BCS) in dairy cows. A total of 42 cows of the Swedish Red Breed, housed in individual tie stalls, were fed 0.25 kg of low- or high-purity glycerine on top of concentrate, twice daily, during the first 4 weeks of lactation. One-third of the cows acted as controls, receiving no glycerine. Silage was fed for ad libitum intake and concentrate was fed at restricted level of intake, about 6 kg/day for primiparous cows and 7 kg/day for multiparous cows. Feed refusals were weighed daily. Cows were milked twice daily, milk yield was recorded on four occasions per week and milk samples were collected simultaneously. Blood samples were drawn from the coccygeal vessel once a week. Low- and high-purity glycerine had no effect on silage or total dry matter intake (P = 0.38 and P = 0.75, respectively) or on BCS (P = 0.45). Cows fed high-purity glycerine tended to have higher milk yield than control cows (P = 0.06). Milk composition tended to differ among treatments. No main effects of treatment on concentration of glycerine (P = 0.44), glucose (P = 0.78), insulin (P = 0.33), non-esterified fatty acids (P = 0.33) and β-hydroxybutyrate (P = 0.15) in plasma. These data indicate that high-purity glycerine has the potential to increase milk yield, as well as enhance the milk protein concentration and milk fat + protein yield.     

Effects of wet brewers grains on milk yield,milk composition and blood components of dairy cows in hot weather

Twenty multiparous Friesian cows, 60–120 days postpartum, were allotted to two groups of ten cows each according to calving date, lactation number and daily yield, and assigned randomly to one of two diets in a crossover design experiment. The control diet was 45% maize silage (dry basis) and contained ground maize, soya bean meal and wheat bran in proportions which would ensure that the dietary dry matter contained 16.5% crude protein, 3.0 Mcal metabolizable energy kg⁻¹ DM and 14% crude fibre. The treatment diet contained wet brewers grains substituted for maize silage, soya bean meal and wheat bran to change the ruminally undegradable protein from 35% to 39% of crude protein. Ground maize was included in the same quantity as in the control diet. The diets were offered individually, in tie-stalls, as total mixed rations in two equal amounts for ad libitum intakes. The experimental period lasted from 18 June to 12 August 1994. The cows were allowed exercise in an open lot without shade. Dry matter intake, milk protein content and yield, as well as content of milk lactose and non-fat solids were not significantly affected by the diet. In contrast, wet brewers grains supplementation increased actual milk yield (24.8 v. 21.7 kg day⁻¹; P < 0.05), 4% fat-corrected milk yield (25.1 v. 21.1 kg day⁻¹; P < 0.01), milk fat content (4.08 v. 3.82%; P < 0.05), milk total solids content (12.89 v. 12.44%; P < 0.05) and milk fat yield (1.01 v. 0.83 kg day⁻¹; P < 0.05). Blood plasma concentrations of glucose, total protein, albumin, urea, triglycerides, cholesterol, phospholipids, sodium, potassium, calcium, phosphorus and magnesium were not affected by treatment.     

Feeding pigs amino acids as protein-bound or in free form influences postprandial concentrations of amino acids,metabolites, and insulin

