PROJECT HIGHLIGHTS

Title: Betaine and Choline Supplementation to Enhance Mohair Production

Objectives:

Measure responses to an increased dietary supply of betaine and choline in Angora goats on fiber growth rate, composition, and quality

Measure responses to an increased supply of betaine and choline in dairy goats on milk production and composition

Recent Highlights:

Effects of dietary supplementation with ruminally protected choline (RPC) on growth performance of Alpine doelings was investigated. Thirty-six Alpine doelings (17 wk of age, 17 ± 1.2 kg BW) consumed ad libitum a completely mixed diet (18% CP, 74% TDN) containing RPC at 0, 8, or 16 g/kg dry matter for 90 d. Average feed consumption (1.15 kg/d) was similar among groups. Average daily gain tended to increase as a result of supplementation (162, 166, and 172 g/d for 0, 8, and 16 g/kg of RPC, respectively). Feed efficiency (feed/gain) was also linearly improved in RPC groups (7.24, 7.04, and 6.84 for 0, 8, and 16 g of RPC, respectively). Supplementation linearly increased plasma choline concentration (2.96, 4.05, and 4.94 µM for 0, 8, and 16 g/kg of RPC, respectively). In conclusion, observed improvements in average daily gain and feed efficiency with dietary choline inclusion suggest that choline may be limiting in diets for growing Alpine doelings. These findings are important to animal scientists, extensionists, and goat producers, in that they may lead to simple and safe means of naturally enhancing efficiency of goat production for improved profitability and sustainability.

Title: Seasonal Manipulations to Improve Cashmere and Meat Returns in Goats

Objectives:

Quantify the natural seasonal cycle of cashmere growth. This is essential to permit the extension of existing technology from other countries to the U.S. Practical recommendations on harvest dates for cashmere will be provided and the window of opportunity for chemical defleecing treatments will be defined.

To quantify the response in fiber growth and breeding cycles of two methods of melatonin treatment applied in April in the U.S. This represents an attempt to improve both meat and cashmere returns from U.S. goats following a single spring melatonin treatment.

To determine whether shedding, following the cessation of a spring melatonin treatment, can be prevented by the suppression of plasma prolactin concentration. This objective seeks to greatly enhance the magnitude of cashmere response to melatonin treatment, without compromising meat production.

To determine the effect of chemical defleecing agents on fiber growth and quality in cashmere goats. This technology seeks to harvest cashmere with minimal guard hair contamination while retaining the guard hair fleece on the goat for protection from cold.

Recent Highlights:

An experiment was conducted to determine if mimosine treatment of goats at the winter solstice induces shedding of cashmere but not guard hair. Twelve adult cashmere wethers (45 ± 2 kg) were infused for a 72-h period on December 9, 16, or 23, 1996 (four goats per day), with mimosine (100 mg/kg body weight) or saline (C). Primary and secondary follicle activities (FA) on d 0 were 33 ± 8 and 78 ± 7%, respectively. On d 8, cashmere had been shed in three of the six mimosine-treated goats; thus, fiber data were collected from three goats infused with mimosine (M) and from six C goats. Day-8 secondary FA was lower (0 vs 69%) and cashmere shedding score (SS; 1 and 5 = no and excessive shedding, respectively) was greater (5.0 vs 1.1) for M than for C. On d 14, cashmere length was shorter (3.0 vs 8.6 cm) and guard hair SS was greater (2.3 vs 1.0 cm) for M compared with C goats. Cashmere yield from M goats was 34 ± 3, 85 ± 4, and 3 ± 1% for pre-combed, combed, and post-combed fleeces, respectively. In January and February, secondary FA (> 98 vs 37 to 52%) and cashmere growth rate ((i.e., based on length of nonshed fiber) 1.10 vs -.22 mm/d) were greater for M vs C goats. In conclusion, M was effective at removing cashmere in 50% of the goats treated; secondary FA in cashmere-shedding goats was increased by M, which led to additional cashmere growth. These findings have immense importance to extensionists and goat producers around the world, in that they may lead to a simple, inexpensive means of harvesting cashmere from goats without shearing and with little guard hair contamination.

