Somchai Chanpongsang

Effects of long-term administration of recombinant bovine somatotropin on milk production and plasma insulin-like growth factor and insulin in crossbred Holstein cows

The objective of the study was to determine the in vivo relationship between the long-term administration of recombinant bovine somatotropin (rbST), circulating levels of IGF-I and insulin, mammary blood flow and other variables relevant to milk synthesis, in crossbred, Holstein cattle. Ten first-lactation, non-pregnant, crossbred, Holstein dairy cattle were divided into two groups of five animals each: an experimental group and a control group. Animals in each group were fed with rice straw, treated with 5 kg urea dissolved in 100 litres water per 100 kg dry rice straw as the source of roughage. Four consecutive study periods were carried out in each group. These consisted of a pretreatment period (45 days postpartum before lactation peak) and three treatment periods during early lactation (105 days postpartum), mid-lactation (165 days postpartum) and late lactation (225 days postpartum). During the treatment periods, animals that had completed 60 days of lactation were injected subcutaneously at fortnightly intervals with 500 mg of recombinant bovine somatotropin (rbST) (POSILAC, Monsanto, USA) in the experimental group, while animals in the control group were injected subcutaneously at fortnightly intervals with 800 mg of sterile sesame oil, without rbST, as a placebo. During the pretreatment period, there were no significant differences in plasma concentrations of IGF-I, insulin and other parameters between the control group and the experimental group. During the treatment periods, the increase in the concentration of plasma IGF-I in rbST treated animals was significantly higher than in the control animals throughout the lactation period. Plasma glucose, protein and triglyceride concentrations in each group remained stable throughout the study. The total daily dry matter intakes were not significantly different between the groups. Milk yield increased by 20% with rbST treatment and it was 22% greater than that of the control animals receiving placebo in early lactation. Milk yield of rbST treated animals rose to a peak in early lactation and then gradually declined. In late lactation, milk yield of rbST-treated animals decreased by 19% as compared with early lactation. Udder plasma flow and udder blood flow markedly increased with rhST treatment and there were no significant changes in the control animals. The ratio of udder blood flow to the rate of milk production increased in mid- and late lactation in controls and the rbST treated animals. These findings suggest that the short persistency of lactation in rbST treated animals was similar to that in the control animals receiving placebo. Changes in milk production during the progress of lactation in rbST treated animals might not be controlled systemic;lily only but also locally within the mammary gland. The lack of effect of higher plasma IGF-I levels on persistency of lactation in rbST treated animals, may be due to changes in the pattern of IGF-I binding proteins and paracrine production inhibiting IGF-I action.

Effects of long-term exogenous bovine somatotropin on water metabolism and milk yield in crossbred Holstein cattle

The present study was conducted to evaluate the effects of long-term administration of recombinant bovine somatotropin (rbST) on the regulation of body fluids, mammary blood flow (MBF) and other variables relevant to milk synthesis, in crossbred dairy cattle (0·875 of Holstein-Friesian (HF) genes and 0·125 Red Shindi (RS) genes. Ten first lactation, non-pregnant, animals were chosen and divided into the control and experimental groups of five animals each. Four consecutive measurements were carried out in each group beginning on days 45 (pre-treatment), 105, 165 and 225 of lactation. Animals that had completed 60 days of lactation were injected subcutaneously every 14 days with 500 mg of rbST (POSILAC, Monsanto, USA) in the experimental group, while animals in the control group were injected subcutaneously every 14 days with 800 mg of sterile sesame oil, without rbST, as a control. All animals were fed with rice straw treated with 50 g urea/l as the source of roughage in combination with a similar concentrate throughout the experiments. During the treatment periods, the daily dry matter intake (DMI) was numerically greater for rbST-treated animals than for control animals, while the relative values of DMI per kg body weight and water intake showed no differences. Animals in both groups gained weight throughout the experiment with no significant differences between the groups. Animals receiving rbST for 45 days increased their peak milk yield from 13·4 kg/day per animal during pre-treatment to 15·9 kg/day per animal (18·7% increase) on day 105 of measurement and this peak yield was higher (19·5%) than those of control animals in the same period. Milk yields on days 225 in late lactation of both groups significantly decreased (P<0·05) in comparison with the early and mid-lactating periods. Over the course of the experiment, milk yield of the rbST-treated animals was significantly higher than those of the control animals (P<0·01). The administration of rbST significantly increased MBF (P<0·05) and mammary plasma flow (MPF) (P<0·01). The ratio of MBF to milk yield slightly increased as lactation advanced in both controls and rbST-treated animals. The administration of rbST significantly increased the absolute values of both plasma volume (P<0·01) and blood volume (P<0·05) when compared with the control animals. The control animals showed no significant changes in values of extracellular water (ECW) throughout the course of treatment periods. The rbST-treated animals increased in both the absolute values and the relative (proportion of body weight) values of ECW throughout the experiment (P<0·05). The estimated values of intracellular water (ICW) in both groups showed no significant changes during the course of treatments. There were no significant changes in the water turnover rate (WTO) and the biological half-life of tritiated water in different periods of lactation in both groups. The absolute values of total body water space (TOH) and total body water (TBW) were significantly greater in rbST-treated than control animals (P<0·05). The relative values of both TOH and TBW as a proportion of body weight of control animals decreased, while no alteration was apparent in rbST-treated animals during the course of treatments. These differences were statistically significant (P<0·05). The absolute values of empty body water (EBW) of the control animals showed no significant changes, while animals treated with rbST tended to increase in absolute values of EBW throughout the course of treatments. The effects of these differences were statistically significant (P<0·05). There were no significant changes in relative values of EBW during the course of treatments in both controls and rbST-treated animals. These data demonstrated that the rbST exerts its galactopoietic action in part through increases in TBW, EBW and ECW in association with an increase in MBF, which partitions the distribution of nutrients to the mammary gland for milk synthesis. During this long-term administration of rbST, the stimulant effect for milk yield was less in late lactation despite a higher MBF. The decline in milk yield during rbST treatment without fall in MBF in late lactation must be attributed to a local change within the mammary gland.

