Protein and energy metabolism of lactating Granadina goats

Abstract

Twelve goats of the Granadina breed in mid-and late lactation were used in two consecutive years to determine their protein and energy requirements for lactation. The animals were individually fed on diets based on pelleted lucerne (Medicago sativa) hay and barley. A total of six balance experiments were carried out. Gas exchange was measured using open-circuit respiration chambers. Milk yield ranged widely from 0.649 to 1.742 kg/d in the first year and from 0.222 to 1.989 kg/d in the second year, a steady decline in milk output being observed as lactation progressed. Milk composition remained rather constant during the midstage of lactation, with an average content (/kg milk) for total solids, total nitrogen, fat and gross energy of 149.7 g, 5.39 g, 58.8 g and 3.59 MJ respectively. Total endogenous N, endogenous urinary N and maintenance requirement for N in lactating goats were estimated to be 244, 218 mg N/kg body-weight (W)07' per d and 478 mg total N/kg W0" per d respectively from regression equations. A constant efficiency of use of dietary N for milk N plus retained N of 51.0% was found. By regressing milk energy plus apparent body energy retention or loss on metabolizable energy (ME) intake, the maintenance energy requirement was estimated to be 401 k J ME/kg Wo75 per d. When estimating the corrected milk yield as milk energy + (0.84 x negative energy retention) + (1.05 x positive energy retention), regression analysis indicated that the overall efficiency of use of M E for lactation was 66.7%. Also, from a plot of apparent body energy retention Y . milk energy yield, both expressed as a percentage of M E intake above maintenance, the efficiency with which ME was used to promote energy retention in the body during lactation was calculated to be 0.907 times that for milk secretion.Energy metabolism : Protein metabolism : Goats Although nutrient requirements are now relatively well-defined in sheep and cattle, there is still a lack of reliable information in the literature about the nutritional needs of lactating goats. Most available information has relied on extrapolations of values derived from cattle and sheep experiments. Nevertheless, because of the specific physiological features of the goat, this approach needs further validation. Previous reports on protein and energy requirements of lactating goats have been derived mainly from feeding trials and only a limited number of studies have published results on nitrogen and energy balance trials. N requirements for maintenance and milk production in lactating goats have been obtained by N balance studies by Khouri (1974), Sengar (1980, Rajpoot et al. (1981), Brun-Bellut et al. (1984) and Ciszuk & Lindberg (1985). These studies indicate that, in goats, the N requirements for maintenance might be in agreement with reported findings for dairy cattle and sheep and also that the efficiency of use of dietary N for milk-protein synthesis appears to be somewhat lower than values given for dairy cattle. To our knowledge, the work of Armstrong & Blaxter (1 965), ...

Replacement of alfalfa hay ( Medicago sativa ) with maralfalfa hay ( Pennisetum sp.) in diets of lactating dairy goats

“…The tissue energy retained in the body was positive and did not differ between diets, even though energy content in milk was 35 kJ/kg of BW 0.75 higher in A than M. Thus, the efficiency of ME for milk production was different between diets; higher efficiency was obtained in A (0.64) than M (0.57). Different authors obtained greater values, such as Aguilera et al (1990) with lactating Granadina goats (k l = 0.67), while Bava et al (2001) found values ranging from 0.60 to 0.73 for Saanen goats during lactation. Moreover, Tovar-Luna et al (2010) investigated Alpine goats during lactation and found values ranging from 0.62 to 0.68.…”

Composition of goat and cow milk produced under similar conditions and analyzed by identical methodology

“…Water was available at all times. They were kept under identical environmental conditions except as concerns the nature and composition of the diet, which in each case was designed in accordance with the nutritional requirements and productive capacity of the species (ARC, 1980;Aguilera et al, 1990;NRC, 2007), and of their particular nutritional behaviour (Morand-Fehr et al, 1991;Boza, 2005). The health condition of the animals was supervised continuously, and any animal presenting any sign of disease was removed from the study.…”

Determinação de cobre e outros minerais em caprinos e ovinos criados no sertão do vale do rio São Francisco, Pernambuco

“…A maior parte da informação disponível consta de extrapolações calculadas a partir de dados de bovinos (Malafaia et al 2004). Não obstante, devido a características fisiológicas especí-ficas dos ovinos e caprinos são necessários mais estudos (Aguilera et al 1990). Ainda, a dosagem de determinados elementos bioquímicos, assim como a atividade de diversas enzimas no sangue pode auxiliar no diagnóstico, no prognóstico e no acompanhamento do tratamento dos animais (Morais et al 2000).…”