Short-term Effects of Exogenous Growth Hormone: Effects on Milk Production and Utilization of Nutrients in Muscle and Mammary Tissues of Lactating Ewes

McDowell, GH; Leenanuruksa, D; Niumsup, P; Gooden, J. M.; Walt, J.G. Van der; Smithard, R. R.

doi:10.1071/bi9880279

Cited by 17 publications

(12 citation statements)

References 29 publications

(37 reference statements)

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“…In this respect the present results are consistent with results of previous short-term studies with sheep (Dracy and Jordan 1954;Jordan and Shaffhausen 1954;Hart et al 1985;McDowell et al 1988), goats (Hart et al 1983;Mepham et al 1984) and dairy cattle (see McCut~heon and Bauman 1985;McDowell 1985;Johnsson and Hart 1986). Similarly, the present results with sheep are in conformity with results of previous longterm studies with dairy cows Peel et al 1985;Chalupa et al 1987).…”

Section: Discussionsupporting

confidence: 82%

“…1984) when administered over short periods of several days. In such short-term studies it has been shown 0004-9417/88/030357$03.00 that nutrient utilization in the body as a whole McDowell et al 1987b) and in muscle and mammary tissues (McDowell et al 1987a(McDowell et al , 1988 is altered by GH so as to increase the supply of nutrients for milk synthesis as was suggested originally by Bauman and Currie (1980) and Bines and Hart (1982).…”

Section: Introductionmentioning

confidence: 99%

“…The procedures used for insertion of catheters [polyvinyl chloride; Dural Plastics, Sydney] and catheter sizes were as described previously (Oddy et al 1984;Teleni and Annison 1986;McDowell et al 1988). Arterial catheters were inserted 8-10 days before, and venous catheters 3-4 days before, measurements of tissue metabolism at peak and during mid-to-Iate lactation (days 3 and 45 of the experiment, respectively).…”

Section: Surgical Preparationmentioning

confidence: 99%

“…The procedure originally described by Oddy et al (1981) and modified by McDowell et al (1988) was used.…”

Section: Tissue Blood Flowmentioning

confidence: 99%

“…Plasma glucose and NEFA, blood acetate, lactate and 3-hydroxybutyrate and plasma insulin and growth hormone were measured using the procedures outlined by McDowell et al (1987aMcDowell et al ( , 1988.…”

Section: Metabolites and Hormonesmentioning

confidence: 99%

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Responses of Lactating Ewes to Exogenous Growth Hormone: Short- and Long-term Effects on Productivity and Tissue Utilization of Key Metabolites

Sandles¹,

Sun²,

D'Cruz³

et al. 1988

Aust. Jnl. Of Bio. Sci.

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Responses to daily injections of bovine growth hormone (GH, 0·15 mg kg-1 liveweight), beginning on day 10 of lactation, were measured in lactating ewes. Milk yields of GH-treated ewes increased soon after commencement of injections and continued to increase for some 25 days before reaching plateau levels. By comparison, yields of ewes injected with excipient (controls) decreased over the experiment. There was a tendency for contents of milk fat to be higher and milk protein to be lower for GH-treated than for control ewes during the first 15-20 days after injections were started.At the beginning and over the first 15-20 days of the experiment feed intakes of both groups of ewes were similar, but thereafter intakes of GH-treated ewes gradually increased to reach plateau levels some 2OG-300 g day-l higher than for control ewes by about day 35. Liveweights of both groups of ewes decreased during the first 2 weeks of treatment then increased, with GH-treated ewes losing, then gaining, more weight than control ewes. The efficiency of food utilization for milk production was higher for GH-treated than control ewes throughout the experiment but digestibility of food organic matter was not different during the eighth week of the experiment. At the end of the experiment, body composition, assessed by dilution of tritiated water, was similar for both groups of ewes. Differences in milk production were not sustained after withdrawal of GH injections.Measurements of tissue uptake of key metabolites were made on days 3 and 45 of GH treatment. On day 3, GH lowered uptake of glucose and non-esterified fatty acids by leg muscle tissue and increased mammary uptake of non-esterified fatty acids. By day 45 there were no apparent differences of tissue uptake of key metabolites.The results indicate that there is a biphasic response to exogenous GH in the lactating ruminant. It appears that initially GH affects nutrient partition thereby increasing supplies to the mammary gland of key nutrients for milk synthesis. In the longer term, GH increases feed intake, which provides sufficient nutrients to sustain increased milk production and also Iiveweight gain.Extra keywords: Milk yield and composition, feed intake and digestibility, Iiveweight and body composition, arterial metabolites and hormones, arterio-venous differences, leg muscle and mammary tissue, non-esterified fatty acid kinetics, tissue blood flow.

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