Glucose metabolism in vivo in crossbred Holstein cattle feeding on different types of roughage during late pregnancy and early lactation

An experiment was carried out to study the glucose kinetics of crossbred Holstein cattle feeding on either hay or 5% urea treated rice straw during late pregnancy (21 days prepartum) and early lactation (30 days postpartum). In all 16 pregnant heifers (23-25 months of age) were selected for the experiments, including eight animals of two breed types, Holstein Friesian x Red Sindhi (50:50 = 50% HF) and Holstein Friesian x Red Sindhi (87.5:12.5 = 87.5% HF). They were divided into four groups of four animals each. Animals from the same breed type in each group were fed with either rice straw treated with 5% urea or pangola hay (Digitaria decumbens) as the source of roughage throughout the experiments. The glucose turnover rate in both types of crossbred Holstein cattle was determined using a continuous infusion of [U-14C] and 3-[3H]glucose during late pregnancy and early lactation. Total glucose entry and utilization rates increased significantly during lactation for all groups. Recycling of [C]glucose was, approximately 20% in both crossbred cattle fed either hay or urea treated rice straw and was unaffected by the stage of late pregnancy or early lactation. Comparing 50 and 87.5% HF animals, arterial plasma glucose concentrations were slightly higher during pregnant periods but significantly higher in lactating periods in 50% HF animals. The ratio of specific radioactivity of arterial blood bicarbonate relative to that of arterial blood [14C]glucose in the lactating period, significantly decreased in 50% HF animals fed either urea treated rice straw or hay. An increase in udder blood flow during early lactation was significantly higher in 87.5% HF animals than in 50% HF animals. The uptake, arteriovenous differences and extraction ratio for glucose across the udder, significantly increased in the lactating period for all crossbred animals. Glucose uptake by the udder of 87.5% HF animals accounted for 65% of the total glucose turnover rate compared to a value of 46% in the lactating 50% HF animals. It can be concluded that both crossbred cattle fed either urea treated rice straw or hay exhibit the same body glucose turnover rate. The 87.5% HF animal has the genetic potential for a high milk yield and has high body and udder glucose metabolisms compared with 50% HF animals.

Effects of cooling and supplemental recombinant bovine somatotropin on diet digestibility, digestion kinetics and milk production of cross-bred Holstein cattle in the tropics

