The Effect of Diets on Milk Production and Composition, and on Lactation Curves in Pastured Dairy Goats

Abstract

A 2-yr study investigated effects of different levels of concentrate supplementation on milk production, composition, and lactation curves in pastured dairy goats. For both years, 44 Alpine goats (Capra hircus; 55 +/- 11 kg body weight) were randomly allocated to 4 groups. Animals were supplemented with 0.66 (treatments A and B), 0.33 (treatment C), or 0 kg of concentrate (treatment D) per kg of milk over 1.5 kg/d. Mixed vegetative forages were rotationally grazed by the goats (treatments B, C, and D), except that treatment A was confined and fed alfalfa hay. Individual milk production was recorded daily, and milk samples were collected once every 2 wk for the 7-mo period (March to September) and analyzed for fat, protein, lactose, urea-N, nonesterified fatty acids, and allantoin (second year only). Milk yield and composition varied among dietary treatments, with some measures affected by year. Average daily milk yield was lowest for treatment D. The increased level of concentrate supplementation in treatment A led to 22% greater milk yield compared with treatment D. Milk production increased by 1.7 and 0.9 kg for each additional kilogram of concentrate fed per day during the first and second years, respectively. Average peak yield, time of peak yield, and persistency were lower for treatment D than for other treatments. The percentage of milk fat was lower for treatment D than for other treatments. Concentration of milk protein was greater for treatments A and B during the first year, and was higher for treatment C than for other treatments during the second year. Average milk lactose concentration was higher for treatments B and C than for other treatments. However, milk urea-N concentration in treatment A was higher than other treatments. Milk allantoin, used to estimate microbial proteins synthesis, was 20 to 25% greater for treatment A than for other treatments. Averaged across year, plasma urea-N and nonesterified fatty acids concentration were lowest for treatment B. Average organic matter intake was similar among treatments during both years. Ratios of acetate and propionate concentrations for treatment A were lowest among treatments. In conclusion, milk production and composition were affected by the feeding treatment and year. Increased level of nutrition lead to an increase in daily milk yield, peak yield, time of peak yield, and persistency compared with treatment D. Alpine dairy goats grazing on fresh forages without concentrate supplementation can produce milk inexpensively, and response to concentrate supplementation is greater for low quality pasture.

Relationship between milk urea, blood plasma urea and body condition score in primiparous browsing goats with different milk yield level

“…Plasma urea data was similar to those by Bava et al (2001) and Min et al (2005) but lower than those by Brun-Bellut (1996) in lactating Saanen and Alpine goats, by Cabiddu et al (1999) in goats browsing a Mediterranean shrubland and by Kohn et al (2005) in various breeds. Plasma urea increased throughout the lactation for LY, whereas it showed a curvilinear shape with the highest value from 105 to 135 DIM for IY.…”

“…Throughout the lactation, milk urea was always higher than plasma urea in all the levels. An analogous characteristic is recorded by Min et al (2005) in Alpine does, but not by Bava et al (2001) in Saanen goats when milk urea is constantly lower than plasma urea. It is an uncommon feature also in sheep (Jelínek et al 1996) and, in dairy cows, the two parameters are habitually correlated in a linear regression (Roseler et al 1993;Broderick et al 1997) and milk urea is higher than plasma urea only in particular phase of the day, e.g.…”

“…The trend of plasma urea was probably affected by the herbage availability and the feed intake, in accordance with the study of Eriksson & Valtonen (1982) which demonstrate that urea renal excretion declines even if plasma urea rises, for example when feed intake is inadequate and body proteins are utilized as a nitrogen source. In addition, in a study regarding grazing Alpine goats fed different supplementation rates (Min et al 2005), the highest plasma urea is recorded among the animals which received no concentrate supplementation. Even if the daily milk yield of HY goats was about twice the amount of LY goats throughout all lactation, productive differences were not able to change the urea metabolism of the goats belonging to the different levels as plasma urea values were not affected by the yield level.…”

Uso de un alimento integral como complemento a cabras locales en pastoreo: respuesta en producción y composición química de la leche

“…Sin embargo, al complementar la alimentación, se incrementó la concentración de proteína y lactosa en leche, indicadores de una mejora en la nutrición de las cabras, la cual se reflejo en una mejora en la condición corporal de las cabras. Por otra parte, el aumento en concentración de proteína en leche puede incrementar el rendimiento de derivados lácteos como queso, mantequilla, y leche en polvo (Min et al, 2005), debido a que la proteína representa alrededor del 60% de la MS de dichos derivados (Zeng et al, 2007), por lo que la complementación a las cabras pudierá representar en una leche más atractiva para la industria, con lo cual se prodria buscar mejorar el precio de venta por litro de leche.…”

Suplementación pre y postparto durante la estación lluviosa en cabras locales del norte de México

“…Sanogo et al (2013), por su parte, reportan incrementos en el contenido de proteína en leche de cabras Sahelian en la época lluviosa y Pinheiro et al (2014) indican un mayor contenido en la época de lluvias con respecto a la época seca en cabras Mestizas en Brasil. Por otra parte, el comportamiento del contenido de proteína en leche es similar al que reportan Min et al (2005), donde se observa una tendencia negativa constante desde el inicio, independientemente del nivel de concentrado ofrecido como suplemento, así mismo, Mohrand-Fer et al (2007) señalan que el contenido de proteína es más estable que el contenido de grasa, por esta razón, se intuye que la variación observada en este estudio no es significativa.…”