Dietary proteins need to be digested first while free amino acids (AAs) and small peptides are readily available for absorption and rapidly appear in the blood. The rapid postprandial appearance of dietary AA in the systemic circulation may result in inefficient AA utilisation for protein synthesis of peripheral tissues if other nutrients implicated in AA and protein metabolism are not available at the same time. The objective of this experiment was to compare the postprandial concentrations of plasma AA and other metabolites after the ingestion of a diet that provided AA either as proteins or as free AA and small peptides. Twenty-four male growing pigs (38.8 ± 2.67 kg) fitted with a jugular catheter were assigned to one of three diets that provided AA either in protein form (INT), free AA and small peptides (HYD), or as free AA (FAA). After an overnight fast and initial blood sampling, a small meal was given to each pig followed by serial blood collection for 360 min. Postprandial concentrations of plasma AA, glucose, insulin, and urea were then measured from the collected blood. Non-linear regression was used to summarise the postprandial plasma AA kinetics. Fasting concentrations of urea and some AA were higher (P < 0.05) while postprandial plasma insulin and glucose were lower (P < 0.01) for INT than for HYD and FAA. The area under the curve of plasma concentration after meal distribution was lower for INT for most AAs (P < 0.05), resulting in a flatter curve compared to HYD and FAA. This was the result of the slower appearance of dietary AA in the plasma when proteins are fed instead of free AA and small peptides. The flatter curve may also result from more AAs being metabolised by the intestine and liver when INT was fed. The metabolism of AA of the intestine and liver was higher for HYD than FAA. Providing AA as proteins or as free AA and small peptides affected the postprandial plasma kinetics of AA, urea, insulin, and glucose. Whether the flat kinetics when feeding proteins has a positive or negative effect on AA metabolism still needs to be explored.     

The effect of granulated barley as single major ingredient in the growing or finishing diet on productive performance,carcass, meat and fat quality of heavy pigs

A total of 48 Duroc × (Large White × Landrace) gilts of 46.8 kg BW (86 ± 3 days of age) were used to investigate the effect of diet during the growing and finishing periods on growth performance and carcass, meat and fat quality. The control diet consisted of a commercial feedstuff and the granulated barley diet had that cereal as the single major ingredient. There were three treatments: (i) control diet provided from 45.6 to 127.8 kg BW (C group), (ii) control diet from 47.0 to 91.8 kg BW and granulated barley from 91.8 to 129.7 kg BW (C + GB group) and (iii) granulated barley from 47.9 to 93.1 kg BW and control diet from 93.1 to 135.1 kg BW (GB + C group). Each treatment was replicated eight times, with two pigs per replicate. The C group grew faster (P < 0.001) and had a better feed conversion ratio (P < 0.001) than the GB + C group, with C + GB being intermediate. Carcasses from C + GB gilts had higher backfat depth than those from C gilts, with GB + C being intermediate (P < 0.05). Also, the main joints (ham + shoulder + loin) had a higher (P < 0.01) yield in carcass in the GB + C group than in the C group, with C + GB being intermediate. The intramuscular fat (IMF) content was higher (P < 0.001) in loin from C + GB and GB + C gilts than in C gilts. The IMF of loin from C + GB gilts had higher (P < 0.05) C18:1n-9 and total monounsaturated fatty acid (FA) proportions than that from C gilts, whereas the C18:2n-6 and total polyunsaturated FA percentages were lower (P < 0.05) in C + GB gilts than in the remaining gilts. The total saturated FA percentage was lower (P < 0.05) in loin from GB + C than in that from C gilts. Hams from C + GB and GB + C gilts had higher (P < 0.05) C18:1n-9 and total monounsaturated FA proportions and lower C18:2n-6 and total polyunsaturated FA contents than those from C gilts. We can conclude that granulated barley provided during the growing or the finishing period improved some carcass and meat characteristics of heavy gilts desirable for dry-cured ham production.     

Responses of milk protein,arterial AA concentration,and mammary AA metabolism to graded abomasal casein infusion in lactating goats