The aim of the current study was to determine how cooling and supplemental recombinant bovine somatotropin (rbST) affect body function with respect to digestion kinetics, digestibility and other variables relevant to milk production in cross-bred Holstein cattle. Ten primiparous cross-bred dairy cattle (0·875 Holstein Friesian × 0·125 Red Shindi) were used and divided into two groups of five animals each that were housed in a normal shaded barn (NS barn; non-cooled cows) and in a shaded barn with mist-fan cooling (MF; cooled cows). The cows in each group were supplemented with rbST in early, mid and late stages of lactation with three consecutive subcutaneous injections of 500 mg rbST every 14 days. All cows were fed the same total mixed ration twice daily at approximately 1·1 of assumed ad libitum intake and water was offered ad libitum. During the experimental periods, values of ambient temperatures and temperature humidity index (THI) in the NS barn were significantly higher than in the MF barn, whereas the relative humidity in the MF barn was significantly higher than in the NS barn (P<0·01). The respiration rate and rectal temperature were significantly higher for non-cooled cows than for cooled cows during the daytime whether there was or was not rbST supplementation. Supplementation of rbST for either cooled or non-cooled cows significantly increased dry matter intake (DMI), the efficiency of feed utilization and milk yields (P<0·05). Digesta kinetics using chromic oxide as an external marker showed a high digesta passage rate constant and low mean retention time of digesta in cows either by cooling or supplementation of rbST, whereas no changes were seen for the digestibility of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF). The half-time of Cr 2 O 3 in the whole digestive tract of cooled cows was lower than those of non-cooled cows and significantly decreased (P<0·05) during rbST supplementation in both groups in all stages of lactation. The magnitude of responses for the digesta passage rate and efficiency of feed utilization were larger in animals supplemented with rbST than in animals under MF cooling only. The main effect of cooling and supplemental rbST was to improve digestion by an increase in the rate of passage of digesta and in turn an increase in feed intake. Digestibility was not influenced by changes in passage rate of digesta either by cooling or rbST supplementation. Milk production in response to rbST supplementation is probably enhanced with cooling. The increased milk production induced by rbST supplementation was mediated by increased efficiency of feed utilization without changes in diet digestibility.

Glucose metabolism in crossbred Holstein cattle feeding on two types of roughage at different stages of lactation

An experiment was performed to study the glucose kinetics of crossbred Holstein cattle feeding on either hay or 5% urea-treated rice straw during early lactation (30 days post partum), mid-lactation (120 days post partum) and late lactation (210 days post partum). Two breeds: Holstein FriesianxRed Sindhi (50:50 = 50% HF) and Holstein FriesianxRed Sindhi (87.5:12.5 = 87.5% HF) were used. In early lactating 87.5% HF animals feeding on either hay or urea-treated rice straw, the high milk yields and lactose secretion were related to glucose uptake by the udder and udder blood flow as compared with those of 50% HF animals. Marked decreases in udder blood flow, glucose uptake, lactose secretion and milk yield were apparent in mid- and late lactation of both groups of 87.5% HF animals. In contrast, both groups of 50% HF animals showed no significant changes in udder blood flow, udder glucose uptake, lactose secretion and milk yields throughout the course of lactation. Total glucose entry rate using 3-[3H] glucose infusion, recycling of glucose carbon and plasma glucose clearance significantly increased during late lactation for 50 and 87.5% HF animals feeding on urea-treated rice straw. The utilization rates of glucose using [U-(14)C] glucose infusion were not significantly different among groups of animals and periods of lactation. It can be concluded that 87.5% HF animals have the genetic potential for a higher milk yield, but a shorter peak yield and poorer persistence in comparison with 50% HF animals. Changes in the utilization of glucose by the mammary gland for milk production in both groups of crossbred animals during feeding on either hay or urea-treated rice straw would be dependent on intramammary changes.

ALTERATIONS IN POTASSIUM HOMEOSTASIS DURING HEAT STRESS IN SWAMP BUFFALOES(BUBALUS BUBALIS)

Abstract 1. 1. Alterations in potassium homeostasis were studied in swamp buffaloes which were exposed to the sun for 5 h in acute heat exposure and exposed to the sun for 8 h each day for 10 days. 2. 2. Plasma volume, blood volume and blood pH increased significantly while packed cell volume (PCV) decreased at 5 h of acute heat exposure to the sun. 3. 3. Plasma glucose concentrations significantly increased along with an increased plasma insulin level after either acute heat exposure or short-term heat exposure at day 5 and day 10. 4. 4. The activity of red blood cell Na + , K + -ATPase increased significantly at 5 h of heat exposure while, at day 5 and day 10 of heat exposure, showing a tendency to increase but not significantly. 5. 5. Na-K pump numbers of red blood cells from the maximal ouabain binding capacity slightly increased at 5 h of heat exposure but significantly decreased at day 5 and remained at a low level in day 10 of the non-shaded period. 6. 6. The concentration of plasma potassium decreased during heat exposure while the concentration of potassium in red blood cells significantly increased. The concentration of chloride ions in red blood cells significantly decreased, along with a decrease of sodium in the red blood cells during heat exposure. 7. 7. It can be concluded that an acute heat exposure to the sun would affect primarily the internal balance of potassium homeostasis in buffalo, involving the distribution of potassium between extracellular and intracellular compartments, while prolonged heat exposure would affect both internal and external balance which involves primarily the potassium renal excretion.

