Lactating Dairy Goats Research Articles

Insulin-like growth factor I (somatomedin c) in goats during normal lactation and in response to somatotropin treatment

1. 1. Two experiments were performed. In Experiment 1, IGF-I concentrations in serum were followed in four lactating dairy goats during normal lactation and before, during and after 14 days of daily administration of 10 IU recombinant bovine somatotropin, starting 10 weeks post-partum. In Experiment 2, IGF-I was measured in single blood samples obtained from 40 dairy goats in the first part of lactation. 2. 2. Measured IGF-I concentrations ranged from 4.4–9.0 nM. Concentrations varied during the day with coefficients of variation from 8.9 to 18.4% in the four goats in Experiment 1. There were no systematic trends in the diurnal variations ( P > 0.75). 3. 3. Concentrations of IGF-I remained fairly constant in all goats in Experiment 1 during the lactational period, and were not related to the changes in milk yield ( P > 0.65). Similarly, no relationship was found in Experiment 2 between level of milk production and IGF-I concentration in serum. 4. 4. Somatotropin treatment stimulated milk yields by 14 ± 2.9% ( P < 0.05) and IGF-I concentration by 27.9 ± 6.7% ( P < 0.05). 5. 5. IGF-I is the most likely factor which increases mammary gland synthetic capacity in response to somatotropin treatment, and thus is responsible for the galactopoietic effect of this hormone being exerted. 6. 6. However, serum IGF-I may primarily be involved in regulation of nutrient partitioning during normal lactation, but a paracrine synthesis with local effect on the mammary gland cannot be ruled out.

Responses in Feed Intake, Digestibility and Nitrogen Retention in Lactating Dairy Goats Fed Increasing Amounts of Urea and Fish Meal

Abstract Balance measurements were made on a total of 14 dairy goats of the Swedish Landrace breed during 3 experimental years. Experimental diets were composed of 40% hay and 60% concentrate mixture on a feed basis. The concentrate mixtures were unsupplemented or supplemented with urea (0.9, 1.8, 2.7 and 3.5%) or fish meal (3.9, 7.9, 11.7 and 15.8%) in increasing amounts. All diets were fed ad libitum. There was a gradual increase in buffer-soluble crude protein (BSCP) and effective rumen degradability of crude protein (EPD) in concentrates with added urea. The opposite was found in concentrates with added fish meal. EPD and BSCP in concentrate mixtures were linearly (p<0.001) related (r 2 = 0.72). Feed intake showed large between-animal variations, which were most pronounced at low and at high crude protein contents in the diet. The relative feed intake decreased significantly (p<0.01) with increasing urea and fish meal supplementation. However, milk protein production was well maintained on the fish meal diets. Organic matter digestibility was similar on all diets (73%; SD 0.7). Crude fibre (CF) digestibility varied between diets but was significantly (p<0.001) positively related to the amount of BSCP in feed organic matter in unsupplemented and fish meal supplemented diets. Significant (p<0.05) individual differences in CF digestibility were also apparent. The nitrogen balances (total N retention-milk N) were not significantly influenced by the diets fed and were, on average, 1.9 g N per day (SD 0.6). Increasing supplementation of urea was not significantly related to any increase in nitrogen accretion. Fish meal addition, on the other hand, gave a significant (p<0.05) curvilinear increase of nitrogen retention in milk.

Relation of Registration with Yield and Termination of First Lactation in Dairy Goats

First lactation records of 9941 Alpine, 2383 LaMancha, 11,203 Nubian, 3714 Saanen, and 4649 Toggenburg dairy goat does were obtained from the USDA to evaluate relation of registration (purebred, American, or grade) with lactation yield traits (mature equivalent milk and fat yields) and with reason for termination of lactation (normal, sold for dairy, or culled). Does were grouped by age at first kidding (11 through 16 mo or 21 through 26 mo) and by calendar year (1976 through 1978, 1979 through 1981, or 1982 through 1984). Data were analyzed within breed and year group for yield traits and within breed for reason of termination. Registration and age at first kidding accounted for little variation in mature equivalent milk and fat yields or in reason for termination.