It has been generally assumed in postruminal protein or AA infusion studies that casein or AA mixtures mimicking the essential AA (EAA) composition of milk approach ‘ideal protein’ status, but the differences in postabsorptive metabolism of individual EAA may bring the assumption into question. Graded amounts of caseinate sodium were abomasally infused into lactating goats, and concentrations in the plasma of carotid, mammary uptakes and utilization efficiencies of amino acids were monitored in the present study. The results indicated that arterial concentrations of all the amino acids, except for Arg were increased with the increase of caseinate sodium infused (P < 0.05). The increments in plasma concentration differed with individual EAA. Concentrations of Ile, Leu, and Lys increased about two-folds, and that of Met, Thr, Phe, and His increased 58.33, 32.5, 29.87, and 61.66%, respectively, when data of the 99 g/day and the control treatment was compared. Mammary extraction efficiencies of Arg, Thr, Lys, Leu, and Phe increased with graded casein infusion (P < 0.05), while those of the other EAA were not significantly changed (P > 0.05). Mammary extraction efficiencies of individual non-essential amino acids (NEAA) varied greatly, and ranged from 9.18 to 33.89% in the control treatment. Except for Pro, mammary extraction efficiency of NEAA increased with graded casein infusion. Mammary uptake to milk output ratios (U/O) of sequestered AA was generally increased with the increase of casein infused, but that of Thr, His, and Ala was not insignificantly changed (P > 0.05). Compared with the data of previous researchers, the U/O of Thr recorded in the present study was much lower (<0.42). We speculate that Thr may be extracted in forms other than FAA (such as peptide bond AA) by the mammary under conditions of the present study. Consistent with the results of other authors, mammary uptake of Arg was two times more than milk output even in the control treatment, which suggests that there may be a requirement of Arg other than milk protein synthesis in the mammary.     

The partial replacement of soyabean meal and rapeseed meal with feed grade urea or a slow-release urea and its effect on the performance, metabolism and digestibility in dairy cows

The objectives of the study were to determine the effect of the partial replacement of soyabean meal and rapeseed meal with feed grade urea or a slow-release urea on the performance, metabolism and whole-tract digestibility in mid-lactation dairy cows. Forty-two Holstein–Friesian dairy cows were allocated to one of three dietary treatments in each of three periods of 5 weeks duration in a Latin square design. Control (C) cows were offered a total mixed ration based on grass and maize silages and straight feeds that included 93 g/kg dry matter (DM) soyabean meal and 61 g/kg DM rapeseed meal. Cows that received either of the other two treatments were offered the same basal ration with the replacement of 28 g/kg DM soyabean and 19 g/kg DM rapeseed meal with either 5 g/kg DM feed grade urea (U) or 5.5 g/kg DM of the slow-release urea (S; Optigen^R; Alltech Inc., Kentucky, USA), with the content of maize silage increasing. There was no effect (P > 0.05) of dietary treatment on DM intake, which averaged 22.5 kg/day. Similarly, there was no effect (P > 0.05) of treatment on daily milk or milk fat yield but there was a trend (P = 0.09) for cows offered either of the diets containing urea to have a higher milk fat content (average of 40.1 g/kg for U and S v. 38.9 g/kg for C). Milk true protein concentration and yield were not affected by treatment (P > 0.05). Milk yield from forage and N efficiency (g milk N output/g N intake) were highest (P < 0.01) in cows when offered S and lowest in C, with cows receiving U having intermediate values. Cows offered S also tended to have the highest live weight gain (0.38 kg/day) followed by U (0.23 kg/day) and C (0.01 kg/day; P = 0.07). Plasma urea concentrations were higher (P < 0.05) at 2 and 4 h post feeding in cows when offered U and lowest in C, with animals receiving S having intermediate values. There was no effect (P > 0.05) of treatment on whole-tract digestibility. In conclusion, the partial replacement of soyabean meal and rapeseed meal with feed grade urea or a slow-release urea can be achieved without affecting milk performance or diet digestibility, with the efficiency of conversion of dietary N into milk being improved when the slow-release urea was fed.     

