Digestibility of untreated and hydroxide-treated annual ryegrass straw.

Digestion trials with sheep were carried out with untreated and NaOH-treated cubed annual ryegrass straw. In the first trial, NaOH treatment increased (P < .05) digestibility of all organic components. Organic matter digestibility was increased by 21% and energy by 32%. In the second trial, the untreated straw (different crop year) was more digestible than in the first trial (digestible energy was 47%, vs 43% in the first year). In both cases, digestibility of the straw was estimated by difference when it was fed with alfalfa hay and compared to alfalfa hay alone. When the straw was fed with urea and molasses and digestibility was estimated with book values for molasses, digestion coefficients for organic matter and acid detergent fiber were slightly higher and energy was slightly lower than when digestibility was determined by difference, but the values were not different (P > .05). NaOH treatment did not result in as much improvement in the second trial as in the first trial, but it did result in increased digestibility or organic matter and fiber; crude protein digestibility however, was lower (P < .05) with NaOH-treated than with untreated straw. TDN estimated from digestible energy appeared to give more appropriate values for straw (39.7, 41.3) and NaOH-treated straw (44.4, 46.3) relative to alfalfa hay (53.4) than those calculated by the standard method (48.2 and 50.8 for straw; 52.0 and 55.0 for NaOH-treated straw).

Digestibility of dried bakery product by sheep.

The digestibility of a commercial dried bakery product was determined with sheep. The product was fed at 20 or 40% of the diet; the rest of the diet was composed of alfalfa hay, dried beet pulp and rolled barley. Digestibility of all constituents increased (P < 05) when either 20 or 40% dried bakery product was fed. Calculated coefficients (computed by difference) for the dried bakery product indicated a slight decrease in digestibility of crude protein, digestible energy and total dietary nitrogen when the product was fed at the 40% level. Digestible energy was calculated at 4.08 and 3.89 Mcal/kg for the dried bakery product when fed at 20 and 40% of the diet, respectively. These values agree closely with suggested literature values derived from digestion trials with poultry.

Relationships between eating rate of sheep and live weight gain, weight and fill of the gastrointestinal tract.

Nine ewe and eight wether weanling lambs were fed a pelleted diet containing 60% roughage and 40% concentrate for 12 h/day. Feed consumption (FC) was measured during the first 30 and 60 min (FC-30, -60). Total daily consumption (FCT) was also measured. With these data, feed efficiency (FE), eating rate index (ERI = FC/BW.75) and propensity to eat (percentage FC/unit of time) were calculated. After the completion of these studies, the lambs were slaughtered and weights of the full gastrointestinal tract (GIT) organs, empty organs and wet digesta were obtained. Dry digesta in the organs were estimated from samples of oven-dried digesta. Respective values for males and females were: FE, 6.36 and 7.50 (P less than .01); average daily gain (ADG), 285 and 230 g (P less than .02); FC-30, 597 and 488 g (P less than .05), and FC-60, 706 and 583 g (P less than .05). Significant correlations were found only for females for FC-30 with FCT, ADG with FE and FC-60 with FE (P less than .05). Significant correlations of ERI-30 and ERI-60 with ADG and FE were also observed for the combined sex data. Correlations between eating rate terms and organ or digesta weights were significant only for some reticulorumen (RR) and abomasal parameters. When data from the GIT were correlated with animal performance (FC, ADG, FE), the highest correlations observed were generally for females. Correlations with organ or digesta weights tended to be highest for the small intestine (SI) and ADG; these were followed by values of about equal magnitude for RR organ or digesta weights and ADG or FE. The highest correlations were those between ADG and full organ weight of the SI for males (.86, P less than .01) and between ADG and wet digesta weights of the SI for females (.86, P less than .01). It is concluded that organ and (or) digesta weights of the SI are highly related to animal performance and may be as important as the RR in affecting voluntary feed consumption of pelleted diets.

Evaluation of single cell protein from pulp mills: laboratory analyses and in vivo digestibility.

Single cell protein (SCP) derived from secondary clarifiers of pulp mills is a potential commercial protein supplement in many areas. Samples of SCP were collected from several pulp mills in the Pacific Northwest and evaluated by laboratory procedures. Six in vivo digestion trials were conducted to determine the relative nutritive value of SCP that was dewatered by centrifugation or by the addition of a polyacrylamide polymer before being put through a belt press and dried with a sonic dehydrator. Amino acid analyses showed that SCP was higher in methionine than was cottonseed meal (CSM) and had a similar level of lysine. True protein, based upon amino acids recovered in SCP samples, ranged from 51.6 to 65.9% of the crude protein (CP). Pepsin digestibility of the CP ranged from 16.2 to 36.8%. Pepsin digestibility increased by 6.3 to 11.3 percentage units when SCP were incubated in a buffered rumen fluid for 24 hours. Solubility of the nitrogenous components in 10% Burroughs' buffer solution ranged from 12.4 to 36.5%. The range in mineral composition was : P, .62 to 1.55%; Ca, .14 to .99%; K, .21 to 5.52%; Mg, .07 to .59%. The concentration of trace minerals and heavy metals varied considerably from sample to sample. Digestion trials were conducted with sheep to compare SCP with CSM; 20 to 50% of the total CP was provided by the SCP sources. The CP digestibilities of the centrifuged and the polymer-dewatered SCP were 70.5 to 70.8% and 66.3 to 69.9%, respectively, of that observed for CSM. In all digestion trials, sheep consumed the SCP diets readily, and no digestive disturbances were observed. On the basis of laboratory and in vivo results, pulp mill SCP has the potential to be a viable protein supplement for livestock.