Implication of Forage Particle Length on Chewing Activities and Milk Production in Dairy Goats

Twenty-four primiparous Alpine does fed a high concentrate ration were utilized to study the effect of forage particle length on chewing activity, ruminal components, and milk composition. Treatments were Bermudagrass hay with mean particle length of 2.38 and 3.87mm. Forage particle length was determined with an oscillating screen particle separator. Feeding forage with 3.87-mm mean particle length to lactating dairy goats resulted in higher total chewing and rumination times, slightly higher milk fat content, and fat-corrected milk production. Results from this experiment support the hypothesis that forage particle length affects chewing activities and production of milk fat precursors in the rumen and alters milk fat content and output of fat-corrected milk. Forage particle length appeared to be an important index for forage quality and a quantitative approach could be feasible to establish a system relating forage particle length to milk production in dairy goats.

Strategies for improving the nutritional status of small ruminants in tropical ecosystems

Research on goat and sheep nutrition and feeding systems has been initiated in five tropical or Mediterranean countries, by United States and host-country institutions which are participants in the Small Ruminant Collaborative Research Support Program. The major objective is to increase small ruminant productivity by better utilizing locally available feedstuffs and to more closely meet the nutritional needs of animals during the critical phases of their production cycle. West Java, Indonesia, is a humid tropical site with high rainfall and intensive agriculture, with small ruminants raised in nearly total confinement. Village feed resources include native grasses, tree legumes, and foliage from food crops. Energy may be the most limiting nutrient, due to seasonal feed availability and intake limitation when tropical grasses form a large proportion of the diet. Western Kenya is a wet-dry tropical site with a long and a short rainy season. The feasibility of intensifying dual purpose goat production within mixed crop-livestock systems is under study. Solutions to severe dry season feed limitations are being evaluated. Sweet potato vines and legumes such as pigeon peas have been demonstrated to be excellent in nutritional value, with high intakes by lactating does. Intercropped or ratooned sorghum also has promise. Northeast Brazil is representative of the semiarid tropics with a short, variable rainy season and prolonged dry season during which all production parameters for goats and hair sheep are unsatisfactory. The native “caatinga” brushland is the major feed resource. Dry season confinement of lambs has resulted in adequate growth (90 g/day or more) when fed maized crop residue plus supplements. Weanling kids fed the same ration have lower intake and gains of 20 to 40 g/day. Sorghum hay has been fed to lactating dairy goats. The fourth site, Morocco, has a Mediterranean climate with good rainfall in spring, prolonged drought in summer and fall, and cold limitation in winter (especially at higher elevations). Wheat stubble and other crop residues are under study for their nutritional contribution and supplementation requirements in summer, fall and winter. Also, studies are underway on productivity responses of native sheep in extensive or semi-intensive systems, as well as the prolific D'man breed in total confinement. The fifth site is Peru, where Andean highland areas are limited by cold year-round and extended drought for part of the year. Grazing systems for sheep and alpacas are under study at three Andean locations. At a coastal site, which receives sporadic rain (1 to 3 months, not every year), improved feeding systems for seminomadic herds of dual purpose goats are under study.

Mammary Gland Growth and the Initiation of Lactation in Dairy Goats

Summary The efficacy of estradiol, oxytocin, and bovine somatotrophin to initiate lactation in goats with artificially induced mammary gland growth was tested. In a second experiment, the amount of mammary gland growth resulting from the oral administration of diethylstilbestrol (DES) and 6-methyl-17 acetoprogesterone (MAP) was determined. In the first experiment, the milk production of goats previously treated for 120 days with estradiol and progesterone was not increased by the injections of either estradiol, oxytocin, or bovine somatotrophin. In the second experiment, no marked milk secretion occurred in goats fed DES or MAP for 150 days until a dose of 1.0 mg estradiol had been injected daily for a 7-day period. The oral administration of DES or MAP alone, or a combination of the two, resulted in some mammary gland growth and milk production, but the production was much lower than that resulting from pregnancy. The combination of both compounds was no more effective than either one alone. The feeding of MAP to goats for the last 60 days of pregnancy resulted in higher levels of milk production for the first 4 wk of lactation, but the difference was not statistically significant (P > 0.10). Thereafter, the milk production was approximately equal in the treated and the normal pregnant groups. The correlation between previous milk production and total alveolar surface area was 0.935.