Glucose tolerance and serum concentrations of hormones and metabolites in goats ( Capra hircus) fed diets supplemented with inorganic and organic chromium salts

Adult goats (no. = 18) were supplemented with chromium (Cr, 0.5 mg/kg concentrate) for 120 days as Cr chloride and Cr yeast complex and their responses in terms of glucose tolerance and serum profiles of metabolites and hormones were measured. The goats were fed 200 g/day of the concentrate and reared under a semi-intensive regimen. Cr supplementation significantly reduced serum glucose ( P = 0.049) and cholesterol ( P = 0.0001) levels compared with the same in the control group (calculated as % change between days 0 and 120). Serum cortisol on day 120 was lower in goats fed Cr chloride than in the control group ( P < 0.05). Overall, the mean cortisol level was lower ( P = 0.001) in the goats receiving added dietary Cr. An intravenous glucose tolerance test (IVGTT) was performed on the goats on day 75. The clearance rate (k) of glucose between 5 and 60 min of glucose infusion was significantly higher ( P = 0.004) in the goats supplemented with Cr yeast compared with those on the control or the Cr chloride supplemented diets. The kinetic parameters as well as the k and T_1/2 responses for serum insulin during the IVGTT were not affected. The ratio between the insulin k to glucose k increased ( P = 0.011) in the goats fed added dietary Cr as Cr chloride compared with the control and the Cr yeast groups. Post-prandial serum levels of glucose (diet effect P = 0.038) and cholesterol (diet effect P = 0.033) was lower in both the Cr supplemented groups than the control. Serum glucose during an epinephrine challenge test tended to remain elevated ( P = 0.076) 2 h after epinephrine infusion in the Cr yeast group indicating a delayed return of serum glucose to the basal level. However, serum insulin and cortisol remained unaffected. Several changes in selected blood metabolites and hormone measurements were observed when Cr was added as a dietary supplement in the diet of the goats. Contrary to the generally accepted view, supplemental Cr may influence the metabolism of ruminants even in a non-stressed management regime.     

Associations between genetic merit for milk production and animal parameters and the fertility performance of dairy cows

Relationships between genetic merit for milk production and animal parameters and various parameters of reproductive performance were examined using multilevel binary response analysis in a study of 19 dairy herds for three successive years, representing approximately 2500 cows per year. The proportion of cows intended for rebreeding that were back in-calf again within 100 days of calving (ICR-100) and the proportion of cows that reappeared again with 365 (RR-365) and 400 days (RR-400) of a previous calving were considered in addition to the traditional measures of reproductive performance. Each 100-kg increase in genetic merit for milk yield was associated with an increased interval to first service (IFS) and calving index (CI) of 1.4 ( P < 0.001) and 1.8 days ( P < 0.001), respectively, a 0.5% increase ( P < 0.05) in calving rate to first insemination (CR-1) and 0.8% increase in RR-400. Each £10 increase in £PIN (the economically weighted yield selection index used in the UK that takes account of butterfat and protein yields) was associated with an increased IFS and CI of 1.5 ( P < 0.001) and 3.0 days ( P < 0.001), respectively. Cows with increased genetic merit for milk yield and £PIN were more likely to re-calve (RR-overall; P < 0.001). Each 1000-kg increase in 305-day milk yield was associated with an increased IFS and CI of 3.2 ( P < 0.001) and 7.8 days ( P < 0.001), respectively, and a 13.6 ( P < 0.001), 22.4 ( P < 0.001), 19.9 ( P < 0.001) and 19.0% ( P < 0.001) decrease in CR-1, ICR-100, RR-365 and RR-400, respectively. A 10-kg increase in maximum yield was associated with a 6.6-day increase in CI ( P < 0.001) and a 14.9 ( P < 0.001), 18.3 ( P < 0.001), 9.6 ( P < 0.05) and 14.2% ( P < 0.001) decrease in CR-1, ICR-100, RR-365 and RR-400, respectively. Fertility performance was also associated with season of calving, lactation number and dystocia score. Level of production had a larger effect on fertility performance than genetic merit for milk production suggesting that infertility at an individual cow level is more likely to be associated with increased production and an inability to meet the nutritional requirements of the cow.     

