Effects of Bovine Somatotropin on Physiologic Responses of Lactating Holstein and Jersey Cows During Hot, Humid Weather

Abstract

Thirty-one lactating Holstein and Jersey cows were used to determine the effects of daily injections of 0 or 20 mg of recombinant bST on physiologic responses during hot, humid weather. Body temperature was determined by measuring milk temperature at each milking. Jugular blood was sampled for serum analysis of selected hormones, blood metabolites, and fatty acids, and arterial blood was sampled for blood pH and blood gas analysis. Milk was characterized for fatty acid composition. Blood pH was unchanged, but partial pressure of blood CO2, blood bicarbonate, base excess, and total CO2 declined with administration of bST. Serum triglycerides increased 89% in cows receiving bST. Blood urea nitrogen tended to decline in cows receiving bST. Serum cortisol, triiodothyronine, and thyroxine did not change, but insulin-like growth factor-1 increased 128% with bST use. Reduced milk short-chain fatty acids, increased milk long-chain fatty acids, and increased blood serum C18:1 fatty acid content occurred in cows administered bST and probably reflected tissue mobilization. Cows administered bST in hot weather had higher milk temperatures. Alterations in physiologic and metabolic measures in association with higher milk temperature suggest an interaction of bST use with hot, humid weather and reflect the need to minimize the effects of heat stress.

Effects of Cooling and Supplemental Bovine Somatotropin on Milk Production relating to Body Glucose Metabolism and Utilization of Glucose by the Mammary Gland in Crossbred Holstein Cattle

“…In the present study in both groups, milk yield was increased by rbST which accompanied with increases in both RT and RR throughout the experimental periods. The observation for an increase in heat production during rbST supplementation agrees with the reports of West et al (1991) and West (1994) that rbST-treated cows can increase heat production in a hot environment either high or lower milk producing cows.…”

“…The concentrations of FFA in milk were significantly increased by supplemental rbST in cooled and non-cooled cows (Table 7). A similar result for an increase in milk fat content due to prolonged administration of rbST has also been observed previously (West et al, 1991;Chaiyabutr et al, 2000b). It has been known that milk fat is synthesized from fatty acids of both blood lipids and from de novo synthesis within the mammary epithelial cells.…”

“…Environmental modifications such as fans and sprinklers (Fike et al, 2002) or evaporative cooling system (Chan et al, 1997;Chaiyabutr et al, 2008a) can be used to alleviate of severe heat stress and increase in milk production in dairy cattle. In addition to environmental modifications, other technologies can increase milk production in dairy cattle, for example, by supplementation of dietary methionine (Yang et al, 2010), or the application of exogenous bovine somatotropin (West et al, 1991;West, 1994). Somatotropin is known to play a role in responsible for galactopoietic and contributing to homeostasis and homeorhesis in ruminants (Bauman and Currie, 1980).…”

Basal levels and diurnal variations of some hormones and metabolites in blood of dairy cows treated daily with rbst in early and late lactation

“…Moreover, with respect to hormones, the concentrations of insulinlike growth factor (IGF-I) have been observed to increase after rbST administration (Ronge and Blum, 1989), but the rbST-IGF axis seems strictly dependent on the cow's nutritional status (Burton et al, 1994;Ronge et al, 1988). Insulin increments due to rbST treatment were also observed (Ronge and Blum, 1989;West et al, 1991), while other authors showed variable insulin changes after rbST treatment (Davis et al, 1988;de Boer and Kennelly, 1989;French et al, 1990). Many other authors have reported small changes of insulin and thyroid hormone concentrations (Butterwick et al, 1989;Chilliard et al, 1989;Cissé et al, 1991), and Johnson et al (1991) observed a significant reduction of 3,5,3'-triiodothyronine (T3) and cortisol concentrations.…”

Indicadores de estresse térmico e utilização da somatotropina bovina (bST) em vacas leiteiras mestiças (Bos taurus x Bos indicus) no semi-árido do Nordeste

“…Dentro de cada grupo de animais, a temperatura do leite apresentou aumentos significativos (P<0,05) entre os períodos da manhã e da tarde, com diferenças médias de 1,3ºC para os animais tratados e 1,1ºC para o grupo controle. WEST et al (1991) observaram que vacas Holandesas (n=6) e Jersey (n=8) tratadas com bST e mantidas em temperaturas de 22 a 35ºC (72% UR) apresentaram aumentos (P<0,01) de 0,3 a 0,6ºC na temperatura do leite em relação aos grupos controle. Dado que o número de animais no citado experimento foi semelhante ao utilizado no presente trabalho, a uniformidade do rebanho e, conseqüentemente, menor variabilidade dentro dos grupos tratados e controle provavelmente influenciaram os resultados dos testes estatísticos.…”