Title: Exogenous Hormone and Nutritional Manipulation to Increase Fiber Production

Objectives:

Investigate the interactions among growth hormone, insulin-like growth factor I, insulin, and thyroid hormones for mohair growth and skin metabolism

Define the role of growth hormone on skin metabolism and mohair growth and determine whether growth hormone has the potential to improve mohair production and quality

Recent Highlights:

Fourteen Angora kids (age = 5 mo; BW = 19.4 kg) were used to study effects of exogenous bovine somatotropin (bST) on hormonal, metabolic status, and productivity of animals. The experiment consisted of a 4-wk pretreatment period, 5 wk of daily subcutaneous administration of bST at two levels (0 and 100 g/kg BW/d; Period 1), and a 7-wk post-treatment (Period 2). Kids were given ad libitum access to a diet with 16% CP and 2.34 Mcal/kg of metabolizable energy. Plasma triiodothyronine (T₃), thyroxine (T₄), and cortisol concentrations were not affected by treatment, although plasma insulin was increased by bST. During Period 1, bST improved rate of BW gain by 65% (151 vs 92 g/d) and feed conversion ratio (5.4 vs 7.8 g feed/g gain). After cessation of bST injection, treatment differences disappeared. Dry matter intake and mohair production were not altered by bST. Plasma threonine and phenylalanine concentrations decreased during bST treatment. At the end of Period 1, plasma concentration of somatotropin was 6-fold greater (18.3 vs 2.9 ng/mL), insulin-like growth factor I (IGF-I) was 3-fold greater (1,006 vs 320 ng/mL), and plasma urea nitrogen concentration was lower (14.9 vs 18.3 mg/dL) for goats injected with bST. Interactions among bST, IGF-I, and insulin may impact BW gain and feed conversion ratio. This research will be of importance to animal scientists in determining nutritional and physiological factors influencing growth and fiber production by goats to increase profitability for livestock producers.

Title: The Evaluation of Various Feedstuffs for Milk Production in Early Lactating Goats

Objectives:

Study interactions between levels of ruminally undegradable protein and digestible energy in lactating goat diets

• Evaluate potential use of cotton byproducts in dairy goat diets
• Determine influences on milk fever in dairy goats of dietary concentrations and ratios of acidogenic and alkalinogenic minerals

Recent Highlights:

An experiment was recently conducted to investigate effects of whole cottonseed on production by lactating dairy goats. Seventy Alpine does were used, being fed diets with 0, 4, 8, 12, or 16% whole cottonseed for a 115-d period. Currently, feed and ruminal fluid samples are being subjected to laboratory analyses, and feed intake, milk production, and milk composition data are being analyzed statistically. Though not complete, results of this project will be of value to animal scientists and extensionists and livestock producers in determining practical feeding guidelines for a regional available byproduct, to achieve highest possible performance with lowest production costs for greatest profit.

Title: Factors Affecting the Quality and Quantity of Fiber Growth in Goats

Objectives:

Determine influences of amino acids and hormones on metabolism of skin in Angora goats

Improve the understanding of regulation of mohair production, to facilitate future improvements in fiber production by goats

Recent Highlights:

Results of one experiment suggest that insulin regulates skin methionine metabolism via local effects, whereas triiodothyronine influences amino acid metabolism via centrally regulated mechanisms. In Angora goats, skin demand for methionine may be higher than provided by average blood methionine concentration. Results of another experiment suggest that whole body branched-chain amino acid and glucose concentrations in Angora goats are highly responsive to doubling of physiological concentration of triiodothyronine, but apparently unresponsive to acute (60 min) pharmacological increments in plasma cortisol concentration. These findings are of value to animal scientists in increasing knowledge of skin metabolism for future diet formulation to optimize mohair production, providing the basis for genetic selection of animals for mohair production, and development of products to regulate nutrient uptake in the skin. Ultimately, such research will benefit livestock producers, in leading to development of technologies to increase profitability of goat fiber production.

Title: Nutritional Management of Breeds and Genders for Efficient Goat Meat Production

Objective:

Determine effects of gender, breed, and dietary level of concentrate or energy intake on protein and fat deposition and meat quality in growing goats

Recent Highlights:

Spanish x Boer kids (intact males, castrates, and females) were used to investigate effects of gender and age on growth performance. Kids started the experiment at an average BW of 16.4 kg and age of 93 d and consumed a corn-based diet during the study. Performance results at 21, 29, 36, and 45 wk of age are as follows. Dry matter intake (519, 550, 717, and 727 g/d) increased linearly with age. Average daily gain (ADG; 113, 98, 139, and 126 g/d) and feed to gain (F/G)(4.77, 6.32, 5.22, and 5.88) responded to age in a cubic fashion. Intact males and castrates had greater DMI than females (675 vs 533 g/d); males had the greatest ADG and were the most efficient (ADG: 143, 121, and 93 g/d; F/G: 4.80, 5.93, and 5.91 for males, castrates, and females, respectively). No significant gender x age interaction was observed for DMI (g/d), BW, ADG, or F/G. Loin eye area increased linearly with age (7.29, 10.19, 11.10, 13.55, and 13.74 cm²). Internal fat increased quadratically with age (0.32, 1.08, 1.60, 2.77, and 4.08 kg). Internal fat comprised 6.9, 7.0, and 5.1% of empty BW for castrates, females and males, respectively. In conclusion, these results reflect performance advantages for intact male meat goats; changes in internal fat deposition with advancing age may impact increases in lean tissue accretion by Boer crossbreds. These findings will be of great importance to meat goat producers and animal extensionists and scientists in promoting use of management strategies to achieve most efficient and profitable production.