Supplementing sow diets with palm oil during late gestation and lactation: effects on milk production,sow hormonal profiles and growth and development of her offspring

The supplementing of sow diets with lipids during pregnancy and lactation has been shown to reduce sow condition loss and improve piglet performance. The aim of this study was to determine the effects of supplemental palm oil (PO) on sow performance, plasma metabolites and hormones, milk profiles and pre-weaning piglet development. A commercial sow ration (C) or an experimental diet supplemented with 10% extra energy in the form of PO, were provided from day 90 of gestation until weaning (24 to 28 days postpartum) in two groups of eight multiparous sows. Gestation length of PO sows increased by 1 day (P<0.05). Maternal BW changes were similar throughout the trial, but loss of backfat during lactation was reduced in PO animals (C: −3.6±0.8 mm; PO: −0.1±0.8 mm; P<0.01). Milk fat was increased by PO supplementation (C day 3: 8.0±0.3% fat; PO day 3: 9.1±0.3% fat; C day 7: 7.8±0.5% fat; PO day 7: 9.9±0.5% fat; P<0.05) and hence milk energy yield of PO sows was also elevated (P<0.05). The proportion of saturated fatty acids was greater in colostrum from PO sows (C: 29.19±0.31 g/100 g of fat; PO: 30.77±0.36 g/100 g of fat; P<0.01). Blood samples taken on 105 days of gestation, within 24 h of farrowing, day 7 of lactation and at weaning (28±3 days post-farrowing) showed there were no differences in plasma concentrations of triacylglycerol, non-esterified fatty acids, insulin or IGF-1 throughout the trial. However, circulating plasma concentrations of both glucose and leptin were elevated during lactation in PO sows (P<0.05 and P<0.005, respectively) and thyroxine was greater at weaning in PO sows (P<0.05). Piglet weight and body composition were similar at birth, as were piglet growth rates throughout the pre-weaning period. A period of 7 days after birth, C piglets contained more body fat, as indicated by their lower fat-free mass per kg (C: 66.4±0.8 arbitrary units/kg; PO: 69.7±0.8 arbitrary unit/kg; P<0.01), but by day 14 of life this situation was reversed (C: 65.8±0.6 arbitrary units/kg; PO: 63.6±0.6 arbitrary units/kg; P<0.05). Following weaning, PO sows exhibited an increased ratio of male to female offspring at their subsequent farrowing (C: 1.0±0.3; PO: 2.2±0.2; P<0.05). We conclude that supplementation of sow diets with PO during late gestation and lactation appears to increase sow milk fat content and hence energy supply to piglets. Furthermore, elevated glucose concentrations in the sow during lactation may be suggestive of impaired glucose homoeostasis.     

Grass silage particle size when fed with or without maize silage alters performance,reticular pH and metabolism of Holstein-Friesian dairy cows

The particle size of the forage has been proposed as a key factor to ensure a healthy rumen function and maintain dairy cow performance, but little work has been conducted on ryegrass silage (GS). To determine the effect of chop length of GS and GS:maize silage (MS) ratio on the performance, reticular pH, metabolism and eating behaviour of dairy cows, 16 multiparous Holstein-Friesian cows were used in a 4×4 Latin square design with four periods each of 28-days duration. Ryegrass was harvested and ensiled at two mean chop lengths (short and long) and included at two ratios of GS:MS (100:0 or 40:60 dry matter (DM) basis). The forages were fed in mixed rations to produce four isonitrogenous and isoenergetic diets: long chop GS, short chop GS, long chop GS and MS and short chop GS and MS. The DM intake (DMI) was 3.2 kg/day higher (P<0.001) when cows were fed the MS than the GS-based diets. The short chop length GS also resulted in a 0.9 kg/day DM higher (P<0.05) DMI compared with the long chop length. When fed the GS:MS-based diets, cows produced 2.4 kg/day more (P<0.001) milk than when fed diets containing GS only. There was an interaction (P<0.05) between chop length and forage ratio for milk yield, with a short chop length GS increasing yield in cows fed GS but not MS-based diets. An interaction for DM and organic matter digestibility was also observed (P<0.05), where a short chop length GS increased digestibility in cows when fed the GS-based diets but had little effect when fed the MS-based diet. When fed the MS-based diets, cows spent longer at reticular pH levels below pH 6.2 and pH 6.5 (P<0.01), but chop length had little effect. Cows when fed the MS-based diets had a higher (P<0.05) milk fat concentration of C18 : 2n-6 and total polyunsaturated fatty acids compared with when fed the GS only diets. In conclusion, GS chop length had little effect on reticular pH, but a longer chop length reduced DMI and milk yield but had little effect on milk fat yield. Including MS reduced reticular pH, but increased DMI and milk performance irrespective of the GS chop length.     