Effects of supplemental recombinant bovine somatotropin and mist-fan cooling on the renal tubular handling of sodium in different stages of lactation in crossbred Holstein cattle.

The effect of supplementary administration of recombinant bovine somatotrophin (rbST) on the renal tubular handling of sodium in crossbred 87.5% Holstein cattle housed in normal shade (NS) or mist-fan cooled (MF) barns was evaluated. The cows were injected with 500 mg rbST at three different stages of lactation. The MF barn housed cows showed a slightly decreased ambient temperature and temperature humidity index, but an increased relative humidity. Rectal temperature and respiration rates were significantly lower in cooled cows. The rbST treated cows, housed in NS or MF barns, showed markedly increased milk yields, total body water, extracellular fluid and plasma volume levels, along with a reduced rate of urine flow and urinary excretion of sodium, potassium and chloride ions and osmolar clearance, in all three stages of lactation. Renal tubular sodium and water reabsorption were increased after rbST administration without any alteration in the renal hemodynamics. Lithium clearance data suggested that the site of response is in the proximal nephron segment, which may be mediated via increases in the plasma levels of aldosterone and IGF-1, but not vasopressin, during rbST administration.

Effects of misty-fan cooling and supplemental rbST on rumen function and milk production of crossbred Holstein cattle during early, mid and late lactation in a tropical environment.

Two groups of five crossbred 87.5% Holstein cattle were housed in normal shade only (NS) as non-cooled cows and in shaded housing with misty-fan cooling (MF) as cooled cows. The cows were treated with recombinant bovine somatotropin (rbST) in early, mid and late lactation with three consecutive injections of rbST in every 14 days. Ambient temperatures and the temperature humidity index in the NS barn were significantly higher than those of the MF barn, whereas relative humidity in MF was higher than that of NS barn. The DMI of cooled cows were higher than those of non-cooled cows, and cooled cows exhibited more response to rbST treatment. Exogenous rbST significantly increased milk yield throughout lactation. The rbST-treated cows had higher total ruminal fermentation products as volatile fatty acid and ammonia nitrogen than the non-rbST treated cows and associated changes were greater in cooled animals in all stages of lactation. Exogenous rbST increased the concentrations of milk urea nitrogen in both groups. These results suggest that the changes in ruminal fermentation with greater production of total VFA and NH(3)N in response to rbST in crossbred cows whether under misty-fan cooling or not, is in part through an increase in feed intake, thereby making more substrate available to the mammary gland for milk synthesis.

The effect of dietary ions difference on drinking and eating patterns in dairy goats under high ambient temperature

Objective The present study was carried out to evaluate the effect of high dietary cation and anion difference (DCAD) rations on diurnal variations in eating and meal patterns, water intake and urination patterns in dairy goats fed under high ambient temperature (HTa). Methods Ten crossbred dairy goats during peri-parturition period were selected and divided into two groups of five animals each. Experimental diets were control DCAD (control, 22.8 mEq/100 g dry matter [DM]) and high DCAD (DCAD, 39.1 mEq/100 g DM). The composition of two diets consisted of 44% corn silage and 56% concentrate. From the 2nd week to 8th week postpartum, goats were fed ad libitum twice daily either with the control or DCAD total mix ration with free access to water. The spontaneous eating and drinking patterns were determined. Results The environmental conditions in the present experiment indicated that goats were fed under HTa conditions (average peak THI = 85.2) and were in heat stress. In addition to the typical HTa induced tachypnoea in both groups, the respiratory rate in the DCAD group was significantly higher than the control group (p<0.05). Although the goats from both groups showed comparable level of eating, drinking and urination during experiment, the meal pattern and water intake were different. High DCAD apparently increased eating and meal patterns compared with the control. At week 8 postpartum, goats from high DCAD group had significant (p<0.05) bigger meal size and longer meal duration. Moreover, high DCAD appeared to increase night-time water intake (p<0.05). Conclusion Both meal pattern and night-time drinking effects of DCAD suggested that feeding with high DCAD ration may alleviate the effect of heat stress in dairy goat fed under HTa conditions.