Drivers,challenges and opportunities of forage technology adoption by smallholder cattle households in Cambodia

Forage technology has been successfully introduced into smallholder cattle systems in Cambodia as an alternative feed source to the traditional rice straw and native pastures, improving animal nutrition and reducing labour requirements of feeding cattle. Previous research has highlighted the positive impacts of forage technology including improved growth rates of cattle and household time savings. However, further research is required to understand the drivers, challenges and opportunities of forage technology for smallholder cattle households in Cambodia to facilitate widespread adoption and identify areas for further improvement. A survey of forage-growing households (n = 40) in July–September 2016 examined forage technology adoption experiences, including reasons for forage establishment, use of inputs and labour requirements of forage plot maintenance and use of forages (feeding, fattening, sale of grass or seedlings and silage). Time savings was reported as the main driver of forage adoption with household members spending approximately 1 h per day maintaining forages and feeding it to cattle. Water availability was reported as the main challenge to this activity. A small number of households also reported lack of labour, lack of fencing, competition from natural grasses, cost of irrigation and lack of experience as challenges to forage growing. Cattle fattening and sale of cut forage grass and seedlings was not found to be a widespread activity by interviewed households, with 25 and 10% of households reporting use of forages for these activities, respectively. Currently, opportunities exist for these households to better utilise forages through expansion of forage plots and cattle activities, although assistance is required to support these households in addressing current constraints, particularly availability of water, if the sustainability of this feed technology for smallholder cattle household is to be established in Cambodia.     

Pituitary hormone and insulin responses to infusion of amino acids and N-methyl-D,L-aspartate in horses

Thirty-nine adult light horse mares, geldings, and stallions were used in two experiments to assess the pituitary hormone and insulin responses to infusions of arginine, aspartic acid, lysine, glutamic acid, and N-methyl-D,L-aspartate (NMA). In Exp. 1, 27 horses were assigned to one of three infusion treatments: 1) physiological saline (1 L); 2) 2.855 mmol of arginine/kg BW in 1 L of water; or 3) 2.855 mmol of aspartic acid/kg BW in 1 L of water. In Exp. 2, 12 horses were assigned, in a multiple-square 4 x 4 Latin square design, to one of four infusion treatments: 1) 2 mL of saline/kg BW; 2) 2.855 mmol of lysine/kg BW in water; 3) 2.855 mmol of glutamic acid/kg BW in water; or 4) 1 mg of NMA/kg BW in water. In Exp. 1, an acute (within 20 min) release of growth hormone (GH) was induced (P = 0.002) by aspartic acid. In contrast, acute release of prolactin (P = 0.001) and insulin (P = 0.002) was induced only by arginine; moreover, the arginine effect on insulin was present only in mares (P = 0.011). In Exp. 2, an acute release of GH was induced (P = 0.001) by glutamic acid and NMA. In males, the glutamic acid-induced GH release was greater than that of NMA; in mares, the NMA-induced GH release was greater than that of glutamic acid (P = 0.069). Both lysine and glutamic acid induced (P = 0.001) acute release of prolactin, whereas an acute release of insulin was elicited (P = 0.002) only by lysine. The NMA-induced LH response was due almost entirely to the response in mares and stallions (P = 0.016), and the NMA-induced FSH release was due almost entirely to the response in mares (reproductive status effect; P = 0.004). In the horse, aspartic acid, glutamic acid, and NMA seem to stimulate GH release; arginine and lysine seem to stimulate prolactin and insulin release; and NMA seems to stimulate LH and FSH release. It seems that N-methyl-D-aspartate glutamate receptors are involved in controlling GH, LH, and FSH secretion, whereas other mechanisms are involved with prolactin secretion. These results also indicate that gonadal steroids interact with amino acid-induced pituitary hormone release in adult horses.     