Effects of replacement of Moringa oleifera for berseem clover in the diets of Nubian goats on feed utilisation,and milk yield,composition and fatty acid profile

Replacement of conventional feedstuffs with cheap non-conventional ingredients may improve livestock performance and the quality of their products, particularly milk. The study considered the effects of Moringa oleifera (MO) foliage in replacement of berseem clover (BC) on feed utilisation and lactational performance in Nubian goats. A total of 16 lactating Nubian does, weighing 36.2±0.8 kg, were randomly assigned to four experimental treatments containing 0, 125, 250 and 375 g of MO per kg diet to replace 0 (M0), 25 (M25), 50 (M50) and 75% (M75) of BC (on dry matter (DM) basis) in a quadruplicated 4×4 Latin square design. The MO diets increased (P<0.01) feed intake and nutrient digestibility. Feeding MO diets improved (P<0.01) ruminal volatile fatty acids, acetate and propionate but reduced (P<0.01) valerate and iso-butyrate. Moringa diets increased (P<0.01) serum total protein, albumin and glucose but decreased (P<0.05) cholesterol and triglycerides. Milk yield and energy corrected milk, and milk total solids, fat and energy content were increased (P<0.01) in MO diets. Yields of milk components and energy were greater (P<0.05) for MO diets than for control diet. Milk total saturated fatty acids and athrogenicity index were lower (P<0.01), and unsaturated fatty acids, conjugated fatty acids and UFA/SFA ratio higher (P<0.05) for MO diets. It is concluded that feeding MO to replace 75% DM of BC improved feed utilisation, ruminal fermentation, and milk yield and quality in lactating Nubian goats.     

Estimates of genetic parameters and genetic trends for growth,reproduction, milk production and milk composition traits of Awassi sheep

Genetic parameters and genetic trends for growth, reproduction, milk production and composition traits were estimated for Syrian (S) and Turkish (T) Awassi sheep and their crosses maintained at the International Center for Agricultural Research in the Dry Areas Tal Hadya station, Aleppo, Syria (now in Terbol station in Lebanon). The data were spread over 9 years. The individual breed additive effects of T were positive and significant (P<0.05) for birth weight (BW). However, the values for weaning weight (WW) and pre-weaning weight gain (WG) were negative, even though they were significant (P<0.05). These estimates were positive and significant (P<0.05) for all reproduction and milk traits, except for litter weight at birth (LWB). The additive contributions of T were 60.72±0.94 days, 1.643±0.359 kg, 13.09±0.89 days, 16.13±0.89 kg, 1.12±0.44 kg, 0.71±0.26 kg, 2.80±0.72 kg and 0.83±0.32 kg for lambing interval (LI), litter weight at weaning (LWW), lactation length, milk yield, fat yield, protein yield, total solids yield and lactose yield, respectively. The heterosis effects, both individual and maternal, were non-significant (P>0.05) for most growth traits. Crossing of T with S, however, resulted in desirable and significant (P<0.05) individual heterosis effects for all the reproduction, milk production and constituent yields. The heritability (h²) estimates, both direct and maternal, were low for BW, WW, WG and all reproductive traits indicating major influence of environmental factors, whereas milk yield and composition had medium values. Birth weight had moderate genetic correlation with WW and WG. The genetic correlation between WW and WG was high (0.724±0.951). Lambing interval had large negative genetic correlation with LWB and LWW. However, LI had medium significant correlations with all the milk production and composition traits. Larger litter weights at birth had high and negative influence on milk yield of the dam and its constituents. Genetic changes over years for all traits were non-significant. The lack of genetic change in the studied traits calls for systematic and organized selection scheme.     

