The effect of bovine somatotropin treatment on production of lactating angora does with kids.

Abstract

Fourteen Angora does (35+/-2 kg), each with a single kid and in the first month of lactation, were used to determine ongoing (Period 1) and residual (Period 2) effects of chronic bovine somatotropin (bST) treatment. Specifically, we sought to determine whether chronic bST treatment was capable of improving milk yield, and thus kid growth, and mohair production of nursing does. The experiment consisted of a 2-wk pretreatment period, 5 wk of weekly subcutaneous treatment of slow-release bST (n = 7; Period 1), and a 4-wk posttreatment period (Period 2). The weekly dose of bST was calculated to release 100 microg/(kg BW.d(-1)). To estimate milk production, kids were separated from the does daily for 5 h, and their BW was recorded before and after suckling. The difference in BW was taken as milk production for 5 h. Fiber growth was measured by shearing does at the start of the experiment and at the end of Periods 1 and 2. Dry matter intake and BW of does were not affected by bST (P>.05). Average daily gain of kids that were suckling bST-treated does was higher (P<.05) than for kids of untreated does during Period 1 (184 vs. 139 g/d) but not during Period 2 (140 vs. 136 g/d; P>.10). Treatment with bST did not affect (P>.10) milk composition or clean fleece production in either period. Injection of bST did not affect (P>.10) plasma concentrations of glucose (mean = 49.5 mg/dL), urea N (mean = 19 mg/dL), total protein (mean = 72.5 g/d), or NEFA (mean = 122 microEq/L). During the period of bST treatment, plasma concentrations of somatotropin and IGF-I were increased (P<.05), concentrations of thyroxine and cortisol were decreased (P<.10), and plasma insulin levels were unchanged (P>.10) by bST. In conclusion, treatment of Angora dams with bST did not change DMI or mohair growth, but it improved growth of their kids.

Effects of field bean (Vicia faba L. var. minor) dietary supplementation on plasma thyroid hormones, insulin, insulin‐like growth factor‐1 concentrations and mohair characteristics in growing Angora goat kids

“…The higher mean IGF‐1 values found in males are consistent with data available for lambs when obtained before (Medrano and Bradford, 1991; Gatford et al., 1996) and soon after puberty (Roberts et al., 1990). The lack of any relationship between circulating IGF‐1 and mohair production supports previous findings in Angora goats treated with bovine somatotropin (Davis et al., 1999a,b). In ovine species, systemic endocrine actions of IGF‐1 at the hair follicular level did not seem important for wool growth (Cottam et al., 1992; Spencer et al., 1994; Adams et al., 1996a,b), while its fundamental role is thought to be paracrine (Su et al., 1999).…”

Thyroid hormones (th) and 5'-monodeiodinase (5'-md) activity in goat's milk from the early, mid- and late lactation period

“…5), and this result is in full agreement with the earlier findings (Anderson et al, 1988;Davis et al, 1999). The blood T 4 concentration was found to be decreased at the beginning of lactation which is consistent with a similar observation made in dairy cows (Mixner et al, 1962;Hart et al, 1978).…”

“…As it has already been found by Riis and Madsen (1985), there is an increasing thyroxine secretion rate from early to late lactation in milking goats, suggesting adaptive changes to body energy balance, that is to a negative energy balance at the beginning of lactation and to zero or positive energy balance during late lactation. This suggestion seems to be supported by more recent observations in lactating goats in which bovine somatotropin (bST) treatment, capable of improving milk yield, caused a decrease in thyroxine plasma concentration (Davis et al, 1999).…”

Physiological responses of dairy animals to recombinant bovine somatotropin: A review

“…In the case of goats, Davis et al (1999) using 14 multiparous Angora does injected with rbST (100 µg/kg BW/d), showed that body weight and dry matter intake of does were not affected by rbST treatment. Kids of rbSTtreated does had higher (P<0.05) average daily gain (ADG) by 32% than the kids of control, suggesting that kid ADG is probably a good indicator of actual milk production.…”

“…However, a few studies have investigated the effect of rbST on milk production in lactating dairy ewes and goats. The milk yield responses to rbST treatment in goats and sheep are more variable than that in cows (Davis et al, 1999). The rbST has been shown to be active in goats (Puchala et al, 2001).…”