Effect of Exogenous Growth Hormone on Lactational Performance in High Yielding Dairy Cows

Abstract

Bovine growth hormone (bGH) was administered to high-yielding Holstein cows fed a complete mixed ration ad libitum. Commencing on day 74 of lactation, 10 cows averaging 34.4 kg milk per day were divided into two groups and received a daily subcutaneous injection of bGH (51.5 IU/day) or a placebo. Injections were continued for an 11-day period and differences in lactational performance, nitrogen balance and estimated energy balance between the two groups were compared for the last 5 days of the preinjection and injection periods. Growth hormone resulted in increases of 9.5% in milk yield, 22.7% in milk fat yield, 14.5% in milk lactose yield and a 17.1% increase in milk energy secretion. Feed intake was slightly reduced (-4.3%, nonsignificant) while milk protein secretion and nitrogen balance were unchanged. Serum growth hormone levels in the bGH group were maintained at the higher concentrations of the normal physiological range during the injection period. By 48 hours following the last injection, declining bGH concentrations approached control values, and milk production decreased to preinjection values. Serum prolactin levels and plasma concentrations of free-fatty acids were slightly increased during the injection period in the bGH group. Growth hormone clearly enhances milk synthesis in the high-yielding dairy cow.

Revue bibliographique : Variations quantitatives et métabolisme des lipides dans les tissus adipeux et le foie au cours du cycle gestation-lactation 2e partie : chez la brebis et la vache

“…Des résultats récents montrent que l'hormone de croissance diminue la réponse à l'insuline du tissu adipeux bovin in vitro, et accroît la réponse à l'adrénaline in vivo Bauman et Mc Cutcheon, 1986 ;Mc Cutcheon et Bauman, 1986). Les réponses in vitro peuvent de plus varier selon l'état nutritionnel de l'animal donneur de tissu (Keys et Capuco, 1985 ;Fekry et al, 1986 Peel et al, 1981Peel et al, , 1983Tyrrell et al, 1982 ;Bitman et al, 1984a ;Eppard et al, 1985a, b ;Richard et al, 1985).…”

Effects of Exogenous Growth Hormone on Milk Production and Nutrient Uptake by Muscle and Mammary Tissues of Dairy Cows in Mid-lactation

“…In most short-term studies, where GH has been administered over several days to a few weeks, increased milk production has occurred in the absence of a change in feed intake. Further, in studies of this type, exogenous GH has not altered digestibilities of dry matter, energy or nitrogen (Peel et al 1981;Tyrrell et al 1982). Thus it appears that GH alters the partition of nutrients such that nutrient supply to the mammary gland increases, perhaps at the expense of maintenance and/or growth of other tissues (see reviews by Bauman and Currie 1980;Bines and Hart 1982; see also McDowell et al 1987).…”

Local Intra-arterial Infusion of Growth Hormone into the Mammary Glands of Sheep and Goats: Effects on Milk Yield and Composition, Plasma Hormones and Metabolites

“…Although it is well documented that growth hormone (GH) increases milk production in cows Bines et al 1980;Peel et al 1981Peel et al , 1982, sheep (Dracy and Jordan 1954;Jordan and Shaffhausen 1954;Hart et al 1985) and goats Mepham et al 1984), the mechanisms by which the hormone exerts galactopoietic effects remain unclear. Bines et al (1980) and also raised the possibilities that GH acts directly or indirectly on the mammary gland or, alternatively, influences the supplies of key nutrients to the mammary gland, thereby influencing the capacity of the mammary gland to synthesize milk.…”