Effect of polymorphic variants of GH, Pit-1, and beta-LG genes on milk production of Holstein cows

Effect of polymorphic variants of growth hormone (GH), beta-lactoglobulin (beta-LG), and Pit-1 genes on milk yield was analyzed in a Holstein herd. Genotypes of the cows for these genes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Allele frequencies were 0.884 and 0.116 for L and V variants of GH, 0.170 and 0.830 for A and B variants of Pit-1, and 0.529 and 0.471 for A and B variants of beta-LG, respectively. GLM procedure of SAS software was used to test the effects of these genes on milk yield. Results indicated significant effects of these genes on milk yield (P < 0.05). Cows with LL genotype of GH produced more milk than cows with LVgenotype (P < 0.05). Also, for Pit-1 gene, animals with AB genotype produced more milk than BB genotype (P < 0.05). In the case of beta-LG gene, milk yield of animals with AA genotype was more than BB genotype (P < 0.01). Therefore, it might be concluded that homozygote genotypes of GH (LL) and beta-LG (AA) were superior compared to heterozygote genotypes, whereas, the heterozygote genotype of Pit-1 gene (AB) was desirable.     

Feeding corn germ instead of corn grain on the performance of Holstein dairy cows fed low-forage diet and human-edible feed conversion efficiency

Using corn germ (CG) instead of corn grain could maintain dairy cow performance and might increase the efficiency of human food production. The primary objective of this study was to evaluate the effects of replacing corn grain with CG on the performance, nutrient intake, and digestibility of dairy cows. It also aimed to investigate the effect of CG on the efficiency of human food production in high-producing Holstein dairy cows in early lactation. Nine multiparous Holstein cows with 65.6 ± 8.5 DIM, milk yield of 55.6 ± 4.5 kg/d, and body weight of 611.3 ± 43.3 kg (mean ± SD) were used in a 3 × 3 Latin square design with 21-d periods. Treatments were (1) control treatment (CT, diet contains corn grain), (2) alternative treatment (AT, diet where corn grain was replaced with CG), and (3) balanced treatment (BT, diet where corn grain was replaced with CG but with the same energy content as CT). Control and balanced diets were isoenergetic (6.61 MJ/kg of DM); however, AT had higher energy (6.77 MJ/kg of DM). Treatments had no effect on dry and organic matter intake. NDF intake, however, was higher in CG diets compared with CT (P = 0.0001). Total-tract digestibility of DM tended to be reduced (P = 0.08), and OM digestibility was reduced (P = 0.05) by the inclusion of CG in diets. Whole and energy-corrected milk production were greater in AT compared with CT and BT (P < 0.05). Milk yield was similar in cows fed CT and BT. Treatments had no effect on milk composition or feed efficiency. Diet CT, when compared with CG diets, had lower efficiency in terms of human-edible feed conversion efficiency (HeFCE) and net food production (P < 0.05). Diet BT had greater HeFCE and net production of human-edible CP than AT (P < 0.05). Plasma BHBA, non-esterified fatty acids, and glucose concentrations were not affected by treatments, but plasma cholesterol was higher in cows that consumed CG diets (P = 0.04). The results indicate that, in high-producing early lactation dairy cows fed high concentrate diets, net food protein production can be substantially improved without lowering milk production through the reduction of dietary starch from 30.2 to 24.8% by replacing corn grain with CG.     