Title: Environmental and Physiological Control of the Growth and Properties of Mohair

Objective:

Investigate effects of and interactions between environmental and physiological controls of mohair growth and quality

Recent Highlights:

An experiment was conducted to describe the seasonal fleece growth cycle in U.S. goats with ambient climatic conditions, and to determine effects of level of feed intake on the cycle. From September 13, 1995 to October 9, 1996, 20 mature, nonpregnant Angora does (30.2 ± .9 kg; 2.45 ± .09 kg 6-mo fleece weight) were maintained in .4-ha paddocks with low available forage mass. In addition, a diet was offered at .53 (Low) or .68 kg/d of dry matter (High) to maintain or slowly increase body weight, respectively. Minimum follicle activity (FA) occurred 1 mo after the winter solstice and averaged 8 ± 3 and 78 ± 4% in primary and secondary follicles, respectively. Fleece growth rate, fiber diameter, and fleece medullation were 40, 15, and 120% lower, respectively, in the winter than summer. Fleece growth rate and fiber diameter were maximal 1 mo before the autumn equinox. The High goats had a 20% greater shorn fleece weight than did Low goats. Overall, High and Low goats had similar clean fiber regrowth rates, yield, and diameter. Spring primary FA was lower for Low compared with High goats, but secondary FA, follicle medullation, and fleece kemp level were unaffected by level of feed intake. In conclusion, U.S. Angora goats, with constant levels of feed intake, exhibit seasonal follicle and fiber growth cycles, which may impact efficiency of feed use for mohair growth throughout the year. Level of feed intake can affect fleece weight and seasonal changes in primary FA. This research is of great value to animal scientists and extensionists and goat producers, in that it will facilitate the formulation of management plans that can be implemented on the farm to increase income from goat fiber production.

Title: Protein Supplementation to Enhance Mohair Production

Objective:

Determine physiological factors influenced by protein supplementation that enhance mohair growth and(or) quality

Recent Highlights:

Ruminal and plasma amino acid responses to providing supplemental DL-methionine (Met) in either drinking water or feed was studied in adult (45 kg) wethers. Goats received 1) the basal diet (40% forage and 14% crude protein) containing .15% sulfur, 2) the basal diet plus 2.5 g of Met daily in drinking water for approximately .18% dietary sulfur, or 3) the basal diet plus 2.5 g of Met daily top-dressed on feed (.18% dietary sulfur). Methionine supplemented in water or feed increased plasma concentrations of glutamate, arginine, Met, and of Met as a percentage of essential and total amino acids (AA). Plasma Met concentration was higher when top-dressed; Val, Met, and Met levels as a % of essential and total amino acids were increased by Met supplementation. Phenylalanine was higher when Met was placed in drinking water. Concentrations of serine, threonine, alanine, tyrosine, valine, leucine, total AA, essential AA, and nonessential AA exhibited quadratic responses over time post-feeding, peaking at 1 h. Only Met as a % of total AA was increased linearly by Met supplementation. Ruminal ammonia decreased when Met was added to the diet. Volatile fatty acid ratios, protozoal numbers, and pH were not altered by added Met. In summary, Met supplementation in water or feed increased plasma Met. Responses to Met in water need to be tested with goats fed a higher dietary sulfur level to determine if equal responses can be attributed to organic and inorganic dietary sulfur. These results are of importance to animal scientists in facilitating further research with different forms of dietary sulfur, which may lead to more profitable mohair growth for goat producers.

Title: Enhancing Browse Utilization by Goats

Objectives:

Investigate the chemical composition and potential nutritive value of browse with emphasis on the tannin content, type, and limitation to digestion

Explore relationships among supplemental polyethylene glycol, tannin content in forage, and forage utilization by ruminants in order to increase intake of tannin-containing forages

Determine if once-daily supplementation with polyethylene glycol will enhance goat control of noxious brush and weeds

Recent Highlights:

One of the primary studies of this project will begin in the spring of 1998. A preliminary, pilot experiment was conducted in the fall of 1997. In this experiment, Alpine wethers were fed leaves of two brush species, Water Oak and Shining Sumac. Feed intake was measured and samples of feed, feces, and urine are currently being subjected to laboratory analyses to determine nutrient digestibilities and nitrogen and energy balances. Though this project is in its infancy, expected results hold promise to markedly enhance the ability of goats to thrive while consuming high-tannin herbage, thereby improving utilization of normally low-value plants and increasing the brush-clearing ability of goats for elevated land productivity and agricultural system sustainability.