Leptin, GH, PRL, Insulin and Metabolic Parameters Throughout the Dry Period and Lactation in Dairy Cows

Leptin may play a role in the endocrine-metabolic processes that guarantee the physiological course of lactation in dairy cattle. This study was aimed at determining the changes in plasma concentrations of leptin and some of the main hormones and metabolites involved in the lactogenetic process in high-yielding dairy cows throughout lactation; we also wanted to assess whether leptin secretion is subjected to seasonal influences. Blood samples were collected from 23 Italian Friesian dairy cows from the end of a lactation to the ninth month of the subsequent one; in addition, blood was sampled from 47 dairy cows in different phases of lactation during February and July. Plasma concentrations of leptin, growth hormone (GH), insulin, prolactin (PRL), glucose, non-esterified fatty acids (NEFA) and urea were quantified by either validated radioimmunoassay (RIA) or enzymatic colorimetric methods. At the beginning of lactation, GH concentrations significantly increased, while a significant reduction occurred in leptin and insulin. This endocrine condition, such as the significant increase in NEFA plasma concentrations, is indicative of a marked lipid mobilization. In the more advanced stages of lactation, when both energy and protein balances become positive, leptin plasma concentrations increased, whereas GH and NEFA concentrations declined. During the summer months, a significant increase in leptin plasma concentrations, irrespective of the phase of lactation, was observed. Collectively, our findings suggest that, in dairy cows, leptin may represent a 'metabolic signal' of animal's status of fattening and nutritional level; in addition, leptin seems to be influenced by photoperiod and environmental temperature.     

Responses of seasonally anovulatory mares to daily administration of thyrotropin-releasing hormone and(or) gonadotropin-releasing hormone analog

Seventeen seasonally anovulatory light horse mares were treated daily, starting January 5 (d 1), for 28 d with GnRH analog (GnRH-A; 50 ng/kg BW) and(or) thyrotropin-releasing hormone (TRH; 5 microg/kg BW) in a 2 x 2 factorial arrangement of treatments to test the hypothesis that combined treatment may stimulate follicular growth and development. Ovaries were examined via ultrasonography and jugular blood samples were collected every 3 d. Frequent blood samples were collected after treatment injections on d 1, 2, 4, 7, 11, 16, and 22; on d 29, all mares received an i.v. mixture of GnRH, TRH, sulpiride, and EP51389 (a growth hormone secretagogue) to assess pituitary responsiveness. No consistent effects (P > 0.1) of treatment were observed for plasma LH, FSH, prolactin, or thyroxine concentrations in samples collected every 3 d. The only effect on ovarian follicle numbers was a reduction in number of follicles 11 to 19 mm in diameter due to TRH treatment (P = 0.029). No mare ovulated during treatment. On the days of frequent sampling, mean LH (P = 0.0001) and FSH (P = 0.001) concentrations were higher in mares receiving GnRH-A and tended to increase from d 1 through 7. In contrast, mean prolactin (P = 0.001) and thyroid-stimulating hormone (P = 0.0001) concentrations were high in mares receiving TRH on d 1 but rapidly decreased thereafter. When mares were administered the secretagogue mixture on d 29, the LH response was greater (P = 0.0002) in mares that had previously received GnRH-A but the FSH response was not affected (P > 0.1); the prolactin response was greater (P = 0.014) and the TSH response was smaller (P = 0.0005) in mares that had previously received TRH. Surprisingly, an immediate growth hormone response to EP51389 was absent in all mares. In conclusion, daily GnRH-A treatment stimulated plasma LH and FSH concentrations immediately after injection; although no long-term elevation in preinjection concentrations was achieved, the responses gradually increased over time, indicating a stimulation of gonadotropin production and storage. Daily treatment with TRH stimulated plasma TSH and prolactin concentrations, but the response diminished rapidly and was minimal within a few days, indicating a depletion of pituitary stores and little or no stimulation of production. There was no beneficial effect of adding TRH treatment to the daily GnRH-A regimen.     