Ovine insulin induced-gene-2: molecular characterization,polymorphisms and association with milk traits

The aim was to characterize the INSIG-2 gene in Sarda sheep and to highlight associations between polymorphisms and milk traits. Two-hundred ewes, in their third or fourth lactation who lambed a single lamb between 20th and 30th of November, were chosen. Monthly individual milk yield was recorded and from each ewe a sample of milk was taken to analyze fat and protein content. PCR–RFLP and DNA sequencing were carried out to detect polymorphisms. Five exons have been characterized and five mutations have been found G88A, 436TCAGdel, A471G, C1071T and T1737G all in the intronic regions. The ovine sequence and related variations were deposited in GenBank with accession number JX843812.1. The animals carrying AA genotype at position 88 showed a lower milk fat concentration than those with the AG or GG genotype (P < 0.05). A lower milk fat concentration was registered also in the animals with the TCAG deletion in position 436 (P < 0.05) and in the animals carrying AA genotype at position 471 compared to those with the AG or GG genotype (P < 0.05). Moreover, the animals carrying CC genotype at position 1071 had a greater milk yield than those with CT or TT genotype (P < 0.05) while ewes with TT genotype showed a higher milk protein concentration compared to the others (P < 0.05). A total of 11 haplotypes were detected but no significant associations with milk traits were found. In conclusion for the first time the complete coding sequence of INSIG-2 gene and its association with milk trait has been reported in this study.     

Evaluation of production efficiencies at pasture of lactating suckler cows of diverse genetic merit and replacement strategy

Feed costs account for the largest proportion of direct cost within suckler beef production systems. By identifying the cow type with enhanced capability of converting grazed herbage to beef output across lactations, suckler cow systems would become more efficient and sustainable. The objective of this study was to estimate grass DM intake (GDMI) and production efficiency among lactating suckler cows of diverse genetic merit for the national Irish maternal index (Replacement Index) which includes cow efficiency components such as milk yield and feed intake. Data from 131 cows of diverse genetic merit within the Replacement Index, across two different replacement strategies (suckler or dairy sourced), were available over two grazing seasons. Milk yield, GDMI, cow live weight (BW) and body condition score (BCS) were recorded during early, mid and late-lactation, with subsequent measures of production efficiency extrapolated. Genetic merit had no significant effect on any variables investigated, with the exception of low genetic merit (LOW) cows being 22 kg heavier in BW than high genetic merit (HIGH) cows (P < 0.05). Beef cows were 55 kg heavier in BW (P < 0.001), had a 0.31 greater BCS (P < 0.05) and 0.30 Unité Fourragère Lait (UFL) greater energy requirement for maintenance compared to dairy sourced beef × dairy crossbred (BDX) cows (P < 0.001). The BDX had 0.8 kg greater GDMI, produced 1.8 kg more milk (P < 0.001), had a 0.8 UFL greater energy requirement for lactation and produced weanlings that were 17 kg heavier in BW than beef cows (P < 0.05). Subsequent efficiency variables of milk per 100 kg BW (P < 0.001), milk per kg GDMI (P < 0.001) and GDMI per 100 kg BW (P < 0.001) were more favourable for BDX. The correlations examined showed GDMI had moderate positive correlations (P < 0.001) with intake per 100 kg BW, net energy intake per kg milk yield, RFI and intake per 100 kg calf weaning weight but was weakly negatively correlated to milk yield per kg GDMI (P < 0.001). No difference was observed across genetic merit for beef cows for any of the traits investigated. Results from the current study showed that, while contrasting replacement strategies had an effect on GDMI and production efficiency, no main effect was observed on cows diverse in genetic merit for Replacement Index. Nonetheless, utilising genetic indexes in the suckler herd is an important resource for selecting breeding females for the national herd and phenotypic performance generated from this study can be included in future genetic evaluations to improve reliability of genetic values.