The relationship between body condition,leptin, and reproductive and hormonal characteristics of mares during the seasonal anovulatory period

An experiment was conducted to determine the effects of high vs low body condition scores (BCS) produced by restricted feeding on reproductive characteristics, hormonal secretion, and leptin concentrations in mares during the autumnal transition and winter anovulatory period. Mares with BCS of 6.5 to 8.0 were maintained on pasture and/or grass hay, and starting in September, were full fed or restricted to produce BCS of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) by December. All but one mare with high BCS continued to ovulate or have follicular activity during the winter, whereas mares with low BCS went reproductively quiescent. Plasma leptin concentrations varied widely before the onset of restriction, even though all mares were in good body condition. During the experiment, leptin concentrations gradually decreased (P < 0.0001) over time in both groups, but were higher (P < 0.009) in mares with high vs low BCS after 6 wk of restriction, regardless of initial concentration. No differences (P > 0.1) between groups were detected for plasma concentrations of LH, FSH, TSH, GH, glucose, or insulin in samples collected weekly; in contrast, plasma prolactin concentrations were higher (P < 0.02) in mares with high BCS, but also decreased over time (P < 0.008). Plasma IGF-I concentrations tended (P = 0.1) to be greater in mares with high vs low BCS. The prolactin response to sulpiride injection on January 7 did not differ (P > 0.1) between groups. During 12 h of frequent blood sampling on January 12, LH concentrations were higher (P < 0.0001), whereas GH concentrations (P < 0.0001) and response to secretagogue (EP51389; P < 0.03) were lower in mares with high BCS. On January 19, the LH response to GnRH was higher (P < 0.02) in mares with high BCS; the prolactin response to TRH also was higher (P < 0.01) in mares with high BCS. In conclusion, nutrient restriction resulting in low BCS in mares resulted in a profound seasonal anovulatory period that was accompanied by lower leptin, IGF-I, and prolactin concentrations. All but one mare with high BCS continued to cycle throughout the winter or had significant follicular activity on the ovaries. Although leptin concentrations on average are very low in mares with low BCS and higher in well-fed mares, there is a wide variation in concentrations among well-fed mares, indicating that some other factor(s) may determine leptin concentrations under conditions of high BCS.     

The effect of low to normal dietary phosphorus levels on zinc metabolism and tissue distribution in calves

Sixteen 10-wk-old, phosphorus (P)-depleted Holstein bull calves were fed for 6 wk a control diet containing .08% P or P-supplemented diets containing .14, .20 or .32% P with supplemental P from two sources (CDP and Dynafos). The diets contained .45, .56, .66 and .87% Ca. After 5 wk of the experiment, the calves were dosed orally with 65Zn, and daily total fecal collections were initiated. At the end of the experimental period, the calves were killed and tissue samples were taken for total Zn and 65Zn analyses. Growth, feed intake and feed efficiency improved with increasing dietary P levels. Level of dietary P and Ca had little or no effect (P greater than .05) on total Zn content of rib, tibia, liver, heart, kidney, muscle or blood. Likewise, 65Zn absorption and content in most tissues were not affected (P greater than .05). The results do not preclude the possibility of some minor effects of P levels on Zn metabolism. However, it is apparent that when adequate Zn is fed, any effects are likely to be of little or no practical importance.     

Serum neutralization of cytotoxin from Pasteurella haemolytica, serotype 1 and resistance to experimental bovine pneumonic pasteurellosis

Sera from several groups of experimental calves were tested for cytotoxin neutralizing capacity. The relationship between this capability and resistance of the animals to an experimental challenge was examined. All undiluted bovine sera tested, other than fetal bovine serum, neutralized cytotoxin. Preadsorption of selected sera with formalin-killed P. haemolytica did not reduce their neutralizing capacity. Crude IgG fractions extracted from bovine sera retained neutralizing capacity as well. Cytotoxin neutralization titers were determined by serial dilution of sera from cattle which were previously unexposed, naturally exposed, or exposed by vaccination to the organism. Both live and killed vaccines were used. Prior exposure to live organisms resulted in the production of antibodies to both cell surface antigens and cytotoxin, whereas exposure to the killed vaccine resulted in the production of antibodies primarily to cell surface antigens. Resistance to experimental challenge with the organism correlated directly with serum cytotoxin neutralizing titers.